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Journal of Australian Energy Producers
RESEARCH ARTICLE

Re-discovering the Gummy gas field – Gippsland Basin

Eamonn Montague A * , Brendan Frears A , Mark Browne A , Peter Strauss A , Stephen Adams B and Jeremy Prosser C
+ Author Affiliations
- Author Affiliations

A Cooper Energy Ltd., Adelaide, SA, Australia.

B The Petrophysicist Ltd., Karaka, New Zealand.

C TASK Fronterra Geoscience, Perth, WA, Australia.

The APPEA Journal 63 190-206 https://doi.org/10.1071/AJ22246
Submitted: 21 December 2022  Accepted: 23 February 2023   Published: 11 May 2023

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of APPEA.

Abstract

Recent sub-surface studies of the Gummy Gas Field have resulted in a significant upgrade of its gas and liquids resource potential. Previous interpretations had ascribed little resource potential to the field. Shell drilled Gummy-1 in 1990, a Golden Beach (GB) Subgroup gas/liquids discovery in the eastern Gippsland Basin. The GB Subgroup was previously described as a stacked, grading to generally thin, isolated sandstone reservoir hosting limited gas volumes. In 2022, a new study integrated the interpretation of the CGG Gippsland Multi-Client 3D seismic survey dataset with a re-look at the reservoir characterisation, petrophysical properties and reservoir pressures and found that reservoir quality is better than previously thought. The improved reservoir quality is interpreted to be the result of depositional reworking, which also increases confidence that the sandstones are laterally extensive. Consideration of the impact of regional pressure depletion due to nearby production from the GBJV fields has improved the understanding of the hydrocarbon columns encountered at Gummy-1. Increased hydrocarbon column heights are interpreted, which are consistent with wireline log evaluation and regional saturation-height data. Confidence that the seal at Gummy is working as effectively or better than offset fields and reservoirs is high. The new interpretation has also significantly improved the exploration potential for underlying gas reservoirs within the middle and lower GB Subgroup. Gummy-1 reached a total depth of 3530 m MDRT in a gas sandstone reservoir with an interpreted main gas column up to 185 m. Potential exists for additional gas in reservoir quality sandstones to be discovered in deeper exploration targets – the Gummy Deep exploration prospect. Combined with the adjacent Manta Gas Field, this demonstrates the enhanced potential for future commercial development in the area.

Keywords: aquifer depletion, BMG, depositional environment, dipmeter data, gas development, gas exploration, geophysics, Gippsland Basin, Golden Beach Formation, Gummy, petrophysics, reservoir quality.

Eamonn Montague graduated with an Honour’s degree in Petroleum Geology from Adelaide University in 1989 and has 33 years of experience. Confronted with limited geoscience opportunities, he began a Reservoir Engineering career with a 5-year stint at Santos. He then travelled to the UK in 1995 and worked with Reservoir Management Ltd. for several North Sea operators. In 1997, he returned to Australia and worked with Mobil in Perth. After the Exxon-Mobil merger, he spent 4 years working as a lecturer, researcher and consultant at Curtin University. It was back to consulting in 2004 and then overseas with Shell Brunei from 2005 to 2008. He returned to Adelaide in 2008 as a Consultant and then another 4 years on staff at Santos. In 2014, he moved back into the consulting realm, where he worked with Cooper Energy and Oilfield Data Services, Inc., eventually joining Cooper on staff in 2020.

Brendan Frears is a Senior Geologist at Cooper Energy. He has over 16 years of experience working primarily on exploration assets, focussing on sedimentology, modern-day analogues, well planning, play-based studies and petroleum systems modelling. Brendan has a BSc (Exploration Geoscience) from the University of Adelaide and a BSc (Honours) from the Australian School of Petroleum. His career began at Santos, in Adelaide, from 2007 as a Graduate Geologist. Through 14 years, he took on various roles, including onshore and offshore exploration campaigns, with high levels of success. He is currently based in Adelaide, within Cooper Energy’s Exploration team, focussing on operated Southeast Australian offshore acreage in the Gippsland and Otway basins.

Mark Browne is a Geophysicist with over 30 years of experience in seismic processing and interpretation. Mark has a BSc (Hons) from the National Centre for Petroleum Geology & Geophysics (Adelaide University). His career started in seismic processing and moved into seismic interpretation, where he currently resides. He has worked on most basins throughout Australia and Southeast Asia with companies such as Santos, Woodside, Mobil and Shell. He is presently a Staff Geophysicist with Cooper Energy, where his main interest is to get more geology from seismic data.

Peter Strauss is a Geophysicist with over 40 years of experience in seismic acquisition, processing and interpretation. Peter graduated with a Geology (Hons) in 1981 from Stellenbosch University in South Africa. His career has involved seismic acquisition, processing and interpretation of many African, Australian and South East Asian basins' seismic data. His primary interest is to generate gas and oil prospects. To support this, he in-house reprocesses legacy 2D and 3D seismic data from field data to final migration. He is currently reprocessing and interpreting onshore 3D Otway seismic data.

Steve Adams has MSC in Physics with First Class Honours. He has been a Petrophysicist since 1987. Following training and an initial 7 years with Shell, he has worked as an independent consultant with clients in Australasia, Asia, the Middle East and elsewhere. Steve has also worked extensively for reserves auditing companies, including Gaffney-Cline, RPS and RISC. Steve is a member of the Society of Petrophysicists and Well Log Analysts (SPWLA) and the Society of Petroleum Engineers. He has volunteered significant time to the latter organisation over the years on the basis that SPWLA members don’t need to be convinced of the value of petrophysics. Steve has 20 papers published and is well known in the industry as a specialist in Saturation-Height Modelling. His 2016 book ‘Saturation-Height Modelling for Reservoir Description’ has been well received by the industry. In addition, he has been providing petrophysically focussed training courses since 2001.

Jeremy Prosser is a Geologist with over 30 years of experience, largely in the field of clastic sedimentology. Jeremy has a BSc (Geology) and PhD from the University of Aston Birmingham and an MSc from the University of South Carolina. His career started as a Sedimentologist with GAPS Geological Consultants in London in (1988). He then undertook 5 years of post-doctoral studies at the University of Aberdeen before joining Z&S Geoscience (1994), working on borehole image data. He established the Z&S office in Perth, WA (1996–1998), subsequently spending 8 years with Baker Atlas as their Asia Pacific Geoscience Manager and finally Asia Pacific Sales Manager before joining Task Geoscience in 2006. He is currently Task Fronterra Geoscience’s Global Business Development Manager, and his primary interest is using borehole image data for reservoir characterisation.


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