Session K17: Porous Media Flows: Displacement of Immiscible Fluids (8:45am - 9:30am CST)

Using colloidal deposition to mobilize immiscible fluids from porous media

Nanoparticles are thought to enhance immiscible fluid mobilization from porous media primarily through interactions at fluid interfaces that decrease interfacial energy. Most studies focus on optimizing the transport of these particles to prevent them from depositing onto solid surfaces in a porous medium because deposition is broadly linked with clogging and unfavorable permeability reduction characteristics that prevent flow through the pore space. We investigate how controlled permeability reduction of a three-dimensional porous medium plays a surprisingly positive role in mobilizing trapped oil using confocal microscopy of a transparent, 3D porous medium. We find that nanoparticle deposition results in a large decrease in the amount of oil that remains trapped in the porous medium and expand upon an existing framework to quantify how this reduction in permeability changes the geometric properties of the medium and flow through it. Importantly, our results thus show that slightly reducing the permeability of a porous medium can be beneficial, presenting a new method of mobilizing immiscible fluids from a porous medium.   

Cooperative mobilization of emulsion droplets in porous media

Immiscible displacement in porous media is a fascinating problem encountered daily in oil recovery and soil remediation. Droplets of oil stabilized by a surfactant, naturally present in crude oil, resist merging while trapped in porous media, which results in unexpected dynamics. We study the cooperative dynamics of monodisperse droplets in 2D porous media, both experimentally using confocal microscopy and computationally using COMSOL. By probing the dynamics of the carrier fluid at pore level and tracking the mobilization of droplets, we find that upon arrival or mobilization of one droplet, large pressure fluctuations emerge across neighboring pores. The pressure fluctuations result in cooperative mobilization of droplets. Moreover, a pile up of droplets in one area results in reduction of viscous pressure across all droplets by diverting the flow in unoccupied pores. However, the pile up is extremely unstable and droplets easily slide out of the pile with small fluctuations in velocities of the neighboring pores. The correlation length of the mobilized single droplets remain of the order of a few pores while a pile of droplets result in an increased correlation length.   

Low-pressure driven displacement of gas-fluid-gas plugs in a capillary tube

This talk focuses on experiments conducted to study the effects of low-pressure driven displacement of liquid plugs in a capillary tube. Experiments were performed in a capillary tube (diameter $\approx$ 800 $\mu$m) by displacing liquid plugs containing aqueous glycerol solution using pressurized air with a range of 0.02 psig $\leq$ $P$ $\leq$ 0.1 psig (at an increment of 0.01 psig). Two CCD cameras placed in front of the set-up captured the displaced and displacing fluid interfaces simultaneously. At these low pressures, we categorized the flow behavior as following: $1)$ At the lowest pressure, displacement of fluid plug becomes stationary after a certain time, $2)$ With further increase in pressure, the residual film of the displaced fluid deforms into drops along the tube walls, and $3)$ At the highest pressure, a flat and thin film was left behind by the displaced fluid. Subsequently, we measure the fluid fraction left in the tube using the expression $m=1-U_m/U_t$, where the mean ($U_m$) and tip ($U_t$) velocities were measured by analyzing the experimental data using an in-house MATLAB code. We report the $m$ versus $Ca$ trends observed in our experiments and compare them against classical results for immiscible fluid displacement.   

Permeability modification and scaling of flow velocities in porous media

Permeability modifications and conformance control in porous media have an essential role in applications such as prevention of bioclogging in water filters and oil recovery. We use confocal microscopy and bulk transport measurements to probe the local flow and permeability of the medium in 3D porous micromodels. Using two different methods, we modify the available network of pores to reduce permeability and probe the local flow: 1) polymer retention and 2) immiscible trapping. We find that the average flow velocities scale with permeability and poorly with porosity. These methods of permeability reduction are dynamically modifying the permeability and are dictated by the network of pores. Furthermore, the distribution of velocities retain the same shape after considerable reduction in permeability in polymer retention but not in immiscible trapping. This is because of the gradual change in permeability in polymer retention.   

An Experimental Study of Capillary Pressure Hysteresis in Two-Phase Flow in 2D Porous Micromodels

Multiphase flow in porous media occurs naturally in many environmental and industrial systems. A comprehensive understanding of the fundamental flow physics in such systems is essential. For an isothermal two-phase flow in porous media, traditional models often use constitutive relations of capillary pressure as a function of saturation, which exhibit hysteresis. Recently it has been theoretically shown that a unique state equation is possible by adding a few variables in the functional form, which is hysteresis-free and works for both equilibrium and dynamic conditions. However, experiments are needed to validate and further develop the theories. Micromodel is a powerful tool to perform such studies as it offers excellent optical access and control over pore properties. Employing fluorescence microscopy and high-speed imaging, pore flow and its dynamics are captured and investigated. Herein I will be trying to delineate techniques for 2D micromodel fabrication and measurements of capillary pressure, interfacial area, and Euler Characteristic, thus providing a general method for 2D micromodel validation of novel theories regarding hysteresis. The results will provide new insight into the hysteretic behavior of capillary pressure as well as validations of new functional forms.   

Intermittency effects in multi-phase flows and anomalous in heterogeneous porous media

Multi-phase flow and transport in porous media is prevalent in a wide range of challenging fluid mechanics problems in sustainability, energy, and the environment. The small- or pore-scale study of such flows’ spatial and temporal evolution can impact flow behavior at system scales in a nontrivial manner. Therefore, the underlying physics of the spreading, mixing, and interfacial processes at these very small scales must be understood for the development of accurate system-scale prediction models of transport in multi-phase flow systems. We present results from a coordinated numerical and experimental study of intermittency effects over a range of viscous and inertial flow regimes in single- and multi-phase flows in 2D heterogeneous micromodels to quantify Lagrangian flow statistics to better inform pore-scale models. The applicability of different modeling frameworks such as the correlated-continuous time random walk is tested by studying statistics of particle trajectories obtained by particle tracking velocimetry measurements and Lattice Boltzmann simulations from single- and multi-phase flows. The results make particular note of the presence of trapped ganglia, the influence of the pore Reynolds number, and inertial effects on intermittency, and compare these effects.