It is a heavy dark liquid, consisting of many different hydrocarbon compounds. Crude oil is extracted from the ground and fractionated into its components by volatility in an oil refinery. Some of the main products distilled from crude oil are:
The following table compares the qualities of various types of petroleum:
|Fraction||API gravity|| Viscosity|
Petroleum has an organic origin, being generally believed to be formed from the remains of vegetable material.
Secular geologists have contended that petroleum is the remains of huge amounts of algal material that was laid down millions of years ago, and altered in form under high temperatures and pressures. Layers of buried plant material tend to produce coal or lignite.
Creationary geologists believe that petroleum was formed from organic material buried during the Noachian flood.
Recently, researchers have shown that natural gas can form rapidly, and that some is still being formed. This gives support to the creationary view. If this research is supported it would refute the idea that fossil fuels are diminishing.[Citation Needed] It has also been posulated that oil and natural gas are formed continuously by an abiotic process, deep inside the earth. These petroleum products constantly migrate from deep in the earth to the earth's crust where they can be effectively mined . If this hypothesis is supported by further evidence, the notion of petroleum as a limited resource would be refuted.
- Stainforth, J., Nourse, R. & Nosiara, M., 2007, Basin Oriented Geology - Petroleum Systems Module Course Manual.
- O’Donnell, E. 2005. “Rocks into Gas.” Harvard Magazine 107, no. 4.
- Gold, Thomas (1999). The deep, hot biosphere. Copernicus Books