Miscible gas injection processes could be among the most widely used enhanced oil recovery processes. Successful design and implementation of a miscible gas injection project depends upon the accurate determination of the minimum miscibility pressure (MMP) and other factors such as reservoir and fluid characterization. The MMP indicates the lowest pressure at which the displacement process becomes multicontact miscible. The experimental methods available for determining MMP are both costly and time consuming. Therefore, the use of correlations that prove to be reliable for a wide range of fluid types would likely be considered acceptable for preliminary screening studies. This work includes a comparative and critical evaluation of MMP correlations and thermodynamic models using an equation of state by PVTsim software. Application of gas injection usually entails substantial risk because of the technological sophistication and financial requirements to initiate the project. More detailed, comprehensive reservoir engineering and project monitoring are necessary for typical miscible flood projects than for other recovery methods. This project evaluated effects of important factors such as injection pressure, vertical-to-horizontal permeability ratio, well completion, relative permeability, and permeability stratification on the recovery efficiency from the reservoir for both miscible and immiscible displacements. A three-dimensional, three-phase, Peng-Robinson equation of state (PR-EOS) compositional simulator based on the implicit-pressure explicit-saturation (IMPES) technique was used to determine the sensitivity of miscible or immiscible oil recovery to suitable ranges of these reservoir parameters. Most of the MMP correlations evaluated in this study have proven not to consider the effect of fluid composition properly. In most cases, EOS-based models are more conservative in predicting MMP values. If screening methods identify a reservoir as a candidate for a miscible injection project, experimental MMP measurements should be conducted for specific gas-injection purposes. Simulation results indicated that injection pressure was a key parameter that influences oil recovery to a high degree. MMP appears to be the optimum injection pressure since the incremental oil recovery at pressures above the MMP is negligible and at pressures below the MMP recovery is substantially lower. Stratification, injection-well completion pattern, and vertical-to-horizontal permeability ratios could also affect the recovery efficiency of the reservoir in a variety of ways discussed in this work.

In natural systems, the solution concentration and hence, potential bioavailability of trace metals is primarily controlled by adsorption-desorption reactions at the mineral-water interface. While many studies have been conducted to understand the adsorption of trace metals to soil minerals, less is known about long-term adsorption/desorption processes. In this study, we examined the influence of mixing and sorption period on the desorption of lead from goethite. Lead sorption was rapid and essentially complete in 1 h, with no change in the quantity of lead adsorbed over the 6 month sorption period. Desorption of lead was slower than the adsorption reaction and was best modeled by two first order equations. At all sorption densities, the desorption of lead followed the order Short-term (24 h) > Long-term non-stirred (6 months) > Long-term stirred (6 months). However, statistical analysis indicated that these differences were not statistically significant. Furthermore, the desorption rate coefficients were very similar for all the experiments indicating that there was no significant residence time effect in this study. However, a sample from a previous study that was allowed to age 5 years and then analyzed by the desorption procedure did have statistically significant differences between the long-term (5 years) and the short-term (5 months). These results suggest that longer adsorption periods, perhaps a number of years, may be necessary to determine if residence time effects are an artifact of the experimental conditions or truly the length of the adsorption period. / Master of Science

