Crude Oil

Crude oil – as petroleum directly out of the ground is called – is a remarkably varied substance, both in its use and composition. Crude oil is formed from the preserved remains of prehistoric zooplankton and algae, which have been settled to the sea (or lake) bottom in large quantities under anoxic conditions. It was formed over millions of years from the remains of tiny aquatic plants and animals that lived in ancient seas due to compression and heating of ancient organic materials over geological time. The oldest oil-bearing rocks, date back to more than 600 million years, the youngest being as old as about 1 million years.

Although various types of hydrocarbons – molecules made of hydrogen and carbon atoms – form the basis of all crude oils, they differ in their configurations. The chemical structure of petroleum is composed of hydrocarbon chains of different lengths. Because of this, petroleum may be taken to oil refineries and the hydrocarbon chemicals separated by distillation and treated by other chemical processes, to be used for a variety of purposes. It can be a straw-colored liquid or tar-black solid. Red, green and brown hues are not uncommon.

More About Crude Oil

Crude oil is typically obtained through drilling, where it is usually found alongside other resources, such as natural gas (which is lighter and therefore sits above the crude oil) and saline water (which is denser and sinks below). It is then refined and processed into a variety of forms, such as gasoline, kerosene, and asphalt, and sold to consumers.

Although it is often called "black gold," crude oil has ranging viscosity and can vary in color from black to yellow depending on its hydrocarbon composition. Distillation, the process by which oil is heated and separated in different components, is the first stage in refining.