超临界CO_(2)作用下页岩微观孔隙结构与多尺度分形特征--以鄂尔多斯盆地延长组73亚段为例  

Research on the micro-pore structure and multiscale fractal characteristics of shale under supercritical CO_(2) action:A case study of the Chang 73 sub-member in the Ordos Basin

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作  者:蒋丽丽 田冷[1,2] 陈掌星[3,4] 王泽川[1,2] 黄文奎 柴晓龙 JIANG Lili;TIAN Leng;CHEN Zhangxing;WANG Zechuan;HUANG Wenkui;CHAI Xiaolong(College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing 102249,China;Engineering Research Center of Gas Energy Development and Utilization,Ministry of Education,China University of Petroleum(Beijing),Beijing 102249,China;University of Calgary,Calgary T2N 1N4,Canada;Ningbo Eastern University of Technology,Ningbo 315200,China)

机构地区:[1]中国石油大学(北京)石油工程学院,北京102249 [2]中国石油大学(北京)气体能源开发与利用教育部工程研究中心,北京102249 [3]卡尔加里大学,加拿大卡尔加里T2N 1N4 [4]宁波东方理工大学,浙江宁波315200

出  处:《天然气地球科学》2025年第3期533-553,共21页Natural Gas Geoscience

基  金:国家自然科学基金项目“基于超声波作用促进低渗透油藏CO_(2)驱动态混相机理研究”(编号:51974329);国家自然科学基金国际合作基金项目“CCUS二氧化碳驱油与埋存技术”(编号:G2021122005L)联合资助。

摘  要:为明确超临界CO(2 ScCO_(2))对页岩微观孔隙结构的影响机制,以鄂尔多斯盆地延长组73亚段(长73亚段)页岩为研究对象,在有机地球化学和矿物组成分析的基础上,采用低温气体(CO_(2)、N2)吸附实验和核磁共振(NMR)扫描方法,结合多尺度分形理论,全面分析了页岩微观孔隙结构的变化规律及多尺度分形特征,详细阐明了ScCO_(2)对页岩孔隙结构的微观作用机制。研究结果表明,ScCO_(2)作用后,页岩样品的总有机质(TOC)含量下降,石英含量增加,而黏土矿物和长石含量减少。相比于温度变化,TOC及矿物组分对压力变化的敏感性更高。此外,页岩孔隙主要分布在对比表面积贡献较大的微孔(0~2 nm)和中孔(2~50 nm)范围内,大孔(>50 nm)的数量较少,但其对总孔体积的贡献显著。ScCO_(2)作用后,页岩样品的总比表面积减少,而总孔体积、平均孔径和有效孔隙度均增大。其中,总比表面积和平均孔径对温度变化较为敏感,而总孔体积和有效孔隙度则受压力影响显著。同时,页岩孔隙表现出多尺度分形特征:微孔具有较高的分形维数,而中、大孔的分形维数较低。ScCO_(2)作用后,各尺度分形维数均呈下降趋势,表明页岩样品孔隙结构的复杂性得到改善。微孔分形维数与TOC含量呈显著正相关,而中大孔分形维数与石英、黏土矿物含量的相关性更强。由此可知,页岩矿化特性的变化是影响微观孔隙结构的内在因素,ScCO_(2)作用条件则是重要的外在因素,两者共同作用决定了页岩孔隙结构的演变过程。研究成果为碳捕集、利用与封存的优选层段提供了重要的科学依据和实际指导。To elucidate the mechanism of supercritical CO_(2)(ScCO_(2))on the micro-porous structure of shale,this study focuses on the Chang 73 sub-member of the Yanchang Formation in the Ordos Basin.Based on organic geochemical and mineral composition analyses,low-temperature gas(CO_(2),N2)adsorption experiments and nu⁃clear magnetic resonance(NMR)scanning methods are employed,combined with multi-scale fractal theory,to comprehensively analyze the changes in shale micro-porous structure and its multi-scale fractal characteristics.The detailed mechanisms by which ScCO_(2) affects shale pore structure are clarified.The study results show that after ScCO_(2) treatment,the total organic carbon(TOC)content of the shale samples decreases,the quartz con⁃tent increases,while the contents of clay minerals and feldspar decrease.Compared to temperature variations,TOC and mineral components are more sensitive to pressure changes.Additionally,shale pores are mainly dis⁃tributed in the micropore range(0-2 nm)and mesopore range(2-50 nm),which contribute significantly to the specific surface area,while macropores(>50 nm)are fewer but significantly contribute to the total pore vol⁃ume.After ScCO_(2) treatment,the total specific surface area of the shale samples decreases,while the total pore volume,average pore diameter,and effective porosity all increase.The total specific surface area and average pore diameter are more sensitive to temperature changes,while the total pore volume and effective porosity are more significantly influenced by pressure.Moreover,shale pores exhibit multi-scale fractal characteristics:mi⁃cropores have a higher fractal dimension,while meso-and macropores have lower fractal dimensions.After Sc⁃CO_(2) treatment,the fractal dimensions at all scales decrease,indicating an improvement in the complexity of the shale pore structure.The fractal dimension of micropores is significantly positively correlated with TOC con⁃tent,while the fractal dimension of meso-and macropores has a stronger correlation with

关 键 词:超临界CO_(2) 页岩 微观孔隙结构 多尺度分形 低温气体吸附 核磁共振 CCUS 

分 类 号:TE122.2[石油与天然气工程—油气勘探]

 

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