塔里木盆地与威利斯顿盆地古生界海相碳酸盐岩油气成藏特征对比

摘要

The Paleozoic marine carbonates are the main exploration targets in both Tarim and Williston basins .Based on a comparative analysis of both tectonic-depositional setting and conditions for the formation of hydrocarbon accumula-tions,this paper discusses the similarities and differences of hydrocarbon accumulation in the Paleozoic marine carbonates of the two basins .Williston Basin locates within the large North America Plate with relatively stable tectonic setting .The sedimentation within the basin was mainly controlled by eustasy .In contrast ,Tarim Basin locates in the much smaller Tar-im Plate and experienced frequent and intensive structural deformations .As a result,the sedimentation within the basin was mainly controlled by the tectonic movements .Williston Basin has high-TOC effective source rocks ,good porous-type reservoirs and evaporite cap rocks ,while Tarim Basin has high-mature to overmature source rocks ,karst and dolomite res-ervoirs,and mudstone and evaporite cap rocks .Different kinds of traps are developed on the paleo-highs in both basins , which constitute the main carbonate play fairways .Williston Basin has multiple evaporite sequences ,which makes it pos-sible to effectively apply the petroleum system concept to the basin .In comparison ,the hydrocarbon accumulation system concept can provide effective guidance for the hydrocarbon exploration in basins such as Tarim Basin featuring in multiple source rocks ,multiple kitchens and multiple episodes of hydrocarbon charging .The favorable reservoir-seal assemblage in Williston Basin is dolomite reservoir and evaporite seal .The comparative analyses indicate that the favorable carbonate play fairways are the areas with the assemblage of the Lower-Middle Cambrian dolomite reservoirs and the Middle Cam-brian evaporite seals in the Bachu and Tazhong areas .%塔里木盆地和威利斯顿盆地均以古生界海相碳酸盐岩为主要勘探层系。基于对构造沉积背景和油气成藏条件的对比分析，探讨了两个盆地古生界海相碳酸盐岩油气成藏的异同。威利斯顿盆地所处的北美板块规模较大，构造相对稳定，沉积主要受海平面升降的控制。塔里木盆地所处的塔里木板块规模较小，构造变动强烈，沉积受构造运动影响较大。威利斯顿盆地发育了高丰度的烃源岩、良好的孔隙型储层和蒸发岩盖层。而塔里木盆地古生界发育高-过成熟度烃源岩、岩溶型和白云岩储层及泥岩和蒸发岩主导的盖层。二者均发育有多种类型圈闭的古隆起，可作为盆地油气富集的主要区带。威利斯顿盆地发育的多套蒸发岩盖层使得含油气系统概念在该盆地能够得到有效的应用，而油气成藏体系则可以更有效地指导以塔里木盆地为代表的多源、多灶和多成藏期盆地的油气勘探。白云岩-蒸发岩构成了威利斯顿盆地重要的储-盖组合类型。以此类比，塔里木盆地巴楚和塔中地区的中、下寒武统白云岩-中寒武统膏盐岩储-盖组合是未来勘探的有利目标区。