Present-Day Two-Dimension Maturity History Modelling of Source Rocks from the Central Region of the Andaman Sea Back Arc Depression

Abstract

Basin modelling is an essential research tool that aids geologists improve the description and analysis of subsurface activity. The central region of the Andaman Sea back arc basin is a potential oil and gas prospect. Herein, two-dimension present-day maturity models are constructed from four seismic sections of the study area using Basin Mod™ software (Platte River Associates, Inc. of USA). Designated study areas are the South to North Moattama Basin, western Moattama to the Mergui Shelf, Western to Eastern Moattama basin centres through Eastern Moattama basin centre to the Eastern section of Mergui basin and Eastern Andaman Sea Basin to Western Mergui Basin. The two-dimension (2D) maturity models are generated from known data burial and geothermal data. Vitrinite Reflectance (Ro%) which is the main variable in determining source rock (s) maturity showed that the source units were within the oil (0.5% ≤ Ro ≤ 1%) and gas (1.3% ≤ Ro ≤ 4.5%) and had commenced generation of some quantities of hydrocarbons. Data analyzed revealed that most portions of the Oligocene and Lower Miocene shales source units in all study areas buried below 2000 m are matured to generate oil and / or gas. The outcome of modelling also indicated that source units from the Moattama Basin center and the Mergui Basin were mostly matured to produce some form of hydrocarbons, principally gas or dry gas. However, no oil expulsion into limestone reservoirs was observed; only gas or dry gas.