SEISMIC EVIDENCE FOR REVERSE AND WRENCH FAULT TECTONICS—CLIFF HEAD OIL FIELD, PERTH BASIN

摘要

Seismic interpretation of the Cliff Head oil field has shown it to be structurally complex with reverse faults, wrench faults and listric faults mapped at both field and reservoir scale within the Permo-Triassic section. The Cliff Head field overlies the Abrolhos Transfer Zone and has strong similarity to the progressive evolution, internal structure and rhomboid map geometry in experimental models of restraining stepovers in strike-slip systems. It is concluded that the Cliff Head oil field is a pop-up structure formed during the Permian and early Cretaceous within a restrained convergent wrench system—the result of sinistral transpression. A similar style of faulting could be applied when mapping seismic data in other offshore areas and especially the onshore Perth Basin with its poorer seismic data quality. Interpretation of prospects with a strong reverse or wrench component has implications for the timing of hydrocarbon emplacement and the potential for seal breach and leakage. Furthermore, paleo-structural style will determine fracture density and orientation and may be critical in determining optimum design of producer and injection wells during field development. It is recommended that interpreters of seismic data in the Perth Basin treat the fault patterns and structural trends of the Permian and early Cretaceous as different structural packages. The two should only be linked when it is very clear that there is a strong early Cretaceous overprint.