INTERPRETATION OF GEOPHYSICAL DATA FOR THE VALE, OREGON GEOTHERMAL SYSTEM
Ken W. Wisian and David D. Blackwell
Southern Methodists University, Dallas, Texas
Bill Teplow and Tsvi Meidev
Trans-Pacific Geothermal Co.
Geothermal Resource Council Transactions, v. 20, p. 435-438, 1996.
The Vale, Oregon geothermal system is located on the western edge of the Snake River Plain. The Vale hot springs discharge 164°F (73°C) water at about 20 gpm into the Malheur River. The surface heat flow anomaly is about 8.5 miles (13.5 km) long by 2 miles (3 km) wide, as defined by the 7°F/100feet (127°C/km) temperature gradient contour, and has a conductive heat output on the order of >10 MW. Maximum observed subsurface temperatures are approximately 290°F (143°C), close to the estimated geochemical reservoir temperature of about 320°F (160°C). Data from 54 shallow temperature gradient holes, several existing deep wells, one new deep well, and geophysical surveys, were used to construct a conceptual model of the geothermal system. The temperature gradient anomaly correlates very well with a gravity high and a small topography high, suggesting a buried horst block, volcanic center or other elevated structure. The geothermal system appears to be structurally controlled with upflow in a buried structure, or along the faults, with perhaps some shallow lateral flow driven by local topography.