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Saturday, 07 February 2015 06:20






Petroleum literally means "rock oil," from the Latin terms petra, meaning rock, and oleum, which means oil. Oil is actually formed from the remains of small organisms, such as algae, plankton and vegetation which lived tens or hundreds of millions of years ago in oceans and lakes. When these ancient organisms pass away, their remains settle on the bottoms of the oceans or lakes, and are covered by mud and sediment. The presence of oxygen with time helps organisms decay, but the small percentage of these dead organisms that led to formation of oil become compressed into oxygen deprived mud and rock. Over thousands of years, this layer of mud and sediment containing the organic matter is covered by many more layers created in the same manner, with pressure and heat exerted on the original layer becoming increasingly intense. Eventually, the sediment under intense pressure forms a solid rock, with the organic matter still contained within it. This rock is called the source rock.

Thus Oil and gas were formed by the anaerobic decay of organic material in conditions of increased temperature and pressure.

The layers of mud prevented air from reaching the organic material. Without air, the organic material couldn't rot in the same way as organic material rots away in a compost heap. As the layers of mud grew in thickness, they pushed down on the organic material with increasing pressure. The temperature of the organic material was also increased as it was heated by other processes going on inside the Earth.

Very slowly, increasing temperature, pressure and anaerobic bacteria - micro-organisms that can live without oxygen - started acting on the organic material. In this was the energy first given to the plants by the sun is transferred and the organic matter is changed into crude oil and gas.

After oil and natural gas were formed, they tended to migrate through tiny pores in the surrounding rock. Some oil and natural gas migrated all the way to the surface and escaped. Other oil and natural gas deposits migrated until they were caught under impermeable layers of rock or clay where they were trapped. These trapped deposits are where we find oil and natural gas today.

Oil and gas are called 'hydrocarbons' because they mostly contain molecules of the elements hydrogen and carbon.

Crude oil is a complex mixture of hydrocarbons with small amounts of other chemical compounds that contain sulphur, nitrogen and oxygen. Traces of other elements, such as sulphur and nitrogen, were also present in the decaying organic material, giving rise to small quantities of other compounds in crude oil.

Petroleum products are usually grouped into three categories: light distillates (LPG, gasoline, naphtha), middle distillates (kerosene, diesel), heavy distillates and residuum (heavy fuel oil, lubricating oils, wax, asphalt).


Liquefied petroleum gases are the light hydrocarbon fraction of the paraffin series, derived from refinery processes, crude oil stabilization plants and natural gas processing plants comprising propane (C3H8) and butane (C4H10) or a combination of the two. They could also include propylene, butylene, isobutene and isobutylene. LPG is normally liquefied under pressure for transportation and storage.

Motor gasoline

Motor gasoline is light hydrocarbon oil for use in internal combustion engines such as motor vehicles, excluding aircraft. Motor gasoline is distilled between 35°C and 215°C and is used as a fuel for land based spark ignition engines. Motor gasoline may include additives, oxygenates and octane enhancers, including lead compounds such as TEL (Tetraethyl lead) and TML (tetra-methyl lead).


Naphtha is a feedstock destined either for the petrochemical industry (e.g. ethylene manufacture or aromatics production) or for gasoline production by reforming or isomerisation within the refinery. Naphtha comprises material that distils between 30°C and 210°C.

Gas diesel oil

Gas/diesel oil includes heavy gas oils. Several grades are available depending on uses: diesel oil for diesel compression ignition (cars, trucks, marine, etc.), light heating oil for industrial and commercial uses, and other gas oil including heavy gas oils which distil between 380°C and 540°C and which are used as petrochemical feedstocks.


Kerosene (other than kerosene used for aircraft transport which is included with aviation fuels) comprises refined petroleum distillate intermediate in volatility between gasoline and gas/diesel oil. It is a medium oil distilling between 150°C and 300°C.

Aviation gasoline

Aviation gasoline is motor spirit prepared especially for aviation piston engines, with an octane number suited to the engine, a freezing point of -60°C, and a distillation range usually within the limits of 30°C and 180°C.


Asphalt/Bitumen is a sticky, black and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product; it is a substance classed as a pitch. The primary use of asphalt/bitumen is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

Paraffin waxes

Paraffin wax refers to a white or colourless soft solid that is used as a lubricant and for other applications. It is derived from petroleum and consists of a mixture of hydrocarbon molecules containing between twenty and forty carbon atoms. It is solid at room temperature and begins to melt above approximately 37 °C (99 °F).





Last Updated on Saturday, 07 February 2015 06:26

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