Petroleum accumulation characteristics and favorable exploration directions in Wenchang B Sag and its surrounding areas, Pearl River Mouth Basin

Based on source rock analysis,oil—source correlation and accumulation comprehensive analysis,oil source and accumulation process in the Wenchang B Sag and its surrounding areas were studied.Main source rock and hydrocarbon accumulation features in different regions were illustrated.Main controlling factors of hydrocarbon accumulation and favorable exploration directions were pointed out.Sha-llow lacustrine source rock of the Wenchang Formation in the Wenchang B Sag was the main contributor for accumulation in uplifting region besides the well-known middle—deep lacustrine source rock.At the end of deposition,lacustrine source rock of the Wenchang Formation in the downthrow of southern fault experienced tectonic inversion,resulting in the delay of oil generation and expulsion as well as the multi-stages of oil charging.The downthrow of fault No.3 was also characterized by early oil generation and expulsion as well as multi-stages of oil charging.Favorable lacustrine source rock of the Wenchang Formation,multi-stages of fault activities and sets of reservoir—caprock assemblages worked as the main controlling factors for hydrocarbon accumulation.Favorable exploration directions were pointed out,including the inverse abrupt slope and the middle—deep buried Paleogene of the northern slope in the Wenchang B Sag as well as the first member of Zhujiang Formation in the Qionghai uplift.