The Dixie Valley, Nevada Tracer Test

Abstract

Three injection wells in the Dixie Valley, Nevada geothermal field were tagged with organic tracers. The tracers used were benzoic acid, benzenesulfonic acid, 4 ethylbenzenesulfonic acid and flourescein. Six production wells were intensively sampled for 2.5 moths. During this period one well, 76-7, showed breakthrough. The presence of benzoic acid and fluorscein in the 76-7 production fluid demonstrated that breakthrough was from well 32-18. Concentration ratios of these compounds varied during the test period, as predicted from laboratory experiments. These ratios predict an average flow path temperature of 230°C for eh early time data and a range from 218°C to 232°C for the later data. These temperatures are consistent with the observed temperatures in the reservoir. A numerical reservoir model of the Dixie Valley field was employed to predict the results of the tracer testes. The model as used to estimate needed tracer quantities and sampling frequencies. The results of the model are in qualitative agreement with the observed arrival tracer breakthrough. Difference between calculated and observed arrival times may be due to the larges mesh size used in the model and a possible under estimate of the average fracture porosity.