Carbonate Scale Inhibition in a High-Gas Geothermal Well, Germencik, Turkey

Abstract

Germencik is the largest known high-temperature geothermal system in Turkey. Geothermal development in Turkey has been hampered, in part, by high CO2 concentrations and the resulting severe calcium carbonate scale precipitation. Germencik, originally drilled for production in the mid-1980’s, is now being fully developed with additional production and injection wells, and a 50 MW power plant. A 10-day flow test was completed to demonstrate that uninterrupted power generation could be accomplished with cost-effective scale inhibition. High total inorganic carbon concentrations of 2.0 wt.% CO2 in the 200°-230°C single-phase reservoir liquid results in high flowing wellhead pressure and gas/steam ratio in the well bore, and CO2 concentrations in high pressure steam of 20 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, and locally up to 88 meter/years, if appropriate mitigation techniques are not implemented. Application of PowerChem Geosperse 8466 polymeric inhibitor reduced calcium carbonate deposition by more than 99.9% over an eight-day application. 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.