-The great difference in density between steam and liquid during wet steam injection always results in steam override, that is, steam gathers on the top of the pay zone. In this article, the equation for steam override coefficient was firstly established based on van Lookeren's steam override theory and then radius of steam zone and hot fluid zone were derived according to a more realistic temperature distribution and an energy balance in the pay zone. On this basis, the equation for the reservoir heat efficiency with the consideration of steam override was developed. Next, predicted results of the new model were compared with these of another analytical model and CMG STARS (a mature commercial reservoir numerical simulator) to verify the accuracy of the new mathematical model. Finally, based on the validated model, we analyzed the effects of injection rate, steam quality and reservoir thickness on the reservoir heat efficiency. The results show that the new model can be simplified to the classic model (Marx-Langenheim model) under the condition of the steam override being not taken into account, which means the Marx-Langenheim model is corresponding to a special case of this new model. The new model is much closer to the actual situation compared to the Marx-Langenheim model because of considering steam override. Moreover, with the help of the new model, it is found that the reservoir heat efficiency is not much affected by injection rate and steam quality but significantly influenced by reservoir thickness, and to ensure that the reservoir can be heated effectively, the reservoir thickness should not be too small.Résumé -Un modèle amélioré d'injection de vapeur prenant en compte la surcharge de vapeur -La différence de densité entre la vapeur et le liquide lors de l'injection de vapeur humide conduit toujours à un débordement de vapeur, en d'autres termes, la vapeur s'accumule sur le dessus de la zone de production. Dans cet article, l'équation pour le coefficient de surcharge de vapeur a d'abord été établie sur la base de la théorie de la surcharge de vapeur de van Lookeren, puis le rayon de la zone de vapeur et la zone de fluide chaud ont été dérivés selon une distribution de température plus réaliste et un bilan énergétique dans la zone de production. Sur cette base, l'équation d'efficacité thermique du réservoir en tenant compte de la surpression de la vapeur d'eau a été développée. Par la suite, les résultats prévus par le nouveau modèle ont été comparés à ceux d'un autre modèle analytique et à CMG STARS (un simulateur numérique à réservoir commercial reconnu) pour vérifier la précision du nouveau modèle mathématique. Enfin, sur la base du modèle validé, nous avons analysé les effets du taux d'injection, de la qualité de la vapeur et de la densité du réservoir sur l'efficacité thermique du réservoir. Les résultats montrent que le nouveau modèle peut être simplifié par rapport au modèle classique (modèle de Marx-Langenheim) à condition que la 2017 DOI: 10.2516 This is an Open Access article dist...
Fluids with different components were used in threshold pressure gradient (TPG) experiment by steady "pressure~velocity" method. Influence of Permeability and fluids components on TPG was analyzed. The study indicates different fluids give different TPG versus permeability power function, TPG of different fluids was as follows: Distilled water >Injected water >Formation water >Surfactant solution. Mechanism analysis of TPG reduction shows that higher salinity and Surfactant are favorable to TPG reduction, and it offers a theoretical explanation for injection of formation water and surfactant solution in the low permeability reservoir. The injection of the two fluids can decrease injection pressure and increase injection capacity for water wells.
As a crucial factor affecting water flooding in tight sandstone reservoirs, dynamic capillary pressure (DCP) has significant impact on the production performance during oil-water flow. In this work, a novel numerical simulation method with DCP is developed to study oil displacement in tight sandstone reservoirs. Based on this new model, the impacts from DCP to water/oil displacement (or water flooding effects) are analysed. The results of this work show that the effects brought by dynamic capillary pressure cannot be neglected. The more significant dynamic effects of capillary pressure correspond to the sample with lower permeability. The effect of DCP is probably a major contributor to non-linear flow (non-Darcy flow) in tight sandstone reservoirs during water flooding process. Compared with the conventional flow theory (e.g., static capillary pressure theory), our derived model with DCP can help to reduce the uncertainty in water/oil flow in tight sandstone reservoirs.
Horizontal wells have been applied in bottom-water reservoir since their advantages were found on distribution of linear dropdown near wellbore, higher critical production, and more OOIP (original oil in place) controlled. In the paper, one 3D visible physical model of horizontal physical model is designed and built to simulate the water cresting process during the horizontal well producing and find water breakthrough point in homogenous and heterogeneous reservoir with bottom water. Water cresting shape and water cut of horizontal well in between homogenous and heterogeneous reservoir are compared on the base of experiment’s result. The water cresting pattern of horizontal well in homogeneous reservoir can be summarized as “central breakthrough, lateral expansion, thorough flooding, and then flank uplifting.” Furthermore, a simple analysis model of horizontal well in bottom water reservoir is established and water breakthrough point is analyzed. It can be drawn from the analysis result that whether or not to consider the top and bottom border, breakthrough would be located in the middle of horizontal segment with equal flow velocity distribution.
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