1. A method of generating a simulator production and reserves forecast, a mechanism representing a process that is active in a reservoir being chosen in response to a first development plan for developing a reservoir, comprising the step of: (a) in response to a history calibrated model, an implementation plan of said mechanism, and a set of constraints, executing a simulator production and reserves forecast model and, responsive thereto, generating a simulator production and reserves forecast representing a manner by which said reservoir responds to said first development plan, wherein said set of constraints is selected from a group consisting of: production objectives, sales and transport constraints, rig and equipment availability, injectant constraints, processing constraints, well capacity constraints, and proposed plan of development.