1790 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
Chapter 10 D.5 RPS Oil Spill Modelling Report
BROWSE TO NWS PROJECT - QUANTITATIVE SPILL RISK ASSESSMENT
Report
MAW0815J Browse to NWS Project - Quantitative Spill Risk Assessment Rev 4 27 November 2019 udi es
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ofservices. This report is supplied for the sole and specific purpose for use by RPS’ client. The reportdoes This reportwas prepared by RPS within the terms of RPS’ engagementwith its clientand in directresponse to a REPORT www.rpsgroup.com/mst MAW0815J w th since for any changes relating the subject matterthe of report, or any legislative or regulatory changes thathave occurred David Wri David issue for Approval Rev Rev 3 Rev 2 Rev 1 Rev 0 Rev A Version status Document
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ght Browse to NWS Project NWS to Browse Client review Client review Client review Client review Client review Internal review Internal document of Purpose -31 Troode Street
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Quantitative Spill Risk Assessment Risk Spill Quantitative
N J. Wynen J. Wynen Watt M. B. G J. Wynen Watt M. B. G J. Wynen Authored by
J. Wynen Watt M. B. G .
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| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
T Woodside Energy Ltd Energy Woodside Perth Yellagonga,MiaMount 11 Street Prepared for
D R. Alexander R. Alexander D. Wright by Reviewed R. Alexande D. Wright |
+61 8 +61 8 9348 4000 . WA 6000 WA 27 November 2019 November 27
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D. Wright Appr D. Wright D. Wright D. Wright D. Wright D. 27 November 2019
Wright oved by
0 date Review 25/07/2019 2 05/11/2019 2 01/0 not account 4 7 9 /0 /11/2019 /08/2019 7 7 scope /2019 /2019 Page
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Contents Executive Summary ...... 13 Metocean Influences ...... 13 Oil Characteristics ...... 13 Summary of Stochastic Assessment Results ...... 14 Interpretation of Contour Figures ...... 14 Scenario 1: Long-Term (77-Day) Surface/Subsea Blowout of Unstabilised Torosa Condensate at the TRA-C Well ...... 14 Scenario 2: Short-Term (24-Hour) Surface Release of Stabilised Torosa Condensate after a Vessel Cargo Tank Rupture at the Torosa FPSO Location ...... 15 Scenario 3: Short-Term (Instantaneous) Surface Release of Stabilised Torosa Condensate after an FPSO Offtake System Failure at the Torosa FPSO Location ...... 16 Scenario 4: Short-Term (Instantaneous) Surface Release of Marine Diesel after a Vessel Fuel Tank Rupture near the Rowley Shoals ...... 16 1 INTRODUCTION ...... 1 1.1 Background ...... 1 1.2 Stochastic Modelling of Spill Scenarios ...... 3 1.3 Deterministic Analysis ...... 4 1.4 Report Structure ...... 4 2 MODELLING METHODOLOGY ...... 5 2.1 Description of the Models ...... 5 2.1.1 SIMAP ...... 5 2.1.2 OILMAP ...... 6 2.2 Calculation of Exposure Risks ...... 7 2.3 Inputs to the Risk Assessment ...... 8 2.3.1 Current Data ...... 8 2.3.2 Wind Data ...... 29 2.3.3 Water Temperature and Salinity Data ...... 32 2.3.4 Dispersion ...... 32 2.3.5 Replication ...... 32 2.3.6 Contact Thresholds ...... 34 2.3.7 Oil Characteristics ...... 35 2.3.8 Weathering Characteristics ...... 38 2.3.9 Emulsification Characteristics ...... 49 2.3.10 Subsea Discharge Characteristics...... 50 3 STOCHASTIC ASSESSMENT RESULTS ...... 53 3.1 Overview ...... 53 3.2 Scenario 1: Long-Term (77-Day) Surface/Subsea Blowout of Unstabilised Torosa Condensate at the TRA-C Well ...... 56 3.2.1 Discussion of Results ...... 56 3.2.2 Results Tables and Figures ...... 58 3.3 Scenario 2: Short-Term (24-Hour) Surface Release of Stabilised Torosa Condensate after a Vessel Cargo Tank Rupture at the Torosa FPSO Location ...... 79 3.3.1 Discussion of Results ...... 79 3.3.2 Results Tables and Figures ...... 81 3.4 Scenario 3: Short-Term (Instantaneous) Surface Release of Stabilised Torosa Condensate after an FPSO Offtake System Failure at the Torosa FPSO Location ...... 102 3.4.1 Discussion of Results ...... 102 3.4.2 Results Tables and Figures ...... 104
Scenario 4: Short-Term (Instantaneous) Surface Release of Marine Diesel after a Vessel 3.5 Fuel Tank Rupture near the Rowley Shoals ...... 125 udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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4.3 4.2 4.1 ASSESS DETERMINISTIC REFERENCES Results Assessment Stochastic of Summary Oil Characteristics Influences Metocean CONCLUSIONS 4.5 4.4
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Browse to NWS Project NWS to Browse after a Vessel Cargo Tank Rupture at the Torosa FPSO Location FPSO Torosa at the Rupture Tank Cargo aVessel after TRA at the Condensate Location FPSO Torosa at the Rupture Tank Cargo aVessel after TRA at the Condensate Fuel Tank Rupture near the Rowley Shoals Rowley near the Rupture Fuel Tank Short 4: Scenario Location FPSO Torosa the at Failure System Offtake an FPSO after Condensate Short 3: Scenario Short 2: Scenario Long 1: Scenario Figures Contour of Interpretation 4.5.1 Shoals Rowley near the Rupture Fuel Tank Short 4: Scenario 4.4.1 Location FPSO Torosa the at Failure System Offtake an FPSO after Condensate Short 3: Scenario 4.3.4 4.3.3 4.3.2 4.3.1 Short 2: Scenario 4.2.2 4.2.1 Long 1: Scenario Overview 3.5.2 3.5.1
Results Tables and Figures and Tables Results Results of Discussion at Any Individual Shoreline Receptor at Defined Threshold at Defined Receptor Shoreline Individual at Any and Receptors Shoreline All across Accumulation Oil Maximum with Simulation Threshold at Defined Receptor Shoreline Individual at Any and Receptors Shoreline All across Accumulation Oil Maximum with Simulation Threshold at Defined Receptor Shoreline Individual at Any All Re Shoreline across Oil Accumulation with Simulation Maximum Defined Threshold to Oil Time Minimum with Simulation Threshold atDefined Receptor Shoreline Minimum with Simulation Threshold at Defined Receptor Shoreline at Any to Floating Contact Oil Time Minimum with Simulation Threshold at Defined Receptor Shoreline Individual at Any and Receptors Shoreline All across Accumulation Oil Maximum with Simulation Thresholds at Defined Receptor Shoreline at Any Accumulation to and Oil Contact Time Minimum with Simulation
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Quant ------Term (7 Term (77 Term Term (Instantaneous) Surface Release of Marine Diesel after a Vessel a after Diesel Marine of Release Surface (Instantaneous) Term (Instantane Term (24 Term Vessel a after Diesel Marine of Release Surface (Instantaneous) Term Torosa Stabilised of Release Surface (Instantaneous) Term (24 Term
itative Spill Risk Assessment Risk Spill itative MENT RESULTS MENT - - C Well C Well 7
- - - - ...... Day) Surface/Subsea Blowout of Unstabilised Torosa Torosa Unstabilised of Blowout Day) Surface/Subsea Torosa Unstabilised of Blowout Day) Surface/Subsea Hour) Surface Release Surface Hour) Condensate Torosa Stabilised of Release Surface Hour) ......
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...... Time to Entrained/Dissolved Oil Contact at Any at Oil Contact to Entrained/Dissolved Time ...... ous) Surface Release of Stabilised Torosa Torosa Stabilised of Release Surface ous)
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of Stabilised Torosa Condensate Condensate Torosa Stabilised of ......
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...... 157 ...... 157 ...... 157 ceptors and and ceptors ...... 127 ...... 157 ...... 148 ...... 149
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Tables Table 1.1 Summary of the hydrocarbon spill scenarios assessed in a stochastic manner in this study...... 4 Table 2.1 Statistical comparison of BRAN-predicted and measured non-tidal current speeds along orthogonal component axes at the three measurement sites (2006-2007)...... 15 Table 2.2 Summary of the thresholds applied in this study...... 34 Table 2.3 Characteristics of the oil types used in the modelling of Scenarios 1-4...... 36 Table 2.4 Near-field subsea discharge model parameters for Scenario 1...... 52 Table 3.1 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well...... 58 Table 3.2 Expected annualised entrained oil outcomes at sensitive receptors resulting from a 77- day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well...... 67 Table 3.3 Expected annualised dissolved aromatic hydrocarbon outcomes at sensitive receptors resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well...... 73 Table 3.4 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 81 Table 3.5 Expected annualised entrained oil outcomes at sensitive receptors resulting from a 24- hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 90 Table 3.6 Expected annualised dissolved aromatic hydrocarbon outcomes at sensitive receptors resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 96 Table 3.7 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location...... 104 Table 3.8 Expected annualised entrained oil outcomes at sensitive receptors resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location...... 113 Table 3.9 Expected annualised dissolved aromatic hydrocarbon outcomes at sensitive receptors resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location...... 119 Table 3.10 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 127 Table 3.11 Expected annualised entrained oil outcomes at sensitive receptors resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 136 Table 3.12 Expected annualised dissolved aromatic hydrocarbon outcomes at sensitive receptors resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 142
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Figure 2.10 Figure 2.9 Figure 2.8 Figure 2.7 Figure 2.6 Figure 2.5 Figure 2.4 Figure 2.3 Figure Figure 2.1 Figure 1.1 Figures REPORT www.rpsgroup.com/mst MAW0815J Figure 2.16 Figure 2.15 Figure 2.14 Figure 2.13 Figure 2.12 Figure 2.11 2.2
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for the period of August 2006 to July 2007. July to 2006 August of the period for f 97 17 for the period of August 2006 to July 2007. July to 2006 August of the period for measured (blue line) non (blue measured measured (blue line) non (blue measured line) non (blue measured line) non (blue measured line) non (blue measured line) non (blue measured 220 line indicates a 1:1 correlation between the modelled and observed data. observed and modelled the between 1:1 correlation a line indicates Th domain. model HYDROMAP thein (>80) at stations all relevant (bottom) phases and (top) amplitudes tidal constituent observed and modelled between Comparisons north the in locations at five variations elevation line) surface (red observed line) and (blue predicted the between Comparisons north the in locations at five variations thebetween pred Comparisons zones. mesh denser the by indicated are areas resolution Higher dots). labelled blue and (red tidal comparisons for available locations the showing the for wire mesh) (blue grid model hydrodynamic the of subset Zoomed zones. mesh the denser Higher dots). labelled blue and (red tidal comparisons wit in context domain the full showing currents, tidal the to used generate wire mesh) (blue grid model Hydrodynamic the record of percentage the gives wedge the of size the and flowing, is current the which direction towards the provides direction compass the magnitude, current the shows key colour The location. 4 spill Scenario to the (2006 distribution current Monthly the record. of percentage the gives wedge the of size is flowin current which the towards direction the provides direction the compass magnitude, current the key shows colour The locations. spill 3 2 and 1, Scenario to the (2006 distribution current Monthly BRAN between Comparisons BRAN between Comparisons BRAN between Comparisons BRAN between Comparisons BRAN between Comparisons BRAN between Comparisons Australia. of the Kimberley Coast off Western Reef, Scott to proximity in validation, model curre the FPSO and Torosa proposed the of Locations sites. release scenario spill hydrocarbon modelled the of Locations Monthly current distribution (2006 distribution current Monthly perce the gives wedge the of size the and flowing, is current which the towards direction the directionprovides compass the magnitude, current the key shows colour The location. spill 1 Scenario the to near database (2006 distribution current Monthly flowing, and the size of the wedge gives wedge the of size the and flowing, is current which the towards direction the directionprovides compass the magnitude, current the shows colour key The locations. 3 spill and 2 Scenario the to near database or the period of August 2006 to July 2007. July to 2006 August of or the period m, for the period of August 2006 to July 2007. July to 2006 August the of period for m, 2007. July to 2006 August the of period for m, m, for the period of August 2006 to July 2007. July to 2006 August of the period for m,
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Quantitative Spill Risk Assessment Risk Spill Quantitative
...... ------tidal current data at site C1 at site data tidalcurrent tidal current data at site G2 at site data tidalcurrent G2 at site data tidalcurrent C1 at site data tidalcurrent B2 at site data tidalcurrent B2 at site data tidalcurrent h the continental land mass and the locations available for for available locations and the land mass continental h the ------predicted (red line), HYCOM line), (red predicted HYCOM line), (red predicted HYCOM line), (red predicted HYCOM line), (red predicted HYCOM line), (red predicted HYCOM line), (red predicted icted (blue line) and observed (red line) surface elevation elevation line) surface (red observed line) and (blue icted - - - - 2015, inclusive) d inclusive) 2015, near the database BRAN from derived inclusive) 2015, 2015, inclusive) derived from the HYDROMAP the HYDROMAP from derived inclusive) 2015, 201 - - 5, inclusive) derived from the HYDROMAP the HYDROMAP from derived inclusive) 5, east of the tidal model domain for January 2018. January for domain model tidal the of east 2018. January for domain model tidal the of east
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...... ntage of the record. of ntage
...... erived from the BRAN database near the database BRAN from erived . ------
1, at a depth of app of a depth 1, at 20 approximately of a depth 1, at 1, at a depth of approximately 80 approximately of a depth 1, at 1, at a depth of approximately 20 approximately of a depth 1, at - ...... 1, at a depth of approximately approximately of a depth 1, at approximately of a depth 1, at resolution areas are indicated by by indicated are areas resolution nt measurement sites used for for sitesused nt measurement
...... ------predicted (green line) and line) (green predicted and line) (green predicted line) (green predicted and line) (green predicted and line) (green predicted and line) (green predicted
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Scott Reef area, Scott Reef roximately roximately ...... 16 ...... 17 ...... 21 g, and the g,
and ...... 13 ...... 13 ...... 12 e red ...... 20
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Figure 2.17 Monthly current distribution (2006-2015, inclusive) derived from the HYDROMAP database near to the Scenario 4 spill location. The colour key shows the current magnitude, the compass direction provides the direction towards which the current is flowing, and the size of the wedge gives the percentage of the record...... 28 Figure 2.18 Monthly wind distribution (2006-2015, inclusive) derived from the CFSR database near to the Scenario 1, 2 and 3 spill locations. The colour key shows the wind magnitude, the compass direction provides the direction from which the wind is blowing, and the size of the wedge gives the percentage of the record...... 30 Figure 2.19 Monthly wind distribution (2006-2015, inclusive) derived from the CFSR database near to the Scenario 4 spill location. The colour key shows the wind magnitude, the compass direction provides the direction from which the wind is blowing, and the size of the wedge gives the percentage of the record...... 31 Figure 2.20 Temperature (blue line) and salinity (green line) profiles derived from the WOA13 database near the Torosa FPSO location (13° 52' 30" S, 121° 52' 30" E). Depth of 0 m is the water surface...... 33 Figure 2.21 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of unstabilised Torosa Condensate (surface) spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to a constant 5 kn (2.6 m/s) wind at 27 °C water temperature and 25 °C air temperature...... 41 Figure 2.22 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of unstabilised Torosa Condensate (surface) spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature...... 42 Figure 2.23 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of unstabilised Torosa Condensate (subsea) spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to a constant 5 kn (2.6 m/s) wind at 27 °C water temperature and 25 °C air temperature...... 43 Figure 2.24 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of unstabilised Torosa Condensate (subsea) spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature...... 44 Figure 2.25 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of stabilised Torosa Condensate spilled onto the water surface as a one- off release (50 m3 over 1 hour) and subject to a constant 5 kn (2.6 m/s) wind at 27 °C water temperature and 25 °C air temperature...... 45 Figure 2.26 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of stabilised Torosa Condensate spilled onto the water surface as a one- off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature...... 46 Figure 2.27 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of marine diesel spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to a constant 5 kn (2.6 m/s) wind at 27 °C water temperature and 25 °C air temperature...... 47 Figure 2.28 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of marine diesel spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature...... 48 Figure 2.29 Average properties of emulsion stability groups (Fingas & Fieldhouse, 2004)...... 49 Figure 2.30 Theoretical equilibrium lines for hydrate formation based on the temperature and pressure at the release point. The line for “natural gas” assumes 80% methane, 10% ethane and 10% propane. Typical indicative sea temperature profiles with depth are
indicated (Johansen, 2003)...... 51 udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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Figure 3.11 Figure 3.10 Figure 3.9 Figure 3.8 Figure 3.7 Figure 3.6 Figure 3.5 Figure 3.4 Figure 3.3 Figure 3.2 Figure 3.1 REPORT www.rpsgroup.com/mst MAW0815J Figure 3.17 Figure 3.16 Figure 3.15 Figure 3.14 Figure 3.13 Figure 3.12
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Condensate at the TRA at the Condensate TRA well. Condensate at the TRA at the Condensate TRA at the Condensate TRA scenari spill each for wereextracted concentrations hydrocarbon aromatic dissolved entrainedoil and maximum of distributions which the line), along Condensate at the TRA at the Condensate resulting from a 77 resulting from TRA Condensate at the TRA at the Condensate from a 77 from from a 24 from well. rupture at the Torosa FPSO location. FPSO Torosa at the rupture from a 77 from well. resulting from a 77 resulting from from a 77 from well. from a 77 from above 50 or at concentrations hydrocarbon aromatic dissolved of EMBA annualised Predicted TRA the at Condensate Torosa unstabilised 50 above at or concentrations hydrocarbon aromatic dissolved to by contact times minimum annualised Predicted above 50 Pred 3.1. Figure in locations areshown Transect a 77 Cross 100 at or above concentrations oil entrained of EMBA annualised Predicted TRA at the Condensate above 100 or at concentrations oil entrained to by contact times minimum annualised Predicted a 77 resulting from oil concentration entrained of probability annualised Predicted 100 above at or oil concentrations shoreline of probability annualised Predicted 10 or above at oil concentrations floating of EMBA annualised Predicted 1 or above at oil concentrations floating of EMBA annualised Predicted 10 oil concentrati tofloating by contact times minimum annualised Predicted 1 above or at oil concentrations tofloating by contact times minimum annualised Predicted 10 or above at oil concentrations floating of probability annualised Predicted proba annualised Predicted cross of Locations Predicted annualised probability of floating oil concentrations at or above 1 or above at oil concentrations floating of probability annualised Predicted hydrocarb Cross
g/m g/m - -
- -
icted annualised probability of dissolved aromatic hydrocarbon concentrations at or concentrations hydrocarbon aromatic dissolved of probability annualised icted ...... day surfac C well. C C well. C C well. C 2 - -
section transects of predicted annualised maximum entrained oil concentrations for for concentrations entrained oil maximum annualised predicted of section transects section transects of predicted annualised maximum dissolved aromatic dissolved aromatic maximum annualised predicted of section transects 2 resulting from a 77 from resulting
resulting from a 77 resulting from
- - - - - ppb resulting from a 77 from resulting ppb a 77 from resulting ppb on concentrations for a77 for on concentrations day surface/subsea release of unstabilised Torosa Condensate at the TRA at the Condensate Torosa unstabilised of release day surface/subsea hour surface release of stabilised Torosa Condensate after a vessel cargo tank tank cargo vessel a after Condensate Torosa stabilised of release hour surface day surface/subsea release of unstabilised Torosa Condensate at the TRA at the Condensate Torosa unstabilised of release day surface/subsea day surface/subsea release of unstabilised Torosa Condensate at the TRA at the Condensate Torosa unstabilised of release day surface/subsea day surface/subsea release of unstabilised Torosa Condensate at th Condensate Torosa unstabilised of release day surface/subsea
ppb resulting from a 77 from resulting ppb
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Quantitative Spill Risk Assessment Risk Spill Quantitative e/subsea release of unstabilised Torosa Condensate at the TRA the at Condensate Torosa unstabilised of release e/subsea - - - - sections, over a varying latitude (dashed line) and longitude (solid (solid longitude and line) (dashed latitude varying a over sections, day surface/subsea releas day surface/subsea day surface/subsea release of unstabilised Torosa Condensate at the Condensate Torosa unstabilised of release day surface/subsea day surface/subsea release of unstabilised Torosa Condensate at the Condensate Torosa unstabilised of release day surface/subsea ------C well. C well. C well. C well. Transect locations are shown in Figure 3.1. in Figure shown are locations well. Transect C C well. C well...... - day surface/subsea release of unsta of release day surface/subsea - bility of floating oil concentrations at or above 1 or above at oil concentrations floating bility of day surface/subsea release of unstabilised Torosa Torosa unstabilised of release day surface/subsea
ppb resulting from a 77 from resulting ppb ...... - - day surface/subsea release of unstabilised Tor unstabilised of release day surface/subsea Torosa unstabilised of release day surface/subsea - day surface/subsea release of unstabilised Torosa Torosa unstabilised of release day surface/subsea -
day surface/subsea release of unstabilised Torosa Torosa unstabilised of release surface/subsea day ......
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...... - C well. C ...... e of unstabilised Torosa Condensate at the Condensate Torosa unstabilised e of
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...... - day surface/subsea release of of release day surface/subsea ...... s at or above 100 or above at s
bilised Torosa Torosa bilised o in study. this o
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...... 61 ...... 69 ...... 66 g/m ons at or above or at ons
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Figure 3.18 Predicted annualised probability of floating oil concentrations at or above 10 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 84 Figure 3.19 Predicted annualised minimum times to contact by floating oil concentrations at or above 1 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 85 Figure 3.20 Predicted annualised minimum times to contact by floating oil concentrations at or above 10 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 86 Figure 3.21 Predicted annualised EMBA of floating oil concentrations at or above 1 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 87 Figure 3.22 Predicted annualised EMBA of floating oil concentrations at or above 10 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 88 Figure 3.23 Predicted annualised probability of shoreline oil concentrations at or above 100 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 89 Figure 3.24 Predicted annualised probability of entrained oil concentrations at or above 100 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 92 Figure 3.25 Predicted annualised minimum times to contact by entrained oil concentrations at or above 100 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 93 Figure 3.26 Predicted annualised EMBA of entrained oil concentrations at or above 100 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 94 Figure 3.27 Cross-section transects of predicted annualised maximum entrained oil concentrations for a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location. Transect locations are shown in Figure 3.1...... 95 Figure 3.28 Predicted annualised probability of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 98 Figure 3.29 Predicted annualised minimum times to contact by dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 99 Figure 3.30 Predicted annualised EMBA of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location...... 100 Figure 3.31 Cross-section transects of predicted annualised maximum dissolved aromatic hydrocarbon concentrations for a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location. Transect locations are shown in Figure 3.1...... 101 Figure 3.32 Predicted annualised probability of floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location...... 106 Figure 3.33 Predicted annualised probability of floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location...... 107 Figure 3.34 Predicted annualised minimum times to contact by floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate
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Condensate after an FPSO offtake system failure at the Torosa FPSO location. FPSO Torosa the failure at system offtake an FPSO after Condensate Condensate after an FPSO offtake system failure at the Torosa FPSO location. FPSO Torosa the failure at system offtake an FPSO after Condensate tank rupture near the Rowley Shoals. Rowley the rupture near tank rupture near the Rowley Shoals. Rowley near the rupture afte diesel marine of release surface an instantaneous resulting from FPSO offtake system failure at the Torosa FPSO location. FPSO failure Torosa at the system FPSO offtake an after Condensate Torosa stabilised of release surface an instantaneous resulting from after an FPSO offtake system failure at the Torosa FPSO location. FPSO Torosa the system failure at offtake an FPSO after fuel tank fuel Shoals. rupturetank nearthe Rowley near the Rowley Shoals. Rowley near the rupture fueltank vessel a diesel after marine of release surface an instantaneous from offtake system failure at the Torosa FPSO location. Torosa failure at the system offtake FPSO an after Condensate Torosa stabilised of release surface an instantaneous from rupture near the Rowley Shoals. Rowley near the rupture fueltank vessel a after diesel marine of release surface an instantaneous resulting from offtake system failure at the Torosa FPSO location. Torosa failure at the system offtake a after Condensate Torosa stabilised of release surface an instantaneous from Pred 1 or above at oil concentrations floating of probability annualised Predicted locations Transect location. FPSO Torosa the failure at system offtake an FPSO after Condensate Torosa stabilised of release surface aninstantaneous for concentrations hydrocarbon Cross above 50 or at concentrations hydrocarbon aromatic dissolved of EMBA annualised Predicted location. FPSO failure Torosa at the system offtake FPSO an after Condensate Torosa stabilised 50 above at or concentrations to times minimum annualised Predicted above 50 at or concentrations hydrocarbon aromatic dissolved of probability annualised Predicted 3.1. in Figure areshown locations Transect location. FPSO Torosa at the failure system offtake an FPSO after Condensate Torosa stabilised of release surface an instantaneous Cross FPSO location. Torosa failure at the system offtake FPSO an after Condensate Torosa stabilised of release surface an instantaneous from annual Predicted location. FPSO Torosa the failure at system offtake an FPSO after Condensate above 100 or at concentrations oil entrained to by contact times minimum annualised Predicted location. FPSO failure Torosa at the system FPSO offtake an after Condensate Torosa stabilised of release surface an instantaneous resulting from 100 or above at oil concentrations entrained of probability annualised Predicted 100 above at or oil concentrations shoreline of probability annualised Predicted 10 or above at oil concentrations floating of EMBA annualised Predicted 1 or above at oil concentrations floating of EMBA annualised Predicted 10 above or at oil concentrations tofloating by contact times minimum annualised Predicted Predicted annualised smoothed EMBA of floating oil concentrations at or above 1 or above at oil concentrations floating of EMBA smoothed annualised Predicted 10 above or at oil concentrations to floating by contact times minimum annualised Predicted 1 above or at oil concentrations to floating by contact times minimum annualised Predicted
g/m g/m g/m
icted annualised probability of floating oil concentrations at or above 10 or above at oil concentrations floating of probability annualised icted NWS Project NWS 2 - -
section transects of predicted annualised maximum dissolved aromatic dissolved aromatic maximum annualised predicted of section transects en maximum annualised predicted of section transects 2 2 resulting from an instantaneous surface release of marine diesel after a ves a after diesel of release marine surface an instantaneous from resulting
resulting from an instantaneous surface r surface an instantaneous resulting from resulting from an instantaneous surface release of marine diesel after a vessel vessel a diesel after marine of release surface an instantaneous resulting from
......
are shown in Figure 3.1. Figure in shown are ppb resulting from an instantaneous surface release of stabili of release surface an instantaneous from resulting ppb Toros stabilised of release surface an instantaneous from resulting ppb
ppb resulting from an instantaneous surface rele surface an instantaneous from resulting ppb
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Quantitative Spill Risk Assessment Risk Spill Quantitative ised EMBA of entrained oil concentrations at or above 100 at or above concentrations oil entrained of EMBA ised
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ppb resulting from an instantaneous surface release of of release surface an instantaneous from resulting ppb
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......
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contact by dissolved aromatic hydrocarbon hydrocarbon aromatic dissolved by contact |
...... PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 ......
| 27 November 2019 November 27 ...... elease of stabilised Torosa Condensate Condensate Torosa stabilised of elease ......
...... ase of stabilised Torosa Torosa stabilised of ase trained oil concentrations for for concentrations trained oil ......
...... r a vessel fuel tank fueltank vessel a r
sed Torosa Torosa sed g/m
...... 133 ...... 130 g/m ...... 124
2 g/m
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...... 131 resulting ...... 112 ...... 115 n FPSO FPSO n
2
...... 123 ...... 121 ...... 116 g/m
ppb ppb 2 resulting a
...... 132 g/m sel fuel 2
...... 129 2
...... 109
...... 118 ...... 122 Page ..110 ..111 ..117
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1799 10D Tech nTeicalchnical St udiStudieses 1800 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
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Figure 3.52 Predicted annualised smoothed EMBA of floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 134 Figure 3.53 Predicted annualised probability of shoreline oil concentrations at or above 100 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 135 Figure 3.54 Predicted annualised probability of entrained oil concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 138 Figure 3.55 Predicted annualised minimum times to contact by entrained oil concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 139 Figure 3.56 Predicted annualised smoothed EMBA of entrained oil concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 140 Figure 3.57 Cross-section transects of predicted annualised maximum entrained oil concentrations for an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals. Transect locations are shown in Figure 3.1...... 141 Figure 3.58 Predicted annualised probability of dissolved aromatic hydrocarbon concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 144 Figure 3.59 Predicted annualised minimum times to contact by dissolved aromatic hydrocarbon concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 145 Figure 3.60 Predicted annualised smoothed EMBA of dissolved aromatic hydrocarbon concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals...... 146 Figure 3.61 Cross-section transects of predicted annualised maximum dissolved aromatic hydrocarbon concentrations for an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals. Transect locations are shown in Figure 3.1...... 147 Figure 4.1 Time-varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well, for the replicate case with the minimum time to floating oil contact with the offshore edge(s) of any shoreline receptor polygon (at a threshold of 10 g/m2), the minimum time to entrained/dissolved oil contact with the offshore edge(s) of any shoreline receptor polygon (at a threshold of 500 ppb) and the minimum time to commencement of oil accumulation at any shoreline receptor (at a threshold of 100 g/m2)...... 149 Figure 4.2 Time-varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well, for the replicate case with the maximum cumulative oil volume accumulated across all shoreline receptors and at any individual shoreline receptor (exceeding a threshold of 100 g/m2)...... 150 Figure 4.3 Time-varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location, for the replicate case with the minimum time to floating oil contact with the offshore edge(s) of any shoreline receptor polygon (at a threshold of 10 g/m2)...... 151
,Figure 4.4 Time-varying areal extent of potential exposure at defined floating oil, entrained oil dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
ical www.rpsgroup.com/mst Page xi n ch e T 10D
Figure 4.8 Figure 4.7 Figure 4.6 Figure 4.5 REPORT www.rpsgroup.com/mst MAW0815J
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Browse to NWS Project NWS to Browse receptor (excee receptor shoreline individual at any and receptors all shoreline across accumulated oil volume cumulative maximum the with case the replicate for location, FPSO Torosa at the rupture commencement of oil accumulation at any shoreline receptor (at a threshold of 100 of a threshold (at receptor at any shoreline oilaccumulation of commencement time to minimum the with case the replicate for location, FPSO Torosa at the rupture (exceeding a threshold of 100 of threshold a (exceeding s individual any at and receptors all shoreline across accumulated volume cumulativeoil maximum the with case replicate the for Shoals, the Rowley near rupture fueltank avessel after diesel marine of release surface an instantaneous concentrat oil threshold shoreline and hydrocarbon aromatic dissolved Time 100 of threshold a (exceeding shoreline receptor individual at any and receptors all shoreline across accumulated volume oil cumulative fai system offtake an FPSO after Condensate Torosa stabilised of release surface an instantaneous from resulting concentrations, oil threshold shoreline and hydrocarbon aromatic dissolved Time a 24 from resulting concentrations, oil threshold shoreline and hydrocarbon aromatic dissolved Time a 24 from resulting concentrations, oil threshold shoreline and hydrocarbon aromatic dissolved Time 500 of a threshold (at polygon any receptor of shoreline edge(s) with offshore the oil contact entrained/dissolved the replicat for location, FPSO Torosa at the rupture a 24 ------hour surface hour vessel cargo a after Condensate stabilised Torosa of release surface hour tank vessel cargo a after Condensate stabilised Torosa of release surface hour varying areal extent of potential exposure at defined floating oil, entrained oil, entrained oil, floating defined at exposure potential of extent varying areal varying areal oil, entrained oil, floating defined at exposure potential of extent varying areal oil, entrained oil, floating defined at exposure potential of extent varying areal lure at the Torosa FPSO location, for the replicate case with the maximum maximum the with case replicate the for location, FPSO Torosa at the lure
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Quantitative Spill Risk Assessment Risk Spill Quantitative ding a threshold of 100 of a threshold ding
release of stabilised Torosa Condensate after a vessel cargo tank tank vessel cargo a after Condensate stabilised Torosa of release extent of potential exposure at defined floating oil, entrained oil, entrained oil, floating defined at exposure potential of extent
g/m ppb). 2 ).
