Changes

[[File:Well-completions_fig1.png|300px|thumb|'''Figure 1.''' Wellbore diagram of (a) an open hole completion and (b) a slotted liner completion.]]

[[File:Well-completions_fig1.png|300px|thumb|'''Figure 1.''' Wellbore diagram of (a) an open hole completion and (b) a slotted liner completion.]]

'''Open hole completions''' were originally used in the early days of the petroleum industry when most wells were drilled with [[cable tools]]. Normally, [[casing]] was run as the hole was drilled. When the formation was penetrated and oil and gas began to flow, drilling ceased and the well was produced as an open hole completion. As [[rotary rig]]s began to drill a majority of the wells, it was still common to complete a well using an open hole completion. If the well needed to be [[Stimulation|stimulated]], [[Wikipedia:Nitroglycerin|nitroglycerine]] was used to rubbleize the formation near the wellbore. [[:File:Well-completions_fig1.png|Figure 1(a)]] illustrates a typical wellbore diagram for an open hole completion. Although not common in most areas, open hole completions are still used today in certain situations, such as the [[Well types#Horizontal wells|horizontal well]] completions in the [[Austin Chalk]] and in the [[Devonian shale]]s in [[Wikipedia:Appalachia|Appalachia]]. In a typical open hole completion, casing is set prior to drilling into the producing interval. A [[Rock-water_reaction#Problem_prevention_and_correction|nondamaging fluid]] can then be used to drill into the pay section.

'''Open hole completions''' were originally used in the early days of the [[petroleum]] industry when most wells were drilled with [[cable tools]]. Normally, [[casing]] was run as the hole was drilled. When the formation was penetrated and oil and gas began to flow, drilling ceased and the well was produced as an open hole completion. As [[rotary rig]]s began to drill a majority of the wells, it was still common to complete a well using an open hole completion. If the well needed to be [[Stimulation|stimulated]], [[Wikipedia:Nitroglycerin|nitroglycerine]] was used to rubbleize the formation near the wellbore. [[:File:Well-completions_fig1.png|Figure 1(a)]] illustrates a typical wellbore diagram for an open hole completion. Although not common in most areas, open hole completions are still used today in certain situations, such as the [[Well types#Horizontal wells|horizontal well]] completions in the [[Austin Chalk]] and in the [[Devonian shale]]s in [[Wikipedia:Appalachia|Appalachia]]. In a typical open hole completion, casing is set prior to drilling into the producing interval. A [[Rock-water_reaction#Problem_prevention_and_correction|nondamaging fluid]] can then be used to drill into the pay section.

One important disadvantage of an openhole completion is that [[production casing]] must be set prior to drilling and logging the reservoir. If for some geological or engineering reason the target formation is not productive, then money has been spent to set casing in a well that may be [[Plugging|plugged]] as a [[dry hole]]. Another disadvantage is the lack of control that occurs when an open hole completion is made. One cannot control the flow of fluids from the reservoir into the wellbore nor the [[injection profile]] in an open hole completion. In addition, if the formation is not competent, [[/Drilling_problems#Hole_instability|sloughing]] zones can cave into the wellbore and restrict flow to the surface.

One important disadvantage of an openhole completion is that [[production casing]] must be set prior to drilling and logging the reservoir. If for some geological or engineering reason the target formation is not productive, then money has been spent to set casing in a well that may be [[Plugging|plugged]] as a [[dry hole]]. Another disadvantage is the lack of control that occurs when an open hole completion is made. One cannot control the flow of fluids from the reservoir into the wellbore nor the [[injection profile]] in an open hole completion. In addition, if the formation is not competent, [[/Drilling_problems#Hole_instability|sloughing]] zones can cave into the wellbore and restrict flow to the surface.

[[File:Well-completions_fig2.png|thumb|300px|'''Figure 2.''' Wellbore diagram of (a) a screen and liner completion and (b) a cement liner completion.]]

[[File:Well-completions_fig2.png|thumb|300px|'''Figure 2.''' Wellbore diagram of (a) a screen and liner completion and (b) a cement liner completion.]]

'''Liner completions''' are similar to [[Types_of_completions#Open_hole_completions|open hole completions]] in that [[casing]] must be set prior to drilling the producing interval. The advantage of a liner completion is that the drilling fluid system can be changed and a [[Rock-water_reaction#Problem_prevention_and_correction|nondamaging fluid]] used to drill the pay interval. Several types of liner completions are commonly employed in well completions. These include

'''Liner completions''' are similar to [[Types_of_completions#Open_hole_completions|open hole completions]] in that [[casing]] must be set prior to drilling the producing interval. The advantage of a liner completion is that the [[drilling fluid]] system can be changed and a [[Rock-water_reaction#Problem_prevention_and_correction|nondamaging fluid]] used to drill the pay interval. Several types of liner completions are commonly employed in well completions. These include

