Abstract
The effective radius of methane extraction after high-pressure water jet slotting is the most important parameter for borehole optimization and extraction time planning. We applied a steady flow model and thermal-hydrological-mechanical (THM) coupling model to calculate the effective radius after high-pressure water jet slotting. Field measurements at the Zhongliangshan coal mine show that both the steady flow model and the THM coupling model can accurately represent the effective radius, and the THM coupling model provides further information regarding extraction time. After that, a variety of factors, including extraction time, coal burial depth, slot radius, initial permeability, and initial methane pressure, are discussed. The effective radius of a slotted borehole is 1.94 times larger than that of a conventional borehole.
Highlights
Coalbed methane (CBM) extraction is an intensive method for reducing the security risk of coal and methane outbursts during mine production [1] that can provide cleaner energy resources [2] and potentially reduce greenhouse gas emissions [3]
To provide improved guidance for methane extraction, we propose an efficient and robust method within a thermal-hydrological-mechanical (THM) coupling model to calculate the effective radius of methane extraction after high-pressure water jet slotting
To establish the THM coupling model for methane extraction after high-pressure water jet slotting, we suggest the following basic assumptions [30,31,32]: (1) the coal seams are homogeneous and isotropic porous media; (2) the deformation of coal skeleton and porosity is minimal and can be described by the linear elasticity criterion; (3) thermodynamic parameters of coal seams and methane are temperature independent; (4) the coal seams are saturated by methane; (5) methane adsorption on coal can be represented by the Langmuir model, and the free methane is an ideal gas
Summary
Coalbed methane (CBM) extraction is an intensive method for reducing the security risk of coal and methane outbursts during mine production [1] that can provide cleaner energy resources [2] and potentially reduce greenhouse gas emissions [3]. The most important parameter to consider during this process is the effective methane extraction radius after high-pressure water jet slotting, which has been determined empirically. To provide improved guidance for methane extraction, we propose an efficient and robust method within a thermal-hydrological-mechanical (THM) coupling model to calculate the effective radius of methane extraction after high-pressure water jet slotting. Numerical simulations, model validation, and sensitivity analysis to detect the methane distribution after slotting
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