Motion of an Oil Droplet Through a Water-Filled Uneven Pore Déplacement d'une gouttelette d'huile à travers un pore irrégulier rempli d'eau

The need to understand various mechanisms governing fluid-fluid displacements associated with enhanced oil recovery provides the motivation for this study. The observation of apparently linear dependence of flow rates upon pressure gradients during multiphase flow through porous media conceals the true nature of displacement phenomena such as Haine's jumps, droplet break-up, coalescence, etc. Most of these phenomena are understood only qualitatively. This study is on attempt to quantitatively describe them for a specific idealized pore geometry using approximate quasi steady-state calculations. The progress of a non-wetting oil droplet down a periodically convergent-divergent pore, the basic unit of which is a truncated bicone, shows a fluctuating, piecewise continuous track that resembles Haine's jumps. In addition to Haine's jumps, variations in the motion of droplets may also occur due to their break-up, coolescence or the instability of their interfacial configurations. Different parts of a droplet may be required to adjust to different curvatures and sometimes it may fail to maintain a constant mean curvature throughout its interface. Consequently, while flowing through constrictions, a droplet may break-up. Some portions of broken droplets may then travel in the middle of the pore and sometimes may coalesce with each other in different portions of the pore. The droplets become immobilized whevener the pressure gradients available across them are insufficient to overcome the threshold pressure offered by their interfaces. Possible implications of these phenomena in the entrapment of residual oil, hystereses in capillary pressure and relative permeability curves, and fluctuations in the multiphase flovv of fluids through porous media are discussed. <br> Le besoin de comprendre les divers mécanismes régissant les déplacements de certains fluides par d'autres, déplacements rencontrés dans la récupération assistée du pétrole, constitue la motivation de cet article. L'observation de la relation apparemment linéaire entre débits et gradients de pression dans un écoulement polyphasique en milieu poreux, dissimule la vraie nature des phénomènes de déplacement tels que l'écoulement discontinu de Haine, la rupture et la fusion des gouttelettes, etc. La plupart de ces phénomènes ne sont connus que qualitativement. La présente étude constitue une tentative de les décrire quantitativement à partir des calculs approchés admettant un régime quasi stationnaire et pour le cas d'un pore ayant une géométrie idéale donnée. La progression d'une gouttelette d'huile non mouillante le long d'un pore périodiquement convergent-divergent dont l'unité de base est un bicône tronqué, se présente sous un cheminement fluctuant, continu par morceaux et ressemblant à l'écoulement discontinu de Haine. En plus de cet écoulement discontinu, des variations dans le déplacement des gouttelettes peuvent également se produire à cause de leur fragmentation, de leur coalescence ou de l'instabilité de leur configuration interfaciale. Les différentes parties d'une gouttelette peuvent être nécessaires pour s'adapter à diverses courbures et il peut quelquefois arriver qu'elles ne puissent maintenir une courbure moyenne constante partout sur l'interface. Une gouttelette peut donc se fragmenter au passage des étranglements. Certaines parties de gouttelettes éclatées peuvent alors circuler au milieu du pore et parfois fusionner entre elles à certains endroits. Les gouttelettes s'immobilisent chaque fois que les gradients de pression disponibles à travers elles sont insuffisants pour surmonter la pression de seuil présentée par leurs interfaces. Les implications possibles de ces phénomènes dans le piégeage d'huile résiduelle, les hystérésis des courbes de pression capillaire et de perméabilités relatives, et les fluctuations dans les écoulements polyphasiques des fluides en milieu poreux, sont discutés

Mass transfer in liquid-phase epitaxy of two-layer systems

A liquid phase epitaxy diffusion model of a two-layer system at instable cooling speed of the solution-melt has been developed. It was discovered that the transition process continues even after the termination of cooling, due to which the layer growth continues as well. This effect is connected with to the hypothetical inertia of the diffusion process. The practical application of this phenomenon is shown

Investigation of Underground Sour Gas Storage in a Depleted Gas Reservoir

Underground Gas Storage (UGS) involves storage of large quantities of natural gas to support the natural gas demand in domestic, commercial and industrial areas. Storage of sour gas can be advantageous from economic standpoint, as it reduces treatment costs and increases the potential of production from shared reservoirs. This paper investigates feasibility of UGS in one of Iranian depleted fractured gas condensate reservoirs. Compositional simulation was employed to build dynamic reservoir model, develop the history matching phase of the reservoir and construct Injection/Withdrawal (I/W) cycles. One sweet gas stream and three sour gas streams with different compositions were tested for storage into reservoir during summer season. Results of simulation showed that presence of H2S and CO2 in the injected gas stream improves condensate production. Condensate Production Enhancement (CPE), defined as the percentage of condensate recovery increase due to sour gas injection relative to the sweet gas injection, was calculated for different compositions of storage gas. Also, Condensate Holding Ratio (CHR), defined as the ratio of condensate in the withdrawn sour gas to that in the withdrawn CH4, was estimated for different storage gas compositions. Results showed that CPE has a higher rate in earlier cycles and declines at later cycles. CHR is higher for sour gas storage compared to sweet gas. Furthermore, heating value of produced gas was calculated in all I/W cycles and compared with heating value of injected gas. It was indicated that difference between heating value of produced and injected gas increases with increase of H2S and CO2 content of the injected gas. Also, it was found that the reservoir has lower pressure rise at the end of I/W cycles in the case of underground sour gas storage compared to sweet gas storage. The presence of acid gas components decreases the z-factor of injected gas stream resulting in smaller difference between z-factors of injected gas and reservoir fluid

Optical and electrical properties of highly doped ZnO:Al films deposited by atomic layer deposition on Si substrates in visible and near infrared region

Optical properties of ZnO films doped by Al in the range 0.5 to 7 at.% and deposited by atomic layer deposition were studied in visible and infrared spectral range. Spectral dependences of film optical permittivity were modeled with the Lorentz-Drude approximation resulting in ZnO:Al plasma frequency and plasma damping parameters. We observed changing electron effective mass from 0.29m₀ to 0.5m₀ with increasing electron concentration in the range (0.9-4) × 10²⁰ due to the phenomenon of conduction band non-parabolicity. Comparing the results of optical and electrical investigations we can see that the main scattering mechanism is the scattering on grain boundaries (its contribution is about 60%)