Reserves of natural gas and oil were discovered beneath the North Sea in the 1960s. To allow these reserves to be developed fairly, the countries bordering the North Sea established median lines to divide up the sea bed.
Gas was discovered in the UK sector of the North Sea in the West Sole field in 1964 and started to come ashore in 1965. Oil was discovered in the Ekofisk field in the Norwegian sector in 1971. The first oil in the UK sector was produced from the Argyll field and started flowing in 1975.
The first fields to be developed were those in shallower waters (50-100 metres deep). However, as the price of oil rose in the 1970s, and technology improved, it became both possible and worthwhile to develop oil fields in deeper water (up to 200 metres deep). Announcements have been made of developments to the west of the Shetland Isles where the water depth is over 400 metres.
The right to search for and extract oil and gas is controlled by the government. For the purpose of granting licences, areas of the sea bed are divided into quadrants - an area covering 1º of latitude by 1º of longitude. These quadrants are further divided into 30 blocks.
The government department granting licences takes into account many factors. Companies are judged not only on their technical and commercial capability but also on their environmental performance.
Licences are conditional on a company's taking special measures to protect the environment and to meet the needs of fishing, transport and other interests. An analysis of possible effects on the environment is required, so that steps can be taken to reduce these to an acceptable level.
The search for oil is a highly technical, lengthy and expensive activity. However, the only way of proving whether oil is there or not is to drill a well.
Once oil or gas is found in quantities worth developing, and government approval is received, further wells are drilled. Equipment may be located on the sea bed, or new production facilities put in place.
The mixture of oil and gas reaching the surface is often contaminated with water and solid material. The oil and gas are separated from each other and transported to onshore terminals or refineries by tanker or pipeline.
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* Wytch Farm is an onshore field in Dorset. |
Some oil from the Norwegian sector (notably the Ekofisk field) is piped to onshore terminals in the UK.
How long will the oil and gas last?
This is a very difficult question to answer. Estimates of the world's proven oil reserves have actually increased over the last few years, despite the continuing extraction of oil.
This is partly because new fields are being discovered. It is also because new technology makes it possible to get more out of existing oil fields and reach into previously inaccessible sources or those which were formerly uneconomic to develop using the technology available at the time.
The recovery factor (the amount that can be extracted compared to the total amount within the ground) varies widely. Twenty years ago, recovery factors were about 30 per cent. Today, the industry standard has reached 45 per cent. Perhaps new methods and improved technology will further increase the amount which can be recovered from each field.
Compared to countries like Saudi Arabia, our UK reserves of oil and gas are small. There are possibilities that new finds will be discovered in the North Sea and to the west of England, Wales and Scotland.
As well as producing a valuable resource, the oil and gas industry also creates much economic activity in associated industries. North Sea discoveries meant that shipyards were turned over to building the huge production platforms required. Pipelines were manufacture and laid, and onshore receiving and processing terminals were built.
The employment opportunities in steelworks, shipyards, refineries, supply, service and maintenance companies grew. Companies set up at the start of the boom are now established and sell their equipment and expertise to other countries overseas.
In the 1970s ports chosen as onshore bases experienced rapid expansion. Aberdeen was known as a "boom town". Many people moved into the area and house prices rose rapidly, rivalling those in London as the most expensive in Britain.
a) a dock worker
b) a builder
c) a secondary school pupil
d) a taxi driver