Effect of Layering in the Simultaneous Propagation of Fluid-Driven Fractures: A Coupled Hydro-Mechanical Model Using the Extended Finite Element Method

Optimal design of fluid-driven fracture networks to decrease the environmental impact of hydraulic fracturing operations requires a thorough understanding of the interaction between fluid-driven fractures and heterogeneous geomaterials from both numerical and operational standpoints. Although the effect of layered geomaterials in single fluid-driven fractures has been thoroughly discussed in previous studies, their effect on multiple simultaneous fractures is not well understood. In this study, the effect of the layered media, fracture intervals, injection rate and viscosity of the fracturing fluid on the behavior of simultaneous fluid-driven fractures was investigated using a coupled 2D hydro-mechanical extended finite element method. Fluid flow was modeled by lubrication theory and was coupled with rock deformations while it was assumed no fluid leakoff from the fractures’ surfaces. The results illustrate disturbance in the stress field in the multi-layered media. It was observed that the propagating fractures tend to deviate towards the layer with lower elastic modulus due to lower resistance against their propagation. This deviation is a function of the contrast between the elastic moduli of the layers. Also, it was observed that an increase in the spacing between fractures would result in a decrease in their deviation, which appears to be caused by a reduction in the stress shadowing effect. Furthermore, an increase in both injection rate and fluid viscosity leads to wider fractures and less digression, which seems to be a result of the greater induced stresses generated by the fluid-driven fracture. In conclusion, The elastic modulus contrast, fracture spacing, injection rate and fluid viscosity significantly affect the stresses induced by the fluid-driven fractures and their geometry in the heterogeneous medium and, therefore, appear to play a critical role in the interaction between fluid-driven fractures.