Well casing: Difference between revisions

Revision as of 23:51, 9 July 2026

A well casing is a lining that is installed in an oil or gas well after it is drilled and surrounds the wellbore. Casing typically consists hollow steel pipe that lines the inside of the wellbore.^[1] Casings are used to support the wellbore, preventing the surrounding rock and soil from collapsing into the well.^[2]

Figure 1. A diagram of a pump jack and wellbore, including a diagram of the well casing.^[3]

In addition to providing structural support, the casing also isolates the contents of the well from the surrounding rock and soil. This helps prevent the loss of oil or gas and reduces the risk of contaminating surrounding rock formations and groundwater. Cement is pumped into the space between the casing and the surrounding rock, where it hardens to form a seal that provides the primary barrier against fluid leakage and groundwater contamination.^[2] Protecting groundwater from contamination is an important consideration when drilling for natural gas or petroleum. Additionally, casing provides a conduit for fluids produced from the well and for fluids used during well operations and treatment.

Casing a Well

Well casing is installed in multiple sections. Each section of casing is referred to as a casing string.^[1] The casing is composed of steel and has a smaller diameter than the wellbore. Casing is installed in stages, beginning with the largest-diameter casing near the surface and progressing to smaller-diameter casing at greater depths. Each section of casing is connected using threaded collars or couplings.^[2] After the steel casing is installed, cement is pumped into the space between the casing and the surrounding rock to create a protective seal.^[2] The cement is pumped into the gap between the wellbore and the steel casing after the casing has been installed. Once hardened, the cement creates another barrier against fluid migration and helps secure the casing in place.

The thickness of the casing varies with depth and is determined by engineering requirements such as the pressures, loads, and geological conditions encountered throughout the well. Different sections of casing may have different wall thicknesses depending on the mechanical and environmental conditions at each depth, rather than solely on the surrounding rock type.

Capping a Well

Oil and natural gas wells can be abandoned when they no longer produce enough oil or natural gas to be economically viable. In this case, the well must be permanently sealed to ensure that it does not pose a risk to the environment after abandoned. The process of permanently sealing a well before abandonment is commonly known as well plugging and abandonment, although it is often referred to as capping the well. The first step involves cleaning the wellbore and removing any equipment so that permanent sealing materials can be installed. The well is then inspected to ensure the casing and cement barriers remain effective. Any deficiencies identified in the casing or cement must be repaired to ensure an effective seal. Cement plugs are then placed at strategic locations within the well to isolate underground formations and prevent the movement of fluids. Once the well has been permanently plugged, the casing is cut below ground level and a cap is installed. Typically, the casing is cut below ground surface, and a steel cap is installed to complete the abandonment process.^[4]

For Further Reading

References

↑ ^1.0 ^1.1 FracFocus. (October 18, 2015). Well Casing [Online]. Available: http://fracfocus.org/hydraulic-fracturing-how-it-works/casing
↑ ^2.0 ^2.1 ^2.2 ^2.3 Rigzone. (October 18, 2015). Well Casing [Online]. Available: http://www.rigzone.com/training/insight.asp?insight_id=333&c_id=24
↑ Wikimedia Commons. (October 18, 2015). Pump Jack [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/3/3f/Pump_Jack_labelled.png
↑ Alberta Energy Regulator. (November 2, 2015). Why are Wells Abandoned [Online]. Available: https://www.aer.ca/abandonment-and-reclamation/why-are-wells-abandoned

[RE2-1] 1.0 ^1.1 FracFocus. (October 18, 2015). Well Casing [Online]. Available: http://fracfocus.org/hydraulic-fracturing-how-it-works/casing

[RE1-2] 2.0 ^2.1 ^2.2 ^2.3 Rigzone. (October 18, 2015). Well Casing [Online]. Available: http://www.rigzone.com/training/insight.asp?insight_id=333&c_id=24

[3] Wikimedia Commons. (October 18, 2015). Pump Jack [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/3/3f/Pump_Jack_labelled.png

[4] Alberta Energy Regulator. (November 2, 2015). Why are Wells Abandoned [Online]. Available: https://www.aer.ca/abandonment-and-reclamation/why-are-wells-abandoned

