Abstract

An extensive study of the Papuan Basin was made daring 1983-84 by Robertson Research (Australia) Pty Ltd and Flower Doery Buchan Pty. Ltd. on behalf of the Geological Survey of Papua Hew Guinea to provide coherent petroleum exploration concepts with the intent of stimulating future exploration. The study included the reinterpretation of about 35,000 km of seismic reflection data recorded between 1959 and 1983, together with a critical re-evaluation of well data.

An important feature of this reinterpretation was the identification of widespread wrench faulting on the Fly Platform that had not previously been recognised. The faulting occurs primarily in two parallel wrench fault systems. The Komevu Wrench System extends northwesterly across the northern Fly Platform for about 500 km to the Irian Jaya border near Kiunga-1 well. The smaller, less well-defined Fly Wrench System lies southeast of the Lake Murray High and trends in a similar direction over a distance of 140 km. Other evidence of wrench faulting in areas of predominantly extensional tectonics is recognised in the Morehead Sub-basin an in the Darn Embayment.

Wrenching along these zones took place in the Late Cretaceous to Paleocene as a result of the relative left-lateral movement of the Pacific and Indo-Australian plates. The effects become progressively weaker to the southwest, away from the zone of in-teraction. Rejuvenation of the faulting occurred during the Miocene as the relative movement of the two plates became more convergent.

These newly recognised wrench fault systems present an entirely original set of petroleum plays, including en-enchelon anticlinal trends and up-dip closure against faults. Good seals and reservoir rocks are present. Only one well so far, Kiunga-1, has been drilled on a valid structure related to these wrench systems, this well produced shows of oil and gas from separate reservoirs.