水力压裂增透技术及应用研究

Research and application of anti-reflection technology of hydraulic fracturing

为解决煤层渗透率低、瓦斯抽采率不高的问题,利用离散元软件RFPA2D-flow进行水力压裂增透数值模拟。首先,模拟不同水压力对单孔裂缝扩展的影响;然后,模拟多点水力压裂,分析中心孔单独压裂和周边孔同步压裂对裂缝扩展发育状态的影响;最后,以马堡煤矿为工作背景,基于理论分析和研究,结合现场工业试验,综合评价水力压裂增透效果。结果表明:考虑钻孔周围地应力的重新分布能够确保数值模拟结果准确可靠;诱导应力会影响后发育裂缝的扩展方向,使后发育裂缝更易与其他裂缝形成网状结构,验证水力压裂增透机制。水压力为27 MPa时,压裂有效半径的模拟结果为2.8 m,与实测抽采钻孔的有效抽采半径3 m基本吻合。

In order to solve problems of low permeability and low gas extraction rate in coal seams,permeability enhancement of hydraulic fracturing was numerically simulated by using discrete element software RFPA2D-flow.Firstly,effect of different water pressure on single-hole fracture propagation was simulated.Secondly,multi-point hydraulic fracturing was simulated,and influence of single fracturing of center hole and simultaneous fracturing of peripheral hole on development state of crack growth was analyzed.Finally,taking Mabao coal mine as working background,anti-reflection effect of hydraulic fracturing was comprehensively evaluated based on theoretical analysis and research and field industrial test.The results show that redistribution of borehole stress can ensure accuracy and reliability of numerical simulation results.Induced stress can affect propagation direction of fracture developed later,making it easier to form a network structure with that developed first,thus verifying anti-reflection mechanism of hydraulic fracturing.In addition,when water pressure is 27 MPa,simulation result of effective radius of fracturing is 2.8 m,which is basically consistent with actual radius of 3 m.