Foam-Oil Interaction in Porous Media - Implications for Foam-assisted Enhanced Oil Recovery (SPE 154197)

A problem associated with many gas injection projects is the inefficient gas utilization, poor sweep efficiency, oil recovery due to viscous instabilities (channelling or fingering), and gravity segregation. The above mentioned effects are caused by rock heterogeneity and the low density and viscosity of the injected gas. Foam, which is created by co-injection of surfactant solution and gas, or by SAG (Surfactant-Alternating-Gas), can be injected into oil reservoir to mitigate these drawbacks. When foam films are created in-situ, the flow of gas is hindered and gas can sweep portions of the reservoir that would not been reached in the absence of foam. Potentially foam injection can lead to better pore, aerial, and vertical sweep efficiencies. The efficiency of the displacement process in a foam assisted gas flood depends largely on the longevity of the created foam films, ratio of films destabilization and re-generation rates. Experimental results have demonstrated that oil can have a detrimental impact on foam stability. This paper summarizes experimental and theoretical results on the effect of oil on foam stability both in bulk and porous media. The relevant mechanisms of foam (in)stability in the presence of oil and destruction by oil such as disjoining pressure, coalescence and drainage, entering and spreading of oil, oil emulsification, snap-off, etc. are critically reviewed. Moreover, we describe the existing approaches to foam modeling in porous media and the ways these models represent the effect of oil on foam propagation in porous media. Finally, ways to improve foam stability in the presence of oil are discussed.