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-This experimental study is aimed at evaluating the performance of the miscible WaterAlternating-CO 2 (CO 2 -WAG) flooding as a function of slug size and WAG ratio based on the ultimate oil recovery in the Sarvak formation. In this research, initially the slim-tube apparatus was used to determine the Minimum Miscibility Pressure (MMP) of the Sarvak heavy oil and CO 2 at the constant reservoir temperature. Then, a total of seven core flooding experiments were performed by using the sandstone core samples collected from the Sarvak formation. These experiments were conducted through respective water flooding, miscible continuous CO 2 flooding, and miscible CO 2 -WAG flooding. In the miscible CO 2 -WAG flooding, different WAG slug sizes of 0.15, 0.25, and 0.50 Pore Volume (PV) and different WAG ratios of 1:1, 2:1, and 1:2 were applied to investigate their effects on the oil Recovery Factor (RF) in the Sarvak formation. The results showed that, in general, the miscible CO 2 Enhanced Oil Recovery (CO 2 -EOR) process is capable of mobilizing the heavy oil and achieving a high and significant oil RF in the Sarvak formation. The miscible CO 2 -WAG flooding has the highest oil RF (84.3%) in comparison with water flooding (37.7%), and miscible continuous CO 2 flooding (61.5%). In addition, using a smaller WAG slug size for miscible CO 2 -WAG flooding leads to a higher oil RF. The optimum WAG ratio of the miscible CO 2 -WAG flooding for the Sarvak formation is approximately 2:1. The results also demonstrated that, more than 50% of the heavy oil is produced in the first two cycles of the miscible CO 2 -WAG flooding. The optimum miscible CO 2 -WAG flooding has a much less CO 2 consumption than the miscible continuous CO 2 flooding.

and available online here Cet article fait partie du dossier thématique ci-dessous publié dans la revue OGST, Vol. 70, n°6, pp. 909-1132 et téléchargeable ici D o s s i e rOil & Gas Science and Technology -Rev. IFP Energies nouvelles, Vol. 70 (2015), No. 6, pp. 909-1132 Copyright © 2015, IFP Energies nouvelles > Editorial -Enhanced Oil Recovery (EOR), Asphaltenes and HydratesÉditorial -EOR «récupération assistée du pétrole», Asphaltènes et Hydrates D. Langevin and F. Baudin ENHANCED OIL RECOVERY (EOR) > HP-HT Drilling Mud Based on Environmently-Friendly Fluorinated ChemicalsBoues de forage HP/HT à base de composés fluorés respectueux de l'environnement Abstract -Asphaltene instability may occur when pressure, temperature and compositional variations affect the reservoir oil. Permeability reduction, wettability alteration, and plugging of wells and flow lines are the consequences of this phenomenon. Therefore, it is crucial to investigate the asphaltene behavior in different thermodynamic conditions by knowing the Asphaltene Precipitation Envelope (APE) in a preventive way rather than the costly clean-up procedures. The selected reservoir oil has faced a remarkable decline in production due to several years of extraction, and Enhanced Oil Recovery (EOR) has been considered as a solution. Therefore, in this paper, a comprehensive study was carried out to predict the effects of different injected gases on asphaltene onset and to prevent future asphaltene precipitation based on the laboratory data. The Advanced Redlich-Kwong-Soave (RKSA) equation of state was considered to develop APE using Multiflash (Infochem Co.). For the selected reservoir oil, with temperature reduction at low temperatures, asphaltene precipitation weakened and made the onset pressure decrease, so this behavior is different from the results obtained in other published reports. On the basis of this model, several sensitivity analyses were performed with different gases (i.e., methane, CO 2 , N 2 and associated gases) to compare the risk of each gas for future EOR strategies. APE tend to expand as the amount of injected gases increases, except for CO 2 gas injection, that showed another unconventional behavior for this crude oil. It was observed that for CO 2 gas injection below a certain temperature, asphaltene stability increased, which can be considered as a good inhibitor of asphaltene precipitation.Re´sume´-Pre´vision de l'effet d'injection de gaz sur l'enveloppe de phase des asphalte`nes -L'instabilite´des asphalte`nes peut se produire lorsque des variations de pression, de tempe´rature et de composition affectent les re´servoirs d'huile conduisant a`une re´duction de la perme´abilite´, a`l'alte´ration de la mouillabilite´et au blocage de l'e´coulement dans les puits et les conduites. Par conse´quent, il est crucial d'e´tudier le comportement des asphalte`nes pour diffe´rentes conditions thermodynamiques en connaissant leur domaine de pre´cipitation (APE, Asphaltene Precipitation Envelope) de manie`re pre´ventive pour limiter les ope´ra...

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