Petroleum is a naturally occurring liquid oil normally found in deposits beneath the surface of the earth. It is a type of oil composed of rock minerals, making it different from other kinds of oils that come from plants and animals (such as vegetable oil, animal fat, or essential oils). The word petroleum comes from the Latin words petra (rock) and oleum (oil), and so literally means rock oil. Despite this, petroleum is an organic compound, formed from the remains of microorganisms living millions of years ago. It is one of the three main fossil fuels, along with coal and natural gas.

Petroleum Economy

Petroleum, like all fossil fuels, primarily consists of a complex mixture of molecules called hydrocarbons (molecules containing both hydrogen and carbon). When it comes out of the ground, it is known as crude oil, and it may have various gases, solids, and trace minerals...