Exploitation of The Geysers began about 140 years ago with the construction of a resort hotel. Electric generation commenced in the 1920s upon the completion of several shallow steam wells. A steam engine-driven generator supplied roughly a kilowatt to electrify the resort through the 1930s. The current large-scale development began with drilling in 1955 and the first 12 MW plant in 1960. Additions in the 1960s brought field capacity to 82 MW. The sustained development started in 1971, with an average of 67 MW/year installed through 1981. Growth accelerated to 150 MW/year in the latest phase (1982-89). This latest phase of expansion has been accompanied by 100-200 percent increases in reservoir pressure and production decline rates. Steam deliverability fieldwide has peaked, and substantial declines have been experienced. The reservoir response indicates the field is fully developed. Performance forecasts have been made using both numerical models and direct extrapolation of pressure and flow rate trends. Both methods suggest that field life will exceed 50 years. However, Unocal-NEC-Thermal production will probably decline from 16 million lb/hr (7,273 t/h) to 8 million lb/hr (3,636 t/h) in the next 10 years