GDA Steamboat Power Plant: A Case History

G. Martin Booth, III

Located 10 mi south of Reno, Nevada, Steamboat Springs has long been recognized as a prime geothermal resource for electric power generation potential by the U.S. Geological Survey and numerous energy companies. Extensive leasing and exploration by Phillips and Gulf led to the discovery of a high-temperature (over 400°F) reservoir in 1979.

Geothermal Development Associates obtained a geothermal resources lease on a 30-acre parcel and a 10-year power sales agreement for 5 MW from the local utility, Sierra Pacific Power Company, in late 1983. Drilling commenced in March 1985, modular power plant construction began in October, and initial plant startup with power to the grid was accomplished in December 1985. Owing to cooling-water access and treatment costs, air-cooled condensers replaced the planned cooling towers, and full-time scale continuous production at rated capacity did not begin until late 1986.

Three production wells and two injection wells, completed in highly fractured Cretaceous granodiorite and Tertiary andesite at depths of less than 1,000 ft, produce 340°F water having a salinity of 2,300 ppm. Production well line-shaft pumps deliver in excess of 3,000 gpm water to seven 1.2 MW-Rankine cycle binary power plant modules. The heat extracted from the geothermal water vaporizes the low boiling point N-pentane working fluid that expands to drive the turbines. The geothermal water is injected back into the reservoir. Both the pentane and the geothermal water are in separate closed-loop systems, which provides for an environmentally clean operation in this sensitive, highly visible site on the periphery of a metropolitan area.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.