Maximum temperatures found in the reservoir were approximately 700°F in the Imperial Valley, California, but drill bit temperatures may be considerably higher in the Geysers geothermal area. Temperatures reached up to 900°F because of frictional heating and possibly inefficient cooling. Rock types found in the high temperature environments range from hard abrasive granites and metamorphosed sandstones to unconsolidated sediments and friable sandstones. The rocks are highly fractured at reservoir depths