低透气性煤层多孔同步分段水力压裂增透技术研究

Segmented hydraulic fracturing technology by multi-hole synchronous drilling in low permeability coal seams

为了提高煤层透气性的增透效率,研究了煤层多孔同步分段水力压裂增透技术,介绍了多孔同步分段水力压裂技术的基本原理,通过实验室测试了高压封孔胶囊的耐压强度及多孔同步分段水力压裂系统的自动控制工艺,结果表明:高压封孔胶囊的最小破坏强度为35 MPa,多孔同步分段水力压裂可通过自动控制系统实时监测每个钻孔的压力数据,实现压裂过程的自动控制。同时在三元煤矿进行了现场工业试验,工业试验表明,3#煤层的起裂压力为23.3~25.4 MPa,当压裂距离为10 m时,压裂孔的裂纹扩展时间为26~38 min,裂纹沟通时间为28~40 min,可有效提高压裂效率。经过多孔同步分段水力压裂增透的煤层,相对于未压裂煤层,在30 d的统计时间内,压裂后的平均瓦斯浓度是未压裂的1.12倍,平均混合流量是未压裂的2.17倍,平均瓦斯纯量是未压裂的2.44倍,能够有效的增加煤层透气性,提高瓦斯抽采效果。

In order to improve the permeability improving efficiency of coal seams,we researched on hydraulic fracturing technology with multi-hole synchronous drilling.Based on the basic principle of this technology,we did a laboratory test for the compressive strength of high-pressure sealing capsule and the automatic control process of hydraulic fracturing system with multi-hole synchronous drilling.The test shows the minimum failure strength is 35 MPa;the automatic control system of this technology can monitor real time pressure data of each hole;the fracturing process is controlled automatically in this system.We made an on-site industrial test at Sanyuan Coal Mine.The industrial test shows that the starting pressure of No.3 coal seam is 23.3~25.4 MPa;when the fracturing distance is 10 m,the crack extension time of a fracturing hole is 26~38 min and the cracks connecting time is 28~40 min;the data shows the fracturing efficiency is effectively improved.In a 30 d statistic period,the average gas concentration after fracturing is 1.12 times,the average mixing flow is 2.17 times,and the average gas purity is 2.44 times,that of the unfractured coal seam.This technology is proved to effectively increase the permeability of coal seams and improve the gas extraction effect.