陆相页岩储层连通孔隙系统分布与形成机制——以川西坳陷上三叠统须家河组为例  

Distribution and genetic mechanisms of connected pore systems in continental shale reservoirs:a case study of Xujiahe Formation of Upper Triassic, Western Sichuan Depression

作　　者：赵明珠 杨威[1,2] 王耀华 鲁健康 徐亮 李兰 李兴宇[1,2] 姚琳洁 ZHAO Mingzhu;YANG Wei;WANG Yaohua;LU Jiankang;XU Liang;LI Lan;LI Xingyu;YAO Linjie(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;Unconventional Oil and Gas Science and Technology Institute,China University of Petroleum(Beijing),Beijing 102249,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,北京102249 [2]中国石油大学(北京)非常规油气科学技术研究院,北京102249

出　　处：《石油实验地质》2022年第1期170-179,198,共11页Petroleum Geology & Experiment

基　　金：国家科技重大专项(2016ZX05034001-005,2017ZX05035002-007);中国石油大学(北京)优秀青年学者科研启动基金项目(2462020QNXZ004);中国石油天然气集团有限公司—中国石油大学(北京)战略合作科技专项(ZLZX2020-01-06)联合资助。

摘　　要：为揭示陆相页岩储层连通孔隙系统的形成机制,指导页岩气高效开发,以川西坳陷上三叠统须家河组陆相页岩为例,综合运用X衍射、场发射扫描电镜、低温气体吸附、高压压汞和核磁共振冻融等分析测试方法,研究了样品的矿物组分、全孔径分布特征和孔隙连通特征,并分析了孔隙连通性的主控因素。川西坳陷研究区上三叠统须家河组陆相页岩黏土矿物含量最高,石英含量次之;页岩孔径分布复杂,其中中孔最为发育,是孔体积(占87.33%)和比表面积(占49.19%)的主要贡献者;20~50 nm孔隙连通性较好,是研究区须家河组主要的连通孔隙发育区间;须家河组陆相页岩主要发育黏土矿物晶间孔,粒内溶孔较少,基本不发育有机质孔,广泛发育微裂缝,其中黏土矿物晶间孔—微裂缝孔隙组合是研究区主要的连通孔隙类型;黏土矿物及石英等脆性矿物的含量及排列方式控制连通孔隙的发育及分布。基于以上结果总结了陆相页岩连通孔隙的3种潜在发育机制:发育在黏土矿物与脆性矿物基质上的黏土矿物晶间孔—微裂缝组合连通性最好;黏土矿物集合体内的黏土矿物晶间孔连通性次之;有机—黏土复合体内的有机孔—黏土矿物晶间孔连通性最差。The distribution and genetic mechanisms of connected pore systems in continental shale reservoirs were analyzed in this paper to enhance the high-efficiency exploration of shale gas. A case study was made with the continental shale of the Upper Triassic Xujiahe Formation in the Western Sichuan Depression. Various experimental methods such as X-ray diffraction, field emission-scanning electron microscopy, low temperature gas adsorption, high-pressure mercury injection and nuclear magnetic resonance cryoporometry were applied to study its mineral composition, distribution of pore-size and pore connectivity, and the main constrains for pore connectivity were discussed. The continental shale of the Xujiahe Formation in the study area has a high content of clay minerals, followed by quartz. The pore-size distribution is complex, and the mesopores in the range of 4-50 nm is the main contributor to pore volume(87.33%) and specific surface area(49.19%). The pores having the size between 20-50 nm appeared to have better pore connectivity and are the major type of connected pores. The continental shale developed various types of pore, predominantly composed of clay intercrystalline pores, with minor dissolved pores and organic pores. Microfractures were widely developed and formed the dominant connective pore assemblage together with clay intercrystalline pores. The development and distribution of connected pores were controlled by the contents and arrangement of brittle minerals such as clay minerals and quartz. Based on the experimental results, some development mechanisms of connected pores in continental shale were concluded. The combination of intercrystalline pores and microfractures developed on the matrix of clay minerals and brittle minerals shows the best connectivity, followed by the clay intercrystalline pores in clay minerals, while the organic pores and clay intercrystalline pores in organic-clay complexes show the lowest connectivity.

关 键 词：陆相页岩 孔隙连通性 黏土矿物晶间孔 核磁共振冻融 须家河组 上三叠统 川西坳陷 

分 类 号：TE122.2[石油与天然气工程—油气勘探]