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Résumé -Propriétés interfaciales saumure/CO 2 et effets sur le stockage du CO 2 dans des aquifères salins profonds -Il est admis depuis longtemps que les propriétés interfaciales (tension interfaciale, mouillabilité, capillarité et transfert de masse) régissent la distribution et le comportement des fluides au sein des milieux poreux. Par conséquent, les propriétés interfaciales entre le milieu poreux constituant le réservoir, le CO 2 , la saumure et/ou le gaz du réservoir jouent un rôle important sur l'efficacité de n'importe quelle opération de stockage de CO 2 . Dans le cas des aquifères salins profonds, il existe un manque de données certain en ce qui concerne les propriétés interfaciales saumure-CO 2 en conditions de stockage. Plus spécifiquement, des données expérimentales de tension interfaciale saumure-CO 2 et une meilleure compréhension du comportement de la mouillabilité en fonction des conditions thermodynamiques et ses effets sur l'écoulement dans le milieu poreux sont nécessaires. Dans cet article, nous présentons un jeu de données expérimentales complet de tensions interfaciales (IFT) en conditions de pression, température et salinité représentatives de celles d'un site de stockage, et une corrélation semi-analytique pour modéliser les valeurs expérimentales dont certaines ont été récemment publiées [Chalbaud C., Robin M., Lombard J.-M., Egermann P., Bertin H. (2009)

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIt has been long recognized that interfacial interactions (interfacial tension, wettability, capillarity and interfacial mass transfer) govern fluid distribution and behavior in porous media. Therefore the interfacial interactions between CO 2 , brine and reservoir oil and/or gas should have an important influence on the effectiveness of any CO 2 storage operation. As a model, the interfacial tension of the pure water-CO 2 system has been studied intensively. Nevertheless, to our knowledge, no interfacial tension (IFT) equilibrium data for brine-CO 2 systems are available at reservoir conditions for different salinities, temperatures and pressures.In this paper, we present experimental IFT brine-CO 2 data obtained at high pressures (45 to 255 bar), high temperatures (27 to 100°C) and different salt concentrations (5,000 to 150,000 ppm of NaCl) using the axi-symmetric drop shape analysis technique (ADSA) for a rising drop case. Special attention was paid in developing a procedure to achieve true thermodynamic equilibrium. The themodynamic conditions were selected in order to cover the most practical CO 2 storage cases of interest, liquid and supercritical CO 2 . A correlation was developped on the basis of the Parachor model, the salt effect and a regression fit of more than a hundred IFT experimental values obtained in this study. This correlation yields a Brine-CO 2 IFT prediction at reservoir conditions with a mean absolute deviation of 2.5%. We also present correlations to determine the IFT increase due to salt concentration. The existence of a plateau in the brine-CO 2 IFT values, independent of the temperature and the pressure and only dependent on the salt concentration, has been demonstrated from the experimental data for temperatures between 27 to 71°C and pressures above 150 bar. These pressure and temperature values can be easily found in many geological sites considered as prospects for CO 2 storage. The linear dependency of the IFT increase with molal NaCl concentration has also been demonstrated.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA proper modeling of tertiary recovery processes such as gas injection or WAG (Water Alternating Gas) requires an adequate three-phase flow model. This allows to better predict the recovery efficiency, gas storage reservoir performance as well as the well injectivity.For gas drainage, a previous paper [25] presented a new threephase flow model based on a theoretical analysis and validated through experimental approach. For WAG injection, there is an additional complexity due to the need to model the imbibition that occurs when gas saturation decreases. To tackle the modeling of hysteresis problem, a comprehensive approach was followed. First, successive drainage and imbibition experiments were conducted under various conditions of initial saturations. A new three-phase model taking into account the hysteresis is presented and validated on the experiments.Indeed, as shown in previous experimental studies, hysteresis was found to depend not only on the drainage/imbibition process (saturation history) but also on the cycle considered (displacement history) where cycle names the association of two consecutive displacements (drainage and imbibition). In this study, a relevant analytical expression of the hysteresis is proposed avoiding any negative effect of numerical instabilities. The new formulation was implemented in a reservoir simulator and WAG experiments have been successfully simulated. The impact on breakthrough time, overall recovery efficiency was tested through large scale reservoir simulations.