REGIONAL FACIES AND GEOCHEMICAL EVALUATION OF THE SOUTHERN DENISON TROUGH, QUEENSLAND

Abstract

Results of geochemical investigations by the Bureau of Mineral Resources (BMR) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) indicate significant potential for hydrocarbon source throughout the Permian sequence with the Cattle Creek Formation (shallow shelf mudstone and shale facies, and prodelta mudstone facies) and the Reids Dome Beds (fluvial flood basin facies) constituting the most favourable source rock facies. The source rock facies comprise dominantly humic organic matter indicating that the Permian source is mainly gas-prone. The existing mature organic zone within the trough encompasses much of the Cattle Creek Formation and a section of the Reids Dome Beds; this suggests that present-day hydrocarbon generation may be taking place within these source rocks.

A complementary regional facies analysis by the Geological Survey of Queensland (GSQ) demonstrated a relationship between hydrocarbon-bearing reservoirs and facies types. Clearly distributary channel, tidal, beach and barrier bar facies constitute the most favourable reservoir facies. Within the interval covered by the Cattle Creek Formation and Aldebaran Sandstone, juxtaposition of source and reservoir facies has been recognised and could present favourable stratigraphic traps. Three zones are recognised:

an area extending from Rolleston to Westgrove;within the Kildare area; andan area extending from GSQ Taroom 10 to AAO Kia Ora 1.

These zones deserve further consideration. Results of this integrated investigation lends optimism to further exploration.