Static Prediction of Anhydrite Scale Formation in Electrolyte Solutions of Oil Systems

In the present study, the prediction of dehydrated calcium sulfate sedimentation was studied in the oil system and the presence of electrolytic solution. In this study, in order to predict the amount of sediment, two equations for activity coefficient and constant thermodynamic equilibrium have been studied. The Extended UNIQUAC activity factor model has been used to investigate and determine the calcium sulfate mineralization index. The performance of this model is desirable in electrolytic systems and its coefficients are optimized based on empirical results. The results of this study were compared to experimental data, Pitzer and NRTL models, and the result of OLI3.2 software for the prediction of anhydrite mineral deposition. Based on the results, the total relative error of anhydrite precipitation prediction compared to the experimental results in the Extended UNIQUAC, Pitzer, and NRTL models and OLI3.2 software are 0.41(41%), 0.44 (44.72%), 0.53 (53%), and 0.99 (99%), respectively. Also, based on the results of the optimized model and the experimental results, the solubility of calcium sulfate precipitation in the presence of magnesium chloride and calcium chloride decreases with increasing temperature. By comparing the calculated results, it can be concluded that the proposed model has good accuracy. In this study, the pressure range was 25 to 250 bar and the temperature ranged from 1 to 300 ° C.