川东南盆缘常压区页岩裂缝脉体特征及古压力演化  

Characteristics of Shale Fracture Veins and Paleo-Pressure Evolution in Normal Pressure Shale Gas Zone, Southeast Margin of Sichuan Basin

作　　者：曾宇 侯宇光[1] 胡东风 何生[1] 刘若冰 董田[1] 杨锐[1] 李欣诚 叶云飞 Zeng Yu;Hou Yuguang;Hu Dongfeng;He Sheng;Liu Ruobing;Dong Tian;Yang Rui;Li Xincheng;Ye Yunfei(Key Laboratory of Tectonics and Petroleum Resources,Ministry of Education,China University of Geosciences,Wuhan 430074,China;SINOPEC Exploration Company,Chengdu 610041,China)

机构地区：[1]中国地质大学构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国石油化工有限公司勘探分公司,四川成都610041

出　　处：《地球科学》2022年第5期1819-1833,共15页Earth Science

基　　金：国家自然科学基金企业发展联合项目(No.U19B6003-03-03);国家自然科学基金项目(Nos.41772143,42172157)。

摘　　要：为了查明川东南盆缘常压页岩气区五峰组页岩裂缝脉体记录的古温度及古压力特征,揭示常压页岩气区储层压力降低的主要影响因素和页岩气散失机理.以松坎地区五峰组黑色碳质页岩裂缝脉体内的流体包裹体为主要研究对象,通过显微镜光学观察、阴极发光测试、包裹体测温和激光拉曼分析,结合埋藏-生烃-热史模拟,对裂缝脉体中的气-液两相盐水包裹体和高密度甲烷包裹体进行了系统研究.研究表明:松坎地区五峰组裂缝中主要存在着两期脉体充填,M1裂缝脉体形成时间距今约103~86 Ma,脉体较宽、阴极发光颜色为橘红色,其内甲烷包裹体捕获压力为82.6~91.5 MPa,反映燕山中期盆缘地区页岩气藏处在超压状态;M2裂缝脉体生长于M1裂缝脉体两侧,形成时间距今约90~72 Ma,脉体较窄、阴极发光颜色为暗红色,其内甲烷包裹体捕获压力为43.6~47.3 MPa.综合分析认为,川东南盆缘松坎地区五峰组在燕山期经历了由超压至常压的转变.燕山期以来的抬升剥蚀与褶皱变形导致地层内大量页岩气沿着滑脱层发生侧向运移和散失,地层压力快速下降.燕山晚期时,盆内稳定构造区页岩气藏仍处于超压状态,而盆缘地区已降至常压.This study aims to investigate the characteristics of paleo-temperature and paleo-pressure of fluid inclusions in shale fracture veins of Wufeng Formation, and to understand the main influencing factors of the shale reservoir pressure reduction and the mechanism of shale gas loss in the normal pressure shale gas zone, southeast margin of Sichuan basin. Taking the fluid inclusions in the fracture veins of the black carbonaceous shale of the Wufeng Formation in Songkan region as the main research object, the gas-liquid saline inclusion and high-density methane inclusion with the records of paleo-temperature and paleo-pressure characteristics in fracture veins were studied systematically by the microscope optical observation, cathodoluminescence(CL)test, inclusion temperature measurement and laser Raman analysis, combined with burial-hydrocarbon generation-thermal history simulation. The results show that there are mainly two phases of vein filling in the fractures of Wufeng Formation in Songkan region. The first phase fracture veins(M1) was formed about 103-86 Ma ago, which are wide in size and with orange-red CL color. The capture pressure of methane inclusions in the fractures recorded by the M1 vein is 82.6-91.5 MPa, reflecting that the shale gas reservoir in the basin margin region was still in the overpressure state at the medium stage of Yanshanian. The secondstage fracture veins(M2) grew along both sides of the first-stage fracture veins, and the formation time was about 90-72 Ma.The M2 veins are relative narrower than M1, and with dark-red CL color. And the trapping pressure of methane inclusions in M2veins is calculated to be 43.6-47.3 MPa. Comprehensive analysis suggests that the Wufeng Formation in the Songkan region of the Southeast margin of Sichuan basin experienced a transition from overpressure to normal pressure during the Yanshanian. The uplift, denudation and fold deformation since the Yanshanian have caused a large amount of shale gas to migrate and dissipate laterally along the detachment zone

关 键 词：页岩裂缝脉体 流体包裹体 古温压恢复 松坎复向斜 油气地质 

分 类 号：P618[天文地球—矿床学]