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水力压裂是改变岩体结构的一种人为手段,为控制压裂裂隙的扩展方向,需要研究定向水力压裂导控技术。根据裂隙产生及扩展机理,通过水力压裂力学分析,总结出轴向楔形槽导控、环形楔形槽导控及控制孔导控3种定向水力压裂导控方法。为对比分析3种导控方法的效果,运用数值模拟试验方法,对常规(非定向)压裂、轴向楔形槽导控压裂、环形楔形槽导控压裂及控制孔导控压裂进行了数值模拟,通过声发射及剪应力分布研究了4种压裂方式下压裂过程中裂隙扩展动态特征,对比分析了4种压裂方式的微裂压力及破裂压力。结果表明:3种导控方法均可起到控制裂隙发展方向的作用,且有效降低了水力压裂的微裂压力和破裂压力,3种导控方法中以轴向楔形槽导控为最优。
Hydraulic fracturing is a man-made method to change the rock mass structure. To control the direction of fracturing, it is necessary to study directional hydraulic fracturing control technology. According to the mechanism of fissure generation and propagation, hydraulic fracturing mechanics analysis shows that three kinds of directional hydraulic fracturing control methods are axial wedge groove control, annular wedge groove control and control hole pilot control. In order to compare and analyze the effect of the three kinds of control methods, numerical simulation tests are carried out to study the effects of conventional (non-directional) fracturing, axial wedge groove pilot fracturing, annular wedge groove pilot fracturing and pilot hole pilot fracturing Numerical simulations were carried out to study the dynamic characteristics of fracture propagation during fracturing with four kinds of fracturing methods through acoustic emission and shear stress distribution. The microcracking pressure and fracture pressure of four kinds of fracturing methods were compared and analyzed. The results show that all the three kinds of control methods can play the role of controlling the development direction of fractures and effectively reduce the micro-cracking pressure and rupture pressure of hydraulic fracturing. .