Chemical treatments using solvents and surfactants can be used to increase the productivity of gas-condensate wells with condensate banks. CMG’s compositional simulator GEM was used to simulate such treatments to gain a better understanding of design questions such as how much treatment solution to inject and to predict the benefits of such treatments. GEM was used to simulate treatments in vertical wells with and without hydraulic fractures and also horizontal wells. However, like other commercial compositional simulators, the flash calculations used to predict the phase behavior is limited to two phases whereas a three-phase flash is needed to accurately model the complex phase behavior that occurs during and after the injection of treatment solutions. UTCOMP is a compositional simulator with three-phase flash routine and attempts were made to use it to simulate such well treatments. However, this is a very difficult problem to simulate and all previous attempts failed because of numerical problems caused by inconsistent phase labeling (so called phase flipping) and the discontinuities this causes in the relative permeability values. In this research, a new relative permeability model based on molar Gibbs free energy was developed, implemented in a compositional simulator and applied to several difficult three-phase flash problems. A new way of modeling the residual saturations was needed to ensure a continuous variation of the residual saturations from the three-phase region to the two-phase region or back and was included in the new model. The new relative permeability model was implemented in the compositional reservoir simulator UTCOMP. This new relative permeability model makes it is unnecessary to identify and track the phases. This method automatically avoids the previous phase flipping problems and thus is physically accurate as well as computationally faster due to the improved numerical performance. The new code was tested by running several difficult simulation problems including a CO2 flood with three-hydrocarbon phases and a water phase. A new framework for doing flash calculations was also developed and implemented in UTCOMP to account for the multiple roots of the cubic equation-of-state to ensure a global minimum in the Gibbs free energy by doing an exhaustive search for the minimum value for one, two and three phases. The purpose was to determine if the standard method using a Gibbs stability test followed by a flash calculation was in fact resulting in the true minimum in the Gibbs free energy. Test problems were run and the results of the standard algorithm and the exhaustive search algorithm compared. The updated UTCOMP simulator was used to understand the flow back of solvents injected in gas condensate wells as part of chemical treatments. The flow back of the solvents, a short-term process, affects how well the treatment works and has been an important design and performance question for years that could not be simulated correctly until now due to the limitations of both commercial simulators and UTCOMP. Different solvents and chase gases were simulated to gain insight into how to improve the design of the chemical treatments under different conditions. / text

Nous avons effectué 14 simulations de collisions majeures de galaxies spirales riches en gaz. Ces simulations ont été réalisées grâce à GCD+, un algorithme qui inclue la gravité, l'hydrodynamique, la formation stellaire et un traitement détaillé de l'enrichissement en métaux. Nous avons analysé les propriétés cinématiques, structurelles et chimiques des étoiles formées avant, pendant et après la collision. Ces collisions forment une galaxie ayant un disque pouvant être divisé en deux composantes. Ces deux composantes peuvent correspondre au disque mince et au disque épais d'une galaxie, et leur profil de luminosité peut être ajustées par une loi exponentielle. Les étoiles formées avant et pendant la collision ont une longueur d'échelle plus grande que les étoiles formées après la collision par 20% en moyenne. Du point de vue de la cinématique, les étoiles vieilles ont des dispersions en vitesse plus élevées et sont en retard sur les étoiles jeunes pour ce qui est de la vitesse de rotation. Le sursaut de formation d'étoiles associé à la collision permet d'enrichir rapidement le gaz en différent métaux. Les explosions de supernovae de type II qui ont lieu rapidement après la collision, étant donné la courte durée de vie des étoiles qui les produisent, enrichissent le milieu intergalactique en éléments a. Les supernovae de type la, ayant une distribution plus étendue dans le temps, permettent l'enrichissement en fer des deux populations associées aux composantes du disque, ce qui permet d'obtenir une population stellaire vieille ayant un rapport [a/Fe] supérieur à celui des étoiles jeunes et ce, même à des métallicités relativement élevées ([Fe/H] = —0.5). Ce résultat pourrait expliquer le rapport [a/Fe] élevé que l'on retrouve chez les étoiles du disque épais de la Voie lactée. / We employ GCD+, a N-body, smoothed particle hydrodynamic simulation, including star formation and a detailed treatment of chemical enrichment, to follow 14 gas-rich mergers that resuit almost ail in a galaxy with disk morphology. We trace the kinematic, structural, and chemical properties of stars formed before, during, and after the merger. We show that such merger produces two exponential disk components, with the older, hotter component having a scale length 20% larger than the later forming, cold disk. On a kinematical point of view the old stellar population clearly lags the rotation velocity of the young disk and hâve a higher rotational velocity dispersion. Rapid star formation during the mergers quickly enriches the protogalactic gas réservoir, resulting in high metallicities of the forming stars. Thèse stars form from gas largely polluted by Type II supernovae, which form rapidly in the merger-induced starburst. After the mergers, a thin disk forms from gas that has had time to be polluted by type la supernovae. This fact lead to an old stellar population with a higher [a/Fe] ratio than the young population at quite high metalicity ([Fe/H] = —0.5). We examine the proposai that increased star formation during gas-rich mergers may explain the high a-to-iron abundance ratios that exist in the relatively high-metallicity, thick-disk component of the Milky way.