EVALUATION OF DRAINAGE PROCESS IN POROUS MEDIA BY INVADED PERCOLATION PROBABILITY

Abstract

Invasion processes, such as the imbibition and drainage processes, through porous media could be modeled using the invasion percolation model in a pore-network that is extracted from actual or virtual packed grains. It is well known that water retention properties depend on pore structures such as pore shape, pore-size distribution, and pore-connectivity. However, in our previous work, it is confirmed that there is a spatial structure even in a porous medium packed with single-size grains, and that if the spatial structure of the pores is not disturbed, different water retention curves obtained from different pore-size distributions for the imbibition process can be unified into a single curve using the invaded percolation probability (IPP). This is the proposed evaluation method based on the percolation probability (PP). In this study, the drainage process is evaluated using water retention curves and the IPP through numerical experiments. The results show that the different water retention curves were unified into a certain curve based on the PP when the IPP based on pore body and pore throat was employed. Using this evaluation method, we can obtain additional information regarding the proportion of potentially invadable and actually invaded pores and the degree of their spread in the porous media. Hence, it is concluded that this method could be a very useful tool to grasp the state of porous media.