低渗透煤层合增透技术应用

Application of low permeability coal seam anti-reflection technology

为增加低渗透高瓦斯煤层的透气性,提高瓦斯利用率和抽采效率,提出低渗透煤层复合增透的方法。利用RFPA2D-Flow和FLAC3D软件分别对水力压裂裂缝的起裂、延伸与扩展规律和CO2增透钻孔内提前制造不同长度的预裂缝对爆破致裂增透效果的影响情况进行模拟。进行井下复合增透效果工业试验,运用瓦斯压力降低法分析预裂后煤层瓦斯抽采半径。结果表明:模拟注水压裂27 PMa时,割缝半径约2 m,随着煤壁预裂缝长度增加,CO2爆破致裂影响半径呈线性递增的趋势。现场复合增透后煤层抽采率显著提高,有效半径由原来单一水力压裂的2 m增加到7 m左右。

In order to increase the permeability of low-permeability and high-gas coal seams and improve gas utilization and extraction efficiency,this paper proposed a method for composite anti-reflection of low-permeability coal seams.The effects of crack initiation,extension and expansion of hydraulic fracturing cracks and pre-cracking of different lengths in the CO2 anti-drilling bore on the blasting cracking and anti-reflection effect were simulated by RFPA2D-Flow and FLAC3D software respectively.The industrial test of the underground comprehensive anti-reflection effect was carried out,and the gas extraction pressure radius of the pre-cracked coal seam was analyzed by the gas pressure reduction method.The results show that when the initial water injection fracturing is 27 Pa,the cutting radius is about 2.5 m.With the length of the pre-crack of the coal wall is increased,the impact radius of the CO2 burst is linearly increasing.After the on-site compound anti-reflection,the coal seam drainage rate is significantly improved,and the effective radius is increased from 2 m to 7 m in the original single hydraulic fracturing.