Effect of Methanol and Ethylene Glycol on Sulfates and Halite Scale Formation

A self-consistent activity model is presented to calculate the effect of methanol on barite, gypsum, celestite, and halite solubility in methanol/water/salt and ethylene glycol/water/salt solutions. The model parameters are derived from experimental studies at 0−6 m ionic strength, 4−50 °C, and 0−90 wt % of methanol and to a lesser extent of ethylene glycol concentrations. Pitzer theory is used to model the effect of salt, and a Born-type equation approach is used to model the effect of methanol. The barite solubility is significantly reduced, by as much as 20-fold, with 50% methanol. Other mineral solubilities are also reduced significantly. Ethylene glycol has much less impact on the mineral solubility than methanol. Good agreements between the model prediction and both experimental and literature results are observed.