CO2 FOAMS IN ENHANCED OIL-RECOVERY

This chapter reviews the special qualities of CO2 floods that make foam particularly attractive as a mobility-control agent. These features also impose requirements on the surfactant that forms the foam. Examples are given of high-pressure techniques of measurement that can determine the mobility of CO2 foam under different surfactant concentration and type, flow velocities, and concentrations of the dense CO2. A promising result is that some surfactants produce CO2 foams for which the mobility is less than proportional to the rock permeability, and this result implies that CO2 foams might be used to ''smooth out'' the uneven flow otherwise resulting from permeability heterogeneities in the reservoir. Other topics include surfactant adsorption and the durability of high-pressure CO2 foams. A final topic concerns field operational procedures in application of this promising mobility-control method.