Comparison of discrete and equivalent continuum approaches to simulate the mechanical behavior of jointed rock masses

Modeling of rock masses is of major importance to assess the Geomechanical behaviour of oil & gas reservoirs, especially for fractured tight reservoirs. The presence of discontinuities will significantly influence the general behavior of the rock masses, in particular introducing strength reduction, enhanced/reduction permeability, anisotropic behavior and a non-linear response. In the present study, Discrete and Equivalent continuum approaches have been used to simulate the mechanical behavior of jointed rock masses. Discrete approach uses the eXtended Finite Element Method (XFEM) and the Zero-thickness interface elements, while the Equivalent continuum approaches uses an elastic-viscoplastic constitutive model of the multilaminate type to represent the rock mass behavior. Advantages and limitations of each approach are identified and some hints for their practical use are given. Although the discrete approach is sometimes preferred for being based on a mature theory, the equivalent continuum analysis seems to be more often applicable for usual geomechanical analyses from engineering practice.