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There are a number of different types of wells that can be drilled, and these are described below. A particular well type may be best suited or most economic in the efforts to drain a specific configuration of hydrocarbons. Various drilling strategies can be adopted to place wells in specific patterns with the aim of optimizing production from a field.

There are a number of different types of wells that can be drilled, and these are described below. A particular well type may be best suited or most economic in the efforts to drain a specific configuration of hydrocarbons. Various drilling strategies can be adopted to place wells in specific patterns with the aim of optimizing production from a field.

==Conventional wells==

==Conventional wells==

A typical operation is to sidetrack a well. This is where a well has already been drilled or partly drilled and there is a need to exit out of one side of the well to a different target. A sidetrack may be required if there is an object stuck in the original hole, which cannot be fished out. In producing fields, an existing well may be sidetracked if there is no further use for that well, e.g., the oil well has watered out. A window will be cut in the casing of the original well by a special milling assembly, and drilling will then proceed out of the window toward a new target.

A typical operation is to sidetrack a well. This is where a well has already been drilled or partly drilled and there is a need to exit out of one side of the well to a different target. A sidetrack may be required if there is an object stuck in the original hole, which cannot be fished out. In producing fields, an existing well may be sidetracked if there is no further use for that well, e.g., the oil well has watered out. A window will be cut in the casing of the original well by a special milling assembly, and drilling will then proceed out of the window toward a new target.

==Horizontal wells==

==Horizontal wells==

Coiled tubing is continuous, small-diameter steel pipe stored on a reel at the surface in lengths of up to 6000 m (19,685 ft) long. Coiled tubing can be used in place of drill pipe for new wells and short-length to medium-length horizontal sidetracks (typically with a step-out of less than 800 m [2625 ft]). A mud turbine and drill bit combination is used for coiled tubing drilling. The turbine is powered by the mud moving through it; the tubing itself does not rotate. The advantage of coiled tubing drilling is that the drilling operation is quicker than normal drilling in that the connection time involved with a jointed drill pipe is eliminated. The tubing is simply rolled in and out of the well.

Coiled tubing is continuous, small-diameter steel pipe stored on a reel at the surface in lengths of up to 6000 m (19,685 ft) long. Coiled tubing can be used in place of drill pipe for new wells and short-length to medium-length horizontal sidetracks (typically with a step-out of less than 800 m [2625 ft]). A mud turbine and drill bit combination is used for coiled tubing drilling. The turbine is powered by the mud moving through it; the tubing itself does not rotate. The advantage of coiled tubing drilling is that the drilling operation is quicker than normal drilling in that the connection time involved with a jointed drill pipe is eliminated. The tubing is simply rolled in and out of the well.

==Through tubing rotary drilling==

==Through tubing rotary drilling==

* [[Well completion]]

* [[Well completion]]

* [[Well planning]]

* [[Well planning]]

==References==

==References==

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==External links==

==External links==