Introduction to Wellbore Positioning Web

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Table of Contents

Introduction to Wellbore Positioning Web

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- Introduction to Wellbore Positioning Web — 1

Introduction to Wellbore Positioning
- Copyright notice
- Revisions
- Acknowledgements
- Sponsors
- Introduction
1.0 Coordinate Systems and Geodesy
- 1.1 The Origin – Reference Surfaces and Elevations in Mapping
- 1.2 Principles of Geodesy – The forgotten Earth science
- 1.3 Principles of Cartography – It’s a ‘Square World’! Or is it?
2. Changing from One Map System to Another
- 2.1 Ellipsoids and datums
3. True North, Grid North, Convergence Summary & Exercises
- 3.1 Map projections
- Work Examples
4. The Earth’s Magnetic Field
- 4.1 Basic Outline
- 4.2 Variations in the Earth’s Magnetic Field
- 4.3 Magnetic Observatory Distribution
- 4.4 Diurnal Variation
5. Principles of MWD and Magnetic Spacing
- 5.1 Measurement While Drilling (MWD)
- 5.1 Data Recovery
- 5.2 MWD Magnetic Spacing
6. In-Field Referencing
- 6.1 Measuring Crustal Anomalies using In-field Referencing
  - 6.1.1 IFR Survey Maps
- 6.2 Interpolated In-field Referencing
7. Survey Calculation Methods
- 7.1 Examples of current methods
8. Survey Frequency
- 8.1 Determining TVD
- 8.2 Effect of Survey Interval on Well Path Positional Uncertainty
9. Gyro Surveying
- 9.1 Background and History of Gyros
- 9.2 Oilfield Applications – A Brief History
- 9.3 Chronology of gyro development
- 9.4 Improving Performance and Service Capability
- 9.5 The Gyro Survey Process
- 9.6 ERD and Horizontal Transit
- 9.7 Ring Laser Gyro
- 9.8 Fibre Optic Gyro
- 9.9 Vibrating Structure Gyroscope
- 9.10 Coriolis Vibratory Gyros (CVG)
  - 9.10.1 Micro electro mechanical System (MEMS) – Tuning Fork Gyro
  - 9.10.2 Hemispherical Resonator Gyro (HRG)
10. Basic Gyro Theory
- 10.1 Fundamental principles
- 10.2 Gyrodata Rate Gyro
- 10.3 Earth’s rate of Rotation
- 10.4 How to Measure Azimuth
- 10.5 Sensor Errors
- 10.6 Survey Tool Calibration
- 10.7 Survey Tool Operating Modes
- 11. When to run Gyros
- 12. Correcting for Sag
13. Correcting for Magnetic Interference
- 13.1 Drilling magnetisation
14. Multi Station Analysis
- 14.1 Calculation and background
15. Correcting for Pipe and Wireline Stretch
- 15.1 Forces on the drillpipe
- 15.2 Thermal Effects
- 15a Along Hole Depth Measurements
16. Human Error v Measurement Uncertainty
- 16.1 Common Human errors
- 16.2 Misapplication of Uncertainty in Top Hole
17. Understanding Error Models
- 17.1 Error Models and Instrument Performance Models
- 17.2 Modelling Uncertainty
- 17.3 Probability in two dimensions
- 17.4 How can we determine the size and shape?
18. The ISCWSA Error Model: Introduction
- 18.1 Some background to ISCWSA
- 18.2 Covariance
  - 18.2.1 How the errors affect the observations.
- 18.3 The Variance Covariance Matrix
- 18.4 Eigen Values and Eigen Vectors
- 18.5 Collision Risk
- 18.6 Definition of Ellipse Axes
- 18.7 How errors propagate
19. The ISCWSA Error Models: Explanation and Synthesis
- 19.1 Introduction
- 19.2 Framework of the Error Model
- 19.3 MWD Error Model
- 19.4 Gyro Error Model
- 19.5 Error Model Implementation
- 19.6 Standardisation
  - 19.6.1 Why Do My Standard ISCWSA Results Not Agree with Yours?
  - 19.6.2 Non Standard Error Sources
20. Anti-collision Techniques
- 20.1 Minimum Separation Methods and Limits
- 20.2 Definition of Separation Factor
- 20.3 Separation Vector Method
- 20.4 Pedal Curve Method
- 20.5 Scalar (Expansion) Method
- 20.6 Probability of Collision
  - 20.6.1 Difference between Separation Factor and Probability Based Rules
- 20.7 Acceptable Risk of Collision
- 20.8 A simplified Calculation of Probability of Collision
- 20.9 Anti-collision Scanning and Reporting
- 20.10 The Ellipse of Uncertainty Report
- 20.11 Safe Scanning Intervals
- 20.12 Travelling Cylinder Plot
  - 20.12.1 Reading the Traveling Cylinder Plot
- 20.13 Travelling Cylinder Options
- 20.14 Using TVD “Crop” Diagrams
- 20.15 Using Ladder Plots
21. Planning for Minimum Risk
- 21.1 Designing the wellpath
22. Basic Data QC
- 22.1 Checking raw data
23. Advanced Data QC
- 23.1 Varying curvature method
24. Tortuosity
- 24.1 Illustrating tortuosity
- 24.2 Calculating Tortuosity
25. Combined Surveys
- 25.1 Combined Surveys
26. Some Guidelines for Best Practice
- 26.1 Required Data
- 26.2 Position and Referencing Data
- 26.3 The Existing Well Data Including Survey Tools and Depth Ranges
- 26.4 Existing Planned Well to be Avoided (Caging)
- 26.5 Separation Rules
27. Relief Well Drilling
- 27.1 Magnetic Ranging
28. Subsea Positioning
- 28.1 GPS Positioning
- 28.2 DGPS
- 28.3 Vessel Offsets
- 28.4 Acoustic Positioning
- 28.5 Boxing In
- 28.6 USBL
- 28.7 Section Summary
29. Wellbore survey quality control
- 29.1 Introduction
- 29.2 Standardized confidence level
- 29.3 Georeference QC tests
- 29.4 Multi-station QC tests
- 29.5 Repeated measurement QC tests
- 29.6 Independent surveys QC tests
- 29.7 Recommended Use of QC Methods
- 29.8 Concluding remarks
- 29.9 References
30. Error model validation
- 30.1 Introduction
- 30.2 Discussion relating to survey type
- 30.3 Validation through determination of individual error parameters
- 30.4 Indirect validation through the comparison of independent surveys
- 30.5 References
APPENDICES
- Appendix A: Details of the Mathematical Derivations
- Appendix B: List of MWD Model Error Sources and Weighting Functions
- Appendix C: List of Gyro Model Error Sources and Weighting Functions
- Appendix D: Some Useful Mathematics
VERSION &SUBMISSION INFORMATION

Download as PDF

19. The ISCWSA Error Models: Explanation and Synthesis

18.7 How errors propagate

19.1 Introduction

*This chapter is included courtesy of Andrew McGregor of Tech21 Engineering Solutions, from a paper produced for ISCWSA. The text and associated appendices are taken from the paper:
The ISCWSA Error Models: An Explanation and Synthesis, version 11.

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