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g/m
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g/m e case with the minimum time to minimum the with case e 2 ).
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horeline receptor receptor horeline ions, resulting from from resulting ions, ...... 155 ...... 152 ...... 156
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g/m ...... 154 2 ).
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1801 10D Tech nTeicalchnical St udiStudieses 1802 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
EXECUTIVE SUMMARY RPS was commissioned by Woodside Energy Ltd (Woodside) to undertake a quantitative spill risk assessment of hypothetical hydrocarbon spill scenarios related to the proposed Browse Joint Venture (BJV) Browse to North West Shelf Project. The Browse hydrocarbon resource includes the Brecknock, Calliance and Torosa reservoirs, which are approximately 400 km north of Broome. The primary assessment location is in the vicinity of complex reef structures consisting of Scott Reef North, Scott Reef South and Seringapatam Reef. These are coral atolls that rise steeply from the surrounding shelf. The main objective of the study was to provide an assessment of the probabilities of oil contact (at greater than defined minimum concentrations), the potential concentrations that might be involved, and the minimum state of weathering of the oil in the case of a release of hydrocarbons. The assessment considers several specific spill scenarios involving different sources, spill durations and oil types, which were defined by Woodside to represent credible scenarios. Woodside identified four hydrocarbon spill scenarios for investigation, including one two-phase surface/subsea well blowout scenario and three other surface inventory/fuel spill scenarios. Oil spill modelling was undertaken using a three-dimensional oil spill trajectory and weathering model, SIMAP (Spill Impact Mapping and Analysis Program), which is designed to simulate the transport, spreading and weathering of specific oil types under the influence of changing meteorological and oceanographic forces. Near-field subsea discharge modelling was undertaken using OILMAP, which predicts the droplet sizes that are generated by the turbulence of the discharge as well as the centreline velocity, buoyancy, width and trapping depth (if any) of the rising gas and oil plumes. To define trends and variations in the potential outcomes of a given scenario, a stochastic modelling process was followed for all scenarios, whereby SIMAP was applied to repeatedly simulate the defined spill scenarios using different samples of current and wind data selected randomly from historic time series data representative of the study area. Results of the repeated simulations were then statistically analysed and mapped to define contours of risk around the release point. The main findings of this study are as follows: Metocean Influences • Tidal flows within the reef complex will have a significant influence on the short-term trajectory of any oil spilled at the modelled release sites, irrespective of the seasonal conditions. • Large-scale drift currents will have a significant influence on the trajectory of any oil spilled at the modelled release sites, irrespective of the seasonal conditions. The prevailing drift currents will determine the trajectory of oil that is entrained beneath the water surface. • Interactions with the prevailing wind will provide additional variation in the trajectory of spilled oil, and marked variation in the prevailing drift current and wind conditions will be expected over the duration of a long-term release. This will be expected to increase the spread of hydrocarbons during any single event. Oil Characteristics • The unstabilised Torosa Condensate mixture specified for the sea-surface release phase of the Scenario 1 blowout is a pre-processed condensate that is a mixture of volatile and persistent hydrocarbons with significant proportions of highly volatile and residual components. If the sea-surface release phase unstabilised Torosa Condensate mixture is exposed to the atmosphere, around 17% of the mass is expected to evaporate in around 24 hours, another 33% within a few days, and the remaining 51% is expected to persist in the marine environment until decayed due to photochemical and biological
degradation. If the unstabilised Torosa Condensate mixture specified for the subsea release phase were to be exposed to the atmosphere, these proportions are expected to be 54%, 21% and 25%, respectively. udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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• • • Unstabilised Torosa Conden Torosa Unstabilised • Scenario 1: Long • Figures Contour of Interpretation Stochastic of Summary • • REPORT www.rpsgroup.com/mst MAW0815J • • • • to be contacted by floating oil concentratio floating by to be contacted Central Scott Reef this receptor. treate of 34.3 of Floating oil at 10 at oil Floating probabilities of shoreline oil accumulation in excess of the 100 of excess in accumulation oil shoreline of probabilities highest to have the arepredicted (18%) Reef Ashmore Island and (22%) Cartier location, the release Floating oi Floating to 143 Entrai to approximately 863 to approximately Islet, with a maximum accumulated volume of 827 of volume accumulated maximum a with Islet, Potentia boundaries that define boundaries receptor of that set Note the system. Reef the Scott comprise that receptors the on focused are scenario relea the of location The the over ful oil trajectories predicted the of an aggregation are each scenario for assessment the stochastic of outcomes spatial mapped The environment. degr the will regulate entrainment of influence the types, all hydrocarbon For decayed. until environment in marine the persist to expected bewould 5% and remaining the the of 41% around atmosphere, the to exposed If 4. Scenario in considered been has and components residual and in persist to expected will be 14% remaining the and days, few a within 8% another hours, 24 around in evaporate to expected be will proportion a significant contains 3, 2 and Scenarios in considered been which has by and the FPSO processed been which has to condensate which refers Condensate, Stabilised Torosa Marine diesel is a mixtu is diesel Marine residual of hydroc proportion and alow excess of the 100 excess Central Scott Reef The contact of 46 hours after commencement of release. of commencement after hours 46 of contact Reef Central Central Reef Scott shorelineas with same the South, overlap Scott Reef and Central Reef Scott receptors, twoother of These outcomes do not depict a hydrocarbon hydrocarbon a do not depict outcomes These Floating oil at concentrations equal to or greater than the 10 the than greater or to equal concentrations at oil Floating oil impacts. some of reporting duplicated implies this and areas, overlapping event. the spill of commencement after time pointin at some locations individual for concentrations at defined exposure of probability the simulation. spill hydrocarbon individual an of full duration the over predicted coverage overall represent the
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Browse to NWS Project NWS to Browse d as a submerged feature floating oil ispredict floating feature a submerged as d ned oil at concentrations equal to or greater th equal to orgreater oil atned concentrations
km from the spill site. from km kg/m l for accumulation of oil on shorelines is predi is shorelines oil on of accumulation for l l concentrations at the 10 at the concentrations l
mass would be expected to evaporate in around 24 hours, anothe hours, 24 around in evaporate to expected be would mass 2
. The predicted zone of shoreline impact is impact zone shoreline of . predicted The –
Sandy Islet so reported accumulations for these receptors are a duplication. are receptors these for accumulations reported so Islet Sandy
g/m g/m -Term (77
2 km from the spill site. from km 2
-
reaches Scott Reef North in all replicate simulations, but as Scott Reef North is is North Reef Scott as but simulations, replicate all in North Reef Scott reaches threshold withp a threshold
Quantitative Spill Risk Assessment Risk Spill Quantitative re of volatile and persistent hydrocarbons with low percentages of highly volatile highlyvolatile of with percentages low hydrocarbons volatilepersistent andof re the Scott Reef system the this for of purposes system Scott Reef the se is adjacent to the Scott Reef system. Most of the predicted impacts from this from impacts predicted the of Most system. Reef Scott the to is adjacent se –
Sandy Islet receptor is predicted to experience shoreline oil accumulation in accumulation oil shoreline experience to is predicted receptor Sandy Islet
the marine environment until decayed. until environment marine the –
Sandy Islet is treated as an emergent feature. This receptor is predicted is predicted receptor This feature. emergent an as is treated Islet Sandy l duration of many individual hydrocarbon spill hydrocarbon individual of many lduration -Day) Surface/Subsea Blowout of
g/m Assessment Results Assessment sate at the TRA at the sate arbons. If exposed to the atmosphere, around 78% of the mass the of mass 78% around exposedto the atmosphere, If arbons. 2
robability of 92%. With regard to shoreline rece to shoreline regard 92%. of With robability threshold are predicted to be focused on the Scott Reef system. system. Reef Scott the on be focused to predicted are threshold ns of 10 of ns
slick or plume at any particular instant in time in instant particular at any plume or slick
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
m g/m an the 100an
ed to drift over rather than make direct contact with with directcontact make than rather over todrift ed cted to be significant for Scott Reef Central Central Reef Scott for significant be to cted 3
and a maximum local accumulated concentration concentration local accumulated a maximum and | 2 restricted to Sandy Islet. Note that the boundar the that Note Islet. to Sandy restricted
27 November 2019 November 27 with a probability of 8% and amin 8% of with aprobability
g/m -C Well
g/m
ppb threshold is predicted to be found up up to beis predicted found threshold ppb 2
threshold could potentially be fou be potentially could threshold 2
threshold.
study have some intentional intentional some have study
ee of mass retention in the the retention in mass of ee
r 54% within a few days, days, few a within 54% r simulations and indicate indicate and simulations
of volatile compounds volatile compounds of ptors further from further ptors
imum time totime imum , nor do they , nor do they
–
Sandy Sandy Page nd up up nd ies ies
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1803 10D Tech nTeicalchnical St udiStudieses 1804 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
• Contact by entrained oil at concentrations equal to or greater than 100 ppb is generally predicted for Scott Reef receptors including Scott Reef North (100%). Seringapatam Reef is also predicted to be contacted at 100 ppb (87%). • The maximum entrained oil concentration forecast for any receptor is predicted as 23.6 ppm at Scott Reef North. • Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 50 ppb threshold are predicted to be found up to around 673 km from the spill site. • Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 50 ppb is generally predicted for Scott Reef receptors including Scott Reef North (100%). Seringapatam Reef is also predicted to be contacted at 50 ppb (85%). • The maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as 13.9 ppm at Scott Reef North.
Scenario 2: Short-Term (24-Hour) Surface Release of Stabilised Torosa Condensate after a Vessel Cargo Tank Rupture at the Torosa FPSO Location • The location of the release is adjacent to the Scott Reef system. Most of the predicted impacts from this scenario are focused on the receptors that comprise the Scott Reef system. • Floating oil at concentrations equal to or greater than the 10 g/m2 threshold could potentially be found up to 126 km from the spill site. • Floating oil concentrations at the 10 g/m2 threshold are predicted to be focused on the Scott Reef system. The Scott Reef South and Scott Reef Central shoreline receptors are predicted to be contacted by floating oil concentrations at the 10 g/m2 threshold with probabilities of 6.5% and 2%, respectively. At these receptors, the corresponding minimum times to contact at this threshold are 21 hours and 57 hours. • The three Scott Reef receptors that share a common shoreline, Scott Reef South, Scott Reef Central and Scott Reef Central – Sandy Islet, are predicted to experience shoreline oil accumulation in excess of the 100 g/m2 threshold with a probability of 20.5%. • Potential for accumulation of oil on shorelines is predicted to be moderate, with a maximum accumulated volume of 212 m3 and a maximum local accumulated concentration of 9.5 kg/m2 forecast at the Scott Reef South, Scott Reef Central and Scott Reef Central – Sandy Islet receptors. • Entrained oil at concentrations equal to or greater than the 100 ppb threshold is predicted to be found up to around 890 km from the spill site. • Contact by entrained oil at concentrations equal to or greater than 100 ppb is generally predicted for Scott Reef receptors including Scott Reef North (48.5%). Seringapatam Reef is also predicted to be contacted at 100 ppb (22.5%). • The maximum entrained oil concentration forecast for any receptor is predicted as 30.5 ppm at Scott Reef North. This result is greater than the maximum concentration forecast in Scenario 1, where a larger total volume of oil is released. The difference in maximum entrained oil concentration is attributable to the higher release rate in Scenario 2 (18,000 m3/day compared to 1,846 m3/day for Scenario 1). The Scott Reef North receptor is close enough to the release site that the peak concentration is influenced more by the rate of oil released in one day than the total volume of oil released. • Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 50 ppb threshold are predicted to be found up to around 517 km from the spill site. • Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 50 ppb is generally
predicted for Scott Reef receptors including Scott Reef North (41.5%). Seringapatam Reef is also predicted to be contacted at 50 ppb (15.5%). udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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• • • • • • • • FPSO Torosa Condensate after an FPSO Offtake System Failure at the Torosa Scenario 3: Short • REPORT www.rpsgroup.com/mst MAW0815J • • Diesel after aVessel Fuel Tank Ru Scenario 4: Short • • • • probabilities of floating oil contact at the 10 at the oil contact floating of probabilities Dissolved aromatic hydrocarbons at con hydrocarbons aromatic Dissolved North and Scott Reef North North Scott Reef North and 1.8 T 50 than to greater or equal at concentrations hydrocarbons aromatic dissolved Contact by at Scott Reef North(23%) Reef at Scott 271 around up to found be to predicted The maximum entrained oil concentration forecast for any receptor is predicted as 6.4as is for predicted any receptor forecast concentration entrained oil The maximum Reef State State Reef 100 12.7 North North receptor is predicted to be contacted by floating oil concentrations at the 10 at the concentrations oil floating by contacted be to is predicted receptor probability of 15%, with a correspo with 15%, of probability of 8 of Potential Central Central Th 24 hours. of time contact a 1.5% minimum and of a probability with threshold to 67 to 82 concentrations equal equal to concentrations or greater than 10 Floating oil at concentrations equal to or greater than the 10 the than greater or to equal concentrations at oil Floating system. Reef Scott the comprise that receptors the on are focused scenario is release the of location The diss maximum The Floating oil at concentrations concentrations at oil Floating Shoals. the Rowley of vicinity the in are focused this scenario from impacts the predicted of Most Reef. Mermaid adjacent to is the release location of The Scott Reef receptors, including Scott Reef Nor Reef Scott including receptors, ScottReef Contact by entrained oil at concentrations equal to or greater than 100 than greater or to equal concentrations at oil entrained by Contact 242 to around equal to or oil at concentrations Entrained shoreline receptors. a minimum time to contact of less than 1 less of to contact time a minimum The Scott Reef South receptor is predicted to be contacted by floating oil concentrations at the 10 oil concentrations by floating contacted to be ispredicted South Scott Reef receptor The Given Given lies the Argo that spill within location the he maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as as is predicted receptor any for forecast concentration hydrocarbon dissolved aromatic he maximum e Scott Reef shoreline, encompassed by t by encompassed shoreline, e Scott Reef
ppm at Scott Reef North and Scott Reef North Reef Scott and North at Scott Reef ppm |
g/m
Location m ppm at Scott Reef North. Reef at Scott ppm
Browse to NWS Project NWS to Browse km from the spill site. from km km from the spill site. from km – 3
Lagoon (20%). Lagoon – 2 and a maximum local accumulated concentration of 715 of local concentration accumulated and amaximum
for accumulation of oil on shorelines is oil shorelines on of accumulation for
threshold with a probability of 2.5%. of probability a with threshold Sandy Islet receptors, is predicted to experience shoreline oil accumulation in excess of the of in excess accumulation oil shoreline to experience ispredicted receptors, Islet Sandy M arine Park and Rowley Shoals Shoals and Park Rowley arine
km from the spill site. from km
olved aromatic hydrocarbon concentration forec concentration hydrocarbon olved aromatic
- - Term (Instantaneous) Surface Release of Stabilised Term (Instantaneous) Surface Release of M -
Quantitative Spill Risk Assessment Risk Spill Quantitative
and Scott Reef North Scott Reef and
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equal to or greater than the 10 the than greater or to equal Flats. adjacent to the Scott Reef system. Most of the predicted impacts from this from impacts predicted the of Most system. Reef Scott the to adjacent
nding minimum contact time of 5 hours. At the Rowley Shoals Shoals Rowley At5 hours. the of time contact ndingminimum
km from the spill site. from km
hour. The Rowley Shoals Shoals Rowley The hour. centrations equal to or greater than the than greater or to equal centrations
greater than the 100 than greater g/m
g /m –
he Scott Reef South, Scott Reef Central and Scott Reef Scott Reef and Central Reef Scott South, Reef Scott he 2
pture near the Rowley near Shoals pture
th (28%), Scott Reef North North Scott Reef th (28%),
2 predicted to be low, with a maximum accumulated volume volume accumulated maximum with a low, be to predicted Imperieuse Reef State State Reef Imperieuse i
s forecast at this receptor with a proba a with receptor at this forecast s – threshold are forecast to be 1% or l or be 1% to are forecast threshold |
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Flats (22.5%). Flats Rev 4 – - Rowley Terrace Terrace Rowley Lagoon.
| 27 November 2019 November 27
g/m g/m
ppb threshold is pr threshold ppb 2 2
threshold could potentially be found u found be potentially could threshold thr –
Mermaid Reef Reef Mermaid ast for any receptor is predicted as as is predicted receptor any for ast eshold could potentially be found up up found be potentially could eshold
g/m ppb is predicted at various northern ppb atnorthern various is predicted M
M arine Park area, floating oil at at oil area, floating Park arine 2 arine Park shoreline receptors, shoreline receptors, Park arine
– forecast at three Scott Reef ScottReef at three forecast
Flats (25%) Flats
edicted to be found up up toedicted be found
M g/m 50 ess. arine Park shoreline arine Park
ppb threshold are are threshold ppb ppm at Scott Reef at Scott Reef ppm bility of 100% and and 100% of bility 2 threshold wi arine arine
ppb is predicted is predicted ppb and Scott Reef Reef Scott and
–
Clerke Clerke Page
g/m th a
p xvi 2
1805 10D Tech nTeicalchnical St udiStudieses 1806 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
• The Rowley Shoals – Mermaid Reef Marine Park receptor is predicted to experience shoreline oil accumulation in excess of the 100 g/m2 threshold with a probability of 1%. • Potential for accumulation of oil on shorelines is predicted to be low, with a maximum accumulated volume of 6 m3 forecast at the Rowley Shoals – Clerke Reef State Marine Park and a maximum local accumulated concentration of 491 g/m2 forecast at the Rowley Shoals – Mermaid Reef Marine Park. • Entrained oil at concentrations equal to or greater than the 500 ppb threshold is predicted to be found up to around 371 km from the spill site. • Contact by entrained oil at concentrations equal to or greater than 500 ppb is predicted at Argo-Rowley Terrace Marine Park (57%), Rowley Shoals – Mermaid Reef Marine Park (33.5%) and Rowley Shoals – Clerke Reef State Marine Park (7.5%). • The maximum entrained oil concentration forecast for any receptor is predicted as 167.6 ppm at Argo- Rowley Terrace Marine Park. • Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 500 ppb threshold are predicted to be found up to around 43 km from the spill site. • Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 500 ppb is predicted at Argo-Rowley Terrace Marine Park (8.5%) and Rowley Shoals – Mermaid Reef Marine Park (1.5%). • The maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as 2.2 ppm at Argo-Rowley Terrace Marine Park.
udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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• • •
minimum concentrations), the potential con the potential concentrations), minimum defined than greater (at oil contact of the probabilities of modelling, spill stochastic through assessment, rec and sensitive resources surrounding for to of hydrocarbons exposure on the risk focused assessment The (PetroChina). Ltd Pty (Australia) Investment International PetroChina and Ltd (MIMI) Develo BP (Shell), Pty Ltd Australia Shell Ltd, Browse Pty the BJV: of on behalf and Woodside for is Operator Ltd (Woodside) Energy Woodside (NRC). ~85 a infrastructure Project Shelf (NWS) North West existing to gas export and will system production a subsea Woodside Woodside weathering of the oil in case of a release of hydrocarbons. of a release of in case oil the of weathering The BJV propose to develop the Browse resource using tw using resource Browse the to develop BJVpropose The the to related spill scenarios hydrocarbon hypothetical of ( Ltd Energy Woodside by was commissioned RPS 1.1 1 REPORT www.rpsgroup.com/mst MAW0815J coastline 425 approximately located reservoirs Shelf West North surface/ cubic feet per day (MMscf/d) export capacity (annual daily average). The The average). daily (annual capacity export per day(MMscf/d) feet cubic • in summarised are this in study assessed the scenarios details of The in is shown scenario assessed each for spill location the of regional context The study. this in period annual an over assessed and manner a stochastic in modelled
eptors ifeptors Scenario 4: Scenario a 72 FPSO Scenario 3: Scenario 2: Scenario containment after a vessel cargo tank rupture tank cargo avessel after containment ru Shoals (17° Shoals location FPSO the Torosa Condensate fro Scenario 1: Scenario
km km pture
- the TRA m subsea
. | -
day spur line and a ~900 linespur a and Background INTRODUC Browse to NWS Project NWS to Browse
offtake system failure system offtake
identified four hydrocarbon spill scenarios for investigation, including a a including investigation, for scenarios spill hydrocarbon four identified .
defined spill scenarios were to occur. The main objectives of the study were to provide an an provide were to study the of objectives The main occur. were to spill scenarios defined subsea
well blowout and three and well blowout
A long A
A short A A short A Project. The The Project. 16' A at the Torosa FPSOlocation Torosa at the C well (13° well C
short 52.8" release phase, representing loss of containment after a loss of well control of aloss after containment of loss representing phase, release - term (77 term - - term (instantaneous) surface release of 2,000 of release surface (instantaneous) term term (instantaneous) surface release of 768 of release surface (instantaneous) term
-
term (24 term S, 119° S, -
Quantitative Spill Risk Assessment Risk Spill Quantitative Browse hydrocarbon resource is located in the Brecknock, Calliance and Torosa Torosa and Calliance Brecknock, the in is located resource hydrocarbon Browse
58'
TION km Browse Trunkline (BTL), which will tie in near the North Rankin Complex Complex Rankin theNorth near in willtie which (BTL), Browse Trunkline km (13° - . day) uncontrolled release of 142,154 of release uncontrolled day)
12.5"
- 39'
hour) uncontrolled surf uncontrolled hour) pmen 58'
30.8" km north of Broome and approximately 290 and approximately Broome north of km
15.1" S, 121° S, sur
ts Austra ts face inve face
cent E), representing loss of containment after a vessel fuel tank tank fuel vessel a after containment of loss representing E),
S, 122° S,
58' rations t rations
. Woodside
lia Pty Ltd (BP), Japan Australia LNG (MIMI Browse) Pty Pty Browse) (MIMI LNG Australia Japan PtyLtd (BP), lia (13°
37.7"
ntory/fuel spills ( spills ntory/fuel |
01' PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
58'
hat might be involved, and the minimum state of state minimum and the be involved, hatmight E), with a 5 with a E), 28.5"
proposed proposed o FPSO facili o FPSO
15.1" | se of 18,000 of releaace se ) to undertake a quantitative spill risk assessment assessment risk spill aquantitative undertake to ) 27 November 2019 November 27
E), representing loss of of loss representing E),
S, 122° Browse Joint Venture (BJV) (BJV) Venture Joint Browse -
m day surface release phase followed by by phase followed release surface day Woodside Table Table m
m 3 ties with up to 1,100 million standard standard million to 1,100 up with ties 3 p
of of 3 unstabilised unstabilised of r 01'
o of marine diesel n diesel marine of p stabi 1
o 28.5" . 1 s
e and listed here: listed and Figure Figure , 2019). Each scenario was was 2019). Each , scenario lised lised d
FPSOs will be supplied by by supplied be will FPSOs
E
m ), representing loss of of loss representing ),
3 Torosa km off the Kimberley the Kimberley off km
1 containment after after containment of of . nsate nsate Conde Torosa 1 .
stabilised stabilised two phase sea phase two
ear the R the ear Condensate Condensate
.
Browse to Torosa owley Page via via an an at at
1 -
1807 10D Tech nTeicalchnical St udiStudieses 10D
Technical Studies 1808 PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERD
REPORT
Figure 1.1 Locations of the modelled hydrocarbon spill scenario release sites.
MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019 www.rpsgroup.com/mst Page 2
each different each under affected be would influence of zone potential within the locations Different conditions. different under Furthermore, the results are presented in terms of statistical p in terms are presented the results Furthermore, the should outcomes likely the to guide a as viewed be therefore should results once defined spill event spill defined once resu modelling the that note to important It is products. degraded and weathered highly represent would simulation, each of end which oil, floating remnant that expected is It analysis. inapplied the threshold the below decrease to concentrations oil for period time a sufficient allow to discharge the duration run for was Each simulation annual quantify to thearchive data from sampled mod the stochastic of results The an to time contact, minimum the contact, of probability the esti Risk slicks. spill individual by The contours should therefore be judged as contou as judged be therefore should contours The infl Ocean Indian eastern depth) depth) withtogether tidal windand tempora for a long thispurpose, For of contours to define mapped and analysed statistically were then simulations replicate the of Results area. study the of representative data the model Thus, separately. modelled dissolved)are and (entrained components Oil spill modelling was undertaken using a three using undertaken was modelling Oil spill 1.2 REPORT www.rpsgroup.com/mst MAW0815J disch the of turbulence the by are generated weatheri and spreading transport, the to simulate which isdesigned Program), Analysis and Mapping (Spill Impact different samples of current and wind data selected randomly from an historictime from randomly selected data currentwind and of samples different u scenarios spill defined the simulate repeatedly to applied was SIMAP whereby study, this in followed was potentia the in variations and definetrends To dissolve and to entrained exposure and features surface oil for slick to contact direct including a spill, of consequences potential wider the oil calcula to type oil an of properties and surface both simulates model SIMAP The trapping depth (if any) of the rising gas and oil plumes and gas rising the of any) (if depth trapping Near - uence will cover a larger area than the area that is likely to be affected during any one single spill event. event. any during spill single one is likelyaffected to be area thanthat the willa larger cover uence in - -
water emulsions. Moreover, the unique transport and dispersion of surface slicks and slicks surface of dispersion and transport unique the Moreover, wateremulsions. field
ng of ng mates were calculated from the multiple replicate simulations for each assessed scenario, including including scenario, assessed each for simulations replicate the multiple from werecalculated mates |
Stocha Browse to NWS Project NWS to Browse subsea l and spatial variations in large in variations spatial land
specific oil types under the influence of changing meteorological and oceanographic forces. forces. and oceanographic changing meteorological of influence the under oil types specific time
discharge modelling was undertaken using OILMAP, which predicts the droplet sizes that that sizes the droplet which predicts using OILMAP, was undertaken modelling discharge
series of environmental forces. Consequently, these contours for the potential zon the potential for contours these Consequently, forces. environmental of series stic spanning 10 years (2006years 10 spanning s have oc have s
- term archive of spatially of archive term d oil for organisms in the water column. in the organisms oil for d
-
Quantitative Spill Risk Assessment Risk Spill Quantitative
Modelling of Spill Scenarios of Spill Modelling risk around the release point. around release the risk
curred. The probability of the spill scenarios occurring is not considered. The The considered. is not occurring scenarios spill the of probability The curred. elling arelling te rates rates te - driven currents. Modelling was carried out using current and wind data data windand using current out carried was Modelling currents. driven e presented in Section 3. Section in presented e of evaporation and viscosity change, including the tendency to form form to tendency the including change, viscosity and evaporation of
of the s of - scale drift currents over the outer shelf waters (typi waters shelf outer the over currents drift scale lts presented in this document relate to the predicted outcomes outcomes predicted tothe relate document in this presented lts l outcome arge as w as arge - subsea - 2015, inclusive) was assembled. Current patterns accounted accounted patterns Current wasassembled. inclusive) 2015, dimensional oil spill trajectory and weathering model, SIMAP SIMAP model, weathering and trajectory oil spill dimensional - ised risks of contact at surrounding locations. of atcontact surrounding risks ised varia pecified spill, plus a further period after the cessation of of the cessation after period a further plus spill, pecified rs of probability and not representations of the area swept swept area the of representations not and probability of rs
| .
ble wind PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Rev releases and uses the unique physical and chemical chemical and physical unique the uses and releases s of a given scenario, a stochastic modelling scheme scheme modelling a stochastic scenario, a given of s d the potential concentrations that might be involved. be might that concentrations potential the d ell a ell
4
| 27 November 2019 November 27 s the centreline velocity, buoyancy, width and and width buoyancy, velocity, centreline the s and current data covering the data covering current and robabilit
may be p be may y maps, based on many simulations simulations on many basedy maps,
resent at low thresholds at the at the low thresholds at resent can becan us
series of series
spill scenarios occur. occur. scenarios spill
ed to understand understand edto wind and current wind current and
Timor Sea Timor
concentrations concentrations cally >20 cally
in - Page water water
sing sing e of e of and and 0
m
3
1809 10D Tech nTeicalchnical St udiStudieses 1810 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
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Table 1.1 Summary of the hydrocarbon spill scenarios assessed in a stochastic manner in this study.
Spilled Release Release Simulation Scenario Description Oil Type Volume Depth Spill Duration Period Coordinates Duration (m3) (m BMSL)
Unstabilised Loss of well control 13° 58' 12.5" S 1 Torosa 142,154 425 77 days 100 days Annual at the TRA-C well 121° 58' 37.7" E Condensate
Loss of containment Stabilised 13° 58' 15.1" S 2 after a vessel cargo Torosa 18,000 0 24 hours 56 days Annual 122° 01' 28.5" E tank rupture Condensate
Loss of containment Stabilised after an FPSO 13° 58' 15.1" S 3 Torosa 768 0 Instantaneous 42 days Annual offtake system 122° 01' 28.5" E Condensate failure
Loss of containment 17° 16' 52.8" S 4 after a vessel fuel Marine Diesel 2,000 0 Instantaneous 42 days Annual 119° 39' 30.8" E tank rupture
1.3 Deterministic Analysis After assessing the stochastic modelling outcomes for all scenarios, Woodside determined there was a requirement for additional model outputs to be provided for selected replicate simulations of each scenario in order to contextualise the stochastic contours. The results of the deterministic analysis are presented in Section 4.
