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22. Basic Data QC .................................................................................................................................................... 117 22.1 Checking raw data............................................................................................................................................. 117 23. Advanced Data QC .................................................................................................................................................. 118 23.1 Varying curvature method ................................................................................................................................ 118 24. Tortuosity ................................................................................................................................................................ 121 24.1 Illustrating tortuosity ........................................................................................................................................ 121 24.2 Calculating Tortuosity ....................................................................................................................................... 123 25. Some Guidelines for Best Practice .......................................................................................................................... 126 25.1 Required Data ................................................................................................................................................... 126 25.2 Position and Referencing Data.......................................................................................................................... 126 25.3 The Existing Well Data Including Survey Tools and Depth Ranges ................................................................... 127 25.4 Existing Planned Well to be Avoided (Caging) .................................................................................................. 128 25.5 Separation Rules ............................................................................................................................................... 128 26. Relief Well Drilling................................................................................................................................................... 130 26.1 Magnetic Ranging ............................................................................................................................................. 130 Some Practical Considerations.............................................................................................................................. 131 27. Subsea Positioning .................................................................................................................................................. 133 27.1 GPS positioning ................................................................................................................................................. 133 27.2 DGPS.................................................................................................................................................................. 133 27.3 Vessel Offsets .................................................................................................................................................... 134 27.4 Acoustic Positioning .......................................................................................................................................... 134 27.5 Boxing in............................................................................................................................................................ 135 27.6 USBL .................................................................................................................................................................. 135 Procedures for establishing offshore position. ..................................................................................................... 136 27.7 Points to Ponder ............................................................................................................................................... 136 APPENDICES .................................................................................................................................................................. 137 Appendix A: Details of the Mathematical Derivations .......................................................................................... 157 A1 - Details of the Propagation Mathematics....................................................................................................... 157 A2 - Details of the Error Summation Method ....................................................................................................... 160 Appendix B: List of MWD Model Error Sources and Weighting Functions ....................................................... 162 B1 - MWD Model Weighting Functions at Revision 3........................................................................................... 162 B2 - Historic Terms: No Longer Used in the MWD Model After Revisions 1 and 3 .............................................. 164 B3 - MWD Defined Error Magnitudes – Revision 3............................................................................................... 166 B4 - MWD Defined Error Magnitudes – Revision 3............................................................................................... 168 Appendix C: List of Gyro Model Error Sources and Weighting Functions ......................................................... 170 VERSION & SUBMISSION INFORMATION...................................................................................................................... 173 Submissions for assessment ..................................................................................................................................... 173 INDEX ............................................................................................................................................................................ 174
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