Hydrocarbon Potential of the Offshore Northern Perth Basin | 1 ISSUE 103 Sept 2011

Gamma Ray GOI Depth 0 (API Units) 200 0 5 (%) 20 (mRT) Percent ISSUE 103 Sept 2011 Lithostrat. Oil Shows Sequence 100 0 Morangie 1 Hydrocarbon2080 potential of the offshore 2090 northern Perth Kockatea Basin 2100 Kockatea Shale Hovea Member New data and knowledge2110 deliver 16.1% opportunities for petroleum explorers10.6% 2120 Andrew Jones, Diane Jorgensen, Ron Hackney4.5% and 2130 Chris Nicholson 18.7% 2140 4.3% Geoscience Australia has recently completed an assessment10.5% of the knowledge generated during this Dongara hydrocarbon prospectivity of the2150 offshore northern Perth Basin to study has enhanced the potential 5.1% stimulate exploration in the basin byWagina Formation Australia’s offshore 10.5%oil and gas for new oil and gas discoveries industry. The study was mainly2160 based on new data collected asP-ODT part of in the Perth Basin. It also Palaeo-oil No shows SWC Geoscience Australia’s Offshore Energy Security Program. A down-toreview of underpinned the release of area 2170 Cuttings not depth the Program is included in this issue of AusGeo Newsmatched. to wireline W11-18 in April 2011 as part 11-5494-5 The new datasets, including regionalOil Shows two-dimensional (2D) of the Australian Government’s and three-dimensional (3D) seismic, potentialCuttings field and SWCwell data, 2011 release of offshore provided an improved understanding of basin evolution and the petroleum exploration acreage spatial distribution of key petroleum system elements. The new (see AusGeo News 102). Biostratigraphy Geochemistry Gamma Sequence Depth Cuttings Picks VR Ray Sequences Spore-Pollen Dinocyst TOC S1 S2 HI PI TMAX (mRT) Lithology SWC Depth (mg hydrocarbon (mg S2 (°C) (%) Shows (%) (gAPI) (mRT) Zones Zones /g rock) /g TOC) Water Bottom 68.7 100 Valanginian Unconformity 128.39 200 300 Yarragadee SB 356 400 Cadda SB 412 Upper D. caddaense C. turbatus 500 600 Cattamarra MFS 625 C. turbatus 700 800 Lower Luehndea Cattamarra SB 845 C. turbatus Assemblage 900 ?cavings? ?cavings? 1000 Eneabba SB 1036 S. speciosus 1100 or older Lesueur SB 1162 Lower 1200 Woodada SB 1221 T. playfordii 1300 P. samoilovichii 1400 Hovea FS 1424.52 L. pellucidus Kockatea SB 1466 P. microcorpus 1500 P. sinuosus Dongara SB 1485 or younger 1600 M. trisina Irwin River SB 1728 or younger 11-5494-1 Figure 1. An example of the data included in the Dunsborough-1 well composite from the offshore northern Perth Basin well folio (location shown in figure 4). The Middle Jurassic to Permian stratigraphy in Dunsborough-1 was revised on the basis of sequence stratigraphic analysis that incorporated a review of open-file palynological data and new palynological analysis of cuttings samples over the interval 380-1210 mRT. Forty-one new geochemistry and 10 new Vitrinite Reflectance measurements were acquired from cuttings and side wall core samples over the interval 580-1725.4 mRT. Hydrocarbon potential of the offshore northern Perth Basin www.ga.gov.au/ausgeonews/ | 1 ISSUE 103 Sept 2011 Oil is currently being produced from the offshore northern Perth since the Cliff Head–1 discovery. Basin, specifically from the Cliff Head oil field that was discovered The new biostratigraphic in 2001. Three more petroleum discoveries were made in this part data were reviewed and used of the basin in 2007, with oil and gas in Dunsborough–1, and gas in in conjunction with well logs Frankland–1 and Perseverance–1. These accumulations are located in and lithological interpretations Permian sandstones and have primarily been sourced from the Triassic of cuttings, cores and Hovea Member of the Kockatea Shale. This shale has also been the sidewall cores to define a new source of the majority of producing oil and gas fields of the onshore chronostratigraphic sequence Perth Basin. framework. Depositional sequences and key maximum Depositional history flooding surfaces are correlated The biostratigraphic history of the offshore northern Perth Basin was between wells to show the spatial revised through combining existing well data with interpretations of and temporal distribution of newly-acquired palynology data. This study also included the first these sequences. The main published synthesis of data from 14 new exploration wells drilled sedimentary succession in this part of the basin is Permian to 112° 116° SOUTHERN Late Jurassic in age. Two regional W CARNARVON WESTERN it unconformities were identified te BASIN AUSTRALIA ca Houtman rra 28° and they correspond to regional Sub-basin T e rra uplift in the Late Permian c e W11-18 Bo Sh (Capitanian) and the breakup of o ka e l ra f Australia and Greater India in the Zeewyck Abrolhos Valanginian Stage. Sub-basin Sub-basin T B The new data and u e C D rt a l a a R e g d l n i D e d d d interpretations for 23 of the g o e ve R a a ra i T d e g g petroleum exploration wells are r e a r a n ce 0 150km T