Abstract
Hypothesis
Capillary-dominated multiphase flow in porous materials is strongly affected by the pore walls’ wettability. Recent micro-computed tomography (mCT) studies found unexpectedly wide contact angle distributions measured on static fluid distributions inside the pores. We hypothesize that analysis on time-resolved mCT data of fluid invasion events may be more directly relevant to the fluid dynamics.
Experiment
We approximated receding contact angles locally in time and space on time-resolved mCT datasets of drainage in a glass bead pack and a limestone. Whenever a meniscus suddenly entered one or more pores, geometric and thermodynamically consistent contact angles in the surrounding pores were measured in the time step just prior to the displacement event. We introduced a new force-based contact angle, defined to recover the measured capillary pressure in the invaded pore throat prior to interface movement.
Findings
Unlike the classical method, the new geometric and force-based contact angles followed plausible, narrower distributions and were mutually consistent. We were unable to obtain credible results with the thermodynamically consistent method, likely because of sensitivity to common imaging artifacts and neglecting dissipation. Time-resolved mCT analysis can yield a more appropriate wettability characterization for pore scale models, despite the need to further reduce image analysis uncertainties.
Capillary-dominated multiphase flow in porous materials is strongly affected by the pore walls’ wettability. Recent micro-computed tomography (mCT) studies found unexpectedly wide contact angle distributions measured on static fluid distributions inside the pores. We hypothesize that analysis on time-resolved mCT data of fluid invasion events may be more directly relevant to the fluid dynamics.
Experiment
We approximated receding contact angles locally in time and space on time-resolved mCT datasets of drainage in a glass bead pack and a limestone. Whenever a meniscus suddenly entered one or more pores, geometric and thermodynamically consistent contact angles in the surrounding pores were measured in the time step just prior to the displacement event. We introduced a new force-based contact angle, defined to recover the measured capillary pressure in the invaded pore throat prior to interface movement.
Findings
Unlike the classical method, the new geometric and force-based contact angles followed plausible, narrower distributions and were mutually consistent. We were unable to obtain credible results with the thermodynamically consistent method, likely because of sensitivity to common imaging artifacts and neglecting dissipation. Time-resolved mCT analysis can yield a more appropriate wettability characterization for pore scale models, despite the need to further reduce image analysis uncertainties.
| Original language | English |
|---|---|
| Pages (from-to) | 354-363 |
| Number of pages | 10 |
| Journal | Journal of Colloid and Interface Science |
| Volume | 572 |
| DOIs | |
| Publication status | Published - 15 Jul 2020 |
Funding
Dr. Steffen Schlüter and Dr. Kamaljit Singh are thanked for making their data available and their helpful discussions. The two anonymous reviewers are thanked for their constructive feedback. This research received funding from the Research Foundation–Flanders (FWO, project G051418N ). Tom Bultreys is a postdoctoral fellow of the Research Foundation–Flanders (FWO) and acknowledges its support under grant 12X0919N. The data used in this manuscript is freely available online, as cited in the main text.
Keywords
- Contact angle
- Haines jump
- Imaging
- Interfacial curvature
- Multiphase flow
- Pore-scale
- Porous media
- Primary drainage
- Wettability
- X-ray micro-tomography