Effect of cyclic hydraulic stimulation on pore structure and methane sorption characteristics of anthracite coal: A case study in the Qinshui Basin, China  

作　　者：Rui-Shuai Ma Ji-Yuan Zhang Qi-Hong Feng Xue-Ying Zhang Yan-Hui Yang 

机构地区：[1]State Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao,266580,Shandong,PR China [2]School of Petroleum Engineering,China University of Petroleum(East China),Qingdao,266580,Shandong,PR China [3]Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)),Ministry of Education,Qingdao,266580,Shandong,PR China [4]Shandong Institute of Petroleum and Chemical Technology,Dongying,257000,Shandong,PR China [5]PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,PR China [6]PetroChina Huabei Oilfield Company,Renqiu,062552,Hebei,PR China

出　　处：《Petroleum Science》2024年第5期3271-3287,共17页石油科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China (51904319);the Fundamental Research Funds for the Central Universities (21CX06029A)。

摘　　要：The cyclic hydraulic stimulation(CHS) has proven as a prospective technology for enhancing the permeability of unconventional formations such as coalbeds. However, the effects of CHS on the microstructure and gas sorption behavior of coal remain unclear. In this study, laboratory tests including the nuclear magnetic resonance(NMR), low-temperature nitrogen sorption(LTNS), and methane sorption isotherm measurement were conducted to explore changes in the pore structure and methane sorption characteristics caused by CHS on an anthracite coal from Qinshui Basin, China. The NMR and LTNS tests show that after CHS treatment, meso- and macro-pores tend to be enlarged, whereas micropores with larger sizes and transition-pores may be converted into smaller-sized micro-pores. After the coal samples treated with 1, 3, 5 and 7 hydraulic stimulation cycles, the total specific surface area(TSSA)decreased from 0.636 to 0.538, 0.516, 0.505, and 0.491 m^(2)/g, respectively. Fractal analysis based on the NMR and LTNS results show that the surface fractal dimensions increase with the increase in the number of hydraulic stimulation cycles, while the volume fractal dimensions exhibit an opposite trend to the surface fractal dimensions, indicating that the pore surface roughness and pore structure connectivity are both increased after CHS treatment. Methane sorption isothermal measurements show that both the Langmuir volume and Langmuir pressure decrease significantly with the increase in the number of hydraulic stimulation cycles. The Langmuir volume and the Langmuir pressure decrease from 33.47 cm^(3)/g and 0.205 MPa to 24.18 cm^(3)/g and 0.176 MPa after the coal samples treated with 7 hydraulic stimulation cycles, respectively. The increments of Langmuir volume and Langmuir pressure are positively correlated with the increment of TSSA and negatively correlated with the increments of surface fractal dimensions.

关 键 词：Coalbed methane Cyclic hydraulic stimulation Pore structure Methane sorption characteristics Fractal analysis 

分 类 号：TE37[石油与天然气工程—油气田开发工程]