Weak Points

• 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’
• Its 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.

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