The Reservoir Liquids

Over 1000 chemical analyses of reservoir liquids coming from different geothermal systems were reconstructed combining the chemical analyses of the liquid and vapor phases discharged from drilled wells and collected at known separation temperature and pressure. All these reservoir liquids, apart from a few exceptions, have probably attained or closely approached the condition of chemical equilibrium with the hydrothermal (secondary) minerals occurring in the geothermal reservoirs of provenance at temperatures of 100-350°C. Therefore, they can be used to test geothermometers and \(f_{{{\text{CO}}_{2} }}\)-indicators, both the traditional ones and those derived in this work. The chemical characteristics of these reservoir liquids are illustrated through a comprehensive water-classification approach, including not only the triangular diagram of major anions but also the triangular diagram of main cations and suitable salinity plots, all prepared from concentrations in equivalent units. The fractions of free Na+, K+, Mg2+, and Ca2+ ions and undissociated SiO2(aq) and the activity coefficients of these entities are examined to highlight the effects of relevant association-dissociation reactions as well as of solute-solvent and solute-solute interactions.