TRACER TESTING AT STEAMBOAT HILLS, NEVADA, USING FLUORESCEIN AND 1,5-NAPHTHALENE DISULFONATE

Abstract

A tracer test was recently initiated at the Steamboat Hills, Nevada, geothermal system in order to test the performance of the candidate tracer 1,5-naphthalene disulfonate and to evaluate the flow patterns of fluids entering the reservoir through a recently drilled slim hole injector. The tracer fluorescein was used as a companion dye to 1,5-naphthalene disulfonate. Early returns indicate comparable performance for the two tracers with both appearing to behave conservatively. The Arrhenius first-order thermal decay rate of 1,5naphthalene disulfonate was determined over the temperature range of 310-330 o C using a batch autoclave reactor under conditions that simulate a hydrothermal environment. The tracer was found to be remarkably stable with only 20% decay measured after one week in the autoclave at 330 o C. The long linear tailing portion of return curves from a tracer test initiated in 1992 indicates the effective fluid volume at Steamboat Hills to be on the order of 30 million m 3 (8 billion gal). The natural recharge rate was estimated to be about 300 kg/sec (5000 gal/min).