STRUCTURAL EVOLUTION OF THE PERMIAN-TRIASSIC COOPER BASIN, AUSTRALIA - RELATION TO HYDROCARBON TRAP STYLES

The structural and depositional history of the Cooper basin in eastern central Australia has revealed that the basin is a mildly compression al structural depression controlled by northwest-trending and northeas t-trending pre-Permian basement features. Pronounced pre-Permian compr essions are indicated by northeast-trending major structures, the Gidg ealpa-Merrimelia-Innamincka and Murteree-Nappacoongee trends. Detailed chronostratigraphic facies analysis, with closely spaced palynologica l control, of the Patchawarra Formation revealed that two pronounced p hases of uplift occurred during the Sakmarian. The major intrabasin hi ghs were rejuvenated during these tectonic events, as documented by cr estal unconformities (middle and upper Patchawarra unconformities). Ev idence of each event is dominantly tectonic in character, with similar depositional patterns over these highs related to each event. These e vents are also recognizable in mid-flank areas and basin margins with contemporaneous deposition in deeper parts of the basin.Results from t his research show potential for future hydrocarbon discoveries within structural, stratigraphic, and structural/stratigraphic traps in the C ooper basin. Various trap styles are closely associated with faults, u nconformities, and lateral facies changes. Lowside fault closures, onl ap plays, and unconformity traps are expected to be well developed alo ng intrabasinal highs, basin margins, and preexisting structures. The primary reservoir targets would be deltaic sequences comprising shorel ine sandstones, distributary and delta-mouth bar deposits that may be well developed in synclinal areas, and flanks of intrabasin highs in t he Cooper basin.