Evaluation of Smart Water Flooding in a Selected UAE Carbonate Oil Reservoir
Water flooding is by far the most common method of improved oil recovery applied in oil reservoirs. Water is the cheapest source of external energy that has been used over decades in water flooding schemes, provided that the formation damage does not adversely affect its infectivity. Displacement efficiency of water flooding can be significantly affected by crude oil/water/rock interactions. Historically, some consideration was given to such interactions in the practice of reservoir engineering. In recent years, extensive research in this area has documented that higher oil recoveries can be obtained when low-salinity water is injected in a formation with high salinity formation water. Hence, selecting a "smart water" with the proper salinity and ionic composition could be considered as a tertiary recovery fluid. While laboratory tests and historical field evidences validated this observation in carbonate reservoirs, the mechanism behind the observed incremental increase of oil recovery is still a topic of discussion. In this work, selected core samples from a carbonate reservoir were used to run flooding and spontaneous imbibition experiments at reservoir temperature and a potential smart water that could yield maximum oil recovery has been identified. Measurements of endpoint effective permeability along with chemical analysis of the effluents at the end of each core-flooding test were employed to suggest the likely mechanism for the incremental increase of oil recovery.