Relating Capillary Pressure to Interfacial Areas Using a Two-dimensional Micromodel

Capillary pressure plays a critical role in multiphase flow and transport in porous media. Because it is defined as the difference in wetting and non-wetting fluid pressures, it is also a function of both saturation and the interfacial area between the wetting and non-wetting phases. Experiments were performed in a two- dimensional micro-scale porous medium to gain insight into the relationship between externally measured capillary pressure and internally measured interfacial curvature, as well as the potential dependence of interface relaxation rates on flow velocities, High resolution images of phase distributions and associated interfaces within the pores are collected during drainage and imbibitions experiments. Images with app. 1 um resolution are acquired at regular intervals during the relaxation process. Concurrently, pressure in each phase is measured with a transducer outside the porous medium, and Laplace's Law is used to calculate the average pressure inside the porous medium based on measured curvatures, such that the two pressure values can be compared. The relaxation of capillary pressure can then be correlated to the relaxation of interface menisci for varying degrees of system saturation, and for varying flow rates. The images and capillary pressure measurements will allow for investigation of pore scale properties during dynamic flow conditions, as well as static conditions, and importantly, allow for comparison among the two situations.