Toward Development of a Universal CP-PC-SAFT-Based Modeling Framework for Predicting Thermophysical Properties at Reservoir Conditions: Inclusion of Surface Tensions

Abstract

This study presents an approach for predicting surface tensions (ST) of mixtures coupling the critical-point-based perturbedchain statistical association fluid theory (CP-PC-SAFT) and the square gradient theory (SGT). This modeling framework implements standardized and transparent parametrization procedures. As an input it requires the pure compound critical temperatures and pressures along with the triple point densities and surface tensions, without further adjustment to ST data of mixtures. Its predictions of a major part of the existing surface tension data on asymmetric binary systems, including the aqueous solutions, in the entire available range of conditions, are discussed. The results demonstrate that the proposed approach is characterized by a remarkable overall robustness and reliability. However, the system toluene (1)−water (2) poses a clear limitation to its predictive implementation. Predictions of CP-PC-SAFT coupled with the generalized modified Yarranton−Satyro correlation for the recently published data on saturated liquid CO 2 (1)−n-alkane (2) phases are also presented.

Bulk and Interfacial Properties of the Decane + Brine System in the Presence of Carbon Dioxide, Methane, and Their Mixture

“…2 Note that among the different species, the maximum difference (differ by a factor of up to ~2) between the simulated and calculated densities is obtained for CO 2 , especially at high pressures. In all cases, the density profiles show local enrichment of gas molecules at the interface, but no such behavior is seen for n-decane in agreement with the previous studies [38][39][40][41][43][44][45][46][47][48][49][50][51][52][53] . That is, a positive surface activity is seen for both methane and carbon dioxide (dn i /dz = 0; d 2 n i /dz 2 < 0 in the interfacial region).…”

“…The correlation between the IFT and the local enrichment of the interface in methane and carbon dioxide will be discussed in detail below. Notably, theoretical calculations based on other equations of state [38][39][40][41][43][44][45][46][47][48][49][50][51] , such as the statistical associating fluid theory, can also give accurate estimates of the bulk and interfacial properties of these www.nature.com/scientificreports www.nature.com/scientificreports/ binary systems. One of the main properties governing the design and operation of CCS and EOR processes is the miscibility of the injected CO 2 with oil 24,36 .…”

“…In general, the IFT of CH 4 + n-decane and CO 2 + n-decane systems decreases with increasing pressure and temperature. However, at high pressures, the IFT of the CO 2 + n-decane system increased with increasing temperature 37,40,41,50 . This can be explained by the fact that the local adsorption of gas molecules at the interface is more pronounced for carbon dioxide when compared to that of methane, especially at low temperatures.…”

“…The bulk and interfacial properties of binary mixtures of methane or carbon dioxide with alkanes such as n-decane (model oil in this work) under reservoir conditions receive continuous attention and many experimental [30][31][32][33][34][35][36][37][38][39][40][41][42] , theoretical [38][39][40][41][43][44][45][46][47][48][49][50][51] , and simulation 39,46,[52][53][54][55][56] studies have been reported. These studies, for example, showed that the mole fractions of methane and carbon dioxide in the decane-rich phase increase with pressure.…”

Calculation of surface tensions for liquid mixtures using the SWCF‐VR EOS and Butler‐type method

“…In Figure , the trends of surface tensions with pressures and bulk liquid compositions are plotted for nitrogen and methane mixtures at different given temperature. It can be seen that the theoretical model can well predict the experimental surface tensions at 95 and 105 K, while it fails to give the descriptions of surface tension at 120 K which is close to the critical temperature (126.2 K) of nitrogen, showing that the critical properties should be considered and included in a suitable EOS …”