Curvature Measurement and Tracking of Nonwetting Phase Trapping and Pressure State in Porous Media

Abstract:

X-ray microtomography images are used to predict capillary pressure of trapped phase via interfacial curvature measurement and applying the Young-LaPlace equation. We have made several improvements to previous algorithms by removing interface segments that are affected by proximity to the solid surface, and by using distance-weighted curvature estimates. The algorithm shows significant improvement over previous quantification and allows for a close match to externally-measured capillary pressure values obtained using pressure transducers.

The data also allows us to track the pressure state of trapped nonwetting phase and illustrates the dependence of pressure state of trapped objects (nonwetting phase blobs) on pore morphology as opposed to the bulk fluid pressure when the object is trapped. Individual objects can be followed during several drainage and imbibition cycles, and curvature changes followed as the object expands or contracts. This has important implications for how we understand trapping in multi-phase porous medium systems.