白云深水区东部油气成因来源与成藏特征

白云深水区东部位于珠江口盆地珠二坳陷白云凹陷东部深水区,是一个发育文昌组、恩平组、珠海组3套有效烃源岩、早中新世富砂深水扇和晚渐新世陆架浅水三角洲储盖组合及构造—岩性圈闭的复合油气成藏区。油—岩特征生物标志化合物的对比结果和原油轻烃组成特征表明,LW3-1、LH34-2构造所产凝析油和原油及LH29-1构造气藏所产凝析油主要来自白云主洼恩平组烃源岩,LH29-1、LH16-2构造油藏所产原油主要来自白云东洼恩平组烃源岩,该区凝析油和原油有珠海组烃源岩的贡献。天然气主要源自白云主洼恩平组烃源岩干酪根裂解气,有文昌组烃源岩生成的原油裂解气的贡献。白云深水区东部油气成藏带主体有两期成藏,早期聚油,晚期聚天然气及凝析油,主成藏期在粤海期—现今,LH29低凸起成藏带油藏遭受气洗。白云深水区东部存在的5个断裂带、流体底辟是垂向输导体,区域砂岩层、不整合面与构造脊耦合形成侧向运载层,共同控制该区成藏带的有效烃源灶位置与运聚。

Origins and Accumulation Characteristics of Hydrocarbons in Eastern Baiyun Deepwater Area

Eastern Baiyun Deepwater Area, located at eastern deepwater area in Baiyun Sag of Zhu II Depression in Pearl River Mouth Basin, is a multiple hydrocarbon generation and accumulation area where three sets of effective source rocks, Wenchang, Enping and Zhuhai formation, early Miocene sand-rich deepwater fan, late Oligocene continental shelf shallow water deltaic reservoir-cap assemblage and structural-lithologic traps, have developed. Based on oil-source correlation of biomarkers and light hydrocarbons data from crude oils, it was concluded that the crude oil and condensate oils in LW3-1 and LH34-2 traps and the condensate oil in LH29-1 gas reservoir mainly generated from Enping Formation source rock in main subsag of Baiyun sag, however, the crude oils from LH29-1 and LH16-2 oil reservoirs mainly generated from Enping Formation source rock in eastern subsag of Baiyun sag, with some contribution of oil generating from Zhuhai Formation source rock. Natural gas is mainly generated by kerogen-cracked gas from Enping Formation source rock in main subsag of Baiyun sag, with the contribution of oil-cracked gas from Wenchang Formation source rock. There are two stages of hydrocarbon accumulation in Eastern Baiyun deepwater area, with the early stage characterized by oil accumulation and late stage by gas and condensate oil. Yuehai period to present is the main accumulation period in Eastern Baiyun deepwater areas. Some oil reservoirs in low uplifts have undergone gas washing. Five fault zones and some fluid diapers developed in Eastern Baiyun deepwater area constitute important vertical migration pathway systems. Regional sandstone, unconformable surface and structural ridge are lateral pathways. They controlled the location of effective source kitchen, the hydrocarbon migration and accumulation together.