Study on Numerical Simulation of Gas–Water Two-Phase Micro-Seepage Considering Fluid–Solid Coupling in the Cleats of Coal Rocks

Cheng Qian, Yaxi Xie (), Xiujun Zhang, Ruiqi Zhou and Bixin Mou
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Cheng Qian: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Yaxi Xie: College of Energy, Chengdu University of Technology, Chengdu 610059, China
Xiujun Zhang: Sichuan Institute of Energetical and Geological Survey, Chengdu 610072, China
Ruiqi Zhou: Sichuan Institute of Energetical and Geological Survey, Chengdu 610072, China
Bixin Mou: Sichuan Institute of Energetical and Geological Survey, Chengdu 610072, China

Energies, 2024, vol. 17, issue 4, 1-16

Abstract: The increasing demand for natural gas energy will promote unconventional natural gas, such as coal seam gas and shale gas, to play a key role in future energy development. The mechanical properties of coal seams are weaker compared with conventional natural gas reservoirs. The fluid–solid coupling phenomenon exists widely at the pore scale and macro scale of coal seams, and runs through the whole process of coalbed gas exploitation. The objective of this study is to establish a microscale gas–water flow model for coalbed methane considering fluid structure coupling. Frist, this study used scanning electron microscopy (SEM) to obtain microscopic pore images of coal rocks. Then, we constructed a numerical model to simulate the movement of coalbed methane and water within the scale of coal cleats based on the Navier–Stokes equation, phase field method, and solid mechanics theory. Finally, we analyzed the effects of injection pressure and wettability on the microscopic two-phase seepage characteristics and displacement efficiency of coal. Our research shows that when the injection pressure is increased from 60 kPa to 120 kPa, the displacement completion time is shortened from 1.3 × 10 −4 s to 7 × 10 −5 s, and the time is doubled, resulting in a final gas saturation of 98%. The contact angle increases from 45° to 120°, and the final gas saturation increases from 0.871 to 0.992, an increase of 12.2%.

Keywords: CBM; micro-seepage; gas–water two-phase; fluid–solid coupling; numerical simulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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