MAPPING BASEMENT AND BASEMENT FAULTS FOR PREDICTION OF POTENTIAL BASEMENT RESERVOIRS USING SEISMIC ATTRIBUTES IN WESTERN BASIN, GULF OF THAILAND

Abstract

The Permian Ratburi carbonate basement is a productive Pre-Tertiary karstified carbonate reservoir in the Gulf of Thailand, specifically in the Nang Nuan Oil Field in Chumphon Basin. However, its neighboring Western basin basement has yet to be extensively explored and studied. The integration of 3D seismic data, logging data of five wells as well as seismic attributes were used to identify the basement structural pattern and fault features in this study area located in Western basin. A depth structural map was generated for the top of basement formation. The basement is influenced by numerous N-S trending normal faults that have formed two block-faulted half-grabens in the structure. The faults are characterized by high-angle normal faults that become low-angle faults as they go into the basement. Some of these faults also show fault reactivations that have a higher displacement compared to the overlying sediments. Seismic attributes such as structure-oriented filter (SOF), relative acoustic impedance (RAI) and variance (edge) method attributes proved effective to enhance the basement images and fault features in this basin. High porosity zones were illustrated by high amplitude anomaly evaluated from the root-mean-square (RMS) amplitude attribute, mainly seen along the basement ridges. In conclusion, the structural highs with predicted higher porosity zones of the study area in Western basin are of interest as it shows better opportunities for potential hydrocarbon exploration as supported by the results in this study.