gas and oil, other materials extracted are salt, sand and water. When less oil is being extracted from the oil fields, more salt, sand and water will be extracted. Some oil fields extract mainly salt water, which makes up 99 percent of the liquid extracted. But you will find some oil and sand along with the extracted salt water, hence filtering is required. With the increased filtering process, the extraction costs increase until it becomes economically unfeasible to perform further extractions in an old oil field.

You cannot simply pump crude oil into your car engine to fuel it. The raw material contains many types of components known as fractions. Fractions can be very combustible; runny and light, or thick, heavy and inflammable like tar sludge. Others fall in between.

Many fractions mix together to form the crude oil. To be useful, crude oil must first be separated and converted, using the proper treatment, before it can be used commercially. This process takes place at the oil refinery.

Many products can be transformed from crude oil at an oil refinery. Here are some of them:

• Bitumen/tar: used in road surfaces as well as in roofing materials, it is a heavy liquid that is flammable
• Fuel oil: a heavy liquid produced by power stations that use oil and large industrial engines
• Lubricants: grease and oil based polishes
• Diesel
• Kerosene: used for jet fuel, heating oil and paraffin production
• Petrol/Gasoline
• Naphtha: used in plastics production
• Petroleum Gas: LPG and bottled gases production

A distillation tower is filled with hot crude oil and heated continuously. When the heat reaches the different oil densities, the crude oil is separated into various fractions according to the boiling point and weight where they are extracted.

Petrol and LPG, the lighter oils, evaporate quickly under heat to rise up the tower top, while diesel and kerosene stay at the middle. Lubricating oil and tar, the heavier liquids, sink to the tower’s bottom. The various fractions are then siphoned out for further treatment.

Although much of the crude oil is used for many other purposes, some can be used as fuels. But as petrol and gasoline demand is very high, oil refineries must create more fuel by some other means besides distillation. This means that some lesser quality but heavier oils will be put through catalytic cracking – a process that uses a lot of energy. The oils are filled into a reactor to be heated intensely until they reach a high pressure. The catalytic cracking process engages a catalyst to convert a lot of the heavy fractions into petrol or gasoline, the lighter fractions.

Another energy intensive process oil refineries use is called coking. This process breaks down the very heavy and thick fractions, like lubricating oil and tar, into lighter oils, while producing a coke residue – a hard and high carbon substance that is like coal. This product is used in the industry as fuel, in the same way that coal is used in many power stations. When petrol, diesel and gasoline are extracted, further treatments