- The weak point of a string won’t necessarily occur at surface and won’t necessarily occur in the smaller/weaker pipe either (if running a taper string).
- In the example shown the weak point does not occur at surface, nor does it occur in the “weaker” 4½” drill pipe.
- The weak point actually occurs at around 600’ with the tensile capacity of the string being reduced at this depth as a result of the string being subject to additional stress from already having to “bend” around the dogleg at ~600’
- It is important that the combined loads on a string be analyzed and the actual as drilled surveys taken into account. The example also illustrates the potential issues that can arise as a result of unplanned large shallow doglegs.
