HYDROCARBON GEOLOGY IN NW SABAH BASIN AND CONTROLLING FACTORS ON HYDROCARBON ACCUMULATION

The NW Sabah Basin is one of the major exploration targets in Southeast Asia. With hydrocarbon geological theory as the guide, the distribution and maturity of source rocks, reservoirs, cap rocks and traps in different tectonic zones are studied, and the main controlling factors on hydrocarbon accumulation also discussed in this paper, on the basis of structural and stratigraphic studies. It is proved that the mudstones and shale in the StageⅣ are the main source rocks and the main clastic reservoirs are provided by the Lower Sandstone Unit of Stage ⅣA, the Upper Sandstone Unit of Stage ⅣC and ⅣD, and the turbidites of Stage ⅣC and ⅣD. Three reservoir-seal combinations, i.e. the lower, upper, and deep-water turbidite fan combinations, have been identified, and the lower one is best among the three. Source rocks and reservoirs are distributed in different tectonic areas under the control of tectonics and palaeogeography. Various traps are developed in different tectonic areas by the distinct deformation effect, which controls as well the formation and distribution of oil accumulation in the basin.