摘要
近年来二叠系海陆过渡相页岩逐渐成为未来非常规页岩气资源的重要勘探目的层,但不同构造应力产生的页岩裂缝对于页岩气的富集或调整改造的作用机制尚未被深入研究。通过对低角度顺层滑脱裂缝脉体以及高角度剪切裂缝脉体中成岩流体和烃类流体的地球化学指标进行分析研究,阐明不同成因类型裂缝对于页岩气的影响机制。基于裂缝脉体中流体包裹体岩相学观察,显微拉曼光谱定量分析和碳酸盐岩U-Pb同位素年代学及成脉流体环境分析,认为低角度顺层滑脱裂缝脉体主要在地层埋藏—生烃阶段形成,其中主要捕获高温高压的CH_(4)—C_(2)H_(6)流体包裹体,脉体来源于热液或者成岩流体成因,以封闭还原环境为主。高角度剪切裂缝方解石脉体未发育大量烃类气包裹体,方解石脉体成因是大气淡水来源,以开放氧化环境为主,碳酸盐岩U-Pb定年结果显示喜马拉雅期构造运动的地层抬升导致高角度剪切裂缝形成。低角度顺层滑脱裂缝脉体对于页岩气的富集具有建设意义,而多数高角度剪切裂缝脉体对页岩气起到破坏和调整作用。
In recent years,the Permian terrestrial transition shale has attracted much attention due to the discovery of high-quality source rocks.The mechanism of shale fractures produced by different tectonic stresses on the enrichment or modification of shale gas has yet to be in-depth study.By analyzing the geochemical indicators of the diagenetic fluid and hydrocarbon fluid in the oblique high-angle shear fractures and bedding slippage fractures,this article clarifies the influence mechanism of different genetic types of fracture on shale gas.Based on petrography observation of the fluid inclusion in fracture veins,quantitative analysis of microscopic Raman spectroscopy,U-Pb isotope dating of carbonate rocks and analysis of vein forming fluid environment,it is concluded that the low-angle slip fracture veins are mainly formed during the burial and hydrocarbon generation stage,with CH_(4)-C_(2)H_(6) fluid inclusions under high temperature and high pressure.Fracture veins are derived from hydrothermal or diagenetic fluid,and are mainly in a closed reduction environment.A large number of hydrocarbon gas inclusions are not developed in the calcite veins with high Angle shear fractures.The calcite veins are mainly formed in an open oxidation environment due to the source of atmospheric fresh water.The U-Pb dating results of carbonate rocks show that the formation of high Angle shear fractures was caused by the uplifting of the Himalayan tectonic movement.The low-angle slip fracture vein has constructive significance for shale gas enrichment,and most of the oblique high-angle shear fracture vein plays a role of disruption and adjustment in shale gas preservation.
作者
卢宽
黄亚浩
何生
文志刚
徐耀辉
孟江辉
封栋洋
吴忠锐
LU Kuan;HUANG Yahao;HE Sheng;WEI Zhigang;XU Yaohui;MENG Jianghui;FENG Dongyang;WU Zhongrui(Hubei Key Laboratory of Petroleum Geochemistry and Environment(Yangtze University),Wuhan 430100,China;Key Laboratory of Structure and Oil and Gas Resources,Ministry of Education,China University of Geosciences(Wuhan),Wuhan 430074,China;Hubei Collaborative Innovation Center for Unconventional Oil and Gas(Yangtze University),Wuhan 430100,China)
出处
《天然气地球科学》
CAS
CSCD
北大核心
2023年第6期1090-1102,共13页
Natural Gas Geoscience
基金
中国石油开放基金项目(编号:RIPED-2022-JS-2382)资助.
关键词
流体包裹体
裂缝脉体
流体来源
下扬子二叠系乐平组
页岩气
Fluid inclusion
Fracture vein
Fluid source
Permian Leping Formation of Lower Yangtze
Shale gas
