Measurement of interfacial area per volume for drainage and imbibition

We investigate experimentally the functional relationship between capillary pressure, Pc, wetting phase saturation, Sw, and interfacial area per volume between the wetting and nonwetting phases, awn, for drainage and imbibition processes in micromodels of two‐dimensional pore structures. Within the experimental and analysis error (around 10–15%), the resulting Pc‐Sw‐awn surfaces were the same. This suggests that data obtained from either the drainage process or the imbibition process are sufficient to generate the complete functional relationship among Pc‐Sw‐awn and that the observed hysteresis in Pc‐Sw‐awn can be modeled by including interfacial area as an additional state variable.