Ability of the MHV2 mixing rule to describe the effect of salt on gas solubility in brines at high temperature and high pressure
Isabelle Vanderbeken, Suyu Ye, Brice Bouyssière, Hervé Carrier, Pierre Xans
An empirical model for gas solubility in brines under high temperatures and high pressures has been developed by modification of the modified Huron – Vidal second order (MHV2) model and evaluated by least squares fitting to available p – T – X (pressure – temperature – composition) data. The model is based on the MHV2 mixing rule. It combines the Soave – Redlich – Kwong (SRK) equation of state with a model for the excess Gibbs energy to calculate the mixture parameter, a. The ability of the MHV2 mixing rule to describe the effect of salt on gas solubility (CH4, CO2) in water – sodium chloride systems over a wide range of temperature and pressure has been investigated. A modified Wilson activity coefficient model was chosen, which is more flexible than the modified UNIFAC activity coefficient model which yields an unsatisfying evolution with temperature of the calculated gas solubility when a gas, such as methane, exhibits very low solubility in water – salt mixtures.