1.4 Report Structure The near-field and far-field computational models, risk assessment methodology, environmental data used as input to the models, environmental threshold trigger levels defined for the assessment, characteristics of the oil types used in the modelling of the defined scenarios, and discharge plume characteristics for the subsea release scenario are described in detail in Section 2. Contour figures and tabulated results showing risk estimates for the receptors nominated by Woodside, produced for defined floating oil, entrained oil and dissolved aromatic hydrocarbon threshold concentrations, are presented in Section 3 to summarise the stochastic modelling outcomes. Tabulated results for floating oil, entrained oil, dissolved aromatic hydrocarbons and shoreline oil are presented in Section 4 to summarise the outcomes of the deterministic analysis. The overall findings of the study are summarised in Section 5.
udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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• • • The model calculates a distribution of the oil by ma oil by the of distribution a calculates The model tempe versus off distilled Input specifications f Input specifications (1998), French in French provided are events an SIMAP used in algorithms the of descriptions Technical processes. dynamic alg weathering SIMAP release. The after the oil that affect conditions wi competition dynamic in be will dissolution Because the compounds that have high have that compounds the Because oil of com so of high concentrations generate not will surface water the onto hydrocarbons of release the In contrast, adeep for the release of site at the t by affected strongly also are rates short purpose a using out carried was spill modelling The 2.1.1 2.1 2 REPORT www.rpsgroup.com/mst MAW0815J b land from downwind distance (i.e. fetch and direction wind speed, the sustained from heights wave estimating wave energ to correlated are rates emulsification and dissolution Entrainment, oil types. bet differentiate can model the process, this By compounds. volatile the more of loss de will rates Evaporation oil. the of weathering state of French 1998; French, Rines, & (French model Assessment Damage Resource Natural EPA US the of evolution an is SIMAP pr and scenario, pro weathering and transport the simulate to is designed model This Program). Assessment and Mapping Impact speeds, the surface area of the slick and entrained the slick of area surface the speeds, rates Evaporation considered. being oil type the specific account for algorithms These photo and bacterial evaporation, sedimentation, components, e formation, slick and droplet include These weat the of all calculate algorithms tension, phy The processes transport and weathering between the interaction for accounts also oil). model The atmosp dissolved compounds), (entrained oil and column m spilled the of partitioning the for accounting to algorithms t both arriers) arriers)
cesses that affect the outcomes of hydrocarbon spills to the sea, accounting for the specific oil spill the specific type, for to the of sea, accounting hydrocarbon spills the outcomes that affect cesses pounds. However, subsequent exposure of the surface slick to breaking waves will enhance entrainment entrainment enhance will waves to breaking slick surface the of exposure subsequent pounds. However, Dissolved hydrocarbons (principally the aromatic and short and aromatic the (principally hydrocarbons Dissolved Entrained oil (non Entrained Surface
- he surfac he into the upper water column as oil droplets, which will enhance dissolution of the soluble components. components. soluble the of dissolution will enhance which droplets, oil as column water upper the into chained hydrocarbon compounds, and the surface area at the oil/water interface of slicks. Dissolution Dissolution slicks. of interface oil/water at the area surface the and compounds, hydrocarbon chained
sical transport algorithms calculate transport and spreading by physical forces, including surface surface including forces, physical by and spreading calculate transport algorithms transport sical gravity and wind and current forces for both surface slicks and oil within the water column. The fates The watercolumn. the and oilwithin slicks both surface for forces current and wind and gravity
| at different locations in the domain. Dissolution rates are dependent upon the proportion of soluble, soluble, of proportion the upon dependent are rates Dissolution domain. in the locations at different
Description of the Models the of Description SIMAP MODELLING METHODOL MODELLING Browse to NWS Project NWS to Browse - bound or floating oil. or floating bound account for both physical transport and weathering processes. The latter are important for for important are latter The processes. weathering and transport physical both for account e slick and the three the and e slick evailing evailing vary over space and time dependent on the prevailing sea temperatures, wind and current wind current and on temperatures, sea thedependent prevailing and space time over vary
or oilor ty et al. - dissolved oil droplets that are p are that oil droplets dissolved wind and current patterns. current and wind rature) and the aromatic/aliphatic component ratios within given boiling point ranges. ranges. point boiling given within ratios component aromatic/aliphatic the and rature)
, 1999) and is designed to simulate the fate and effects of spilled oils and fuels for for fuels and oils spilled of effects and fate the simulate to is designed and , 1999) -
Quantitative Spill Risk Assessment Risk Spill Quantitative pes include the density, viscosity, viscosity, pour density, include the pes
- - he level level he hering pr hering dimensional plume that is generated in the water column. SIMAP includes includes SIMAP water column. the in is generated that plume dimensional sea discharge at high pressure. at discharge sea
solubili th the balance dictated by the nature of the release and the weather the and release the of nature the by dictated balance the th of turbulence. For example, dissolution rates will be relatively high high will relatively rates be dissolution example, For turbulence. of ntrainment by wave action, emulsification, dissolution of soluble soluble of dissolution emulsification, action, wave by ntrainment ocesses known to be important for oil spilled to marine waters. waters. to marine spilled oil for important be to known ocesses et al. et ass over over ass ty also have high volatility, the processes of evaporation and and evaporation of processes the volatility, high have also ty
-
ss intoss t droplets
developed oil spill trajectory and fat and trajectory oil spill developed (1999) and French and (1999)
| hysically entrained by waveaction). by entrained hysically
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 crease over time, depending on the calculated rate of of rate calculated the on depending time, over crease time between the water surface (surface slick), water water slick), (surface surface water the between time here (evaporated compounds) and land (stranded and land (stranded compounds) here (evaporated he following components: he following
OGY that are exposed to the atmosphere wellas that atmosphere are exposed as to the the | 27 November 2019 November 27 - - chained aliphatic compounds). aliphatic chained chemical deca chemical
orithms i orithms - - point, distillation curve (volume of oil (volume curve point,distillation McCay (2004).
nclude terms to represent these to representthese nclude terms y and sho y d validations against real spill spill real against validations d y, which is accounted for by by y, for which is accounted ween the ween the
es model, es
reline interactions. reline interactions. fates of different different of fates .
SIMAP (Spill (Spill SIMAP Page 1997; 1997; luble luble
5
1811 10D Tech nTeicalchnical St udiStudieses 1812 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
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• Evaporated hydrocarbons. • Sedimented hydrocarbons. • Decayed hydrocarbons.
2.1.2 OILMAP SIMAP uses specifications of the depth of release to represent spills onto the water surface or into the water column. For subsea release scenarios, where oil will initially be entrained in the water column as droplets of oil in suspension, it is necessary to define the size-distribution of the droplets and their initial vertical distribution following the initial (within minutes) discharge processes. These processes include the jet induced by the discharge and the dynamic evolution of any associated gas plume. This size distribution will regulate the time for oil droplets to rise to near the sea surface and affect their ability to surface and become floating oil. High pressure releases (such as a pipeline rupture or gas/oil blowout) tend to generate a distribution with a small to median size (300 μm or less; Johansen, 2003). Due to their larger surface area to volume ratio, droplets of decreasing size will rise under buoyancy at a quadratically slower rate due to viscous resistance exerted by the surrounding water, which can be theoretically derived using Stokes’ Law:
2 V = [2 * 9.81 * R (ρo - ρw)] / 9µ
Where: V is the rising velocity of oil droplets; ρo and ρw are the mass density of oil and water, respectively; R is the radius of the oil droplet; and µ is the dynamic viscosity of water. If oil is discharged with little or no gas, the oil droplets must rise to the surface under their own buoyancy (resisted by water viscosity) after the dissipation of a relatively short (~1-2 m) discharge jet. However, if gas is discharged with the oil, it will rapidly expand on exiting the pressurised reservoir and continue to expand as it rises and water pressure reduces. As the discharge moves upward, the density difference between the expanding gas bubbles in the plume and the receiving water results in a buoyant force which drives the plume of gas, oil and water towards the surface. Oil in the release is rapidly mixed by the turbulence in the rising plume. These droplets (typically a few micrometres to millimetres in diameter) are rapidly transported upward by the rising plume; their individual rise velocities contributing little to their upward motion. As the plume rises, it continues to entrain ambient water, which reduces the buoyancy of the mixture and increases the radius of the plume (Chen & Yapa, 2007; Spaulding et al., 2000). In shallow water (<200 m) the rising plume of gas, oil and water will tend to reach the sea surface before deflecting as a radial, surface flow zone which will spread the oil droplets rapidly away from the centre of the plume (Spaulding et al., 2000). The velocity and oil concentrations in this surface flow zone decrease while the depth of the zone increases. Finally in the far field, where the plume buoyancy has been dissipated, ambient currents and the turbulence generated by wind generated waves will determine the subsequent transport and dispersion of the oil droplets. As water depths increase, the buoyancy of the rising plume is likely to be lost before the plume reaches the surface, because the gas begins to dissolve into the water column due to increased water temperatures and the density of the plume equalises with the surrounding water (Chen & Yapa, 2007; Spaulding et al., 2000). This results in a situation where the oil droplets will have a further distance to rise to the surface under their own buoyancy and be subject to horizontal displacement due to the prevailing water currents. The reduced velocity of these droplets will also increase their susceptibility to trapping by stratification in the water column, and mixing in the near surface layer (typically 5-10 m depth) generated by surface waves. As water depths increase further (beyond ~600 m), resulting in higher pressure and colder temperatures at the release depth, a further complication can arise due to part or all of the gas volume converting to a hydrate structure – a solid ice-like lattice structure with specific gravities on the order of 0.92 to 0.96 (Chen & Yapa, 2007; Spaulding et al., 2000). The conversion of the gas into gas-hydrates deprives the plume of its principal
source of buoyancy, leaving the oil droplets and gas hydrates to rise a longer distance under their own udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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• • • Risks are then summarised as follow as arethen summarised Risks time. over concentrations threshold defined exceed estimates concentration whether oil of calculate concentrations The b dividing and cell a grid within particles of mass the summing by step time each at calculated are concentrations particles, oil dissolved and entrained For divided by the are divided the by cell, within a grid located effects) dispersion and spreading for accounting (including in allmass oil particles di a into study region the by analysed dividing then are all simulations from collective records The forces. les time, over shoreline that contact a shoreline, the model records the accumulation of the accumulation records model the a shoreline, that contact particles any For steps. time regular at water column, the in or on oil) of mass given a (representing particles During each simulation, the SIM the simulation, each During frequently. less be represented will unusual aremore that conditions occur overstudy occur the simulations. the discharge as well as the centreline v centreline the well as as the discharge (Spaulding the droplet size distribu size thedroplet the receiving of profile temperature/salinity vertical theand viscosity, and density oil size; hole rate; discharge waterpressure); (hence depth the include the model to Inputs plume. i oil from of prediction the for extended model fates and trajectory oil spill is an OILMAP occupy. they that depth the at acting by currents transport to horizontal environmental conditions will be selected at a rate that ispropor that at a rate will be selected conditions environmental of a spill, because of theoutcomes possible measure an objective provides sampling approach stochastic This a long time data from ea for time thespill varying slic • The stochastic model within SIMAP performs a large number of simulati a large number SIMAP performs within stochastic model The 2.2 dro oil Hence, surface. the to reach buoyancy REPORT www.rpsgroup.com/mst MAW0815J ncluding ncluding mensional grid. For oil particles that are classified as as are classified that particles oil For grid. mensional k will be subject to a different sample of wind curre and of different sample a will to subject be k duri replicate spill simulations. For example, if example, For simulations. spill replicate of number by total the location at that threshold a specified above occurred contact instantaneous any concent a oil at which over time shortest the by calculated is location shoreline a to time potential The minimum The pr The m per mass the greatest is section shoreline each for oil predicted of potential concentration The maximum of the replicate simulations. the replicate of and calculating an and calculating section is calculated by determining the greatest mass per m mass greatest the determining by is calculated section shoreline each on accumulate potentially to oil predicted of concentrations maximum the of average The simulations.
2
ng 21 out of 100 simulations, a probability of exposure of 21% is indicated. 21% of exposure of a probability simulations, 100 of out 21 ng of shoreline calcu of |
those in deep water (>600 water deep in those Calculation of Exposure Risk Exposure of Calculation Browse to NWS Project NWS to Browse et al. obability of exposure to a location is calculated by divi by iscalculated location a to exposure of obability
ration ab ration , 2000). The blowout model predicts the droplet sizes that are generated by the turbulence of of turbulence the by aregenerated that droplet sizes the predicts model blowout The 2000). ,
a of the a of
region. More simulations will tend to use the most commonly occurring conditions, while while conditions, occurring commonly most to the use will tend More simulations region. series of wind and current data for the area. Hence, the transport and weathering of weathering of and thethe transport area. Hence, wind for of data series current and ove a particular threshold was calculated to travel from from travel to calculated was threshold particular a ove
s any mass that is lost to evaporation and/or subsequent removal by current and wind wind and current by removal subsequent and/or evaporation to is lost that anys mass average of these estimates across the simulations. across these estimates of average tion and the plume dimensions to the SIMAP model, for thelong for model, SIMAP to the dimensions plume andtion the
cell provides estimates of the concentration of oilin of th the concentration of estimates provides cell ch simulation. The model uses the spill time to select samples of current and wind currentwind and of to select samples the spill time uses model The simulation. ch lated to to lated -
Quantitative Spill Risk Assessment Risk Spill Quantitative AP model AP model
d for each grid cell, at each time step, are then analysed to determine determine to analysed then are step, at time each grideach cell, d for strand at any location within that section during any of of any during section within that location any at strand s:
m) where gas hydrate formation formation hydrate where gas m)
elocity, elocity, records the location (by latitude, longitude and depth) o and depth) longitude (by the latitude, location records y thevol plets wil plets
contact contact buoyancy, width and trapping depth (if any) of the rising of any) (if depth trapping andwidth buoyancy, ume of the grid cell. the grid of ume
| l have a longer period during which they will be subject will be subject which they haveduring period longer l a PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 being at the water surface (floating oil), the sum of the of sum the oil), (floating water surface the at being occurred at a location (above a specified threshold) threshold) a specified (above location a at occurred nt conditions.
| s 27 November 2019 November 27
2 tional to tional
of shor of ding the number of spill simulations where where spill simulations of number the ding
oil mass
water. T
can affect the fate of discharged oil oil discharged of fate the affect can eline during each replicate simulation simulation replicate eline each during
the frequency that these conditions conditions these that the frequency ons for a for ons
the source to the location in any any in location the to the source that arrives on each section of of section thatarriveson each his model was applied to supply supply to was applied his model at grid cell, at each time step. time each grid at cell, at
given spill site, randomly site,given randomly spill
subsea
oil/gas blowouts, blowouts, oil/gas - term discharge term the replicate replicate the f each of the each of f
three Page each each
gas gas
7 -
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• Similar treatments are undertaken for entrained oil and dissolved aromatic hydrocarbons. Thus, the minimum time to shoreline and the maximum potential concentration estimates indicate the worst potential outcome of the modelled spill scenario for each section of shoreline. However, the average over the replicates presents an average of the potential outcomes, in terms of oil that could strand. Note also that results quoted for sections of shoreline or shoal are derived for any individual location within that section or shoal, as a conservative estimate. Locations will represent shoreline lengths of the order of ~1 km, while sections or regions will represent shorelines spanning tens to hundreds of kilometres and we do not imply that the maximum potential concentrations quoted will occur over the full extent of each section. We therefore warn against multiplying the maximum concentration estimates by the full area of the section because this will greatly overestimate the total volume expected on that section. The maximum entrained hydrocarbon and maximum dissolved aromatic hydrocarbon concentration are calculated for water locations surrounding each defined shoreline (see Section 3.1). These zones are defined to provide a buffer area around shallow (<10 m) habitats to allow for spatial errors in model forecasts. The greatest calculated value at any time step during any replicate simulation is listed. These values therefore represent worst-case localised estimates (within a grid cell). The averages over all replicate values represent a central tendency of these simulated worst-case estimates. 2.3 Inputs to the Risk Assessment 2.3.1 Current Data
2.3.1.1 Background The area of interest for this study is located within the influence of the Indonesian Throughflow, a large-scale current system characterised as a series of migrating gyres and connecting jets that are steered by the continental shelf. While the mass flow is generally towards the south-west, year-round, the internal gyres generate local currents in all directions. As these gyres migrate through the area, large spatial variations in the speed and direction of currents will occur at a given location over time. Further south of the project area, the Leeuwin Current becomes the dominant large-scale current system, flowing poleward down the pressure gradient along the Western Australian coastline and past Cape Leeuwin. Offshore regions with water depths exceeding 100-200 m experience significant large-scale drift currents. These drift currents can be relatively strong (1-2 knots) and complex, manifesting as a series of eddies, meandering currents and connecting flows. These offshore drift currents also tend to persist longer (days to weeks) than tidal current flows (hours between reversals) and thus will have greater influence upon the net trajectory of plumes over time scales exceeding a few hours. On the continental shelf, in shallower waters around Scott Reef and closer to the inshore region of the Kimberley Coast, surface winds and tidal dynamics dominate over the large scale current flows (Condie & Andrewartha, 2008). In comparison to drift currents, tidal currents generate only relatively short tidal migrations (distance travelled by a parcel of water over a tidal cycle) that follow an elliptical path with a period of about 12 hours in the study region. Hence, tidal currents add variability to the longer-term drift patterns of an entrained plume. Wind shear on the water surface also generates local-scale currents that can persist for extended periods (hours to days) and result in long trajectories. Persistent winds along the mainland coast can induce Ekman transport, where surface waters move offshore and facilitate upwelling events in which cold nutrient-rich waters from the deep Indian Ocean are brought to the surface. However, due to the opposing transport of warm tropical waters by the Leeuwin Current, large-scale persistent upwelling along the Western Australian coast is suppressed. Therefore, upwelling events are sporadic, short-term and localised to areas of the coastline where the continental shelf narrows, including the area around the Capes and the Ningaloo coast (IMOS, 2015). This process is seasonal/transient and affected by the strength of the Leeuwin Current, with minimal upwelling in times with strong Leeuwin Current flow. udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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ensuring nearshore and offshore hydrodynam offshore and nearshore ensuring inter of influences cur tidal hourly the of with predictions models, global ocean from resolution daily at available circulation currents, A composi offshore areas relevant to this study this to relevant areas offshore avail not is data current measured term numerical bymodelling numerical in To appropr To current speed and direct speed and current advective mechanisms to rigorously understand patterns of potential transport from a given discharge location a given discharge from potentialtransport of patterns understand to rigorously mechanisms advective density horiz a Two mesoscale ocean curr ocean mesoscale Two 2.3.1.2.1 2.3.1.2 current The REPORT www.rpsgroup.com/mst MAW0815J in the tidal and non and tidal in the are relati with episodic associated vertical currents because reasonable considered A years. future area for study the over conditions current the of sample representative a suitably be to assumed was data The (inclusive). and Industrial Research Organisation) Research and Industrial represent upwelling upwelling represent and independent in situ observations f observations insitu andindependent Coo (Hybrid January 1994 to August 2016. From this database, three thisdatabase, From 2016. to August 1994 January are There attri principally are data BRAN the in waters shelf inner the over are represented kilom of tens circulation mesoscale of estimates provides data movement at discr movement et al. driven upwellings (Oke (Oke driven upwellings mesoscale circulation, the sea assimilates routinely BRAN ocean model, which is sponsored by the Australian Go Australian the by is sponsored which model, ocean model validation conducted by RPS, RPS, by conducted validation model over the region, at a frequency of once per day, averaged over the 24 the over averaged day, peronce of atafrequency region, overthe The BRANpr The (Oke measurements salinity and temperature many for data is a the area. BRAN affect Australia Royal (BoM), Meteorology
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Mesoscale Circulat Mesoscale Description of Mesoscale Model: BRAN Browse to NWS Project NWS to Browse several versions of the BRAN dat the BRAN of versions several iately allow for temporal and spatial variatio and spatial temporal allow for iately te modelled ocean current data product was derived by combining predictions of of mesoscale predictions derived combining was by product data current te ocean modelled ) - . rdinate Ocean Model) Ocean rdinate induced transport of of induced transport etres’ diameter, as well as connecting stream currents of similar spatial scale. Drift currents that that currents Drift scale. spatial similar of currents stream well connecting as as etres’ diameter, Additionally, edictions for drift cu drift for edictions - 50
- m/s) and vertical (1 m/s) annual and seasonal drift patterns, and the more regular variations in tide, were depicted, depicted, were in tide, variations regular and more the patterns, drift seasonal and annual in magnitude in magnitude ete depths was extract was ete depths events - tidal current data (0.5 data current tidal et al. ion over a spatial grid covering the potentialmigration grid overcovering a spatial ion ents. Depending on their local influe local on their ents. Depending ternationally recognised organisations recognised ternationally
r surface eddyfield surface , in particular , ent data sets were considered for the study: study: the for considered were sets data ent
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30 Consortium’s global ocean model, HYCOM. Base HYCOM. model, ocean global Consortium’s effects of upwelling and of effects
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- for simultaneous periods over a network of locations covering the the covering locations of network a over periods simultaneous for abase available. The latest BRAN simulation spans the period of of period the spans simulation BRAN latest The available. abase represent vertical currents between horizontal layers. This was was layers. This horizontal between vertical currents represent , 2
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2.3.1.2.2 Mesoscale Current Validation The suitability of the BRAN ocean model product was evaluated by comparing the predicted currents to those measured within the Browse project area. The validation included both quantitative and qualitative comparisons between measured and modelled data at a range of depths through the water column, at three available measurement locations shown in Figure 2.1: Browse C1-1 (three depth layers), B2-1 (eight depth layers) and G2-1 (three depth layers). Time series comparisons of modelled and measured current magnitude, direction, and U/V velocity components are presented for sites B2-1 (Figure 2.2 and Figure 2.3), C1-1 (Figure 2.4 and Figure 2.5) and G2-1 (Figure 2.6 and Figure 2.7). For the purposes of brevity and clarity, only a surface and mid-depth time series at each site was selected for presentation. The time series comparisons revealed that, at two of the sites (B2-1 and G2-1), the BRAN model offered a good match in magnitude and direction of the measured current velocity in the upper water column; however, the magnitudes of the peaks and troughs were often underpredicted at the deeper levels. At the C1-1 site, the BRAN model captured the range in current magnitude at each depth; however, the timing of peaks and troughs in the measured current velocity and direction was not well-matched. Given the location of this site in close proximity to Scott Reef, with steep gradients in the bathymetry and the relatively coarse resolution of the ocean model (relative to the tidal model), this was not unexpected. A quantitative analysis of the BRAN model’s skill at replicating the drift currents was conducted using the Index of Agreement (IOA), presented in Willmott (1981) and Willmott et al. (1985), and the Mean Absolute Error (MAE), discussed in Willmott (1982) and Willmott & Matsuura (2005). A perfect agreement can be said to exist between the model and field observations if the IOA gives a measure of one, and complete disagreement will produce an IOA measure of zero (Willmott, 1981). The MAE is simply the average of the absolute values of the differences between the observed and modelled values. The IOA and MAE values derived from comparisons of the U/V velocity components over the full measurement period at sites B2-1, C1-1 and G2-1 for all available water depths are presented in Table 2.1. The results confirm the conclusions drawn from analysis of the comparison time series plots. The IOA for both velocity components is good at sites B2-1 and G2-1 in the upper water column but reduces at deeper layers. This reflects the generally good match in the range, magnitude and direction of the measured and modelled drift currents at these sites, particularly in the upper water column. The IOA for both velocity components at site C1-1 is low, suggesting a poor agreement, reflecting the poor match in the timing of peaks and troughs in velocity observed in the time series plots. Overall, the BRAN model data offered a reasonable match to the field measurements within the Browse project area, particularly in the upper water column. Given the stochastic methodology applied in far-field modelling, the use of a ten-year hindcast of BRAN current data allowed a realistic spatial distribution of potential plume trajectories and extents to be captured in aggregate. The BRAN model was considered suitable for use in the marine dispersion modelling studies.
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Figure 2.1 Locations of the proposed Torosa FPSO and the current measurement sites used for model validation, in proximity to Scott Reef, off the Kimberley Coast of Western Australia.
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Figure 2.2 Comparisons between BRAN-predicted (red line), HYCOM-predicted (green line) and measured (blue line) non-tidal current data at site B2-1, at a depth of approximately 20 m, for the period of August 2006 to July 2007.
Figure 2.3 Comparisons between BRAN-predicted (red line), HYCOM-predicted (green line) and measured (blue line) non-tidal current data at site B2-1, at a depth of approximately 220 m, .for the period of August 2006 to July 2007 udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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Figur Figure Figure REPORT www.rpsgroup.com/mst MAW0815J e 2 2
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for the period of Aug of period the for non line) (blue measured Compariso for the period of August 2006 to July 2007 July to August2006 of period the for non line) (blue measured Comparisons between BRAN between Comparisons ns between BRAN between ns
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Quantitative Spill Risk Assessment Risk Spill Quantitative ust 2006 2006 ust - - tidal current data at site C1 site at data current tidal tidal current data at site C1 site at data current tidal to July 2007 July to - - predicted (red lin (red predicted predi cted (red line), HYCOM line), (red cted
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 . .
| 27 November 2019 November 27 e), HYCOM - - 1, at a depth of approximately 80 approximately of depth a at 1, 1, at a depth of approximately 20 approximately of depth a at 1,
- - predicted (green line) and and line) (green predicted predicted ( predicted
green line) and and line) green
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Figure 2.6 Comparisons between BRAN-predicted (red line), HYCOM-predicted (green line) and measured (blue line) non-tidal current data at site G2-1, at a depth of approximately 17 m, for the period of August 2006 to July 2007.
Figure 2.7 Comparisons between BRAN-predicted (red line), HYCOM-predicted (green line) and measured (blue line) non-tidal current data at site G2-1, at a depth of approximately 97 m, .for the period of August 2006 to July 2007 udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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Figure 2.8 Monthly current distribution (2006-2015, inclusive) derived from the BRAN database near to the Scenario 1, 2 and 3 spill locations. The colour key shows the current magnitude, the compass direction provides the direction towards which the current is flowing, and the size of the wedge gives the percentage of the record.
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REPORT www.rpsgroup.com/mst MAW0815J Figure Figure 2
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9 Browse to NWS Project NWS to Browse
wedge gives the percentage of the record the of percentage the gives wedge di locat spill 4 Scenario the to Monthly current distribution (2006 distribution current Monthly rection provides the direction towards which the current is flowing, and the and is flowing, current the which towards direction the provides rection
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Quantitative Spill Risk Assessment Risk Spill Quantitative
ion. The colour key shows the current magnitude, the compass compass the magnitude, current the shows key colour The ion. - 2015, inclusive) derived from the BRAN database near near database BRAN the from derived inclusive) 2015,
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size of the the of size Page
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2.3.1.3 Tidal Circulation
2.3.1.3.1 Description of Tidal Model: HYDROMAP As the BRAN model does not include tidal forcing, and because the data is only available at a daily frequency, a tidal model was developed for the study region using RPS’ three-dimensional hydrodynamic model, HYDROMAP. The model formulations and output (current speed, direction and sea level) of this model have been validated through field measurements around the world for more than 30 years (Isaji & Spaulding, 1984, 1986; Isaji et al., 2001; Zigic et al., 2003). HYDROMAP current data has also been widely used as input to forecasts and hindcasts of oil spill migrations in Australian waters. This modelling system forms part of the National Marine Oil Spill Contingency Plan for the Australian Maritime Safety Authority (AMSA, 2002). HYDROMAP simulates the flow of ocean currents within a model region due to forcing by astronomical tides, wind stress and bottom friction. The model employs a sophisticated dynamically nested-gridding strategy, supporting up to six levels of spatial resolution within a single domain. This allows for higher resolution of currents within areas of greater bathymetric and coastline complexity, or of particular interest to a study. The numerical solution methodology of HYDROMAP follows that of Davies (1977a, 1977b) with further developments for model efficiency by Owen (1980) and Gordon (1982). A more detailed presentation of the model can be found in Isaji & Spaulding (1984).
2.3.1.3.2 Tidal Domain Setup A HYDROMAP model was established over a domain that extended approximately 3,300 km east-west by 3,100 km north-south over the eastern Indian Ocean. The grid extends beyond Eucla in the south and beyond Bathurst Island in the north (Figure 2.10). Approximately 98,600 cells were used to define the region, with four layers of sub-gridding applied to provide variable resolution throughout the domain. The resolution at the primary level was 15 km. The finer levels were defined by subdividing these cells into 4, 16 and 64 cells, resulting in resolutions of 7.5 km, 3.75 km and 1.88 km. The finer grids were allocated in a step-wise fashion to areas where higher resolution of circulation patterns was required to resolve flows through channels, around shorelines or over more complex bathymetry. Figure 2.11 shows a zoomed subset of the hydrodynamic model grid in the Scott Reef region, showing the finer resolution grids surrounding Scott Reef, the numerous shoals and islands, and complex areas of the mainland coastline. Modelling of the tidal circulation at relatively fine scales in the topographically-complex area around Scott Reef was achieved using an additional model sub-domain with resolutions ranging down to <500 m. Major tidal channels that occur across the reef flats of North Scott Reef were represented in this model, with tidal current flows across the rest of the flats known to be minimal. High-resolution (~50 m) bathymetric data covering Scott and Seringapatam Reefs and the Brecknock, Torosa and Calliance gas fields was supplied by Woodside. Beyond these areas, bathymetric data used to define the three-dimensional shape of the study domain was extracted from the Geoscience Australia 250 m resolution bathymetry database (GA, 2009) and the CMAP electronic chart database, supplemented where necessary with manual digitisation of chart data supplied by the Australian Hydrographic Office. Depths in the domain ranged from shallow intertidal areas through to approximately 7,200 m.
2.3.1.3.3 Tidal Boundary Conditions Ocean boundary data for the HYDROMAP model was obtained from the TOPEX/Poseidon global tidal database (TPXO7.2) of satellite-measured altimetry data, which provided estimates of tidal amplitudes and phases for the eight dominant tidal constituents (designated as K2, S2, M2, N2, K1, P1, O1 and Q1) at a horizontal scale of approximately 0.25°. Using the tidal data, sea surface heights are firstly calculated along the open
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selected representative representative selected Water level Water t the observed and modelled amplitude (top) and phase (bottom) of the five dominant tidal constituents (S constituents tidal dominant the five of (bottom) phase and (top) amplitude modelled and the observed discharges considered in this study in ( this considered discharges mid w performance the model of comparisons for were suitable t performance data 1:1 line, the shows plot each line on known tidal behaviour for a wide range of tidala a wide of range for behaviour known tidal one The model skill was further evaluated through a comparison of the predicte the of comparison a through evaluated was further skill model The signal. tidal the of nature diurnal derived from an analysis of an analysis of model derived from than 120 tid than 120 locat at data level water measured from derived constituents Kostianoy over 13 y over 13 predictions of tides using the XTide database (Flater, 1998 (Flater, database XTide the using tides of predictions o the purpose For 2.3.1.3.4 this study. for accurate suitably is considered data 2,10 than more of subject the being community, oceanographic the amongst widely used been has data tidal TOPEX/Poseidon than to±5 less accurate measurements level sea taking of capable altimeters highly accurate with two satellites, equipped The Agency (NASA). Space ispr data satellite The TOPEX/Poseidon REPORT www.rpsgroup.com/mst MAW0815J N hat are not sufficiently resolved hat are resolved not sufficiently 2 , K - - . Note that the data is generally closely aligned to the 1:1 line demonstrati line 1:1 the to aligned closely generally is data the that Note . to month period (January 2018). All comparisons show that the model the that show All comparisons 2018). (January period month 1
- and O and northwest regions of the Western A the of northwest regions Western
|
ea Tidal Elevation Validation Browse to NWS Project NWS to Browse et al. et al stations within the HYDROMAP model domain; domain; model HYDROMAP within the stations al rs (1992 rs ime series for the for series ime . 1
) for all relevant stations within the model domain (>80) are present are (>80) domain model the within stations relevant all for ) , 2003; Yaremchuk & Tangdong, 2004; Qiu & Chen, 2010). As such, the TOPEX/Poseidon tidal tidal TOPEX/Poseidon the such, As 2010). Chen, & Qiu 2004; & Tangdong, Yaremchuk 2003; , 0 research publications (e.g. Anderse (e.g. publications 0 research f verification of the tidal predictions, the model output w output the model predictions, the tidal of verification f - 2005). In total, these satellites carried out more than 62,000 orbits of the planet. The The the planet. orbits of than 62,000 more out carried satellites In total, these 2005). subset of the available tidal station validation data is data validation station tidal the available of subset
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Quantitative Spill Risk Assessment Risk Spill Quantitative
selected
by this large this by - predicted time predicted which would indicate a perfect match between the modelled and observed observed and modelled the between match aperfect indicate would which Figure Figure
subset of t of subset cm, measured oceanic surface elevations (a surface oceanic measured cm,
oduced, and quality controlled by the by quality controlled and oduced, 2 ustralian coastline, encompassing encompassing coastline, ustralian - . 10 scale ocean model. More than 80 stations along the coastli the along stations 80 than More model. ocean scale mplitudes and clearly represents the varying diurnal and semi diurnal varying the and represents clearly mplitudes
a series at each of the tidal station locations. Scatter plots of of Scatterplots locations. station the tidal at each of series
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ith the observed data. These stations covered the the stationscovered These data. observed the ith | ). The XTide database contains har contains database XTide The ). 2 27 November 2019 November 27 ions around the world. Overall, there are more more are there Overall, world. the around ions . 1 however, some of these are located in areas areas in located ofare these some however, 1 ). ). For the purposes of brevity of clarity, and purposes the For
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U S National Atmospheric and and S Atmospheric National s a very good match to the to the match good very a s the locales of the marine the marine of the locales ed in in ed 2 . served tidal constituents, constituents, tidal served nd the resultant tides) for for tides) resultant nd the 12 and and Figur . Figu
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Figure 2.10 Hydrodynamic model grid (blue wire mesh) used to generate the tidal currents, showing the full domain in context with the continental land mass and the locations available for tidal comparisons (red and blue labelled dots). Higher-resolution areas are indicated by the denser mesh zones.
