Hydrologic properties of the Dixie Valley, Nevada, geothermal reservoir from well-test analyses

摘要

Temperature, pressure, and spinner (TPS) logs have been recorded in several wells from the Dixie Valley Geothermal Reservoir in west central Nevada. A variety of well-test analyses has been performed with these data to quantify the hydrologic properties of this fault-dominated geothermal resource. Four complementary analytical techniques were employed, their individual application depending upon availability and quality of data and validity of scientific assumptions. The methods were (1) step-drawdown, variable- discharge test; (2) recovery analysis; (3) damped-oscillation response; and (4) injection test. To date, TPS logs from five wells have been examined and results fall into two distinct categories. Productive, economically viable wells have permeability-thickness values on the order of 100,000 millidarcy-meter (mD-m) and storativities of about 10 to the -3rd power. Low-productivity wells, sometimes located only a few kilometers from their permeable counterparts, are artesian and display a sharp reduction in permeability- thickness to about 10 mD-m with storativities on the order of 10 to the -4th power. These results demonstrate that the hydrologic characteristics of this liquid-dominated geothermal system exhibit a significant spatial variability along the range-bounding normal fault that forms the predominant aquifer.