An effective procedure for wax formation modeling using multi-solid approach and PC-SAFT EOS for petroleum fluids with PNA characterization

Abstract

Several experiments and thermodynamic models are developed to prevent Wax precipitation. Paraffinic hydrocarbons participate to a greater extent in the precipitation process than other hydrocarbon families. However, the existing models do not distinguish these hydrocarbon families, leading to the overestimation or underestimation of wax precipitation parameters. To address this problem, we will use a predictive Paraffin, Naphthene, and Aromatic (PNA) estimation technique to split the petroleum fractions that avoids using average properties for petroleum fractions. A sequential multi-solid approach is also implemented for the thermodynamic analysis of wax precipitation. The perturbed chain statistical associating fluid theory (PC-SAFT) equation of state (EOS) is utilized to calculate liquid properties. The binary interaction coefficients (BIC) of non-paraffin hydrocarbons are modified to improve the model's accuracy for calculating wax weight and wax appearance temperature (WAT). Six crudes from the North Sea are selected to evaluate the reliability of the proposed model. The contribution of each hydrocarbons family in the precipitation process is investigated. The results show a considerable improvement compared to previous models. The predicted WAT presents a slight deviation from the experimental data. In addition, the outcome of this work is compared to the modeling works from two reliable references. The average estimation error of wax weight for all crude oils is about 0.19. This deviation increases to 0.36 and 0.38 for the works of the first and second reference, in turn.