Pore‐scale and continuum modeling of gas flow pattern obtained by high‐resolution optical bench‐scale experiments

Abstract

[1] High-resolution optical bench-scale experiments were conducted in order to investigate local gas flow pattern and integral flow properties caused by point-like gas injection into water-saturated glass beads. The main goal of this study was to test the validity of the continuum approach for two-fluid flow in macroscopic homogeneous media. Analyzing the steady state experimental gas flow pattern that satisfies the necessary coherence condition by image processing and calibrating the optical gas distribution by the gravimetrical gas saturation, it was found that a pulse-like function yields the best fit for the lateral gas saturation profile. This strange behavior of a relatively sharp saturation transition is in contradiction to the widely anticipated picture of a smooth Gaussian-like transition, which is obtained by the continuum approach. This transition is caused by the channelized flow structure, and it turns out that only a narrow range of capillary pressure is realized by the system, whereas the continuum approach assumes that within the representative elementary volume the whole spectrum of capillary pressures can be realized. It was found that the stochastical hypothesis proposed by Selker et al. (2007) that bridges pore scale and continuum scale is supported by the experiments. In order to study channelized gas flow on the pore scale, a variational treatment, which minimizes the free energy of an undulating capillary, was carried out. On the basis of thermodynamical arguments the geometric form of a microcapillary, macrochannel formation and a length-scale-dependent transition in gas flow pattern from coherent to incoherent flow are discussed.

The effect of spontaneous gas expansion and mobilization on the aqueous-phase concentrations above a dense non-aqueous phase liquid pool

“…It is not capable of simulating the extensive expansion and mobilization [3] that is characteristic of spontaneous expansion above DNAPL pools. The inability of continuum-based numerical models such as this to simulate the processes that control the unstable flow of non-wetting fluids in porous media has been previously recognized [12,15,18,29]. Therefore, the expansion to adjacent grid blocks within the model, as well as the fragmentation and mobilization of gas clusters, was simulated using macroscopic invasion percolation (IP) techniques [20,[30][31][32][33][34], with modifications for IP in a gravity gradient [33,35] and migration and fragmentation of the invading gas phase [19][20][21].…”

The impact of pore structure and surface roughness on capillary trapping for 2‐D and 3‐D porous media: Comparison with percolation theory

“…For CCS technology (CCS—carbon capture and storage), capillary trapping is one of the relevant storage processes [ Juanes et al ., ; Iglauer et al ., , ]. Achieving homogeneous distribution of trapped oxygen gas bubbles and/or mobilization of trapped residual NAPL‐blobs (NAPL—nonaqueous phase liquid) is still a challenge in the remediation of contaminated groundwater [ Johnson et al ., ; Jeong and Corapcioglu , ; Kaoa et al ., ; Geistlinger et al ., ]. The effectiveness of oil recovery will depend on how many isolated oil blobs remain in the porous matrix after water flooding [ Chatzis et al ., ; Iglauer et al ., ].…”

Microbubble transport in water‐saturated porous media

“…When gas is transported continuously, channel flow may occur. Experiments and numerical simulations have been carried out to investigate the radius of influence area and contaminant removal rate under the condition of channel flow [Geistlinger et al, 2009;Forsyth, 1993;Forsyth and Shao, 1991;McCray, 2000;Thomson and Johnson, 2000]. However, gas channels might not be necessarily stable.…”