A coupled reservoir/geomechanics model was developed to simulate enhanced production phenomena in conventional and heavy-oil reservoirs. The model was developed and implemented by fully coupling an extended geomechanics model to a two-phase-reservoir-flow model. The effect of solids production on oil recovery was analyzed. Data from approximately 40 wells were used to validate the model for cumulative sand and oil production. Studies indicate that enhanced production is caused by reservoir-porosity and -permeability improvement after a large amount of sand is produced and by higher fluid mobility caused by movement of the sand particles.