High Total Inorganic Carbon Concentration, Dependent Carbonate Scaling and Mitigation System, in Moderate to High Enthalpy Geothermal Fields in Turkey

Abstract

Most of Turkey’s geothermal fields contain high total inorganic carbon concentrations of 1,5 -3,0 wt.% CO2 in the 150 ºC-240 ºC single-phase reservoir liquid. This results in high flowing wellhead pressure and gas/steam ratio in the well bore, and CO2 concentrations in high pressure steam of 15-30 wt.%. At power plant gathering system design pressures, scale deposition is relatively minor in the well bore, but severe in surface piping, with general calcium carbonate deposition rates exceeding 1,5 meter/year, if appropriate mitigation techniques are not implemented. Application of organic phosphates and polymeric inhibitor reduced calcium carbonate deposition by more than 98 % over all well bores and plant surface equipments. Scale inhibitor must be injected below the depth of gas breakout to fully mitigate scale formation in the well bore, but feeding additional inhibitor at the surface is not necessary to prevent scale formation from the wellhead to the power plant. Geothermal development in Turkey has been hampered, in part, by high CO2 concentrations and the resulting severe calcium carbonate scale precipitation. In this paper, the determination of true gas breakout depth and appropriate scaling mitigation techniques for high carbon dioxide involver geothermal fields in Turkey will be discussed.