ABSTRACT: Geology and Hydrocarbon Potential of the Sepik-Ramu Area, Ramu Basin, Papua New Guinea

James C. Donaldson, J. Thomas Wilson

Improvements in seismic processing have made new interpretations of the structural and depositional history of the northwestern portion of the Ramu basin possible. Support for a wrench tectonic model for this area is observed in the reprocessed seismic data. Strike-slip movement along major fault zones has allowed compressional forces to be translated laterally and resulted in only minor deformation occurring in the Sepik-Ramu area. The major tectonic event is thought to have occurred during late Miocene-early Pliocene, and not during the middle Miocene, as earlier hypothesized. Consequently, Miocene deposition is postulated to have occurred uninterrupted by periods of erosion.

A thick Miocene section is preserved in this region and is postulated to contain slope, reef, and shelf carbonates of early to middle Miocene age. This interpretation has led to the identification of a reef trend over 7 mi wide and at least 42 mi long containing numerous pinnacle reefs. The pinnacle reefs are analogous to those found in the Salawati basin of Irian Jaya, Indonesia. The reefs are overlain by deep-water shales, a combination that provides potential reservoirs and seals necessary for the entrapment of hydrocarbons. The presence of oil and gas seeps document the existence of a source. These three factors justify hydrocarbon exploration in this area. The numerous potential drilling targets may lead to the discovery of significant quantities of hydrocarbons.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990