Foam as a Mobility Control Agent in Steam Injection Processes

Abstract

ABSTRACT Although our primary interest in studying the technique of mobility control by foaming agents was for steam injection processes, this method seems to offer excellent prospects of improving oil recovery efficiency in any type of gas drive process. Laboratory studies showed that gravity override of injected gases in gas drive processes can be strikingly reduced and hence recovery increased by in-situ generation of foam. A two-dimensional, vertical plexiglas model holding a 4' × 1' × 0.25″ sandpack was used to investigate this phenomenon. Saturation of the sandpack by a surfactant solution instead of pure water sharply increased liquid recovery and breakthrough time in nitrogen flooding process. The improvement in production was shown to be due to a reduction of gravity override caused by in-situ generation of foam at the gas-liquid interface. A large range of surfactant solutions of various concentrations with different amounts of monovalent and bivalent salts and alcohols has been studied as to their effectiveness as foamers. Surface tension, rate of drainage, bubble size and shape of the foams were measured in each case. In-situ foaming in the model increased generally with surfactant concentration until the critical micelle concentration (CMC) was reached; above CMC additional amounts of surfactant had very little effect on the phenomenon. Similar increase of recovery and delay in breakthrough time was observed in oil flooding processes. A slug of surfactant solution was injected into the pack saturated with oil, and water at irreducible water saturation, and then nitrogen was injected. Gravity override was much less than in the case when no surfactant was present.