Abstract: The foam stability stabilized by α-olefin sulfonate(AOS) with different hydrophobic chain lengths at temperature below 100 ℃ and above 200 ℃ was investigated by foam column decay method and foam block in sand-pack pipe, respectively. The results show that the foam stability increases with the increase of hydrophobic chain length. Dynamic surface tension, interfacial rheometer and molecular simulation were used to study the foam stablity mechanism at a high temperature. From the experiment results, we can see that when the hydrophobic chain length was longer than 20 carbon atoms, the hydration of surfacrtant head could not support the hydrophobic chain to keep vertical or unattached, and the hydrophobic chains cross-link with each other, which increase the strength of the foam film, decrease the diffusion of the gas through the film and make the foam stable at a high temperature.

Key words: Foam stability, High temperature foam, Foam block, Steam flooding, Hydrophobic chain length