GEOPHYSICAL EXPLORATION OF THE TUCSON MOUNTAINS, SOUTHERN ARIZONA, FOR POTENTIAL UNDERGROUND COMPRESSED AIR ENERGY STORAGE

Compared with batteries and other energy storage means, compressed air energy storage (CAES) presents a cost-effective solution for solar energy storage. Compressed air can be stored in natural geological reservoirs, such as bedded salt formations, karst systems, and various structural and stratigraphic traps. In the Tucson Mountains, a previously undelineated structural trap is being investigated using transient electromagnetic (TEM) and controlled source audio-magnetotellurics (CSAMT) and may provide an effective method for storage of compressed air.

The geology of the Tucson Mountains encompasses a complex history with several eruptive events over the past 20 million years. Underlying the impermeable lava flows and other volcanic rocks are much more permeable sedimentary units. Because of the nature of faulting around the Tucson Mountains, there is considerable offset of the electrically resistive Cat Mountain Tuff. Other Mesozoic units beneath the tuff are less resistive and provide some stratigraphic control within the relatively unexplored Tucson Mountains. This research attempts to map the depth and thickness of the tuff to better characterize the potential for CAES-appropriate traps within the mountains. Preliminary data support the hypothesized subsurface structure in previously published geological surveys within the mountains and provide support for potential fluid reservoirs within the study area.