How Oil Well Drilling Works
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Preliminaries
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Oil reservoirs are located by trained, specialized geologists. They use seismic surveys, which involve planting and exploding underground charges. The sound waves created by these explosions can be read using instruments like a seismograph, and by studying the seismic response, a map of the geological structures in the surrounding area can be made. These maps are invaluable for predicting the location of oil.
Drilling
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Once a site is selected, a drilling rig is erected. This bores a 5 and 36-inch wide hole through the dirt and rock down to the oil reservoir. The drill mechanism is forced down by the weight of the drill piping on top of it, which is also used to pump in a drilling fluid called "mud." This "mud" can be anything from ordinary water, water with air bubbles added, or water mixed with polymers. The injection of "mud" into the drilling area creates the best working conditions for the drill through mixing up into its solution all of the crushed rock debris created by the drill. Once in the "mud," this debris is much more easily sucked up and sent to the surface for disposal. The piping is continuously assembled above the drill, lengthening as the drill digs deeper.
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Casing
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When the drilling stops, the casing begins. This can be as simple as installing a metal pipe down to the bottom of the bore hole, but it usually takes the form of concrete casing with the metal pipes serving as an interior liner. Truly complicated casings, used in unstable wells or those with potential high pressure problems, will use multiple widths of concrete and metal pipe casings, becoming progressively narrower as the well goes deeper.
Opening
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Once the well is cased, holes called perforations are drilled around the bottom of the bore hole, which allow the oil to drain out of the surrounding rock formations and into the well. In a newly tapped reservoir, the high underground pressure will be enough to draw oil out and bring it to the surface, as it is literally pushed up to release in an area of lower pressure. This is the cause of the legendary geysers of oil at new oil wells.
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References
Resources
- Photo Credit Wikimedia Commons
