Hybrid processes combine the benefits of both thermal and solvent processes. The results generated to date in this area demonstrate potential to develop improved processes that will significantly reduce energy, water and greenhouse gas (GHG) intensity, and therefore operating costs, while maintaining economic oil recovery rates. The Steam Butane Hybrid (SBH) process has emerged as a promising hybrid process that could be considered as an alternative to SAGD, where the performance of SAGD is expected to be less than ideal.
This paper summarizes the results of a study designed to evaluate the performance of the SBH process in comparison with the SAGD process for three different reservoir models (Geomodel I, II and III) using numerical simulation. Geomodel III is the cleanest (highest average permeability) and most homogeneous of the three reservoir models. Geomodel II has the lowest average permeability, and the highest shale content, while Geomodel I is midway between the other two, in terms of average permeability and shale content. Five well pairs were used in all of the simulations. Three different injection pressures were investigated: 2000, 1000 & 800 kPa*.
It was found that geology plays a very important role in determining the competitive advantage of SBH vs. SAGD. It also plays an important role in establishing optimal operating conditions for the process in the field. The predicted performance of SBH, in terms of cumulative oil production, was better than that of SAGD at low injection pressures in the two geomodels (I & II) with lower average permeabilities. In the geomodel with the highest average permeability (III), the predicted performance of the SBH process was slightly poorer than that of SAGD at a relatively low injection pressure (800 kPa), but slightly better than that of SAGD at a relatively high injection pressure (2000 kPa).
These numerical simulation results indicate that the relative performance of SBH as compared with SAGD is likely to be reservoir specific, meaning that the optimal injection pressures and butane concentrations should be tailored to specific reservoir characteristics, on a case by case basis, rather than generalizing the process to a range of reservoir conditions.