(76b) Foam for Mobility Control in Enhanced Oil Recovery Processes Using Surfactants

Water-soluble polymers of high molecular weight such as partially hydrolyzed polyacrylamides are the usual method of providing mobility control and thus improving sweep efficiency in surfactant and alkaline/surfactant processes for enhanced oil recovery. Foam offers the prospect of further improvement in sweep efficiency, especially in heterogeneous reservoirs, because foam mobility is lower (apparent viscosity is higher) in layers of high permeability than in those of low permeability. While additional surfactant is needed to generate the foam, its amount and cost is less than the decrease in the amount and cost of polymer because half or more of the injected fluid is gas in the foam case. Results of alkaline/surfactant floods carried out in one-foot long sand packs with polymer drive and with foam are presented to support these statements. Recovery of residual oil is excellent in both cases for the surfactant mixture used. Apparent viscosity of the foam is approximately a factor of five larger in the sand pack with the higher permeability, confirming the ability of foam to provide a more uniform sweep than polymer.