鄂尔多斯盆地下寺湾地区长7致密油地质特征及成藏主控因素

Geological characteristics and main controlling factors of hydrocarbon accumulation in Chang 7 tight oil of Yanchang Formation of Xiasiwan area, Ordos Basin

基于大量钻井、测井、录井及试油资料,结合岩心观察和薄片鉴定,通过综合研究下寺湾地区长7段致密油储集层与烃源岩的展布、岩石学、地球化学等资料,对下寺湾地区长7致密油地质特征、富集规律及主控因素进行研究。研究结果表明:下寺湾地区长7致密油资源丰富,主要赋存于与湖相泥页岩共生或紧邻的大面积分布的重力流成因的致密砂岩储层中,石油未经过长距离运移。长7段致密油具有砂体大面积叠合规模大、储集层致密、孔喉结构复杂、裂缝发育、含油性和原油物性较好、低压低产等特征。长7优质烃源岩与大面积分布的厚层储集砂体互层共生,呈连续型分布,地史期生烃增压强排烃作用控制了延长组大面积叠合致密油的形成。下寺湾地区致密油资源潜力大,具有广阔的勘探前景。

Based on the analysis of massive data about well drilling, well logging, geological log, production test, combined with the core observation and thin section analysis, through comprehensive study of reservoir and source rock distribution, petrology and geochemistry, the geological characteristics, hydrocarbon distribution laws and main controlling factors of Chang 7 tight oil in Xiasiwan area of Ordos Basin were studied. The results show that Chang 7 in Xiasiwan area contains abundant tight oil resources, and they accumulate in source rocks in tight sandstones or adjacent to source rocks. Generally, this oil accumulation has not yet experienced a large-scale, long-distance migration. Tight oil in Xiasiwan area is characterized by a wide distribution, superior conditions of source rocks, tight sandstone reservoirs, complex pore-throat structure, abundant fractures and oil saturation, better crude property, low fluid pressure coefficient and low oil yield. The formation of large-scale superimposed tight oil reservoirs is controlled by the interbeded lithologic combination of extensive source rocks and reservoirs and the strong hydrocarbon generation and expulsion during geological history. This type of pool is an important potential resource, revealing the huge potential and good exploration prospect.