Oil, sometimes known as 'Black Gold', is a dark, thick liquid found underground or beneath the sea.
The great oil fields of the world, for example in the Middle East, in Texas and Mexico were formed millions of years ago when seas covered these areas. These were created by tiny sea plants and animals dying. These sank to the sea bed and were buried in mud. Over the millennia the mud turned to stone and the plants and animals were compressed by the weight of the rock on top of them and slowly turned into mineral oil.
Although we think of oil and the petrol that comes from it as a modern discovery, in fact the Chinese discovered oil more than 2,000 years ago. They even sunk drill holes to extract it. However, it was not until the mid 19th century that the first modern type of oil well was built in the USA. Since then the search for oil has spread all over the world.
The most familiar sight on a modern oil field is the derrick, or the drilling tower. This tall metal tower holds the drilling equipment. Down through the centre of the tower is the drill pipe, at the bottom of which is the bit. This has sharp teeth to cut through the layers of rock above the oil deposit. Scientists examine the fragments of rock and can tell from them how near they are to the oil. Sometimes when they reach the oil deposits, the oil gushes up in a great fountain, but more usually it has to be pumped up.
Once extracted from the ground, the crude oil is pumped along pipe-lines to the refining plant. Here the oil is separated into various qualities of oil, bitumen for road and, of course, petrol. The oil is also used in the manufacture of fertilizers, medicines, plastics and detergent.
The demand for oil is increasing all the time and scientists use the latest technology in their search for new fields. Geologists study satellite pictures of the Earth looking for the sort of geological areas that might cover an oil field. Other specialists are looking at ways of extracting oil from a rock called shale. At the same time engineers have built great derricks in the middle of the sea to extract oil detected there. However, all these sources of fuel are finite: they will run out eventually. So it is important to investigate other sources of energy, especially those that will not run out, such as solar power and wind power. Until a suitable alternative is found, however, the search for black gold will continue....
