Approximation of Geothermal Reservoir Characteristics Based on Gravimetry

Abstract

A close correspondence between heat flow anomalies and residual gravity anomalies has been observed in several geothermal fields. particularly in the Imperial Valley of California. This correspondence provides evidence that the residual gravity anomaly is due to of the supra-basement sediments as a result of mineral deposition by convecting geothermal fluids. Based on this correlation, the total amount of fluid that has circulated in the geothermal system can be determined. Dissolved minerals from the geothermal fluid are precipitated as the tluid convects from deeper, high-temperature. high-pressure zones within the reservoir to shallower, low-temperature, low-pressure zones. Analysis ofthe residual gravity anomaly associated with the convecting system is used to provide the total mass of hydrothermally precipitated minerals. By utilizing of mass loss unit volume of fluid with the total excess mass calculated from gravimetry, the total fluid and thcrmal energy throughput of the gcothermal system over its active lifetime is calculated. Alternatively, the convection rate of the hydrothernial system can be calculated using heat flow and reservoir engineering methods. The derived from gravimetry is then used together with the calculatcd convection rate to determine the age the hydrothermal system.