Extracting crude oil and natural gas When we refer to crude oil as a raw material for the chemical industry, we are usually referring to crude oil, which a mixture of hydrocarbons. Strictly, we should be using the term petroleum, derived from Latin petra - rocks and oleum – oil. Peak oil is the point in time when the maximum rate of crude oil extraction is reached, after which the rate of extraction is expected to begin to decline… forever.. It simply does not matter why peak crude oil extraction is reached, the peak is the peak regardless of the cause.