Permeability-Enhancing Technology through Liquid CO 2 Fracturing and Its Application

Zebiao Jiang, Xiping Quan, Shixiang Tian (), Hao Liu (), Yaling Guo, Xiangxiang Fu and Xifa Yang
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Zebiao Jiang: Key Laboratory of Comprehensive Utilization of Nonmetallic Mineral Resources in Guizhou, School of Mining, Guizhou University, Guiyang 550025, China
Xiping Quan: Key Laboratory of Comprehensive Utilization of Nonmetallic Mineral Resources in Guizhou, School of Mining, Guizhou University, Guiyang 550025, China
Shixiang Tian: Key Laboratory of Comprehensive Utilization of Nonmetallic Mineral Resources in Guizhou, School of Mining, Guizhou University, Guiyang 550025, China
Hao Liu: College of Aerospace Engineering, Chongqing University, Chongqing 400044, China
Yaling Guo: Key Laboratory of Comprehensive Utilization of Nonmetallic Mineral Resources in Guizhou, School of Mining, Guizhou University, Guiyang 550025, China
Xiangxiang Fu: College of Aerospace Engineering, Chongqing University, Chongqing 400044, China
Xifa Yang: Key Laboratory of Comprehensive Utilization of Nonmetallic Mineral Resources in Guizhou, School of Mining, Guizhou University, Guiyang 550025, China

Sustainability, 2022, vol. 14, issue 16, 1-23

Abstract: Liquid carbon dioxide (CO 2 ) phase change fracturing (LCPCF) is an innovative technique to improve the efficiency of gas drainage from low-permeability coal seams of high gas content. However, fracture sprouting, extension and displacement changes of coal under LCPCF need further study, and corresponding field tests are also lacking. Therefore, a mechanical model based on the thermodynamic theory of CO 2 phase change is developed in this paper. Then, the pressure change characteristics, crack propagation and displacement change of coal subjected to LCPCF were analyzed through numerical simulation. In addition, the permeability-enhancing effect of the field LCPCF test was analyzed. The results obtained from the numerical simulation show that during the LCPCF process, the crack-generation process changes with pressure as follows: microfracture–numerous microfractures–major macrofracture–macrofractures. During the development of fractures, the stress is incompletely symmetrically distributed in coal centered on the fracturing borehole. The failure occurs stochastically in the coal in the vicinity of the fracturing borehole at first, and then it gradually propagates to the inner seam of coal as the gas pressure increases. The following result can be obtained from field experiments: the permeability coefficient of coal seams after increasing the permeability through LCPCF is 2.60~3.97 times that of coal seams without presplitting. The average concentration of gas extracted in coal seams within the zone having undergone an increase in permeability through liquid CO 2 fracturing is 2.14 times greater than that within the zone without presplitting. The average pure amount of gas extracted within the zone having undergone an increase in permeability through LCPCF is 3.78 times greater than that within the zone without presplitting. By comparing coal seams before and after fracturing in the field test, it can be seen that the LCPCF presents a favorable effect in increasing the permeability of low-permeability coal seams. This provides an effective approach for increasing the permeability of coal seams in coal mines with similar geological conditions.

Keywords: LCPCF; numerical simulation analysis; mechanical analysis; fracturing effect (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
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