(257ai) Thermodynamic Modeling of Binary, Ternary and Quaternary Aqueous Solutions Containing Ba2+, Na+, Cl-, and SO42- By Enrtl Model

Thermodynamic modeling of binary, ternary and Quaternary aqueous solutions containing Ba²⁺, Na⁺, Cl^-, and SO₄^2- by eNRTL model

Soraya Honarparvar, Danny Reible, Chau-Chyun Chen

Department off Chemical Engineering, Texas Tech University

Fresh water consumption by oil and gas industry specifically hydraulic fracturing is rising huge concern of local water stress. In order to decrease fresh water demand for hydraulic fracturing, saline water sources such as flowback produced water are considered for usage in this industry. However, due to the high salinity as well as numerous electrolytes in flowback produced water, treatment and recycling of this type of water is facing challenges. Scaling potential by some existing electrolytes at fracturing temperature and condition is one of them. Barium (Ba²⁺) is the leading cation for scale formation and despite the high concentration of Chloride (Cl^-), sulfate (SO₄^2-) also can react with Ba²⁺ and precipitate in the fractures. Comprehensive thermodynamic modeling of the high salinity produced water is essential for the industry to master physical and chemical behavior of the electrolyte solutions.

In previous studies, Pitzer model has been used generally for modeling saline water. However, the model results are shown to be accurate only for dilute solution with molality up to 6, and also the need for ternary parameters in addition to binary interaction parameters make serious issues for application of this model in studying produced water. The number of Pitzer model parameters which needed to be correlated for produced water can easily exceed hundreds and there are not enough experimental data to do the regression.

Therefore in this study symmetric eNRTL activity coefficient model is used to model BaCl₂+H₂O binary system, BaSO₄+H₂O binary system, BaCl₂+NaCl+H₂O ternary system, BaSO₄+Na₂SO₄+H₂O ternary system, and the BaCl₂+BaSO₄+Na₂SO₄+NaCl+H₂O system. The model requires only molecule-electrolyte and electrolyte-electrolyte binary interaction parameters and three temperature coefficients for each of the binary parameter. Experimental data such as osmotic coefficient, mean ionic activity coefficient, vapor pressure, heat capacity, excess enthalpy, and salt solubility at different temperature up to 473.15 K and also at different electrolyte concentration up to saturation are used to identify the model parameters. The model provides accurate representation for all thermodynamic properties for the BaCl₂+BaSO₄+Na₂SO₄+NaCl+H₂O system and all its subsystems.