Be ro included in the offshore northern e u rmu g h Perth Basin well folio (figure 1). lla h Tro These new data include: 120 u Y g a h l Dataset l new palynological samples; 244 i location n NT g u WA QLD p new geochemistry measurements; Sh Figure SA Vlaming 32° e 100 new thermal maturity l Sub-basin extent NSW f VIC measurements; and a compilation Full dataset TAS coverage of Grains with Oil Inclusions 11-5494-3 (GOITM) data. All data presented 2 350 µm/s 2011 Offshore Petroleum Sub-basin outline in the folio were either publicly 100 µm/s2 Acreage Release Area 2 50 µm/s Macallan 3D seismic available or newly derived. The 0 µm/s2 survey location composite 1:5000 scale well log -50 µm/s2 -100 µm/s2 summarises, in graphic form, -850 µm/s2 the main stratigraphic features Figure 2. The levelled and merged gravity dataset for the northern Perth and hydrocarbon occurrences Basin and adjacent onshore areas overlain by structural elements of the (figure 1). The folio also includes offshore northern Perth Basin and the Release Area W11-18. The residual gravity image is computed from the Bouguer anomaly by subtracting its Offshore Perth Basin Biozonation upward continuation to 25 kilometres. and Stratigraphy 2011 Chart 38. Hydrocarbon potential of the offshore northern Perth Basin www.ga.gov.au/ausgeonews/ | 2 ISSUE 103 Sept 2011 Australian National Gravity 112° 116° W SOUTHERN it Database. The final compilations te ca CARNARVON rra BASIN of gravity and magnetic data T e rra 28° provide a consistent dataset that c Houtman e Sub-basin covers the southwestern margin W11-18 Bo Sh o ka of Australia (106–120°E and e l ra f 19–37°S). This area includes the Zeewyck Abrolhos Sub-basin Sub-basin Mentelle, Perth and southern D T B a u e n WESTERN C r a t d Carnarvon basins, as well as l a R e g a AUSTRALIA d l ra i D e d d g o g e ve R a the Wallaby Plateau. Data a i T d n e g r T e r ro a covering the northern Perth ce 0 150 km u g Be h Basin (figures 2 and 3), as well e rmu lla as the full dataset coverage of the h Tro u area, are available for download Y g h a l l i n through the Geophysical NT g QLD u WA p Vlaming Archive Data Delivery System Sh Figure SA Sub-basin 32° extent NSW e l f (see below). VIC The new compilations of Full dataset TAS coverage 11-5494-4 levelled gravity and magnetic data covering marine and onshore 450 nT 2011 Offshore Petroleum Sub-basin outline Acreage Release Area areas are facilitating structural 100 nT and geological interpretations 0 nT -50 nT of the offshore northern Perth -100 nT Basin. Depth-to-basement and -850 nT basement architecture in some Figure 3. The levelled and merged, reduced-to-pole magnetic dataset for the northern Perth Basin and adjacent onshore areas overlain by structural parts of the basin are not well elements of the offshore northern Perth Basin and the Release Area W11-18. defined using seismic data. For these locations integrated New geophysical datasets modelling and interpretation A major output from the study is a data package which includes of potential field data are being reprocessed seismic data, new seismic reflection data and new gravity used to provide additional and magnetic data. The new seismic, gravity and magnetic datasets information. Several geophysical were collected between October 2008 and February 2009 during two processing methods are being major surveys off the coast of Western Australia (surveys GA-310 applied to the new datasets, and GA-2476). The datasets collected during these surveys have including wavelet-based multi- greatly improved the coverage over a large portion of Australia’s scale edge detection to highlight southwestern margin. The data package covering this area was released the edges of anomalies. This to the petroleum industry by the Australian Government’s Minister method complements seismic for Resources and Energy, the Hon Martin Ferguson AM MP, in reflection data for mapping April 2010. structural trends. Spectrally-based The new gravity and magnetic data were merged and levelled with depth-to-basement estimates and an existing Australia-wide dataset (Petkovic et al 2001) and combined three-dimensional (3D) gravity with onshore data from the fifth edition of the Magnetic Anomaly modelling are being used to map Map of Australia (Milligan et al 2010) and the 2010 version of the basement architecture. Hydrocarbon potential of the offshore northern Perth Basin www.ga.gov.au/ausgeonews/ | 3 ISSUE 103 Sept 2011 a) 113° 114° 115° Petroleum prospectivity assessment Geraldton The new seismic data collected by Dunsborough 1 29° Geoscience Australia show that 4b Permo-Triassic strata which are re u WESTERN Fig AUSTRALIA stratigraphically equivalent to the productive onshore and nearshore 0 50 km W11-18 Cliff Head Perth Basin petroleum system also occur within Permian half- grabens in the outer Abrolhos 30° and Houtman sub-basins.

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