Low Angle MWD Survey Errors
- Planned for ISCWSA Rev 5
XCL Formulation - Worst Case: Slide Rotate
- Andy Brooks method
- Worst case instantaneous change
- Equivalent to 3 sigma (99.9%)
- Divide by 3… for 1 sigma
- XCL = (MD2-MD1)*DL /6
- DL = Angle change Inc /Azi
- Problem: what happens when DL=0? straight sections
- Tortuosity 1 deg/100 - average
XCL Evidence: Open Hole Continuous Gyro Surveys in DP
- 83 Surveys reported at 10-ft intervals, high angle to horizontal. TD Difference normalized to ‘/1000’
XCL Error Formulation
- It’s a position error
- Not an angle error
- Split into Azimuth
- & Highside terms
- Error is 0.167 radians
- Tortuosity is 1°/100
Misalignment XYM Evidence - Survey Comparisons Gyro vs. MWD
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View the entire Presentation:
Jerry Codling – Halliburton Landmark