Li Jing, Li Hu, Jiang Wei, Cai Molun, He Jia, Wang Qiang, Li Dingyuan
Institute of Geological Exploration and Development of CNPC Chuanqing Drilling Engineering Company Limited, Chengdu, 610051, China.
School of Economics, Sichuan University of Science and Engineering, Yibin, 644000, China.
Sci Rep. 2024 Jul 23;14(1):16896. doi: 10.1038/s41598-024-66759-7.
Deep shale has the characteristics of large burial depth, rapid changes in reservoir properties, complex pore types and structures, and unstable production. The whole-rock X-ray diffraction (XRD) analysis, reservoir physical property parameter testing, scanning electron microscopy (SEM) analysis, high-pressure mercury intrusion testing, CO adsorption experimentation, and low-temperature nitrogen adsorption-desorption testing were performed to study the pore structure characteristics of marine shale reservoirs in the southern Sichuan Basin. The results show that the deep shale of the Wufeng Formation Longyi sub-member in the Luzhou area is superior to that of the Weiyuan area in terms of factors controlling shale gas enrichment, such as organic matter abundance, physical properties, gas-bearing properties, and shale reservoir thickness. SEM is utilized to identify six types of pores (mainly organic matter pores). The porosities of the pyrobitumen pores reach 21.04-31.65%, while the porosities of the solid kerogen pores, siliceous mineral dissolution pores, and carbonate dissolution pores are low at 0.48-1.80%. The pores of shale reservoirs are mainly micropores and mesopores, with a small amount of macropores. The total pore volume ranges from 22.0 to 36.40 μL/g, with an average of 27.46 μL/g, the total pore specific surface area ranges from 34.27 to 50.39 m/g, with an average of 41.12 m/g. The pore volume and specific surface area of deep shale gas are positively correlated with TOC content, siliceous minerals, and clay minerals. The key period for shale gas enrichment, which matches the evolution process of shale hydrocarbon generation, reservoir capacity, and direct and indirect cap rocks, is from the Middle to Late Triassic to the present. Areas with late structural uplift, small uplift amplitude, and high formation pressure coefficient characteristics favor preserving shale gas with high gas content and production levels.
深层页岩具有埋藏深度大、储层性质变化快、孔隙类型和结构复杂以及产量不稳定等特点。开展了全岩X射线衍射（XRD）分析、储层物性参数测试、扫描电子显微镜（SEM）分析、高压压汞测试、CO吸附实验以及低温氮吸附-脱附测试，以研究四川盆地南部海相页岩储层的孔隙结构特征。结果表明，泸州地区五峰组龙一段深层页岩在控制页岩气富集的因素方面，如有机质丰度、物性、含气性和页岩储层厚度等，优于威远地区。利用扫描电子显微镜识别出六种孔隙类型（主要为有机质孔隙）。热沥青孔隙的孔隙度达到21.04 - 31.65%，而固体干酪根孔隙、硅质矿物溶蚀孔隙和碳酸盐溶蚀孔隙的孔隙度较低，为0.48 - 1.80%。页岩储层的孔隙主要为微孔和中孔，大孔较少。总孔隙体积范围为22.0至36.40 μL/g，平均为27.46 μL/g，总孔隙比表面积范围为34.27至50.39 m/g，平均为41.12 m/g。深层页岩气的孔隙体积和比表面积与TOC含量、硅质矿物和黏土矿物呈正相关。页岩气富集的关键时期与页岩生烃、储集能力以及直接和间接盖层的演化过程相匹配，为中三叠世晚期至今。构造抬升较晚、抬升幅度小且地层压力系数高的地区有利于保存高含气量和高产气量的页岩气。
