Numerical Simulation of a Tracer Test at Dixie Valley, Nevada

Abstract

A tracer test was conducted at the Dixie Valley, Nevada, geothermal reservoir using fluorescein. Four of 9 production wells showed fluorescein breakthrough during the first 200 days of the test. Reconstructed fluorescein return curves are presented that correct for the thermal decay of the tracer assuming an average reservoir temperature of 227?C. In order to examine the feasibility of using numerical simulation to model tracer flow, we developed simple, two dimensional models of the geothermal reservoir using the numerical simulation programs TETRAD and TOUGH2. By fitting model outputs to measured return curves, we show that numerical reservoir simulations can be calibrated with the tracer data. Both models predict the same order of elution, approximate tracer concentrations, and return curve shapes. Using these results, we propose a method for using numerical models to design a tracer test.