A successful reservoir model that history matches pro-duction data in a mature field requires the integration of mul-tiple disciplines and all available data. The disciplines required are geology, geophysics, petrophysics, rock physics, and reservoir engineering. The data types include, but are certainly not limited to, seismic, well logs, core, PVT, and production data. Of all the data types available, only seismic data measure and image the reservoir over the whole field. It is obvious that seismic data should be used to constrain reservoir models. However, the amount of constraining depends on factors such as data quality, resolution relative to reservoir thickness, sufficient elastic im-pedance contrasts between lith-ologies and fluids, and good well-to-seismic ties.