Geothermal Water Resources in Arizona: Feasibility Study: Project Completion Report

Abstract

Conventional geothermal water resources of Arizona are apparently limited to an east-west trending belt about 100 miles wide within the Basin-Range province of Arizona and closely following the Gila River. Hot-dry rock and magma-tap types of geothermal energy may also be present within this zone as well as outside it as for example, in the Flagstaff area. Numerous wells and springs with temperatures greater than 32 degrees C are found within the 100 mile-wide zone, and commonly their locations are coincident with linear features described by ERTS photographs. Application of geochemical geothermometers to these waters yields predicted reservoir temperatures up to 150 degrees C, although Tellier (1973) reports values up to 300 degrees C for waters from this region. Well logs, core, and outcroppings of basin fill deposits in Safford Basin suggest that thermal waters are contained in coarse sand and conglomeratic basin fill reservoirs and possibly in lava flows and tuff deposits under the sediments which fill the basin. Shallow lacustrine deposits of evaporites and clays probably function as cap rocks in this area preventing mixing of warm deeper waters with cooler surface waters. Igneous rocks of very recent age are consistently found within the zone containing the thermal waters. These bodies represent the most probable source of thermal energy, although in Safford Basin heat may originate from exothermic hydration reactions of anhydrite in lacustrine evaporite deposits.