Preliminary investigations of scaling and corrosion in high enthalpy geothermal wells in Hungary

摘要

A solubility equilibrium program GEOPROF was applied to the determination of the bubble-point depth, pressure and temperature, as well as the partial pressure profiles of the gases CO_2, CH_4 and N_2 between the bubble-point depth and the wellhead, in two high enthalpy geothermal wells, NSZ-2 and FAB-4 in southern Hungary. The pH, alkalinity, total carbonates, and equilibrium solubility for CaCO_3, CaSO_4, BaSO_4, and SrSO_4 along the well depth profile in the Na-K-Mg-Ca-H-Ba -Sr-Cl-Br-SO_4-OH HCO_3-CO_3-CO_2-H_2O system were also determined and the concentrations of Ca~(2+) , Ba~(2+) , Sr~(2+) , H~+ , OH~-, HCO_3~-, CO_3~(2-), and H_2CO_3~* were computed at the actual temperature and CO_2 pressure using the Davies and Pitzer activity calculation methods. The calculated amounts of CaCO_3 scaling along the wells and at the surface were used in estimating service life. The results for well FAB-4 contain high uncertainties because of the estimated gas separation analysis data.