西湖凹陷西斜坡平湖组烃源岩沉积成因分析

西湖凹陷西斜坡是东海盆地当前油气勘探的现实选择和主要领域,但以往研究在烃源岩形成条件和分布规律等基本地质问题方面尚未形成共识.在沉积学、煤岩学和有机地球化学等理论指导下,利用钻井、烃源岩有机地球化学及古生物等资料,对西湖凹陷西斜坡钻井揭示的平湖组烃源岩成因类型和形成条件进行了全面系统分析,建立了与沉积环境相对应的有机相划分方法,并总结了平面分布规律.研究表明,烃源岩主要为煤系烃源岩,次要为海相泥岩;西斜坡中北部以受潮汐影响的三角洲-障壁海岸沉积体系为主,西斜坡中南部为潮坪-半封闭海湾体系;沉积环境差异决定了烃源岩类型的不同,潮坪-泻湖比三角洲具有更高的煤系发育程度和生烃能力.研究结果对西斜坡烃源岩评价和储层预测及勘探部署有较大指导作用.

Depositional Genesis Analysis of Source Rock in Pinghu Formation of Western Slope,Xihu Depression

The western slope of Xihu deprssion is the realistic choice and main field of current petroleum exploration in East China Sea basin. However, there is no consensus reached on the basic geological problems such as the formation conditions and distribution rule of source rock. Based on sedimentology, coal petrography and organic geochemistry, using the drilling data, organic geochemistry of source rock and paleontology, genetic types and formation conditions of source rock of Pinghu Formation in western slope of Xihu depression have been systematically analyzed in this study. In addition, the organic facies division method corresponding to sedimentary environment has been established, and distribution law has been summarized.It is found that the source rocks are mainly coal-bearing source rocks, and secondly marine mudstones. The north-central region of western slope mainly develops costal sedimentary system affected by tidal, while the south-central region of western slope develops tidal-flat and semi-enclosed gulf system. Different sedimentary environments determine different types of source rocks. The tidal-flat and lagoon have higher coal-bearing development degree and hydrocarbon generation capacity than delta. This research is significant for source rock evaluation, reservoir prediction and exploration deployment in western slope.