This paper presents a sand productionmodel that predictsthe stability of wellbores and perforation tunnels, as well as the mass of sand produced. Past analytical, numerical, and empirical models on material failure and erosion mechanisms were analyzed. The sand production model incorporates shear and tensile failure mechanisms. A criterion for sand erosion in failed sand was proposed based on a force-balance calculation on the sand face. It is shown that failure, post-failure sand mechanics, and flow-dominated erosion mechanisms are important in the sand production process. The model has a small number of required input parameters that can be directly measured in the laboratory and does not require the use of empirical correlations for determining sand erosion. The model was implemented in a numerical simulator. Experiments using different materials were simulated, and the results were compared to test the model. The model-generated results successfully matched the sand production profiles in experiments. When the post-failure behavior of materials was well-known, the match between the simulation and experiment was excellent. Sensitivity studies on the effect of mechanical stresses, flow rates, cohesion, and permeability showed qualitative agreement with experimental observations. In addition, the effect of two-phase flow was presented to emphasize the importance of the water-weakening of the sand. These results showed that catastrophic sand production occurs following water breakthrough.