Abstract

Results from an integrated geochemical and sedimentological study of the Oligocene to Early Miocene Talang Akar Formation suggest that the North Seribu Trough (NST) in the offshore NW Java basinal area is a hydrocarbon generative center. The presence of good source rocks, adequate maturity, and excellent quality reservoir rocks in conjuction with anticlinal, fault and stratigraphic traps in the NST and adjacent flank areas have created new exploration opportunities.

Based on stable carbon isotope composition and biomarker distributions, a new type of oil has been recognized. The NST oils differ from established oil families of the Ardjuna Subbasin and South Seribu Trough. They were probably generated from a lacustrine facies of the Talang Akar Formation, located within the central NST depocenter. A thick section of mature source rock is predicted.

Detailed core and wireline log analyses indicate that thick reservoir-quality sandstones of deltaic and lacustrine origin were developed in areas where the source rocks were deposited. The interbedded nature of reservoir and mature source rocks has increased the efficiency of hydrocarbon migration.

The results of this study, especially the geochemical analyses, have led to the discovery of a new generative center and redirected the exploration strategy in this area.