Pore-filling events in single junction micro-models with corresponding lattice Boltzmann simulations

Abstract

The aim of this work is to better understand fluid displacement mechanisms at the pore scale in relation to capillary-filling rules. Using specifically designed micro-models we investigate the role of pore body shape on fluid displacement during drainage and imbibition via quasi-static and spontaneous experiments at ambient conditions. The experimental results are directly compared to lattice Boltzmann (LB) simulations. The critical pore-filling pressures for the quasi-static experiments agree well with those predicted by the Young-Laplace equation and follow the expected filling events. However, the spontaneous imbibition experimental results differ from those predicted by the Young-Laplace equation; instead of entering the narrowest available downstream throat the wetting phase enters an adjacent throat first. Thus, pore geometry plays a vital role as it becomes the main deciding factor in the displacement pathways. Current pore network models used to predict displacement at the field scale may need to be revised as they currently use the filling rules proposed by Lenormand et al. (J. Fluid Mech., vol. 135, 1983, pp. 337-353). Energy balance arguments are particularly insightful in understanding the aspects affecting capillary-filling rules. Moreover, simulation results on spontaneous imbibition, in excellent agreement with theoretical predictions, reveal that the capillary number itself is not sufficient to characterise the two phase flow. The Ohnesorge number, which gives the relative importance of viscous forces over inertial and capillary forces, is required to fully describe the fluid flow, along with the viscosity ratio.

The Role of Disjoining Pressure and Thermal Activation in the Invasion of Droplets into Nanopores

“…Hence, as the droplet enters the pore, a thin residual water film remains on the pore wall, which reduces the pore to an effective width W eff . We note that such thin water films, akin to the precursor film in front of a droplet spreading on a hydrophilic surface, 19 are observed both in prior studies of bubbles/droplets entering pores with strongly hydrophilic walls (e.g., mica) 20−22 and in our MD simulations (see below).…”

Energy Conversion Reveals Regime Transition of Imbibition in a Rough Fracture

“…where E k is the kinetic energy, , v is the velocity vector, Φ is the energy dissipation rate, Φ > 0, P is the power by the external forces, P = Δ p ( t ) Q , and d F is the change in surface energy, expressed as (Ferrari & Lunati, ; Zacharoudiou et al, ) where A nw is the fluid‐fluid interfacial area, A ws is the wetting phase‐solid phase interfacial area, and θ is the static contact angle.…”

“…Since energy balance is independent of system size and flow geometry, it offers a rigorous way for identification of the transitions between the two regimes. Energy conversion and dissipation have been investigated by experiments (Morrow, 1970;Schlüter et al, 2017;Seth & Morrow, 2006) and simulations (Ferrari & Lunati, 2014;Helland et al, 2017;Zacharoudiou et al, 2017). In a pioneering experimental work, Morrow (1970) discussed the energy conversion between surface energy and external work, indicating that during capillary imbibition, only part of surface energy can be converted into external work and the rest is dissipated.…”

“…where E k is the kinetic energy, E k ¼ ∫ Ω 1 2 ρv·vdΩ > 0, v is the velocity vector, Φ is the energy dissipation rate, Φ > 0, P is the power by the external forces, P = Δp(t)Q, and dF is the change in surface energy, expressed as (Ferrari & Lunati, 2014;Zacharoudiou et al, 2017) dF ¼ σ dA nw À cosθdA ws ð Þ…”

Coupled supercritical CO2 dissolution and water flow in pore-scale micromodels

“…Longer residence time with lower imbibition rates allows for longer contact between scCO 2 and mobile water that is available for dissolution and mass transfer. In addition, because of the water-wet silica surface, water flow may occur as thin film along the surface of the silica posts (Zhao et al, 2016;Zacharoudiou et al, 2017;Hu et al, 2018). The swelling of water films was investigated as a slow diffusion process driven by capillary pressure at localities (Nguyen et al, 2006), i.e., with the increase in water injection rate, the time for less effective in dissolving residual scCO 2 than that at a slower velocity and equilibrium scCO 2 dissolution may only occur in regional groundwater flow with a very small (close to zero) velocity (to be further discussed in Section 5).…”