Talang Akar-Cibulakan(!) Petroleum Systems, Arjuna Basin, Offshore Northwest Java, Indonesia

Chanda Suria, S. W. Sinclair, A. R. Livsey, and M. J. Gresko

The Talang Akar-Cibulakan(!) petroleum systems occur in the Arjuna basin, one of a series of basins on the southern edge of the Sunda craton originating during a major Eocene-Oligocene period of extension. Total in-place hydrocarbons of 2.5 BBO and 3 TGFG have been discovered since 1968. Over 1000 wells have been drilled, and 1 BBO and 1.1 TCFG have been produced from 70 fields. Major reservoirs are Upper Oligocene to Lower Miocene fluvial sandstones of the Talang Akar Formation and Middle to Upper Miocene shallow-marine sandstones of the Cibulakan Formation.

Geochemical analyses indicate that Talang Akar coals and shales are the principal source of hydrocarbons in this prolific petroleum systems. This source interval has thicknesses from <125 m on flanks and highs to >600 m in the axis of the basin. These source rocks contain mainly terrestrially-derived organic mater but source quality varies considerably. Carbonaceous shales are mainly gas prone while liptinite-enriched coals are good oil and gas source rocks. Geohistory modelling indicates that hydrocarbon generation was initiated by Middle Miocene (15 mya) and reached its peak at Upper Miocene (10 mya). Primary migration at Middle Miocene resulted in hydrocarbon charge of interbedded reservoir rocks. Secondary migration since post-Upper Miocene, concurrent with renewed tectonism has been mainly vertical through fault-related fractures. Basin-wide source rock and hydrocarbon characteristics, in combination with structural and stratigraphic framework, define these supercharged and vertically drained petroleum systems.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California