An oil well is a general term for any boring through the earthsurface designed to find and produce petroleum hydrocarbons Usually some natural gas is produced along with the oil, and a well designed to produce mainly or only gas may be termed a gas.the method in which taking oil is known as oil drilling.in earliest days oil wells have been drilled in china. The earliest oil wells were drilled by hammering a cable tool into the earth. Soon after, cable tools were replaced with rotary drilling, which could drill boreholes to much greater depths and in less time.
Now-a-days the usage of oil had increased. The use of deviated and horizontal drilling has also made it possible to reach reservoirs several kilometers or miles away from the drilling location (extended reach drilling), allowing for the production of hydrocarbons located below locations that are either difficult to place a drilling rig on, environmentally sensitive, or populated.
