注液方式对深层页岩裂缝形态影响实验研究

开发深层页岩需要通过对储层进行水力压裂,而注液方式会对压裂效果产生很大的影响。采用真三轴水力压裂实验系统,研究不同的注液方式对深层页岩的裂缝形态的影响规律。实验结果表明:高地应力差下水力裂缝会沿着垂直于最小地应力方向起裂并扩展成横切缝,遇层理或天然裂缝会沟通并形成分支缝;采用先小排量后提升至大排量的注液方式可以开启更多的裂缝;先注入高粘度的压裂液制造主缝,然后替换为低粘度压裂液开启分支缝,形成主缝+分支缝的裂缝形态,有利于提升储层SRV。本实验研究结果可以为深层页岩压裂设计提供参考。

Experiments Research on the Influence of Injection Method on Hydraulic Fracture Morphology of Deep Shale

Hydraulic fracturing is always used to reform deep shale reservoir, while injection method has a great influence on the fracturing results. The hydraulic fracturing experiments under true triaxial conditions are conducted on the deep shale to research the influence of different injection methods on the fracture morphology. The results indicate that the hydraulic fractures always crack in the direction perpendicular to minor principal stress and extend, then penetrate or connect when encounter bedding planes and natural fractures; the injection method that low displacement is first used then high is instead can open more fractures; Injecting high viscosity fracturing fluid could firstly manufacturing main fractures and then with low viscosity fluid could open branch fractures. It is a better method to improve the SRV of shale reservoir. The research can provide a reference for deep shale fracturing design.