Integration of Gas Chimney Processing and Fault Stress Analysis to Evaluate Top Seal Integrity in the Gippsland Basin, Australia

Abstract

Gas chimney processing was applied to a merged 3D seismic dataset in the Flathead, Galloway, and Seaspray areas of the near-shore Gippsland Basin, Australia. The study covered the Whale Harlequin, and Amberjack dry holes, and the Perch and Seahorse oil fields. One objective of the study was to determine if the dry or sub-commercial wells were due to top seal failure or other reasons (water flushing or trap timing). The chimney detection process uses a neural network trained on multi-trace attributes calculated on reliable picked examples of chimneys and non-chimneys. A well documented gas chimney in the Flathead area was used for neural network training to detect chimneys in the Galloway and Seaspray areas, where obvious chimneys had not been seen. The results of the processing showed the presence of chimneys associated with East –West trending faults in the primary reservoir Latrobe Formation. A regional fault stress analysis showed that these faults had a greater slip tendency, and were thus at a higher risk for vertical fault seal failure. The results of this current study show that these faults are a conduit for vertical hydrocarbon migration, which may provide charge to the oil fields. However, with the exception of the Whale dry hole, these chimneys die out in the overlying Lakes Entrance Formation, which is the major regional seal. Thus, based on the chimney analysis, the other dry holes are probably not due to top seal failure, but other causes like water flushing.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015