水力喷射多级压裂中水力封隔效果的数值模拟

Numerical Simulation of Effect of Hydraulic Isolation in Hydraulic Jet Multi-stage Fracturing

在多级压裂过程中有效的层间封隔至关重要,水力喷射压裂技术利用水力射流形成的低压区来实现层段间的封隔,但是在井下复杂环境下很难通过试验来定量分析水力封隔效果。鉴于此,首先建立了包含喷嘴、射孔孔道和环空段等结构的CFD模型,模拟了多级水力喷射压裂过程中环空的特性,并将数值模拟结果与试验数据进行对比,验证了该数值模型的正确性;然后根据环空流动特性,提出了用2个出口的质量流量比来评价多级压裂中水力封隔效果;最后,分析了不同参数对封隔效果的影响规律。模拟结果表明:1在一定条件下,高速射流能产生有效的层间封隔;2水力封隔效果随层间压差、喷射相位角和喷距的减小而增强,随喷射流速和喷射层数的增大而增强,且喷射相位角对水力封隔效果的影响大于喷射层数的影响。研究结果可为多级水力喷射压裂水力参数、喷嘴布置和参数组合的优化提供参考。

Effective interzonal isolation is technology utilizes the low pressure area formed critical during multi-stage fracturing. The hydraulic jet fracturing by hydraulic jet to provide isolation between intervals. Within corn- plex downhole environment, however, it is very hard to use tests to quantitatively analyze the effect of hydraulic isolation. For this reason, a CFD model consisting of structures such as nozzles, perforation channels and annulus sections is built firstly, and the numerical simulation result are compared with test data and the validity of this numerical model is verified ; then, based on annular flow characteristics, it is suggested that the mass flow ratio of 2 outlets be used to evaluate the effect of hydraulic isolation in multi-stage fracturing; finally, the rule of impact of different parameters on the isolation effect is analyzed. The simulation result indicates that：①under certain conditions, high-speed jet can produce effective interzonal isolation ; ②the effect of hydraulic isolation increases as interzonal pressure difference, jet phase angle and jet distance decrease and as jet flow velocity and jet interval count increase, and the impact of jet phase angle on the effect of hydraulic isolation is greater than that of jet interval count. The study result can provide reference for optimizing hydraulic parameters, nozzle arrangement and parameter combinations of multi-stage hydraulic jet fracturing.