STRUCTURAL ZONATION AND HYDROCARBON ACCUMULATION MODEL OF THE SUMATRA BACK ARC RIFT BASIN

The Sumatra back-arc rift basin is the largest oil and gas producing province in Indonesia and Southeast Asia. Since the exploration degree of the region is quite high already, new exploration results are pretty rare in the past ten years, and thus the hydrocarbon discovery in the basin has entered a bottleneck. In order to find out the target areas for future exploration in the basin, we studied the tectonic pattern of the basin and its control over the distribution of source rocks and reservoirs. Upon the basis, the future exploration direction of the back arc rift basin is discussed. According to tectonic features, the Sumatra back-arc rift basin can be subdivided into three structural belts namely the near island arc belt, the central inversion belt and the distant island arc belt. The near island arc belt, in fact, is an inherited uplift. Oil and gas migrate vertically mainly through faults and accumulate in high-stand traps such as reefs and anticlines. The buried-hill trap is the major exploration target for future in the belt. The central inversion belt is dominated by semi-grabens and shovel-like normal faults. Oil and gas come from deep depressions and accumulated in the multi-layer reservoir in the upper part. Both fault and sand body act as the pathway for oil and gas migration. Buried-hill and structural-lithological are the main traps for hydrocarbon accumulation. The distant island arc belt is dominated by monoclinic strata locally with visible depressions which have hydrocarbon generation potential. Lithological hydrocarbon reservoirs occur in the belt and there is a great potential for future hydrocarbon exploration.