The treatment of buckling is based on use of the fundamental equation for the reduced axial force at any point in the casing string. If the calculated reduced axial force exceeds the calculated buckling resistance, buckling of the casing is likely to occur. Methods of preventing buckling (by raising the top of cement, by use of centralisers or by applying surface forces) are described below.

It should be realised, however, that the onset of buckling is not synonymous with casing failure. The amount of buckling that can be tolerated can be estimated by post-buckling analysis involving a first-order calculation of the stresses caused by the geometry changes involved. Such calculations are complex, and detailed studies are only possible with the aid of computer tools.


Resistance to buckling

The buckling theory showed that for buckling to occur, the reduced axial force, Fa*, must be negative. However, it is not necessarily the case that buckling will occur if the reduced axial force is…

Post-buckling analyses

The onset of buckling does not necessarily mean pipe failure. The acceptability of buckled casing must be assessed in two ways, i.e. the resulting stresses in the casing wall, and the access through…

Fundamental equation for reduced axial force

By examining the reduced axial force, Fa*, in a casing string, the operating conditions under which the uncemented portion of the casing will buckle are defined. This leads directly to methods of…