渤海海域莱州湾凹陷沙三段水道型湖底扇发育特征与沉积模式

Development Characteristics and Sedimentary Model of Sublacustrine Fan of Channel Type in the Third Member of Shahejie Formation in the Northern Laizhou Bay Depression, Bohai Sea Area

基于已钻井、测井和三维地震资料,分析了莱州湾凹陷沙三段水道型湖底扇砂体的沉积特征,并探讨其成因及发育模式.研究区沙三中亚段早期砂体成因为湖底扇沉积,并表现出水道型特征,可划分为叠覆型水道及其侧翼、复合型水道及其侧翼和单一水道及水道间等沉积微相类型.顺源条带状展布的叠覆型水道和复合型水道构成湖底扇骨架砂体.湖底扇水道类型和规模受控于物源富砂程度、同沉积断裂坡折带类型和古地貌变化.其中,物源富砂程度决定了湖底扇外部形态,同沉积断裂坡折带类型和古地貌变化进一步控制湖底扇发育位置和水道规模及其类型.水道型湖底扇具有近油源、储盖组合良好和油气运聚条件优越等特点,是岩性油气藏勘探的重要目标.

Based on the well-drilled, well logging and 3D seismic data, the sedimentary characteristics of sandbodies in the third member of Shahejie formation in Laizhouwan sag were analyzed, and the genesis and development model were discussed. The results show that the sandbodies in the early middle member of the third member of Shahejie formation in the study area are formed by sublacustrine fan deposits, which show channel type characteristics. The sublacustrine fan deposits can be subdivided into sedimentary microfacies types such as superimposed channel and its flanks, compound channel and its flanks, single channel and interchannel. Sublacustrine fan framework sand body is composed of superimposed channel and compound channel. The type and scale of the waterway from south to north are controlled by the degree of provenance and sand enrichment, the type of slope break zone of synsedimentary fault, and paleogeomorphology changes. The degree of provenance sand enrichment fundamentally determines the external shape of the sublacustrine fan. The type of slope break zone and paleogeomorphologic change of synsedimentary fault further control the location, channel size and type of the lake floor fan. Watercourse type lake-bottom fan is an important target for lithologic reservoir exploration because of the excellent hydrocarbon migration and accumulation conditions near oil source and good reservoir-cap assemblage.