Numerical Study on the Evolution of Reservoir Pressure and CBM Concentration Considering Hydraulic Fractures

Yuan Wang, Liguo Zhong, Lei Zhang and Junpeng Zou ()
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Yuan Wang: Unconventional Oil and Gas Institute, China University of Petroleum, Beijing 102249, China
Liguo Zhong: Unconventional Oil and Gas Institute, China University of Petroleum, Beijing 102249, China
Lei Zhang: PetroChina Coalbed Methane Company Limited, Beijing 100028, China
Junpeng Zou: Faculty of Engineering, China University of Geosciences, Wuhan 430074, China

Energies, 2023, vol. 16, issue 4, 1-16

Abstract: Based on the theories of mass conservation and coalbed methane (CBM) adsorption/desorption, this paper first establishes a novel reservoir pressure model for CBM production, following which, the CBM concentration and production models are also proposed. Then, these models are programmed and solved by means of the finite element method. Taking the Hunchun CBM field in Jilin province, China, as an example, the reservoir pressure, gas concentration, and production characteristics under different hydraulic fracture forms are simulated and investigated. In conclusion, the reservoir pressure decreases very rapidly in a small region near the fracture tip, which we called the “reservoir pressure singularity”. The existence of a hydraulic fracture greatly reduces the reservoir pressure in the process of CBM exploitation. The permeability sensitivity coefficient of reservoir pressure, R pk , is defined to quantitatively describe the influence of coal seam permeability on the evolution of reservoir pressure. R pk decreases logarithmically as the distance from the CBM extraction well increases. The reservoir pressure and CBM recovery rate characteristics in the presence of multiple hydraulic fractures are also investigated. We believe these results could contribute to the design of hydraulic fracturing wells and the evaluation of gas production in a CBM reservoir.

Keywords: reservoir pressure model; hydraulic fracturing; CBM seepage; production rate (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: 2023
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