Prediction of mineral scale formation in geothermal and oilfield operations using the extended UNIQUAC model

Pressure parameters are added to the Extended UNIQUAC model presented by Thomsen and Rasmussen (Modeling of vapor-liquid-solid equilibrium in gas-aqueous electrolyte systems. Chemical Engineering Science 54, 1787-1802, 1999). The improved model has been used for correlation and prediction of solid-liquid equilibrium (SLE) of scaling minerals (CaSO4, CaSO4·2H2O, BaSO4 and SrSO4) at temperatures up to 300 °C and pressures up to 1000 bar. The results show that the Extended UNIQUAC model, with the proposed pressure parameters, is able to represent binary, ternary and quaternary solubility data within the experimental accuracy in the temperature range from −20 to 300 °C, and the pressure range from 1 to 1000 bar.