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A constant suction negative pressure is used in coal mines owing to a lack of research on the effects of diffusion and suction negative pressure on methane extraction, resulting in the low methane concentration and utilization rate. In this study, Comsol Multiphysics is used to conduct a numerical solution of a gas–solid coupling model considering pseudo-steady diffusion in coal matrix, seepage in...
The evolution of the petrophysical properties (porosity/permeability) of lignite, subbituminous and high-volatile bituminous coals (LSBC) and the effects of the first coalification jump on the pore-cleat physical properties are still poorly understood. We investigated the pore-cleat heterogeneity, volume, aperture, connectivity and pore-contributed porosity/permeability with increasing coal ranks...
Ultrasonic waves can potentially be used to improve the permeability of low-permeability coalbed methane (CBM) reservoirs by enhancing cleats propagation and new cracks generation. Two polished blocks of semi-anthracite coal were subjected to ultrasonic waves for 360h without confining stress. The variations in cracks development due to the effects of original cracks (especially face cleats) and of...
Various sizes of pores in coal, which are generally formed by organic matter during the coalification process, have a direct influence on coalbed methane extraction. However, few studies have investigated the pore size distributions across the thermal evolution of coal from peat to anthracite. In this project, three series of coal samples collected from three key CBM development basins with graded...
Liquid carbon dioxide (LCO2) fracturing technology has been applied in the enhanced coalbed methane recovery (ECBM), and it has made some progress in the physical experiments and field applications. However, the freeze phenomenon during the injection process might induce coal matrix shrinkage, hindering the fracturing efficiency. A multiple cycle LCO2 fracturing technology is proposed, and the feasibility...
Coal structure determines the porosity and permeability in coal reservoirs to a great extent, which not only influences the evaluation of coalbed methane (CBM) reservoirs, but is also closely related to their production efficiency. The traditional methods for identifying coal structure mainly depend on coals in boreholes or underground roadway sections. However, as these methods are expensive and...
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