Capillary-Dominated Fluid Displacement in Porous Media

Abstract

Liquid invasion into a porous medium is a phenomenon of great importance in both nature and technology. Despite its enormous importance, there is a surprisingly sparse understanding of the processes occurring on the scale of individual pores and of how these processes determine the global invasion pattern. In particular, the exact influence of the wettability remains unclear besides the limiting cases of very small or very large contact angles of the invading fluid. Most quantitative pore-scale experiments and theoretical considerations have been conducted in effectively two-dimensional (2D) micromodels and Hele–Shaw geometries. Although these pioneering works helped to unravel some of the physical aspects of the displacement processes, the relevance of 2D models has not always been appreciated for natural porous media. With the availability of X-ray microtomography, 3D imaging has become a standard for exploring pore-scale processes in porous media. Applying advanced postprocessing routines and synchrotron microtomography, researchers can image even slow flow processes in real time and extract relevant material parameters like the contact angle from the interfaces in the pore space. These advances are expected to boost both theoretical and experimental understanding of pore-scale processes in natural porous media.

Review of Microfluidic Devices and Imaging Techniques for Fluid Flow Study in Porous Geomaterials

“…Therefore, it has a very wide range of applications, including medical science, biology, earth science, material science and many other areas [ 209 , 210 , 211 ]. Characterization of pore shape and structure [ 12 , 212 , 213 , 214 ], saturation distribution [ 200 , 215 , 216 , 217 , 218 , 219 ], fluid flow mechanisms, soil deformation [ 220 ], and reactive transport [ 221 ] have been some of the main applications of X-ray CT in geological and hydrological studies.…”

Local instabilities during capillary-dominated immiscible displacement in porous media

“…These pore-scale instabilities affect not only the distribution of fluids in the pore space, but also the displacement efficiency of the various fluids. However, current research achievements on local instabilities are mainly based on two-dimensional or threedimensional idealized porous media such as dense random arrangements of circular disks, monolayer spherical beads in 2D microfluidic experiments, monodisperse or polydisperse arrangement of glass beads in X-ray CT imaging experiments, or real porous media with relatively large pore spaces (Singh et al, 2019). In future, with the improvement of space-time resolution of CT scanning, the dynamical pore-scale flow mechanisms in real geological porous media with smaller pores and more complex structures will be studied.…”

Self-adaptive preferential flow control using displacing fluid with dispersed polymers in heterogeneous porous media

“…Preferential flow usually refers to a 'winner-takes-all' phenomenon of uneven fluid or solute transport in porous media, where the fluids prefer to travel through the low-resistance pathways rather than through other parts of the matrix. The frequent occurrence of this phenomenon has attracted much attention from biochemists, hydrologists, agriculturalists and geophysicists, for its close relevance to numerous practical issues, such as drug delivery in vascular networks (Kim, Park & Lee 2017;Jensen & Chernyavsky 2019), soil wetting (Homsy 1987;Valentine, Zhang & Robinson 2002;Šimůnek et al 2003;Good, Noone & Bowen 2015), enhanced oil recovery (EOR) (Payatakes 1982;Gerritsen & Durlofsky 2005;Thomas 2008;Zinchenko & Davis 2017;Singh et al 2019) and microfluidic logic control (Fuerstman, Garstecki & Whitesides 2007;Prakash & Gershenfeld 2007;Gasperino et al 2018). As opposed to uniform flow, preferential flow is one of the most unwelcome flow patterns during the above processes.…”

“…Extensive efforts have been made to understand the mechanism of this flow pattern from the large scale (Adler & Brenner 1988;Ritsema et al 1993;Khan et al 2016) down to the core-to-pore scale (Chen & Wilkinson 1985;Stokes et al 1986;Cueto-Felgueroso & Juanes 2008;Li et al 2009;Segre & Holtzman 2015;Holtzman 2016;Singh et al 2019). These results suggest that either applying to a more homogeneous matrix or providing more favourable flow conditions (e.g.…”