Evolution mechanism of main control factors for coalbed methane extraction
Borehole gas extraction is one of the most economical and effective methods for comprehensive gas utilization and disaster prevention.To study the evolution mechanism of the main control factors in coal seam gas extraction process,a multi-field coupling model for gas migration was established and solved using COMSOL Multiphysics software.The results indicate that,due to the influence of coal pore and fracture network structure,there is an asynchrony between the changes in matrix gas pressure and fracture gas pressure,making it difficult for gas to migrate from the matrix.The fracture system and matrix system jointly control the gas migration ability of the coal body.In the early stage of gas extraction,the gas migration process is mainly controlled by the fracture system.At this time,increasing the permeability of the coal seam can effectively improve the gas extraction efficiency.As the gas extraction processing,the gas migration process gradually shifts to be controlled by the matrix system.It is hard to effectively improve the gas extraction efficiency by just increasing the permeability of the coal body.Measures should be taken to improve the diffusion performance of the coal matrix.
gas extractionmain control factorsmulti-field couplinggas diffusionnumerical model
NETL
NSTL
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