黔中隆起及其周缘地区“下组合”油气地质特征

Petroleum Geological Conditions of Lower Assemblage in Qianzhong Uplift and Peripheral Regions

黔中隆起及其周缘地区包括滇黔北部坳陷、黔中隆起、滇东隆起、黔西南坳陷、黔南坳陷和武陵坳陷等六个一级构造单元。“下组合”包括震旦系、寒武系、奥陶系和志留系,具有丰富的油气资源和较好的油气成藏条件。两套区域性海相烃源岩,包括下寒武统牛蹄塘组碳质页岩和上奥陶统五峰组—下志留统龙马溪组石灰岩和碳质页岩,Ro值普遍在2%以上,主体处于高成熟晚期—过成熟早期。上震旦统陡山沱组发育地区性黑色页岩和碳质灰岩等烃源岩。主力储层包括上震旦统灯影组、中—上寒武统、下奥陶统桐梓组—红花园组及下志留统石牛栏组。区域盖层发育于下寒武统下部和下志留统下部,皆以泥质岩为主。各区块海相“下组合”纵向生储盖组合发育情况有所差异,黔中隆起区和黔南坳陷有两套组合,滇黔北部坳陷则有四套组合。以下寒武统牛蹄塘组为烃源岩、上震旦统灯影组白云岩为储层、下寒武统泥岩为盖层的生储盖组合,是黔中隆起及其周缘地区“下组合”勘探的主要目的层系。

There is a play, named Lower Assemblage, in Qianzhong Uplift and its peripheral regions. The Lower Assemblage comprised regional marine Sinian-Silurian sedimentary system with rich hydrocarbon and good hydrocarbon accumulation conditions. Two sets of late high-mature to early overmature （generally Ro〉2.0%） regional source rock are Niutitang （ε1） marine carbonaceous shale and Wufeng（O3）-Longmaxi（S1） limestone and carbonaceous shale. Another local source rock is Doushantuo（Z2） maine balck shale and carbonaceous carbonate rock. Reservoirs mainly arc Upper Sinian Denying dolostone, Upper and Middle Cambrian dolostone and dolomitic limestone, Lower Ordovician Tongzi-honghuayuan limestone and dolostone, and Lower Silurian Shiniulan shale and limestone. Regional cap rocks are lower Lower Cambrian and lower Lower Silurian shaly rocks. The Lower Assemblage reveals different assemblages in different structure regions. For example, there are two assemblages in Qianzhong Uplift and Qiannan Depression but four assemblages in Dianqian Beibu Depression. It is suggested that the recent exploration target should be the lower assemblage consisting of Niutitang（source）-Denying（reservoir）-Lower Cambrian（cap） rocks.