If we create an additional column in a spreadsheet to hold the changes in dls from one survey to the next, we can use that to calculate unwanted curvature induced in the wellbore. We do not need to know the well plan since any well plan will require constant curvature in each section and we are measuring the deviations from constant. By multiplying the change in dls (converted to degs/ft or degs/m) by the measured depth difference, we can simply add up the unwanted curvature in the wellpath. If the dls is unchanged, this process accumulates zero unwanted curvature.
Unwanted curvature is the sum of (dls change x md change). In the example above the unwanted curvature accumulation looks like this:
The design total curvature was only 27 degrees and the unwanted curvature is an additional 54 degrees or 200%. Anything over 100% would be considered tortuous and likely to cause casing and pipe problems.
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