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.
Crude oil is classified by the location of its origin (e.g. West Texas Intermediate, WT, Brent, Dubai or Minas) and often by its relative weight or viscosity (light, intermediate or heavy); refiners may also refer to it as `sweetâ€™,
which means it contains relatively little sulphur, or as `sourâ€™, which means it contains
substantial amounts of sulphur and requires more refining in order to meet current product specifications. The number of carbon atoms determines the oil's relative `weightâ€™ or density. Gases generally have one to four carbon atoms, while heavy oils and waxes may have 50, and asphalts, hundreds.
Crude oil from an area in which the crude oil's molecular characteristics have been determined and the oil has been classified are used as pricing references throughout the world. These references are known as Crude oil benchmarks.
After considering availability of indigenous crude oil, balance crude oil is required to be imported. IndianOil sources its crude oil requirement from Far East, Gulf region, Mediterranean, West Africa and Latin American sources.