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Figure 2.11 Zoomed subset of the hydrodynamic model grid (blue wire mesh) for the Scott Reef area, showing the locations available for tidal comparisons (red and blue labelled dots). Higher-resolution areas are indicated by the denser mesh zones.
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Figure 2.12 Comparisons between the predicted (blue line) and observed (red line) surface elevation variations at five locations in the north-east of the tidal model domain for January 2018.
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Figure 2.13 Comparisons between the predicted (blue line) and observed (red line) surface elevation variations at five locations in the north-east of the tidal model domain for January 2018.
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Figure 2.14 Comparisons between modelled and observed tidal constituent amplitudes (top) and
phases (bottom) at all relevant stations (>80) in the HYDROMAP model domain. The red line indicates a 1:1 correlation between the modelled and observed data. udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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regime. current tidal the in variation considerable to subject be would steering of the tidal flow direction around the reef. Maximum speeds at the Scena at speeds the Maximum reef. the around direction flow tidal the of steering released oil due to the tidal tidal to the due oil released anyof behaviour initial expected the into an insight provides locations spill nearthe data current extracted The a along and approximately 0.25 approximately The data indicates cyclical tidal flow directi tidal flow cyclical indicates data The flows. current the which direction towards is the direction current defining for that convention the data Figure 2.3.1.3.5 REPORT www.rpsgroup.com/mst MAW0815J
points closest to closest points 2
. 15 |
Tidal CurrentsTidalat the Browse to NWS Project NWS to Browse to
north Figure Figure - south axis at the Scenario 1 site which is relatively close to Scott Reef and experiences experiences and Reef Scott to close is relatively which site 1 Scenario the at axis south - 0.3 2 the spill locations for Scenario 1, Scenarios 2 and 3, and Scenario 4, respectively. Note Note 4, respectively. Scenario and 3, and 2 Scenarios 1, Scenario for locations spill the . 17 m/s, with peak speeds at the Scenario 4 site being around 0.4 around being 4 site Scenario at speeds the peak with m/s,
show the monthly distributions of current speeds and directions for the HYDROMAP the HYDROMAP for and speeds of directions current distributions theshow monthly currents alone. Oil alone. currents -
Quantitative Spill Risk Assessment Risk Spill Quantitative
S p i l l
Locations ons along a northwe a along ons
moving beyond the release sites, particularly towards the coast, coast, the towards particularly sites, release the beyond moving
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 Novembe st - southeast axis at the Scenario 2 Scenario the at axis southeast
r 2019
m/s. rio 1 to 3 sites ar 3 sites 1 to rio
to
4 sites, sites, 4 Page
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Figure 2.15 Monthly current distribution (2006-2015, inclusive) derived from the HYDROMAP database near to the Scenario 1 spill location. The colour key shows the current magnitude, the compass direction provides the direction towards which the current is flowing, and the size of the wedge gives the percentage of the record.
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REPORT www.rpsgroup.com/mst MAW0815J Figure 2
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16 Browse to NWS Project NWS to Browse
Monthly current distribution (2006 distribution current Monthly the compass direction provides the dire the provides direction compass the ma current the key shows colour The 3 spill locations. and 2 Scenario near the to size of the wedge gives wedge the of size
-
Quantitative Spill Risk Assessment Risk Spill Quantitative
the percentage of the record the of percentage the - 2015, inclusive) derived from the HYDROMAP database database HYDROMAP the from derived inclusive) 2015,
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 ction towards which the current is flowing, and the the current is flowing, which towards ction
| 27 November 2019 November 27 .
gnitude, Page
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Figure 2.17 Monthly current distribution (2006-2015, inclusive) derived from the HYDROMAP database near to the Scenario 4 spill location. The colour key shows the current magnitude, the compass direction provides the direction towards which the current is flowing, and the size of the wedge gives the percentage of the record.
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the ne surface slicks in the absence of any current effects. No effects. current any of absence in the slicks surface acting wind the to due trajectories initial possible suggests location spill the near data wind extracted The near all westerly directions most prominent between September an September prominent between most directions westerly spill site, easterly/south sites between directions easterly predominantly indicates wind data The for defining wind direction is the direction from whichwind the from the direction is direction wind defining for points closest to the spill locations for Scenarios 1 t Scenarios for locations spill to the closest points Figure be a suitably representative sample of the wind conditions over the study area for area for study the over wind the conditions of sample representative be a suitably dat theas current temporal coverage the same for domain directio and speed wind of series Time 1 and resolution 0.25° at is available winds, data gridded The atmosphere. and land oceans, Earth’s the between interaction N via the (NCEP), Prediction Environmental for theCenter National from sourced fields wind spatial by provided Environmental Sciences (CIR Sciences Environmental acco To 2.3.2 REPORT www.rpsgroup.com/mst MAW0815J Saha (CFSR; Reanalysis ational Oceanic and Atmospheric Administ Atmospheric and Oceanic ational , and wester , and t result of a combination of the prevailing wind and current vectors acting at a given time and location. time a given at acting vectors current and wind the prevailing of a combination of t result
2 spill unt for the influence of the wind onwind surface the of the influence unt for
. 18 |
Wind Data Wind Browse to NWS Project NWS to Browse
and sites Figure Figure ly/south
vary in the range range in the vary - 2 eas - . 19 westerly directions dominating in the in the dominating directions westerly
et al. et -
terly directions are most common between April and August, with southerly and and with southerly August, and between April common most are terly directions
Quantitative Spill Risk Assessment Risk Spill Quantitative s how the monthly distribution monthly how the ES) Climate Diagnostics Center (CDC). The NCEP Climate Forecast System System Forecast Climate NCEP The Center(CDC). Diagnostics Climate ES) , 2010) is a fully isa , 2010)
- 5.9 6.5 n were extracted from the CFSR database database the CFSR from extracted were n
m/s, with year with m/s, - hourly time intervals. time hourly ration (NOAA) and Cooperative Institute for Research in in Research for Institute Cooperative and (NOAA) ration - coupled, data coupled, - o 3 bound oil slicks, representation of th of representation slicks, oil bound
|
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES and Scenario 4, respectively and Scenario Rev 4 te that the actual trajectories of surface slicks will be will be slicks surface of trajectories actual the that te - round maximum sp maximum round a (2006 s
of wind speed of | d March. d March. 27 November 2019 November 27
blows. - October assimilative hindcast model representing model hindcast assimilative
- 2015, inclusive). The data was assumed to was data assumed The inclusive). 2015, May
Average wind speeds across the year the across speeds wind Average
to F
and and s
ebruary period. period. ebruary and direction and eeds of of eeds July
future years. future at the Scenario 1 to 3 spill spill to 3 1 Scenario at the for all nodes in the model model the in nodes all for . Note that the convention convention the that . Note output, including surface surface including output, 2 5 e wind was conditions .5 s -
29. for the CFSR data data the CFSR for At the Scenario 4 4 Scenario Atthe 4
m/s.
Page
the the on on
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Figure 2.18 Monthly wind distribution (2006-2015, inclusive) derived from the CFSR database near to the Scenario 1, 2 and 3 spill locations. The colour key shows the wind magnitude, the compass direction provides the direction from which the wind is blowing, and the size of the wedge gives the percentage of the record.
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REPORT www.rpsgroup.com/mst MAW0815J
Figure Figure 2
. |
19 Browse to NWS Project NWS to Browse
gives the percentage of the record the of percentage the gives wind the which from direction the provides direction 4 Scenario the (2006 distribution wind Monthly
-
Quantitative Spill Risk Asses Risk Spill Quantitative
spill location. The colour key shows the the mag wind keycolour shows The spill location.
- 2015, inclusive) derived from the CFSR database near to to near database CFSR the from derived inclusive) 2015, sment .
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 November 2019 November 27 is blowing, and the size of the wedge wedge the of size the and is blowing,
nitude, the compass compass the nitude, Page
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2.3.3 Water Temperature and Salinity Data The World Ocean Atlas 2013 (WOA13) is provided by NOAA and is a hindcast model of the climatological fields of in situ temperature, salinity, and a number of additional variables (NOAA, 2013a). WOA13 has a 0.25° resolution and has standard depth levels ranging from the water surface to 5,500 m (Locarnini et al., 2013; Zweng et al., 2013). Vertical profiles of sea temperature and salinity at the spill locations were retrieved from a data point in the WOA13 database near the Torosa FPSO location (13° 52' 30" S, 121° 52' 30" E), with monthly averages used as input to both SIMAP and OILMAP. Figure 2.20 shows the variation in water temperature and salinity both seasonally and over depth. During the period from May to September, surface mixing is evident over the upper 50-100 m of the water column (where the depth is approximately 300 m at this location). In contrast, during the period from October to April, the surface mixed layer is shallower, indicating stronger thermal stratification. The average temperature over the upper 300 m of the water column varies between approximately 10-30 °C across the year, while the average salinity over this depth range varies between approximately 33.8-34.8 PSU year-round.
2.3.4 Dispersion A horizontal dispersion coefficient of 10 m2/s was used to account for dispersive processes acting at the surface that are below the scale of resolution of the input current field, based on typical values for coastal waters (Okubo, 1971). Dispersion rates within the water column (applicable for entrained and dissolved plumes of hydrocarbons) were specified at 1 m2/s, based on empirical data for the dispersion of hydrocarbon plumes over the North West Shelf (King & McAllister, 1998).
2.3.5 Replication Multiple replicate simulations were completed for the defined scenarios to account for trends and variations in the trajectory and weathering of spilled oil, with an even number of replicates completed using samples of metocean data that commenced within each month. For Scenario 1, a total of 100 replicate simulations were run over an annual period; for Scenarios 2-4, a total of 200 replicate simulations were run over an annual period.
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Figure Figure REPORT www.rpsgroup.com/mst MAW0815J 2
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Browse to NWS Project NWS to Browse
surface near the Torosa FPSO location location FPSO near Torosa the line salinity (green and line) (blue Temperature .
-
Quantitative Spill Risk Assessment Risk Spill Quantitative ( 13°
52' |
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
30"
|
S, 121° 27 November 2019 November 27 ) profiles derived from the WOA13 database database WOA13 the from derived profiles )
52'
30"
E ).
Depth of 0 of Depth
m is t m he water water he Page
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2.3.6 Contact Thresholds
2.3.6.1 Overview The SIMAP model will track oil concentrations to very low levels. Hence, it is useful to define meaningful threshold concentrations for the recording of contact by oil components and determining the probability of exposure at a location (calculated from the number of replicate simulations in which this contact occurred). The judgement of meaningful levels is complicated and will depend upon the mode of action, sensitivity of the biota contacted, the duration of the contact and the particular toxicity of the compounds that are represented in the oil. The latter factor is further complicated by the change in the composition of an oil type over time due to weathering processes. Without specific testing of the oil types, at different states of weathering against a wide range of the potential local receptors, such considerations are beyond the scope of this investigation. For this case, thresholds for floating, entrained and dissolved aromatic hydrocarbons were specified by Woodside for use in defining the potential zone of influence of the spill event. These thresholds are summarised in Table 2.2 and discussed afterwards.
Table 2.2 Summary of the thresholds applied in this study.
Dissolved Aromatic Floating Oil Concentration Shoreline Oil Entrained Oil Hydrocarbon (g/m2) Concentration (g/m2) Concentration (ppb) Concentration (ppb)
1 100 (Scenarios 1-3) 50 (Scenarios 1-3) 100 10 500 (Scenario 4) 500 (Scenario 4)
2.3.6.2 Floating Oil Floating oil concentrations are relevant to describing the risks of oil coating emergent reefs, vegetation in the littoral zone and shoreline habitats, as well as the risk to wildlife found on the water surface, such as marine mammals, reptiles and birds. Estimates for the minimal thickness of floating oil that might result in harm to seabirds through ingestion from preening of contaminated feathers, or the loss of the thermal protection of their feathers, has been estimated by different researchers at approximately 10 g/m2 (French-McCay, 2009) to 25 g/m2 (Scholten et al., 1996; Koops et al., 2004). Hence, the 10 g/m2 threshold is likely to be moderately conservative in terms of environmental harm for effects on seabirds, for example. The lower threshold of 1 g/m2 is likely to be an indicator of where there is a visual presence of an oil slick that may trigger social and economic impacts but where there is little potential for environmental impact. It is important to note that real spill events generate surface slicks that break up into multiple patches separated by areas of open water. Concentrations calculated and presented in this study represent necessary areal averaging over discrete model cells, and therefore indicate the potential for both higher and lower relative concentrations in the surrounding space.
2.3.6.3 Shoreline Oil Shoreline oil concentrations are relevant to describing the risks of oil contact/stranding on shorelines and beaches. French et al. (1996) and French-McCay (2009) have defined an oil exposure threshold of 100 g/m2 for shorebirds and wildlife (furbearing aquatic mammals and marine reptiles) on or along the shore, which is based on studies for sub-lethal and lethal impacts. The 100 g/m2 threshold has been used in previous environmental risk assessment studies (French-McCay et al., 2004, 2011, 2012; French-McCay, 2003; NOAA, 2013b). This threshold is also recommended in the Australian Maritime Safety Authority’s foreshore udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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short exposure durations. exposure short French, hydrocarb toxic of concentrations typically can tolerate organisms marine because and conditions, environmental habitats affected by the dy the by affected habitats passing over a fixed habitat (such as a reef), due to fluctuati due a reef), as (such habitat a fixed over passing at defined As indicat As As indicat As mixture. For mortality of molluscs, reported LC molluscs, of For mortality mixture. test the on depending variation wide showed 2005) (NRC, studies laboratory in after 24 after 500 A review of the concentrations of phy of concentrations the of A review 2005). (NRC, or accidentalingestion surfaces, coati physical through example, for with contact organisms; direct through demonstrated an Physical a shoreline). against waves co elevated generate to thehave potential exert for mechanisms p of number a oil presents Entrained depth. at discharge a pressurised by subsea be generated natu by remediated best For Scenario 1, Scenario For hydrocarbons polyaromatic NR 2000; o time with or concentration with exposure isadditive, increasing effect This organisms. into uptake resulting from effect a narcotic is hydrocarbons soluble of action of mode The 2.3.6.5 wavewinddue and to surface slicks from watercolumn the into Oilbe can entrained 2.3.6.4 acc the as guide assessment REPORT www.rpsgroup.com/mst MAW0815J Condensate of Characteristics 2.3.7.1 2.3.7 e (subsea). Condensate Torosa Torosa Condensate (surface). The formulation used in the in used formulation The (surface). Condensate Torosa subsea Woodside Woodside with 96 with xposure. Wider exposure sensitivities are displayed by species of crustaceans (100 crustaceans of by species displayed are sensitivities exposure xposure. Wider
ppb. Th ppb.
-
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2000), the 2000),
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. The formulation used in the se the in used formulation . The 500
ral coastal processes alone coastal processes ral
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ppb. Because exposure times may be be may times exposure Because ppb. unstabi Quantitative Spill Risk Assessment Risk Spill Quantitative eptable minimum thickness that does not inhibit the potential for recovery and is and recovery for potential the inhibit not does that thickness eptable minimum
s
rticularly relevant for short duration (acute) exposure to organisms or fixedor to organisms exposure (acute) duration short for relevant particularly
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s
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- for concentrations of dissolved aromatic w hydrocarbons aromatic of dissolved concentrations for soluble fraction is the best predictor of the toxicity of the oil. the of the toxicity of predictor best is the fraction soluble Condensate mixture Condensate 50
values range from 500 range from values (AMSA, 2015). (AMSA, longside characteristics for marine diesel in diesel for marine characteristics longside
|
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Rev 4 (pre by the FPSO the by a- surface release phase is referred to as to as referred is phase release surface subsea
- | processed condensate) processed 27 November 2019 November 27 as been demonstrated to have harmful effects harmful tohave as demonstrated been ons in the plume locationons in wi the plume release phase phase release
short (<1 short )
w were specified from data supplied by by data supplied from were specified as trained oil droplets have also been been also have droplets oil trained
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is referred to as referred is organisms and the initial oil oil initial and the organisms to 2,000 ere 50
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Page . ppm) ppm) 3 hour hour
ppb ppb . ere
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Table 2.3 Characteristics of the oil types used in the modelling of Scenarios 1-4.
Semi- Low Volatile Residual Aromatics Component Volatile Volatility Density Viscosity (%) (%) (%) Oil Type (%) (%) (g/cm3) (cP) Boiling point <180 180 - 265 265 - 380 >380 Of whole oil (°C) C4 to C10 C11 to C15 C16 to C20 >C20 <380 BP
Unstabilised % of total 14.5 39.9 20.7 24.9 26.2 Torosa 0.780 1.092 Condensate at 25 °C at 20 °C 2.5 8.8 14.9 - - (subsea) % aromatics
Unstabilised % of total 1.0 15.5 32.8 50.7 26.9 Torosa 0.813 2.519 Condensate at 25 °C at 25 °C 0.2 3.1 23.6 - - (surface) % aromatics
Stabilised % of total 57.0 21.0 8.0 14.0 19.6 0.780 1.092 Torosa at 20 °C at 20 °C Condensate % aromatics 10.3 4.3 5.0 - -
% of total 6.0 34.6 54.4 5.0 3.0 0.829 4.000 Marine Diesel at 25 °C at 25 °C % aromatics 1.8 1.0 0.2 - -
The boiling points are dictated by the length of the carbon chains, with the longer and more complex compounds having a higher boiling point, and therefore lower volatility and evaporation rate. The aromatic components within the volatile to low-volatility range are also soluble (with decreasing solubility following decreasing volatility) and will dissolve across the oil-water interface. The rate of dissolution will increase with increase in surface area. Hence, dissolution rates will be higher under discharge conditions that generate smaller oil droplets. Atmospheric weathering will commence if and when oil droplets float to the water surface. Typical evaporation times once the hydrocarbons reach the surface and are exposed to the atmosphere are: • Up to 12 hours for the C4 to C10 compounds (or less than 180 °C BP); • Up to 24 hours for the C11 to C15 compounds (180-265 °C BP); • Several days for the C16 to C20 compounds (265-380 °C BP); and • Not applicable for the residual compounds (BP > 380 °C), which will resist evaporation, persist in the marine environment for longer periods, and be subject to relatively slow degradation. The actual fate of released oil in the marine environment will depend greatly on the amount of oil that reaches the surface, either through the initial release or by rising after discharge in the water column.
2.3.7.2 Unstabilised Torosa Condensate (Surface/Subsea) Two formulations of unstabilised Torosa Condensate (pre-processed condensate) were used in Scenario 1. Unstabilised Torosa Condensate (surface) contains a high proportion (50.7% by mass) of hydrocarbon compounds that will not evaporate at atmospheric temperatures; this proportion is lower but still significant (24.9%) for unstabilised Torosa Condensate (subsea). These compounds will persist in the marine environment. The unweathered mixtures of unstabilised Torosa Condensate (surface) and unstabilised Torosa Condensate (subsea) have dynamic viscosities of 0.81 cP and 0.78 cP, respectively. The pour point of the whole oils (<15 °C) ensures that they will remain in a liquid state over the annual temperature range observed in the Timor Sea. udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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compounds will evaporate slow willevaporate compounds significant proportion (surface, 23.6%; subsea, 14.9%) inC16 the 14.9%) subsea, 23.6%; (surface, proportion significant Soluble aromatic hydrocarbons contribute approximately 26.9% and 26.2% by mass of t of mass by 26.2% and 26.9% approximately contribute hydrocarbons Soluble aromatic mixtures, remaining S Condensate (surface) and (surface) Condensate water to form water to (0.6 content low whole asphaltene have oils The they as weather orsink areunlikelyto solidify mixtures and evaporation through compounds (265 the first 24 thefirst has the capacity to evaporate within the first 12 within the first evaporate thehas to capacity the potential for dissolution of a proportion of them into the water. intothe them of a proportion of dissolution for the potential proportion (10.3%) in the C4 the in (10.3%) proportion con hydrocarbons aromatic Soluble over several days days over several to form water to form p a low indicating (0.66%), content asphaltene low wholeoil has The m the oil, remaining the of density in increase an in will result dissolution and evaporation through compounds re boiling lower the of evaporation Selective days (265 Approximately 5% of the oil is shown to be persistent. The aromatic content of the the content of aromatic The be persistent. to is shown oil the 5% of Approximately 15.5% could evaporate within the first 24 first within the evaporate 15.5% could Condensate (surface) mass has the capaci the has mass (surface) Condensate (180 24 within thefirst evaporate 12 first the within evaporate to capacity the has mass Condensate with increase will rates Evaporation temperature atmospheric at volatilities and points boiling of range wide a have that hydrocarbons of iscomposed The mixture wi rates Evaporation to the atmosphere. on rates exposure at different will to whichevaporate and begin temperatures, atmospheric Stabili 2.3.7.3 hydrocar of composed are The mixtures REPORT www.rpsgroup.com/mst MAW0815J hours 12 first the within evaporate low pro Marine 2.3.7.4 3. 2 and that it 0.78 of viscosity dynamic a has mixture unweathered The environment. temperatures. atatmospheric will evaporate not that compounds elective evaporation of the lower boiling lower the of evaporation elective ixture is unlikely to solidify or sink a or sink ixture isto unlikely solidify maining mixture, including anmaining including increase in mixture, the viscosity pourpoint. Although and re
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(BP tribute approximately 19.6% by mass of t by 19.6% mass approximately tribute 265 4. s it weathers. its
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ontains a moderate proportion (14.0% by (14.0% proportion moderate a ontains < ty to evaporate within the first 12 first the within evaporate to ty
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265 bons. These compounds will evaporate rapidly, reducing reducing rapidly, evaporate will compounds These bons.
°C
| . PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
°C); and a further 8.0% co 8.0% a further and °C); < aporate over several daysseveral (265 over aporate
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Torosa Condensate (sub Condensate Torosa |
180 27 November 2019 November 27
<
different rates on exposure to the atmosphere. to the atmosphere. on rates exposure different 265
.7% could evaporate over several days days several over evaporate could .7%
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d 37
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If released in the marine environment and in contact with the atmosphere (i.e. surface spill), approximately 41% by mass of this oil is predicted to evaporate over the first couple of days depending upon the prevailing conditions, with further evaporation slowing over time. The heavier (low volatility) components of the oil have a tendency to entrain into the upper water column due to wind-generated waves, but can subsequently resurface if wind-waves abate. Therefore, the heavier components of this oil can remain entrained or on the sea surface for an extended period, with associated potential for dissolution of the soluble aromatic fraction.
2.3.8 Weathering Characteristics
2.3.8.1 Overview A series of model weather tests were conducted to illustrate the potential behaviour of unstabilised Torosa Condensate (surface and subsea), stabilised Torosa Condensate and marine diesel when exposed to idealised and representative environmental conditions: • Instantaneous release (1-hour discharge) onto the water surface at a discharge rate of 50 m3/hr under calm wind conditions (constant 5 knots), assuming low seasonal water temperature (27 °C) and average air temperature (25 °C). Slick also subject to ambient tidal and drift currents. • Instantaneous release (1-hour discharge) onto the water surface at a discharge rate of 50 m3/hr under variable wind conditions (4-19 knots, drawn from representative data files), assuming low seasonal water temperature (27 °C) and average air temperature (25 °C). Slick also subject to ambient tidal and drift currents. The first case is indicative of cumulative weathering rates under calm conditions that would not generate entrainment, while the second case may represent conditions that could cause a minor degree of entrainment. Both scenarios provide examples of potential behaviour during periods of a spill event, once the oil reaches the surface.
2.3.8.2 Unstabilised Torosa Condensate (Surface/Subsea) Weathering results are presented for the unstabilised Torosa Condensate mixture that was used in the modelling of the sea-surface release phase, referred to as unstabilised Torosa Condensate (surface), and for the unstabilised Torosa Condensate mixture that was used in the modelling of the subsea release phase, referred to as unstabilised Torosa Condensate (subsea). The results for the constant-wind case indicate that a significant proportion of unstabilised Torosa Condensate (surface, Figure 2.21; subsea, Figure 2.23) will tend to persist on the sea surface (46% and 15%, respectively, after 7 days) during calm wind conditions, with low levels of entrainment and around 40% (surface) and 70% (subsea) of the spilled volume expected to evaporate within the first 24 hours under light winds. The results for the variable-wind case (surface, Figure 2.22; subsea, Figure 2.24) indicate that the wind conditions will have a large impact on the proportion of unstabilised Torosa Condensate that remains afloat, with very little oil mass predicted to persist on the sea surface (<2% after 24 hours). This is largely due to the higher wind speeds within this test case (>5 knots) generating significant entrainment events, with almost all of the oil mass becoming entrained shortly after release. The higher proportion of entrained oil predicted in the variable-wind case also results in a larger proportion of the oil dissolving: 30% (surface) and 16% (subsea) after 7 days compared with <6% under calm conditions. The evaporation rate observed in the first 24 hours is similar in both weathering tests; however, as the wind speed increases in the variable-wind case, increased entrainment reduces the proportion of oil available for evaporation, resulting in around 17% (surface) and 50% (subsea) of the spill volume expected to evaporate after 7 days as compared to 39% (surface) and 69% (subsea) in the lower-wind case. Biological and photochemical degradation is predicted to contribute to the decay of the floating slicks in both weathering cases, with increased levels of entrainment and dissolution in the variable-wind case resulting in a higher proportion of oil decaying: 25% (surface) and 16% (subsea) after 7 days compared with 12% (surface) and 6% (subsea) under calm conditions. udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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slicks to reduce concentrations below the thresholds considered in th considered thresholds the below to concentrations reduce slicks long weatheringlong duration wi Under calm conditions where entrainment is restricted, a proportion of the spilled mass of mass spilled the of proportion a is restricted, entrainment where conditions Under calm higher proportion of oildecayin of proportion higher of levels with increased cases, weathering photoc and Biological lower the 84% in few months, with the entrained oil entrained with the fewmonths, components circumstan In these watersurface. the on floating to remain expected willbe Condensate evaporation, resulting in around inaround resulting evaporation, speed inc 24 first the in observed rate evaporation The conditio calm under <2% hydrocarbons will decay and/or evaporate over time scales of several of scales time over evaporate and/or will decay hydrocarbons it to re for oil tendency and the entrained of large proportion and day per ~0.2% rate of at anapproximate photo variable the in entrainment of level increased The entrained beneath the surface under conditions that generate wind waves (approxima waves wind generate that conditions under surface the beneath entrained variable entrained of proportion higher The release. after shortly entrained becoming oil mass (>5 case test this within speeds wind surf sea toonpersist the predicted oil mass littlevery on the of proportion impact will have a large conditions small proportion of the oil floating on the wate on the the oil floating of proportion small 24 v the spilled andof around 80% entrainment of levels negligible of the oil mass is forecast to have entrained have to isforecast oil mass the of the into diesel Condensate will tend to persist on persist to willtend Condensate Under the variable Underthe be su will then they and slow significantly, will the compounds residual of Evaporation boiling points. with higher compounds remaining oil on t oilon remaining conditio Under these calm within hours. to24 evaporate the oil ispredicted 45%of The results for the constant for results The 2.3.8.3 a prop is restricted, entrainment where conditions Under calm REPORT www.rpsgroup.com/mst MAW0815J the constant for forecast balance mass The 2.3.8.4 components circu In these watersurface. the on floating to remain expected willbe Condensate long weatheringdurati long This scales. time similar over degradation through concentration oilreducing entrained with the fewmonths, slicks to reduce concentrations b to concentrations reduce slicks
hours under light winds. The results for the variable the for results The winds. light under hours chemical degradation, where the decay of the floating slicks and oil droplets in the water column occurs occurs water column in the droplets and oil slicks floating the of decay where the degradation, chemical -
wind case also results in a larger proportion of the oil dissolving: 11% after 7 after 11% the oil dissolving: of proportion a larger in results wind also case |
reases in the variable the in reases Stabilised Stabilised Marine Diesel Marine Browse to NWS Project NWS to Browse
of the remaining floating oil will evaporate and/or degrade over time scales of several weeks to a a to weeks several of scales time over degrade and/or will evaporate oil floating remaining the of of the remaining floating oil will evaporate and/or degrade over time scales of several weeks to weeks several of scales time over degrade and/or will evaporate oil floating remaining the of
bject to more gradual decay through biolo through decay gradual more to bject water column is in water column - wind case. he water surface will weather at a slower rate due to being comprised of the longe of comprised being to due rate a slower at weather will surface water he - rate of 1.8% per day with an accumulated total of ~13% after 7 days, in comparison to a to in 7 days,comparison after ~13% total of an accumulated with per day 1.8% rate of wind case ( windcase hemical degradation is predicted to contribute to the decay of the floating slicks in both the floating slicks of decay to to the contribute is predicted degradation hemical on will extend the area o area the will extend on Torosa ns.
- ll extend the area of area ll the extend
an accumulated tota an accumulated
Quantitative Spill Risk Assessment Risk Spill Quantitative - wind case ( case wind g: 8% after 7 8%after g: Figure - wind case, increased entrainment reduces the proportion of oil available for for available oil of proportion the reduces entrainment increased wind case, 73% of the spill volume expected to evaporate after 7 after expected to evaporate volume the spill of 73% elow the thresholds considered in study. this considered thresholds the elow
dicated to be significant. Approximately 24 hours after the spill, around 45% the45% spill, after around 24 hours Approximately to be significant. dicated Condensate
reducing concentration through degradation over similar time scales. This This scales. time similar over degradation through concentration reducing
the sea surface (6% after 7 after (6% surface sea the
knots) generating significant entrainment events, with a with events, entrainment significant generating knots) 2 . 28 Figure
- entrainment and dissolution in the variable in the and dissolution entrainment ), where the winds are of greater strength, entrainment of of marine entrainment greater strength, windsof are wherethe ), wind case ( case wind
days co days and a further 35% is forecast to have evaporated, leaving only a only leaving evaporated, have to is forecast 35% further a and
hours is similar in both weathering tests; inhowever, is similar weatheringhours tests; both r surface Th (<1%). surface r f potential effect, requiring the break requiring the effect, potential f
l of 1.5% after 7 days in the constant the in 7 days after 1.5% lof potential effect, requiring the break requiring the effect, potential -
2 wind case will result in a higher percentage of b of percentage higher a in will result case wind . ) indicate that a small proportion of of proportion small a indicate that 25) mpared with 3% under calm conditions. calm under 3% with mpared ace (<1% after 24 (<1%after ace
| Figure Figure PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES stabilised Rev 4 gical and photochemical processes. photochemical and gical -
wind case ( wind case | main mixed in the water column, the remaining the remaining water column, in the mixed main 2 27 November 2019 November 27 ortion of the spilled mass of of mass the spilled of ortion . ) for marine diesel shows that approximately approximately that dieselshows marine for 27)
olume expected to evaporate within the first within thefirst to evaporate expected olume Torosa
e residual compounds will tend to remain to willremain tend e compounds residual days) during calm wind co calm during days) is study. is
rs). This is largely due to the higher higher islargely to the due This hours).
