## Abstract

The work presented in the papers is related to pore scale dynamics of two-phase flow in porous media. In the three first papers, a lattice Boltzmann method is applied in investigating the chosen systems. In the three last papers, oscillation stimulated two- phase flow systems have been investigated by means of the same numerical method, or through experiments. Paper 1: A direct comparison between a slow quasi-two-dimensional pore scale drainage experiment and a 2D lattice Boltzmann simulation is presented. An experimental porous medium consisting of approximately 10-by-10 pores is mapped onto the LB model. At a constant injection rate a non-wetting fluid slowly invades the porous medium filled with a wetting fluid. Capillary forces dominate the process and it is found to be in the capillary fingering regime. The LB method aims to simulate all the dynamics of the chosen fluids. It is here investigated how well a 2D LB simulation can mimic the dynamics of this slow invasion process. A direct visual comparison between the invasion front evolution of the invasion processes in the two systems is presented. By comparing the time evolution of the pressure difference between the two fluids, differences in the front dynamics of the experimental
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## Citation Formats

Aursjoe, Olav.
Two-phase flow in a porous medium stimulated by oscillations.
Norway: N. p.,
2010.
Web.

Aursjoe, Olav.
Two-phase flow in a porous medium stimulated by oscillations.
Norway.

Aursjoe, Olav.
2010.
"Two-phase flow in a porous medium stimulated by oscillations."
Norway.

@misc{etde_1010758,

title = {Two-phase flow in a porous medium stimulated by oscillations}

author = {Aursjoe, Olav}

abstractNote = {The work presented in the papers is related to pore scale dynamics of two-phase flow in porous media. In the three first papers, a lattice Boltzmann method is applied in investigating the chosen systems. In the three last papers, oscillation stimulated two- phase flow systems have been investigated by means of the same numerical method, or through experiments. Paper 1: A direct comparison between a slow quasi-two-dimensional pore scale drainage experiment and a 2D lattice Boltzmann simulation is presented. An experimental porous medium consisting of approximately 10-by-10 pores is mapped onto the LB model. At a constant injection rate a non-wetting fluid slowly invades the porous medium filled with a wetting fluid. Capillary forces dominate the process and it is found to be in the capillary fingering regime. The LB method aims to simulate all the dynamics of the chosen fluids. It is here investigated how well a 2D LB simulation can mimic the dynamics of this slow invasion process. A direct visual comparison between the invasion front evolution of the invasion processes in the two systems is presented. By comparing the time evolution of the pressure difference between the two fluids, differences in the front dynamics of the experimental and numerical systems are captured. The 2D LB simulation is found to reproduce the behavior and dynamics of the invasion process well. There are, however, some effects due to the three-dimensional topology of the experimental porous medium that the simulation is unable to produce. Paper 2: Pore scale effects on a two-phase flow undergoing seismic stimulation are studied numerically in 2D grain-pack geometries. A set of analytical criteria for successful mobilization of oil droplets stuck in pore cavities is presented. This set of criteria is tested by comparison to numerical results obtained from two-dimensional lattice Boltzmann simulations of small pore scale flow cells with periodic boundary conditions. The dynamics observed in these flow cells are taken to be representative for the typical flow dynamics encountered in the reservoir. To study the effect of seismic stimulation on oil reservoirs regarded to be nearly depleted, only one-third of the pore space in the flow cell is occupied by non-wetting oil droplets. Under the influence of an applied constant pressure gradient, all these oil droplets are left stuck or nearly stuck in the porous cell. It is found from the numerical simulations that applying an additional seismic stimulation will mobilize the trapped oil, thus increasing oil production, in good agreement with the analytical criteria presented. These results have also been published in a shortened and simplified form in the June 2009 issue of World Oil under the title Mechanisms of seismic EOR. Paper 3: A numerical study of the statistical behavior of a two-phase flow in a two-dimensional medium subjected to an oscillatory acceleration transverse to the overall direction of flow is presented. A viscous non-wetting fluid invades a porous medium filled with a more viscous wetting fluid. During the whole process sinusoidal oscillations of constant amplitude and frequency accelerates the porous medium sideways. The process displays a transient phase where defending fluid is removed from the porous medium, before it enters a state of irreducible wetting saturation where there is no net transport of defending fluid. The distribution of sizes of the remaining clusters in this state is observed to obey a power law with an exponential cutoff. The characteristic cutoff cluster size is found to be determined by the flow and oscillatory stimulation parameters. The end saturation of defending fluid is also found to be directly given by the cutoff cluster size. Paper 4: The effects of vibrational stimulation of a primary drainage process in a horizontal quasi-two-dimensional porous medium are experimentally investigated. The porous model is exposed to horizontal oscillations of fixed acceleration and frequency while an incompressible wetting fluid is withdrawn from the porous medium at a constant and low flow rate. The low extraction speed keeps the background flow in the capillary regime. The vibrational stimulation is applied independently in the direction of the background flow and perpendicular to it. The effect of the stimulation is observed in general to depend on the chosen acceleration amplitude, frequency, and orientation of the oscillations. When the stimulation is applied parallel to the average background flow, both the frequency and acceleration amplitude are influential with regards to the observed morphological changes in the invasion structure. In the cases where the oscillations of the system are directed perpendicular to the background flow direction, the effects are observed to apparently be independent of the applied frequencies and only depend on the acceleration amplitudes of the oscillations. (Author)}

