Dynamics of snap-off and pore-filling events during two-phase fluid flow in permeable media

Abstract

Understanding the pore-scale dynamics of two-phase fluid flow in permeable media is important in many processes such as water infiltration in soils, oil recovery, and geo-sequestration of CO2. The two most important processes that compete during the displacement of a non-wetting fluid by a wetting fluid are pore-filling or piston-like displacement and snap-off; this latter process can lead to trapping of the non-wetting phase. We present a three-dimensional dynamic visualization study using fast synchrotron X-ray micro-tomography to provide new insights into these processes by conducting a time-resolved pore-by-pore analysis of the local curvature and capillary pressure. We show that the time-scales of interface movement and brine layer swelling leading to snap-off are several minutes, orders of magnitude slower than observed for Haines jumps in drainage. The local capillary pressure increases rapidly after snap-off as the trapped phase finds a position that is a new local energy minimum. However, the pressure change is less dramatic than that observed during drainage. We also show that the brine-oil interface jumps from pore-to-pore during imbibition at an approximately constant local capillary pressure, with an event size of the order of an average pore size, again much smaller than the large bursts seen during drainage.

Microfluidic Model Porous Media: Fabrication and Applications

“…Therefore, the individual particle velocities can be determined based on the individual particle displacements over the given time interval. Both PIV and PTV usually use fluorescent tracer particles and a high‐resolution microscope (such as a confocal laser scanning microscope) to visualize the particle motion; for 3D imaging, it is important to match the refractive index between the fluids and particles. The flow velocity field obtained using μ‐PIV from 2D silicon‐based micromodel with an array of pillars by deep reactive ion etching and 3D glass bead‐packed micromodels is shown in Figure .…”

Direct Measurement of Static and Dynamic Contact Angles Using a Random Micromodel Considering Geological CO2 Sequestration

“…In capillary or residual trapping, CO 2 bubbles are entrapped inside rock pores by three mechanisms: (1) snap-off, (2) dead-end, and (3) by-passing. In snap-off, when water is invaded into a water-wet media, the water in the corner of a throat will swell gradually until it disconnects the non-wetting phase in the throat and forcibly pushes non-wetting into pore bodies [60,61]. The snap-off trapping mechanism is dominant for water-wet rocks with a high aspect ratio of pore-body diameter to pore-throat diameter [62].…”

Evaporation with the formation of chains of liquid bridges

“…As an example, the width of the most external liquid bridge along a film is plotted as a function of time in figure 10: it decreases continuously with time until the break-up suddenly occurs, between t = 25 and t = 26 s. Studying in detail the dynamics of the non-local fluid redistribution within the liquid cluster following a pore invasion or of the liquid bridge break-up is not within the scope of the present study. Such topics have been considered in recent studies, using micromodels (Armstrong & Berg 2013) or packing of beads (Singh et al 2017a). On figure 8(b), the solid line shows the evolution of the liquid film ends as a function of the main menisci locations, averaged over the 28 spirals of the micromodel (so 28 liquid film-main meniscus pairs).…”