CAES in aquifers is challenging because of a lack of geological data. Exploration drilling and geophysical surveys may be necessary to confirm the suitability of a geological aquifer structure.
Hydrodynamics’ CAES aquifer design experience indicates a complex air injection program is necessary to create a relatively dry working air storage volume. Air storage system reservoir simulation modeling is critical to the design of the air injection/withdrawal well pattern. Reservoir modeling is also necessary to the air storage system to match both the energy market cycle, and to match both the mass flow rate and pressure necessary to operate the turbo-machinery.
CAES in aquifer storage media often has the following challenges: (1) air storage pressure around the hydrostatic pressure of the aquifer may cause limitations on well productivity, (2) the potential for oxygen depletion, and (3) the potential presence of water in the produced air. Mitigation of these issues is dependent on the selection of an anticline structure at the proper depth, and choice of highly permeable porous media. The presence of a caprock above the air storage zone is also a key factor. The verification of the integrity of the caprock in an aquifer storage structure can only be confirmed by the injection of a test volume of air, often at considerable cost. In addition, exploratory drilling is typically necessary to confirm the geometry of the confining geological structure. Thus, siting criteria are essential to the success of a CAES aquifer storage system.
