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In recent years considerable interest has been focused on deep saline aquifers as reservoirs for the disposal of liquid waste. In general, the water in such aquifers is already in motion controlled by 3 sets of gradients: the hydraulic-pressure gradient, the geothermal gradient, and the salt concentration gradient. In thick aquifers, interaction of these gradients induces gravity convection currents which are not present in constant-density fluid systems. The fate of the waste liquids entrained in this fluid system will depend (among other things) upon the state of motion in the aquifer before injection and the modification of this state by the injection process.
A hydraulic laboratory sandstone model was built to simulate a saline aquifer, a geothermal source, freshwater recharge, and waste-injection wells. The studies show stream lines, velocities, and temperature/salinity distributions before and during waste injection. The governing equations, namely, the hydraulic flow equation, the diffusion equation for salt and injected contaminants, and the heat diffusion equation are solved simultaneously on a high-speed digital computer. Obtaining theoretical solutions comparable to the model data requires choosing correct empirical values of coefficients of salt and heat diffusion.
After the validity of solutions of the governing equations is established by comparison with the model studies, a basis for prediction is investigated by comparing theoretical solutions for field conditions with temperature and salinity data from selected oil exploratory wells in the Floridan aquifer of southern Florida.
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