Tuesday, 10 December 2019

CASING STRINGS TYPES USED IN DRILLING WELLS

OIL GAS CASING TYPES

TYPES OF CASING USED FOR OIL AND GAS WELLS

CONDUCTOR CASING PIPES

This string of casing which used on oil and gas wells, serves several purposes:
  1. To Prevent erosion around the rigs foundation where the surface sand is weak.
  2. To make the cellar more stable.
  3. To provide a good start for subsequent drilling 
  4. To circulate drilling fluids through to the surface.
  5. To protect inner casings from corrosion.

The conductor casing setting depth is usually based on the amount required to prevent washout of the shallow borehole when drilling to the depth of the surface casing and to
support the weight of the surface casing.

A diverter can be installed on the conductor to divert flow in case of a shallow kick. Normally when the surface sand is stable this string of casing is not necessary.

See also : Running procedures for 30" conductor Pipes

SURFACE CASING

This string of casing which used on oil and gas wells, serves several purposes:

  1. To protect shallow fresh water sands from possible contamination
  2. To prevent cave-in of unconsolidated, weaker, near surface sediments and in the event of a kick.
  3. To allow the flow to be contained by the BOP’s. 
  4. To support and protect from corrosion any subsequent casing strings run in the well. 

INTERMEDIATE CASING 

This string of casing which used on oil and gas wells, serves several purposes:
  1. Intermediate casing is similar to surface casing in that its function is to permit the final depth objective to be reached safely. 
  2. To isolate problem zones, i.e. abnormal pressured, lost circulation, sloughing or caving zones between the surface casing depth and the production casing depth.  
More than one intermediate string can be set if necessary.

See also : Casing Running and Cementing PreparationCasing running - installation patternsCasing Running Procedures

LINER 

A liner is a different type of casing profile in that it does not extend from the bottom of the well to the surface but is suspended from the bottom of the next largest casing string.

Normally it only extends a few hundred feet above the last casing shoe depth.  A liner can be used for drilling purposes to isolate problem zones or production or both. The principal advantage of the liner is its lower cost.

See also : Casing Running and Cementing PreparationCasing running - installation patternsCasing Running Procedures

PRODUCTION CASING

This string of casing is run across the production zone. Its purpose is to provide isolation between zones and in case a tubing leak occurs, it will contain the production fluid until remedial work can be performed to repair the leak.

See also : Casing Running and Cementing PreparationCasing running - installation patternsCasing Running Procedures


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