Well, Hydrology, and Geochemistry Problems Encountered in ATES Systems and Their Solutions

In aquifer thermal energy storage (ATES) systems, wells provide the interface between the energy storage and use. Efficient operational wells are, therefore, essential for the system to run at maximum (design) efficiency. Adequate test drilling to accurately predict aquifer properties is essential in the design phase; proper construction and development are crucial; and proper monitoring of performance is necessary to identify the early stages of clogging and to evaluate the adequacy of well rehabilitation. Problems related to hydrology, well, and aquifer properties include 1) loss of permeability resulting from gas exsolution, chemical precipitation, and dispersion and movement of fine-grained particles; 2) loss of recoverable heat caused by excessive regional ground-water gradient, hydrodynamic mixing of injected and native ground water, buoyancy flow (because of temperature-induced differences in water density); 3) leakage up along the well casing; and 4) “fracturing” of a shallow upper aquiclude as a result of an injection pressure greater than the hydrostatic pressure on the aquiclude.