Commercial exploitation of the Northwest Geysers began in early 1988. To date, little has been published about the connectivity of this area to the rest of the geothermal field, the interaction between the so-called ＇＇typical＇＇ reservoir and the underlying high-temperature zone, or the combined potential of both producing horizons. To investigate these issues, a dual-porosity numerical model of The Geysers geothermal system with special emphasis to the NW Geysers was developed. The model was calibrated using production data from 1957 to early 1991. Simulation results and the measured data suggest that: the typical reservoir in NW Geysers is connected to the rest of the field; significant migration of fluids from this part of the reservoir to the rest of The Geysers has occurred; and there still are some undeveloped areas in the NW Geysers with production potential. The production/injection scenarios analyzed with the model suggest that the existing wells are not sufficient to sustain a 60 MWe operation for 30 years starting in 1991, However, the addition of new wells within the licensed boundaries of the Coldwater Creek steamfield, drilled over a period of years, could sustain the steam production required to generate 60 MWe for 30 years. A 130 MWe development is not feasible within the mid-1993 licensed boundaries.