Question

Enhanced oil recovery methods are necessary because

Answer 1

Enhanced oil recovery (abbreviated EOR), also called tertiary recovery, is the extraction of crude oil from an oil field that cannot be extracted otherwise. EOR can extract 30% to 60% or more of a reservoir's oil, compared to 20% to 40% using primary and secondary recovery. According to the US Department of Energy, there are three primary techniques for EOR: thermal, gas injection, and chemical injection. More advanced, speculative EOR techniques are sometimes called quaternary recovery.