Interwell Tracer Analyses of a Hydraulically Fractured Granitic Geothermal Reservoir
Journal Article: Interwell Tracer Analyses of a Hydraulically Fractured Granitic Geothermal Reservoir
AbstractRadioisotopic tracer techniques using I/sup 131/ and Br/sup 82/ with downhole gamma logging have been used successfully at temperatures up to 200/sup 0/C (392/sup 0/F) and depths to 3 km (10,000 ft) to characterize quantitatively flow at injection and production points in hydraulically fractured regions in granite, including mapping of fracture intersections with wellbores. RTD techniques using sodium fluorescein and Br/sup 82/ tracers were developed to estimate overall fracture volumes, overall levels of dispersed mixing, and individual flow path characteristics. Observed levels of mixing are much higher than would be expected for purely hydrodynamic dispersion in nearly potential or steady laminar flow in a flat fracture between injection and production wells. Variable residence times caused by a complex distribution of crack apertures may control the overall RTD in a completely convectively dominated system. Geophysical, geometric, and flow data and 1- and 2D dispersion analyses were combined to develop plausible reservoir models for hydraulically fractured HDR systems. Models developed are consistent with major observations from extensive field tests including estimates of effective heat transfer area, thermal drawdown and recovery temperature logs, flow impedances, and reservoir geochemistry. Because of the complex relationship between geometric factors (fracture roughness, primary and secondary flow paths through propped joints, dead-end pore volume and other stagnation regions) and the physical phenomena controlling convective circulation and dispersion, a unique model to describe flow and mixing cannot be determined.
- Jefferson W. Tester, R. L. Bivins and R. M. Potter
- Published Journal
- Society of Petroleum Engineers, 1982
- Not Provided
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Jefferson W. Tester,R. L. Bivins,R. M. Potter. 1982. Interwell Tracer Analyses of a Hydraulically Fractured Granitic Geothermal Reservoir. Society of Petroleum Engineers. 22:537-554.