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

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 b...

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Bibliographic Details
Published inEnergies (Basel) Vol. 16; no. 4; p. 1718
Main Authors Wang, Yuan, Zhong, Liguo, Zhang, Lei, Zou, Junpeng
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 01.02.2023
Subjects
CBM seepage
Coal
Coalbed methane
Drainage
Environmental aspects
Gas fields
Gas production
Hydraulic fracturing
Mathematical models
Natural gas
Oil and gas production
Oil wells
Partial differential equations
Permeability
Pressure
production rate
Propagation
reservoir pressure model
Reservoirs
Viscosity
China
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Summary: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, Rpk, is defined to quantitatively describe the influence of coal seam permeability on the evolution of reservoir pressure. Rpk 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.
ISSN:1996-1073
1996-1073
DOI:10.3390/en16041718