Casing and tubing

Casing and tubing strings are the main parts of the well construction. All wells drilled for the purpose of oil or gas production (or injecting materials into underground formations) must be cased with material with sufficient strength and functionality.

Casing

Casing is the major structural component of a well. Casing is needed to:

• Maintain borehole stability
• Prevent contamination of water sands
• Isolate water from producing formations
• Control well pressures during drilling, production, and workover operations

Casing provides locations for the installation of:

• Blowout preventers
• Wellhead equipment
• Production packers
• Production tubing

The cost of casing is a major part of the overall well cost, so selection of casing size, grade, connectors, and setting depth is a primary engineering and economic consideration.

Casing strings

There are six basic types of casing strings:

• Conductor Casing
• Surface Casing
• Intermediate Casing
• Production Casing
• Liner
• Liner tieback casing