Insights on foam generation in porous media from pore-network studies

We report an extensive pore-network study that incorporates pore-level mechanisms, as foam is created by drainage or the continuous injection of gas and liquid in porous media. Pore networks with up to 10,000 pores are considered, with rules for the formation and movement of foam lamellae by the mechanisms of snap-off, leave-behind and lamella division enforced throughout. The study explores the roles of these mechanisms, and by implication, the appropriate form of the foam-generation function for mechanistic foam simulation. Results are compared with previous studies. In particular, they reconcile an apparent contradiction in the foam-generation model of Rossen and Gauglitz [W.R. Rossen, P.A. Gauglitz, Percolation theory of creation and mobilization of foam in porous media, AIChE J. 36 (1990) 1176], and identify how foam is created near the inlet of the porous medium when lamella division controls foam generation. In the process, we identify a new mechanism of snap-off and foam generation near the inlet of the medium.