Abstract
In order to make a better understanding of the hydraulic fracturing in transversely isotropic rock masses, the modified particle flow modeling method was used by embedding the smooth joint models within an area of certain thickness, and the optimized fluid-mechanical coupling mechanism was applied in hydraulic fracturing modeling. On this basis, the influence of the injection rates, in-situ stress ratios and inclination angles of the bedding planes on the breakdown pressure and propagation of the hydraulic fractures was analyzed. The simulation indicated that: 1) Excessive small or large injection rates would lead to the increase of the breakdown pressure of the hydraulic fractures. 2) Under different inclination angles of the bedding planes, the crack breakdown pressure increased linearly with the increasing of the in-situ stress ratios. And under conditions of different in-situ stress ratios, the crack breakdown pressure changed as a ‘wave’ type with the increasing inclination angles of bedding planes. 3) Both the in-situ stress ratios and the inclination angle of bedding planes affected the propagation of the hydraulic fractures. The existence of the bedding planes would induce the hydraulic fractures to propagate along the bedding planes. The large inclinations of the bedding planes would cause the hydraulic fractures to keep propagating with the direction of maximum principal stress.
Highlights
In recent years, with the success of the shale gas revolution in the United States, the unconventional oil and gas resources have been developed efficiently and economically
Under conditions of different in-situ stress ratios, the crack breakdown pressure changed as a ‘wave’ type with the increasing inclination angles of bedding planes
Sergey Stanchits et al [3] used acoustic emission technology to monitor the fracture position during the fracturing process, and obtain the relationship between the hydraulic fractures and the natural fractures under the different injection rate and fluid dynamic viscosity
Summary
With the success of the shale gas revolution in the United States, the unconventional oil and gas resources have been developed efficiently and economically. McClure [5] used two-dimensional displacement discontinuous method (DDM) to study the propagation of hydraulic fractures in rock reservoirs with natural discrete fracture networks. Hanyi Wang [7] established a fully coupled non-planar hydraulic propagation model using the XFEM (Extended Finite Element Method) to study the initiation and propagation of hydraulic fractures in brittle and ductile rock masses. Based on the mechanism of the fluid-mechanical coupling in PFC, the crack initiation and propagation of hydraulic fractures in transversely isotropic rock masses were studied
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