Alexey Andrianov

Foam–oil interaction in porous media: Implications for foam assisted enhanced oil recovery

The efficiency of a foam displacement process in enhanced oil recovery (EOR) depends largely on the stability of foam films in the presence of oil. Experimental studies have demonstrated the detrimental impact of oil on foam stability. This paper reviews the mechanisms and theories (disjoining pressure, coalescence and drainage, entering and spreading of oil, oil emulsification, pinch-off, etc.) suggested in the literature to explain the impact of oil on foam stability in the bulk and porous media. Moreover, we describe the existing approaches to foam modeling in porous media and the ways these models describe the oil effect on foam propagation in porous media. Further, we present various ideas on an improvement of foam stability and longevity in the presence of oil. The outstanding questions regarding foam-oil interactions and modeling of these interactions are pointed out.

Novel Insight into Foam Mobility Control

laboratory study of foam propagation in natural sandstones in the absence of oil is reported. The goal of this study was to elucidate further the mechanisms of foam mobility control. The C14-16 Alpha-Olefin Sulfonate (AOS) surfactant was selected to stabilize nitrogen foam. X-ray CT scan images were taken during foam propagation to map liquid saturation over time. The effects of surfactant concentration and of total injection velocity were examined in detail as these are key parameters for controlling foam strength and foam propagation under field conditions.

New Insights into Application of Foam for Acid Diversion

Foam is widely used to divert acid or abandon the high permeable layers. In this type of application foam should considerably reduce gas mobility. The nature of the gas and the surfactant may influence foaming behavior and thus the efficiency of the foam. In this paper an experimental study of the behaviorof CO2 and N2 foams in granular porous media using X-ray Computed Tomography is reported. In the experiments gas is forced through natural porous media initially saturated with a surfactant solution, a process known as SurfactantAlternatingGas (SAG). The CO2 was either under subor super-critical conditions whereas N2 remained under subcritical conditions in all experiments. Alpha Olefin Sulfonate (AOS) surfactant was used as foaming agent. We found that injection of gas following a slug of surfactant can considerably reduce gas mobility and promote higher liquid recovery at the experimental conditions investigated. Foaming of CO2 builds-up a lower pressure drop over the core at both low and high pressures than N2. Both gases require a certain penetration depth to develop into foam. This length is longer for N2 (larger entrance effect) and increases with growing gas velocity. Moreover, the ultimate liquid recovery by CO2 foam is always lower than by N2 foam. The possible mechanisms explaining the observed differences in foaming behavior of the two gases are discussed in detail.