* Slotted liner

* Slotted liner

* Screen and liner

* Screen and liner

The slotted liner completion is similar to an open hole completion and has all the major advantages and disadvantages discussed for open hole completions. The only difference is that a slotted liner is hung in the open hole interval to minimize [[/Drilling_problems#Hole_instability|sloughing]] of the formation into the well bore ([[:Image:Charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_1.jpg|Figure 1b]]). A screen and liner completion is similar to the slotted liner completion in that a screen and liner is set in the open hole section of the wellbore. The difference is that gravel is sometimes placed behind the screen ([[:File:Well-completions_fig2.png|Figure 2a]]). The advantages and disadvantages are the same as for open hole completions. The screen and liner completion is used primarily in [[unconsolidated]] formations to prevent the movement of formation materials into the wellbore, restricting the flow of reservoir fluids.

The slotted liner completion is similar to an open hole completion and has all the major advantages and disadvantages discussed for open hole completions. The only difference is that a slotted liner is hung in the open hole interval to minimize [[/Drilling_problems#Hole_instability|sloughing]] of the formation into the well bore ([[:Image:Charles-l-vavra-john-g-kaldi-robert-m-sneider_capillary-pressure_1.jpg|Figure 1b]]). A screen and liner completion is similar to the slotted liner completion in that a screen and liner is set in the open hole section of the wellbore. The difference is that gravel is sometimes placed behind the screen ([[:File:Well-completions_fig2.png|Figure 2a]]). The advantages and disadvantages are the same as for open hole completions. The screen and liner completion is used primarily in [[unconsolidated]] formations to prevent the movement of formation materials into the wellbore, restricting the flow of reservoir fluids.

The cemented liner completion is used when [[intermediate casing]] is set in a well prior to reaching total depth ([[:File:Well-completions_fig2.png|Figure 2b]]). Many times intermediate casing is used to isolate zones behind pipe such as low pressured intervals that tend to cause [[Drilling_problems#Lost_circulation|lost circulation]] problems or to isolate zones such as sloughing shales or salt layers. Intermediate casing is also set in transition zones between normally pressured intervals and [http://www.glossary.oilfield.slb.com/en/Terms/g/geopressure.aspx geopressured] intervals. After the casing is set, the weight or chemistry of the drilling fluid can be changed to continue drilling the well. The cemented liner completion is advantageous because the particular intervals behind the liner can be selectively perforated. This selection will allow one to control both the production and injection of fluids in those intervals. he main disadvantage of a cemented liner is the difficulty encountered in obtaining a good primary cement job across the liner. If a good cement job is obtained, then a cemented liner completion is very similar to a perforated casing completion.

The cemented liner completion is used when [[intermediate casing]] is set in a well prior to reaching total depth ([[:File:Well-completions_fig2.png|Figure 2b]]). Many times intermediate casing is used to isolate zones behind pipe such as low pressured intervals that tend to cause [[Drilling_problems#Lost_circulation|lost circulation]] problems or to isolate zones such as sloughing shales or salt layers. Intermediate casing is also set in transition zones between normally pressured intervals and [http://www.glossary.oilfield.slb.com/en/Terms/g/geopressure.aspx geopressured] intervals. After the casing is set, the weight or chemistry of the [[drilling fluid]] can be changed to continue drilling the well. The cemented liner completion is advantageous because the particular intervals behind the liner can be selectively perforated. This selection will allow one to control both the production and injection of fluids in those intervals. he main disadvantage of a cemented liner is the difficulty encountered in obtaining a good primary cement job across the liner. If a good cement job is obtained, then a cemented liner completion is very similar to a perforated casing completion.

==Perforated casing completions==

==Perforated casing completions==

The more complex the completion, the more trouble one can expect in both completion operations and in subsequent [[Workovers|workover operations]]. Multiple completions should be considered only in special situations. These situations include areas where [[drilling costs]] are very high or where the area allocated for drilling wells is at a premium. Such areas include offshore areas, highly populated areas, and remote land locations.

The more complex the completion, the more trouble one can expect in both completion operations and in subsequent [[Workovers|workover operations]]. Multiple completions should be considered only in special situations. These situations include areas where [[drilling costs]] are very high or where the area allocated for drilling wells is at a premium. Such areas include offshore areas, highly populated areas, and remote land locations.

The main advantage of multiple completions is that two or more reservoirs can be simultaneously produced from a single wellbore. If all goes properly, the economics of using multiple completions can be attractive; however, operating and workover costs can be quite high. These operational factors must be considered when considering multiple completions.

The main advantage of multiple completions is that two or more reservoirs can be simultaneously produced from a single wellbore. If all goes properly, the [[economics]] of using multiple completions can be attractive; however, operating and workover costs can be quite high. These operational factors must be considered when considering multiple completions.

==Alternate completions==

==Alternate completions==

[[Category:Production engineering]] [[Category:Development geology]] [[Category:Test content]]

[[Category:Production engineering]] [[Category:Development geology]] [[Category:Test content]]