Safe disposal of thermally spent geothermal brines that contain enviro
nmentally hazardous constituents is commonly obtained by reinjection.
The reinjection process also serves to maintain reservoir pressure, en
hance thermal recovery, and eliminate possible compactional subsidence
. To avoid premature thermal breakthrough of reinjected fluids, tracer
tests are employed for detection and evaluation of preferential path
networks. In this paper some promising tracers that have not received
much attention in geothermal reservoir studies are discussed, and a co
mprehensive tabulation of field sites of artificial tracer utilization
is presented. Chemical and transport processes responsible for tracer
retention by the formation of reservoir solids, as well as available
tracer detection techniques, are emphasized.