摘要
四川盆地及周缘筇竹寺组、五峰组-龙马溪组2套页岩是目前中国海相页岩气勘探的主攻层位,但页岩气勘探效果差异较大。为进一步探究这2套海相页岩储层的微观孔隙结构特征及其差异,采用定性和定量相结合的方法(包括场发射扫描电子显微镜、低压CO_(2)/N_(2)吸附、多重分形分析)对研究区筇竹寺组、五峰组-龙马溪组页岩的孔隙结构进行精细表征和对比,并揭示两者的成因机制差异。结果表明,研究区筇竹寺组、五峰组-龙马溪组页岩孔隙结构在孔隙发育程度及类型、孔径分布以及微孔、介孔-宏孔连通性、非均质性等方面存在明显差异。相较于筇竹寺组,五峰组-龙马溪组页岩具有有机质孔隙更为发育、孔隙度高、孔隙连通性较低、非均质性更强、微孔占比高以及孔隙比表面积和孔体积高等特征。导致筇竹寺组、五峰组-龙马溪组页岩孔隙结构差异的原因包括:①沉积环境差异导致两者页岩岩相不同,进而影响原始孔隙的有效保存;②机械压实作用、有机质热成熟作用、热成熟阶段页岩系统的封闭性以及深埋藏阶段强烈的机械压实作用是造成2套页岩孔隙结构差异的关键成岩作用。五峰组-龙马溪组由于其高的生物硅质含量、适中的热演化程度、相对封闭的页岩系统、相对较浅的埋藏作用和相对稳定的构造条件更有利于页岩中残余无机孔隙及有机质孔隙的发育和有效保存。
Shales in the Qiongzhusi Formation and Wufeng-Longmaxi Formation in the Sichuan Basin and surrounding areas are a major target for the exploration of marine shale gas in China,but their analyses have yielded significantly varying results thus far.To comprehensively investigate the characteristics of the pore structure and differential mechanisms of these two marine shale reservoirs,this study combines qualitative and quantitative methods(including field-emission scanning electron microscopy,low-pressure CO_(2)/N_(2)adsorption,and multiple analyses)to accurately characterize and compare the pore structures of shales in the Qiongzhusi Formation and Wufeng-Longmaxi Formation,with the aim of revealing the differences in their mechanisms of formation.The results revealed significant variations in pore structure between shales of the Qiongzhusi Formation and Wufeng-Longmaxi Formation,including in the development,style,size distribution,and connectivity of micro-and meso-macro-pores as well as their heterogeneity.Shale in the Wufeng-Longmaxi Formation contained pores with a higher organic matter(OM)content,higher porosity,lower connectivity,greater heterogeneity,higher ratio of micropores,and a larger surface specific area and pore volume than the Qiongzhusi Formation shale.The differences in their pore structures can be attributed to the following distinct genetic mechanisms of the two shale reservoirs:(1)variations in the depositional environment,leading to differences in mineral composition that influenced primary porosity preservation;and(2)key diagenetic processes,including mechanical compaction,thermal maturation of OM,sealing conditions during thermal maturation,and intense burial-induced compaction,that led to disparities in the pore structure.The presence of biogenetic quartz,moderate thermal maturity of OM,sealed shale gas systems,shallow depth of burial,and relatively stable tectonic conditions were found to be conducive to the formation and preservation of residual inorganic and OM pores in the shales.
作者
谢国梁
焦堃
刘瑞崟
邓宾
叶玥豪
刘树根
XIE Guoliang;JIAO Kun;LIU Ruiyin;DENG Bin;YE Yuehao;LIU Shugen(School of Civil Engineering&Architecture,Tongling University,Tongling 244061,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploration(Chengdu University of Technology),Chengdu 610059,China;Guizhou Engineering Research Institute of Oil&Gas Exploration and Development,Guiyang 550004,China;Key Laboratory of Unconventional Natural Gas Evaluation and Development in Complex Tectonic Areas,Ministry of Natural Resources,Guiyang 550004,China;Xihua University,Chengdu 610039,China)
出处
《成都理工大学学报（自然科学版）》
CAS
CSCD
北大核心
2024年第5期813-832,共20页
Journal of Chengdu University of Technology: Science & Technology Edition
基金
国家自然科学基金项目(42372174,42207293)
安徽省自然科学基金项目(2208085QD110)
四川省自然科学基金面上项目(2023NSFSC0262)
安徽省高校自然重点项目(2022AH051748)
铜陵学院自然科学重点项目(2021tlxyZD03)
铜陵学院人才科研启动基金项目(2021tlxyrc16)。
关键词
孔隙结构
成因差异机制
五峰组-龙马溪组
筇竹寺组
四川盆地及周缘
pore structure
differences in genetic mechanism
Wufeng-Longmaxi Formation
Qiongzhusi Formation
Sichuan Basin and surrounding areas
