SENSITIVITY OF A REACTIVE-TRACER BASED ESTIMATE OF THERMAL BREAKTHROUGH IN AN EGS TO PROPERTIES OF THE RESERVOIR AND TRACER

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. Here, we examine the sensitivity of the proposed method to reservoir cooling and demonstrate that while the sensitivity of the method as generally proposed is low, it may be practical under certain conditions. Our analyses suggest that modifications to that method, where practical, could provide much greater sensitivity. In particular, if the reaction can be quenched before maximum temperature is reached, the sensitivity is greatly enhanced. Push-pull tracer tests conducted at the injection well demonstrate similar advantages. Other alternatives, such as combinations of tracers, and tracers with parallel or chain decay behavior may offer similar advantages