This node will look briefly at the three types of oils: essential, fixed, and mineral oils, before going on to look at petroleum or crude oil in more depth. Drilling and refining oil will be described, followed by a discussion of political aspects of oil production in the world economy.

There are three main types of oils. Essential oils are obtained from plants, and have the odour of their plant source. They are often used in perfumes, flavourings, and aromatherapy. Fixed oils are obtained from animals and plants, and are mixtures of lipids, used as foods and lubricants and in making soaps, paints, and varnishes. Mineral oils are hydrocarbons used as fuels and lubricants and are mainly obtained by refining petroleum.

Petroleum or crude oil is a thick greenish-brown liquid found in permeable underground rock, and consisting mainly of hydrocarbons and mixed with other elements, especially oxygen, sulphur, and nitrogen. Petroleum is believed to have been formed from the remains of ancient living organisms deposited with rock-forming sediments. These have then been converted by the effects of heat, pressure, and bacterial action, and changed into petroleum. This liquid then migrated through porous rocks and fissures, becoming trapped in large underground reservoirs.

In order to locate and drill for oil, geologists first look for variations of rock density in the type of rocks where oil is known to occur. Exploratory drillings then confirm the presence of oil. Oil wells are made by drilling with a rotating bit supported in a wider shaft. A special mud is then pumped through the hollow bit to collect debris, which is forced back up the shaft around the drilling bit.

Petroleum is refined by a process known as fractional distillation, where components are separated according to their boiling points. The distillation fractions are then blended, producing products like fuel oil, petrol (gasoline), kerosene, diesel, and lubricating oil. Other processes such as catalytic cracking are used to increase the yield of petrol and reduce the viscosity of heavier oils. These processes lead to valuable petrochemicals used in detergents, plastics, and drugs.

The politics of oil

Worlwide dependence on oil has led to many attempts to control production levels and prices. The US drilled the first commercial well in Pennsylvania in 1859, and led in production until the 1960s when Middle Eastern reserves led to cheap oil and worldwide dependence. The Organisation of Petroleum Exporting Countries (OPEC) was formed in 1961 to protect member countries from exploitation. OPEC introduced price rises in 1973, and in 1974 the International Energy Agency (IEA) was formed to protect the interests of oil-consuming countries. North Sea oil and the Alaska pipeline have helped stabilise prices since then, but wars in Iran, Iraq, and Kuwait have heightened fears about unstable production levels. World oil reserves and future consumption are both difficult to estimate accurately.

The environmental impact of oil disasters cannot be overlooked. These disasters are some of the world's worst environmental catastrophes, and include the Torrey Canyon, Amoco Cadiz, and Exxon Valdez tanker spills, and the oil wells destroyed in Kuwait and Iraq in the Gulf War.

In summary, then, the impact of oil on the world's economy and the lives of individuals is a very important one, and one which has led to many attempts to gain control over oil production and prices.

The Hutchison Encyclopedia, 1997 ed., BCA