Analysis of the intermittency of the steam alternating solvent process (SAS) applied to a heavy oil reservoir

Abstract In the World energy outlook, the importance of heavy oils has increased every day. It happens because the oil consumption is growing, hence, light oil reserves, which can be easily produced, have been decreasing. Offshore exploration and production activities in Campos, Santos and Espirito Santo basins, in the Brazilian coast, have taken to the discovery of significant amounts of heavy oils, which can complement the Brazilian production. For these kind of oils, it can be applied the steam alternating solvent process (SAS), which combines advantages of SAGD and VAPEX, minimizing the consumption of energy per unit of recovered oil. Therefore, this research aimed at studying the SAS process, through numerical simulations, to evaluate the influence of operational parameters in the oil recovery factor. To reach this goal, it was modeled a homogeneous reservoir, with characteristics similar to those ones found in the Brazilian Northeast, simulated through the STARS (Steam, Thermal and Advanced Process Reservoir Simulation) software, developed by the CMG (Computer Modeling Group Ltd.), considering a project time of 16 years. When compared to the primary recovery and the continuous steam injection, it was verified that, by applying the SAS process, it was obtained the highest oil recovery and there was an anticipation of the arrival of the heated oil bank to the producer well. For the injection interval of 8 years, it was obtained an oil recovery factor of 84%, at the end of the project time. Finally, it was concluded that, by increasing the percentage of injected solvent, there was an increasing in the oil recovery factor, reaching an improvement of 11 pp, considering an injection interval of 8 years.