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A generalized corresponding-states model based on two reference fluids and a parachor correlation were developed for the prediction of interfacial tensions for non-polar and weakly polar pure fluids and mixtures. Pure methane and n-octane were chosen as reference fluids of the corresponding-states model. The two models were tested on 86 pure substances, more than 30 binary and multicomponent mixtures, 1 1 naphtha reformate cuts, 6 petroleum cuts and 2 North Sea oil mixtures. The calculated results were found to be in good agreement with experimental data.Un modele d'etats correspondants generalise s'appuyant sur deux fluides de reference et une correlation de parachor a ete mis au point pour la prediction des tensions interfaciales pour des fluides et des melanges purs non polaires et legerement polaires. Du methane et du n-octane purs ont ete choisis comme fluides de reference du modele d'etats correspondants. Les deux modeles ont ete testes sur 86 substances pures, plus de 30 melanges binaires et multicomposants, 11 coupes de reformat de naphta, 6 coupes de petrole et 2 melanges de petrole de la mer du Nord. On a trouve un bon accord entre les resultats calcules et les donnees experimentales.Keywords: corresponding-states, parachor, interfacial tension, reference fluids.he interfacial tension (IFT) is an important parameter for T modeling many secondary and tertiary recovery processes of petroleum reservoir fluids. In immiscible displacements, the efficiency of the recovery process is influenced by the IFT between the fluid phases present in the reservoir. In gas condensate systems, for instance, the low JFT is the dominant fluid property which determines relative permeabilities and residual liquid saturations. There are several methods available for predicting IFTs, e.g. the parachor method, the gradient theory and the corresponding-states theory.The standard method of IFT predictions in reservoir simulators is the parachor method proposed by Weinaug and Katz (1943) and its extensions. The parachor method is sensitive to the accuracy of the parachor because of the fourth power relationship between the IFT and the parachor. Gasem et al. (1989) compared the Weinaug-Katz (1943), Lee-Chien (1984) and Hugill-van Welsenes (1986) models. The results indicated that each of these models could represent the data with average errors of less than 10% if a scaling exponent of 3.6 was incorporated in the models and some parameters were tuned to fit experimental data. More recently, Ali (1994) reviewed the methods for estimating the parachors of petroleum fractions and pseudocomponents and compared seven existing IFT correlations. All the correlations predicted the results with deviations around 2040%.The gradient theory (GT) of interfaces has been successfully used for estimating interfacial properties of pure fluids and mixtures (Carey et al., 1978, Sahimi and Taylor, 1991, Cornelisse et al., 1993. However, since the GT is complicated and time-consuming, it is difficult to apply the GT to multicomponent mixtures and re...

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