Prediction of fluid distribution in porous media treated with foamed gel

Abstract

A wide variety of materials used to plug porous media, such as cross-linked polymer gels, bacterial biomass, and foamed polymer gels, breakdown when exposed to excessive stress. However, models typically used to evaluate the effect of these plugging agents neglect the breakdown phenomena and may not accurately assess the effect of a given treatment. Foamed gel is a very efficient, low-cost plugging agent that is particularly susceptible to stress-induced breakdown. This paper demonstrates the effect of breakdown on the performance of foamed gel profile modification using a foamed gel breakdown network model. It is shown that a simple analysis can be made using Darcy's law and a relationship between the applied pressure and the foamed gel barrier's permeability when the porous medium is comprised of noncommunicating layers of different permeability. Two types of successful treatments are identified, and they are distinguished by whether the foamed gel barrier in the low permeability zone breaks down at lower pressures (type 1) or higher pressures (type2) than the high permeability zone barrier. The relative length of the barriers in high and low permeability zones as well as factors that influence the gelled lens aspect ratio (permeability and gel saturation) govern whether a treatment is type 1 (low permeability zone breaks down at lower pressures) or not. Under low injection pressures, all radial profile modification treatments have a higher post-treatment flow redistribution ratio than linear treatments; under high injection pressures, only type 2 radial treatments have a higher flow redistribution.