Exploring the Sub-Salt Play in the Frontier Amadeus Basin – Insights from Potential Field Data Analysis

Exploring the sub-salt play in the frontier Amadeus Basin – Insights from potential field data analysis

T Debacker, K Connors, J Lee, S Watters, J Clifford, P Plummer and S Menpes EXPLORING THE SUB-SALT PLAY IN THE FRONTIER AMADEUS BASIN – INSIGHTS FROM POTENTIAL FIELD DATA ANALYSIS Timothy Debacker1, Karen Connors1, Jia-Urnn Lee1, Sandy Watters2, Jenni Clifford2, Phil Plummer2 and Sandra Menpes2

1 FROGTECH Thanks to C. Pietruchia, C. Jorand, Z. Shi, A. Kroll, M. den Hartog (FROGTECH), E. 2 Santos Ltd Hissey and W. Aspinal (Santos) and exploration team of Central Petroleum Email: [email protected]

AGES, 2016 Alice Springs Introduction: Exploring the Sub-salt Play in the Southern Amadeus Basin

Sub-salt Play • Primary exploration target • Neoproterozoic lower Gillen- Heavitree petroleum system • Gas flows from Magee-1 (1992) and Mt Kitty-1 (2014) have proven the sub-salt play

2013 AMSAN 2D Seismic Survey • First regional framework 2D seismic • 1586 line km over an area totalling 43,000 sq km • Line length up to 387km

Objectives • Provide regional structural and stratigraphic framework • Link isolated 2D grids • Identify key leads for follow up

Introduction: New Sub-salt Leads Identified

• Two significant sub-salt leads identified (Dukas shown here) • Regional framework seismic grid - higher spatial density magnetic and gravity surveys useful for interpolating trends away from seismic and well control. • Santos contracted FROGTECH to update the SEEBASE™ Depth-to-Basement Model of the Amadeus Basin Introduction: SEEBASE™ update

FROGTECH update for Santos of 2004 and 2005 SEEBASE™ of Amadeus Basin, 2014-20152004 SEEBASE™SEEBASE™ calibrated with newly acquired seismic data

2005 SEEBASE™

SW NE Basin Stratigraphy

• Central and eastern parts dominated by NW-SE trends, 4 Petermann Orogeny

with exceptions Cambrian Unconformity • More random trends in western parts, above Gillespie Petermann Unconformity Craton. 3

• Central zone with Neoproterozoic units at surface with a broadly anticlinal geometry, but extensively brecciated in many areas. 2

Centralian Extension II

Structure 1 Salt-bearing unit: Gillen Member of

F Anticline the Bitter Springs Formation Basement thrust fault Centralian Extension I

Fault

Crystalline Basement

M Syncline

Potential field data

Gravity data: BG HP300 km • ~E-W-trending long-wavelength positive and negative gravity anomalies • ~NW-SE-trending, elongate short- wavelength positive gravity anomalies (central and east) • Variable moderate to short-wavelength gravity trends in west

Magnetic data:

• Shallow magnetic (and “non-magnetic”) basement surrounding Amadeus Basin RTP CMY ternary • ~NE-SW-trending moderate to long- wavelength anomalies below central and eastern Amadeus Basin • ~NW-SE-trending, elongate short- wavelength magnetic anomalies (central and east) • Variable moderate to short-wavelength magnetic trends in west

Potential field data and basement terranes

• Cratonic basement below western BG HP200 km

Amadeus Basin • Link with Albany-Fraser Orogen for

basement below central and eastern Gillespie

Amadeus Basin (cf. Betts et al., 2011)

RTP CMY ternary

Gillespie Musgrave Province / Petermann Orogeny

Deformation style and link with gravity data

• Predominantly detached Petermann Orogeny deformation style, facilitated by Bitter Springs Formation salts • Local basement-involved Petermann Orogeny deformation style • Deformation asymmetry decreases N- ward, away from Musgraves • Seismic wash-out zones flanked by upturned sediments, interpreted as (brecciated) salt mobilisation zones BG HP300 km

S Detached Petermann Orogeny faults Delamerian Unconformity N Petermann Unconformity

Reverse basement fault, possibly 3s inverted Centralian normal fault Seismic wash-out zones correspond to local positive gravity anomalies and are interpreted Metasedimentary basement (?) affected to be zones of intensely brecciated carbonate by Petermann Orogeny reverse faults and anhydrite as a result of salt mobilisation amsan 13B-04 Crystalline basement Deformation style and link with gravity data

• Elongate ~NW-SE-trending short-wavelength positive • Edges of seismic wash-out zones correspond to gravity anomalies are linked to upturned carbonates of elongate short-wavelength positive gravity anomalies Bitter Springs Formation • In general seismic wash-out zones correspond to positive gravity anomalies

High-Pass 20 km

High-Pass 50 km

Wash- out zone Wash- out zone

3s Deformation style and link with gravity data

• High-density intrabasinal sources contributing to central positive gravity anomaly: • (1) coherent sedimentary packages containing dolomite and limestone • (2) highly disrupted zones that show up as wash-out zones on seismic.

