基于煤体各向异性的瓦斯热流固耦合抽采特性研究

Study on the Characteristics of Gas Thermal-Fluid-Solid Coupled Extraction Based on Anisotropy of Coal Body

为研究煤层渗透率各向异性影响下瓦斯抽采的相关特性,同时考虑温度变化对瓦斯渗流和煤体变形的影响,建立了煤岩变形场、渗流场、温度场的热流固耦合模型。使用COMSOL Multiphysics软件进行模拟求解,研究初始渗透率、初始煤层温度以及初始瓦斯压力对有效抽采区域的影响规律。研究表明:考虑渗透率各向异性下,钻孔周围呈现出椭圆形压降区域,且随抽采时间的增加蔓延为鼓形,钻孔周围应力重新分布;渗透率较大的区域瓦斯渗流速度快,瓦斯抽采效率高;煤层温度随抽采过程的进行不断下降至稳定,距钻孔最远处温度最高,煤层初始温度越大,有效抽采区域越小;初始压力越大,吸附瓦斯解吸时间越长,有效抽采区域面积随之降低。

In order to study the relevant characteristics of gas extraction under the influence of anisotropy of coal seam permeability,a thermal-fluid-solid coupling model of coal rock deformation field,seepage field and temperature field was established by considering the influence of temperature change on gas seepage and coal deformation.The COMSOL Multiphysics software was used to simulate and solve the influences of initial permeability,initial coal seam temperature and initial gas pressure on the effective extraction area.The results show that considering the anisotropy of permeability,there is an elliptical pressure drop area around the borehole,which spreads into a drum shape with the increase of extraction time,and the stress around the borehole would be redistributed.The area with large permeability has fast gas seepage speed and high gas extraction efficiency.The temperature of coal seam decreases to a stable state with the process of extraction,and the temperature is the highest at the farthest distance from the borehole.The larger the initial temperature of coal seam,the smaller the effective extraction area.The larger the initial pressure,the longer the desorption time of adsorbed gas,and the smaller the effective extraction area.