Aquifer thermal energy storage: An attempt to counter free thermal convection

In previous Aquifer Thermal Energy Storage (ATES) experiments, appreciable free thermal convection was observed. In an attempt to counter the detrimental effects of convection, a dual recovery well system was constructed at the Mobile site and a third injection‐storage‐recovery cycle performed. Using a partially penetrating well, cycle 3‐3 injection began on April 7, 1982. A total of 56,680 m 3 of 79°C water were injected. After 57 days of storage, production began with a dual recovery well system. Due to the dominating effect of nonhomogeneities, the dual well system did not work particularly well, and a recovery factor of 0.42 was achieved. The degree of aquifer heterogeneity at the location of the present experiments was not apparent during previous experiments at a location only 109 m away, although pumping tests indicated similar values of transmissivity. Therefore aquifers with the same transmissivity can behave quite differently in a thermal sense. Heat conduction to the upper aquitard was a major energy loss mechanism. Water sample analyses indicated that there were no important changes in the chemical constituents during the third set of experiments. There was a 19% increase in total dissolved solids. At the end of injection, the land surface near the injection well had risen 1.39 cm with respect to bench marks located 70 m away.