In this modeling approach first the

In this modeling approach, first, the cross-association volume parameter of the various mixtures of water + hydrocarbon was optimized as the only adjusting parameter of the model. Previous studies showed [59], [60] aromatics can form weak hydrogen bonds with alcohols and water, but there is not enough support that paraffinic and naphthenic hydrocarbons form hydrogen bonds with water. It is generally known that heavy reservoir fluids normally contain high concentration of large molecule aromatics (aromatic, resin, and asphaltene fractions). However the solvation may not physically happen for all hydrocarbons in reality, but it HOBt is believed that considering reservoir fluids as pseudo-associating components can improve the phase equilibrium calculation. Similar approach has been taken previously by Li and Firoozabadi [50] for pure hydrocarbons and water binaries. The cross-association volume parameter of mixtures was fitted against the available equilibrium data at high temperatures. Eq. (10) was chosen as the objective function to minimize the deviation between the water solubility experimental data and calculated values. The optimized cross-association volume parameters were used to generate a correlation by which is expressed as a function of mixture\'s properties as shown in Eq. (11). This correlation was established using response surface method (RSM). Water solubility experimental data in the hydrocarbons presented in Table 2, except Athabasca bitumen and two mixtures of Athabasca + toluene, were used in model development. The water solubility data in Athabasca bitumen and two Athabasca bitumen + toluene mixtures, measured at very high temperatures, were chosen to evaluate the reliability and performance of the model. The generalized correlation for the cross-association volume parameter is described by: The presented correlation is a function of molecular weight (Mw) and Watson characterization factor In addition to simplicity, malleus correlation is compatible to the physical nature of interactions between water and hydrocarbons. A proper description of a hydrocarbon component can be achieved by Mw and . The molecular weight indicates the size of a component, and characterization factor represents chemical nature of hydrocarbons. It has been observed that by increasing carbon number and the size of hydrocarbons, water solubility in the mixtures decreases [32]. According to the suggested correlation, by increasing hydrocarbon Mw, will increase that means greater molar mass will lead to the larger volume association between water and hydrocarbon. As shown, Fig. 1 suggests a quadratic relationship between adjusted cross-association volume parameter and molecular weight of these hydrocarbons. Therefore, the presented correlation of was selected to be proportional to the second power of hydrocarbon molecular weight in the correlation. Characterization factor is another variable suggested in the presented correlation. Specific gravity (SG) and normal boiling point of hydrocarbons are needed to calculate Watson characterization factor [61], [62]: