Enhanced Oil Recovery (EOR) also referred as improved, extended or tertiary oil recovery. It is a method for increasing the amount of oil that can be extracted from depleted or high viscosity oil fields.
How is it important to us?
The three main EOR techniques are:
- Chemical flooding which involves the use of chemicals like polymers, surfactants, micellar/polymer, and alkaline/caustic substances to lower the surface tension that prevents the oil from flowing up. This technique is used in 1% of U.S EOR production.
- Thermal recovery which comprises the use of heat such as steam, hot water or in situ combustion to decrease the oil’s viscosity. 40% of U.S EOR production are thermal.
- Gas injection which uses gas such as natural gas, nitrogen (N2), carbon dioxide (CO2), hydrocarbon to push the oil throughout the reservoir. Gas injection constitutes more than 50% of worldwide EOR projects and more than 60% of U.S EOR projects.
Other EOR methods are: microbial injection and downhole seismic stimulation.
The optimal efficiency of each method depends on factors such as: the reservoir temperature, pressure, permeability, porosity and the fluid viscosity.
Enhanced Oil Recovery has a higher recovery rate than primary and secondary recovery: 30 to 60 % compared with 20 to 40 % using respectively primary and secondary recovery.
