Trapping Mechanisms along North Similan and Lanta Trends, Pattani Basin, Gulf of Thailand

Abstract

Nine exploration wells along the Surin, Lanta, and North Similan structural trends in the northern Pattani Bain show significant variations in pay. To try to understand these variations in pay, analysis of the variations in the petroleum system elements in the area was studied with particular emphasis on trapping mechanisms. 3D seismic data, wireline logs and geochemistry data were used for this study. In the Pattani Basin, the first critical factor of the petroleum system is the structural trap. Wells should be drilled within structural closures to encounter hydrocarbon pays. However, pay count numbers vary considerably even in wells drilled on closed structures. For these wells fault sealing capacity was determined in this study to be the next critical factor that controls variations in hydrocarbon pays. Wells that have high sand- shale juxtapositions tend to have high pay count numbers whereas wells that have high sand- sand juxtapositions tend to have low pay count numbers. The third critical factor was determined to be the length of migration pathway or the distance from mature source rocks. The wells located near mature source rock tend to have higher pay counts on the east side where source rocks have higher maturation based on 1D maturity modeling. Sand distribution does not appear to be a factor in influencing the hydrocarbon pay count. From this integrated analysis, the best area for high pay potential is the eastern basinward side of the study area.