Sensitivity of a Reactive-Tracer Based Estimate of Thermal Breakthrough in an EGS to Properties of the Reservoir and Tracer

Abstract

Reactive tracers have long been considered a possible means of measuring thermal drawdown in a geothermal system before significant cooling occurs at the extraction well. In this study, we examine the sensitivity of successive reactive tracer tests to reservoir cooling. Results indicate that while the sensitivity of the method as generally proposed is low, it may be sufficient to provide valuable information about the thermal evolution of the reservoir. We propose several modifications to the basic flow-through method that could provide increased sensitivity, including push-pull tracer tests at the injection well and utilization of a tracer reaction that is quenched before background reservoir temperature is reached. While preliminary numerical modeling tests of these methods demonstrate similar sensitivity to the basic inter-well test, additional sensitivity tests of the sensitivity of these methods are needed.