Northern Houtman Sub-basin Project

A key goal of Geoscience Australia's regional petroleum program is to identify new prospective energy provinces through the acquisition, analysis and delivery of pre-competitive data and associated geological assessments. The northern Houtman Sub-basin is a large frontier depocentre of the Perth Basin, offshore Western Australia, over which data coverage until now has been very poor. In order to better understand the region's hydrocarbon prospectivity, the Northern Houtman Sub-basin Project acquired a new regional 2D seismic survey, GA349, and is interpreting these data in the context of regional integration of all available datasets for the Houtman Sub-basin. The  seismic survey was carried out under the Australian government's precompetitive data acquisition program allowing for all acquired and processed data to become publically available on project completion.

The Houtman Sub-basin - An Exploration Frontier

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Figure 1. Geological setting and
location of the new seismic survey
(Borissova et al., 2017).

The Houtman Sub-basin is the largest depocentre in the offshore Perth Basin. It is almost 700 km long, up to 150 km wide and previous studies have suggested it contains a sediment succession over 12 km thick. Only three wells have been drilled in this depocentre, and while seismic coverage in the southern part of the Houtman Sub-basin is of a reasonable density, coverage in the northern sub-basin is sparse (Figure 1; Jorgensen et al., 2011; Totterdell et al., 2014). The presence of an active petroleum system in the adjacent Abrolhos Sub-basin has been demonstrated by the discovery of a commercial oil accumulation at Cliff Head in 2001 and by multiple hydrocarbon shows. However exploration to date has focused on the shallow-water part of the offshore Perth Basin and the deep-water depocentre of the Houtman Sub-basin remains largely unexplored (Rollet et al., 2013a, b).

 

New Precompetitive Data Acquisition

In 2014, Geoscience Australia acquired 3455km of new 2D seismic data across the northern Houtman Sub-basin (seismic survey GA349) to better image the basin architecture, sedimentary fill and crustal structure of this frontier province (Fig. 1; Borissova et al., 2016a, b; Owen, 2016; Southby et al., 2016). The new data have been processed to pre-stack time migration (PSTM) and pre-stack depth migration (PSDM) and are available for download via the National Offshore Petroleum Information Management System (NOPIMS) or on request from ausgeodata@ga.gov.au. In addition, a multibeam bathymetry dataset was collected as part of this survey and is also available for public download from Geoscience Australia's website (Spinoccia, 2014).

Structural Architecture and Basin Evolution

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Figure 2. Tectono-stratigraphic chart for the
northern Houtman Sub-basin
 (Borissova et al., 2017).

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Figure 3. Seismic sequences
interpreted in the northern Houtman
Sub-basin: a) example from GA
survey 349, line 1024 );
   b) thickness of NH-TR1 sequence
(Kockatea Shale equivalent).
(Borissova et al., 2017).

In 2015-16, the project conducted a regional interpretation of the legacy 2D seismic data in the Houtman Sub-basin based on ties to petroleum exploration wells in the Abrolhos Sub-basin and southern part of the Houtman Sub-basin. This regional grid was then used as a basis for seismic interpretation of the new data. Seismic sequences mapped on the new data were used to define tectono-stratigraphic framework specific to the northern Houtman Sub-basin, reflecting changes in stratigraphy in comparison to its southern part (Figure 2; Borissova et al., 2017).

Initial results of this study have already significantly improved our understanding of the tectonic evolution, structural architecture and major depositional phases of this part of the Australia's western margin. Interpretation reveals that the northern Houtman Sub-basin depocentre contains up to 19 km of sediments. This includes up to 10 km of sediment confined to a series of large half-graben, interpreted to be Permian in age, and between 4 and 6 km of Triassic, Jurassic and Early Cretaceous sequences (Figure 3; Borissova et al., 2016b, 2017). Integrated interpretation of the seismic and potential field data shows that the crust beneath the central part of the northern sub-basin is hyperextended, about 5 km thick (Sanchez et al., 2016). Outboard, more detailed analysis of the volcanic margin successions related to the development of the Wallaby-Zenith Large Igneous Province (Seaward Dipping Reflector Sequences, lava flows, volcanic complexes) is now possible (Borissova et al., 2015).

Regional Prospectivity Assessment

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Figure 4. Northern Houtman
Sub-basin petroleum systems
analysis results for selected
potential source rocks.
(Hall et al., 2017).

