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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 wellartesian well,
deep drilled well through which water is forced upward under pressure. The water in an artesian well flows from an aquifer, which is a layer of very porous rock or sediment, usually sandstone, capable of holding and transmitting large quantities of water.
..... Click the link for more information. , 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. In natural gas wells drilled in relatively narrow bands of shale, horizontal drilling is used in combination with hydraulic fracturing, or "fracking," in which pressurized fluids are injected into the well to induce rock fractures that permit the release of greater quantities of gas.
a hydraulic-engineering structure in the form of a vertical shaft or hole. Wells are built to collect underground water for water supply and irrigation (intake wells), to replenish the supply of underground water with surface water or to collect drainage water and clarified sewage (filter wells), and to regulate the intake of water from rivers, lakes, and reservoirs (shore wells).
Intake wells, particularly for obtaining drinking water, are the most common type. A distinction is made between dug and Abyssinian wells, depending on the design and the method of construction and reinforcement of the walls. Dug wells are built for collecting water from unpressured, low-yield, shallow waterbearing strata. They are used to supply water to small settlements, livestock farms, field camps, and pastures; they are located in areas where the groundwater is suitable for drinking without purification. Dug wells most often have circular or square cross section; their diameter (or width) is usually 0.8–1.5 m, and they are up to 30–40 m deep. In the Northern Caucasus there are unique dug wells up to 100 m deep; in Turkmenia there are wells up to 300 m deep. Water enters a dug well through filters or walls made of porous concrete. The yield of most wells is 5–100 cu m per day. To increase the yield, radial horizontal drains (boreholes) up to 100 m long are made from pipe with filters.
In loose ground (sand and sandy loam), shafts are most often driven by hand and reinforced with a log frame, then plastered with cement over metal mesh, or thin reinforced-concrete slabs 50 cm high and 30–40 cm wide are laid, their reinforcement rods are joined, and the spaces between them and the wall are filled with cement (clad reinforcing). In sinking a well up to 30 m deep and 1 m in diameter in ground that does not collapse during excavation the well is dug with an excavator and then braced with reinforced-concrete rings joined by bolts or brackets. In rocky ground (limestone and marl), dug wells are not reinforced. The life of dug wells with wooden framing is 10–15 years; stone and concrete wells may last more than 25 years. Water is raised from them by various water-lifting devices.
Abyssinian wells are boreholes. They are built to bring up water from various depths, predominantly from abundant pressured and unpressured water-bearing beds. The water in such wells may rise above the water-bearing bed and even flow out onto the surface under its natural pressure (artesian wells). The depth of Abyssinian wells reaches 800 m; however, in the USSR, most of them are not deeper than 100 m. The yield is 0.5–50l/sec (sometimes higher). Abyssinian wells are significantly better than dug wells in terms of sanitary conditions. Water from them is used for centralized water supply. The walls of an Abyssinian well in unstable, friable rock are reinforced by strings of casing pipe that fit into one another. The pipe usually ends in the water-bearing bed and is capped by a filter, which may be made from porous concrete, ceramic, or gravel or of the screen, perforated, or rod type. Submersible centrifugal pumps, airlifts, and siphon intakes are used to lift water from Abyssinian wells. The life of Abyssinian wells is usually 10–15 years (sometimes up to 30 years).
Filter wells are used to drain landlocked depressions (a type of vertical drainage). By connecting a waterlogged bed to an absorbent bed by means of a filter well, excess water can be released into the absorbent bed. Filter wells are of both the dug and Abyssinian types.
A shore well is a chamber divided by a screen; water from a river or another source is delivered by pipe into the intake portion of the chamber.
REFERENCESPashenkov, la. M., N. A. Karambirov, and I. P. Gribanov. Sel’skokhoziaistvennoe vodosnabzhenie, burovoe délo i nasosnye stantsii, 2nd ed. Moscow, 1957.
Ovodov, V. S. Sel’skokhoziaistvennoe vodosnabzhenie i obvodnenie, 2nd ed. Moscow, 1960.
Gavrilko, V. M. Fil’try vodozabornykh, vodoponizitel’nykh i gidrogeologicheskikh skvazhin. Moscow, 1961.
I. S. NIKOLODYSHEV
What does it mean when you dream about a well?
The depth of emotional and spiritual resources, a well in a dream often represents knowledge and nurturance, a place from which emotions “well up.” It can also symbolize good health and physical well-being.
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