川东北元坝地区侏罗系陆相页岩天然裂缝发育特征及其对页岩油气富集和保存的影响OA北大核心CSTPCD

Development of natural fractures is one of key factors affecting the enrichment and preservation of shale oil and gas with in the continental shale at the Yuanba area,northeast Sichuan Basin.This study investi-gated the distribution of the natural fractures in the Jurassic Da'anzhai shale and Qianfoya shale based on the core data,thin section,and scanning electron microscopic images.We further discussed the influence of frac-tures on the shale oil and gas enrichment and preservation.The results show that there are mainly tectonic frac-tures,lamellation fractures,cross-layer hydraulic fractures,and shrinkage fractures.The tectonic fractures in-clude cross-layer shear fractures,layer-parallel shear fractures,and intra-layer aperture fractures.The lamel-lation fractures are the dominant natural fractures and the linear density is between 66 and 357 per meter with an average of 188 per meter.We concluded that the lamellation and shrinkage fractures are the storage space of shale oil and gas,as well as the migration channels to improve the reservoir and benefit the enrichment of shale oil and gas.The macroscopic fracture networks formed by tectonic fractures,cross-layer hydraulic fractures,and lamellation fractures are the channels for shale oil and gas emission,which has a great influence on the dis-sipation of shale gas in Da'anzhai Member,but has little influence on shale oil preservation in Qianfoya Forma-tion.These results provide a fundamental reference for the exploration and development of continental shale oil and gas in the Sichuan Basin.