Immiscible Foam for Enhancing Oil Recovery: Bulk and Porous Media Experiments

This paper reports a laboratory study of foams intended to improve immiscible gas flooding in oil production. The study is relevant for both continuous and water alternating gas (WAG) injection schemes. The effect of oil on the longevity of nitrogen and air foams was studied in bulk for a selected set of surfactants. Foam heights were measured in a glass column as a function of time, in the absence and presence of mineral and crude oils. The column experiments indicated that foam longevity increases as the carbon chain length in the oil molecule increases; that is, foam is generally more stable in the presence of higher-viscosity oils. The surfactant formulation that gave the most stable foam in the presence of oil was used in core floods. Oil recovery from natural sandstone cores with CO2 and with N-2 foams was studied with the aid of X-ray computed tomography, while the injection rates, foam quality, and surfactant concentration were varied. The core floods revealed that foam increases oil recovery by as much as 20% of the oil initially in place (OIIP) as compared with water flooding, while gas injection increases oil recovery by 10% only. Thus, foam can achieve an additional recovery of up to 10% relative to gas injection. This confirms that foam is potentially an efficient enhanced oil recovery (EOR) method.