Oil recovery potential for a heavy oil in unconsolidated sands under polymer flood in the UKCS

Heavy oil production on the United Kingdom Continental Shelf (UKCS) is set to increase with the new developments expected to come on-stream within ten years. It is estimated that 9 billion barrels of heavy oil resources are in-place. The next generation of fields have lower API in the range of 10-18°, with viscosities as high as 1,500cP, presenting significant technical challenges. Shallow Eocene sand reservoirs, such as Bressay and Bentley, are often unconsolidated, which results in significant potential for compaction if the reservoir voidage is not maintained. Initial work matched the Li et al. (2014) model performance and the main controls on reservoir compaction were identified as rock stiffness and rate of withdrawal with constant aquifer properties. The results suggest that without inclusion of the geomechanics model in both aquifer and polymer assisted recovery the oil recovery is underestimated for low values of reservoir stiffness. The overburden compacts the reservoir while oil is produced and the polymer decreases the mobility of water, thereby allowing the recovery of more oil. Therefore, we conclude that managed compaction should be actively used as a reservoir management tool for Eocene reservoirs in the UKCS in addition to the application of EOR technologies.