延安地区延长组长7段湖相泥页岩孔隙结构及分形特征  

Pore structure and fractal characteristics of lacustrine shale in Chang 7 Member of Yanchang Formation,Yan′an area

作　　者：杨迪 赵卫卫 吴佳 李慧 肖颖 YANG Di;ZHAO Weiwei;WU Jia;LI Hui;XIAO Ying(School of Earth Sciences and Engineering,Xi′an Shiyou University,Xi′an,Shaanxi 710065,China;Shaanxi Key Laboratory of Petroleum Accumulation Geology,Xi′an,Shaanxi 710065,China)

机构地区：[1]西安石油大学地球科学与工程学院 [2]陕西省油气成藏地质学重点实验室

出　　处：《录井工程》2025年第1期137-145,共9页Mud Logging Engineering

基　　金：国家重大专项“陆相页岩储气机理与储层精细描述研究”(编号:2017ZX05039⁃001⁃002)。

摘　　要：鄂尔多斯盆地东南缘延安地区延长组长7段是典型的陆相页岩气勘探开发层位。为了解不同成因孔隙及其结构对陆相页岩气吸附作用的影响,利用有机地球化学方法研究了延长组长7段泥页岩的矿物成分,采用氮气低温吸附法研究页岩的孔径分布特征并利用分形理论对页岩中氮的吸附特征进行解析,进而揭示了泥页岩孔隙结构的非均质性。长7段泥页岩有机碳含量为0.50%~6.43%,平均为2.93%;脆性矿物含量为0~46.00%,平均为7.75%;黏土矿物含量为21.00%~59.00%,平均为40.95%。由长7段岩样的分形拟合曲线可知,分形维数可以划分为两段,第一段分形维数D1为2.0294~2.5015,平均为2.2710,对应着长7段泥页岩中较大的微米级裂隙;第二段分形维数D2为2.4893~2.6223,平均为2.5550,与纳米级孔隙相对应,其孔隙结构更为复杂,孔隙内表面比较粗糙,具有极强的非均质性。在长7段泥页岩中,纳米级孔隙是吸附态气体的主要储集空间,而较大的微米级裂隙则是游离态气体的储集空间及渗流通道。The Chang 7 Member of Yanchang Formation in Yan′an area,southeastern margin of Ordos Basin is a typical continental shale gas exploration and development horizon.In order to understand the influence of pores with different genesis and their structures on the adsorption of continental shale gas,the mineral composition of the shale in Chang 7 Member of Yanchang Formation was studied by using organic geochemical methods.The pore size distribution characteristics of shale were studied by nitrogen low temperature adsorption method,and the adsorption characteristics of nitrogen in shale were analyzed by fractal theory,thereby revealing the heterogeneity of shale pore structure.For the shale in Chang 7 Member,the organic carbon content is 0.50%6.43%,with an average of 2.93%;the content of brittle minerals is 046.00%,with an average of 7.75%;the clay mineral content is 21.00%59.00%,with an average of 40.95%.According to the fractal fitting curve of the shale samples of Chang 7 Member,the fractal dimension can be divided into two segments,the fractal dimension of the first segment(D1)is 2.02942.5015,with an average of 2.2710,which corresponds to the larger micronscale fractures in the shale of Chang 7 Member,and the fractal dimension of the second segment(D2)is 2.48932.6223,with an average of 2.5550,which corresponds to the nanoscale pores,and its pore structure is more complex,the inner surface of the pores is relatively rough,and it has strong heterogeneity.In the shale of Chang 7 Member,the nanoscale pores are the main reservoir space for adsorbed gas,while larger micronscale fractures are the reservoir space and flow path for free gas.

关 键 词：延安地区 页岩气 孔隙结构 氮气吸附 分形维数 泥页岩 延长组 

分 类 号：TE132.1[石油与天然气工程—油气勘探]