Hydromechanical Modeling of Nonplanar Three-Dimensional Fracture Propagation Using an Iteratively Coupled Approach

Accurate numerical modeling of fracture propagation and deflection in porous media is important in the development of georesources. To this end, we propose a novel modeling framework to simulate nonplanar three-dimensional fracture growth within poroelastic media, using an iteratively coupled approach based on time-/scale-dependent fracture stiffness. In this approach, the propagating fractures are explicitly tracked and fitted at each growth step using triangular elements that are independent of the matrix discretized by hexahedral grids. The finite volume/finite element method is employed to solve the hydromechanical system, based on the embedded discrete fracture model. The calculated pressure in fractures and the stress state of the host grid of the embedded fractures constitute the boundary conditions for the boundary element method. The boundary element method module, in turn, renders the evolving fracture stiffness and aperture for the finite volume/finite element method module. Finally, the total stresses and the fracture tip displacements are computed at the end of each time step to estimate the velocity and direction of newly created fractures ahead of the fracture tip. The proposed model is first validated against analytical solutions. Then, in three different examples, results are shown from the fracture's footprint under layered stress conditions, simultaneous propagation of two nonplanar three-dimensional fractures, and the mechanical interaction of en échelon arrays. This work presents an efficient framework to simulate propagation of nonplanar fractures and establishes the foundation to build an integrated simulator for fracture propagation, proppant transport, and production forecasting in unconventional formations.