Hydrochemistry and geothermometry of thermal waters from UAE and their energetic potential assessment

Abstract

Abstract Two main low-enthalpy geothermal fields are present in the UAE: Mubazzarah-Ain Faidha (Al-Ain city) in the Abu Dhabi Emirate and Ain-Khatt in the Ras Al-Khaimah (RAK) Emirate. The chemistry of nineteen waters was analyzed to calculate geothermal reservoir temperatures using cation and silica geothermometers, and to describe the source of recharge of the hot waters from isotopic data. In total, 19 water samples (16 from wells, 2 from springs AF and KT1 and one sea water) were collected and analyzed for major anion and cation concentrations. The isotope and chemical data suggest that the hot waters from Al-Ain (Mubazzarah and Ain Faidha) are almost entirely recharged by rainwater, which originates at higher altitude, heats up through deep water circulation, and travels to the surface through fault structures within the study area. The waters are mainly Na-Cl type, and the discharge temperatures range from 32.5\u202f°C to 49\u202f°C. The Na-K geothermometers predict a geothermal reservoir temperature of 151\u202f°C for the Mubazzarah-Ain Faidha hot waters and 112\u202f°C for the Ain-Khatt hot waters with estimated depth of water penetration of 3.8\u202fkm and 2.6\u202fkm, respectively. The existing known geothermal resources in the Mubazzarah and Ain Khatt areas can be immediately and sustainably used for low-temperature, direct-use geothermal applications. A stochastic Monte Carlo simulation was performed to estimate the geothermal energy stored in the two main low-enthalpy geothermal fields for 25 years and 50\u202fyears. The geothermal electricity potential at Mubazzarah-Ain Faidha is ∼16.5 MWe and ∼8.27 MWe for 25 and 50\u202fyears, respectively. The geothermal electricity potential at Ain Khatt is ∼291 kWe and ∼146 kWe for 25 and 50\u202fyears, respectively. These preliminary potential assessments are subject to further delineation drilling and availability of field performance data and considered that the geothermal power plant has either a single or multiple ORC systems due to the very low temperature.