Flow characteristics and regime transition of aqueous foams in porous media over a wide range of quality, velocity, and surfactant concentration

Aqueous foam is broadly applicable to enhanced oil recovery (EOR). The rheology of foam as a function of foam quality, gas and liquid velocities, and surfactant concentration constitute the foundation of its application. The great variations of the above factors can affect the effectiveness of N₂ foam in EOR continuously in complex formations, which is rarely involved in previous relevant studies. This paper presents an experimental study of foam flow in porous media by injecting pre-generated N₂ foam into a sand pack under the conditions of considering a wide range of gas and liquid velocities and surfactant concentrations. The results show that in a wide range of gas and liquid velocities, the pressure gradient contours are L-shaped near the coordinate axes, but V-shaped in other regions. And the surfactant concentration is a strong factor influencing the trend of pressure gradient contours. Foam flow resistance is very sensitive to the surfactant concentration in both the high- and low-foam quality regime, especially when the surfactant concentration is less than CMC. The foam quality is an important variable to the flow resistance obtained. There exists a transition point from low- to high-quality regime in a particular flow system, where has the maximum flow resistance, the corresponding foam quality is called transition foam quality, which increases as the surfactant concentration increases. The results can add to our knowledge base of foam rheology in porous media, and can provide a strong basis for the field application of foams.