Injecting geothermal fluids back into the reservoir is essential to maintaining the electrical production from geothermal systems. Proper injection-well location leads to increased power production due to enhanced pressures and reduced thermal breakthrough. Introduction of tracers into the injection-production loops is the fastest and most effective method of obtaining data that reveal the flow patterns of injected fluids.

The primary objective of our research efforts at EGI is to identify and test candidate compounds for use as tracers in geothermal reservoirs. An ideal tracer is nontoxic, environmentally benign, thermally stable (or possessing a quantifiable and reasonably slow rate of decay under geothermal conditions), detectable at very low concentrations, non-reactive with the reservoir rock and relatively inexpensive. As many of these compounds as possible should be identified because of the need for identifying individual injector/producer flow paths in reservoirs containing multiple injection wells.

At the inception of the DOE tracer development program in 1982, there were very few tracers in use by the geothermal industry. Since then, we have studied nearly a hundred candidate tracers, and all of those currently in use by the geothermal industry were developed or studied at EGI. Whereas most of the geothermal tracers that we have developed partition exclusively to the condensed (liquid) phase, a major emphasis of our program has also been the development of vapor-phase tracers to accommodate the growing need for tracers that will follow steam.

A potentially important spin-off from the liquid-phase tracer research has been the discovery that these compounds appear to serve very well as groundwater tracers.