High-temperature surfactant foams are simulated by modifying gas-phase mobility in a conventional thermal simulator. Both surfactant-alternating-gas (SAG) and gaslliquid-coinjection processes are modeled. Foam generation by leave-behind and snap-off as well as foam coalescence and trapping mechanisms are incorporated in the model by an equation for the number density of foam bubbles; gas-phase relative permeability and apparent viscosity are modified according to the bubble density. Pressure and saturation data of laboratory corefloods are successfully history matched with simulation results. Field-scale sensitivity studies of the steam-foamdrive process demonstrate how the coalescence rate affects the extent of steam diversion. IntroductionGases (such as steam, CO 2 , and nitrogen) are injected into oil reservoirs as drive fluids in some EOR processes. Early gas breakthrough can occur at producing wells owing to override and channeling, resulting in low oil-recovery efficiency. Injecting surfactant to create foam can reduce gas mobility and improve volumetric sweep efficiency in oil reservoirs. Foams used in both mature and infant steamdrives have resulted in incremental oil production in California heavy-oil reservoirs. 1-4The behavior of foam in porous media is complex, and the mechanisms governing its flow are not yet fully understood. Laboratory and theoretical studies have investigated foam generation,5-7 bubble coalescence,8 and the effect of oil on foam stability. 9, 10 A few investigators have begun to develop a comprehensive model of foam flow in porous media, but only few experiments have been modeled. 6, II, 12This paper offers a mathematical model that includes the principal mechanisms that govern foam displacement in porous media. The effect of foam on gas-phase relative permeability and apparent viscosity is included in the model. Both static or continuousgas foams and "strong" or discontinuous-gas foams are modeled. 5 ,6 In the first case, static foam lamellae block pore throats for gas flow, decreasing the gas-phase relative permeability. In the second case, foam bubbles are displaced through the pore network and the flow behavior is controlled by the rheology and the generation, trapping, and coalescence of the flowing foam bubbles. As proposed by Falls et al. 6 and Patzek, II an equation is incorporated to calculate the flowing-foam-bubble density, which, in turn, dictates how the flowing-foam mobility is modified.Chaser SD1OOO™, a surfactant developed for steam-foam applications, was the sole chemical used in this study. Model parameters are obtained from corefloods and by history matching nitrogen foam floods in Berea sandstone cores. Two laboratory corefloods are compared to simulations with the chosen parameters. Field-scale simulations of the steam-foam-drive process are then presented for a range of bubble coalescence rates.

This paper describes a model for numerically simulating themal recovery processes, The primary focus is on the simulation of in-situ combustion, but the formulation also represents /ire-and-water flooding, steam/looding, hot water flooding, steam stimulation, and spontaneous ignition as well. The simu Iator describes the flow of water, oil, and gas, and includes gravity and capillary effects. Heat tran.r/er by conduction, convection, and vaporization-conden~a~ion of both water and hydrocarbons are included. The rigorous but general nature of the simulator is obtained by employing conservation balance equations for . oxygen, inert gases, a Iigbt hydrocarbon pseudocomponent, a heavy hydrocarbon. pseudo component, water, coke, and energy. Vaporization-condensation is governed by vaporliquid equilibrium using temperature and pressure-dependent equilibrium coefficients. Four chemical reactions are -accounted for: formation of coke from the heavy hydroctirbon component and the oxidation of coke and botb heavy and light hydrocarbon components. Formulation details, numerical solution procedures, and computational results are pr~sented. The computational results include both one-and two-dimensional cross-sectional studies. The simulator represents a major improvement in the ability to simulate thermal recovery processes urder complex conditions. P G9 P Cw %? %? Sw Sw Pg, T, Y5

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractEnsemble Kalman Filter (EnKF) has been reported to be very efficient for real-time updating of reservoir model to match the most current production data. Using EnKF, an ensemble of reservoir models assimilating the most current observations of production data are always available. Thus the estimations of reservoir model parameters, and their associated uncertainty, as well as the forecasts are always up-to-date.In this paper, we apply the EnKF for continuously updating an ensemble of permeability models to match realtime multiphase production data. We improve the previously EnKF by resolving the flow equations after Kalman filter updating so that the updated static and dynamic parameters are always consistent. By doing so, we show that the production data are also better matched for some cases. We investigate the sensitivity of using different number of realizations in the EnKF. Our results show that a relatively large number of realizations are needed to obtain stable results, particularly for the reliable assessment of uncertainty. The sensitivity of using different covariance functions is also investigated.The efficiency and robustness of EnKF is clearly demonstrated using an example. By assimilating more production data, new features of heterogeneity in reservoir model can be revealed with reduced uncertainty, resulting in more accurate predictions.

Active flow control for aerofoils has been proven to be an effective way to improve the aerodynamic performance of aircraft. A conceptual hybrid design with surfaces embedded with Shape-Memory Alloy (SMA) and trailing Macro Fibre Composites (MFC) is proposed to implement active flow control for aerofoils. A Computational Fluid Dynamics (CFD) model has been built to explore the feasibility and potential performance of the proposed conceptual hybrid design. Accordingly, numerical analysis is carried out to investigate the unsteady flow characteristics by dynamic morphing rather than using classical static simulations and complicated coupling. The results show that camber growth by SMA action could cause an evident rise of Cl and Cd in the take-off/landing phases when the Angle-of-Attack (AoA) is less than 10°. The transient tail vibration behaviour in the cruise period when using MFC actuators is studied over wide ranges of frequency, AoA and vibration amplitude. The buffet frequency is locked in by the vibration frequency, and a decrease of 1.66–2.32% in Cd can be achieved by using a proper vibration frequency and amplitude.