A laboratory study of enhancing heavy oil recovery with steam flooding by adding nitrogen foams

•A new evaluation method of foaming agent for thermal recovery was established.•3D physical simulation was carried out to research the effect of thermal foams.•The distribution of remaining oil was presented to analyze EOR mechanisms.•The mechanisms of thermal foams include profile control and water cut reduction.

Two significant problems, steam override and steam channeling, decrease the sweep efficiency of steam to result in a lower oil recovery in heavy oil reservoirs. Thermal foam flooding, which is in fact steam flooding by adding non-condensate gas and foaming agent, presents a satisfactory effect in laboratory and field pilot. In this article, a new evaluation method was introduced to choose the optimum foaming agent for thermal foam flooding. The method considered the influence of temperature variation on the properties of foaming agent during steam flooding. Then the chosen surfactant and nitrogen were injected into the reservoir model in our experiments. The results showed that nitrogen foams effectively increased displacement efficiency of steam flooding from 43.30% to 81.24% in the single sand-pack experiment. Thermal foams can effectively improve injection profile to restrain steam injection from gravity override and steam channeling in reservoirs. Foaming agent is an important component in thermal foam flooding; on the one hand, it decreases oil–water interface tension to improve oil displacement efficiency, and on the other hand, it increases the stability of foams to improve sweep efficiency. Therefore, steam flooding by adding nitrogen foams is an effective EOR method to develop heavy oil reservoirs.

Graphical abstractSteam override and steam channeling largely decrease the sweep efficiency of steam to result in a lower oil recovery in heavy oil reservoirs. Thermal foams can effectively improve injection profile to restrain steam injection from gravity override and steam channeling in reservoirs. Foaming agent is an important component in thermal foam flooding; on the one hand, it decreases oil–water interface tension to improve oil displacement efficiency, but on the other hand, it increases the stability of foams to improve sweep efficiency. Therefore, steam flooding by adding nitrogen foams is an effective EOR method to develop heavy oil reservoirs.Figure optionsDownload full-size imageDownload as PowerPoint slide