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|
Geologists have deduced 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.
Recently, researchers have shown that natural gas can form rapidly, supporting the idea that petroleum products could have been formed within the last few thousand years and is constantly being replenished, supporting the views of Young Earth Creationists. If this research is supported it would refute the idea that fossil fuels are diminishing.
- Stainforth, J., Nourse, R. & Nosiara, M., 2007, Basin Oriented Geology - Petroleum Systems Module Course Manual.