水力喷射压裂中环空水力封隔全尺寸实验

Field-scale testing of hydraulic isolation in wellbore during hydra-jet fracturing

多级水力喷射压裂技术依靠水力封隔实现层段间隔离。通过地面全尺寸实验,提出从环空压力变化的角度评估水力封隔效率。实验中对喷射速度、围压、喷嘴直径和射孔入口直径以及环空注液对水力封隔效率的影响进行测试。实验结果表明:射流速度和围压是影响环空压力降低的两个主要因素,环空压力降低的幅度与射流速度呈线性增长关系,与围压呈指数递减关系;水力封隔效率与射流动能和孔道入口直径的比值成正比,可通过增大喷嘴直径和减小孔道入口直径的方法提高水力封隔能力;环空注液降低水力封隔效率。

Hydraulic isolation can be used to isolate the wellbore sections during multiple hydra-jet fracturing. A field-scale testing on the hydraulic isolation was conducted to evaluate its isolation efficiency based on annulus pressure measurement. In the testing,the effects of jet velocity,ambient pressure,diameter of nozzle and perforation inlet,and annulus injection on isolation efficiency were investigated. The results show that the jet velocity and ambient pressure are the two key parameters to affect the annulus pressure drop-down,and it has a linear relationship with the jet velocity and an exponential relationship with the ambient pressure. In addition,the hydraulic isolation efficiency is directly proportional to the ratio of kinetic energy of the jet to the diameter of perforation inlet. Therefore,the isolation efficiency can be improved by enlarging the nozzle diameter or reducing the perforation inlet diameter,while the annulus injection can reduce the hydraulic isolation efficiency.