The Influence of the Injected Water on the Underground Coalbed Methane Extraction

Yanbao Liu, Zhigang Zhang, Wei Xiong, Kai Shen and Quanbin Ba
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Yanbao Liu: Gas Research Branch, Chongqing Research Institute of China Coal Technology and Engineering Group Crop., Chongqing 400037, China
Zhigang Zhang: Gas Research Branch, Chongqing Research Institute of China Coal Technology and Engineering Group Crop., Chongqing 400037, China
Wei Xiong: Gas Research Branch, Chongqing Research Institute of China Coal Technology and Engineering Group Crop., Chongqing 400037, China
Kai Shen: Gas Research Branch, Chongqing Research Institute of China Coal Technology and Engineering Group Crop., Chongqing 400037, China
Quanbin Ba: Gas Research Branch, Chongqing Research Institute of China Coal Technology and Engineering Group Crop., Chongqing 400037, China

Energies, 2020, vol. 13, issue 5, 1-16

Abstract: The increasing demand on coal production has led to the gradually increase of mining depth and more high methane mines, which bring difficulties in terms of coalbed methane (CBM) extraction. Hydraulic fracturing is widely applied to improve the production of CBM, control mine gas, and prevent gas outbursts. It improves coal bed permeability and accelerate desorption and migration of CBM. Even though the impacts of hydraulic fracturing treatment on the coal reservoirs are rare, negative effects could not be totally ignored. To defend this defect, the presented work aims to study the influence of water filtration on coal body deformation and permeability evolution. For this purpose, a simulation based finite element method was developed to build a solid-fluid coupled two-phase flow model using commercial software (COMSOL Multiphysics 5.4). The model was verified using production data from a long strike borehole from Wangpo coal mine in Shanxi Province, China. Several simulation scenarios were designed to investigate the adverse impacts of hydraulic fracturing on gas flow behaviors. The mechanisms of both relative and intrinsic permeability evolutions were analyzed, and simulation results were presented. Results show that the intrinsic permeability of the fracture system increases in the water injection process. The impacts of water imitation were addressed that a critical time was observed beyond which water cannot go further and also a critical pressure exists above which the hydraulic pressure would impair the gas flow. Sensitivity analysis also showed that a suitable time and pressure combination could be observed to maximize gas extraction. This work provides an efficient approach to guide the coal bed methane exploitation and other unconventional gas reservoirs.

Keywords: hydraulic fracturing; methane adsorption; permeability evolution; water saturation; relative permeability; intrinsic permeability (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: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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