气相压裂增透技术强化煤层瓦斯抽采效果的研究

Study on strengthening methane extraction effect of coal seam by gas fracturing permeability enhancement technology

针对高瓦斯低透煤层瓦斯抽采效果差、抽采成本高、抽采时间长等问题,通过应用气相压裂增透技术来强化煤层的瓦斯抽采效果,实验和现场测试分析压裂前后煤样的孔隙裂隙基本参数变化情况,明确增透强化的机理。结果表明:气相压裂煤层孔容和比表面积均以大孔为主;在不同吸附平衡压力和粒径下,压裂煤层的扩散系数随着时间的延长减小的幅度存在差异;气相压裂后煤层孔隙裂隙基本参数都呈现增大的趋势,有利于缩短瓦斯扩散路径,提高瓦斯扩散系数;气相压裂后,钻孔有效抽采半径、煤层透气性系数和渗透率分别提高了2.1~4.3倍、54~96倍和7.54~30.40倍,从而判定压裂煤层由原始难抽采煤层转化为易抽采煤层,气相压裂增透强化瓦斯抽采效果明显。

In view of the problems of poor gas extraction effect,high extraction cost and long extraction time in high gas and low permeability coal seam,gas phase fracturing technology was applied to strengthen gas extraction effect in coal seam.The basic parameters of pore and fracture of coal samples before and after fracturing were analyzed by experiment and field test,and the mechanism of permeability enhancement was clarified.The results showed that the pore volume and specific surface area of fractured coal seam were mainly macroporous;the diffusion coefficient of fractured coal seam decreases with time at different adsorption equilibrium pressures and particle sizes;after gas fracturing,the basic parameters of coal seam pore and fracture showed an increasing trend,which was conducive to shortening gas diffusion path.After gas phase fracturing,the effective extraction radius of borehole,permeability coefficient and permeability of coal seam were increased by 2.1~4.3 times,54~96 times and 7.54~30.40 times,respectively,so that it can be judged that fractured coal seam was transformed from original difficult-to-extract coal seam to easy-to-extract coal seam,and the effect of gas phase fracturing was obvious.