The newly-interpreted GA349 seismic data also provides the basis for the project's assessment of the petroleum potential of the Houtman Sub-basin. The Permian, Triassic and Jurassic successions potentially contain multiple source rock, reservoir and seal intervals (Figure 2). In addition, a variety of play types have been identified in the northern depocentre, including a very large Dongara/Kockatea stratigraphic pinchout play, where the Dongara Sandstone is sourced and sealed by the Kockatea Shale (Borissova et al., 2017).

Petroleum systems analysis results, integrating a regional assessment of offshore Perth Basin source rock geochemistry data (Grosjean et al., in prep), suggest that Permian, Triassic and Early Jurassic source rocks have generated large cumulative volumes of hydrocarbons across the northern Houtman Sub-basin, whilst Middle Jurassic-Cretaceous sources remain largely immature (Figure 4; Hall et al, 2017). However the impact of the tectonic and magmatic history of the Houtman Sub-basin on source rock maturity and the relationship between the timing of hydrocarbon generation and expulsion with respect to trap formation are critical for the successful development and preservation of hydrocarbon accumulations.

Project Outcomes

The new precompetitive data and analyses produced from this study have enabled new prospective plays to be identified in what is currently one of Australia's exploration frontiers. The systematic workflow applied here demonstrates the importance of integrated basin and petroleum systems analysis studies as a predictive tool for understanding the petroleum resource potential of Australia's frontier sedimentary basins.

Products and Publications

Data products

  • Houtman Sub-basin Seismic Survey GA349 - Seismic Field Data - Acquisition report and field tapes for the 3308 km of deep (12s) broadband 2D seismic data collected during the Geoscience Australia Survey (GA0349) in the northern Houtman Sub-basin. Available on request from ausgeodata@ga.gov.au
  • Houtman Sub-basin Seismic Survey GA349 - Processed Seismic Data - Geoscience Australia Houtman Sub-basin 2D Seismic data (GA0349) processed to PSTM (pre-stack time migrated) and PSDM (pre-stack depth migrated). These data provide the first regional grid over the northern part of the Houtman Sub-basin. Available from NOPIMS or on request from ausgeodata@ga.gov.au
  • Spinoccia, M, (2014). Houtman Sub-basin 2D Seismic Survey 2014, (GA-0349/Duke10046) - High Resolution Bathymetry Grids. Geoscience Australia, Canberra. -  Multibeam bathymetry dataset collected along ship tracks during the Geoscience Australia Houtman Sub-basin 2D Seismic Survey (GA0349)

Reports and news articles

  • Bodorkos, S., Fitzsimons, I. C. W., Hall, L. S., Sircombe, K. N. and Lewis, C. J. (2016). Beneath the Perth Basin: New U-Pb SHRIMP zircon ages from the Pinjarra Orogen, Western Australia. Geoscience Australia, Canberra. -  New age constraints on Pinjarra Orogen basement beneath the Perth Basin.
  • Southby, C.,Borissova, I.,Owens, R.,Bernardel G.and Morris, R. (2016). Northern Houtman Sub-basin in the spotlight PESA News magazine -  An article published in the Petroleum Exploration Society of Australia's monthly magazine, PESA News. The article outlines objectives of the Houtman Sub-basin Prospectivity Study and initial findings of the project.
  • Grosjean, E., Hall., L.S. and Boreham, C. (in prep). Source Rock Geochemistry of the offshore northern Perth Basin. Record in prep. Geoscience Australia, Canberra. -  A review of the offshore northern Perth Basin source rock geochemistry and maturity based on a compilation of publically available data.
  • Owen, A. (2016). GA349 Houtman 2D Seismic Data-Overview. Geoscience Australia, Canberra. -  An overview of the 2D seismic survey GA349 recently acquired by Geoscience Australia in the northern Houtman Sub-basin, with a list of available data products
  • Sanchez, G., Hall, L.S., Shi, Z., Borissova, I., Pryer, L., Southby, C., Romine, K., Westerman, G., Pietrucha, C. and Kroll, A. (2016). Houtman Sub-basin Geophysical Modelling. Frogtech Pty Ltd, Canberra, Australia. -  An integrated geological and geophysical interpretation of the GA349 seismic survey by Frogtech Geoscience and Geoscience Australia.

Conference proceedings

Other key references