2 1 2 2

1 2 2 1 1 1

BG HP200 km Deformation style and link with gravity data

• Basement in Mereenie area shallower than BG HP300 km expected from position relative to regional negative gravity anomaly

N S

Hermannsberg section (Warren & Shaw, 1995) ~ - 11km

Mereenie p81-ge08r1 SW Basement-involved Alice NE Springs Orogeny deformation

Petermann Neoproterozoic Unconformity deformed during 3s Petermann Orogeny Basement Interpreted Centralian fault Deformation style and link with gravity data

• Basement-involved Alice F Springs Orogeny (II and III) Anticline M Syncline deformation style Ordovician extension lineament • Strong basement control on Centralian extension lineament compressional deformation Albany-Fraser I lineament geometry in central and Surface geology northern part of Amadeus Basin Alice Springs Event Post-Petermann Ord-Sil Cambrian post-Petermann Petermann Event Boord-Inindia

Mereenie p81-ge08r1 SW Basement-involved Alice NE Springs Orogeny deformation

Petermann Neoproterozoic Unconformity deformed during 3s Petermann Orogeny Basement Interpreted Centralian fault Gravity Modelling

• Three regional gravity models BG HP300 km • East line to investigate contribution of high-density Neoproterozoic sediments to central positive gravity anomaly • Gravity models constrained by seismic data, wells, cross-sections, surface geology and density values from wells .

Delamerian Unconformity (yellow)

Petermann T3 Unconformity X (blue) X T2 X X X X X T1 Basement

Line amsan13b-04 Legend

Gravity Modelling Devonian-Carboniferous Basement (Musgrave or Warumpi equivalent) sequence Neoproterozoic Basement (Musgraves S, Warumpi N) sequence • Eastern gravity model shows Silurian sequence Basement (Arunta West Terrane) Fault zone significant contribution of high-density Cambrian sequence Lower crust Intensively deformed Neoproterozoic sediments to central carbonates and evaporites positive gravity anomaly related to salt mobilisation Gravity Modelling

• Central gravity model focusses BG HP100 km on source of long-wavelength gravity anomalies

Legend Syn-Petermann sequence (”Winnall Beds”) Boord Formation / Inindia Beds Bitter Springs Formation Deformed carbonates and evaporites (basal Bitter Springs Fm.) and Dean/Heavitree Quartzite Basement (Musgrave equivalent) Basement (Arunta and Warumpi terranes) Lower crust High-density basin units beneath thrust nappe Musgrave Central 2.69 2.96 Province Australian 2.64 2.55 Petermann 2.75 Suture Nappe Complex 2.75 2.70 2.74 2.69 2.67 2.67 Warumpi Arunta West 2.63 2.79 2.74 2.84 metasediments 2.64 2.82 2.76 2.70 2.74 2.75 2.84 2.69 – Upper Crust 2.74

2.75 – Lower Crust 2.70 2.90 2.85 2.99 Mann Fault 2.97 2.90 2.91 Tikelmungulda Seismic Province 3.32 - Mantle Potential field data interpretation

Gravity data: BG HP300 km • Short-wavelength anomalies caused by intrabasinal sources (upturned carbonates, salt mobilization residuals) • ~E-W-trending long-wavelength positive and negative gravity anomalies are result of shallow high-density basin units, changes in basement depth, changes in Moho depth, and crustal density variations

Magnetic data:

• ~NE-SW-trending moderate to long- wavelength anomalies reflecting RTP CMY ternary compositional variations related to Albany Fraser Orogen (cf. Betts et al., 2011) • Illustrate changes in depth of magnetic basement • Top of magnetic basement usually deeper than top economic basement Potential field data interpretation

Magnetic data: RTP CMY ternary • Top of magnetic basement usually deeper than top economic basement Conclusions

New SEEBASE of Amadeus basin based on Santos seismic new NTGS potential field data and open file data from GSWA

Petermann Nappe Complex

Musgraves 2016 Exploration Program

2016 2D Seismic Survey • 1300 km 2D seismic infill program • Designed to mature leads identified from the 2013 seismic survey and the 2014– 2015 SEEBASE™ depth-to-basement map to drillable prospect status • Two rounds of acquisition – Round 1 lines are firm • In-field processing and preliminary interpretation to determine which Round 2 lines will be acquired Background image 2014–2015 SEEBASE™ depth-to-basement model

Legend Dukas

2013 Seismic Acquisition

2016 Seismic Round 1

2016 Seismic Round 2

Background image Digital Elevation Model