Effects of the well characteristics and operational parameters on the scaling processes and scale formation

Abstract

A solubility equilibrium program GEOPROF developed earlier was applied for the determination of the bubble point depth, pressure and temperature as well as the partial pressure profiles of the gases CO2, CH4 and N2 between the bubble point depth and the well head in two high enthalpy geothermal wells NSZ-2 and FAB-4. Additionally the pH, the alkalinity the total carbonate, the equilibrium solubility for CaCO3, CaSO4, BaSO4, SrSO4 along the well depths in Na-K-Mg-Ca-H-Ba-Sr-Cl-Br-SO4-OH-HCO3-CO3-CO2-H2O system were determined and the concentrations of the Ca2+, Ba2+,Sr2+,H+, OH-, HCO3-, CO32-, and the H2CO3* were computed at the actual temperature, CO2 pressure using the Davies and the Pitzer activity calculation methods. The calculated amounts of scaling CaCO3 along the wells and at the surface were used in the estimation of the suggested service life. The results for the well FAB-4 have high uncertainties because of the estimated gas separation analysis data.