Compound hydrocarbon accumulation and enrichment in southwestern Huizhou Sag, Pearl River Mouth Basin, South China Sea

Aimed at four major issues in the oil and gas exploration of the southwestern Huizhou area in Pearl River Mouth Basin, in-depth study on geologic features and oil and gas reservoir forming pattern has been carried out to find out the exploration potential and direction of compound oil and gas reservoirs in this area. There develops the compound formation structure of basement, rifting and depression layers in this area, and a composite hydrocarbon transport system comprised by faults, sandstone layers and the sequence boundaries, which are connected to the several hydrocarbon generation subsags in the adjacent Huixi half graben. Controlled by the subsag- controlling boundary faults, long inherited paleo-uplifts and ancient structural ridges, oil and gas accumulate in multiple series in vertical direction, multiple connected traps horizontally, forming compound reservoirs of various traps. According to the three types of structural zones controlling oil and gas enrichment, the southwestern Huizhou area can be divided into seven compound oil and gas accumulation zones in three categories, which combine into a large compound hydrocarbon accumulation province.