PIGOTT, JOHN D., The University of Oklahoma, Norman, OK; * DOUGLAS G. NEESE, Maxus Energy Corp., Dallas, TX; and ANDREW B. CULLEN, Pecten International, Houston, TX

ABSTRACT: Northern New Guinea Hydrocarbon Potential: New Constraints from Tectonic Subsidence Analysis and Seismic Stratigraphy

Tectonic subsidence analysis of boreholes north of the Bewani-Torricelli-Prince Alexander Mountain (BTPA) range of Northern Papua New Guinea reveals rapid post-Eocene tectonic subsidence punctuated by two distinct episodes of tectonic uplift. These pulses resulted from near-field changes in strain produced by segmented evolution of the sinistral Northern New Guinea wrench fault system. Periods of slow tectonic subsidence are marked by carbonate-dominated sediment deposition whereas episodes of greatest tectonic subsidence are predominately siliciclastic. Our outcrop-to-borehole reconnaissance demonstrates that these sequences are primarily fine-grained, protected shelf-to-slope facies with uncommon biolithites, grainstones, and coarse-grained siliciclastics.

Seismic-stratigraphic analyses demonstrate that, prior to the Pliocene, the North New Guinea basin was represented by one widespread axial feature which segmented into the Piore and Sepik basins during the Pliocene uplift of the BTPA mountains. Therefore, pre-Pliocene seismic sequences occur on both sides of the BTPA range. Both basins are overprinted by a variety of transpressional fault structures proximal to the Northern New Guinea Fault system.

Maturity modeling incorporating this geo-history analysis indicates that the Tertiary stratigraphic package is immature, consistent with observed low present-day geothermal gradients. Present day oil seeps in Northern New Guinea are anomalous when compared to these computations. We suggest two hypotheses: Either the oil was generated as a result of local (igneous)thermal events, or as our seismic data suggests, the oil migrated along conduits associated with major thrust fault systems from deeper buried source rocks to the south.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.