Figure Figure
Condensate that remains afloat, with afloat, with remains that Condensate weeks to a few mon to a few weeks
2 . ) indicate that the wind wind the that indicate 26) - - up and dispersion of the the of dispersion up and up and dispersion of the the of dispersion up and - tely >6 wind case resulting in a in a resulting windcase - ns the majority of the the of thens majority
wind case. Given the the Given windcase. days as compared to to compared as days
days compared with with days compared
unstabilised oil predicted inoil predicted the stabilised
stab
mstances, some mstances,
m/s). lmost all of the the all of lmost ths. This long long This ths. nditions, with with nditions, ilised ilised iological and and iological as the wind wind the as
ces, some ces, Torosa Torosa Torosa Torosa r - Page chain chain
a 39
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weathering duration will extend the area of potential effect, requiring the break-up and dispersion of the slicks and droplets to reduce concentrations below the thresholds considered in this study.
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REPORT www.rpsgroup.com/mst MAW0815J Figure Figure 2
. |
21 Browse to NWS Project NWS to Browse
27 as one a the weatherin the panel), (bottom volume and panel) (middle proportion as representing, plot balance Mass °C water temperature and 25 and temperature water °C - off release (50 release off
g of g of -
Quantitative Spill Risk Assessment Risk Spill Quantitative unstabilised unstabilised
m 3
over 1 ho over 1 Torosa Condensate (surface) spilled onto the water surface surface water the onto spilled (surface) Condensate Torosa
°C air temperature °C air
ur) and subject to to subject and ur) | PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 November 2019 November 27 .
a constant 5 constant a
kn (2.6 kn
m/s) wind at at wind m/s) Page
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Figure 2.22 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of unstabilised Torosa Condensate (surface) spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature.
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Figure Figure REPORT www.rpsgroup.com/mst MAW0815J 2
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27 as one a of weathering the panel), (bottom volume and panel) (middle proportion as representing, plot balance Mass °C water temperature and 25 and temperature water °C
Project - off release (50 release off
-
Quantitative Spill Risk Assessment Risk Spill Quantitative unstabilised unstabilised
m 3
over 1 hour) and subject to a constant 5 constant a to subject and hour) 1 over T
°C air temperature °C air orosa Condensate (subsea) (subsea) orosa Condensate
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 November 2019 November 27 .
spilled onto the water surface surface water the onto spilled
kn (2.6 kn
m/s) wind at at wind m/s) Page
43
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Figure 2.24 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of unstabilised Torosa Condensate (subsea) spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature.
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Figure Figure
REPORT www.rpsgroup.com/mst MAW0815J 2
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off release (50 release off the weathering of weathering the plot balance Mass temper ature and 25 and ature
-
Quantitative Spill Risk Assessment Risk Spill Quantitative m 3
over 1 hour) and subject to a constant 5 a constant to subject and hour) 1 over stabilised
representing, as proportion (middle panel) and volume (bottom panel), panel), (bottom volume and panel) (middle proportion as representing,
°C air temperature air °C
Torosa
Condensate spille Condensate
| .
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 November 2019 November 27 d onto the water surfacea water the onto d
kn (2.6 kn
m/s) wind at 27 at wind m/s)
°C water water °C s aone Page
45 -
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Figure 2.26 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of stabilised Torosa Condensate spilled onto the water surface as a one- off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature.
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Figure Figure REPORT www.rpsgroup.com/mst MAW0815J
2
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25 over the the panel) (middle proportion as representing, plot balance Mass °C air temperature air °C weathering of marine diesel spilled onto the water surface as aone as surface water the onto spilled diesel marine of weathering 1 hour) and subject to a constant 5 a constant to subject and 1 hour)
-
Quantitative Spill Risk Assessment Risk Spill Quantitative
.
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
kn (2.6
| 27 November 2019 November 27
m/s) wind at 27 wind m/s)
and volume (bottom panel), panel), (bottom volume and
°C water temperature and and temperature water °C - off release (50 release off Page
m
47 3
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Figure 2.28 Mass balance plot representing, as proportion (middle panel) and volume (bottom panel), the weathering of marine diesel spilled onto the water surface as a one-off release (50 m3 over 1 hour) and subject to variable wind at 27 °C water temperature and 25 °C air temperature.
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densities ranging ranging densities Fingas Figure Figure unstable. as arecharacterised mixed when water (<6%) of formed, despite despite formed, o asphaltene and either low or and low either and unstable. Only andunstable. viscosit large body of oil types for emulsion stability and defined four water four defined and stability emulsion for oilof types body large and resin content (Fingas content resin and other c alongside emulsions, stabilising for factor contributing Studies have shown strong eviden strong shown have Studies 2.3.9 REPORT www.rpsgroup.com/mst M indicative of unstable water unstable of indicative The The >800 f water (> ~20% and up to 80%) and will persist will and 80%) to up and ~20% water(> f AW0815J densities, vis densities, , 000
ies & Fieldhouse & 2
. | 29
cP). Emulsification Characteristics
Browse to NWS Project NWS to Browse
(>6,000 content
Average prop Average
a cosities and and cosities hi reduction
from from
cP). Oil types that form unstable emulsions have low asphaltene or resin or low have asphaltene unstable emulsions typesform Oil that cP). (1 stable, mesostable and entrained water entrained and mesostable stable, gh densit
(201 - 17%). Oil types that form entrained emulsions have have densit entrained emulsions form Oil that types 17%). 0.89
, 5
201 ) lists oil types that form stab form that types lists oil ) - - erties o erties
in Quantitative Spill Risk Assessment Risk Spill Quantitative in mixing energy ( energy mixing in ies g/cm - asphaltene content asphaltene oil emulsio 0 ; Fingas ; Fingas
(<0.85 3
f emulsion stability groups groups stability emulsion f ce that the asphaltene content of oil mixtures is the most important isthe most oilof mixtures content asphaltene the that ce to >1.0
g/cm & n
with <6% water content. <6%with Fieldhouse
g/cm 3
Figure Figure or >1.0
3 for long periods ( periods long for of the the of , high
| 2
, PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES g/cm . Rev 4
29
). Fingas ). 2015 , 2004 le or le unstabilised unstabilised or veryhigh ). Oil mixtures that do not hold significant amounts significant hold not do that mixtures Oil ).
3 - | in ) with either low or high viscosit with) low high or either 27 November 2019 November 27 ontributing properties such as as such properties ontributing meso - oil emulsions hold a relatively high proportion high proportion a relatively hold oil emulsions ( Fingas &Fieldhouse Fingas - stable emulsions. Universally, these have have these Universally, emulsions. stable
in several several - and oil types viscosit stabilised
weeks to weeks
& :
Fieldhouse (2005) analysed a a analysed (2005) Fieldhouse stable, mesostabl stable, ies ies
>0.96 (1 Torosa Torosa more than a than more 4 - 20,000 ,
2004) g/cm C density, viscosity density, viscosity ies ondensates are ondensates
3
content .
cP
and ve
e, entrained e, entrained (<100
) year) once once year)
and high and high
ry high
(<1%) (<1%) Page cP
or
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2.3.10 Subsea Discharge Characteristics
2.3.10.1 Overview High-pressure releases that involve mixed gas and oil will tend to generate relatively small droplet sizes that have slow rise rates, due to viscous resistance imparted by the surrounding seawater, and may become trapped by density layers in the water column (Chen & Yapa, 2002). The buoyancy of the gas cloud may lift entrained oil droplets towards the surface and, in the case of blowouts in relatively shallow water (<100-200 m), the rising column of gas and entrained water can lift the oil to the surface at a substantially faster rate than would occur from the relative buoyancy of the oil alone, opposed by the viscosity of the water column. For deeper releases (200-500 m), the gas will expand to entrain oil droplets towards the surface, but the gas and oil will then tend to separate before the oil surfaces because the gas either goes into solution or accelerates away from the oil droplets. The height at which the gas lift ceases is referred to as the trapping height. The rate at which oil rises from the trapping height will be determined by a number of factors, including the relative buoyancy of the oil versus local water density, the size of the droplets (increased viscous resistance for smaller sizes), the presence of density barriers in the water column and the action of shear currents that might be present in the water column. Given the water temperature and pressure that would be expected at the specified discharge depth, the potential for methane and other gases to convert to gas hydrates (semi-solid crystalline structures that would affect the buoyancy of the plume; Figure 2.30) was considered in this study. The OILMAP model, described in Section 2.1.2, was used in this study to predict the behaviour of the rising plume of gas-oil-water and the oil droplet distribution resulting from the subsea discharge in Scenario 1. Inputs to the OILMAP model included specification of the discharge rate, hole size, gas-to-oil ratio, and the temperature of the oil on exiting and before subsequent cooling by the ambient water. The model input also included temperature and salinity profiles representative of the location. Summaries of the inputs to and outputs of the OILMAP simulations for Scenario 1 are presented in the following section.
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b produced by the rising plume, the droplets will then tend to remain within the wave the within remain to tend will then the droplets plume, rising the by produced Therefore, waves. breaking and wind by induced vertical mixing of displacement lateral the by generated turbulence due to to mixing be subject entrained. T is water ambient as more diameter plume in increasing column (3 column relatively small oil droplets oil droplets small relatively turbulence and velocity discharge high The 27 approximately be to is predicted surfacing of point at the oil water and 7.6 around of velocity a vertical with water surface the to towards jet forecast dro oil will entrain the that gas Scenario for simulation the OILMAP of results The the location. of representative presented in in presented REPORT www.rpsgroup.com/mst MAW0815J w that parameters output resulting and the parameters input OILMAP The 2.3.10.2 Fi
uoyancy relative to other mixing process mixing other to relative uoyancy gure 2
. |
30
Torosa Condensate atTorosa the TRA Scenario 1: Long 1: Scenario Browse to NWS Project NWS to Browse - 10 m deep, depending on the conditions), where they can resist surfacing due to their weak weak their to due surfacing resist can they where conditions), the on depending deep, 10 m
2003). Typical propane. 10% and ethane 10% 80% methane, assumes gas” “natural line for The release point. the at temperatur the basedon formation hydrate for lines equilibrium Theoretical Table Table
2 . 4
for Scenario 1. The model input also in also input model 1. The Scenario for
- (<150
Quantitative Spill Risk Assessment Risk Spill Quantitative plets and ambient sea water pletsandup water ambient sea wato the
in - Term (77
dicative sea temperature profiles with depth are indicated (Johansen, (Johansen, indicated are depth with profiles temperature sea dicative μm) that will have very low rise v rise low very have will that μm) es.
generated by the expanding gas plume is predicted to generate generate is predicted to plume gas expanding the by generated - Day) Surface/ - C Well 1 predict that the discharge will generate a cone of rising rising of cone a will generate discharge the that predict 1
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 November 2019 November 27 Subsea despite reaching the surface due to the the to due surface the reaching despite elocities (<0.25 elocities cluded temperature and salinity profiles profiles salinity and temperature cluded he diameter of the central cone of risin of the central of cone he diameter ter surface. The mixed plume is initially is initially plume The mixed surface. ter
Blowout o m.
er
e used as input into SIMAP are are SIMAP into input as e used
the rising plume, as well as well as as the plume, rising m/s, gradually slowing and and slowing gradually m/s,
cm/s). These droplets will will droplets These cm/s). - mixed layer of the water the of layer mixed f
U nstabilised e and pressure pressure and e Page
lift lift
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The ongoing nature of the release combined with the potential for the plume to breach the water surface may present other hazards, including conditions that may lead to high local concentrations of atmospheric volatiles. These issues should be considered when evaluating the practicality of response operations at or near the blowout site. The results suggest that beyond the immediate vicinity of the blowout the majority of the released hydrocarbons will be present in the upper layers of the ocean, with the potential for oil to form floating slicks under sufficiently calm local wind conditions.
Table 2.4 Near-field subsea discharge model parameters for Scenario 1.
OILMAP Parameter Value Release depth (m BMSL) 425 Oil density (g/cm3) (at 20 °C) 0.78 Oil viscosity (cP) (at 20 °C) 1.09 Inputs Oil temperature (°C) 139 Hole diameter (m) [in] 0.22 [8.5] Gas:oil ratio (m3/m3) [scf/bbl] 17,632 [98,992] Oil flow rate (m3/d) [bbl/d] 1,845 [11,607] Plume diameter (m) 27.2 Plume height (m ASB) 425 (surface) Outputs Plume initial rise velocity (m/s) 7.6 Plume terminal rise velocity (m/s) 5.1 20% droplets of size (µm) 37.4 20% droplets of size (µm) 54.6 Predicted Oil Droplet Size Distribution 20% droplets of size (µm) 70.9 20% droplets of size (µm) 92.2 20% droplets of size (µm) 134.6
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to any to any the from anydrift oil to for time shortest the present the in tables shown estimates time The minimum stephour). (1 one time tha p the summarise tables the in presented are that oil floating by contact for estimates probability The scenario. assessed each for contact of predicted for any point for predicted accumulation the greatest is spill worst replicate in the concentration local accumulated The maximum where relevant. off, washing the indicate concentrations shoreline maximum and mean The with resource. the contact make formight that oil weathering time minimum (i concentration any at arrives oilthat of mass the summing by calculated are concentrations Accumulated ti over accumulate assessm that were defined by by defined were that Tables contour. nil t of probability a attribute not do we Hence, occur. to were conditions unusual veryif contacted possibly be might simulations the replicate of any in greater or concentrations The modelling. the in used data of the samples derived from are probabilities that the to note is important It contours. probability within higher over the course of a spill event to result in concentrations that apparently exceed the threshold. Hence, Hence, threshold. the exceed apparently that concentrations in result to event spill a of course the over possib is it that Note averagi after the shoreline on point any for calculated concentration greatest isthe spills all replicate over averaged concentration local accumulated maximum The estimate. indicate locations if the spill scenario were to occur in the future. The areas outside of the lowest the of outside areas The future. the in occur to were scenario spill the if locations pre the of combination that the Locations with higher probability ratings were exposed during a greater number of spill s of number greater aduring exposed were ratings probability higher with Locations area. study the around occur that conditions metocean in variations and trends given the spill commences, i for concentrations, defined at exposure of probability the of indications as shouldtreated be maps contour The scenario. assessed to the relevant simulations contours are a c are contours the Rather, time. in instant particular at any plume or a slick of a depiction or spill hydrocarbon one anyof con the should that note Readers Scenarios Scenarios 100 the annual period period the annual least o at least the defined minimum threshold concentrations ( threshold concentrations minimum theat defined least Contour maps present estima present maps Contour modelling. stochastic the annualised of results the summarise to following sections threshol defined oil to bycontact and contact time of the probability for Predictions 3.1 3 REPORT www.rpsgroup.com/mst MAW0815J ncluding < thresh < ncluding
t oil will arrive at shorelines as float as at shorelines will arrive oil t
g/m
ne time step. These contours summarise the outcomes for all replicate simulations commencing across across commencing allsimulations replicate for the outcomes summarise contours step. These time ne part of the sensitive receptor, relative receptor, sensitive the partof are presented to summarise estimates of contact risk for locations within potentially sensitive receptors receptors sensitive potentially within locations for risk contact of estimates summarise to presented are
2 that contact contact that ents were included in the analysis, with were inents theanalysis, included
|
and 250 Overview STOCHASTIC ASSESSMEN Browse to NWS Project NWS to Browse 2 to 4. 2 to ds for floating oil, entrained oil and dissolved aromatic hydrocarbons are provided in the provided are hydrocarbons aromatic dissolved and oil entrained oil, floating for ds omposite of a of omposite
g/m me on any discrete part of a shoreline (calculated for individual portions of 0.8 of portions individual for (calculated a shoreline part of on anydiscrete me old) over time at a model cell and subtr and cell a model at time over old) – le that oil films arriving at concentrations that are less than the threshold may accumulate accumulate may threshold the than less are that concentrations arriving at oil films that le
will be less likely under the range of p of range the under likely less will be a total of 100 replicate simulations for Scenario 1 and 1 and Scenario for simulations 100 replicate of a total 2
for shoreline oil; 500 oil; shoreline for Woodside on the shoreline on
-
Quantitative Spill Risk Assessment Risk Spill Quantitative tes for the an the for tes vailing wind and current conditions are more likely to result in contact to these to these in contact resultlikely to more are conditions wind current and vailing large number of theoretical slick paths, slick theoretical of large number refore, locati refore, tour maps presented in this report do not represent the predicted coverage coverage predicted the presenteddo in not thisrepresent report maps tour . All sensitive receptors historically considered for for considered historically receptors All sensitive . ing films at the specified threshold concentration or greater for at least least at for greater or concentration threshold specified at the films ing
during any replicate simulation, and th and simulation, replicate any during nualised probability of contact by insta by contact of probability nualised
ppb for entrained o entrained for ppb to the commencement of the spill. These times then indicate the the then indicate times These the spill. of commencement the to ons that are not calculated to receive e to receive calculated not are that ons
those outlined here being the receptors shown to be at risk at risk to shown be receptors the here being outlined those ndividual loca ndividual
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 1 g/m revailing conditions for this region than areas falling falling areas than region this for conditions revailing
| acting any mass lost through evaporation and and evaporation through lost anymass acting 27 2 , T RESULTS November 2019 November 10 il and dissolv and il tions, at some point in time after thed after time inpoint at some tions, g/m ng over all repli ng over concentrations fo concentrations concentrations
2 integrated over the full duration of the of duration the full over integrated , 50 o areas beyond areas o
g/m ed aromatic hydrocarbons) for at at for hydrocarbons) aromatic ed 2 200 replicate simulations simulations replicate 200
and 100 ntaneous concentrations of of concentrations ntaneous us represents an extreme an extreme represents us
cate simulations. cate
equalling or exceeding or exceeding equalling
xposure at threshold at threshold xposure recast to potentially to potentially recast the lowest probability probability lowest the imulations, in imulations, - Woodside Woodside
percentage contour contour percentage g/m 2
for floating oil; floating for
km length). km
robability robability spil dicating dicating source efined efined Page l risk l risk the the for for
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mean expected and maximum concentrations of accumulated oil can exceed the threshold applied to the probability calculations for the arrival of floating oil even where no instantaneous exceedances above threshold are predicted. It is important to understand that the two parameters (floating concentration and shoreline concentration) are quite distinct, calculated in different ways and representative of alternative outcomes. The floating probability estimates and the shoreline accumulative estimates should therefore be treated as independent estimators of different exposure outcomes, and not directly compared. For the entrained and dissolved components, the tabulated results summarise interrogations of cells representing the water surrounding the sensitive receptor shorelines (or submerged features), with individual buffer zones. Buffer zones were defined with consideration of the bathymetry bordering each receptor, natural boundaries, or sensible legislative boundaries. The modelling for each assessed scenario assumed no mitigation efforts are undertaken to collect or otherwise affect the natural transport and weathering of the oil. The predicted outcomes based on the modelling results are discussed in the following sections in terms of floating, entrained and dissolved aromatic hydrocarbons. Discussion is based around the outcomes of stochastic risk contours. Plots of the Environment that May Be Affected (EMBA) and minimum time to exceedance of concentration thresholds are presented for the assessed thresholds. Figure 3.1 shows transect lines intersecting at the release locations along which maximum entrained oil and dissolved aromatic hydrocarbon concentrations in the water column were extracted for each assessed scenario.
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Figure 3.1 Locations of cross-sections, over a varying latitude (dashed line) and longitude (solid line), along which the distributions of maximum entrained oil and dissolved aromatic hydrocarbon concentrations were extracted for each spill scenario in this study.
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3.2 Scenario 1: Long-Term (77-Day) Surface/Subsea Blowout of Unstabilised Torosa Condensate at the TRA-C Well 3.2.1 Discussion of Results
3.2.1.1 Overview This scenario investigated the probability of exposure to surrounding regions by oil resulting from a long-term (77-day) surface/subsea release of 142,154 m3 of unstabilised Torosa Condensate at the TRA-C well during operations at any time of year, with no mitigation measures applied. During the initial surface release phase, the volatile fractions of the oil (16.5%) are likely to evaporate within 24 hours of exposure to the atmosphere. The low-volatility fraction of the condensate (32.8%) will take longer times of the order of days to weeks to evaporate, and the remaining fraction (50.7%) is expected to persist for an extended period of time as residual oil. During the subsea release phase, the small oil droplets rapidly transported to the sea surface by the rising gas plume will be susceptible to re-entrainment into the wave mixed layer under typical wind conditions. It is likely that the bulk of the oil mass will remain entrained in the water column until degradation processes occur. Due to the weak buoyancy of the oil droplets, the formation of floating slicks is unlikely, and therefore only a small fraction of the volatile compounds is likely to be exposed to the atmosphere. Considering the spill volume and low levels of evaporation expected, there is a high potential for dissolution of soluble aromatic compounds.
3.2.1.2 Floating and Shoreline Oil The probability contour figures for floating oil indicate that concentrations equal to or greater than the 10 g/m2 threshold could potentially be found, in the form of slicks, up to 143 km from the spill site (Figure 3.3). The Scott Reef South, Scott Reef Central and Scott Reef Central – Sandy Islet shoreline receptors are predicted to be contacted by floating oil concentrations at the 10 g/m2 threshold with probabilities of 45%, 9% and 8%, respectively (Table 3.1). At these receptors, the corresponding minimum times to contact at this threshold are 18 hours, 42 hours and 46 hours. The Scott Reef South, Scott Reef Central and Scott Reef Central – Sandy Islet receptors are predicted to experience shoreline oil accumulation in excess of the 100 g/m2 threshold with a probability of 92% (Table 3.1). Potential for accumulation of oil on shorelines is predicted to be significant, with a maximum accumulated volume of 827 m3 and a maximum local accumulated concentration of 34.3 kg/m2 forecast at these receptors (Table 3.1). The predicted zone of shoreline impact is restricted to Sandy Islet, at which these three receptors overlap. Sandy Islet is treated as an emergent feature, while the intertidal reefs to the north and south are treated as submerged features for the purposes of this study. The forecast annualised minimum times to contact and EMBA for floating oil at or above the 1 g/m2 and 10 g/m2 threshold concentrations are depicted in Figure 3.4 to Figure 3.7.
3.2.1.3 Entrained Oil Entrained oil at concentrations equal to or greater than the 100 ppb threshold is predicted to be found up to around 863 km from the spill site (Figure 3.9). Contact by entrained oil at concentrations equal to or greater than 100 ppb is predicted at Scott Reef North, Scott Reef North – Flats and Scott Reef North – Lagoon with probabilities of 100% (Table 3.2). The maximum entrained oil concentration forecast for any receptor is predicted as 23.6 ppm at Scott Reef North. The forecast annualised minimum times to contact and EMBA for entrained oil at or above the 100 ppb threshold concentration are depicted in Figure 3.10 and Figure 3.11, respectively. udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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of around 20 around of re - cross The The forecast annualised minimum times to andcontact times annualised minimum forecast The the 500 13 3 Scott Reef North Scott Reef disso Contact by to be found up to around around up to found to be ( 25,000 above that concentrations Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 50 the than greater or to equal at concentrations hydrocarbons aromatic Dissolved 3.2.1.4 cross The REPORT www.rpsgroup.com/mst MAW0815J Figure 3 . 3 lease site show that concentrations above above concentrations that show leasesite .9 ). The maximu The ).
ppm ppb threshold concentra threshold ppb
. |
12). - at Scott Reef North. Reef at Scott Dissolved Browse to NWS Project NWS to Browse sectional transects of maximum dissolved aromatic hydrocarbon hydrocarbon dissolved aromatic of maximum sectional transects sectional transsectional
m (
Figure 3 lved aromatic hydrocarbons at concentrations equal to or greater than 50 greater or equal to at concentrations hydrocarbons lved aromatic ,
m dissolved aromatic hydrocarbon concentration forecast for any receptor any receptor for forecast concentration hydrocarbon dissolved aromatic m Scott Reef North North Scott Reef
Aromatic Hydrocarbons . 673 ects of maximum entrained oil conce entrainedoil of maximum ects 16
-
). Quantitative Spill Risk Assessment Risk Spill Quantitative
km from the ( spill site from km
tion are depicted in are tion depicted
ppb are expected to extend from the sea surface to depths of around 20 around of depths to the surface sea from extend to expected are ppb –
Flats
and Scott Reef North North Reef Scott and 10,000
ppb are expected to extend from the sea surface to depths to depths the surface sea from extend to expected are ppb Figure Figure Figure Figure
| EMBA EMBA PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Rev 4 3
3 . | . 13). 14 27 November 2019 November 27 for dissolved aromatic hydrocarbons at hydrocarbons aromatic dissolved for ntrations in the vicinity of the release site show show site the release vicinityof in the ntrations and
–
Lagoon
Figure Figure
concentrations in the vicinity of the the vicinity of in the concentrations
3 with probabilities of of probabilities with . 15, respectively.
ppb threshold are predicted predicted are ppb threshold
ppb is predicted at at is predicted ppb
is predicted as as predicted is 100% or above or above
( Page Table Table
m
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3.2.2 Results Tables and Figures
3.2.2.1 Floating and Shoreline Oil
Table 3.1 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation
Argo-Rowley Terrace Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Ashmore Reef Marine Park <1 <1 NC NC 18 547 302 6,657 23 157
Browse Island* <1 <1 NC NC NA NA NA NA NA NA
Buccaneer & Bonaparte Archipelagos <1 <1 NC NC 2 2,349 3.9 155 <1 8
Cartier Island Marine Park <1 <1 NC NC 22 851 87 1,744 8 38
Glomar Shoals & Rankin Bank* <1 <1 NC NC NA NA NA NA NA NA
Hibernia Reef* <1 <1 NC NC NA NA NA NA NA NA
Indonesia <1 <1 NC NC 3 1,722 10 457 8 52
Indonesian Boundary <1 <1 NC NC 3 1,722 10 457 6 57
Kimberley Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Kimberley Coast <1 <1 NC NC 1 2,345 2.7 205 <1 14
Lacepede Islands <1 <1 NC NC <1 NC 0.2 12 <1 <1
Oceanic Shoals Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Pulau Roti <1 <1 NC NC <1 NC 0.2 24 <1 2 Rowley Shoals - Clerke Reef State <1 <1 NC NC 8 1,103 38 583 3 16 Marine Park Rowley Shoals - Imperieuse Reef <1 <1 NC NC 8 1,198 34 557 3 18 State Marine Park Rowley Shoals - Mermaid Reef <1 <1 NC NC 9 1,038 75 1,059 4 25 Marine Park Scott Reef North* 100 100 2 3 NA NA NA NA NA NA
Scott Reef South 88 45 16 18 92 42 8,495 34,279 339 827
Seringapatam Reef* 46 10 30 33 NA NA NA NA NA NA
Sumba <1 <1 NC NC 3 1,742 10 457 4 36
Ashmore Reef <1 <1 NC NC 18 547 302 6,657 23 157
Big Bank Shoals* <1 <1 NC NC NA NA NA NA NA NA
Camden Sound <1 <1 NC NC <1 NC <0.1 7.5 <1 <1
Cartier Island <1 <1 NC NC 22 851 87 1,744 8 38 Dampier Peninsula Coast - Mid <1 <1 NC NC <1 NC <0.1 2.1 <1 <1 Section Dampier Peninsula Coast - North <1 <1 NC NC <1 NC <0.1 2 <1 <1 Section Lalang-garram - Camden Sound <1 <1 NC NC 1 2,395 1.5 149 <1 6 Marine Park
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Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation Rowley Shoals - Clerke Reef <1 <1 NC NC 8 1,103 38 583 3 16
Rowley Shoals - Imperieuse Reef <1 <1 NC NC 8 1,198 34 557 3 18
Rowley Shoals - Mermaid Reef <1 <1 NC NC 9 1,038 75 1,059 4 25
Sahul Banks* <1 <1 NC NC NA NA NA NA NA NA
Savu <1 <1 NC NC <1 NC 0.8 38 <1 5
Scott Reef Central 56 9 31 42 92 42 8,495 34,279 339 827
Scott Reef Central - Sandy Islet 51 8 39 46 92 42 8,495 34,279 339 827
Scott Reef North - Flats* 100 99 3 4 NA NA NA NA NA NA
Scott Reef North - Lagoon* 100 94 6 7 NA NA NA NA NA NA
Scott Reef South - Flats* 62 19 31 34 NA NA NA NA NA NA
Scott Reef South - Lagoon* 88 47 14 15 NA NA NA NA NA NA
Adele Island <1 <1 NC NC <1 NC 1.4 54 <1 2
Barracouta Shoal* <1 <1 NC NC NA NA NA NA NA NA
Echuca Shoal* <1 <1 NC NC NA NA NA NA NA NA
Eighty Mile Beach Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Eugene McDermott Shoal* <1 <1 NC NC NA NA NA NA NA NA
Fantome Bank* <1 <1 NC NC NA NA NA NA NA NA PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Heywood Shoal* <1 <1 NC NC NA NA NA NA NA NA
Oceanic Shoals - Deep Shoal 1* <1 <1 NC NC NA NA NA NA NA NA Oceanic Shoals Region - Gale-Favell- <1 <1 NC NC NA NA NA NA NA NA Baldwin Banks* Oceanic Shoals Region - Margaret <1 <1 NC NC NA NA NA NA NA NA Harries Banks* Oceanic Shoals Region - The Boxers* <1 <1 NC NC NA NA NA NA NA NA
Timor Leste <1 <1 NC NC 1 2,387 1.6 160 <1 7
Timor West <1 <1 NC NC <1 NC 1.1 65 <1 9
Van Cloon Shoal* <1 <1 NC NC NA NA NA NA NA NA
Vulcan & Goeree Shoals* <1 <1 NC NC NA NA NA NA NA NA
WA Coastline <1 <1 NC NC 2 1,892 3.9 205 2 19
NC: No contact to receptor predicted for specified threshold. NA: Not applicable. * Floating oil will not accumulate on submerged features and at open ocean locations.
