Journal
JOURNAL OF COLLOID AND INTERFACE SCIENCE
Volume 609, Issue -, Pages 384-392Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcis.2021.11.109
Keywords
Imbibition; snap-off; pore-filling; multiphase flow; porous media; 4D X-ray imaging
Categories
Funding
- Qatar Carbonates and Carbon Storage Research Centre (QCCSRC)
- Qatar Petroleum
- Shell
- Qatar Science and Technology Park
- Total and Wintershall DEA
- Natural Environment Research Council [NE/N016173/1]
- [12X0919N]
- NERC [NE/N016173/1] Funding Source: UKRI
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This study investigates the pore-scale processes in natural porous media using time-resolved 3D X-ray imaging. A new type of snap-off in pores is discovered, trapping a small portion of the non-wetting phase in pore corners. The findings provide correlations for displacement events based on pore-throat geometry.
Hypothesis: Imbibition of a fluid into a porous material involves the invasion of a wetting fluid in the pore space through piston-like displacement, film and corner flow, snap-off and pore bypassing. These processes have been studied extensively in two-dimensional (2D) porous systems; however, their relevance to threedimensional (3D) natural porous media is poorly understood. Here, we investigate these pore-scale processes in a natural rock sample using time-resolved 3D (i.e., four-dimensional or 4D) X-ray imaging. Experiments: We performed a capillary-controlled drainage-imbibition experiment on an initially brinesaturated carbonate rock sample. The sample was imaged continuously during imbibition using 4D Xray imaging to visualize and analyze fluid displacement and snap-off processes at the pore-scale. Findings: We discover a new type of snap-off that occurs in pores, resulting in the entrapment of a small portion of the non-wetting phase in pore corners. This contrasts with previously-observed snap-off in throats which traps the non-wetting phase in pore centers. We relate the new type of pore-snap-off to the pinning of fluid-fluid interfaces at rough surfaces, creating contact angles close to 90 degrees. Subsequently, we provide correlations for displacement events as a function of pore-throat geometry. Our findings indicate that having a small throat does not necessarily favor snap-off: the key criterion is the throat radius in relation to the pore radius involved in a displacement event, captured by the aspect ratio. (C) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
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