Effects of Monoethylene Glycol on Carbonate Equilibrium and Calcite Solubility in Gas/Monoethylene Glycol/ NaCl/Water Mixed Systems

摘要

Monoethylene glycol (MEG), HOCH_2CH_2OH, is an important raw material with numerous industry applications, which include polyester synthesis, automobile antifreeze, coolant, and aircraft anti-icer. In the oil and gas industry, MEG is commonly used as a gas-hydrate inhibitor, which can prevent the formation of gas hydrate during natural-gas production. However, common gas-hydrate inhibitors have the adverse effects of lowering the solubility of mineral salts and causing a higher risk of scale formation. Despite the importance of scale problems with MEG in oil production, there have been few investigations on the solubility of mineral salt in MEG/brine solutions. In our research, experiments have been conducted on carbonate equilibrium and calcite solubility at 2-70℃, 0- to 6.5-m (m = molality) ionic strengths, and 0-99.67 wt% MEG.rnA self-consistent activity model based on the Pitzer theory to calculate the effect of salt and a Born-type equation were used to model the effect of MEG. MEG activity coefficients with respect to dissolved carbon dioxide (CO_2), sodium bicarbonate, sodium carbonate (NaHCO_3), and calcium are determined as a function of temperature, ionic strength, and mole fraction of MEG in mixed solvent.