Are well used to stabilize the wall of a hole and meet high standards for:
- flexure (to transmit the axial stress)
- torsion (to resist to upper working stress)
- tensile strength (to counter-balance the string-load and to make easy retraction in case of pressing formations)
Casing is set easily while drilling water, reaming the hole, carries the cutting to the surface, in the space between tubes and hole wall.