An analytical model was used to predict temperature and chemical concentrations that result from the constant injection of cold, hypersaline brine in a hot, deep-seated limestone aquifer. Due to the presence of high concentrations of sulfate and calcium in the brine there is concern that precipitation of anhydrite will occur rendering the aquifer unusable for the planned disposal of the brine that presently contaminates an important surface water supply. The model assumes the aquifer to be a homogeneous, densely fractured system composed of intersecting, highly permeable fractures separated by low-permeability blocks. Based on selected values of aquifer dimensions, and realistic hydraulic, thermal, and chemical properties for the rock and fluid, results show possible locations of the thermal and chemical fronts and/or breakthrough curves. From these results it may be possible, using geochemical modeling, to infer when or where in the aquifer the precipitation of anhydrite is likely to occur and to make recommendations for alleviation of problems related to aquifer plugging.
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