Page 214 - Drilling Technology in Nontechnical Language

Chapter 9 – CASING AND CEMENTING 205

Fig. 9–4. Cutaway casing connection

Particular strain is placed on a connection where the casing is placed
in a curved section of wellbore. High tension combined with bending
forces and also internal forces place great strength requirements on the
connection threads.

Casing and tubing connections might not seal (just contain a thread), or
there may be O-ring or elastomer seals incorporated. For gas well service,
metal-to-metal seals are normally called for. These work by placing the two
metal seal areas in the pin and box in contact just before the connection is
fully screwed together. As the joint is torqued up, energy is placed into the
seals that causes some elastic deformation and creates a tight seal between
the metal faces.

Role of the Cement outside Casing

Casing is cemented in the annulus, either in just the lower part or
sometimes in the complete annulus. The cement is designed to meet a

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