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-<onlyinclude>A '''well casing''' is a lining that is installed in an [[oil well]] once it is drilled and surrounds the well entirely. Casing is typically hollow steel pipe that lines the inside of the [[wellbore]].<ref name="RE2">FracFocus. (October 18, 2015). ''Well Casing'' [Online]. Available: http://fracfocus.org/hydraulic-fracturing-how-it-works/casing</ref> Casings are used to support the well, as the raw sides of the well would collapse in without support.<ref name="RE1">Rigzone. (October 18, 2015). ''Well Casing'' [Online]. Available: http://www.rigzone.com/training/insight.asp?insight_id=333&c_id=24</ref></onlyinclude>
+<onlyinclude>A '''well casing''' is a lining that is installed in an [[oil well|oil or gas well]] after it is drilled and surrounds the [[wellbore]]. Casing typically consists hollow steel pipe that lines the inside of the wellbore.<ref name="RE2">FracFocus. (October 18, 2015). ''Well Casing'' [Online]. Available: http://fracfocus.org/hydraulic-fracturing-how-it-works/casing</ref> Casings are used to support the wellbore, preventing the surrounding rock and soil from collapsing into the well.<ref name="RE1">Rigzone. (October 18, 2015). ''Well Casing'' [Online]. Available: http://www.rigzone.com/training/insight.asp?insight_id=333&c_id=24</ref></onlyinclude>
 [[File:Pump_Jack_labelled2.png|400px|framed|center|Figure 1. A diagram of a [[pump jack]] and wellbore, including a diagram of the well casing.<ref>Wikimedia Commons. (October 18, 2015). ''Pump Jack'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/3/3f/Pump_Jack_labelled.png</ref>]]
-In addition to providing support, the casing also isolates the contents of the well from the surrounding rock and soil. This prevents a loss of product and prevents contamination of surrounding rock and groundwater. It is the concrete component - a mix of cement, sand, and aggregate mixed with water - of the casing that provides the most protection against leakage.<ref name="RE1"/> The contamination of groundwater is a concern when drilling either for [[natural gas]] or [[petroleum]]. Additionally, casing is used to transport fluids back out of the well from well treatment.
+In addition to providing structural support, the casing also isolates the contents of the well from the surrounding rock and soil. This helps prevent the loss of oil or gas and reduces the risk of contaminating surrounding rock formations and groundwater. Cement is pumped into the space between the casing and the surrounding rock, where it hardens to form a seal that provides the primary barrier against fluid leakage and groundwater contamination.<ref name="RE1"/> Protecting groundwater from contamination is an important consideration when drilling for [[natural gas]] or [[petroleum]]. Additionally, casing provides a conduit for fluids produced from the well and for fluids used during well operations and treatment.
 ==Casing a Well==
-The well casing is constructed in multiple sections. Each length of casing is referred to as a casing string.<ref name="RE2"/> The interior of the casing is composed of steel and is smaller than the diameter of the well. The casing of the well is accomplished in phases, beginning with the largest diameter casing and ending with the smallest. Each section of the casing is connected by a collar or coupling.<ref name="RE1"/> The exterior of the casing is made of concrete.<ref name="RE1"/> It is poured into the gap between the well and steel casing once it has been inserted. This creates another barrier layer and prevents the interior casing from shifting.
+Well casing is installed in multiple sections. Each section of casing is referred to as a casing string.<ref name="RE2"/> The casing is composed of steel and has a smaller diameter than the wellbore. Casing is installed in stages, beginning with the largest-diameter casing near the surface and progressing to smaller-diameter casing at greater depths. Each section of casing is connected using threaded collars or couplings.<ref name="RE1"/> After the steel casing is installed, cement is pumped into the space between the casing and the surrounding rock to create a protective seal.<ref name="RE1"/> The cement is pumped into the gap between the wellbore and the steel casing after the casing has been installed. Once hardened, the cement creates another barrier against fluid migration and helps secure the casing in place.
-The thickness of the casing varies depending on depth, with the casing being thicker near the top of the well where it is surrounded by soil and permeable rock that would easily transport contaminants if they were released. Near the bottom of the well, the casing is thinner as it is surrounded by solid, more [[permeability|impermeable]] rock that wouldn't transport contaminants as easily.
+The thickness of the casing varies with depth and is determined by engineering requirements such as the pressures, loads, and geological conditions encountered throughout the well. Different sections of casing may have different wall thicknesses depending on the mechanical and environmental conditions at each depth, rather than solely on the surrounding rock type.
 ==Capping a Well==
-Oil wells can be abandoned when they no longer produce enough [[oil]] or [[natural gas]] to be economically feasible. In this case, the well must be closed off properly to ensure that they do not pose a risk to the [[environment]] if abandoned. The process of closing off a well that is to be abandoned is known as '''capping the well'''. The first step in capping the well involves cleaning the wellbore of any oil or gas that could corrode the inside of the casing and reduce the effectiveness of any of the layers that prevent leakage. Any deficiencies identified in the casing itself must be repaired to ensure a tight seal. The well is then filled with water and other noncorrosive fluids. Once the inside of the well is prepared for abandonment, the well is cut and capped. In this process, the casing is cut one metre below the surface and a cap is placed on top of the well casing.<ref>Alberta Energy Regulator. (November 2, 2015). ''Why are Wells Abandoned'' [Online]. Available: https://www.aer.ca/abandonment-and-reclamation/why-are-wells-abandoned</ref>
+Oil and natural gas wells can be abandoned when they no longer produce enough [[oil]] or [[natural gas]] to be economically viable. In this case, the well must be permanently sealed to ensure that it does not pose a risk to the [[environment]] after abandoned. The process of permanently sealing a well before abandonment is commonly known as '''well plugging and abandonment,''' although it is often referred to as '''capping the well'''. The first step involves cleaning the wellbore and removing any equipment so that permanent sealing materials can be installed. The well is then inspected to ensure the casing and cement barriers remain effective. Any deficiencies identified in the casing or cement must be repaired to ensure an effective seal. Cement plugs are then placed at strategic locations within the well to isolate underground formations and prevent the movement of fluids. Once the well has been permanently plugged, the casing is cut below ground level and a cap is installed. Typically, the casing is cut below ground surface, and a steel cap is installed to complete the abandonment process.<ref>Alberta Energy Regulator. (November 2, 2015). ''Why are Wells Abandoned'' [Online]. Available: https://www.aer.ca/abandonment-and-reclamation/why-are-wells-abandoned</ref>
+== For Further Reading ==
+* [[Wellbore]]
+* [[Groundwater]]
+* [[Petroleum]]
+* [[Natural gas]]
+* Or explore a [[Special:Random|random page]]
 ==References==
 {{reflist}}
 [[Category:Uploaded]]