Steam-foam has been used extensively in field trials to improve steam conformance, both for cyclic steam injection and steam flood. It is a proven process and very useful lessons can be drawn from these field trials to plan new projects. However, foam has not yet been used to improve SAGD (Steam-Assisted Gravity Drainage) performances. The aim of this paper is to examine the reasons for this situation and discuss the practical aspects of Foam-Assisted SAGD (FA-SAGD).
After a thorough description of the main mechanisms involved in these processes (steam-foam for cyclic steam injection and steam flood, as well as foam for SAGD), this paper proposes to review the differences between the various processes and their implications for the design and implementation of FA-SAGD. Finally, based on the lessons drawn from all the documented steam-foam trials, potential and drawbacks of FA-SAGD are presented together with suggested roadmaps to address these remaining and newly identified challenges to make this technology come true.
By definition, the driving mechanism of SAGD relies on gravity and involves the use of a pair of horizontal wells drilled a few meters apart, one on top of the other. This is completely different from foam applications with both cyclic steam injection and steam flood, which are typically conducted with vertical wells; in addition, cyclic steam relies on single wells only whereas steam flood is essentially a lateral displacement process. Steam quality, injection velocity, proximity of the injection and production wells and the risks associated with the formation of emulsions in the surface facilities are some of the issues that are typically not problematic for foam with conventional steam processes, but which need to be considered before FA-SAGD can be implemented in the field. This work concludes that FA-SAGD is feasible but that ignoring any of these aspects would very likely cause the process to fail in the field.
This study will provide useful physical considerations on the steam-foam process along with detailed guidelines for the implementation of the Foam-Assisted SAGD process in the field. It will be useful for engineers that are considering foam to improve the performances of SAGD by targeting a reduction of the steam consumption or the Steam Oil Ratio.