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Give the definitions to an oil field and a natural gas field.



2. What difficulties do people face when establishing a field?

3. Can you show the largest oil and gas fields on the map?

4. Can you comment on the last statement in part I of the text?

I

An oil field is a region with an abundance of oil wells extracting oil from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometers across, full exploitation entails multiple wells scattered across the area. In addition, there may be exploratory wells probing the edges, pipelines to transport the oil elsewhere, and support facilities.

Because an oil field may be remote from civilization, establishing a field is often an extremely complicated exercise in logistics. For instance, workers have to work there for months or years and require housing. In turn, housing and equipment require electricity and water. Pipelines in cold areas may need to be heated. Excess natural gas needs to be burned off if there is no way to make use of it, requiring a furnace, and pipes to carry it from well to furnace. Thus, the typical oil field resembles a small self-contained city

More than 40,000 oil fields are scattered around the globe, on land and offshore. The largest are the Ghawar Field in Saudi Arabia and the Burgan Field in Kuwait, with more than 60 billion barrels (10 km³) estimated in each. Most oil fields are much smaller.

In the modern age, the location of oil fields with proven oil reserves is a key underlying factor in many geopolitical conflicts.

II

Oil and natural gas are produced by the same geological process: anaerobic decay of organic matter deep under the Earth's surface. As a consequence, oil and natural gas are often found together. In common usage, deposits rich in oil are known as oil fields, and deposits rich in natural gas are called natural gas fields.

In general, organic sediments buried in depths of 1,000 m to 6,000 m (at temperatures of 60 °C to 150 °C) generate oil, while sediments buried deeper and at higher temperatures generate natural gas. The deeper the source, the "drier" the gas (that is, the smaller the proportion of condensates in the gas).

The largest natural gas field is South Pars/Asalouyeh gas field, which is shared between Iran and Qatar. The second largest natural gas field is located in Novy Urengoy, Russia.

The life of a field is variable: in general from 15 to 30 years. Longer for a really big one (a super-giant with a life of 50 years or more), shorter for deep-sea fields (5 to 10 years) because of the very high operating costs. The total life consists of 3 stages: the initial period (2 to 3 years) with a growth in extraction quantities as wells are sunk one after another. Then a long steady period during which annual production is stable. Finally a period of reduction, which varies from field to field, before the final closure.

 

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