Abstract

The Sebuku PSC contract area in Indonesia lies between Kalimantan and Sulawesi. There have been four phases of exploration history in Sebuku from 1966 to 2003. Only two wells in the block that were tested demonstrably closed structures encountered hydrocarbon accumulations, Makassar Straits-1 gas and Pangkat-1 oil discovery wells. The Sebuku Block is part of the SE Sunda shield structural framework. There are few types of reservoir rocks in the Sebuku Block including the Berai Carbonate, Lower Tanjung Sandstone, Fractured Basement and Upper Warukin reefal build-ups. Two potential source rocks have been identified in the Lower Tanjung Formation, the lacustrine shale and the fluvio-deltaic shale and coal. The hydrocarbon were cooked in the Makassar Graben which a depth to basement in the depocenter of more than 15,000 feet. The maturity model shows that the lacustrine shale entered oil window (Ro 0.5%) in Early Oligocene time followed by the fluvio-deltaic shale and coal in the oil window (Ro 0.5%) in Late Oligocene time. There are two regional seals, Marl & Shale of Upper Tanjung Formation and Shale of Lower Warukin Formation. Lateral migration initially begun along the basement-sediment interface gradually rising to younger sequences via overstep while vertical migration occurred along faults or high sand/shale ratios. The main traps are basement drapes (early) and inversion (late) and stratigraphic reefal traps.

Presented at: 2005 South East Asia Petroleum Exploration Society (SEAPEX) Conference, Singapore, 2005