Drilled in the 90’s and resulting from multiple runs (with less than 10 truly different BHAs), this well is a typical HPHT well from the North Sea.
For well cases such as the one described in this case study, simple post-process of the BHA Sag raises interesting results.
The Sag analysis conducted on the diverse BHAs used to drill and survey this well showed:
Severe Sag issue at the position of the Azimuth & Inclination sensor in all the BHAs!
Results have shown significant Sag error within the vertical phase (26” Motor BHA).
The final vertical error in TVD at TD was about 10m below the measured trajectory.
BHAs Sag correction applied while drilling provides non negligible enhancement on the actual trajectory positioning,
Post-well correctionare of real added-value and absolutely required for the Geosciences (Subsurface and Reservoir Engineering) to optimize the well drain placements in TVD and enhance the access to HC reserves.
Additionally, improved wellbore positionning uncertainty allows at reservoir level for enhanced development patterns.