Although gel treatments have gained acceptance for injection well profile modification, high treatment cost and potential loss of low permeability zone injectivity curbs implementation. This study investigates an in-situ generated foamed gel barrier that is well suited for long-term waterflood diversion because it provides an intermediate degree of plugging, yet requires substantially less polymer than bulk gels. Microvisual observations indicate foamed gel barriers are initially impermeable but break down when the pressure exceeds a critical value. This critical pressure that initiates breakdown varies with foam quality, permeability, and gel properties.
Foamed gels are currently used for a wide variety of applications including fracturing, stabilization of earthen formations, and plugging of high-permeability streaks. In each of these applications, a permeability loss occurs, whether designed or not, due to invasion of the foamed gel into the pore space. Although the foamed gels have proven effective in these applications, the mechanism of permeability reduction has not been verified and no published work studies the factors that influence the performance of foamed gel barriers.
The application of a foamed polymer gel to modify the injection profile of macroscopically heterogeneous porous media was investigated. Ideally, it is hoped that drive fluid channeling could be eliminated and/or sweep efficiency improved without losing injectivity of unswept zones. Unfortunately, it is not possible to prevent significant loss of injectivity using the currently available chemicals and treatment strategies.
Although foamed gel cannot prevent loss of low-permeability zone injectivity, it does reduce chemical requirements, offers greater control over the permeability reduction, and inhibits migration of the gelant prior to gelation. Thus, foamed gel possesses some properties that make it well suited for profile modification treatments.