Une fontaine peut se créer quand la flottabilité d'un rejet vertical s'oppose à sa quantité de mouvement. Ce type d'écoulement connaît beaucoup d'applications que ce soit dans la nature (panaches issus des éruptions volcaniques) ainsi que dans l'industrie du bâtiment (chauffage et refroidissement) ou dans le domaine des risques (rejets accidentel de gaz lourd). Dans cette thèse, nous nous focalisons sur l'étude des fontaines turbulentes miscibles. Dans le premier chapitre nous reformulons le modèle théorique de Morton et al. (1956) pour traiter le cas des fontaines en milieu linéairement stratifié. La résolution de ce modèle permet d'obtenir des relations analytiques pour la hauteur de la fontaine et sa hauteur d'étalement. Ce modèle est, par la suite, étendu au cas des panaches et des jets turbulents en milieu linéairement stratifié. Dans le second chapitre, nous proposons un modèle théorique permettant d'étudier une fontaine turbulente miscible en régime établi. Pour calibrer ce modèle, des simulations numériques aux grandes échelles (LES) sont utilisées pour obtenir une estimation des valeurs des constantes associées aux phénomènes d'échanges turbulents entre les parties ascendante et descendante de la fontaine. L'objectif du dernier chapitre est d'apporter, à partir d'expérimentations en laboratoire, des informations quantitatives sur l'influence de forts écarts de masses volumiques dans les écoulements de type fontaine. Les expériences sont réalisées pour des fontaines gazeuses (mélange air/hélium) en régime établi. / A fountain can occur when the buoyancy of a vertically released fluid opposes its momentum. Such flows have many applications in nature (plumes issuing from volcanic eruption), building industry (cooling or heating) or in the area of risk management (accidental release of heavy dangerous gas). In this thesis, we focus on the study of miscible turbulent fountains. In the first chapter, we revisit the theoretical model of Morton et al. (1956) to handle the case of fountains in linearly stratified fluid. The resolution of this model allows us to obtain analytical relations for the fountain height as well as the spreading height of its horizontal layer. This model is subsequently extended to the case of turbulent jets and plumes in linearly stratified fluid. In the second chapter, we propose a theoretical model for the study of a turbulent miscible fountain in a steady state. To calibrate this model, large eddy simulations (LES) are used to obtain an estimate of the values of the constants associated with the additional terms appearing in the equations. The objective of the final chapter is to provide, from laboratory experiments, quantitative information on the influence of strong density differences on the behaviour of a turbulent fountain. These experiments shows that all the classical relations valid for the Boussinesq case can be extended to the non-Boussinesq case by using an appropriate definition of the Froude number.

No description available.

Fluids injected during secondary and tertiary floods often leave parts of the reservoir unswept mostly because of large heterogeneity and mobility ratio. Several applications require an analytical scheme that could predict production with as few parameters possible. We develop such an analytical model of volumetric sweep that aims to apply an extension of Koval’s theory where flow is assumed to be segregated under vertical equilibrium conditions for secondary and tertiary displacements. The unified theory for vertical equilibrium (viscous and dispersive) is also derived as a precursor to model development. The original Koval factor is applicable for upscaling secondary miscible floods. The new analytical model for secondary and tertiary floods is applied to provide quick estimates of oil recovery of miscible as well as immiscible displacements, which is then calibrated against field data. The model parameters, Koval factor, sweep efficiency and pore volume, estimated after history matching could be used to make reservoir management decisions. The model is very simple; history matching can be done in a spreadsheet. Single-front, gravity-free, displacements can be modeled using Koval factors. Two-front, gravity-free, displacements can also be modeled using Koval-type factors for both the fronts. These Koval-type factors, coupled with laboratory scale relative permeabilities, allows for scaling the displacement to a larger reservoir system. The new method incorporates by-passed pore volume as a parameter, a difference between this work and that of Molleai, along with Koval factors and local front velocities. For two front displacements, it also accounts for the interaction between the fronts which honors correct mass conservation, another difference with the work of Molleai. The results from new models for secondary and tertiary displacements were verified by comparing them against numerical simulations. The application was also demonstrated on actual field examples. Current techniques for reservoir surveillance rely on numerical models. The parameters on which these numerical models depend on are very large in number, introducing large uncertainty. This technique provides a way to predict performance without the use of computationally expensive fine scale simulation models, which could be used for reservoir management while reducing the uncertainty. / text

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No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Russell T. Johns. Vita. Includes bibliographical references.

No description available.

