【摘要】 多级脉冲气体松弛岩层地应力、压裂地层的过程中,裂缝内爆燃气体压力分布影响裂缝起裂扩展。应用叠加原理将作用于油水井壁裂缝的复杂载荷分解为单个简单载荷,通过设定与时间相关的气体压力分布函数,根据弹性力学、线弹性断裂力学理论推导油水井射孔后高地应力约束条件下裂缝尖端应力强度因子,得到了爆燃气体压裂井壁岩层起裂扩展条件,该条件可以反映裂缝内随时间变化的气体压力梯度对裂缝形态的影响。算例分析和现场对比试验结果表明,多级脉冲气体加载压裂与单级高能气体压裂相比,起裂压力升高,止裂压力降低,对地层作用时间显著延长,得到的岩层裂缝长度是后者的2~3倍,与水力压裂联作可显著降低地层破裂压力,进一步提高和改善地层渗透性。图3表1参11更多还原

【Abstract】 In de-stressing and fracturing formation with multi-pulse gas loading,the pressure gradient of deflagration gas along cracks affects crack initiation and extension.The overlay principle is used to resolve complicated loads of borehole wall into simple ones;based on elastic mechanics and linear elastic fracture mechanics,a function describing gas pressure distribution along the crack is proposed to derive the corresponding stress strength of crack top;and then the conditions of crack initiation in borehole rocks are concluded.The conditions reflect the influence of gas pressure gradient varying with time on fracture geometry.The example analysis and field contrast test reveal that,compared with the common High Energy Gas Fracturing,the multi-pulse gas loading fracturing gives rise to higher crack initiation pressure,lower crack arrest pressure,greater extension of fracturing time,and forms 2-3 times fracture length in the formation.Combined with hydraulic fracturing,it can lower formation breakdown pressure and further improves formation permeability.更多还原