单一低透煤层脉动水力压裂脉动波破煤岩机理

针对单一低透气性高瓦斯煤层瓦斯抽采困难的现状，采用理论研究、物理实验和现场测试相结合的方式，研究了高压脉动压裂过程中脉动应力波的产生、传播及对煤岩体的破坏机理，通过实验室试验，研究了脉动压裂与常规压裂的不同。研究表明：脉动应力波的反射与叠加使某些位置应力增大，某些位置应力减小，加之煤岩体的能量积聚作用，可以以较小的脉动压力产生比较大常规压力更好的压裂效果。应用该原理开发了高压脉动压裂卸压增透技术，经现场实施表明：脉动压裂起裂压力为8 MPa，为常规压裂起裂压力的1/2，压裂影响半径为8 m，脉动压裂后单孔瓦斯抽采量为普通抽采孔的3.6倍，最高为50 L/min，抽采流量为未压裂孔的4倍，是常规压裂孔的1.2倍。

The mechanism of breaking coal and rock by pulsating pressure wave in single low permeability seam

In terms of the difficulty of gas drainage in single coal seam with high gas contents and low permeability，this study investigated the pulsating stress wave generation，propagation and the mechanism of coal and rock breakage using theoretical review，laboratory experiment and field test.Also，the difference between pulsating hydraulic fracturing and normal hydraulic fracturing was investigated through laboratory test.The study shows that the pulsating stress wave reflection and superposition can make stress increase in some areas，and reduce in other areas.In addition to the energy accumulation effect in coal and rock，it results in that a small pulsating pressure generates a better fracturing effect than that by normal hydraulic fracturing.Based on the study，a pulsating hydraulic fracturing technology for low permeability coal seam has been developed.The site test result shows that the initiation pressure of pulsating hydraulic fracturing is 8 MPa，which is half less than that in normal hydraulic fracturing，and pulsating hydraulic fracturing influence radius reaches 8 m.The total amount of gas extraction using pulsating hydraulic fracturing method is 3.6 times more than that using normal hydraulic fracturing.The drainage discharge increases greatly，which is 4 times higher than that in drilling drainage and 1.2 times higher than that in normal hydraulic fracturing.