well (redirected from lets well enough alone)

well, aperture in the earth's surface through which substances in a natural underground reservoir, such as water, gas, oil, salt, and sulfur, can flow or be pumped to the surface. In the United States, until some years after the Civil War, the majority of wells were "open," i.e., holes dug in the ground and lined, or cased, with brick, stone, or wood. Although they are sometimes dug with picks and shovels, most wells today are made by rotary or percussion drills. An artesian well, the most desirable type of water well, is always drilled because rock layers must be cut through to reach the water. Oil wells are usually drilled using a rotary-drill method, in which a drilling bit set in the bottom of a drilling pipe is rotated by machinery on the ground level. As the cut deepens, more sections of pipe are fastened to the sections already in use. A special mixture called drilling mud is sent down through the pipe to wash away the drillings and also to cool the cutting bit. Some oil wells are drilled by a percussion method known as cable-tool drilling. In this procedure a heavy metal bit attached to a cable is alternately raised and dropped, pulverizing the rock beneath it. Water is pumped into the well and mixed with the rock cuttings, the mixture being bailed out when it becomes thick enough to interfere with the action of the bit. Regardless of the drilling method, well walls are usually cased with iron or steel to prevent cave-ins. Casing is inserted when the desired depth has been reached or, in some instances, as the well is being drilled. Minerals, such as salt and sulfur, can be pumped to the surface through a well if they are first liquefied by some process; for example, salt may be brought up if water is first pumped to the bottom of the well to dissolve the salt.

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well

1. a hole or shaft that is excavated, drilled, bored, or cut into the earth so as to tap a supply of water, oil, gas, etc.

2. a natural pool where ground water comes to the surface

3. 

a. a bulkheaded compartment built around a ship's pumps for protection and ease of access

b. another word for cockpit

4. a perforated tank in the hold of a fishing boat for keeping caught fish alive

5. (in England) the open space in the centre of a law court

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well [wel]

(building construction)

An open shaft in a building, extending vertically through floors to accommodate stairs or an elevator.

(engineering)

A hole dug into the earth to reach a supply of water, oil, brine, or gas.

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Well

An artificial excavation made to extract water, oil, gas, brine, or other fluid substance from the earth. Most wells are of the drilled type. Dug wells are almost obsolete, because of the greater speed of drilling and the greater efficiency of drilled wells.

Drilled wells, commonly 2–36 in. (5–90 cm) in diameter, usually are fitted with a steel tube or casing inserted in the drilled hole to the desired depth. Where the water-bearing formation is competent to stand without support, the casing is set, or finished, at the top of solid rock. Where there is danger of caving, as in sand or gravel, the casing is carrried below the top of the water-bearing bed, and a perforated pipe or screen extends below the casing to the bottom of the hole. The construction includes a considerable period of pumping, surging, or other treatment (called well development), during which the finer particles of the formation are drawn into the well and removed. This process substantially increases the initial yield of the well.

Most wells of large capacity are equipped with pumps of the deep-well turbine type to lift the water to the surface. When a well is pumped, the pressure head at the well is lowered and a hydraulic gradient toward the well is established which causes water to flow toward the well. This lowering of head is called drawdown. See Pumping machinery