Micro-model experiments and pore network simulations of liquid imbibition in porous media

• Wetting experiments with an etched micro model for mixtures of ethanol and water.
• Imbibition kinetics of water mixtures can be described by the Lucas–Washburn.
• Development of a pore network model for spontaneous capillary imbibition.
• Comparison of optical experimental results with pore network simulations.
• Influence of pore structure on the imbibition dynamics by network simulations.

In this study, spontaneous capillary imbibition into an air-filled transparent etched silicon-glass micro-model is investigated by optical imaging under ambient conditions for mixtures of ethanol and water. Images of the micro-model are acquired by a high-speed CCD camera. The binarized images allow us to obtain the overall imbibition kinetics and the time evolution of the phase distribution. A pore network with the structure parameters of the physical micro-model is generated, and a wetting algorithm that combines several pore-level liquid transport rules is developed to simulate the spontaneous imbibition of the liquid mixture into the network. The pore network simulations are able to reproduce the effects observed in the micro-model experiments. The influence of spatially correlated structural features on the imbibition dynamics is studied by further pore network simulations, and pore structures that cause weak or strong capillary imbibition are identified. The results of wetting simulations are shown for situations which cannot be treated by the Lucas–Washburn equation.