有限元分析径向水力压裂裂缝扩展影响因素

Finite-element analysis on influencing factors for propagation of fractures induced in radial jet hydraulic fracturing

径向水射流辅助压裂的裂缝起裂和扩展机理尚不明确,基于ABAQUS平台,采用扩展有限元法对径向井水力压裂过程中裂缝的扩展过程进行数值模拟,探索径向井方位角、井径、井长、水平地应力差、岩石杨氏模量、岩石泊松比、储层渗透率、压裂液黏度、排量等9个因素对径向井引导裂缝扩展效果的影响规律,并利用灰色关联分析法研究各因素对径向井引导效果的影响能力大小。结果表明,随井径、井长、岩石泊松比等参数增大,径向井对裂缝引导效果增强;随径向井方位角、水平地应力差值等参数增大,径向井对裂缝引导效果减弱。各因素影响径向井对裂缝引导效果的程度由大至小顺序为:水平地应力差值、径向井方位角、井径、岩石泊松比、压裂液排量、储层渗透率、井长、压裂液黏度、岩石杨氏模量。该分析为径向井辅助压裂技术在低渗油藏的应用具有指导意义。

The initiation and propagation mechanism of fractures induced in radial jet fracturing（ RJF） is unknown. In this paper,numerical simulation was performed for propagation of RJF fractures by using the extended finite element method on the ABAQUS platform to highlight the impacts of 9 factors,i.e. radial well azimuth,borehole diameter,well length,horizontal differential geostress,Young modulus,Poisson＇s ratio,reservoir permeability,fracturing fluid viscosity and flow rate,on the propagation of the hydraulic fractures.Moreover,the grey relational analysis was conducted to diagnose how the factors affect the propagation of RJF fractures. The study results show that the propagation capacity of RJF fractures enhances with the increase in borehole diameter,well length,and Poisson＇s ratio,but reduces with the increase in radial well azimuth,horizontal differential geostress and other factors. In view of the impacts,these factors present a descending order of horizontal differential geostress,radial well azimuth,borehole diameter,Poisson＇s ratio,fracturing fluid flow rate,reservoir permeability,well length,fracturing fluid viscosity,and Young modulus. The results provide necessary guidance for application of radial jet fracturing in low-permeability oil reservoirs.