压裂液对油页岩裂缝扩展影响的数值模拟

Numerical Simulation on the Effect of Fracturing Fluid Onoil Shale Fracture Propagation

压裂液在油页岩水力压裂裂缝扩展过程中扮演着重要的角色,因此获得压裂液对油页岩水力压裂裂缝扩展的影响规律对油页岩水力压裂技术的发展有着巨大的推动作用。选取羟丙基胍胶稠化剂配制成了不同含量的压裂液基液,并测量了其黏度。然后,基于扩展有限元方法(extended finite element method,XFEM)裂缝扩展分析方法和压裂液对油页岩裂缝扩展的影响模型,采用ABAQUS数值模拟软件,对吉林省汪清地区的油页岩进行了不同黏度和不同排量压裂液条件下的裂缝扩展仿真模拟。分析模拟结果发现,水力压裂裂缝在油页岩中扩展时,压裂液排量是影响裂缝扩展的主要因素,而压裂液黏度对油页岩裂缝扩展的影响很小;随着压裂液排量的增加,裂缝的长度和宽度迅速增大,其扩展速率亦随排量增加而增大;到水力压裂后期,裂缝长度和宽度逐渐趋于常值,即压裂液对裂缝扩展的影响逐渐变小。

Fracturing fluid plays an important role in the process of fracture propagation in oil shale hydraulic fracturing.Therefore,it has a great impetus to the development of hydraulic fracturing technology of oil shale to obtain the influence law of fracturing fluid on hydraulic fracturing fracture propagation of oil shale.Hydroxypropyl guanidine gel thickener was selected to prepare fracturing fluid-based fluids with different content,and its viscosity was measured.Then,based on(extended finite element method,XFEM)fracture propagation analysis method and the influence model of fracturing fluid on oil shale fracture propagation,ABAQUS numerical simulation software was used to simulate fracture propagation of Wangqing oil shale in Jilin Province under different viscosity and different displacement fracturing fluid.The analysis of simulation results show that the displacement of fracturing fluid is the main factor affecting fracture propagation when hydraulic fracturing fracture expands in oil shale,while the viscosity of fracturing fluid has little effect on fracture propagation of oil shale;with the increase of fracturing fluid displacement,the length and width of fracture increase rapidly,and the growth rate increases with the increase of displacement.At the later stage of hydraulic fracturing,the length and width of fracture gradually tend to be constant,that is,the influence of fracturing fluid on fracture propagation gradually becomes smaller.