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歧口凹陷西南缘古近系沙河街组一段下部(沙一下亚段:Es1下)广泛发育白云岩类油气藏。经过油源对比发现,油气藏原油主要来自沙一下烃源岩,其特点是成熟度较低,且油气近源充注。在此基础上,对沙一下白云岩类油气藏成藏条件的分析发现,油源条件、储层岩性及厚度、以及储层裂缝的发育是油气成藏的主控因素。良好的油源条件是油气富集高产的基础、而储层岩性是油气富集高产的根本、储层厚度是油气富集高产的保障、而储层内部裂缝的发育是油气富集高产的关键。文章总结了歧口凹陷油气藏发育类型,共发育两种白云岩类油气藏成藏模式,并具有自生自储、下生上储、叠加连片成藏等特点。
The dolomite reservoirs are widely developed in the lower part of the first member of the Shahejie Formation of the Paleogene in the southwestern margin of the Qikou Depression (sub-subscript Sha: Es1). After comparison of oil sources, it is found that the crude oil in the oil and gas reservoirs mainly comes from the source rocks in the sand, which is characterized by low maturity and near-source filling of oil and gas. Based on the above analysis, it is found that the conditions of oil source, the lithology and thickness of reservoirs, and the development of reservoir fractures are the main controlling factors for hydrocarbon accumulation. Good oil source conditions are the basis for oil and gas enrichment and high yield, and reservoir lithology is the basis for oil and gas enrichment and high yield. Reservoir thickness is the guarantee for oil and gas enrichment and high yield. The development of internal fractures in reservoirs is oil and gas-rich high-yield The essential. This paper summarizes the types of oil and gas reservoirs in the Qikou Depression, and developed two types of hydrocarbon accumulation models of dolomite reservoirs, with the characteristics of self-generative self-storage, subsurface upper storage and superimposed contiguous hydrocarbon accumulation.