Spatially distributed wettability characterization in porous media.

Area of Science:

• Geosciences
• Physics
• Chemistry

Background:

• Multiphase flow in porous media is controlled by local wetting properties.
• Spatial variability of wettability in situ is difficult to quantify using micro-CT imaging.
• Estimating contact angles is challenging due to partial-volume effects and segmentation uncertainties, hindering reliable pore-scale wettability heterogeneity resolution.

Purpose of the Study:

• To introduce a novel automated geometric algorithm for pore-by-pore contact angle measurement.
• To overcome limitations of existing methods in resolving pore-scale wettability heterogeneity.
• To enable accurate wettability characterization for various subsurface applications.

Main Methods:

• Developed an automated geometric algorithm to measure pore-by-pore contact angles.
• Bypassed explicit contact loop detection by extrapolating surface normals from neighboring two-phase interfaces.
• Validated the method on synthetic datasets and applied it to water-wet and mixed-wet rock samples.

Main Results:

• The algorithm reduces sensitivity to segmentation errors and partial-volume effects.
• Quantified measurement uncertainty, noting amplification in smaller pores.
• Revealed significant wettability heterogeneity masked by bulk averages, with 40% of pore space in intermediate-wetting regimes in a mixed-wet sample.
• Demonstrated that wettability heterogeneity broadens the contact angle distribution.

Conclusions:

• The novel algorithm provides accurate, spatially resolved wettability characterization.
• Wettability heterogeneity significantly impacts multiphase flow behavior.
• Open-source software is available for applications in CO2 sequestration, hydrogen storage, and multiphase flow.