VIMP Report 74 - Hydrocarbon prospectivity of areas V02-2, V02-3 and V02-4, offshore Gippsland Basin: 2002 Acreage Release
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Product description:Download The downloadable version of this report is supplied in PDF format. Executive Summary The Gippsland Basin is situated in southeastern Australia, located about 200 km east of the city of Melbourne, and is well serviced by roads and population centres. About two thirds of the basin lies offshore representing one of Australia's most prolific hydrocarbon provinces. Initial proven reserves were estimated at 4 billion barrels of oil (Bstb) and 10 trillion cubic feet (Tcf) of gas. The basin currently supplies (as at November 2001) 27% of the nation’s oil demand and most of the State of Victoria’s gas requirements. The remaining resources (at P50 level) have been assessed at 600 million barrels of liquids (Mstb) and 5 Tcf gas, much of which is likely to occur in deeper stratigraphic units. Most of the discoveries to date have been hosted within the Late Cretaceous to Early Tertiary Latrobe Group. Onshore and offshore, the Gippsland Basin has over 80 000 km of 2D seismic data, more than 25 3D seismic surveys and a density of approximately one well per 50 km². Although a mature basin by comparison with other Australian basins, by world standards the Gippsland Basin is still considered to be relatively under-explored. A network of pipelines brings produced hydrocarbons to the onshore petroleum processing facilities at Longford. From here, new pipelines were recently commissioned to deliver Gippsland gas to Sydney in New South Wales, to Adelaide in South Australia and to Tasmania. The potential for additional discoveries will ensure continued interest in the region, which will also be maintained by several other factors. Among these are increasing gas market demand in the SE Australian region and deregulation and reform of the upstream and downstream gas industry during recent years. The latest gazettal rounds in the Gippsland Basin have resulted in a number of new acreage awards outside the production licences traditionally held by the Esso/BHP Petroleum joint venture. Increased interest is being expressed by various companies, spanning both large and small petroleum industry players and may be attributed to factors ranging from improvements in technology to the changing economic and regulatory environment. The three offshore areas described in this report were partly explored by previous operators who identified several prospects and leads. All areas offer significant opportunities for hydrocarbon entrapment in several different play types. Area V02-2 lies to the north of the Turrum/Marlin and Sunfish oil and gas fields, extending across the Rosedale Fault System onto the Northern Terrace and Northern Platform. Play types in this block are dominated by structural traps in the southern portion and stratigraphic pinch-outs, involving a thinning Latrobe Group, in the north. Sufficient well-control and seismic coverage in the area and its immediate vicinity has provided valuable insights into the distribution of reservoir and seal rocks. However, the source rock intervals have not yet been unambiguously identified and the exact migration history is only poorly understood. The Patricia/Baleen gas field and the Sperm Whale discovery provide analogues for top-Latrobe Group accumulations on the Northern Terrace. Fluvial sandstones with good porosities are the dominant reservoir facies, however, the marine Gurnard Formation, generally a fine-grained, glauconitic unit, is known to host commercial quantities of gas in Patricia/Baleen. The Longtom discovery is a significant, non-commercial gas accumulation in the sandy facies of the Emperor Subgroup. Lead 2a is a downthrown fault-trap involving fluvial intra-Latrobe sandstones as tested at Sperm Whale-1 which may be similar to the Patricia/Baleen reservoirs. Depending on how far north sediments of the Emperor Subgroup are preserved, fluvial/alluvial sandstones of P. mawsonii age could be developed immediately to the south of the Sperm Whale discovery. This would represent a play that is equivalent to the Longtom discovery. Leads 2b and 2c are traps of Emperor Subgroup sandstones that onlap onto the Strzelecki Group with possible reliance on fault closures. Lead 2d is an upthrown fault structure in the Emperor Subgroup and bears similarities to the Longtom discovery. Lead 2e is likely to be a top- and intra-Latrobe Group compressional rollover structure over an erosional remnant, similar to that of Sunfish/Remora field. Lead 2f is a similar feature to Remora that resulted from combined extensional and compressional deformation and subsequent erosion. Lead 2g is a complex feature adjacent to the Rosedale Fault System between the Sunfish/Remora and Tuna fields. Area V02-3 is located between the Patricia/Baleen and Sole gas fields and extends from the Northern Platform across the Northern Terrace into the Central Deep. This gazettal block is geologically the most diverse of the 2002 Gippsland acreage providing opportunities for shallow plays on the Northern Terrace, a variety of structural plays in the vicinity of the Rosedale Fault System as well as deep-Latrobe Group plays in the southernmost portion of the block. Petroleum geological control for Area V02-3 is provided by hydrocarbon accumulations at Patricia/Baleen, Leatherjacket, Sole, Kipper and Basker/Manta/Gummy and by the five exploration wells Wahoo-1, Sweep-1, Leatherjacket-1, Admiral-1 and Hammerhead-1. Across the block, hydrocarbon traps are likely to exist in fault-dependent closures along the Rosedale Fault System involving both top- and intra-Latrobe Group sediments. Erosional top-Latrobe Group remnants of marine channel incision may represent stratigraphic traps. The Basker/Manta/Gummy Field can be used as an analogue for expected intra-Latrobe plays. Overall, three play types can be distinguished:
Previous mapping identified two leads. One features an erosional remnant at the top-Latrobe Group, similar to the Flounder Field, the other is a downthrown fault-trap with intra-Latrobe fluvial reservoirs, similar to the Basker/Manta/Gummy Field. While source rock potential should not be a problem in this block, the target intervals are likely to be located in deeper water areas and may therefore be deemed high risk. In summary, the three 2002 offshore gazettal blocks provide excellent investment opportunities, catering for the big as well as the smaller exploration companies. The Gippsland Basin has the distinct advantage of being positioned close to expanding infrastructure and markets. The basin is currently undergoing a resurgence in exploration activity and some major efforts are being undertaken to identify the many hidden oil and gas accumulations. Bibliographic reference Bernecker, T., Wong, D., Driscoll, J. & Liberman, N., 2002. Hydrocarbon prospectivity of areas V02-2, V02-3 and V02-4, offshore Gippsland Basin, Victoria, Australia: 2002 Acreage Release. Victorian Initiative for Minerals and Petroleum Report 74. Department of Natural Resources and Environment. | ||||||
