Multi-method characterization of sandstone pore size distribution heterogeneity and its influence on porosity and permeability variation  

作　　者：Junjian ZHANG Fangkai QUAN Hui ZHANG Yinchuan SHAO Yanning HAN Yuqiang YANG Xiangchun CHANG Xiaoyang ZHANG 

机构地区：[1]College of Earth Sciences&Engineering,Shandong University of Science and Technology,Qingdao 266590,China [2]Key Laboratory of Coalbed Methane Resource&Reservoir Formation Process(Ministry of Education),China University of Mining and Technology,Xuzhou 221008,China [3]School of Safety Science and Engineering,Anhui University of Science and Technology,Huainan 232001,China [4]Geophysical Prospecting and Surveying Team of Shandong Bureau of Coal Geological,Jinan 250104,China [5]Shandong Engineering Research Center of Mine Gas Disaster Prevention,Qingdao 266427,China

出　　处：《Frontiers of Earth Science》2024年第4期814-830,共17页地球科学前沿(英文版)

基　　金：sponsored by the This research was sponsored by the Research Fund of Shandong Coalfield Geological Bureau(No.2022-003);Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process of the Ministry of Education(China University of Mining and Technology)(No.2023-007);Shandong Coalfield Geological Bureau Research Special Project of 2024s(No.MTDZKY-2024-35).

摘　　要：Pore volume/surface area and size distribution heterogeneity are two important parameters of pore structures,which restrict the gas-water-oil migration process in sandstone reservoirs.The fractal theory has been proved to be one of the most effective methods to quantify pore distribution heterogeneity.However,the dynamic variation of porosity and permeability due to fractal characteristics has been rarely studied.In this paper,physical properties,mineral composition,and pore distribution of 18 groups of sandstone samples were analyzed using scanning electron microscope(SEM)and high-pressure mercury injection tests.Then,Sierpinski model,Menger model,thermodynamic model,and multi-fractal model were used to calculate the fractal dimension of the pore volume.Thus,the relationship between fractal dimension and porosity/permeability variation rate,and pore compressibility were studied.The results are as follows.1)All samples can be divided into three types based on pore volume(0.9 cm3∙g−1)and mercury removal efficiency(35%),i.e.,Type A(<0.9 cm3∙g−1and<35%);Type B(>0.9 cm3∙g−1 and<35%);Type C(>0.9 cm3∙g−1 and>35%).2)Four fractal models had poor applicability in characterizing fractal characteristics of different sample types.The fractal dimension by the Sierpinski model had a good linear correlation with that of other models.Pores with smaller volumes dominated the overall pore distribution heterogeneity by multi-fractal dimension.The pore diameter between 200−1000 nm and larger than 1000 nm was the key pore size interval that determined the fractal characteristics.3)With the increase of confining pressures,porosity and permeability decreased in the form of a power function.The compressibility coefficient of typical samples was 0.002−0.2 MPa−1.The compressibility of Types A and B was significantly higher than that of Type C,indicating that the total pore volume was not the key factor affecting the pore compressibility.The correlation of compressibility coefficient/porosity variation rate with pore

关 键 词：tight sandstone/pore size distribution/fractal dimension/multi-fractal model/permeability-porosity 

分 类 号：O17[理学—数学]