place = {Norway}

year = {2010}

month = {Jan}

}

title = {Two-phase flow in a porous medium stimulated by oscillations}

author = {Aursjoe, Olav}

abstractNote = {The work presented in the papers is related to pore scale dynamics of two-phase flow in porous media. In the three first papers, a lattice Boltzmann method is applied in investigating the chosen systems. In the three last papers, oscillation stimulated two- phase flow systems have been investigated by means of the same numerical method, or through experiments. Paper 1: A direct comparison between a slow quasi-two-dimensional pore scale drainage experiment and a 2D lattice Boltzmann simulation is presented. An experimental porous medium consisting of approximately 10-by-10 pores is mapped onto the LB model. At a constant injection rate a non-wetting fluid slowly invades the porous medium filled with a wetting fluid. Capillary forces dominate the process and it is found to be in the capillary fingering regime. The LB method aims to simulate all the dynamics of the chosen fluids. It is here investigated how well a 2D LB simulation can mimic the dynamics of this slow invasion process. A direct visual comparison between the invasion front evolution of the invasion processes in the two systems is presented. By comparing the time evolution of the pressure difference between the two fluids, differences in the front dynamics of the experimental and numerical systems are captured. The 2D LB simulation is found to reproduce the behavior and dynamics of the invasion process well. There are, however, some effects due to the three-dimensional topology of the experimental porous medium that the simulation is unable to produce. Paper 2: Pore scale effects on a two-phase flow undergoing seismic stimulation are studied numerically in 2D grain-pack geometries. A set of analytical criteria for successful mobilization of oil droplets stuck in pore cavities is presented. This set of criteria is tested by comparison to numerical results obtained from two-dimensional lattice Boltzmann simulations of small pore scale flow cells with periodic boundary conditions. The dynamics observed in these flow cells are taken to be representative for the typical flow dynamics encountered in the reservoir. To study the effect of seismic stimulation on oil reservoirs regarded to be nearly depleted, only one-third of the pore space in the flow cell is occupied by non-wetting oil droplets. Under the influence of an applied constant pressure gradient, all these oil droplets are left stuck or nearly stuck in the porous cell. It is found from the numerical simulations that applying an additional seismic stimulation will mobilize the trapped oil, thus increasing oil production, in good agreement with the analytical criteria presented. These results have also been published in a shortened and simplified form in the June 2009 issue of World Oil under the title Mechanisms of seismic EOR. Paper 3: A numerical study of the statistical behavior of a two-phase flow in a two-dimensional medium subjected to an oscillatory acceleration transverse to the overall direction of flow is presented. A viscous non-wetting fluid invades a porous medium filled with a more viscous wetting fluid. During the whole process sinusoidal oscillations of constant amplitude and frequency accelerates the porous medium sideways. The process displays a transient phase where defending fluid is removed from the porous medium, before it enters a state of irreducible wetting saturation where there is no net transport of defending fluid. The distribution of sizes of the remaining clusters in this state is observed to obey a power law with an exponential cutoff. The characteristic cutoff cluster size is found to be determined by the flow and oscillatory stimulation parameters. The end saturation of defending fluid is also found to be directly given by the cutoff cluster size. Paper 4: The effects of vibrational stimulation of a primary drainage process in a horizontal quasi-two-dimensional porous medium are experimentally investigated. The porous model is exposed to horizontal oscillations of fixed acceleration and frequency while an incompressible wetting fluid is withdrawn from the porous medium at a constant and low flow rate. The low extraction speed keeps the background flow in the capillary regime. The vibrational stimulation is applied independently in the direction of the background flow and perpendicular to it. The effect of the stimulation is observed in general to depend on the chosen acceleration amplitude, frequency, and orientation of the oscillations. When the stimulation is applied parallel to the average background flow, both the frequency and acceleration amplitude are influential with regards to the observed morphological changes in the invasion structure. In the cases where the oscillations of the system are directed perpendicular to the background flow direction, the effects are observed to apparently be independent of the applied frequencies and only depend on the acceleration amplitudes of the oscillations. (Author)}

place = {Norway}

year = {2010}

month = {Jan}

}