Investigation of synergistic thermodynamic inhibition effect of MEG and salt solution on gas hydrate

Abstract

This study examined the thermodynamic synergistic inhibition effects of MEG considering in case of produced water breakthrough, which includes high concentration of salts solution mixed with hydrocarbon fluids during natural gas production. First, we proposed the modified model based on Soave-Redlich-Kwong equation of state for expressing the vapor phase and van der Waals and Platteuw theory to predict the hydrate equilibrium conditions in the presence of both MEG and NaCl. The proposed model adopt the change of fugacity of gas component in aqueous MEG and NaCl solution using ENRTL-RK model in Aspen plus v8.6. The activity of water was determined by Margules equation for MEG, Pitzer equation for NaCl and temperature effect. The hydrate equilibrium conditions of solutions containing both MEG and NaCl with high salinity (∼20 wt%) was measured as well. The results showed that the hydrate formation condition was shifted toward lower temperature and higher pressure in accordance with the increased NaCl concentration. The proposed model was acceptably correspond with experimental data. For MEG and NaCl mixed solutions, the average deviation of hydrate formation pressures (AADP) of the proposed model had the lowest value of 5.37% compared to 17.52% of CSMGem and 13.77% of Multiflash.