Virtual element method for geomechanical simulations of reservoir models

In this paper, we study the use of virtual element method (VEM) for geomechanics. Our emphasis is on applications to reservoir simulations. The physical processes behind the formation of the reservoirs, such as sedimentation, erosion, and faulting, lead to complex geometrical structures. A minimal representation, with respect to the physical parameters of the system, then naturally leads to general polyhedral grids. Numerical methods which can directly handle this representation will be highly favorable, in particular in the setting of advanced work-flows. The virtual element method is a promising candidate to solve the linear elasticity equations on such models. In this paper, we investigate some of the limits of the VEM method when used on reservoir models. First, we demonstrate that care must be taken to make the method robust for highly elongated cells, which is common in these applications, and show the importance of calculating forces in terms of traction on the boundary of the elements for elongated distorted cells. Second, we study the effect of triangulations on the surfaces of curved faces, which also naturally occur in subsurface models. We also demonstrate how a more stable stabilization term for reservoir application can be derived.