Abstract
Liquid nitrogen (LN2) fracturing technology is a novel waterless fracturing technology that has significant potential for application in the development of coalbed methane. However, the changes in the microstructure after coal samples are treated with LN2 freeze thaw are poorly understood. Therefore, a combination of mercury intrusion porosimetry and micro-computed tomography (micro CT) was employed to investigate the evolution of pore and fracture structure of coal samples treated with LN2. The experimental results showed that the pore volume and average pore size of coal samples increase after LN2 freeze thaw. After 12 freeze thaw cycles, the change in pore volume of micropores and minipores of coal samples was not significant, while the pore volume of mesopores and macropores increased significantly before LN2 freeze thaw. The specific surface area of the pores in different size ranges of coal samples increases with the increase in the number of LN2 freeze thaw cycles; the structure of micropores and miniopores were damaged by thermal stress and frost heave force during LN2 freeze thaw; and the pore size gradually increases to form mesopores and macropores. Micro-CT images of coal samples after LN2 freeze thaw indicated the primary fractures of coal sample expanded and generated a large number of secondary fractures. The primary and secondary fractures are interconnected and ultimately form penetrated fracture enhancing the connectivity of fractures, enhancing the connectivity of the fracture structure. The key finding study is expected to provide a theoretical basis for LN2 fracturing.
Funder
State Key Laboratory of Coal Mine Disaster Dynamics and Control
Natrual science foundationg of Henan province
Subject
Condensed Matter Physics,Fluid Flow and Transfer Processes,Mechanics of Materials,Computational Mechanics,Mechanical Engineering
Cited by
2 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献