Petroleum Systems of the Eastern Margin of the Enderby Terrace, Dampier Sub-Basin, Carnarvon Basin
Findlay, Ross A.
Masters of Science Degree, 2006
University of Adelaide
This study examines the petroleum systems in the eastern part of the Dampier Sub-Basin - bounded by the Lewis Trough to the north and the coastline of Western Australia to the south. In particular it concentrates on Strike Oil’s blocks WA-261-P, WA-340-P, TP/19 and EP 421. Key seismic horizons – the Aptian Unconformity, the Base Creataceous Unconformity, the top of the Mungaroo Formation and the top of the basement were mapped across the study area.
Geochemical analysis of oils and condensates in the area has concluded they have come from the W. spectabilis interval of the Dingo Claystone. Existing maturity studies were augmented by basin modelling of wells near to the acreage. It was determined that this source interval only reaches sufficient depths for significant petroleum generation in the area of the Lewis Trough, so long range migration is required to charge the area of interest.
Throughout the study area several reservoirs have been identified including the M. australis Sand, Neocomian Sands, Legendre Formation, Intra Athol Sands, Mungaroo Formation and the Base Locker Sand. All of these, with the exception of the Legendre Formation, are thought to be present in Strike Oil’s blocks. The Muderong Shale, the Athol Formation and the Locker Shale are all potential seals within the acreage. There are potential traps within the lower Cretaceous and the Athol to Mungaroo Formations with some potential for additional Base Locker Sand plays.
The presence of fluorescence and hydrocarbon shows encountered in wells throughout the study area proves that there has been migration through these areas. Migration has occurred at lower Cretaceous, Jurassic and Triassic levels. Potential migration pathways from the source kitchen to Strike Oil’s blocks have been identified and there is evidence of migration at Jurassic levels over long distances.
There is considerable uncertainty as to the presence of all of the petroleum system components in blocks WA-261-P, WA-340-P, TP/19 and EP 421 and any drilling in the area would be high risk. The petroleum component with the greatest uncertainty appears to be the presence of a migration pathway. It is recommended that a 2D or 3D basin model is constructed to investigate this further.