PETROLEUM SOURCE ROCK AND MIGRATION IN THE MERGUI BASIN, THE ANDAMAN SEA, THAILAND: PREDICTION FROM AN ORGANIC GEOCHEMISTRY STUDY USING THE PETROMOD PROGRAM
Keywords:
Petroleum source rock, migration pathway, PetroMod, Mergui basin, the Andaman SeaAbstract
The main objective of this research is to identify petroleum source rock and the petroleum migration path of the Mergui basin, Andaman Sea, Thailand. An assessment of the petroleum generation was performed by a geochemical analysis of the rock and running the basin modelling using commercial computer software named PetroMod, whilst the migration path was determined by the porosity of the Ranong Formation and the thermal maturity of the sediments. The results of the study indicated that source rocks were present in the Yala, Kantang, and Trang Formations but were immature throughout the basin. Only the Yala Formation could be properly exploited to generate petroleum. The petroleum source rock of the Yala Formation is marine shale which has total organic carbon values ranging between 0.5 and 1.5%. Its organic matter is Type III terrestrial, which represents a gas prone kerogen, whilst its thermal maturity has a vitrinite reflectance (Ro) range between 0.6 and 1.0; the Tmax of the Yala formation is in the range between 430oC to nearly 450oC and its production index ranges between 0.1 and 0.4. The oil window lies around 2100 m, 3000 m, and 4500 m in the north Mergui basin, main Mergui basin, and Andaman slope areas, respectively. The Oligocene to early Miocene period Yala Formation is mature over most of the basin. From the results of the potential of the reservoir in the Ranong Formation with its thermal maturity, thegeothermal gradient in the basin indicated that the hydrocarbons’ expulsion and migration were believed to have taken place mainly beginning around the middle Miocene period and still continue today. Hydrocarbons are primarily being generated and are migrating from the deep east Mergui, west Mergui, and Ranong troughs.
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