Interwell Tracer Analyses of a Hydraulically Fractured Granitic Geothermal Reservoir

Abstract

Field experiments with fluorescent dye and radioactive tracers (Br82 and I131) have been employed to characterize a hot, low-matrix-permeability, hydraulically fractured granitic reservoir at depths of 2440 to 2960 m (8,000 to 9,700 ft). Tracer profiles and residence time distributions (RTD's) have been used to estimate sweep efficiencies and fracture volumes and to diagnose normal and pathological flow behavior both in injection and in production wells. The effectiveness of one- and two-dimensional (1- and 2D) theoretical dispersion models using single and multiple porous, fractured zones with velocity- and formation-dependent effects is discussed with respect to actual field data.