压裂液黏度对水力压裂破裂压力及破裂形态的影响

Influence of Fracturing Fluid Viscosity on Breakdown Pressure and Fracture Morphology of Hydraulic Fracturing

随着非常规油气开发需求的增加,水力压裂技术作为油气增产的关键技术受到广泛关注。根据现场压裂结果显示,压裂液黏度作为易于调整的工程参数会对储层改造效率造成重大影响。为了探究压裂液黏度对水力压裂效率的影响,系统开展了不同压裂液黏度作用下砂岩室内水力压裂试验,揭示了压裂液黏度对水力压裂破裂压力、破坏形态的影响及内在机理。试验结果表明:低黏度压裂液将产生两翼平直窄裂缝,高黏度压裂液将形成单翼宽裂缝或分支裂缝。随着压裂液黏度升高,水力压裂过程中由于滤失产生的孔隙压力减小,破裂压力升高。通过试验结果得到了考虑压裂液黏度的计算式,对水力压裂参数设计具有指导意义。

With the increasing demand for unconventional oil and gas development,hydraulic fracturing technology has attracted widespread attention as a critical technology for oil and gas production.According to the field fracturing results,fracturing fluid viscosity,as an easily adjusted engineering parameter,will significantly influence hydraulic fracturing results.In order to explore the influence of fracturing fluid viscosity on hydraulic fracturing efficiency,laboratory hydraulic fracturing tests of sandstone under different fracturing fluid viscosity were carried out systematically,revealing the influence of fracturing fluid viscosity on breakdown pressure and failure mode and its internal mechanism.The test results show that pumping low viscosity fracturing fluid will produce two-wings straight narrow fractures.Pumping high viscosity fracturing fluid will form a single wing wide fracture or branch fracture.As the fracturing fluid viscosity increases,the hydraulic fracturing process results in lower pore pressure due to penetration and higher breakdown pressure.A formula considering the viscosity of fracturing fluid was obtained from the test results.The research has guiding significance for hydraulic fracturing parameter design.