| Oil wells usually refer to a vertical hole | | | | Oil wells can be drilled onshore or offshore. |
| drilled in the earth to find and extract | | | | Onshore wells are found on land, and are |
| petroleum oil and natural gas from the | | | | easier and less costly to drill and operate. |
| underground layers. Wells are generally | | | | Gas as the byproduct of oil extraction can |
| composed of a series of small holes and | | | | also be efficiently carried away through pipe |
| tubing and smaller holes within, encased in | | | | lines. Off shore wells target oil which is |
| cement, whereby perforations along the casing | | | | underground but also found under an ocean, |
| in the production zone enable the oil to flow | | | | away from land and shores. Shallow waters are |
| though rocks into the production casing. | | | | easier to drill into and operate wells on, |
| Inherent pressure is then enough to allow the | | | | whereas the logistics of the procedure become |
| oil and gas to flow to the surface. In case | | | | more complicated and expensive the deeper the |
| the pressure is not enough, other substances | | | | water is. |
| may be injected to stimulate it. | | | | |
| | | | Oil wells can be classified in different |
| Wells can produce three types of products. | | | | categories, according to their purpose. |
| Some produce only oil. Others produce both | | | | Production wells are drilled for oil |
| oil and natural gas. Others produce only | | | | production. Appraisal wells are used to |
| natural gas. However, wherever there is | | | | assess characteristics of a hydrocarbon |
| extraction of oil, there are high chances | | | | accumulation. Wildcat wells refer to wells |
| that there will also be natural gas present, | | | | dug in an area where not much is known of |
| as in the release of hydrocarbons when the | | | | hydrocarbon accumulation, and referred much |
| oil is extracted. Where demand for gas is | | | | to a random dig. These are not really used |
| present in the area of the drilling, pipes | | | | nowadays, since they were used for |
| conduct the gas to the supply lines. In | | | | exploratory and information purposes, which |
| places where the gas may not be carried away | | | | is now available through the efforts placed |
| for use, it used to be burnt. However recent | | | | in exploratory and appraisal wells. |
| environmental concerns have reduced this | | | | Regardless of the classification, is it these |
| occurrence of burning gas on the spot, and | | | | wells that help us to enjoy the standard of |
| the gas is often re-injected in the well to | | | | living that is far above what was known as |
| produce pressure. | | | | the norm even fifty years ago. |
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