Accurate Determination of the CO2–Brine Interfacial Tension Using Graphical Alternating Conditional Expectation

Abstract

A newly developed CO2–brine interfacial tension (IFT) correlation based on the alternating condition expectation (ACE) algorithm has been successfully proposed to more accurately estimate the CO2–brine IFT for a wide range of reservoir pressure, temperature, formation water salinity and injected gas composition. The new CO2–brine correlation is expressed as a function of reservoir pressure, temperature, monovalent cation molalities (Na+ and K+), bivalent cation molalities (Ca2+ and Mg2+), N2 mole fraction and CH4 mole fraction in injected gas. This prediction model is originated from a CO2–brine IFT database from the literature that covers 1609 CO2–brine IFT data for pure and impure CO2 streams. To test the validity and accuracy of the developed CO2–brine IFT model, the entire dataset was divided into two groups: a training database consisting of 805 points and a testing dataset consisting of 804 points, which was arbitrarily selected from the total database. To further examine its predicted capacity, the...