The combined effect of stress, fluid flow, and reservoir property changes on oil recovery were evaluated by a fully coupled procedure that integrates geomechanics and reservoir simulation. In this development, we pay particular attention to changes in oil recovery caused by reservoir compaction (the so-called compaction drive mechanism) and to the impact of the constitutive behavior of rock deformation on oil recovery. In general, for weak hydrocarbon reservoirs that exhibit nonlinear, elastic and plastic constitutive behavior, the coupling effect may not be ignored in reservoir simulation. The coupled interaction between geomechanics and reservoir fluid production significantly affects the stress state, reservoir properties, and the efficiency of oil recovery. Both fully and loosely coupled methods are used to illustrate the impact of reservoir compaction on oil recovery. The key variables investigated, that are important in improving oil recovery by the compaction drive mechanism, include the constitutive behavior of reservoir rock, the water-weakening effect, stress-dependent permeability, and the overburden/reservoir interaction. The numerical results from this study show that a fully coupled geomechanics and reservoir simulation approach can be used to accurately quantify the economic impact of compaction drive, and the coupled numerical procedure employed in this paper provides such a tool. A comparison between the fully and loosely coupled models is given.