Abstract
Steam override and channeling due to high steam mobility during steam injection for heavy oil recovery can result in high operating costs and low oil recovery. The high steam mobility issue can be overcome with a sufficient increase in the apparent steam viscosity by surfactant stabilized foams. The objective of this research is to identify surfactants that are thermally stable and can generate stable foam at typical conditions of steam injection for thermal steam EOR processes. Proprietary surfactant structures were found to be stable at up to 250 °C for at least 2 weeks. It was also found that these surfactants at 0.5 wt% concentration were able to generate stable foam in the sandpack with steam at 75% quality (i.e. volume fraction of steam in the injected mixture of steam and surfactant solution) and up to 250 °C. Foam increased the apparent steam viscosity by three orders of magnitude without bitumen and by two orders of magnitude in the presence of bitumen. The results demonstrate that this type of surfactant significantly reduces steam mobility, which is needed to overcome steam gravity override and channeling issues. The study of structure-property relationship shows that the foaming efficiency and effectiveness depend on the temperature and the hydrophobicity of the surfactants. Past research reported in literature focused mostly on sulfonate surfactants as foaming agents for steam EOR processes at operating temperatures up to 200 °C and in the absence of oil. This work has extended the scope of steam foam research as it identified surfactants that are thermally stable and could stabilize foam at up to 250 °C even in the presence of oil. In addition, the structures of the identified surfactants in this study could be optimized with respect to surfactant hydrophobicity to tailor the transport and thermodynamic properties as well as the foam property of the surfactants to target specific reservoir temperature and salinity condition.
