Oil recovery refers to the process of extracting crude oil from underground reservoirs. This involves drilling wells into the earth to access oil deposits, which can be found in various geological formations. The extraction methods can be categorized into primary, secondary, and tertiary recovery techniques, each utilizing different technologies to maximize oil yield. Primary recovery relies on natural pressure to push oil to the surface, while secondary recovery often involves injecting water or gas to maintain pressure. Tertiary recovery, also known as enhanced oil recovery, uses advanced techniques like thermal methods or chemical injections to further increase extraction efficiency.