英西地区裂缝系统在油气成藏过程中的作用

Effects of Fracture Systems During Oil and Gas Accumulation in Yingxi Area, Qaidam Basin

近年来,柴达木盆地英西地区下干柴沟组上段碳酸盐岩油气勘探取得重大突破,综合岩心观察、分析化验和测井成果,对英西地区下干柴沟组上段碳酸盐岩储集层的形成机制及裂缝在油气成藏过程中的作用进行了研究。研究认为:英西地区下干柴沟组上段碳酸盐岩储集层为一套深水细粒碳酸盐沉积,具明显混积特征;储集空间以白云石晶间孔为主,储集层裂缝系统发育,不同尺度的裂缝相互组合,构成了英西地区碳酸盐岩储集层复杂的缝网系统,对油气起到了良好的沟通和输导作用;上干柴沟组沉积初期,下干柴沟组上段烃源岩进入生油门限,并持续生烃,狮子沟组沉积末期的晚期喜马拉雅运动使柴达木盆地发生了褶皱回返,英雄岭构造逐步形成,英雄岭构造的形成过程,也是该套碳酸盐岩储集层裂缝系统的形成过程,也是油气在裂缝系统中再次分配的过程,形成了一个个相对独立的含油气系统。

A significant breakthrough has been gained in petroleum exploration of Yingxi carbonate reservoir of the lower Ganchaigou formation in Yingxi area of Qaidam basin recently.Based on the core observation,experimental analysis and logging data,the forming mechanism of Yingxi carbonate reservoir and its effects during oil and gas accumulation are researched in this paper.The research indicates that the reservoir was formed in a deep-water sedimentary environment,and the sediment is a set of fine-grained carbonates with some features of diamictite.The reservoir spaces are dominated by dolomite intercrystalline pores,the fracture systems are very developed in the reservoir.The complicated fracture systems are made up of various scales of fractures and play important roles in hydrocarbon accumulation and migration.During the deposition of the upper Ganchaigou formation,the source rocks in the upper member of the lower Ganchaigou formation entered the threshold of oil generation and continuously generated oil and gas.During the late deposition period of Shizigou formation, Himalayan movement resulted in the folding inversion and the Yingxiongling structure gradually formed.The formation process of Yingxiongling structure is not only the formation process of the fracture systems in Yingxi carbonate reservoir,but also is the process of hydrocarbon redistribution in the fracture systems,during which a lot of separate petroleum systems formed.