Prediction of Mineral Scaling Using a Comprehensive Thermodynamic Model

A comprehensive methodology has been developed for predicting mineral scaling in environments related to the oil and gas industry. The methodology is based on a previously developed model for mixed-solvent electrolyte systems (MSE). The model has been designed to calculate phase equilibria in multicomponent systems containing an aqueous phase, multiple solid phases, a gas phase, and a second liquid (typically hydrocarbon-dominated) phase. With this formulation, the model is capable of predicting the formation of scales not only in aqueous systems but also in environments that contain nonaqueous additives such as methanol or mono-, di-, and triethylene glycols. The performance of the model has been analyzed for various solids including calcium sulfate, barium sulfate, calcium carbonate and magnesium carbonate as a function of temperature, brine composition, pressure and the presence of methanol and glycols. Additionally, the model has been applied to predict the stability of minerals in the presence of CO₂-rich phases, which is expected to serve as a basis for modeling interactions between rocks and sequestered carbon dioxide.