页岩气藏超压演化过程:来自四川盆地南部五峰组-龙马溪组裂缝流体包裹体的证据  

Overpressure evolution process in shale gas reservoir:Evidence from the fluid inclusions in the fractures of Wufeng Formation-Longmaxi Formation in the southern Sichuan Basin

作　　者：刘冬冬[1] 郭靖 潘占昆 杜威 赵福平 陈祎 石富伦 宋岩[1] 姜振学[1] LIU Dongdong;GUO Jing;PAN Zhankun;DU Wei;ZHAO Fuping;CHEN Yi;SHI Fulun;SONG Yan;JIANG Zhenxue(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing 102249,China;No.10 Oil Production Plant,PetroChina Changqing Oilfield Company,Qingyang,Gansu 745100,China;No.4 Gas Production Plant,PetroChina Changqing Oilfield Company,Xi'an,Shaanxi 710018,China;Guizhou Provincial Oil and Gas Exploration and Development Engineering Research Institute,Guiyang,Guizhou 550001,China)

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京市102249 [2]中国石油长庆油田公司第十采油厂 [3]中国石油长庆油田公司第四采气厂 [4]贵州省油气勘查开发工程研究院

出　　处：《天然气工业》2021年第9期12-22,共11页Natural Gas Industry

基　　金：国家科技重大专项“五峰组—龙马溪组富有机质页岩储层精细描述与页岩气成藏机理”(编号:2017ZX05035002);贵州省地勘基金项目“黔北试验区页岩气成藏控制因素研究与勘探实践”(编号:208-9912-JBN-L1D7);中国石油西南油气田公司科研项目“四川盆地龙马溪组构造演化与页岩气富集规律研究”(编号:2020-57912);“长宁西区断裂系统演化特征及其对页岩气成藏富集的影响”(编号:20210604-02)。

摘　　要：四川盆地南部(以下简称川南地区)上奥陶统五峰组—下志留统龙马溪组页岩气藏普遍存在着超压现象,部分井页岩地层压力系数远高于1.50,目前对于该区页岩气藏压力演化的过程认识尚不清楚。为了揭示该区五峰组—龙马溪组页岩气藏超压的形成机制与演化过程,以川南地区泸州、威远两地典型井页岩裂缝复合脉体样品为研究对象,通过薄片分析、阴极发光扫描电镜观察,明确裂缝复合脉体胶结物的充填期次,开展不同期次裂缝脉体矿物中包裹体测温和激光拉曼分析,结合埋藏史—地热史研究成果,揭示了不同期次裂缝的开启时间,进而探讨了其与页岩气藏超压演化过程的关系。研究结果表明:①研究区典型井页岩裂缝中主要存在着两期脉体充填,第一期脉体主要分布在裂缝壁,矿物颗粒较小,脉体中流体包裹体均一温度与主生气期温度相符,表明第一期裂缝开启过程与生烃增压作用有关,第二期裂缝脉体主要分布在裂缝中部,矿物颗粒较大,脉体中流体包裹体温度范围较广,与抬升过程地层温度相符,指示第二期裂缝开启过程与构造抬升泄压有关;②研究区页岩最大埋深前甲烷包裹体捕获压力介于103.06~139.82 MPa、压力系数介于2.05~2.50,储层抬升过程中甲烷包裹体捕获压力介于101.32~127.73 MPa、压力系数介于1.89~2.18;③页岩气藏超压来自液态烃裂解生气增压作用,抬升阶段是持续泄压的过程。结论认为,川南地区五峰组—龙马溪组页岩气藏具有良好的保存条件,现今仍能保持较高的压力系数。Overpressure is a common phenomenon in the shale gas reservoirs of Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in the southern Sichuan Basin,and the pressure coefficient of shale reservoir in some wells is even over 1.5.However,the pressure evolution process in shale gas reservoirs has not been understood clearly.In order to reveal the formation mechanism and evolution process of the overpressure in the Wufeng Formation-Longmaxi Formation shale gas reservoir of this area,this paper clarifies the filling periods of fracture composite vein cements by performing thin section analysis and cathodoluminescent scanning electron microscope(CL-SEM)observation on the samples of composite veins in the shale fractures in the typical wells in Luzhou and Weiyuan of southern Sichuan Basin.Then,thermometry and laser Raman analyses are carried out on the inclusions in fracture vein minerals of different periods,and combined with burial history and geothermal history study,the opening time of fractures of different periods is revealed.Finally,its relationship with the overpressure evolution process in shale gas reservoirs is discussed.And the following research results are obtained.First,there are mainly two stages of veins in the shale fractures in the typical wells of the study area.The fracture veins of stage one are mainly distributed on fracture walls,the particle size is small and the homogenization temperature of the fluid inclusions in the veins is accordant with the temperature of main gas generation period,which indicates that the opening process of stage-one fractures is related to the hydrocarbon-generation pressurization.The fracture veins of stage two are mainly distributed in the middle of the fractures,the particle size is larger and the temperatures range of the fluid inclusions in the veins is wider and accordant with the formation temperature in the process of uplifting,which indicates that the opening process of stage-two fractures is related to the pressure relief caused by structural u

关 键 词：四川盆地南部 页岩气藏 上奥陶统五峰组 下志留统龙马溪组 裂缝复合脉体 超压演化过程 生烃增压 流体包裹体 

分 类 号：P618.13[天文地球—矿床学]