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Figure 3.2 Predicted annualised probability of floating oil concentrations at or above 1 g/m2 resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.3 Predicted annualised probability of floating oil concentrations at or above 10 g/m2 resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.4 Predicted annualised minimum times to contact by floating oil concentrations at or above 1 g/m2 resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.5 Predicted annualised minimum times to contact by floating oil concentrations at or above 10 g/m2 resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.6 Predicted annualised EMBA of floating oil concentrations at or above 1 g/m2 resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.7 Predicted annualised EMBA of floating oil concentrations at or above 10 g/m2 resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.8 Predicted annualised probability of shoreline oil concentrations at or above 100 g/m2 resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Table Table 3.2.2.2 REPORT www.rpsgroup.com/mst MAW0815J M Park Mermaid ReefM Mermaid M State Reef Imperieuse Argo Coast Coast Peninsula Dampier Penin Dampier Cartier Island Sound Camden Shoals Bank Big Reef Ashmore Sumba Reef Seringapatam South Reef Scott S Rowley Shoals Rowley Shoals M State Reef Rowley Shoals Roti Pulau Park Shoals M Oceanic Is Lacepede Coast Kimberley M Kimberley Boundary Indonesian Indonesia Hibernia Reef Bank Shoals & Rankin Glomar Park Cartier Island M Archipelagos & Bonaparte Buccaneer Browse Island Park M Reef Ashmore Receptor Coast Coast cott Reef North cott Reef arine Park arine
-
Rowley Terrace Rowley Terrace - -
3 Park North Section North Mid Section .
2
|
Entrained Oil Entrained Browse to NWS Project NWS to Browse
lan arine Parkarine
arine Park arine
sul subsea surface/ entrain annualised Expected ds - - -
arine
arine
Clerke arine
a arine
Probability (%) of
concentration
entrained o -
Quantitative Spill Risk Assessment Risk Spill Quantitative ≥10
release of of release 100 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 21 13 87 97 31 13 0 8 8 8 3 1 8
ppb
il il
unstabilised unstabilised ed oil outcomes at sensitive receptors r receptors sensitive at outcomes oil ed receptor (hours) for Minimum time to to time Minimum entrained oil at entrained oil ≥100 1,036
394 498 334 478 397 355 700 987 390 NC NC NC NC NC NC NC NC NC NC NC NC NC NC 37 13 | 3
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Torosa Condensate at the TRA atthe Condensate Torosa Rev 4
ppb
|
27 November 2019 November 27 replicate simulations Maximum averaged overall 7,858 1,241 3,576
<1 <1 <1 <1 <1 <1 <1 <1 <1 64 30 10 77 32 26 15 17 28 3 3 6 2 2 3
entrainedconcentration oil (ppb)
esulting from a 77 a from esulting
- C well at any depth, in the worst replicate replicate worst simulation . 23,584 11,647 1,010
5,213 719 301 137 345 502 328 305 101 602 <1 <1 96 44 86 33 38 19 53 98 3 3 9 2
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Probability (%) of Minimum time to entrained oil receptor (hours) for Maximum entrained oil concentration (ppb) concentration entrained oil at Receptor at any depth, in the averaged over all ≥100 ppb ≥100 ppb worst replicate replicate simulations simulation Lalang-garram - Camden <1 NC <1 50 Sound Marine Park Rowley Shoals - Clerke <1 NC 5 61 Reef Rowley Shoals - <1 NC 2 30 Imperieuse Reef Rowley Shoals - 8 1,055 9 119 Mermaid Reef Sahul Banks <1 NC 3 51
Savu <1 NC <1 11
Scott Reef Central 92 29 2,079 7,648 Scott Reef Central - 91 35 2,079 7,648 Sandy Islet Scott Reef North - Flats 100 4 6,259 18,068 Scott Reef North - 100 6 3,762 10,505 Lagoon Scott Reef South - Flats 94 21 2,873 9,004 Scott Reef South - 97 12 3,387 11,747 Lagoon Adele Island <1 NC 2 71
Barracouta Shoal 8 621 29 348
Echuca Shoal <1 NC 10 77 Eighty Mile Beach <1 NC <1 2 Marine Park Eugene McDermott 6 973 17 155 Shoal Fantome Bank 1 1,935 6 149
Heywood Shoal 5 867 16 144 Oceanic Shoals - Deep <1 NC <1 18 Shoal 1 Oceanic Shoals Region - Gale-Favell-Baldwin <1 NC 2 27 Banks Oceanic Shoals Region - <1 NC <1 24 Margaret Harries Banks Oceanic Shoals Region - <1 NC <1 12 The Boxers Timor Leste <1 NC <1 8
Timor West <1 NC <1 4
Van Cloon Shoal <1 NC <1 25
Vulcan & Goeree Shoals 10 535 23 227
WA Coastline <1 NC 3 93
NC: No contact to receptor predicted for specified threshold. * Probabilities and maximum concentrations calculated at depth of submerged feature.
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Figure 3.9 Predicted annualised probability of entrained oil concentrations at or above 100 ppb resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.10 Predicted annualised minimum times to contact by entrained oil concentrations at or above 100 ppb resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.11 Predicted annualised EMBA of entrained oil concentrations at or above 100 ppb resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.12 Cross-section transects of predicted annualised maximum entrained oil concentrations for a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well. Transect locations are shown in Figure 3.1.
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Table Table 3.2.2.3 REPORT www.rpsgroup.com/mst MAW0815J Sound M Sound Park Lalang Section North Coast Peninsula Dampier Section Coast Peninsula Dampier Cartier Island Sound Camden Shoals Bank Big Reef Ashmore Sumba Reef Seringapatam South Reef Scott North Reef Scott M Rowley Shoals M State Reef Rowley Shoals State M Rowley Shoals Roti Pulau Shoals M Oceanic Islands Lacepede Coast Kimberley M Kimberley Boundary Indonesian Indonesia Hibernia Reef Shoals & Rankin BankGlomar Cartier Island Archipelagos & Bonaparte Buccaneer Browse Island M Reef Ashmore Receptor Argo Park arine
- Rowley Terrace M Rowley Terrace -
3
garram garram Park arine . Park arine
3
|
Dissolved AromaticHydrocarbons Browse to NWS Project NWS to Browse arine Parkarine
arine Park arine
M
TRA resulting receptors sensitive at outcomes hydrocarbon aromatic dissolved annualised Expected - - - -
arine Parkarine
Camden Camden Mermaid ReefMermaid Imperieuse Reef Clerke Park arine
Park arine -
C well
arine
- -
Mid fro .
m a 77 m -
Quantitative Spill Risk Assessment Risk Spill Quantitative Probability (%) of d aromatic hydrocarbon - day surface/ day concentration ≥50 100 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 19 85 10 10 98 5 1 9 1 3 1 6
ppb
issolved issolved
subsea
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Rev 4
release of of release averaged overall replicate Maximum dissolved aromatic hydrocarbonconcentration
| 27 November 2019 November 27 simulations 2,659 3,839 957 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 unstabilised unstabilised 32 13 15 15 6 3 2 9
(ppb) Torosa Condensate at the the at Condensate Torosa
at any depth, in the worst replicate simulation replicate 12,404 13,907 1,281 6,635 198 155 291 332 394 860 NC <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 25 10 86 71 58 7 5
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Probability (%) of dissolved Maximum dissolved aromatic hydrocarbon concentration aromatic hydrocarbon (ppb) Receptor concentration averaged over all replicate at any depth, in the worst ≥50 ppb simulations replicate simulation Rowley Shoals - Clerke Reef <1 <1 9 Rowley Shoals - Imperieuse <1 <1 5 Reef Rowley Shoals - Mermaid Reef <1 <1 25
Sahul Banks <1 <1 2
Savu <1 <1 13
Scott Reef Central 92 1,420 7,015
Scott Reef Central - Sandy Islet 91 1,420 7,015
Scott Reef North - Flats 100 3,582 10,655
Scott Reef North - Lagoon 100 2,611 9,652
Scott Reef South - Flats 94 2,659 12,404
Scott Reef South - Lagoon 98 2,572 11,654
Adele Island <1 <1 2
Barracouta Shoal 1 3 62
Echuca Shoal <1 <1 9
Eighty Mile Beach Marine Park <1 <1 <1
Eugene McDermott Shoal <1 <1 30
Fantome Bank 1 2 141
Heywood Shoal <1 <1 16
Oceanic Shoals - Deep Shoal 1 <1 <1 <1 Oceanic Shoals Region - Gale- <1 <1 <1 Favell-Baldwin Banks Oceanic Shoals Region - <1 <1 <1 Margaret Harries Banks Oceanic Shoals Region - The <1 <1 <1 Boxers Timor Leste <1 <1 <1
Timor West <1 <1 <1
Van Cloon Shoal <1 <1 <1
Vulcan & Goeree Shoals 2 3 68
WA Coastline <1 <1 2
NC: No contact to receptor predicted for specified threshold. * Probabilities and maximum concentrations calculated at depth of submerged feature.
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Figure 3.13 Predicted annualised probability of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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Figure 3.14 Predicted annualised minimum times to contact by dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.15 Predicted annualised EMBA of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well.
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www.rpsgroup.com/mst Page 77 1883 10D Tech nTeicalchnical St udiStudieses 1884 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
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Figure 3.16 Cross-section transects of predicted annualised maximum dissolved aromatic hydrocarbon concentrations for a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well. Transect locations are shown in Figure 3.1.
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The Scott Reef South, Scott Reef Central and Scott Reef C Reef Scott and Central Reef Scott South, Scott Reef The hours. and 57 21 hours are threshold to at contact times this minimum corresponding the receptors, experience shoreline oil accumulation in excess of the the of excess in accumulation oil shoreline experience that concentrations above 25,000 above that concentrations cross The ( concentrations at the 10 at the concentrations oil be floating contacted by to predicted are receptors shoreline Central Scott Reef South Scott Reef and The - (24 The forecast annualised minimum times to contact times annualised minimum forecast The ( The forecast annuali forecast The concentrations. peak dur a sustained for coherent mass a more as move likelyto Torosa threshold concentration are depicted in depicted are concentration threshold volume of 212 of volume 3 period of time as residual oil. residual as time of period isexpecte (14.0%) fraction and remaining to the evaporate, weeks days to of order low The atmosphere. the to exposure threshold could potentially be found, in the form of of form the in be found, potentially could threshold threshold concentration threshold Contact by entrained oil at concentrations equal to or greater than than greater or to equal concentrations at oil entrained by Contact around around The probability co probability The 3.3.1.2 a short resultingfrom oil by regions surrounding to exposure of probability the investigated scenario This 3.3.1.1 3.3.1 3.3 REPORT www.rpsgroup.com/mst MAW0815J concentration oilat Entrained 3.3.1.3 During the surface release, the volatile fractions the release, thesurface During applied. measures a vessel collision a vesselcollision being higher (1,846 being higher 2 Scenario in release rate equivalent the to attributable is this1, result and Scenario in forecast concentration forecast for any for receptor forecast (4 sensitive receptors with probabilities of less than than less of probabilities with sensitive receptors Figure 3 Table Table . 4 8.5 ). Potential for accumulation of oil on shorelines is pr is shorelines on oil of accumulation for Potential ). hour) surface release o release surface hour)
%), Scott Reef North North Reef Scott %), 3
890 Condensate in one day). The oil plume will initially be more concentrated in the latter case and will be will be and case latter the in concentrated more be will initially plume oil The day). one in Condensate
.
4 . |
27). - ). Scenario 2: Short 2: Scenario Discussion of Results Discussion Floating and Shoreline and Floating Oil Overview Entrained Oil Entrained Rupture S Browse to NWS Project NWS to Browse sectional transects of maximum entrained oil concentrations in the vicinity of the release site show show site thevicinity release of in the concentrations entrainedoil of maximum transects sectional
km from the spill ( site from km tabil
m 3
ntour figures for floating oil indicate that concentrations equal to or greater than the 10 the than orgreater to equal concentrations that indicate oil floating for figures ntour
and a maximum local accumulated concentration of 9.5 of concentration local accumulated and a maximum he Torosa FPSO location FPSO Torosa at the
ised Torosa ised m
sed minimum times to contact times minimum sed 3
/d s
ay g/m at the Torosa FPSO Location FPSO Torosa the at are depicted
is predicted as 30.5 as predicted is f 18,000 f
-
–
of of Quantitative Spill Risk Assessment Risk Spill Quantitative
2
s equal to or greater than the the than greater or to equal s
Flats ( threshold with proba threshold unstabilised
Figure Figure pp
m %) and Scott Reef North North Reef Scott and 46%) b are expected to extend from t from extend to expected are b -
3 in in volatil
of Figure Figure - Condensate after a Vessel Cargo Tank Tank Cargo afterVessel a Condensate Figure Figure
3 Term (24 Term stabilised . 24).
Torosa Condensate Condensate Torosa
ity fraction of the condensate (8.0%) will take longer times of the the of times longer will take (8.0%) condensate the of ity fraction
3
ppm atNorth. Scott Reef ppm 3 . 25
. of the oil (78.0%) are likely to evaporate within 24 hours of hours within 24 evaporate to likely are oil the (78.0%) of
30 19 during operations at any time of year, with no mitigation year, with no mitigation of at time any operations during and slicks, up126 to slicks, bilities of 6.5%and 2% of bilities
Torosa and and % (
to
| and EMBA EMBA
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 edicted to be moderate, with a maximum accumulated accumulated maximum a with moderate, be to edicted Figure Figure 10 Table Table Figure Figure - Hour) Surface Release of Release Surface Hour) 0
EMBA EMBA Condensate Condensate
ation before diffusion processes act processes ation before to diffusion reduce the g/m | 1 for floating oil at or above the above at or oil floating for 27 November 2019 November 27 00 entral entral 3 3 3 . 2 . 5 each day versus 18,000 versus day each 22 .
ppb 26, threshold with a probability of of probability with threshold a ). The maximum entrained o entrained maximum The ). – for entrained oil at or above the oilthe at or above entrained for .
km from the spill site ( the spill from site km 1 Lagoon ( Lagoon –
he sea surface to depths of around 20 around of depths to he surface sea
respectively. threshold threshold 00
Sandy Sandy after a vessel cargo tank rupture rupture tank cargo vessel a after ppb is predicte ppb
This is greater than the maximum maximum the isgreater than This , respec
kg/m 4 Islet 0%), as we as 0%), is 2
predicted to be found up to to up found be to predicted
forecast at forecast d to persist for an extended anextended for to persist d tively receptors are predicted to to arepredicted receptors d at Scott Reef North North Reef Scott at d
(
Table Table m Figure Figure
1 ll as several other ll other several as 3
g/m /d
these receptors receptors these il concentration il concentration ay 3 20.5 2
3
. of of and 4 . 18). ).
stabilised stabilised % (
At these these At 1 10 00
Page Table Table -
g/m g/m from from term
ppb
m
79 2 2
1885 10D Tech nTeicalchnical St udiStudieses 1886 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
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3.3.1.4 Dissolved Aromatic Hydrocarbons Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 50 ppb threshold are predicted to be found up to around 517 km from the spill site (Figure 3.28). Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 50 ppb is predicted at Scott Reef North (41.5%), Scott Reef North – Flats (39.5%) and Scott Reef North – Lagoon (33.5%), as well as several other receptors with probabilities of less than 25% (Table 3.6). The maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as 12.7 ppm at Scott Reef North. The forecast annualised minimum times to contact and EMBA for dissolved aromatic hydrocarbons at or above the 50 ppb threshold concentration are depicted in Figure 3.29 and Figure 3.30, respectively. The cross-sectional transects of maximum dissolved aromatic hydrocarbon concentrations in the vicinity of the release site show that concentrations above 10,000 ppb are expected to extend from the sea surface to depths of around 15 m (Figure 3.31).
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3.3.2 Results Tables and Figures
3.3.2.1 Floating and Shoreline Oil
Table 3.4 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation
Argo-Rowley Terrace Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Ashmore Reef Marine Park <1 <1 NC NC 1 615 3.6 208 <1 4
Browse Island* <1 <1 NC NC NA NA NA NA NA NA
Buccaneer & Bonaparte Archipelagos <1 <1 NC NC <1 NC 0.3 28 <1 2
Cartier Island Marine Park <1 <1 NC NC 1 410 3 204 <1 5
Glomar Shoals & Rankin Bank* <1 <1 NC NC NA NA NA NA NA NA
Hibernia Reef* <1 <1 NC NC NA NA NA NA NA NA
Indonesia <1 <1 NC NC <1 NC 0.4 74 <1 8
Indonesian Boundary <1 <1 NC NC <1 NC <0.1 8.2 <1 <1
Kimberley Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Kimberley Coast <1 <1 NC NC <1 NC 0.5 45 <1 3 PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Lacepede Islands <1 <1 NC NC <1 NC NC NC NC NC
Oceanic Shoals Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Pulau Roti <1 <1 NC NC <1 NC NC NC NC NC Rowley Shoals - Clerke Reef State <1 <1 NC NC <1 NC 0.5 98 <1 4 Marine Park Rowley Shoals - Imperieuse Reef <1 <1 NC NC <1 NC 0.3 65 <1 2 State Marine Park Rowley Shoals - Mermaid Reef <1 <1 NC NC <1 NC 0.2 25 <1 <1 Marine Park Scott Reef North* 34 22.5 7 7 NA NA NA NA NA NA
Scott Reef South 12 6.5 18 21 20.5 39 320 9,535 13 212
Seringapatam Reef* 7 4 37 41 NA NA NA NA NA NA
Sumba <1 <1 NC NC <1 NC <0.1 8.2 <1 <1
Ashmore Reef <1 <1 NC NC 1 615 3.6 208 <1 4
Big Bank Shoals* <1 <1 NC NC NA NA NA NA NA NA
Camden Sound <1 <1 NC NC <1 NC NC NC NC NC
Cartier Island <1 <1 NC NC 1 410 3 204 <1 5 Dampier Peninsula Coast - Mid <1 <1 NC NC <1 NC NC NC NC NC Section Dampier Peninsula Coast - North <1 <1 NC NC <1 NC NC NC NC NC Section Lalang-garram - Camden Sound <1 <1 NC NC <1 NC NC NC NC NC Marine Park
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Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation Rowley Shoals - Clerke Reef <1 <1 NC NC <1 NC 0.5 98 <1 4
Rowley Shoals - Imperieuse Reef <1 <1 NC NC <1 NC 0.3 65 <1 2
Rowley Shoals - Mermaid Reef <1 <1 NC NC <1 NC 0.2 25 <1 <1
Sahul Banks* <1 <1 NC NC NA NA NA NA NA NA
Savu <1 <1 NC NC <1 NC NC NC NC NC
Scott Reef Central 5 2 34 57 20.5 39 320 9,535 13 212
Scott Reef Central - Sandy Islet 5 1 37 68 20.5 39 320 9,535 13 212
Scott Reef North - Flats* 29.5 20 8 9 NA NA NA NA NA NA
Scott Reef North - Lagoon* 25 12 9 11 NA NA NA NA NA NA
Scott Reef South - Flats* 7.5 4 22 29 NA NA NA NA NA NA
Scott Reef South - Lagoon* 12 4.5 19 22 NA NA NA NA NA NA
Adele Island <1 <1 NC NC <1 NC NC NC NC NC
Barracouta Shoal* <1 <1 NC NC NA NA NA NA NA NA
Echuca Shoal* <1 <1 NC NC NA NA NA NA NA NA
Eighty Mile Beach Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Eugene McDermott Shoal* <1 <1 NC NC NA NA NA NA NA NA
Fantome Bank* <1 <1 NC NC NA NA NA NA NA NA
Heywood Shoal* <1 <1 NC NC NA NA NA NA NA NA
Oceanic Shoals - Deep Shoal 1* <1 <1 NC NC NA NA NA NA NA NA Oceanic Shoals Region - Gale-Favell- <1 <1 NC NC NA NA NA NA NA NA Baldwin Banks* Oceanic Shoals Region - Margaret <1 <1 NC NC NA NA NA NA NA NA Harries Banks* Oceanic Shoals Region - The Boxers* <1 <1 NC NC NA NA NA NA NA NA
Timor Leste <1 <1 NC NC <1 NC NC NC NC NC
Timor West <1 <1 NC NC <1 NC NC NC NC NC
Van Cloon Shoal* <1 <1 NC NC NA NA NA NA NA NA
Vulcan & Goeree Shoals* <1 <1 NC NC NA NA NA NA NA NA
WA Coastline <1 <1 NC NC <1 NC 0.5 47 <1 4
NC: No contact to receptor predicted for specified threshold. NA: Not applicable. * Floating oil will not accumulate on submerged features and at open ocean locations.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.17 Predicted annualised probability of floating oil concentrations at or above 1 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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Figure 3.18 Predicted annualised probability of floating oil concentrations at or above 10 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.19 Predicted annualised minimum times to contact by floating oil concentrations at or above 1 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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Figure 3.20 Predicted annualised minimum times to contact by floating oil concentrations at or above 10 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.21 Predicted annualised EMBA of floating oil concentrations at or above 1 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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Figure 3.22 Predicted annualised EMBA of floating oil concentrations at or above 10 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.23 Predicted annualised probability of shoreline oil concentrations at or above 100 g/m2 resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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3.3.2.2 Entrained Oil
Table 3.5 Expected annualised entrained oil outcomes at sensitive receptors resulting from a 24- hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
Probability (%) of Minimum time to entrained oil receptor (hours) for Maximum entrained oil concentration (ppb) concentration entrained oil at Receptor at any depth, in the averaged over all ≥100 ppb ≥100 ppb worst replicate replicate simulations simulation Argo-Rowley Terrace 1.5 464 5 545 Marine Park Ashmore Reef Marine 2.5 287 14 1,118 Park Browse Island <1 NC 2 77 Buccaneer & Bonaparte <1 NC <1 54 Archipelagos Cartier Island Marine 1.5 374 6 444 Park Glomar Shoals & Rankin <1 NC NC NC Bank Hibernia Reef <1 344 3 406
Indonesia <1 NC <1 19
Indonesian Boundary <1 593 2 341
Kimberley Marine Park 4.5 271 14 704
Kimberley Coast <1 NC <1 82
Lacepede Islands <1 NC NC NC Oceanic Shoals Marine <1 NC <1 56 Park Pulau Roti <1 NC NC NC Rowley Shoals - Clerke <1 NC <1 40 Reef State Marine Park Rowley Shoals - Imperieuse Reef State <1 NC <1 40 Marine Park Rowley Shoals - Mermaid Reef Marine <1 NC <1 89 Park Scott Reef North 48.5 7 2,775 30,461
Scott Reef South 29.5 17 1,115 21,848
Seringapatam Reef 22.5 30 375 10,263
Sumba <1 NC <1 2
Ashmore Reef 2.5 292 12 916
Big Bank Shoals <1 NC <1 3
Camden Sound <1 NC <1 10
Cartier Island 1.5 386 6 358 Dampier Peninsula NC NC NC 1> Coast - Mid Section udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
ical www.rpsgroup.com/mst Page 90 n ch e T 10D
REPORT www.rpsgroup.com/mst MAW0815J c and concentrations maximum Probabilities * threshold. specified for predicted receptor to No contact NC: Lagoon Banks Lagoon Reef Mermaid Reef Imperieuse M Sound Dampier Dampier WA Coastline WA & Shoals Goeree Vulcan Shoal Cloon Van Timor Leste Timor BoxersThe Shoals Region Oceanic Banks Margaret Harries Shoals Region Oceanic Gale Shoals Region Oceanic 1 Shoal Shoals Oceanic Heywood Shoal Fanto Shoal McDermott Eugene M Beach Mile Eighty Shoal Echuca Shoal Barracouta Adele Island Reef Scott Scott North Reef Scott North Reef Scott Islet Sandy Central Reef Scott Central Reef Scott Savu Banks Sahul Rowley Shoals Rowley Shoals Reef Rowley Shoals Lalang Coast Receptor Park arine -
Favell me Bank me South Reef
West - -
garram garram
North Section North Park arine Peninsula Peninsula
|
South South
-
Browse to NWS Project NWS to Browse Baldwin
- - - -
-
Camden Camden
Clerke
- -
- - Deep
Flats Flats -
- - -
Probability (%) of
concentration entrained oil -
Quantitative Spill Risk Assessment Risk Spill Quantitative ≥100 29.5 26.5 24.5 1.5 2.5 1.5 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 46 40 27 1
ppb
alculated at depth of atalculated depth submerged
receptor (hours) for Minimum time to to time Minimum
entrained oil at entrained oil ≥100
916 402 824 924 533 591 NC NC NC NC NC NC NC NC NC NC N NC NC NC NC NC NC 17 23 10 35 31 | 8 C
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
ppb
|
27 November 2019 November 27 feature. replicate simulations Maximum entrained oil concentration(ppb) averaged overall
2,134 1,115 1,086
639 472 472 NC NC NC NC <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 6 4 2 7 5
at any depth, in the worst simulation 17,516 21,848 22,127 21,848 21,437 15,894 129 726 204 129 206 184 NC NC NC NC replicate replicate <1 <1 34 58 37 34 34 77 34 60 5 8 2
Page
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1897 10D Tech nTeicalchnical St udiStudieses 10D
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Figure 3.24 Predicted annualised probability of entrained oil concentrations at or above 100 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.25 Predicted annualised minimum times to contact by entrained oil concentrations at or above 100 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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Figure 3.26 Predicted annualised EMBA of entrained oil concentrations at or above 100 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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REPORT www.rpsgroup.com/mst MAW0815J Figure Figure 3
. |
27 Browse to NWS Project NWS to Browse
rupture for a 24 for Cross - section transects of predicted annualised maximum ent maximum annualised predicted of transects section - at the Torosa FPSO location FPSO Torosa at the hour surface release of release of surface hour
-
Quantitative Spill Risk Assessment Risk Spill Quantitative stabilised stabilised .
Transect locations are shown in shown are locations Transect | PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
Torosa | 27 November 2019 November 27
Condensate after a vessel cargo tank cargo tank a after vessel Condensate
rained oil concentrations concentrations oil rained Figure 3 . 1 .
Page
95
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3.3.2.3 Dissolved Aromatic Hydrocarbons
Table 3.6 Expected annualised dissolved aromatic hydrocarbon outcomes at sensitive receptors resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
Probability (%) of dissolved Maximum dissolved aromatic hydrocarbon concentration aromatic hydrocarbon (ppb) Receptor concentration averaged over all replicate at any depth, in the worst ≥50 ppb simulations replicate simulation Argo-Rowley Terrace Marine 1.5 2 164 Park Ashmore Reef Marine Park 1.5 3 272
Browse Island <1 <1 2 Buccaneer & Bonaparte <1 NC NC Archipelagos Cartier Island Marine Park <1 <1 40
Glomar Shoals & Rankin Bank <1 NC NC
Hibernia Reef <1 <1 96
Indonesia <1 <1 <1
Indonesian Boundary <1 NC NC
Kimberley Marine Park 2 3 416
Kimberley Coast <1 NC NC
Lacepede Islands <1 NC NC
Oceanic Shoals Marine Park <1 NC NC
Pulau Roti <1 NC NC Rowley Shoals - Clerke Reef <1 NC NC State Marine Park Rowley Shoals - Imperieuse <1 NC NC Reef State Marine Park Rowley Shoals - Mermaid Reef <1 <1 5 Marine Park Scott Reef North 41.5 683 12,749
Scott Reef South 24.5 334 9,440
Seringapatam Reef 15.5 125 6,095
Sumba <1 NC NC
Ashmore Reef 1.5 2 221
Big Bank Shoals <1 NC NC
Camden Sound <1 NC NC
Cartier Island <1 <1 34 Dampier Peninsula Coast - Mid <1 NC NC Section Dampier Peninsula Coast - <1 NC NC North Section Lalang-garram - Camden <1 NC NC Sound Marine Park udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
ical www.rpsgroup.com/mst Page 96 n ch e T 10D
REPORT www.rpsgroup.com/mst MAW0815J of at depth calculated feature and submerged concentrations maximum Probabilities * threshold. specified for predicted receptor to No contact NC: WA Coastline WA & Goeree Vulcan Shoal Cloon Van West Timor Leste Timor Boxers Shoals Region Oceanic Banks Margaret Harries Shoals Region Oceanic Favell Shoals Region Oceanic Shoals Oceanic Heywood Shoal Fantome Shoal McDermott Eugene Mile M Beach Eighty Shoal Echuca Shoal Barracouta Adele Island South Reef Scott South Reef Scott North Reef Scott North Reef Scott Central Reef Scott Central Reef Scott Savu Banks Sahul Rowley Shoals Reef Sh Rowley Rowley Shoals Receptor
- Baldwin Banks
Bank
| oals oals
Browse to NWS Project NWS to Browse
- - -
-
Mermaid Reef Mermaid Imperieuse Reef Clerke
- -
- - Shoals Deep Shoal 1
Lagoon Flats Lagoon Flats -
Sandy Islet Sandy Park arine
- - -
The Gale
-
-
Quantitative Spill Risk Assessment Risk Spill Quantitative Probability (%) of dissolved aromatic hydrocarbon concentration ≥50 24.5 18.5 16.5 33.5 39.5 18.5 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1
ppb
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 averaged overall replicate Ma
ximum dissolved aromatic hydrocarbonconcentration | 27 November 2019 November 27 simulations 334 203 129 364 583 129 NC NC NC NC NC NC NC NC NC NC NC NC <1 <1 <1 <1 <1 <1 <1 <1 <1 .
(ppb)
at any depth, in the worst replicate sim replicate 11,196 12,034 9,440 6,554 5,777 5,777 NC NC NC NC NC NC NC NC NC NC NC NC <1 <1 <1 12 15 32 11 3 3
ulation
Page
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1903 10D Tech nTeicalchnical St udiStudieses 10D
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Figure 3.28 Predicted annualised probability of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.29 Predicted annualised minimum times to contact by dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 24- hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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Figure 3.30 Predicted annualised EMBA of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location.
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REPORT www.rpsgroup.com/mst MAW0815J Figure Figure 3
. |
31 Browse to NWS Project NWS to Browse
locations are shown in shown are locations Condensate after a vessel cargo tank rupture cargo rupture tank a after vessel Condensate hydrocarbon concentrations for a 24 for concentrations hydrocarbon Cross - section transects of predicted annualised m annualised predicted of transects section
-
Quantitative Spill Risk Assessment Risk Spill Quantitative Figure 3 . 1 .
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 - hour surface release of of release surface hour
| 27 November 2019 November 27 at the at Torosa FPSO
aximum dissolved aromatic aromatic dissolved aximum
stabilised stabilised location . Transect Transect Torosa Page
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3.4 Scenario 3: Short-Term (Instantaneous) Surface Release of Stabilised Torosa Condensate after an FPSO Offtake System Failure at the Torosa FPSO Location 3.4.1 Discussion of Results
3.4.1.1 Overview This scenario investigated the probability of exposure to surrounding regions by oil resulting from a short-term (instantaneous) surface release of 768 m3 of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location during operations at any time of year, with no mitigation measures applied. During the surface release, the volatile fractions of the oil (78.0%) are likely to evaporate within 24 hours of exposure to the atmosphere. The low-volatility fraction of the condensate (8.0%) will take longer times of the order of days to weeks to evaporate, and the remaining fraction (14.0%) is expected to persist for an extended period of time as residual oil.
3.4.1.2 Floating and Shoreline Oil The probability contour figures for floating oil indicate that concentrations equal to or greater than the 10 g/m2 threshold could potentially be found, in the form of slicks, up to 67 km from the spill site (Figure 3.33). The Scott Reef South shoreline receptor is predicted to be contacted by floating oil concentrations at the 10 g/m2 threshold with a probability of 1.5% and a minimum contact time of 24 hours (Table 3.7). The Scott Reef South, Scott Reef Central and Scott Reef Central – Sandy Islet receptors are predicted to experience shoreline oil accumulation in excess of the 100 g/m2 threshold with a probability of 2.5% (Table 3.7). Potential for accumulation of oil on shorelines is predicted to be low, with a maximum accumulated volume of 8 m3 and a maximum local accumulated concentration of 715 g/m2 forecast at these receptors (Table 3.7). The forecast annualised minimum times to contact and EMBA for floating oil at or above the 1 g/m2 and 10 g/m2 threshold concentrations are depicted in Figure 3.34 to Figure 3.37.
3.4.1.3 Entrained Oil Entrained oil at concentrations equal to or greater than the 100 ppb threshold is predicted to be found up to around 242 km from the spill site (Figure 3.39). Contact by entrained oil at concentrations equal to or greater than 100 ppb is predicted at Scott Reef North (28%), Scott Reef North – Flats (25%) and Scott Reef North – Lagoon (20%; Table 3.8). The maximum entrained oil concentration forecast for any receptor is predicted as 6.4 ppm at Scott Reef North and Scott Reef North – Flats. The forecast annualised minimum times to contact and EMBA for entrained oil at or above the 100 ppb threshold concentration are depicted in Figure 3.40 and Figure 3.41, respectively. The cross-sectional transects of maximum entrained oil concentrations in the vicinity of the release site show that concentrations above 15,000 ppb are expected to extend from the sea surface to depths of around 15 m (Figure 3.42).
