Enhanced oil recovery (abbreviated EOR) is the implementation of various techniques for increasing the amount of crude oil that can be extracted from an oil field. Enhanced oil recovery is also called tertiary recovery (as opposed to primary and secondary recovery). According to the US Department of Energy, there are three primary techniques for EOR: thermal recovery, gas injection, and chemical injection. Sometimes the term quaternary recovery is used to refer to more advanced, speculative, EOR techniques. Using EOR, 30 to 60 percent, or more, of the reservoir’s original oil can be extracted, compared with 20 to 40 percent using primary and secondary recovery.
Each oil field typically contributes 40% of the oil and gas production, which is an average amount. However, there are certain techniques that can be employed to extract all the identified oil from the reserve without losing it. These techniques are called Enhanced Oil Recovery (EOR). These techniques are used to enhance the recovery factor of the crude oil and improve the production of an oil well. There are basically three major techniques for enhanced oil recovery – chemical injection, gas injection and thermal injection. Gas injection method is the most used EOR technique, followed by thermal injection and chemical injection.