Geochemical assessment of mineral scaling in Kızıldere geothermal field, Turkey

Abstract

The mineral scaling problems in the Kızıldere geothermal field along with hydrogeological and geochemical properties of this field were studied. In this content, chemical analyses for 26 water samples from 12 water points and an additional seven geochemical analyses and six XRD analyses of the scale samples were performed. Measured reservoir temperatures of wells vary from 196 (in the well KD-13) to 242 °C (in the well R-1). Geothermal reservoir waters show the water types of Na–HCO₃ and Na–HCO₃–SO₄. Estimated mineral saturations suggest that calcite, aragonite, strontianite, dolomite, amorphous silica, and barite are likely to precipitate as scales. These are confirmed by the results of the geochemical and XRD data of the scale samples. Reservoir chemistry calculations show a fluid richer in steam and acid gases with lower concentrations in the nonvolatile constituents (i.e., Cl, SiO₂, Na, etc.) at the reservoir. Geochemical modeling shows that CaCO₃ (calcite and aragonite) and strontianite precipitations are inevitable for production and re-injection wells and surface equipment. Amorphous silica scaling is the important risk of re-injection wells. Precipitations of the minerals barite, anhydrite, dolomite, and celestite are also possible. Determinations of the scaling minerals and the safety temperatures to avoid or minimize the scaling problem are the most important parts of this study. It was concluded that cold injection (<50 °C) is favored or inhibitors should be used if any mineral deposition is to be prevented or reduced in injection wells.