Use of time-lapse or 4D-seismic monitoring can improve reservoir understanding and, consequently, ultimate recovery. However, 4D-seismic monitoring is not applicable to all reservoirs or all development strategies. A strong 4D-seismic monitoring candidate must have favorable geophysical rock properties and a development plan that encourages observable changes in repeat 3D-seismic surveys. A traditional now simulator that includes a petrophysical model can predict dynamic reservoir changes and the resulting changes in seismic response. This interdisciplinary approach to reservoir modeling blurs the distinction between geophysics and reservoir engineering.