油气地质与采收率2025，Vol.32Issue(6)：28-41,14.DOI:10.13673/j.pgre.202406003
构造变形页岩纳米孔隙结构及其分形特征
Nano-pore structure and fractal characteristics of tectonically deformed shale:A case study of Longmaxi Formation in Dabashan foreland thrust belt,northeastern Chongqing
摘要
Abstract
As an essential layer system for shale gas exploration in southern China,the shale of the Longmaxi Formation in northeastern Chongqing has undergone multi-stage tectonic movement superposition and transformation,and its nano-pore structure and fractal characteristics have not been systematically explained.Through the observation of nano-pore morphology by field emission scanning electron microscopy(FESEM)and the quantitative characterization of pore structures based on Image J software,combined with the specific surface area,pore volume,and pore size distribution parameters obtained by low-temperature N2 adsorption experiments,the FHH fractal model was used to calculate the pore fractal dimension.The fractal characteristics and influencing factors of nano-pores in the tectonically deformed shale of the Longmaxi Formation in the Dabashan foreland thrust belt in northeastern Chongqing were systematically revealed.The results show that the tectonically deformed shale of the Longmaxi Formation in the study area primarily develops organic matter pores,intergranular pores,and intragranular pores,with the reservoir space dominated by mesopores,accounting for an average of 59.30%.The calculation results of the FHH fractal model indicate that the low-temperature N2 adsorption-desorption curve of the tectonically deformed shale of the Longmaxi Formation begins to show a hysteresis loop when the relative pressure P/P0=0.45.Based on this,the fractal dimension D is divided into D1 in the low pressure region(P/P0<0.45)and D2 in the high pressure region(P/P0≥0.45).The average D1 is 2.609 0,and the average D2 is 2.657 1,indicating that the nano-pores of the tectonically deformed shale have obvious fractal characteristics.With the increase in specific surface area and pore volume,the fractal dimension also increases;the pore structure becomes more complex,and heterogeneity is stronger.There is a significant positive correlation between the total organic carbon content and the fractal dimension,which confirms that the hydrocarbon generation and pressurization during the thermal evolution of organic matter promote the development of nano-pores.The quartz content is positively correlated with the fractal dimension,reflecting the protective effect of rigid minerals on pore structure.Clay minerals are negatively correlated with fractal dimension,indicating that plastic minerals reduce the complexity of pore structure through particle recombination under tectonic stress.关键词
构造变形/页岩/纳米孔隙/分形特征/龙马溪组/渝东北地区Key words
tectonic deformation/shale/nano-pore/fractal characteristic/Longmaxi Formation/northeastern Chongqing分类
能源科技引用本文复制引用
潘妍妍,杨满平,路艳军,林郁,魏铭伯,朱洪建..构造变形页岩纳米孔隙结构及其分形特征[J].油气地质与采收率,2025,32(6):28-41,14.基金项目
国家自然科学基金项目"页岩纳米孔隙结构演化的构造约束机制及页岩气意义"(42102186),河北省自然科学基金优秀青年科学基金项目"基于高温高压实验的页岩剪切变形与纳米孔隙响应机制研究"(D2023203008),河北省高等学校科学技术研究项目"构造-岩浆热作用对页岩微纳米级孔-缝与储层物性的改造机理研究"(BJK2022018). （42102186）
