川东南永川地区龙马溪组页岩储层构造裂缝特征及期次演化研究  

Study on tectonic fracture characteristics and stage evolution of Longmaxi shale reservoir in Yongchuan,southeastern Sichuan Basin

作　　者：何建华 李勇[1] 邓虎成[1,2] 王园园 马若龙 唐建明[4] HE Jianhua;LI Yong;DENG Hucheng;WANG Yuanyuan;MA Ruolong;TANG Jianming(College of Energy,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;Hainan Branch of China National Offshore Oil Corporation Ltd.,Haikou 570100,China;Exploration and Development Research Institute,Sinopec Southwest Oil&Gas Company,Chengdu 610059,China)

机构地区：[1]成都理工大学能源学院,四川成都610059 [2]成都理工大学油气藏地质及开发工程全国重点实验室,四川成都610059 [3]中海石油(中国)有限公司海南分公司,海南海口570100 [4]中国石化西南油气分公司勘探开发研究院,四川成都610059

出　　处：《地学前缘》2024年第3期298-311,共14页Earth Science Frontiers

基　　金：国家自然科学基金面上项目(42072182);四川省杰出青年人才项目(2020JDJQ0058);四川省科技厅重点苗子项目(22MZGC0159)。

摘　　要：天然裂缝发育特征和形成期次对川东南复杂构造区页岩气成藏具有重要意义,且对页岩储层压裂改造效果及高产的控制作用明显。目前对川东南远离盆缘的深层页岩气区块内不同力学成因天然裂缝的特征及形成演化尚缺乏系统研究,制约了盆内深层页岩气的高效勘探开发。基于野外露头、钻井岩心、薄片、地球化学测试及磷灰石定年等资料对永川地区龙马溪组页岩储层构造裂缝特征及形成期次开展了研究。结果表明,龙马溪组页岩主要发育构造成因的中高角度剪切缝,低角度顺层滑脱裂缝和垂直张性缝,此外岩心上可见有非构造成因的层理缝、生烃超压缝以及位于主干断裂部位的热液溶蚀缝。纵向上受矿物组成影响裂缝发育程度由深至浅逐渐降低,平面上受构造影响,在背斜核部或翼部陡坡区裂缝密集发育高角度、组系优势明显且纵向贯穿程度大的裂缝,而平缓区发育低角度、小尺度且组系杂乱的裂缝。研究区裂缝先后经历了燕山晚期—喜马拉雅早期(86~47 Ma)、喜马拉雅中期(47~24 Ma)、喜马拉雅晚期至现今(24 Ma至现今)3期构造运动而形成,不同演化阶段的裂缝发育和充填特征差异明显。第一期,构造裂缝主要为NWW-NNW向共轭剪切裂缝,裂缝多被纤维状方解石和少量石英脉体充填,均一温度介于220~250℃;第二期构造裂缝为NW-NNW向共轭剪切裂缝,同时背斜区形成NE向垂直张性裂缝与高角度剖面剪切缝,裂缝被拉长块状方解石或石英脉体充填,均一温度介于180~210℃;第三期构造裂缝为单独的NE-NEE向压扭性裂缝,同时改造前期形成的裂缝主要被块状方解石、石英脉体充填,均一温度介于140~180℃,这一时期地层抬升导致温度下降明显,裂缝充填性变弱,形成的裂缝不利于页岩气保存。与裂缝形成的地质力学环境进行匹配,构建了永川地区页岩储层3期构造裂缝发育演化模式�Development characteristics and formation stages of natural fractures are of great significance to shale gas accumulation in the complex structural area of southeastern Sichuan.It also significantly influences the effects of hydrofracturing reconstruction and high gas production of shale reservoirs.Currently,there is no systematic study on the characteristics and evolutions of natural fractures with various origins in deep shale gas blocks far from the basin margin in the southeastern Sichuan Basin,which hinders the efficient exploration and development of deep shale gas reservoirs in the basin.Based on field outcrops,drilling cores,thin sections,geochemical data,and apatite dating,the characteristics and formation stages of natural fractures in the Longmaxi Formation shale reservoirs in the Yongchuan area have been studied.The results indicate that the Longmaxi Formation shale mainly developed tectonic fractures,including shear fractures with medium to high angles,low angle slip fractures,and vertical tensile fractures.Additionally,bedding fractures and overpressure fractures are also observed in the cores,with hydrothermal dissolution fractures mainly developed near the main fault zones.Vertically,the density of fracture development gradually decreases from deep to shallow due to variations in mineral compositions.Horizontally,fractures with high angles,distinct single fracture groups,and high vertical penetration capacity are densely developed in the anticline core or wing steep slope area,while fractures with low angles,small scales,and various fracture groups are developed in the gentle areas.Three tectonic movements—the late Yanshan(8647 Ma),early to middle Himalayan(4724 Ma),and late Himalayan to present(240 Ma)—contributed to the tectonic fractures in this area.The fracture development and filling characteristics in different evolutionary stages are notably different.The study establishes a tectonic fracture development and evolution model of shale in three phases in the Yongchuan area,providing valua

关 键 词：裂缝特征 期次演化 五峰组—龙马溪组页岩 永川地区 川东南 

分 类 号：TE121.2[石油与天然气工程—油气勘探] P542.3[天文地球—构造地质学]