Modeling Foam Generation in Porous Media
This presentation focuses on models for foam generation in porous media. Several studies suggest that at some conditions a minimum superficial velocity or pressure gradient is required to create a "strong" (low-mobility) foam in porous media. A model based on percolation theory explains this minimum requirement in terms of the pressure gradient required to mobilize liquid films or lenses in pore throats and start them reproducing by the process of "lamella division." This simple model fits trends for the minimum velocity or pressure gradient required for foam generation as a function of gas volume fraction of injected fluids (i.e. 'foam quality')
The standard framework for representing dynamic foam behavior in porous media is the "population balance" model. A variant of this model incorporating a relation between pressure gradient and creation of the liquid films separating bubbles in foam can explain the multiple steady states seen with foam in laboratory experiments. When applied to a foam created at high velocity near an injection well displacing reservoir fluids at lower velocity further from the well, the model predicts that the rate of advance of foam may approach zero at some radius from the well. The reason, according to the model, is that foam generation cannot keep up with foam destruction at the front. This provides the first explanation for laboratory results presented by Friedmann et al. going back to the 1980s.