Deals with specialized but interrelated problems in oil recovery in which the effect of interfacial behaviors is the dominant factor. Describes approaches to improving the understanding of the fundamentals of displacement, with the goal of simplifying systems sufficiently to enable measurements and

This paper is concerned with the behavior of foam in porous media at the pore level. Identical, heterogeneous silicon micromodels, two dimensionally etched to replicate flow in Berea Sandstone, were used. The models, already saturated with varying concentrations of surfactant and, at times, oil were invaded with air. Visual observations were made of these air displacement events in an effort to determine foam flow characteristics with varying surfactant concentrations, and differing surfactants in the presence of oil. These displacement events were recorded on video tape. These tapes are available at the Stanford University Petroleum Research Institute, Stanford, California. The observed air flow characteristics can be broadly classified into two: continuous and discontinuous. Continuous air flow was observed in two phase runs when the micromodel contained no aqueous surfactant solution. Air followed a tortuous path to the outlet, splitting and reconnecting around grains, isolating water located in dead-end or circumvented pores, all without breaking and forming bubbles. No foam was created. Discontinuous air flow occurred in runs containing surfactant - with smaller bubble sizes appearing with higher surfactant concentrations. Air moved through the medium by way of modified bubble train flow where bubbles travel through pore throats and tend to reside more statically in larger pore bodies until enough force is applied to move them along. The lamellae were stable, and breaking and reforming events by liquid drainage and corner flow were observed in higher surfactant concentrations. However, the classic snap-off process, as described by Roof (1973) was not seen at all.

Foam in porous media is a fascinating fluid both because of its unique microstructure and because its dramatic influence on the flow of gas and liquid. A wealth of information is now compiled in the literature describing foam generation, destruction, and transport mechanisms. Yet there are conflicting views of these mechanisms and on the macroscopic results they produce. By critically reviewing how surfactant formulation and porous media topology conspire to control foam texture and flow resistance, we attempt to unify the disparate viewpoints. Evolution of texture during foam displacement is quantified by a population balance on bubble concentration, which is designed specifically for convenient incorporation into a standard reservoir simulator. Theories for the dominant bubble generation and coalescence mechanisms provide physically based rate expressions for the proposed population balance. Stone-type relative permeability functions along with the texture-sensitive and shear-thinning nature of confined foam complete the model. Quite good agreement is found between theory and new experiments for transient foam displacement in linear cores.

A three-dimensional fully parallel particle-based model for direct pore-level simulation of incompressible viscous fluid flow in disordered porous media is presented. The model is capable of simulating flow in porous media, taking directly as input three-dimensional high-resolution microtomography images of naturally-occurring or man-made porous systems. These images provide the most faithful representations of the pore space in the porous medium. In this method, the entire medium, i.e., solid and fluid, is discretized using particles. The model is based on the Moving Particle Semi-implicit (MPS) technique and modified to improve its stability. The model handles highly irregular fluid-solid boundaries effectively, accounts for viscous pressure drop in addition to gravity forces, conserves mass, and can automatically detect any false connectivities with fluid particles in the neighboring pores and throats. The model also includes a sophisticated algorithm to automatically split and merge fluid particles to maintain hydraulic connectivity of extremely narrow conduits. Finally, it uses novel methods to handle particle inconsistencies and open boundaries. To handle the computational load, a fully parallel version of the model is presented that runs on distributed memory computer clusters and exhibits excellent scalability. The accuracy and reliability of the model in predicting the true flow in porous systems was validated rigorously against analytical, numerical, and experimental data available in the literature. The validated model was then used to simulate flow in naturally-occurring sandstones to compute their absolute permeabilities and their variations with sample size and flow direction. The model was extended to handle the pore-level transport of solutes in random porous media. Two different sandstones possessing different topologies were used to investigate pre-asymptotic and asymptotic longitudinal dispersion coefficients, the impact of pore-scale topologies on the transient behavior of convective-diffusive solute transport at the pore-level, and the impact of inertial forces on dispersion coefficients at very high Peclet numbers. The asymptotic dispersion coefficients were then successfully compared against the experimental data available in the literature for a wide range of Peclet number. Furthermore, a solute adsorption module was developed and integrated with the model allowing us to study the adsorptive-diffusive-convective solute transport in a rough-walled single fracture. These studies provide new insights into the pore-scale behavior of fluid flow and solute transport in random porous media. The model serves as a reliable platform for studies of different pore-level phenomena that can improve our understanding of the pore-level physics of flow and transport.