Reservoir engineering (and simulation) have historically paid little attention to the geomechanical behaviour of porous media. However, a number of important (primarily unconventional) recovery processes can be properly engineered only by including this effect (e.g., thermal recovery in oil sands, compaction drive in soft and unconsolidated reservoirs, chalk reservoirs, stress sensitive and microfractured media, waterflooding at fracture pressure, waste injection, coal seam stimulation, etc.). In addition, analysis of drilling and completion problems, such as well:bore stability, sand production, fracturing or casing failure, requires knowledge of geomechanical behaviour of the reservoir. This paper gives an overview of the geomechanics of reservoir behaviour, describes recent advances in coupled reservoir and geomechanical modelling, and presents case studies of field :applications of this new tool. The examples show the potential of the coupled modelling to become a comprehensive tool for integrated reservoir management, including reservoir, production and drilling aspects of field development. In each case, the use of the new, more comprehensive tools provided better,understanding of recovery mechanisms, and changed significantly the economic evaluation of the project.