Percolation modeling of foam generation in Porous media

Abstract

A foam is a dispersion of a large volume of gas in a continuous liquid phase, stabilized by surfactant. Foams can improve sweep efficiency and oil recovery in gas-injection enhanced oil recovery projects. An important issue for these foam processes is the ease of foam generation in porous media. Previously, Rossen and Gauglitz (1990) derived a percolation model for foam generation in steady gas-liquid flow in porous media. More recent advances in percolation theory require modification of this model, as described in this note. Briefly, Rossen and Gauglitz assumed that the liquid films or lamellae present in foam block a randomly selected fraction (1 [minus] f) of the pore throats in the medium. Creating the large number of lamellae that define a foam from the relatively few present initially requires displacing these lamellae from their pore throats so they can multiply by the processes of lamella division and repeated snapoff. Displacing lamellae from pore throats to initiate the generation process requires imposing a pressure difference across the throat of order one or a few kPa (a few tenths of a psi). Generating'' foam, therefore, depends on lamella mobilization, which depends on the magnitude of the pressure drop [Delta]P across individualmore » pore throats blocked by lamellae. Rossen and Gauglitz's model predicts that the minimum pressure gradient for foam generation [del]P[sup min] decreases nearly linearly, as f approaches f[sub c], the percolation threshold for the pore network, from either direction.« less