Tracer Testing At Fenton Hill HDR Geothermal Area (Tester, Et Al., 1982)

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Exploration Activity: Tracer Testing At Fenton Hill HDR Geothermal Area (Tester, Et Al., 1982)

Exploration Activity Details
Location Fenton Hill HDR Geothermal Area
Exploration Technique Tracer Testing
Activity Date 1982 - 1982

Usefulness useful
DOE-funding Unknown

Exploration Basis
Radioisotopic tracer testing techniques were used to quantitatively characterize flow at injection and production points in the hydraulically fractured Phase I reservoir, and to map fracture intersections within the EE-1 and GT-2B wellbores.
I/sup 131/ and Br/sup 82/ radioisotope tracers were successfully used in conjunction with downhole gamma logging at temperatures up to 200/sup o/C and depths to 3 km. Residence Time Distribution (RTD) techniques using Br/sup 82/ and sodium fluorescein tracers were also developed to investigate individual flow path characteristics and to estimate overall fracture volumes and levels of dispersed mixing. The levels of mixing observed were much higher than would be expected for purely hydrodynamic dispersion in nearly potential or steady laminar flow in flat fractures between the injection and production wellbores. Variable residence times of the different radioisotopes was caused by the complex distribution of crack apertures within the reservoir, and suggest that these reservoir features may control the overall RTD in the convectively dominated system. The results of the tracer testing study prompted the development of a methodology for analyzing the internal flow characteristics of a fractured geothermal reservoir using tracer-determined RTD curves (Robinson and Tester, 1984). The methodology emphasizes the comparison of statistical quantities obtained from the tracer curves of different reservoirs or of the same reservoir under different conditions. In this way, empirical reservoir performance correlations may be constructed unambiguously using model-independent information. Fluid flow behavior may be characterized further using downhole measurements of the tracer response exiting from discrete fracture zones in the reservoir.

Additional References