tertiary recovery

Tertiary recovery, also known as enhanced oil recovery (EOR), refers to methods used to extract oil from wells that are nearly depleted. These techniques are more complex and costly than primary recovery, which relies on natural reservoir pressure, or secondary recovery, like waterflooding.12

EOR methods aim to recover oil left behind after initial extraction. This can involve injecting substances like natural gas or carbon dioxide (CO₂) to make the oil more fluid and easier to displace. Surfactants can also be used to reduce surface tension between the injected fluid and the oil, effectively "scrubbing" the oil from rock pores. Polymers may be added to injected water to increase its viscosity and prevent it from bypassing the oil. CO₂ EOR, in particular, can significantly improve recovery by reducing oil viscosity, causing oil swelling, and creating a dissolved gas drive.3