碎软低渗煤层水力冲孔影响范围的数值模拟

Numerical simulation of the influence range of hydraulic punching in crushed soft and low permeability coal seam

水力冲孔是一种适用于碎软低透煤层的卸压增透强化瓦斯抽采技术。冲孔的有效影响范围决定着合理钻孔的布置参数,而合理的钻孔布置参数是保障煤层瓦斯高效抽采的前提。为了提升瓦斯抽采效果,针对某矿碎软低渗煤层采用水力冲孔措施时遇到的影响半径难以确定的问题,基于瓦斯煤体变形及瓦斯渗流理论,通过COMSOL-Multiphysics数值模拟的方法建立钻孔瓦斯抽采流固耦合模型,研究不同抽采时间条件下不同破煤量对有效影响范围的影响。研究结果表明,在相同的抽采时间条件下,经水力冲孔改造后的钻孔抽采有效影响范围相比原始钻孔有效影响范围有显著提升,并且随着破煤量的增加,抽采有效影响范围逐渐增大。通过现场实测法对水力冲孔有效影响半径进行现场考察,实测结果与模拟结果基本一致,验证了水力冲孔措施具有良好的卸压增透效果。

Hydraulic punching is a gas extraction technology suitable for pressure relief and permeability enhancement in crushed, soft and low permeability coal seams.The effective influence range of punching determines the reasonable drilling parameters, and reasonable drilling parameters are the premise of ensure efficient coal seam gas extraction.In order to improve the effect of gas extraction, in view of the problem that the influence radius is difficult to determine when hydraulic punching measures are adopted in the crushed soft and low permeability coal seam of a certain mine, based on gas coal body deformation and gas seepage theory, a fluid-solid coupling model of drilling gas extraction was established by COMSOL-Multiphysics numerical simulation method to study the effect of different coal breaking amounts on the effective influence range under different extraction time conditions.The research results show that under the same extraction time conditions, the effective influence range of the drilling extraction after the hydraulic punching reconstruction is significantly improved than the effective influence range of the original drilling, and with the increase of the amount of broken coal, the effective influence range of the extraction gradually increases.The effective influence radius of hydraulic punching is investigated on-site by the field measurement method.The measured results are basically consistent with the simulation results, which verifies that the hydraulic punching measures have a good effect of pressure relief and permeability enhancement.