Ali Q. Raeini

Modelling two-phase flow in porous media at the pore scale using the volume-of-fluid method

We present a stable numerical scheme for modelling multiphase flow in porous media, where the characteristic size of the flow domain is of the order of microns to millimetres. The numerical method is developed for efficient modelling of multiphase flow in porous media with complex interface motion and irregular solid boundaries. The Navier-Stokes equations are discretised using a finite volume approach, while the volume-of-fluid method is used to capture the location of interfaces. Capillary forces are computed using a semi-sharp surface force model, in which the transition area for capillary pressure is effectively limited to one grid block. This new formulation along with two new filtering methods, developed for correcting capillary forces, permits simulations at very low capillary numbers and avoids non-physical velocities. Capillary forces are implemented using a semi-implicit formulation, which allows larger time step sizes at low capillary numbers. We verify the accuracy and stability of the numerical method on several test cases, which indicate the potential of the method to predict multiphase flow processes.

Numerical Modelling of Sub-pore Scale Events in Two-Phase Flow Through Porous Media

We use a new volume-of-fluid based finite-volume method to model two-phase flow through simple pore geometries and study the mechanisms controlling two-phase flow at the pore scale. The numerical model is used to study layer flow and snap-off, and investigate the effect of geometry and flow rate on trapping and mobilization of the disconnected ganglia. Furthermore, a new variable, the capillary field, is introduced to characterize the capillary force under dynamic situations, and a force-balance concept is presented to relate flow rates to pore-scale forces—dynamic pressure gradient and the capillary field. This description of the flow has the potential to be used in pore-network models to study the effect of pore-scale structures on the flow at larger scales. As an illustration of the applicability of this concept, we use the relations obtained from the numerical simulations to predict the threshold capillary number for blob mobilization during imbibition and show that this information can be used to reproduce the direct numerical simulation results accurately.

A Sensitivity Study of the Effect of Image Resolution on Predicted Petrophysical Properties

Micro-CT scanning is a nondestructive technique that can provide three-dimensional images of rock pore structure at a resolution of a few microns. We compute petrophysical properties on three-dimensional images of benchmark rocks: two sandstones (Berea and Doddington) and two limestones (Estaillades and Ketton). We take scans at a voxel size of approximately 2.7

A numerical model of two-phase flow at the micro-scale using the volume-of-fluid method

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Predictions of non-Fickian solute transport in different classes of porous media using direct simulation on pore-scale images.

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The impact of porous media heterogeneity on non-Darcy flow behaviour from pore-scale simulation

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