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Casing that is cemented in place aids the drilling process in several ways: [2] Prevents contamination of fresh water well zones. Prevents unstable upper formations from caving in and sticking the drill string or forming large caverns. Provides a strong upper foundation to allow use of high-density drilling fluid to continue drilling deeper.
In a completed well, there may be many annuli. The 'A' annulus is the void between the production tubing and the smallest casing string. The 'A' annulus can serve a number of crucial tasks, including gas lift and well kills. A normal well will also have a 'B' and frequently a 'C' annulus, between the different casing strings.
A water resources borehole into the chalk aquifer under the North Downs, England at Albury. Engineers and environmental consultants use the term borehole to collectively describe all of the various types of holes drilled as part of a geotechnical investigation or environmental site assessment (a so-called Phase II ESA).
(pl.) aboiteaux A sluice or conduit built beneath a coastal dike, with a hinged gate or a one-way valve that closes during high tide, preventing salt water from flowing into the sluice and flooding the land behind the dike, but remains open during low tide, allowing fresh water precipitation and irrigation runoff to drain from the land into the sea; or a method of land reclamation which relies ...
A well-digging team digs under a cutting ring and the well column slowly sinks into the aquifer, whilst protecting the team from collapse of the well bore. Hand-dug wells are inexpensive and low tech (compared to drilling) and they use mostly manual labour to access groundwater in rural locations of developing countries.
Sometimes, the process of running in and cementing the casing is also included. After a well has been drilled, should the drilling fluids be removed, the well would eventually close in upon itself. Casing ensures that this will not happen while also protecting the wellstream from outside incumbents, like water or sand. [1] Perforated shoe
In subsurface hydrogeology, drawdown is the reduction in hydraulic head observed at a well in an aquifer, typically due to pumping a well as part of an aquifer test or well test. In surface water hydrology and civil engineering, drawdown refers to the lowering of the surface elevation of a body of water, the water table, the piezometric surface ...
Preserving well integrity is a vital task for the operators. This includes ensuring that the annuli remain intact. One major threat to annulus integrity is overpressure within the annulus, which could lead to burst or collapse of a casing or damage to the formation below. This will happen first at the shoe of the annulus because the pressure ...