Critical capillary number: Desaturation studied with fast X‐ray computed microtomography

By Ryan T. Armstrong, A. Georgiadis, H. Ott, D. Klemin, S. Berg. 2014

168 citations recorded by the source corpus.

For subsurface flow, the correct definition for the balance of viscous and capillary forces, the so‐called capillary number (Ca), which predicts the mobilization of nonwetting phase, has been a long‐standing controversy. The most common microscopic definition results in nonwetting phase mobilization at Ca ~10−5, which is counterintuitive. Rather, mobilization should occur at Ca ≥ 1. As demonstrated herein, by using fast synchrotron‐based X‐ray computed microtomography and averaging of thereby accessible pore‐scale parameters to macroscale values, a macroscale Ca definition is validated and shown to correctly describe mobilization at Ca ~1. The presented methodology provides a connection between desaturation and pore‐scale fluid topology and gives insight into when and how Ca changes with system size. The broader implication implies that it makes a difference whether desaturation is driven by an increase in flow rate or viscosity or decrease in interfacial tension since Ca incorporates nonwetting phase cluster length, which is process‐dependent.

Subfields: Computational Mechanics, Environmental Engineering, Ocean Engineering

View Paper: https://www.semanticscholar.org/paper/de13fa1700ebe5a68fecc6d2895fc55232d099e9

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Computational Mechanics

In Environmental Engineering

In Ocean Engineering

Citations in the corpus

From connected pathway flow to ganglion dynamics (2015, methodology): “The capillary number Camacro describing this balance [Armstrong et al., 2014] is here approximated as Camacro ¼ l cl rp φ μwv σ (1) where l cl is the average cluster length, and rp the radius of a pore throat.”
Modeling the velocity field during Haines jumps in porous media (2015, unknown): “Recent advances in the imaging of pore-scale displacements [3,7] and pore-scale simulations [32] can assist in understand pore-scale processes, interactions between processes, and the associated length and time scales.”
Pore-Scale Characterization of Two-Phase Flow Using Integral Geometry (2017, methodology): “The details of the beam line settings including energy, filters, camera, number of projections, angular steps, and optics were the same as that reported in our previous publications (Armstrong et al. 2014b).”
Pore‐by‐pore capillary pressure measurements using X‐ray microtomography at reservoir conditions: Curvature, snap‐off, and remobilization of residual CO2 (2014, methodology): “New formulations of capillary number [Armstrong et al., 2014; Hilfer and Oren, 1996; Melrose and Brandner, 1974] have incorporated the increased impact of viscous shear across an extended nonwettingwetting phase interface by adding a term incorporating cluster length, only available through…”
Pore‐scale displacement mechanisms as a source of hysteresis for two‐phase flow in porous media (2016, background): “For two-phase flow, the critical length of the sample is governed by the maximum size of fluid clusters, which differs with flow rate [Armstrong et al., 2014; Hilfer and Øren, 1996].”