Low Sal/High Sal?: A New Promising Approach of EOR in Carbonate Reservoirs

Abstract Enhanced oil recovery (EOR), also referred to tertiary oil recovery, is becoming more critical in the industry as oil production from natural reservoirs is declining and its consumption is increasing. Conventional methods of oil production recover less than 30% of initial oil in place; therefore, EOR techniques are becoming more attractive to recover additional oil from the reservoirs. EOR is generally achieved by injecting either miscible or immiscible fluids into the reservoir including CO2 injection; others are thermal treatment, chemical/surfactant injection, ASP (alkaline-surfactant-polymer) injection and recently low salinity water injection (which is also called dynamic water, smart water and designer water). The main parameters to influence here is pressure, viscosity reduction and interfacial tension reduction, which all contribute to the increase of capillary number and therefore enhance the amount of recoverable oil. Despite some technological challenges, harsh reservoir conditions (carbonate complexity, high-pressure, high-temperature, high-salinity), stringent regulations, and costly implementation that kept oil companies away from using EOR techniques, it is expected that EOR will grow in the next few years and perform extremely well in the world market. However, some challenges remain in understanding the best EOR technique to be used for specific reservoir and what controlling parameters one should focus on for designing the best production/recovery scenario. However with the continuous increase of oil prices and world demand for oil, EOR is quickly becoming more feasible. It is also of interest because of current rising government interest and investment, new innovative technologies, and the availability of required materials such as CO2 and sea water. The market will continue to grow as more countries begin to see EOR results and as it becomes more feasible and common to oil producers.