Browse Basin Petroleum Systems Study

Overview

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Figure 1 a.) Location of the Browse
Basin; b.) Seismic sequences
and petroleum systems elements
of the Caswell and Barcoo sub-basins;
c.) 3D perspective view of the basin,
including location of calibration wells
used for petroleum systems analysis.
From Palu et al. (2017).

The Browse Basin located offshore on Australia’s North West Shelf hosts considerable gas and condensate resources (e.g. le Poidevin et al., 2015; Kuske et al., 2015). It is poised to become Australia's next major conventional liquefied natural gas (LNG) province with the Ichthys, Prelude and Concerto fields currently under development and recent discoveries made at Burnside, Lasseter and Crown/Proteus in the Caswell Sub-basin (Figure 1a). However oil discoveries are presently sub-economic and confined to the central Caswell Sub-basin (Caswell) and Yampi Shelf (Cornea, Gwydion).

Geoscience Australia is undertaking a reassessment of the petroleum prospectivity of the Browse Basin to identify the various hydrocarbon sources and high-grade areas of increased liquids prospectivity within this primarily gas-prone province. This multi-disciplinary study integrates sequence stratigraphy, geochemical and regional petroleum systems analyses to better understand:

  • 3D distribution of reservoir and seal pairs, and areas with enhanced source rock development,
  • source rock geochemical characteristics,
  • petroleum fluid composition, phase behaviour and geochemical typing,
  • burial and thermal history, source rock maturity and generation history,
  • the extent and distribution of existing and newly identified hydrocarbon plays.

Sequence Stratigraphy

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Figure 2 Cretaceous K10‐K40
supersequence depositional
models showing their internal
geometry and stacking pattern
in the Browse Basin.
h) Distribution of the good-quality
reservoir and seal pairs
for the K10‐K65 supersequences.
From Rollet et al. (2016).

The sequence stratigraphic interpretation is based upon a common North West Shelf stratigraphic framework that has been developed in conjunction with industry, and aligned with the international time scale (Figure 1b; Gradstein et al., 2012; Marshall & Lang, 2013; Kelman et al., 2016). Sixty key wells and 2D and 3D seismic data have been interpreted to produce palaeogeographic maps and depositional models for the Jurassic and Cretaceous successions (Figures 1c and 2; Abbott et al., 2016; Rollet et al., 2016a, b). This work was completed as part of a regional assessment of CO2 storage potential in the Browse Basin (Rollet et al., 2016a).

Isochore maps and depositional environmental models are used to map the distribution of key source, reservoir and seal units. Three main reservoir-seal pairs, associated with stratigraphic traps, have been identified within the Cretaceous succession (Rollet et al., 2016b). In addition, multiple source rock units have been identified in compartmentalised Jurassic‐Cretaceous source pods, resulting in four distinct petroleum systems. The location of these petroleum systems elements are influenced by regional basin architecture and entrenched fluvial systems, which form a complex network of sedimentary inputs to the basin (Rollet et al., 2017).

Source Rock Characterisation

Browse Basin source rocks are typically difficult to characterise because they are either sparsely drilled and/or sampled, or have only been penetrated on structural highs and basin margins where their quality may not be representative. Indicative source rock geochemical characteristics have been assessed based on an updated compilation of quality-controlled total organic carbon (TOC), Rock-Eval pyrolysis and vitrinite reflectance data. This data was used in conjunction with sequence isochores and lithological constraints from wells to map source rock thickness, richness and quality across the basin (Palu et al., 2017).

Petroleum Fluids

Using the fluid composition of the hydrocarbon occcurences, the fluid phase characteristics are assessed to understand the possible lateral and vertical fluid distribution in the basin. Bulk reservoir fluid compositions indicate that most fluids belong to dew-point petroleum systems where gas-liquid-ratios (GLR) are high (>10,000 scfs/bbl), consistent with their sourcing from gas-prone source rocks (Figure 3; Edwards et al., 2016; Palu et al., 2017). However, these fluids are expected to drop out oil rims when migrating into shallower traps and this may result in light oil spilling up-dip or being present as a residual column after gas loss through leaking seals.