En utilisant une approche principalement expérimentale, cette thèse de doctorat étudie les écoulements de déplacement miscibles flottants dans les tuyaux à rotation axiale, un sujet fondamental de la mécanique des fluides qui est également motivé par le processus de cimentation dans les constructions de puits de pétrole et de gaz. Une partie du processus de cimentation consiste à pomper un fluide lourd dans un tuyau pour éliminer/déplacer un fluide léger in situ. Nous émettons l’hypothèse qu’une rotation axiale du tuyau peut être utilisée pour améliorer le processus de déplacement, bien que sans résultats expérimentaux en laboratoire pour soutenir cette croyance. Dans ce contexte, ce travail analyse systématiquement les effets d’une rotation axiale du tuyau sur les flux de déplacement miscibles flottants en présence de la différence de densité (flottabilité), de l’angle d’inclinaison du tuyau, de la vitesse d’écoulement imposée et de la contrainte de déformation plastique du fluide déplacé. Le chapitre 1 étudie les effets de la rotation axiale du tuyau sur nos écoulements flottants en l’absence de la vitesse d’écoulement imposée (c’est-à-dire une configuration d’écoulement d’échange). Les deux fluides considérés sont iso-visqueux et newtoniens, mais ils ont une petite différence de densité. Les angles d’inclinaison des tuyaux intermédiaires sont pris en compte. Comme les deux fluides s’interpénètrent, notre objectif est de quantifier les effets de la vitesse de rotation des tuyaux sur la dynamique du front d’interpénétration, pour lesquels plusieurs corrélations empiriques sont proposées. Il s’agit notamment des corrélations pour la vitesse du front, la longueur de propagation du front et le temps de propagation du front. Les deux derniers concernent la situation où l’interpénétration des fluides s’arrête finalement lorsque la vitesse de rotation du tuyau devient importante. Le chapitre 2 étend les résultats du flux d’échange flottant du chapitre 1 à une configuration de flux de déplacement où il existe un flux imposé. Les deux fluides sont newtoniens. Un front d’attaque et un front de fuite sont observés dans le flux de déplacement. Fait intéressant, le mouvement du front arrière est fortement affecté par la vitesse de rotation. Ici, l’accent est mis sur la quantification des effets de la vitesse de rotation du tuyau sur les vitesses frontales avant et arrière. Le signe de la vitesse du front de fuite aide à classer les régimes d’écoulement en régimes d’élimination inefficaces et efficaces, pour lesquels la transition peut être justifiée en utilisant un équilibre entre l’inertie imposée, la flottabilité et les forces de rotation. iii En considérant une contrainte de déformation plastique dans le fluide déplacé, le chapitre 3 ajoute un autre paramètre à notre système d’écoulement. Ici, le déplacement d’un fluide viscoplastique (un gel de Carbopol) par un fluide newtonien dans des tuyaux à rotation axiale est étudié. Les comportements d’écoulement en termes de dynamique du front et de schémas d’écoulement sont considérés. Les effets de la rotation des tuyaux sur les vitesses frontales avant et arrière sont quantifiés. Enfin, les déplacements viscoplastiques sont comparés qualitativement et quantitativement à leurs homologues newtoniens, montrant que la contrainte de déformation plastique a un effet négligeable sur la classification du régime. / Through a mainly experimental approach, this Ph.D. thesis studies buoyant miscible displacement flows in axially rotating pipes, a fundamental fluid mechanics topic that is also motivated by the cementing process in oil and gas well constructions. A part of the cementing process involves pumping a heavy fluid into a pipe to remove/displace an in-situ light fluid. It is believed that an axial rotation of the pipe can be used to enhance the displacement process, albeit without laboratory experimental results to support this belief. In this context, this work systematically analyzes the effects of an axial rotation of the pipe on buoyant miscible displacement flows in the presence of the density difference (buoyancy), the pipe inclination angle, the imposed flow velocity and the yield stress of the displaced fluid. Chapter 1 investigates the effects of the axial rotation of the pipe on buoyant flows in the absence of the imposed flow velocity (i.e. an exchange flow configuration). The two fluids considered are iso-viscous and Newtonian, but they have a small density difference. Intermediate pipe inclination angles are considered. As the two fluids interpenetrate, our focus is to quantify the effects of the pipe rotation speed on the interpenetration front dynamics, for which several empirical correlations are proposed. These include correlations for the front velocity, the front propagation length, and the front propagation time. The two latter concern the situation where the interpenetration of the fluids eventually stops as the pipe rotation speed becomes large. Chapter 2 extends the buoyant exchange flow results of Chapter 1 to a displacement flow configuration where there exists an imposed flow. The two fluids are Newtonian. A leading front and a trailing front are observed in the displacement flow. Interestingly, the motion of the trailing front is highly affected by the rotation speed. Here, the focus is on quantifying the effects of the pipe rotation speed on the leading and trailing front velocities. The sign of the trailing front velocity helps to classify the flow regimes into inefficient and efficient removal regimes. The transition of these two regimes can be justified using a balance among imposed inertia, buoyancy and rotational forces. By considering a yield stress in the displaced fluid, Chapter 3 adds another flow parameter to our flow system. Here, the displacement of a viscoplastic fluid (i.e. a Carbopol gel) by a Newtonian fluid in axially rotating pipes is studied. The flow behaviours in terms of the front v dynamics and flow patterns are considered. The effects of the pipe rotation on the leading and trailing front velocities are quantified. Finally, the viscoplastic displacements are qualitatively and quantitatively compared against their Newtonian counterparts, showing that the yield stress has a negligible effect on the regime classification.