Oil and Gas
An "oil field" or "oilfield" is a region with an abundance of oil wells extracting petroleum (crude oil) from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres 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 inlogistics. This goes beyond requirements for drilling, to include associated infrastructure. For instance, workers require housing to allow them to work onsite for months or years. In turn, housing and equipment require electricity and water. In cold regions, pipelines may need to be heated. Also, excess natural gas may be burned off if there is no way to make use of it—which requires a furnace, chimney and pipes to carry it from the well to the furnace.
Thus, the typical oil field resembles a small, self-contained town in the midst of a landscape dotted with drilling rigs and/or the pump jacks, which are known as "nodding donkeys" because of their bobbing arm. Several companies, such as Hill International, Bechtel, Esso, Weatherford International, Schlumberger Limited, Baker Hughes and Halliburton, have organizations that specialize in the large-scale construction of the infrastructure and providing specialized services required to operate a field profitably.
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 (9,5×109 m3) estimated in each. Most oil fields are much smaller. According to the US Department of Energy (Energy Information Administration), as of 2003 the US alone had over 30,000 oil fields.
In the modern age, the location of oil fields with proven oil reserves is a key underlying factor in many geopolitical conflicts.
The term "oilfield" is also used as a shorthand to refer to the entire petroleum industry. However, it is more accurate to divide the oil industry into three sectors: upstream (crude production from wells and separation of water from oil), midstream (pipeline and tanker transport of crude) and downstream (refining and marketing of refined products).
Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxide, nitrogen, and/or hydrogen sulfide.It is formed when layers of decomposing plant and animal matter are exposed to intense heat and pressure over thousands of years. The energy that the plants originally obtained from the sun is stored in the form of chemical bonds in the gas
Natural gas is a fossil fuel used as a source of energy for heating, cooking, and electricity generation. It is also used as fuel for vehicles and as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals. It is a non-renewable resource
Natural gas is found in deep underground rock formations or associated with other hydrocarbon reservoirs in coal beds and as methane clathrates. Petroleum is another resource and fossil fuel found in close proximity to, and with natural gas. Most natural gas was created over time by two mechanisms: biogenic and thermogenic. Biogenic gas is created by methanogenic organisms in marshes, bogs, landfills, and shallow sediments. Deeper in the earth, at greater temperature and pressure, thermogenic gas is created from buried organic material.
When gas is associated with petroleum production it may be considered a byproduct and be burnt as flare gas. The World Bank estimates that over 150 billion cubic metres of natural gas are flared or vented annually. Before natural gas can be used as a fuel, it must be processed to remove impurities, including water, to meet the specifications of marketable natural gas. The by-products of this processing include: ethane, propane, butanes,pentanes, and higher molecular weight hydrocarbons, hydrogen sulfide (which may be converted into pure sulfur),carbon dioxide, water vapor, and sometimes helium and nitrogen.
Natural gas is often informally referred to simply as "gas", especially when compared to other energy sources such as oil or coal. However, it is not to be confused with gasoline, especially in North America, where the term gasoline is often shortened in colloquial usage to gas.
Oil and natural gas are produced by the same geological process according fossil fuel suggestion: anaerobic decay of organic matterdeep 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). Because both oil and natural gas are lighter than water, they tend to rise from their sources until they either seep to the surface or are trapped by a non-permeable layer of rock. They can be extracted from the trap by drilling