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A dug well in a village in Faryab Province, Afghanistan The difference between a well and a cistern is in the source of the water: a cistern collects rainwater where a well draws from groundwater. A well is an excavation or structure created on the earth by digging, driving, or drilling to access liquid resources, usually water.
A tube well is a type of water well in which a long, 100–200 millimetres (3.9–7.9 in)-wide, stainless steel tube or pipe is bored underground. The lower end is fitted with a strainer, and a pump lifts water for irrigation. The required depth of the well depends on the depth of the water table.
A prolonged, recurrent axial and rotational movement within casing would cause wear to the casing interior, with the probability of blowouts, production loss, and other hazardous and costly complications. The following conditions contribute to casing wear: Drill pipe weight; Mud and additives; RPM and ROP; Tool joint coating; Well path and dogleg
Different methods of measuring the drill pipe length also have a significant effect on the accuracy of the measurement made. Pipe "strapping" is commonly used to define drill pipe length, where the pipe is measured on the pipe racks using a (steel) measure tape. These results are noted in a tally book, and the drillstring length is hence defined.
The well is therefore drilled in sections, with each section of the well being sealed off by lining the inside of the borehole with steel pipe, known as casing, and filling the annular space (or at least the lower portion) between this casing string and the borehole wall with cement.
Well drilling is the process of drilling a hole in the ground for the extraction of a natural resource such as ground water, brine, natural gas, or petroleum, for the injection of a fluid from surface to a subsurface reservoir or for subsurface formations evaluation or monitoring.
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The production liner has the same function as a complete string of production casing. A typical casing arrangement in a well is shown in the diagram below. In this case, the surface casing is set to a depth of about 3,000 ft (910 m). Two intermediate strings are set in this well — a 13 + 3 ⁄ 8 in (340 mm) string and a 9 + 7 ⁄ 8 in (250 mm ...