中国低丰度大型岩性油气田形成条件和分布规律

Formation Conditions and Distribution Rules of Large Lithologic Oil-Gas Fields with Low Abundance in China

我国低丰度岩性油气田具有很大的资源潜力和储量规模,在中、古生代地层均有广泛的分布,具备良好的油气地质背景和成藏条件,是未来油气勘探的重点领域,其形成条件及富集规律不明.本文在大量统计分析和地质研究的基础上,探讨了低丰度大油气田的形成条件、分布特征、富集规律和未来的勘探领域.研究指出了低丰度大型岩性油气田形成的几个地质背景:大面积高丰度烃源岩;平缓的构造格局;稳定的沉积背景;大规模的沉积体系;建设性成岩环境.系统分析了油气田形成控制因素和分布规律:1陆相(或海陆交互相)大型三角洲平原—前缘主河道砂体、海相高能相带(台缘礁滩、滨岸砂体)是大型岩性油气藏的有利分布区;2次生溶蚀相、白云岩化相、风化淋滤相、绿泥石薄膜胶结相和TSR相等建设性成岩作用是优质储层及大油气田分布的有利区;3古地形(古隆起、斜坡、起伏带、鼻隆等)、断裂(层/褶/坡/陷/块)带、构造反转带、裂缝发育带和地层剥蚀尖灭带是大型油气田形成的有利构造条件和富集地区;4低丰度大型岩性油气田的分布和富集普遍受控于构造、沉积和成岩三因素控制的“甜点”.研究成果可为寻找油气勘探的后备领域和储量接替提供理论基础和科学依据.

Lithologic oil-gas fields with low abundance in China have enormous resource potential and reserves scale which are widely distributed in Mesozoic Paleozoic stratum and possess favorable geological background for the formation of oil-gas reservoir. Large lithologic oil-gas fields with low abundance are important future exploration field in China, and their formation conditions and distribution rules are noncommittal. Based on a mass of statistical analysis and geological study, are probed into formation conditions, distribution characteristics, enrichment rules and future exploration fields of large lithologic oil-gas fields. Several geological conditions are pointed out about large lithologic oil-gas fields with low abundance, i.e. hydrocarbon source rock with large area and high abundance, flat structure pattern, steady sedimentary background, large scale sedimentary system and constructive diagenesis environment, In this paper are systematically analyzed the controlling factors of formation and distribution rules of large lithologic oil-gas fields from four aspects. The first is that the main riverway sandbody in large continental deltaic plain-front, the high energy facies belt of marine facies such as reef-flat in platform edge, onshore sandbody are favorable distribution region of large lithologic oil-gas fields; The second is the constructive diagenesis are high quality reservoir and favorable distribution region of large oil-gas fields such as secondary corrosion facies, dolomite lithification facies, weathering leaching facies , chlorite thin film cementation facies and TSR facies; The third is the ancient terrain（ ancient uplift , slope, up-and-down belt, uplift of the nose belt）, rift/fault/break-slope belt, tectonic reversal belt, crack belt and stratum denudation pinch belt are favorable structure conditions and enrichment area of large oil gas fields formation; The fourth is the distributions and enrichment of large lithologic oil-gas fields with low abundance are generally controlled by ＂Sweet Point＂ that is controlled by three facors, namely structure, sedimentary and diagenesis. Research result provide theoretic foundation and scientific foundation for the preparative fields and reserves supersedence of oil-gas exploration.