Types of the scaling in hyper saline geothermal system in northwest Turkey

• Scaling is one of the important problems in geothermal system.
• Scaling reduces the efficiency of the plant and causes economical loss.
• The scales formed in the Tuzla geothermal system were divided into two groups according to location.
• Downhole the scales were composed mainly of PbS and CaCO3.
• The surface pipeline contained saponite like amorphous structure.

Tuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. The geothermal brine from this area, which is dominated by NaCl, has a typical temperature of 173 °C. Rapid withdrawal of fluid to ambient surface conditions during sampling causes precipitation of various compounds known as scaling. Scaling is one of the important problems in Tuzla geothermal system that reduces the efficiency of the geothermal power plant and causes economical loss. The aim of this study was to determine the type of scaling as a first step towards preventing its formation. The scales formed in the geothermal system were divided into two groups according to location: the ones that formed in downhole and the ones that accumulated along the surface pipeline. Both scales were examined in terms of their elemental composition, structure and morphology using XRF, XRD, and SEM, respectively. The former was found to be mainly composed of PbS (Galena) and CaCO3 (aragonite or calcite). In contrast, the latter was heterogeneous in nature and consisted of mainly saponite like amorphous structure along with submicrometer-sized amorphous silica particles, layered double magnesium and iron hydroxide, and NaCl.