Influence of Different Reservoir Conditions on the Stability and Decay Mechanism of the Polymer-Enhanced Foam

Foam is commonly used in tertiary oil recovery because it plugs specific areas. Foam is thermodynamically unstable owing to reservoir complexity. Foam stability in the reservoir is the key research focus. This study examined the foaming volume and half-life of a sodium α-olefin sulfonate (AOS)-diutan gum (DYG) foam under different temperatures, salinities, and oil saturation conditions. Dynamic behavior of the foam drainage process was studied. The foam drainage rate constant (Kd) was determined using a kinetic model under varied situations. The foam drainage activation energy was calculated by correlating Kd values at different temperatures by using the Arrhenius equation. Under different settings, the average bubble diameter, polydispersity coefficient, and Ostwald ripening rate during foam degradation were calculated statistically. Finally, AOS-DYG foam migration stability in porous media was investigated using a microscopic displacement model. The experimental results show that high temperatures decrease foam stability and hasten drainage. AOS-DYG foam showed good temperature resistance, with a foam complex index (FCI, it is obtained by multiplying the foaming volume of foam and the half-life of liquid drainage) of 72.21% at 100 °C compared to 60 °C. By compressing the double electron layer, inorganic salt reduced the foam liquid film thickness. Compression increases liquid film drainage, decreasing AOS-DYG foam stability. AOS-DYG foam with 5 times higher salinity has 76% of normal salinity FCI. This indicates significant salt resistance. A small amount of crude oil can stabilize foam. When oil saturation reached 5%, foam drainage encountered the maximum energy barrier, ensuring foam stability. AOS-DYG foam's long-distance migration stability was proven by microscopic displacement experiments. The findings help explain polymer-improved foam resilience and degradation under different environmental conditions.