CO₂-brine interfacial tension correlation based on the classical orthogonal polynomials: monovalent salts with common anion

Accurate estimation of CO₂-brine Interfacial Tension (IFT) is of great importance since it is required to model the residual/capillary trapping of CO₂ in geological formations. In this paper, a novel correlation is proposed based on the classical orthogonal polynomials to estimate the CO₂-brine IFT of monovalent salts with common anion. To do so, CO₂-brine IFT samples composed of samples from the literature and experimentally measured values using an in-house high-pressure high-temperature IFT measurement device were collected within a wide range of temperatures, pressures, and salinities. The utilized brines included NaCl and KCl salts. Then, a predictive model was developed based on the Group Method of Data Handling approach as a function of temperature, pressure, and ionic strength. The proposed method was compared with four methods from the literature in terms of average absolute percentage error (AAPE), coefficient of determination R², histograms of error, and percent error plots. Results showed the superiority of the proposed method over other methods with an AAPE of 9.85 and R² of 0.719. Also, it was shown that the proposed method did not produce too large errors, contrary to other methods. Therefore, the proposed method can be used reliably as a tool for CO₂-brine IFT estimation in CO₂ storage projects.