Study on Prediction Model of Calcium Carbonate Scaling Based on Three-Phase Equilibrium

Aiming at the problem of difficult scaling and high risk in experimental determination under high-temperature and high-pressure conditions, a prediction model of calcium carbonate scaling under high-temperature and high-pressure was established. The model starts from chemical equilibrium conditions, based on the carbonate gas-liquid-solid three-phase equilibrium conditions, considering the interaction between carbon dioxide concentration and various ions, using the solubility product rule to establish, using the Pitzer model to solve the compound activity coefficient, and calculating the parameters such as equilibrium constant and gas activity in the solution through the experimental regression model. The model can accurately predict the solubility of calcium carbonate in different aqueous solutions, which the error in pure water and barium chloride solution is within 5%, and the error considering the influence of carbon dioxide partial pressure is 14%. Using the model can accurately predict the scaling situation of the system under high temperature and high pressure, and has theoretical guiding significance for the implementation of downhole scale prevention process.