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  

Characteristics of Natural Fractures and Their Influence on Oil and Gas Enrichment and Preservation of the Jurassic Continental Shale in the Yuanba Area,Northeastern Sichuan Basin

作　　者：蒋代琴 李平平[1] 邹华耀[1] JIANG Daiqin;LI Pingping;ZOU Huayao(College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249

出　　处：《现代地质》2024年第2期362-372,共11页Geoscience

基　　金：中国科学院战略性先导科技专项(A类)“四川盆地重点地区深层油气运移机理与富集规律”(XDA14010306)。

摘　　要：川东北元坝地区陆相页岩中天然裂缝发育,是影响页岩油气富集和保存的关键因素。本文依据岩心、镜下薄片和扫描电镜等资料研究该区侏罗系大安寨段和千佛崖组页岩层系天然裂缝的发育分布特征,探讨裂缝对页岩油气富集和保存的影响。结果表明,侏罗系页岩中主要发育构造裂缝、层理缝、穿层水力破裂缝和收缩缝,其中构造裂缝包括穿层剪切缝、顺层剪切缝和层内张开缝,层理缝是页岩中最为发育的天然裂缝,线密度介于66~357条/m之间,平均为188条/m。层理缝和收缩缝既是页岩油气的储集空间也是运移通道,改善了页岩的储集性能,有利于页岩油气的富集。构造裂缝、穿层水力破裂缝与层理缝相互连通形成的宏观裂缝网络是页岩油气排放的通道,对大安寨段页岩气的逸散影响较大,对千佛崖组页岩油的保存条件影响较小。研究成果可为四川盆地陆相页岩油气勘探开发提供基础性参考依据。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 investigated 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 fractures on the shale oil and gas enrichment and preservation.The results show that there are mainly tectonic fractures,lamellation fractures,cross-layer hydraulic fractures,and shrinkage fractures.The tectonic fractures include cross-layer shear fractures,layer-parallel shear fractures,and intra-layer aperture fractures.The lamellation 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 dissipation of shale gas in Da'anzhai Member,but has little influence on shale oil preservation in Qianfoya Formation.These results provide a fundamental reference for the exploration and development of continental shale oil and gas in the Sichuan Basin.

关 键 词：天然裂缝 页岩油气 富集和保存 侏罗系 元坝地区 川东北 

分 类 号：P588.22[天文地球—岩石学] P618.13[天文地球—地质学]