Geochemical analyses characterise the molecular and stable isotopic signatures of fluids occurrences and enable them to be correlated with potential source rocks. Four Mesozoic petroleum systems were identified by their geochemical fingerprints and can be correlated with several petroleum systems sourced from: 1) the J10‐J20 supersequences (Plover Formation), J10-J50 supersequences (Jurassic succession within the Heywood Graben), J30‐K10 supersequences (Vulcan Formation) and K20‐K30 supersequences (Echuca Shoals Formation) (Figures 4 and 5; Grosjean et al., 2015; Edwards et al., 2014, 2016; Spaak et al., 2016). In addition, isotopic signatures are used to investigate the role of biodegradation on fluid composition along the basin margin (Grosjean et al., 2016).

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Figure 3 a) Gas-liquid-ratio (GLR) vs saturation pressure plot for available fluid data. Solid lines show global trends of dew point and bubble point thresholds. b) Saturation pressure vs measured reservoir pressure for the same data. From Palu et al. (2017)

Petroleum Systems Analysis

Petroleum systems analysis is applied as a predictive tool to further understand the source of Browse Basin fluids and their phase behaviour. A regional 3D geological model, developed from the new seismic interpretation (Rollet et al., 2016a) forms the basis of a pseudo-3D petroleum systems model (Figure 1c; Palu et al., 2017). Petroleum systems modelling, integrating source rock property maps, basin-specific kinetics, 1D thermal history models and regional 3D surfaces, provides new insights into source rock maturity, generation and expelled fluid composition (Figure 3 and 6). Results shows that source rocks within the Caswell Sub-basin have reached sufficient maturities to have transformed most of the kerogen into hydrocarbons, with the majority of expulsion occurring from the Late Cretaceous until present. Within the Barcoo Sub-basin, source rocks within the J10‐J20 supersequences have reached sufficient maturity for generation, where the better-quality source rocks within this supersequence have expelled hydrocarbons (Palu et al., 2017). Only limited generation and expulsion is reached from the other two source rock successions.

Outcomes - New Insights into Regional Petroleum Prospectivity

Integration of the newly defined Browse Basin sequence stratigraphic framework, with a comprehensive petroleum system analysis, improves the understanding of the type, extent and charge history of a wide range of play types across the Browse Basin. For example, multiple stacked Cretaceous plays have now been identified along underexplored areas of the basin margin, which may be charged locally by a mixture of Jurassic‐Cretaceous source rocks (Abbott et al., 2016; Rollet et al., 2016; 2017).

The new precompetitive data produced from this study de-risks key outstanding exploration issues associated with the Browse Basin and aids the identification of new prospective areas in what has previously been perceived to be a relatively well explored sedimentary basin. Furthermore, the systematic workflow applied in this study demonstrates the importance of integrated sequence stratigraphic, geochemical and petroleum systems analysis studies as a predictive tool for understanding the petroleum resource potential of Australia’s sedimentary basins.

References

  • AGSO Browse Basin Project Team, 1997. Browse Basin High Resolution Study, Interpretation Report. Record 1997/38. Australian Geological Survey Organisation, Canberra.
  • Gradstein, F.M., Ogg, J.G. & Schmitz, M.D., 2012. The Geologic Time Scale 2012. Elsevier BV, Boston, USA. 1144 pp.
  • Marshall, N.G. & Lang, S.C., 2013. A new sequence stratigraphic framework for the North West Shelf, Australia. In: Keep, M. & Moss, S.J. (eds.) The Sedimentary Basins of Western Australia 4: Proceedings of Petroleum Exploration Society of Australia Symposium. Petroleum Exploration Society of Australia, Perth. 1-32.

