高压水力割缝技术工程实践及瓦斯抽采影响因素探讨

Exploring Engineering Practice of High Pressure Hydraulic Slitting Technology and Influencing Factors of Gas Extraction

针对低渗煤层瓦斯抽采难度大、抽采效率低以及抽-掘-采衔接不紧密等难题,以大佛寺煤矿4#煤层为研究对象,开展了顺层钻孔高压水力割缝现场试验,考察了水力割缝效果。结果表明:(1)当割缝压力为70 MPa,割缝时间为10~15 min时,等效割缝半径为1.16~1.41 m;(2)受水锁效应影响,割缝钻孔瓦斯抽采参数随时间的变化过程可分为抽采初期、抽采稳定期和抽采衰减期3个阶段,其单孔平均抽采浓度、纯流量分别是常规钻孔的1.81~2.36倍和1.93~4.50倍,且割缝间距越小提升效果越显著,衰减越慢;(3)随着负压的增大,割缝钻孔的抽采浓度加速降低,抽采纯流量和混合流量不断升高,但抽采纯流量的增长幅度远小于混合流量的增幅,且差距逐渐拉大。由此可见,高压水力割缝能够增强煤层渗透率,提高瓦斯抽采效率。

Aiming at the difficulties of gas extraction in low-permeability coal seams,low extraction efficiency and poor connection between extraction and mining,a high-pressure hydraulic slitting field test was carried out on the No.4 coal seam in Dafosi coal mine to investigate the effect of hydraulic slitting.The results show that:(1)when the cutting pressure is 70 MPa and the cutting time is 10-15 min,the equivalent cutting radius is 1.16-1.41 m;(2)influenced by the water lock effect,the change process of gas extraction parameters of the cutting borehole with time can be divided into three stages:the initial extraction period,the extraction stabilisation period and the extraction decay period,and the average extraction concentration and pure flow rate of the single hole are 1.81-2.36 times and 1.93-4.50 times of those of the conventional borehole respectively;(3)with the increase of negative pressure,the extraction concentration of the slit borehole decreases at an accelerated rate,and the pure and mixed flow rates increase continuously,but the increase of the pure flow rate is much smaller than the increase of the mixed flow rate,and the gap is gradually widened.This shows that high-pressure hydraulic slitting can enhance coal seam permeability and improve gas extraction efficiency.