3.4.1.4 Dissolved Aromatic Hydrocarbons Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 50 ppb threshold are predicted to be found up to around 271 km from the spill site (Figure 3.43). Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 50 ppb is predicted at Scott Reef North (23%) and Scott Reef North – Flats (22.5%; Table 3.9). The maximum dissolved aromatic udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
ical www.rpsgroup.com/mst Page 102 n ch e T 10D
of around of show releasesite - cross The hydrocarbon concentratio hydrocarbon REPORT www.rpsgroup.com/mst MAW0815J the 50 to andcontact times annualised minimum forecast The North Reef
ppb threshold concentration are depicted are concentration threshold ppb
|
1 Browse to NWS Project NWS to Browse sectional transects of maximum dissolved aromatic hydrocarbon concentrations in the vicinity of the the vicinity of in the concentrations hydrocarbon dissolved aromatic of maximum sectional transects 0 –
m ( Lagoon. Figure 3 t hat concentrations above above hat concentrations
. 46 n forecast for any receptor is predicted as 1.8 as predicted is receptor any for forecast n
-
). Quantitative Spill Risk Assessment Risk Spill Quantitative
1 ,000
in in
ppb are expected to extend from the sea surface to depths to depths the surface sea from to extend expected are ppb Figure Figure
| EMBA EMBA PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 3
. 44 | 27 Nov c hydrocarbons at or above at above or hydrocarbons c aromati dissolved for
and ember 2019 ember
Figure Figure
ppm at Scott Reef North and Scott Scott and at Scottppm Reef North 3
. 45 , respectively.
Page
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3.4.2 Results Tables and Figures
3.4.2.1 Floating and Shoreline Oil
Table 3.7 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation
Argo-Rowley Terrace Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Ashmore Reef Marine Park <1 <1 NC NC <1 NC 0.1 15 <1 <1
Browse Island* <1 <1 NC NC NA NA NA NA NA NA
Buccaneer & Bonaparte Archipelagos <1 <1 NC NC <1 NC NC NC NC NC
Cartier Island Marine Park <1 <1 NC NC <1 NC <0.1 13 <1 <1
Glomar Shoals & Rankin Bank* <1 <1 NC NC NA NA NA NA NA NA
Hibernia Reef* <1 <1 NC NC NA NA NA NA NA NA
Indonesia <1 <1 NC NC <1 NC NC NC NC NC
Indonesian Boundary <1 <1 NC NC <1 NC NC NC NC NC
Kimberley Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Kimberley Coast <1 <1 NC NC <1 NC NC NC NC NC
Lacepede Islands <1 <1 NC NC <1 NC NC NC NC NC
Oceanic Shoals Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Pulau Roti <1 <1 NC NC <1 NC NC NC NC NC Rowley Shoals - Clerke Reef State <1 <1 NC NC <1 NC <0.1 11 <1 <1 Marine Park Rowley Shoals - Imperieuse Reef <1 <1 NC NC <1 NC <0.1 4.8 <1 <1 State Marine Park Rowley Shoals - Mermaid Reef <1 <1 NC NC <1 NC NC NC NC NC Marine Park Scott Reef North* 11.5 5.5 6 7 NA NA NA NA NA NA
Scott Reef South 3 1.5 17 24 2.5 61 12 715 <1 8
Seringapatam Reef* 3.5 <1 38 45 NA NA NA NA NA NA
Sumba <1 <1 NC NC <1 NC NC NC NC NC
Ashmore Reef <1 <1 NC NC <1 NC 0.1 15 <1 <1
Big Bank Shoals* <1 <1 NC NC NA NA NA NA NA NA
Camden Sound <1 <1 NC NC <1 NC NC NC NC NC
Cartier Island <1 <1 NC NC <1 NC <0.1 13 <1 <1 Dampier Peninsula Coast - Mid <1 <1 NC NC <1 NC NC NC NC NC Section Dampier Peninsula Coast - North <1 <1 NC NC <1 NC NC NC NC NC Section Lalang-garram - Camden Sound <1 <1 NC NC <1 NC NC NC NC NC Marine Park
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Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation Rowley Shoals - Clerke Reef <1 <1 NC NC <1 NC <0.1 11 <1 <1
Rowley Shoals - Imperieuse Reef <1 <1 NC NC <1 NC <0.1 4.8 <1 <1
Rowley Shoals - Mermaid Reef <1 <1 NC NC <1 NC NC NC NC NC
Sahul Banks* <1 <1 NC NC NA NA NA NA NA NA
Savu <1 <1 NC NC <1 NC NC NC NC NC
Scott Reef Central 1 <1 50 NC 2.5 61 12 715 <1 8
Scott Reef Central - Sandy Islet 1 <1 60 NC 2.5 61 12 715 <1 8
Scott Reef North - Flats* 11.5 4.5 7 8 NA NA NA NA NA NA
Scott Reef North - Lagoon* 8.5 2.5 9 11 NA NA NA NA NA NA
Scott Reef South - Flats* 2.5 1 22 31 NA NA NA NA NA NA
Scott Reef South - Lagoon* 3 1.5 19 22 NA NA NA NA NA NA
Adele Island <1 <1 NC NC <1 NC NC NC NC NC
Barracouta Shoal* <1 <1 NC NC NA NA NA NA NA NA
Echuca Shoal* <1 <1 NC NC NA NA NA NA NA NA
Eighty Mile Beach Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Eugene McDermott Shoal* <1 <1 NC NC NA NA NA NA NA NA
Fantome Bank* <1 <1 NC NC NA NA NA NA NA NA PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Heywood Shoal* <1 <1 NC NC NA NA NA NA NA NA
Oceanic Shoals - Deep Shoal 1* <1 <1 NC NC NA NA NA NA NA NA Oceanic Shoals Region - Gale-Favell- <1 <1 NC NC NA NA NA NA NA NA Baldwin Banks* Oceanic Shoals Region - Margaret <1 <1 NC NC NA NA NA NA NA NA Harries Banks* Oceanic Shoals Region - The Boxers* <1 <1 NC NC NA NA NA NA NA NA
Timor Leste <1 <1 NC NC <1 NC NC NC NC NC
Timor West <1 <1 NC NC <1 NC NC NC NC NC
Van Cloon Shoal* <1 <1 NC NC NA NA NA NA NA NA
Vulcan & Goeree Shoals* <1 <1 NC NC NA NA NA NA NA NA
WA Coastline <1 <1 NC NC <1 NC NC NC NC NC
NC: No contact to receptor predicted for specified threshold. NA: Not applicable. * Floating oil will not accumulate on submerged features and at open ocean locations.
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Figure 3.32 Predicted annualised probability of floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.33 Predicted annualised probability of floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.34 Predicted annualised minimum times to contact by floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.35 Predicted annualised minimum times to contact by floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.36 Predicted annualised EMBA of floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.37 Predicted annualised EMBA of floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.38 Predicted annualised probability of shoreline oil concentrations at or above 100 g/m2 resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Table Table 3.4.2.2 REPORT www.rpsgroup.com/mst MAW0815J M Park Mermaid Mermaid M State Reef Imperieuse Argo Coast Coast Peninsula Dampier Cartier Island Sound Camden Shoals Bank Big Reef Ashmore Sumba Reef Seringapatam South Reef Scott North Reef Scott Rowley Shoals Rowley Shoals M State Reef Rowley Shoals Roti Pulau Park Shoals M Oceanic Islands Lacepede Coast Kimberley M Kimberley Boundary Indonesian Indonesia Hibernia Bank Shoals & Rankin Glomar Park Cartier Island M Archipelagos B Browse Island Park M Reef Ashmore Receptor uccaneer & uccaneer Bonaparte Park arine Park arine
-
Rowley Terrace Rowley Terrace -
3 Mid Section . Reef
Reef M
8
|
Entrained Oil Entrained Browse to NWS Project NWS to Browse arine Parkarine
arine Park arine
system failure system failure of release surface instantaneous resulti receptors sensitive at outcomes oil entrained annualised Expected - - -
arine
arine
Clerke arine
arine
Prob
concentration
entrained oil -
Quantitative Spill Risk Assessment Risk Spill Quantitative at the Torosa FPSO location FPSO Torosa at the ≥100 ability of (%) 13.5 7.5 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 28
ppb
receptor (hours) for Minimum time to to time Minimum entrained oil at entrained oil stabilised stabilised ≥100
310 302 NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC 29 17 | 6
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
ppb
.
|
27 November 2019 November 27 Torosa replicate simulations Maximum averaged overall
Condensate after after Condensate
278 NC NC NC NC NC NC <1 <1 <1 <1 <1 <1 < <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 26 84 1
entrainedconcentration oil (ppb)
at any depth, in the an worst replicate replicate worst simulation FPSO 6,391 1,207 2,935 ng from an from ng 109 121 NC NC NC NC NC NC <1 <1 <1 <1 44 19 17 45 19 17 2 4 4 3 5
offtake
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Probability (%) of Minimum time to entrained oil receptor (hours) for Maximum entrained oil concentration (ppb) concentration entrained oil at Receptor at any depth, in the averaged over all ≥100 ppb ≥100 ppb worst replicate replicate simulations simulation Dampier Peninsula <1 NC <1 <1 Coast - North Section Lalang-garram - Camden <1 NC <1 <1 Sound Marine Park Rowley Shoals - Clerke <1 NC <1 4 Reef Rowley Shoals - <1 NC <1 4 Imperieuse Reef Rowley Shoals - <1 NC <1 2 Mermaid Reef Sahul Banks <1 NC <1 2
Savu <1 NC <1 2
Scott Reef Central 9.5 31 31 973 Scott Reef Central - 8.5 35 31 879 Sandy Islet Scott Reef North - Flats 25 7 232 6,391 Scott Reef North - 20 10 95 2,979 Lagoon Scott Reef South - Flats 9 22 40 1,916 Scott Reef South - 14.5 18 83 2,887 Lagoon Adele Island <1 NC <1 <1
Barracouta Shoal <1 NC <1 52
Echuca Shoal <1 NC <1 12 Eighty Mile Beach <1 NC NC NC Marine Park Eugene McDermott <1 NC <1 10 Shoal Fantome Bank <1 NC <1 8
Heywood Shoal <1 NC <1 18 Oceanic Shoals - Deep <1 NC NC NC Shoal 1 Oceanic Shoals Region - Gale-Favell-Baldwin <1 NC NC NC Banks Oceanic Shoals Region - <1 NC NC NC Margaret Harries Banks Oceanic Shoals Region - <1 NC NC NC The Boxers Timor Leste <1 NC NC NC
Timor West <1 NC NC NC
Van Cloon Shoal <1 NC NC NC
Vulcan & Goeree Shoals <1 NC <1 15
WA Coastline <1 NC <1 2
NC: No contact to receptor predicted for specified threshold. * Probabilities and maximum concentrations calculated at depth of submerged feature. udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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Figure 3.39 Predicted annualised probability of entrained oil concentrations at or above 100 ppb resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.40 Predicted annualised minimum times to contact by entrained oil concentrations at or above 100 ppb resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.41 Predicted annualised EMBA of entrained oil concentrations at or above 100 ppb resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.42 Cross-section transects of predicted annualised maximum entrained oil concentrations for an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location. Transect locations are shown in Figure 3.1.
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Table Table 3.4.2.3 REPORT www.rpsgroup.com/mst MAW0815J Sound M Sound Park Rowley Shoals Rowley Shoals Lalang Section North Coast Peninsula Dampier Section Coast Peninsula Dampier Cartier Island Sound Camden B Big Reef Ashmore Sumba Reef Seringapatam South Reef Scott North Reef Scott M Rowley Shoals M State Reef Rowley Shoals State M Rowley Shoals Roti Pulau Shoals M Oceanic Islands Lacepede Coast Kimberley M Kimberley Boundary Indonesian Indonesia Hiberni Shoals & Rankin BankGlomar Cartier Island M Archipelagos & Bonaparte Buccaneer Browse Island M Reef Ashmore Receptor Argo Park arine
- ank Shoals Rowley Terrace M Rowley Terrace - a Reef 3
garram garram Park arine . Park arine
9
|
Dissolve Browse to NWS Project NWS to Browse arine Parkarine
arine Park arine
resulting from an instantaneous surface release of of release surface instantaneous an from resulting receptors sensitive at outcomes hydrocarbon aromatic dissolved annualised Expected FP - - - - -
arine Parkarine
Camden Camden Clerke Reef Clerke ReefMermaid Imperieuse Reef Clerke Park arine
Park arine SO
offtake system failure failure system offtake arine d AromaticHydrocarbon
- -
Mid
-
Quantitative Spill Risk Assessment Risk Spill Quantitative Probability (%) of aromatic hydrocarbon concentration ≥50 11.5 7.5 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 23
ppb
at the Torosa FPSO location FPSO Torosa at the
dissolved dissolved
s | PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Rev 4 averaged overall replicate Maximum dissolved aromatic hydrocarbonconcentration
| 27 November 2019 November 27 simulations NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC <1 <1 <1 <1 <1 <1 <1 <1 <1 13 36 76 stabilised
.
Torosa (ppb)
at any depth, in th replicate simulation replicate Condensate after after Condensate 1,249 1,791 881 NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC <1 <1 11 54 24 7 9 9 5
e worst e worst Page
an
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Probability (%) of dissolved Maximum dissolved aromatic hydrocarbon concentration aromatic hydrocarbon (ppb) Receptor concentration averaged over all replicate at any depth, in the worst ≥50 ppb simulations replicate simulation Rowley Shoals - Imperieuse <1 NC NC Reef Rowley Shoals - Mermaid Reef <1 <1 <1
Sahul Banks <1 NC NC
Savu <1 NC NC
Scott Reef Central 7.5 12 971
Scott Reef Central - Sandy Islet 7.5 10 516
Scott Reef North - Flats 22.5 69 1,749
Scott Reef North - Lagoon 15.5 42 1,791
Scott Reef South - Flats 9 19 961
Scott Reef South - Lagoon 11 30 1,166
Adele Island <1 <1 <1
Barracouta Shoal <1 <1 <1
Echuca Shoal <1 <1 <1
Eighty Mile Beach Marine Park <1 NC NC
Eugene McDermott Shoal <1 <1 <1
Fantome Bank <1 <1 <1
Heywood Shoal <1 <1 <1
Oceanic Shoals - Deep Shoal 1 <1 NC NC Oceanic Shoals Region - Gale- <1 NC NC Favell-Baldwin Banks Oceanic Shoals Region - <1 NC NC Margaret Harries Banks Oceanic Shoals Region - The <1 NC NC Boxers Timor Leste <1 NC NC
Timor West <1 NC NC
Van Cloon Shoal <1 NC NC
Vulcan & Goeree Shoals <1 <1 2
WA Coastline <1 <1 <1
NC: No contact to receptor predicted for specified threshold. * Probabilities and maximum concentrations calculated at depth of submerged feature.
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PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.43 Predicted annualised probability of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.44 Predicted annualised minimum times to contact by dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.45 Predicted annualised EMBA of dissolved aromatic hydrocarbon concentrations at or above 50 ppb resulting from an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location.
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Figure 3.46 Cross-section transects of predicted annualised maximum dissolved aromatic hydrocarbon concentrations for an instantaneous surface release of stabilised Torosa Condensate after an FPSO offtake system failure at the Torosa FPSO location. Transect locations are shown in Figure 3.1.
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( that concentrati cross The threshold concentration are depict are concentration threshold The forecast annualised minimum times to andcontact times minimum annualised forecast The pr State State equal to or greater greater or equalto M T Given that the spill location lies within the Argo within the lies spillGiven that location the is predicted to be contacted by floating oil concentrations at the 10 at the oil concentrations by floating contacted be to is predicted Contact by entrained oil at concentratio entrained Contact by M around 371 around ( in excess of the 100 of in excess collision shorelines is predicted to be low, with a maximum acc a maximum with low, be to is predicted shorelines threshold could potentially be found, in the form of slicks, up8 to slicks, of form the in be found, potentially could threshold threshold concentration threshold contact of less than 1 than less of contact – floating oil contact at the 10 at the oil contact floating a The probability contour figures for floating oil indicate that concentrations equal to or greater than the 10 the than orgreater to equal concentrations that indicate oil floating for figures contour probability The 3.5.1.2 sur to exposure of probability the investigated scenario This 3.5.1.1 3.5.1 3.5 REPORT www.rpsgroup.com/mst MAW0815J 500 the than greater or to equal concentrations oil at Entrained 3.5.1.3 Rowley Shoals Rowley Shoals The Rowley Shoals Shoals Rowley The of days to weeks days to of low The atmosphere. the to exposure t likely are oil the (40.6%) of volatile fractions the release, the surface During of time as residual as oil. time of Figure 3 instantaneous
he forecast annualised minimum times to contact times annualised minimum he forecast Clerke arine Park arine arine Park and Rowley Shoals Shoals and Rowley Park arine edicted as 167.6 as edicted corresponding minimum corresponding
M
arine Park arine
near the Rowley Shoals during operations at any time of year, with no mitigation measu year, no with mitigation of anytime at operations during Shoals Rowley the near Reef State State Reef . |
57). - Scenario 4: Short 4: Scenario Discussion of Results Discussion Floating and Shoreline and Floating Oil Overview Entrained Oil Entrained the Rowley Shoals the Rowley Die of Marine Browse to NWS Project NWS to Browse sectional transects of maximum entrained oil entrainedoil of maximum transects sectional
km
(57%), Rowley Shoals Shoals Rowley (57%),
) surface release of 2,000 of release surface )
ons above 25,000 above ons – from the spill ( site from
to evaporate, and the remaining fraction (5.0%) is expected to persist for an extended period period an extended for persist to is expected (5.0%) fraction remaining the and to evaporate, Mermaid Reef Reef Mermaid
than 100 than (7.5%; ppm at Argo ppm – M
g/m Mermaid Reef Reef Mermaid
hour ( hour arine Park arine
s
2 2 are depicted in are depicted
threshold with a probability of 1% ( 1% of probability with thresholda Table Table
contact
-
Ta g/m Quantitative Spill Risk Assessment Risk Spill Quantitative g/m ble - 2 2 Rowley Terrace Terrace Rowley M
3
sel after a Vessel Fuel Tank Rupture near Rupture Tank Fuel afterVessel a sel
and a maximum local accumulated concentration of 491 of concentration local accumulated a maximum and threshold are forecast to be 1% or less. 1% to be are forecast threshold
is forecast at this receptor with a probability of 100% and a minimum time to time a minimum and 100% of probability with a at this receptor is forecast . – F ed in ed ppb are expected to extend from the sea surface to depths of around 20 around of depths to the surface sea from extend to expected are ppb arine Parkarine
3 11 times of 5 hours 5 hours of times
igure igure . M Imperieuse Reef State Reef Imperieuse – ). The Rowley Shoals Shoals Rowley The 10). ). The ma The ). -
arine Park arine volatility fraction of the diesel (54.4%) will take longer times of the order the order of times longer will take diesel (54.4%) the of fraction volatility Mermaid Reef Reef Mermaid ns equal to or greater than 500 than greater or equal to ns
Figure Figure
- Figure Figure 3
Term (Instantaneous) Surface Release Surface (Instantaneous) Term m
. 54).
3
( of marine diesel after a vessel fuel tank rupture tank fuel a vessel after diesel of marine - Ta 3 Rowley Terrace Rowley Terrace
ximum entrained oil concentration forecast for any receptor is any receptor for forecast oil concentration entrained ximum 3 .
55 ble receptor is receptor M .
49 and arine Park arine and and 3
(
to M Ta . | umulated volume of 6 of volume umulated 10 EMBA EMBA
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 arine arine Figure Figure ble ble Figure Figure concentrations in the vicinity of the release site show show site the release vicinityof in the concentrations ).
EMBA EMBA
rounding regions by oil resulting from a short resultingfrom oil by rounding regions predicted to experience shoreline oil accumulation accumulation oil shoreline experience to predicted 3 M | Park . . – Ta for floating oil at or above the above at or oil floating for 27 November 2019 November 27 10).
arine Park shoreline receptors, probabilities receptors, shoreline Park arine 3
M M 3 . ble
52 . 2 ppb arine Park arine Park ermaid Reef Reef ermaid 56,
for entrained oil at or above the 500 the above at or oil entrained for (33.5%) and Rowley Shoals Shoals (33.5%) Rowley and At the At Shoals the Rowley km from the spill s from km g/m .
3
respectively. . threshold threshold ppb is predicted at Argo at is predicted ppb 10 2
threshold with probabilit threshold ). Potential for accumulation of oil on oil on of accumulation for Potential ).
area, floating oil at oilco area, floating m 3 M o evaporate within 24 hours of hours within 24 o evaporate
is forecast at the Rowley Shoals Rowley at the forecast arine Parkarine
predicted to be found up to to up found be to predicted ite
( Figure 3 Figure –
g/m
1
shor Clerke Reef State State Reef Clerke
g/m - Rowley Terrace Terrace Rowley 2
forecast at the at the forecast – from a vessel from y eline receptor receptor eline 2 res applied. res
.
ncentrations ncentrations of 15%, of Clerke Reef Reef Clerke and 48).
10 Page -
g/m g/m
term
with ppb ppb
m of of
125 2 2
1931 10D Tech nTeicalchnical St udiStudieses 1932 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
3.5.1.4 Dissolved Aromatic Hydrocarbons Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 500 ppb threshold are predicted to be found up to around 43 km from the spill site (Figure 3.58). Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 500 ppb is predicted at Argo-Rowley Terrace Marine Park (8.5%) and Rowley Shoals – Mermaid Reef Marine Park (1.5%; Table 3.12). The maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as 2.2 ppm at Argo-Rowley Terrace Marine Park. The forecast annualised minimum times to contact and EMBA for dissolved aromatic hydrocarbons at or above the 500 ppb threshold concentration are depicted in Figure 3.59 and Figure 3.60, respectively. The cross-sectional transects of maximum dissolved aromatic hydrocarbon concentrations in the vicinity of the release site show that concentrations above 2,000 ppb are expected to extend from the sea surface to depths of around 10 m (Figure 3.61).
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3.5.2 Results Tables and Figures
3.5.2.1 Floating and Shoreline Oil
Table 3.10 Expected annualised floating and shoreline oil outcomes at sensitive receptors resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation
Argo-Rowley Terrace Marine Park * 100 100 1 1 NA NA NA NA NA NA
Ashmore Reef Marine Park <1 <1 NC NC <1 NC NC NC NC NC
Browse Island* <1 <1 NC NC NA NA NA NA NA NA
Buccaneer & Bonaparte Archipelagos <1 <1 NC NC <1 NC NC NC NC NC
Cartier Island Marine Park <1 <1 NC NC <1 NC NC NC NC NC
Glomar Shoals & Rankin Bank* <1 <1 NC NC NA NA NA NA NA NA
Hibernia Reef* <1 <1 NC NC NA NA NA NA NA NA
Indonesia <1 <1 NC NC <1 NC NC NC NC NC
Indonesian Boundary <1 <1 NC NC <1 NC NC NC NC NC
Kimberley Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Kimberley Coast <1 <1 NC NC <1 NC NC NC NC NC PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Lacepede Islands <1 <1 NC NC <1 NC NC NC NC NC
Oceanic Shoals Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Pulau Roti <1 <1 NC NC <1 NC NC NC NC NC Rowley Shoals - Clerke Reef State 1.5 1 35 37 <1 76 2.9 438 <1 6 Marine Park Rowley Shoals - Imperieuse Reef <1 <1 NC NC <1 NC 0.4 17 <1 <1 State Marine Park Rowley Shoals - Mermaid Reef 23 15 5 5 1 100 5 491 <1 5 Marine Park Scott Reef North* <1 <1 NC NC NA NA NA NA NA NA
Scott Reef South <1 <1 NC NC <1 NC <0.1 2 <1 <1
Seringapatam Reef* <1 <1 NC NC NA NA NA NA NA NA
Sumba <1 <1 NC NC <1 NC NC NC NC NC
Ashmore Reef <1 <1 NC NC <1 NC NC NC NC NC
Big Bank Shoals* <1 <1 NC NC NA NA NA NA NA NA
Camden Sound <1 <1 NC NC <1 NC NC NC NC NC
Cartier Island <1 <1 NC NC <1 NC NC NC NC NC Dampier Peninsula Coast - Mid <1 <1 NC NC <1 NC NC NC NC NC Section Dampier Peninsula Coast - North <1 <1 NC NC <1 NC NC NC NC NC Section Lalang-garram - Camden Sound <1 <1 NC NC <1 NC NC NC NC NC Marine Park
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Technical Studies 1934 PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERD REPORT
Probability (%) of Minimum time to Minimum time to receptor (hours) for Maximum local accumulated concentration Maximum accumulated volume (m3) along Probability (%) of floating oil concentration shoreline oil receptor (hours) for floating oil at (g/m2) this shoreline Receptor concentration shoreline oil at averaged over all in the worst replicate averaged over all in the worst replicate ≥1 g/m2 ≥10 g/m2 ≥1 g/m2 ≥10 g/m2 ≥100 g/m2 ≥100 g/m2 replicate simulations simulation replicate simulations simulation Rowley Shoals - Clerke Reef <1 <1 68 74 <1 76 2.9 438 <1 6
Rowley Shoals - Imperieuse Reef <1 <1 NC NC <1 NC 0.4 17 <1 <1
Rowley Shoals - Mermaid Reef 8 4 16 17 1 100 5 491 <1 5
Sahul Banks* <1 <1 NC NC NA NA NA NA NA NA
Savu <1 <1 NC NC <1 NC NC NC NC NC
Scott Reef Central <1 <1 NC NC <1 NC <0.1 2 <1 <1
Scott Reef Central - Sandy Islet <1 <1 NC NC <1 NC <0.1 2 <1 <1
Scott Reef North - Flats* <1 <1 NC NC NA NA NA NA NA NA
Scott Reef North - Lagoon* <1 <1 NC NC NA NA NA NA NA NA
Scott Reef South - Flats* <1 <1 NC NC NA NA NA NA NA NA
Scott Reef South - Lagoon* <1 <1 NC NC NA NA NA NA NA NA
Adele Island <1 <1 NC NC <1 NC NC NC NC NC
Barracouta Shoal* <1 <1 NC NC NA NA NA NA NA NA
Echuca Shoal* <1 <1 NC NC NA NA NA NA NA NA
Eighty Mile Beach Marine Park * <1 <1 NC NC NA NA NA NA NA NA
Eugene McDermott Shoal* <1 <1 NC NC NA NA NA NA NA NA
Fantome Bank* <1 <1 NC NC NA NA NA NA NA NA
Heywood Shoal* <1 <1 NC NC NA NA NA NA NA NA
Oceanic Shoals - Deep Shoal 1* <1 <1 NC NC NA NA NA NA NA NA Oceanic Shoals Region - Gale-Favell- <1 <1 NC NC NA NA NA NA NA NA Baldwin Banks* Oceanic Shoals Region - Margaret <1 <1 NC NC NA NA NA NA NA NA Harries Banks* Oceanic Shoals Region - The Boxers* <1 <1 NC NC NA NA NA NA NA NA
Timor Leste <1 <1 NC NC <1 NC NC NC NC NC
Timor West <1 <1 NC NC <1 NC NC NC NC NC
Van Cloon Shoal* <1 <1 NC NC NA NA NA NA NA NA
Vulcan & Goeree Shoals* <1 <1 NC NC NA NA NA NA NA NA
WA Coastline <1 <1 NC NC <1 NC NC NC NC NC
NC: No contact to receptor predicted for specified threshold. NA: Not applicable. * Floating oil will not accumulate on submerged features and at open ocean locations.
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REPORT
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.47 Predicted annualised probability of floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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Figure 3.48 Predicted annualised probability of floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.49 Predicted annualised minimum times to contact by floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
Figure 3.50 Predicted annualised minimum times to contact by floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.51 Predicted annualised smoothed EMBA of floating oil concentrations at or above 1 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
Figure 3.52 Predicted annualised smoothed EMBA of floating oil concentrations at or above 10 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.53 Predicted annualised probability of shoreline oil concentrations at or above 100 g/m2 resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
3.5.2.2 Entrained Oil
Table 3.11 Expected annualised entrained oil outcomes at sensitive receptors resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
Probability (%) of Minimum time to entrained oil receptor (hours) for Maximum entrained oil concentration (ppb) concentration entrained oil at Receptor at any depth, in the averaged over all ≥500 ppb ≥500 ppb worst replicate replicate simulations simulation Argo-Rowley Terrace 57 1 13,271 167,600 Marine Park Ashmore Reef Marine <1 NC NC NC Park Browse Island <1 NC NC NC Buccaneer & Bonaparte <1 NC NC NC Archipelagos Cartier Island Marine <1 NC NC NC Park Glomar Shoals & Rankin <1 NC <1 81 Bank Hibernia Reef <1 NC NC NC
Indonesia <1 NC NC NC
Indonesian Boundary <1 NC NC NC
Kimberley Marine Park <1 NC 5 423
Kimberley Coast <1 NC NC NC
Lacepede Islands <1 NC NC NC Oceanic Shoals Marine <1 NC NC NC Park Pulau Roti <1 NC NC NC Rowley Shoals - Clerke 7.5 26 182 11,204 Reef State Marine Park Rowley Shoals - Imperieuse Reef State 2.5 86 35 3,019 Marine Park Rowley Shoals - Mermaid Reef Marine 33.5 7 2,420 38,749 Park Scott Reef North <1 NC <1 84
Scott Reef South <1 NC 2 125
Seringapatam Reef <1 NC <1 13
Sumba <1 NC NC NC
Ashmore Reef <1 NC NC NC
Big Bank Shoals <1 NC NC NC
Camden Sound <1 NC NC NC
Cartier Island <1 NC NC NC Dampier Peninsula NC NC NC 1> Coast - Mid Section udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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REPORT www.rpsgroup.com/mst MAW0815J of at depth calculated feature. and submerged concentrations maximum Probabilities * threshold. specified for predicted receptor to No contact NC: Lagoon Banks Lagoon Merm Reef Imperieuse Sound Dampier Peninsula Peninsula Dampier WA Coastline WA & Goeree Vulcan Shoal Cloon Van West Timor Leste Timor BoxersThe Shoals Region Oceanic Banks Margaret Harries Shoals Region Oceanic Gale Shoals Oceanic 1 Shoal Shoals Oceanic Heywood Shoal Bank Fantome Shoal McDermott Eugene M Beach Mile Eighty Shoal Echuca Shoal Barracouta Adele Island South Reef Scott South Reef Scott North Reef Scott North Reef Scott Sandy Central Reef Scott Central Reef Scott Savu Banks Sahul Rowley Shoals Rowley Shoals Reef Rowley Shoals Lalang Coast Receptor Park arine -
Favell aid Reef aid
- - Islet M
garram garram
North Section North Park arine
|
-
Browse to NWS Project NWS to Browse Baldwin
- - - -
Region Region -
Camden Camden
Clerke
- -
- - Shoals Deep
Flats Flats -
- - -
Probability (%) of
concen entrained oil -
Quantitative Spil Quantitative ≥500 21.5 6.5 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 2
tratio
ppb
n
l Risk Assessment l Risk receptor (hours) for Minimum time to to time Minimum
entrained oil at entrained oil ≥500
129 NC N NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC 17 39 | C
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 ppb
|
27 November 2019 November 27 replicate simulations Maximum entrained oil concentration(ppb) averaged overall
893 122 NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC <1 <1 <1 <1 <1 <1 35 2
at any depth, in the worst replicate replicate worst simulation 14,365 3,019 9,363 125 105 NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC <1 81 84 88 96
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1943 10D Tech nTeicalchnical St udiStudieses 10D
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REPORT
Figure 3.54 Predicted annualised probability of entrained oil concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.55 Predicted annualised minimum times to contact by entrained oil concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
Figure 3.56 Predicted annualised smoothed EMBA of entrained oil concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019 www.rpsgroup.com/mst Page 140
REPORT www.rpsgroup.com/mst MAW0815J Figure Figure 3
. |
57 Browse to NWS Project NWS to Browse
the Rowley Shoals. Transect locations are shown in shown are locations Transect Shoals. Rowley the s instantaneous an for Cross - section transects of predicted annualised maximum entrained oil concentrations oil concentrations entrained maximum annualised predicted of transects section
-
Quantitative Spill Risk Assessment Risk Spill Quantitative
urface release of marine diese marine of release urface
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 November 2019 November 27 Figure l after a vessel fuel tank rupture near near rupture tank fuel a vessel after l
3 . 1 .
