Energy efficiency and greenhouse gas emissions of current steam injection process and promising steam based techniques for heavy oil reservoirs

Steam injection process has been the prevailing technique for heavy oil and bitumen extraction in the past decades, but the recovery performance and energy efficiency are poor, especially in oil reservoirs with harsh conditions and severe heterogeneity. With global requirements on energy conservation and emission reduction, it is of great significance to improve current techniques or find new techniques to promote the energy efficiency of steam injection process and mitigate associated greenhouse gas emissions. In this study, the energy efficiency and CO2 emissions of current steam injection processes were evaluated, along with sensitivity analysis of various influencing factors. Cyclic steam stimulation (CSS) process was taken as an example to study the production and energy efficiency performance of steam injection. The results show that the steam to oil ratio, energy intensity and CO2 emissions all rise with the increasing crude oil viscosity, but fall with the increase of oil saturation, reservoir temperature, bottom hole steam quality and reservoir heat efficiency. Field history analysis about CSS process shows that the production performance of CSS process was dominated by different factors with the proceeding of oil production, and gas injection assisted CSS process can effectively enhance oil recovery, improve energy efficiency and mitigate CO2 emissions. Finally, the improved steam injection techniques are discussed to shed some lights on the efficient exploitation of heavy oil reservoirs.