Radon transectanalysis involves short-term a geothermal reservoir to examine structural and of the reservoir . In the sestudies , two natural sampling of wells across thermodynamic proper ties gaseous components of the produced geofluids are measured: (1) the radioactive isotope, radon-222 which decays upon release from the host rock with a half - life of 3.83 days; and (2) the non-radioactive compound ammonia, which appears to be produced continuously in geothermal fluids. The information sought in these studies include data on the spacial and temporal behavior of the geofluids in relation to the structural and thermodynamic conditions in the reservoir . Factors that can effect the relative composition of these two natural components include their relative solubilities , partitioning functions under cycles of brine evaporation and condensation, radioactive decay (radon only), and chemical reactions (ammonia only).

The use of radon as an internal tracer of geofluid transport has been well documented (e.g., Stoker and Kruger, 1975; D'Amore and Sabroux, 1976). Kruger, Stoker, and LJmasa (1977) noted the large difference in radon concentration between liquid and vapor-dominated geothermal reservoir s as well as significant variations between neighboring wells in one formation and temporally within a single well . Models of the relationships between radon concentration and flowrate have been described (e.g., Stoker and Kruger, 1975; D'Amore and Sabroux, 1976; Warren and Kruger, 1979). These models considered linear, radial, and conical flow geometry with radon release from uniformly deposited radium in the host rock flowing with the brines or steam through are servoir of uniform properties . In the conical model of Warren and Kruger (1979), radon in vapor-dominated geothermal reservoir s is assumed to boil out with steam production at a boiling front in the reservoir , with radon decay during transport through the steam reservoir to the well plus an accumulation of radon from the reservoir rock along the transport path. Thus the radon concentration at the wellhead is dependent on a number of parameters describing the release and transport of the radon with the geofluids.

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