Page
141
1947 10D Tech nTeicalchnical St udiStudieses 1948 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
3.5.2.3 Dissolved Aromatic Hydrocarbons
Table 3.12 Expected annualised dissolved aromatic hydrocarbon outcomes at sensitive receptors resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
Probability (%) of dissolved Maximum dissolved aromatic hydrocarbon concentration aromatic hydrocarbon (ppb) Receptor concentration averaged over all replicate at any depth, in the worst ≥500 ppb simulations replicate simulation Argo-Rowley Terrace Marine 8.5 141 2,214 Park Ashmore Reef Marine Park <1 NC NC Browse Island <1 NC NC Buccaneer & Bonaparte <1 NC NC Archipelagos Cartier Island Marine Park <1 NC NC Glomar Shoals & Rankin Bank <1 <1 <1 Hibernia Reef <1 NC NC Indonesia <1 NC NC Indonesian Boundary <1 NC NC Kimberley Marine Park <1 <1 3 Kimberley Coast <1 NC NC Lacepede Islands <1 NC NC Oceanic Shoals Marine Park <1 NC NC Pulau Roti <1 NC NC Rowley Shoals - Clerke Reef <1 4 309 State Marine Park Rowley Shoals - Imperieuse <1 <1 134 Reef State Marine Park Rowley Shoals - Mermaid Reef 1.5 37 910 Marine Park Scott Reef North <1 NC NC Scott Reef South <1 NC NC Seringapatam Reef <1 NC NC Sumba <1 NC NC Ashmore Reef <1 NC NC Big Bank Shoals <1 NC NC Camden Sound <1 NC NC Cartier Island <1 NC NC Dampier Peninsula Coast - Mid <1 NC NC Section Dampier Peninsula Coast - <1 NC NC North Section Lalang-garram - Camden <1 NC NC Sound Marine Park Rowley Shoals - Clerke Reef <1 3 309 Rowley Shoals - Imperieuse <1 <1 100 Reef Rowley Shoals - Mermaid Reef <1 18 502 udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
ical www.rpsgroup.com/mst Page 142 n ch e T 10D
REPORT www.rpsgroup.com/mst MAW0815J of at depth calculated feature. and submerged concentrations maximum Probabilities * predicted receptor fo No NC: to contact WA Coastline WA & Shoals Goeree Vulcan Shoal Cloon Van West Timor Leste Timor Boxers Shoals Region Oceanic Banks Margaret Harries Sh Oceanic Favell Shoals Region Oceanic Shoals Oceanic Heywood Shoal Bank Fantome Shoal McDermott Eugene Beach Mile Eighty Shoal Echuca Shoal Barracouta Adele Island South Reef Scott South Reef Scott North Reef Scott North Reef Scott Central Reef Scott Scott Savu Banks Sahul Receptor
Reef Central Reef - Baldwin Banks
|
oals Region
Browse to NWS Project NWS to Browse
-
- -
- - Deep Shoal 1
M Lagoon Flats Lagoon Flats -
Sandy Sandy Park arine
- - -
The Gale
Islet -
-
Quantitative Spill Risk Assessment Risk Spill Quantitative Probability (%) of dissolved aromatic hydrocarbon r specified threshold. specified concentratio ≥500 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1
ppb
n
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 averaged overall replicate Maximum dissolved aromatic hydrocarbonconcentration
| 27 November 2019 November 27 simulations NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC
(ppb)
at any depth, in the worst replicate simulation replicate NC NC NC NC NC NC NC NC N NC NC NC NC NC NC NC NC NC NC NC NC NC NC NC C
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1949 10D Tech nTeicalchnical St udiStudieses 10D
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REPORT
Figure 3.58 Predicted annualised probability of dissolved aromatic hydrocarbon concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
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REPORT
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
Figure 3.59 Predicted annualised minimum times to contact by dissolved aromatic hydrocarbon concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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Technical Studies 1952 PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERD
REPORT
Figure 3.60 Predicted annualised smoothed EMBA of dissolved aromatic hydrocarbon concentrations at or above 500 ppb resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals.
MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019 www.rpsgroup.com/mst Page 146
REPORT www.rpsgroup.com/mst MAW0815J Figure Figure 3
. |
61 Browse to NWS Project NWS to Browse
3 vessel fuel tank rupture near the Rowley Shoals. Transect locatio Transect Shoals. Rowley the near rupture tank fuel vessel hydrocarbon concentrations for an instantaneous surface release of release surface instantaneous an for concentrations hydrocarbon Cross . 1 .
- section transects of predicted annualised maximum dissolved aromatic aromatic dissolved maximum annualised predicted of transects section
-
Quantitative Spill Risk Assessment Risk Spill Quantitative
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
| 27 November 2019 November 27
ns are shown in shown are ns
marine diesel after a a after diesel marine Figure Page
147
1953 10D Tech nTeicalchnical St udiStudieses 1954 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
4 DETERMINISTIC ASSESSMENT RESULTS 4.1 Overview To provide additional context to the outcomes of the stochastic assessment presented in Section 3, deterministic model runs of interest were selected from the stochastic set of replicate simulations for each scenario according to the following criteria: • Minimum time to floating oil contact with the offshore edge(s) of any shoreline receptor polygon (at a threshold of 10 g/m2); • Minimum time to entrained/dissolved oil contact with the offshore edge(s) of any shoreline receptor polygon (at a threshold of 500 ppb); • Minimum time to commencement of oil accumulation at any shoreline receptor (at a threshold of 100 g/m2); • Maximum cumulative oil volume accumulated across all shoreline receptors and at any individual shoreline receptor (at concentrations in excess of 100 g/m2). A time series compilation of figures from each deterministic replicate simulation (i.e. a single spill event) for each scenario is presented in the following sections. Each of the figure compilations includes areal exposure at discrete time intervals during the simulation.
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ical www.rpsgroup.com/mst Page 148 n ch e T 10D www.rpsgroup.com/mst MAW0815J 4.2.1 4.2 REPORT Figure Figure
4
. |
1 ondensate at the TRA the at Condensate Scenario 1: Long 1: Scenario Simulation with with Simulation Thresholds B
rowse to NWS Project NWS to rowse minimum time to commencement of oil accumulation at any shoreline receptor (at a threshold of 100 of athreshold (at receptor shoreline atany oilaccumulation of commencement to time minimum the o a polygonthreshold (at anyreceptor of offshore shoreline edge(s) the with contact oil entrained/dissolved to time minimum - Time with the the with concentrations varying areal extent of potential exposure at potential of varying extent areal minimum tim minimum
-
Quantitative Spill Risk Assessment Risk Spill Quantitative , resulting from a 77 a from resulting M e inimum inimum
to floating oil contact with the offshore edge(s) of any shoreline receptor polygon (at a threshold of 10 of polygona threshold (at receptor anyshoreline of edge(s) withoffshore the oil contact floating to - Term (77 Term T - - C Well ime to day surface/ day
| Rev 4 - Day) Surface/Subsea Blowout of Blowout Surface/Subsea Day)
| 27 November 2019 November 27 Oil Contact andAccumulation atAny Shoreline Receptor at Defined
subsea
defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil oil threshold shoreline and hydrocarbon aromatic oil, dissolved oil, entrained floating defined
release of of release
PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES unstabilised unstabilised Torosa Condensate at the TRA the at Condensate Torosa U nstabilised nstabilised
g/m 2 ) .
- , well C Torosa Torosa for the replicate case case replicate the for f 500 f
g/m
ppb)
2 Page ) , the , the a n
d 149
1955 10D Tech nTeicalchnical St udiStudieses 1956 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
4.2.2 Simulation with Maximum Oil Accumulation across All Shoreline Receptors and at Any Individual Shoreline Receptor at Defined Threshold
Figure 4.2 Time-varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from a 77-day surface/subsea release of unstabilised Torosa Condensate at the TRA-C well, for the replicate case with the maximum cumulative oil volume accumulated across all shoreline receptors and at any individual shoreline receptor (exceeding a threshold of 100 g/m2). udi es t S
MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019 ical www.rpsgroup.com/mst Page 150 n ch e T 10D Figure Figure www.rpsgroup.com/mst MAW0815J 4.3.1 4.3 REPORT
4
. | 3
Scen Simulation with Minimum Time to Floating Oil ContactAny at Shoreline Receptor at Defined Threshold a Vessel Cargo Tank Rupture at the Torosa FPSO Location FPSO Torosa the at Rupture Tank Cargo a Vessel Browse to NWS Project NWS to Browse
- Time threshold of 10 of threshold concentrations location varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreli and hydrocarbon aromatic oil, dissolved oil, entrained floating exposuredefined at potential of varying extent areal ario 2: S ario 2: , for the replicate case with the the with case replicate the for
-
Quantitative Spill Risk Assessment Risk Spill Quantitative
, g/m resulting from a 24 a from resulting hort 2 ) .
- Term (24 Term - hour surface release of of release surface hour
| Rev 4 minimum time to floating oil contact with the offshore edge(s) of any shoreline receptor polygon (at a (at polygon receptor shoreline any of edge(s) offshore the with contact oil floating to time minimum - Hour) Surface Release of Release Surface Hour)
| 27 November 2019 November 27
lised lised stabi PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Tor osa osa Condensate after a vessel cargo tank rupture at the Torosa FPSO Torosa the at rupture tank cargo vessel a after Condensate S tabilised tabilised
Torosa
Condensate after after Condensate ne oil threshold threshold oil ne
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4.3.2 Simulation with Minimum Time to Entrained/Dissolved Oil Contact at Any Shoreline Receptor at Defined Threshold
Figure 4.4 Time-varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location, for the replicate case with the minimum time to entrained/dissolved oil contact with the offshore edge(s) of any shoreline receptor polygon (at a threshold of 500 ppb). udi es t S
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4
. | 5
Simulation with Minimum Time to AccumulationOil at AnyShoreline Receptor at Defined Threshold Browse to NWS Project NWS to Browse
location - Time 100 concentrations g/m varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreli and hydrocarbon aromatic oil, dissolved oil, entrained floating exposuredefined at potential of varying extent areal 2 , ) . for the replicate case with the the with case replicate the for
-
Quantitative Spill Risk Assessment Risk Spill Quantitative , resulting from a 24 a from resulting - hour surface release of of release surface hour
| Rev 4
minimum time to commencement of oil accumulation at any shoreline receptor (at a threshold of of a threshold (at receptor shoreline any at oil accumulation of commencement to time minimum
| 27 Novembe r 2019
stabilised stabilised PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Torosa Torosa C ondensate after a v a after ondensate essel cargo tank rupture at the Torosa FPSO Torosa the at rupture tank cargo essel ne oil threshold threshold oil ne
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4.3.4 Simulation with Maximum Oil Accumulation across All Shoreline Receptors and at Any Individual Shoreline Receptor at Defined Threshold
Figure 4.6 Time-varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from a 24-hour surface release of stabilised Torosa Condensate after a vessel cargo tank rupture at the Torosa FPSO location, for the replicate case with the maximum cumulative oil volume accumulated across all shoreline receptors and at any individual shoreline receptor (exceeding a threshold of 100 g/m2). udi es t S
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4
. |
7 Scenario 3: Short 3: Scenario Shoreline Receptor at Defined Threshold Si after an FPSO Offtake System Fa System Offtake FPSO after an Browse to NWS Project NWS to Browse
individual shoreline receptor (exceeding a threshold of 100 of a threshold (exceeding receptor shoreline individual Torosa FPSO location, FPSO location, Torosa concentrations - Time mulation with Maximum OilAccumulation acrossAll Shoreline Receptors and atAny Individual varying areal
-
Quantitative Spill Risk Assessment Risk Spill Quantitative , resulting from an instantaneous surface release of of release surface instantaneous an from resulting , extent of potential exposure at defined floa exposuredefined at potential of extent for the re the for - Term (Instantaneous) Surface Release of Release Surface (Instantaneous) Term plicate case with the with case plicate
| Rev 4
| 27 November 2019 November 27 ilure at the Torosa FPSO Location FPSO Torosa the ilure at maximum cumulative oil volume accumulated across all shoreline receptors allshoreline across accumulated volume oil cumulative maximum
g/m ting oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold shoreline and hydrocarbon aromatic oil, dissolved oil, entrained ting 2 ) . PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES
stabilised stabilised Torosa
Condensate after after Condensate S tabilised tabilised
an
FPSO offtake system fai system FPSOofftake Torosa
Condensate Condensate
and and lure at the the lure at
at any at any Page
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4.5 Scenario 4: Short-Term (Instantaneous) Surface Release of Marine Diesel after a Vessel Fuel Tank Rupture near the Rowley Shoals 4.5.1 Simulation with Maximum Oil Accumulation across All Shoreline Receptors and at Any Individual Shoreline Receptor at Defined Threshold
Figure 4.8 Time-varying areal extent of potential exposure at defined floating oil, entrained oil, dissolved aromatic hydrocarbon and shoreline oil threshold concentrations, resulting from an instantaneous surface release of marine diesel after a vessel fuel tank rupture near the Rowley Shoals, for the replicate case with the maximum cumulative oil volume accumulated across all shoreline receptors and at any individual shoreline receptor (exceeding a threshold of 100 g/m2). udi es t S
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• • • • • Oil Characteristics • Influences Metocean follows are as study this of findings The main 5 REPORT www.rpsgroup.com/mst MAW0815J • • Figures Contour of Interpretation Results Assessment Stochastic of Summary •
and the remaining 5% would be expected to persist i persist to expected bewould 5% and remaining the days, few a within 54% another hours, 24 around in evaporate to expected be would mass the of 41% atmo to the exposed 4. If Scenario in considered andbeen has components and residual vo highly of withpercentages low hydrocarbons persistent volatile and of a mixture is diesel Marine decayed. until environment marine the in persist to expected be will expecte be will the mass of 78% around exposedto the atmosphere, If hydrocarbons. residual of and proportion a low 3, contain 2 and Scenarios in considered been which has Stabilised respectively. 25%, and 21% 54%, be to expected are proportions these atmosphere, the to exposed to be unstabilised sea the If components. residual and volatile highly of proportions significant a pre is 1 blowout For all hydrocarbon types, the influence of entrainm of influence the types, all hydrocarbon For environment. long wil wind inand variation the conditions drift marked prevailing current with Interactions unstabilised the unstabilised If n. degradatio biological and photochemical to due decayed until environment marine the in persist to expected hours 24 around in evaporate to expected The water surface. the beneath is entrained oil that of trajectory will det currents drift prevailing The conditions. the seasonal of irrespective sites, release release modelled at the spilled short on the influence will a significant complex have reef within the flows Tidal simulation. indivi an of full duration the over predicted coverage overall represent the do outcomes These event. the spill of commencement individ for at concentrations defined exposure of the probability oil predicted out spatial mapped The Large
| - unstabilised
term release. This will be expected to increase th increase to be expected will release. This term CONCLUSION Browse to NWS Project NWS to Browse - scale drift currents willa signi currents have drift scale Torosa
trajectories over the full duration of many individual hydrocarbon spill simulations and indicate indicate and spill simulations hydrocarbon individual of themany full duration over trajectories Torosa Condensate mixture is e is mixture Condensate Torosa
d to evaporate in around 24 hours, another 8% within a few days, and the remaining 14% 14% remaining the and days, few a within 8% another hours, 24 around in evaporate to d Torosa Condensate mixture specified for the sea for specified mixture Condensate Torosa the prevailing wind will provide additional variation in the trajectory of spilled oil, and and oil, spilled of trajectory the in variation additional willwind provide prevailing the
Condensate, which refers to condensate whic to condensate which refers Condensate, - processed condensate that is a mixture of volatilepersisten and of isa mixture that condensate processed
not depict a hydrocarbon slick or plume at any particular instant in time, nor do they donor they in time, instant particular at any plume or slick hydrocarbon a notdepict
-
Quantitative Spill Risk Assessment Risk Spill Quantitative comes of the stochastic assessment for each scenario are an aggregation of the the of an aggregation are each scenario for assessment the stochastic of comes
sites, irrespective of the seasonal conditions. seasonal the of irrespective sites, Torosa Condensate mixture specified for the subsea release phase were phase release subsea the for specified Condensate mixture Torosa S
: ficant influence on the trajectory of any oil spilled at the modelled thespilled any modelled at of oil on the trajectory influence ficant
, another 33% within a few days, and the remaining 51% is is 51% the remaining and days, within a few 33% , another
xposed to the atmosphere, around 17% of the mass is the mass of 17% around atmosphere, to the xposed
| PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4 ent will regulate the degree of mass retention in the in the retention mass of degree the will regulate ent n the marine environment until decayed. until environment marine n the e spread of hydrocarbons during any single event. single any during hydrocarbons of e spread
| 27 November 2019 November 27 s a significant proportion of volatile compounds volatile compounds of proportion a significant s
h has been processed by the FPSO and by and the FPSO processed been h has ual locations at some point in time after time pointin some at locations ual - surface release phase of the release phase of surface
l be expected over the duration of a a of duration the over expected be l
- term trajectoryany of oil term - dual hydrocarbon spill spill dual hydrocarbon surface release phase phase release surface t hydrocarbons with t hydrocarbons sphere, around around sphere,
ermine the the ermine Scenario Scenario Page latile latile
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Scenario 1: Long-Term (77-Day) Surface/Subsea Blowout of Unstabilised Torosa Condensate at the TRA-C Well • The location of the release is adjacent to the Scott Reef system. Most of the predicted impacts from this scenario are focused on the receptors that comprise the Scott Reef system. Note that the set of receptor boundaries that define the Scott Reef system for the purposes of this study have some intentional overlapping areas, and this implies duplicated reporting of some oil impacts. • Floating oil at concentrations equal to or greater than the 10 g/m2 threshold could potentially be found up to 143 km from the spill site. • Floating oil concentrations at the 10 g/m2 threshold are predicted to be focused on the Scott Reef system. Floating oil at 10 g/m2 reaches Scott Reef North in all replicate simulations, but as Scott Reef North is treated as a submerged feature floating oil is predicted to drift over rather than make direct contact with this receptor. Scott Reef Central – Sandy Islet is treated as an emergent feature. This receptor is predicted to be contacted by floating oil concentrations of 10 g/m2 with a probability of 8% and a minimum time to contact of 46 hours after commencement of release. • The Scott Reef Central – Sandy Islet receptor is predicted to experience shoreline oil accumulation in excess of the 100 g/m2 threshold with a probability of 92%. With regard to shoreline receptors further from the release location, Cartier Island (22%) and Ashmore Reef (18%) are predicted to have the highest probabilities of shoreline oil accumulation in excess of the 100 g/m2 threshold. • Potential for accumulation of oil on shorelines is predicted to be significant for Scott Reef Central – Sandy Islet, with a maximum accumulated volume of 827 m3 and a maximum local accumulated concentration of 34.3 kg/m2. The predicted zone of shoreline impact is restricted to Sandy Islet. Note that the boundaries of two other receptors, Scott Reef Central and Scott Reef South, overlap with the same shoreline as Scott Reef Central – Sandy Islet so reported accumulations for these receptors are a duplication. • Entrained oil at concentrations equal to or greater than the 100 ppb threshold is predicted to be found up to approximately 863 km from the spill site. • Contact by entrained oil at concentrations equal to or greater than 100 ppb is generally predicted for Scott Reef receptors including Scott Reef North (100%). Seringapatam Reef is also predicted to be contacted at 100 ppb (87%). • The maximum entrained oil concentration forecast for any receptor is predicted as 23.6 ppm at Scott Reef North. • Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 50 ppb threshold are predicted to be found up to around 673 km from the spill site. • Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 50 ppb is generally predicted for Scott Reef receptors including Scott Reef North (100%). Seringapatam Reef is also predicted to be contacted at 50 ppb (85%). • The maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as 13.9 ppm at Scott Reef North.
Scenario 2: Short-Term (24-Hour) Surface Release of Stabilised Torosa Condensate after a Vessel Cargo Tank Rupture at the Torosa FPSO Location • The location of the release is adjacent to the Scott Reef system. Most of the predicted impacts from this scenario are focused on the receptors that comprise the Scott Reef system. • Floating oil at concentrations equal to or greater than the 10 g/m2 threshold could potentially be found up
.to 126 km from the spill site udi es t S MAW0815J | Browse to NWS Project - Quantitative Spill Risk Assessment | Rev 4 | 27 November 2019
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• • • • FPSO Location • REPORT www.rpsgroup.com/mst MAW0815J • • Torosa Scenario 3: Short • • • • • • • • predicted for Scott Reef receptors including Scott Reef North ( North Reef Scott including receptors Scott Reef for predicted Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 50 than greater or equal to at concentrations hydrocarbons aromatic dissolved by Contact 100 12.7 as is predicted receptor any for forecast concentration hydrocarbon dissolved aromatic maximum The predicted to be contacted contacted be to predicted predicted to be found up to around around up to found be to predicted 50 the than greater or to equal at concentrations hydrocarbons aromatic Dissolved oil released. of volume total the than day one in oil released of the rate to around to around oil concentrations at the 10 the at oil concentrations floating by contacted be to predicted are receptors shoreline Central Reef Scott and South Scott Reef The 100 Central Central Scott Reef and Central Reef Scott South, Reef Scott the by encompassed shoreline, Scott Reef The a 1.5% m and of a probability with threshold Reef North receptor is close enough to the release site that that site release the to enough close is receptor North Reef to 67 Floating oil c oil Floating Floating oil at concentrations concentrations at oil Floating system. Reef Scott the comprise that receptors the on are focused scenario this from ofimpacts Most the predicted system. Scott Reef is adjacent to the the release location of The to around to around Entrained shoreline receptors. higher release rate in Scenario 2 (18,000 Scenario ratein release higher of volume total wherea larger 1, in Scenario forecast concentration than maximum the is greater result North. This The maximum entrained oil concentration forecast for any receptor is predicted as 30.5 as is predicted any receptor for forecast concentration entrained oil The maximum at 1 Reef receptors including Scott Reef North (4 North Reef Scott including receptors Reef than greater or equal to oil at concentrations entrained Contact by Entrained oil at concentrations equal to or greater than the or greater than equal to oil at concentrations Entrained Central Reef Scott and Central Scott Reef South, volume volume accumulated maximum with a be moderate, to is predicted on oil shorelines of accumulation for Potential of 8 of volume accumulated a maximum with low, be to predicted is oil shorelines on of accumulation for Potential receptors, the corresponding minimum times to contact at this threshold are 21 hours and 57 hours. and 57 21 hours are threshold to at contact times this minimum corresponding the receptors, Scott Ree and Central Reef Scott South, Reef Scott shoreline, a common that share receptors Reef three Scott The The Scott Reef South receptor is predicted to be contacted by floating oil concentrations at the 10 oil concentrations by floating contacted to be ispredicted South Scott Reef receptor The
00 |
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Browse to NWS Project NWS to Browse km from the spill site. from km
Condensate after an FPSO Offtake 3 ppb ( ppb
of 212 of – 2 2 and a maximum local accumulated concentration of 715 of local concentration accumulated and amaximum
threshold with a probability of 20.5%. of probability a with threshold threshold wit Central f 890 242 Sandy Islet receptors, is predicted to experience shoreline oil accumulation in excess of the of in excess accumulation oil shoreline experience to is predicted receptors, Islet Sandy oil at c oil is re is oil 22.5 ions at the 10 at the ions oncentrat
km from the spill site. from km m km from the spill site. from km %). 3 oncentrations equal to or greater than the or greater than equal to oncentrations
and a maximum local accumulated concentration of 9.5 of concentration local accumulated and amaximum
leased. The difference in maximum entrained oil concentration is attributable to the to the isattributable entrained oil concentration in difference maximum The leased. –
Sandy Islet, are predicted to experience shoreline oil accumulation in excess of the the of in excess accumulation oil shoreline experience to predicted Islet, are Sandy - h a proba a h Term (Instantaneous) Surface Release of -
Quantitative Spill Risk Asses Risk Spill Quantitative at 50 at
g/m equal to to equal
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| – PROPOSED BROWSE TO NWS PROJECT –DRAFTEIS/ERDAPPENDICES Rev 4
Sandy Islet receptors. Islet Sandy ntact time of 24 hours. of time ntact
| 27 November 2019 November 27 ities of of ities
1 1 System F the peak peak the
00 00 g/m
ppb threshold is pred threshold ppb ppb threshold is predicted to be found up found up to be is predicted threshold ppb 2
1 threshold could potentially be found up up found be potentially could threshold 6.5% At respectively. 6.5% and 2%, these 00 41.5
concentration is influenced more by more influenced is concentration g/m
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159 2
1965 10D Tech nTeicalchnical St udiStudieses 1966 PROPOSED BROWSE TO NWS PROJECT – DRAFT EIS/ERD
REPORT
• Contact by entrained oil at concentrations equal to or greater than 100 ppb is predicted at various northern Scott Reef receptors, including Scott Reef North (28%), Scott Reef North – Flats (25%) and Scott Reef North – Lagoon (20%). • The maximum entrained oil concentration forecast for any receptor is predicted as 6.4 ppm at Scott Reef North and Scott Reef North – Flats. • Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 50 ppb threshold are predicted to be found up to around 271 km from the spill site. • Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 50 ppb is predicted at Scott Reef North (23%) and Scott Reef North – Flats (22.5%). • The maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as 1.8 ppm at Scott Reef North and Scott Reef North – Lagoon.
Scenario 4: Short-Term (Instantaneous) Surface Release of Marine Diesel after a Vessel Fuel Tank Rupture near the Rowley Shoals • The location of the release is adjacent to Mermaid Reef. Most of the predicted impacts from this scenario are focused in the vicinity of the Rowley Shoals. • Floating oil at concentrations equal to or greater than the 10 g/m2 threshold could potentially be found up to 82 km from the spill site. • Given that the spill location lies within the Argo-Rowley Terrace Marine Park area, floating oil at concentrations equal to or greater than 10 g/m2 is forecast at this receptor with a probability of 100% and a minimum time to contact of less than 1 hour. The Rowley Shoals – Mermaid Reef Marine Park shoreline receptor is predicted to be contacted by floating oil concentrations at the 10 g/m2threshold with a probability of 15%, with a corresponding minimum contact time of 5 hours. At the Rowley Shoals – Clerke Reef State Marine Park and Rowley Shoals – Imperieuse Reef State Marine Park shoreline receptors, probabilities of floating oil contact at the 10 g/m2 threshold are forecast to be 1% or less. • The Rowley Shoals – Mermaid Reef Marine Park receptor is predicted to experience shoreline oil accumulation in excess of the 100 g/m2 threshold with a probability of 1%. • Potential for accumulation of oil on shorelines is predicted to be low, with a maximum accumulated volume of 6 m3 forecast at the Rowley Shoals – Clerke Reef State Marine Park and a maximum local accumulated concentration of 491 g/m2 forecast at the Rowley Shoals – Mermaid Reef Marine Park. • Entrained oil at concentrations equal to or greater than the 500 ppb threshold is predicted to be found up to around 371 km from the spill site. • Contact by entrained oil at concentrations equal to or greater than 500 ppb is predicted at Argo-Rowley Terrace Marine Park (57%), Rowley Shoals – Mermaid Reef Marine Park (33.5%) and Rowley Shoals – Clerke Reef State Marine Park (7.5%). • The maximum entrained oil concentration forecast for any receptor is predicted as 167.6 ppm at Argo- Rowley Terrace Marine Park. • Dissolved aromatic hydrocarbons at concentrations equal to or greater than the 500 ppb threshold are predicted to be found up to around 43 km from the spill site. • Contact by dissolved aromatic hydrocarbons at concentrations equal to or greater than 500 ppb is predicted at Argo-Rowley Terrace Marine Park (8.5%) and Rowley Shoals – Mermaid Reef Marine Park (1.5%). • The maximum dissolved aromatic hydrocarbon concentration forecast for any receptor is predicted as 2.2 ppm at Argo-Rowley Terrace Marine Park.
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Flater, D 1998, D 1998, Flater, French, DP 1998, ‘Modelling the impacts of the North Cape Cape the North of impacts the ‘Modelling 1998, DP French, Davies, AMDavies, ‘Three 1977b, Fingas, M Fingas, M 2010, M 2010, Fingas, Davies, AM 1977a, ‘The numerical solutions of the three of solutions numerical ‘The 1977a, AM Davies, Authority Safety Maritime Australian altimetry’, ERS TOPEX/POSEIDON 1 and from tides ocean ‘Global 1995, OB Andersen, 6 REPORT www.rpsgroup.com/mst MAW0815J Fre FW, III, A, French Keller, S, Puckett, T, S, Isaji, Pavignano, H, Rines, S, K, Feng, Jayko, M, D, Reed, French, Fingas, M Fingas, French, DP, DP, French, Fingas, M & Fieldhouse, B 2015 B & Fieldhouse, M Fingas, Chen, F & Yapa, PD 2002, ‘A model for simulating deepwater oil and gas blowouts blowouts gas and oil deepwater simulating for model ‘A 2002, Yapa, PD & F Chen, Condie, SA & Andrewartha, &Condie, SA Andrewartha, (AMSA) Authority Safety Maritime Australian Chen, F & Yapa PD 2007, ‘Estimating the oil droplet size distributions in deepwater oil spills’, in deepwater size distributions oil droplet ‘Estimating the PDYapa 2007, Chen, & F
nch, DP & Rines, HM 1997, ‘Validation and use of spill impact modelling for impact assessment’, in assessment’, impact for spill modelling of impact use and ‘Validation 1997, HM &Rines, DPnch,
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science and technology and science Proceedings of the 8 of the Proceedings 28 Journal of Hazardous Materials Journal of Hazardous on of the vertical current profile current vertical the of on representati Proceedings of the 1997 International Oil Spill Spill Oil International 1997 of the Proceedings DC, USA. Washington, to Submitted (NRDAM/CME)’ Environments Coastal Marine and Model for BS ‘ 1996 M &Ingram, Mac G, Brown, D,McCue, J, Gifford, REFERENCES Colloquium on Ocean Hydrodynamics Ocean on Colloquium Program (AMOP) Technical Seminar Technical (AMOP) Program from an eval from Marine Oilspill Program (AMOP) Technical Seminar Technical (AMOP) Program Oilspill Marine 2938 numerical simulations with “Deepspill” field exper field “Deepspill” with simulations numerical Australia. ACT, Canberra, Authority, Maritime Safety Authority, Canberra, ACT, Australia. ACT, Canberra, Authority, Safety Maritime Continental Shelf Research Shelf Continental Geophysical Research: Oceans Research: Geophysical Hydraulic Engineering Hydraulic 353 4, pp. of termination oil for cleaning Browse to NWS Project NWS to Browse & &
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part II: comparison of of comparison II: part
in in Handbook of oil spill oil spill of Handbook Bottom Turbulence: Turbulence: Bottom Proceedings of the the of Proceedings arch - 430. st , vol. 41, no. no. 41, , vol. , Australian , Australian
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Journal of of Journal Journal of of Journal Arctic and and Arctic 1192
th -
spline Page Liege Liege
-
pp. 834. –
V
161 - ,
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REPORT
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