This article describes the methods to quantify the different casing loads are presented. Internal and external pressure profiles are generally independent and therefore separate design loads will be generated.
The comparison of the internal and external pressure loads results in either a collapse load line or in a burst load line.
Collapse load
The collapse load at any vertical depth is the difference between the external pressure and the internal pressure at that depth.
Burst load
The burst load at any vertical depth is the difference between the internal pressure and the external pressure at that depth.
Formation load
Laterally moving formations, such as salt, exert a collapse loading on casing. The loading is generally modelled as a uniform fluid pressure load with a pressure equal to the overburden pressure. No account is taken of the non-unformity of these types of loads.
Near-vertical formation loads, such as compaction are complex and usually estimated using computer models.