注空气促抽低渗煤层瓦斯的模拟研究

Simulation Study on Air Injection to Promote Gas Extraction from Low Permeability Coal Seam

针对低渗透性煤层抽采瓦斯难度较大、瓦斯抽采率偏低等问题,基于煤层渗流、扩散、多元气体的竞争性吸附作用,建立了煤层注空气提高瓦斯抽采效果的气固耦合模型;利用Comsol Multiphysics软件模拟了在不同的注气时间下,煤层注空气后煤层瓦斯压力和瓦斯含量参数的变化规律。对比分析了注空气瓦斯抽采和单一抽采条件下的瓦斯抽采效果,论证了煤层注空气促抽煤层瓦斯工艺的可行性。模拟结果表明,注气压力为1 MPa,在单一抽采条件下,通过向煤层注空气能够促使其瓦斯含量以及瓦斯压力大幅度地降低。在相同的时间下,相比于单一抽采,注空气促抽使煤层瓦斯压力降低了5.88~32.35个百分点,瓦斯含量降低了5.72~19.47个百分点。

The gas-solid coupling model of air injection in coal seam to improve gas extraction effect was developed in order to address the issues of challenging gas extraction and low gas extraction rate in low permeability coal seams.This model is based on coal seam seepage,diffusion,and competitive adsorption of various gases.The fluctuation of gas pressure and gas content characteristics in coal seams following air injection at various gas injection times was simulated using Comsol Multiphysics software.The possibility of gas extraction by air injection in coal seams was proven.The effects of gas extraction by air injection and gas extraction by single injection were contrasted and assessed.The simulation results show that the gas injection pressure is 1 MPa,and the gas content and pressure can be greatly reduced by injecting air into coal seam under a single extraction condition.At the same time,compared with single drainage,the gas pressure and gas content of coal seam are reduced by 5.88 percentage points-32.35 percentage points and 5.72 percentage points-19.47 percentage points by air injection.