Different type of casing and their function :
- It is run to prevent washout of near surface unconsolidated formation
- It provides a circulation system for the drilling mud.
- It ensure the stability of ground surface.
- It is run from the surface to a shallow depth to protect near surface unconsolidated formation.
- Seal off shallow water Zones
- It provide protection against shallow gas flow.
- It is run to prevent caving of weak formation that are encountered at shallow depth.
- It should be set in competent rocks such as hard limestone.
- It serves to provide protection against shallow blowout, hence BOPs are connected to the top of this string.
- It is usually set in the transition zone below or above an over pressured zone.
- It seal off a severe loss zone or to protect against problem formation.
- It is run to Isolate producing zone.
- It provide reservoir fluid control.
- It permits selective production in multizone production.
- It does not reach the surface.
- Liners are hung on the intermediate casing by use of a liner hanger.