Reports, datasets and presentations

Rollet, N., Grosjean, E., Edwards, D., Palu, T., Hall, L., Abbott, S., Lech, M., Totterdell, J., Nguyen, D., Khider, K., Boreham, C., Higgins, K., Gunning, M-E., Nicholson, C. (2017). Depositional framework of petroleum systems, Browse Basin, offshore North West Shelf, Australia. AAPG|ICE International Conference - London , 15-18 October 2017 (Abstract and Oral presentation).
Palu, T., Hall, L., Grosjean, E., Rollet, N., Boreham, C., Buckler, T., Higgins, K., Nguyen, D., Khider, K. (2017). Source Rocks and Hydrocarbon Fluids of the Browse Basin. AAPG|ICE International Conference - London , 15-18 October 2017 (Abstract and Poster presentation).
Palu, T., Hall, L., Grosjean, E., Edwards, D., Rollet, N., Higgins, K., Boreham, C., Murray, A., Nguyen, D., Khider, K. & Buckler, T. (2017). Integrated petroleum systems analysis to understand the source of fluids in the Browse Basin, Australia. Extended abstract and poster presentation, APPEA Journal 2017, 57.
Rollet, N., Edwards, D., Grosjean, E., Palu, T., Abbott, S., Lech, M., Totterdell, J., Nguyen, D., Khider, K., Boreham, C., Hall, L., Higgins, K., Gunning, M. & Nicholson., C. (2017). Reassessment of the petroleum prospectivity of the Browse Basin, offshore Northwest Australia. SEAPEX Exploration Conference 2017, 26th - 28th April 2017. (Abstract and oral presentation)
Edwards, D.S., Grosjean, E., Palu, T., Rollet, N., Hall, L., Boreham, C.J., Zumberge, A., Zumberge, J., Murray, A.P., Palatty, P., Jinadasa, N., Khider, K. & Buckler, T. (2016). Geochemistry of dew point petroleum systems, Browse Basin, Australia. In: 19th Australian Organic Geochemistry Conference, 4-7 December 2016, Abstract and oral presentation.
Grosjean, E.,Edwards,D.S.,Boreham,C.J.,Hong,Z.,Chen,J. & Sohn,J. (2016). Using neo-pentane to probe the source of gases in accumulations of the Browse and Perth Basins. In: 19th Australian Organic Geochemistry Conference. Fremantle, 4-7 December 2016.
Rollet, N., Grosjean, E., Edwards, D., Palu, T., Abbott, S., Totterdell, J., Lech, M., Khider, K., Hall, L., Orlov, C., Nguyen, D., Nicholson, C., Higgins, K. & McLennan, S. (2016b). New insights into the petroleum prospectivity of the Browse Basin: results of a multi-disciplinary study. APPEA Journal, 483-494. (Abstract and oral presentation)
Rollet, N., Abbott, S.T., Lech, M.E., Romeyn, R., Grosjean, E., Edwards, D.S., Totterdell, J.M., Nicholson, C.J., Khider, K., Nguyen, D., Bernardel, G., Tenthorey, E., Orlov, C. and Wang, L. (2016a). A regional assessment of CO2 storage potential in the Browse Basin: Results of a study undertaken as part of the National CO2 Infrastructure Plan. GA Record 2016/17, Canberra, Australia.
Abbott, S., Khider, K., Kelman, A., Romine, K. (2016). Facies architecture of the K10 supersequence in the Browse Basin: when sequence stratigraphy meets lithostratigraphy. In: APPEA 2016 Journal and Conference Proceedings.
Kelman, A.P., Khider, K., Rollet, N., Abbott, S., Grosjean, E. & Lech, M. (2016). Browse Basin Biozonation and Stratigraphy, Chart 32. Geoscience Australia.
Spaak, G., Edwards, D.S., Grosjean, E., Scarlett, A.G., Grice, K. (2016). Combining GCXGC and CSIA of diamondoids and aromatics to unravel the sources of (biodegraded) hydrocarbons in the browse Basin. In: 19th Australian Organic Geochemistry Conference, 4-7 December 2016, Abstract and poster presentation.
Grosjean, E., Edwards, D.S., Kuske, T.J., Hall, L., Rollet, N. & Zumberge, J.E. (2015). The source of oil and gas accumulations in the Browse Basin, North West Shelf of Australia: a geochemical assessment. AAPG ICE, 13-16 September 2015, Melbourne, Australia.
Kuske, T. J., Le Poidevin, S. R. & Edwards, D. S. (2015). Browse Basin Petroleum Accumulations. Extended abstract and poster presentation, APPEA Journal 2015, 55.
Edwards, D., Grosjean, E. & Rollet, N. (2015). Geochemical Characteristics of Oil and Gas Accumulations Used to Define the Petroleum Systems of the Browse Basin. RIU Good Oil Conference, 2-3 September 2015, Fremantle, Australia.
Le Poidevin, S. R., Kuske, T. J., Edwards, D. S. and Temple, P. R. (2015). Australian Petroleum Accumulations Report 7 Browse Basin: Western Australia and Territory of Ashmore and Cartier Islands adjacent area, 2nd edition. Record 2015/10. Geoscience Australia, Canberra.
Edwards, D.S., Grosjean, E., Kuske, T., Le Poidevin, S., Chen, J., Hong, Z., Boreham, C.J., Rollet, N. & Zumberge, J. (2014). Redefining the petroleum systems of the Browse Basin. Program and Abstracts. AOGC2014: the 18th Australian Organic Geochemistry Conference, 30 November-2 December 2014, Adelaide, South Australia.