The increasing energy demand calls for advances in technology which translate into more accurate and complex simulations of physical problems. We are trying to understand volumetric rock damage, which is essential to understanding the geomechanics of oil and gas reservoirs. The fragile microstructure of some rocks makes it difficult to predict the propagation of damage and fracture in these rocks, therefore a mathematical model is required to predict the fracture mechanisms in such materials. The governing equation of rock damage is a nonlinear parabolic partial differential equation (PDE). The physics of the problem imposes a number of complexities that should be handled numerically. In this paper, we present the results we obtained using COMSOL 3.5a and we show how a complicated problem can be solved using the finite element method incorporated in COMSOL. The results could be used in similar geomechanical and structural damage problems such as failure and rupture of Steel, Aluminum, Concrete, etc. Moreover, the pattern of rock damage in oil and gas reservoirs is of great significance in recovery of hydrocarbon in petroleum engineering.