What is the term for the pressure difference between the non-wetting and wetting phases in a capillary interface?

What is the term for the pressure difference between the non-wetting and wetting phases in a capillary interface?

• A. Capillary pressure
• B. Pore pressure
• C. Hydrostatic pressure
• D. Piezometric pressure

Answer: (A)

Capillary pressure is the pressure difference across the interface between the non-wetting and wetting fluids in a capillary or pore throat. This jump arises because the interface is curved due to interfacial tension and the geometry of the pore, and it is described by the Young-Laplace relation. In porous media, capillary pressure is defined as the pressure in the non-wetting phase minus the pressure in the wetting phase (Pc = P_nw − P_w). A positive capillary pressure means the non-wetting phase sits at a higher pressure than the wetting phase, which influences which fluid fills a pore throat and how fluids distribution changes during drainage or imbibition. Pore pressure is simply the fluid pressure inside the pore space, not the interfacial difference. Hydrostatic pressure is due to the weight of the fluid and varies with depth. Piezometric pressure relates to hydraulic head rather than the capillary interface jump.

Capillary pressure is the pressure difference across the interface between the non-wetting and wetting fluids in a capillary or pore throat. This jump arises because the interface is curved due to interfacial tension and the geometry of the pore, and it is described by the Young-Laplace relation. In porous media, capillary pressure is defined as the pressure in the non-wetting phase minus the pressure in the wetting phase (Pc = P_nw − P_w). A positive capillary pressure means the non-wetting phase sits at a higher pressure than the wetting phase, which influences which fluid fills a pore throat and how fluids distribution changes during drainage or imbibition.

Pore pressure is simply the fluid pressure inside the pore space, not the interfacial difference. Hydrostatic pressure is due to the weight of the fluid and varies with depth. Piezometric pressure relates to hydraulic head rather than the capillary interface jump.