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
1.1.1. MSL, Elevation and Height
1.1.2. Coordinate Systems
1.1.3 Geographical coordinates
1.2 Principles of Geodesy – The forgotten Earth science
1.2.1 Geodesy
1.2.2 Geodetic Datum
1.2.3 Distortions in the Ellipsoidal Model
1.3 Principles of Cartography – It’s a ‘Square World’! Or is it?
1.3.1 Projection Categories
1.3.2 Mapping Parameters
1.3.3 Distortions in Mapping
1.3.4 Azimuth Distortion
1.3.5 Scale Distortion
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
5.2.1 Drill String Magnetic Interference
5.2.2 Pole Strength Values
5.2.3 Azimuth Error
5.2.4 NMDC Length Selection Charts
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
9.5.1 Surface Reference Orientation
9.5.2 Gyro Drift – Precession Correction
9.5.3 True Centre Correction (or Offset Centre Correction)
9.5.4 Tool Centralization
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
10.1.1 Gyroscopic inertia
10.1.2 Angular momentum
10.1.3 Precession
10.1.4 The application of the precession principle
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
10.7.1 Gyro-compassing mode
10.7.2 Continuous mode
10.7.3 Summary
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
15a.1 Discussion: Why Bother
15a.2 Calibration – Principles and Practice
15a.3 Pipe Properties Versus Cable Properties
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
19.1.1 Assumptions and Limitations of the ISCWSA Model
19.1.2 References in this chapter
19.1.3 Abbreviations
19.1.4 Nomenclature
19.1.5 Definition of Axes
19.2 Framework of the Error Model
19.2.1 Overview of the Error Model
19.2.2 Error Sources
19.2.3 Error Magnitude
19.2.4 Weighting Functions
19.2.5 Error Propagation
19.2.6 Summing Error Terms and Propagation Modes
19.2.7 Transformation to Borehole Axes
19.2.8 Bringing It All Together
19.2.9 Bias Terms
19.3 MWD Error Model
19.3.1 MWD Tool Types
19.3.2 MWD Error Sources
19.3.3 MWD Weighting Functions
19.3.4 MWD Error Magnitudes
19.3.5 Relative Contribution of the Various Error Terms
19.3.6 Revisions to the MWD Error Model
19.4 Gyro Error Model
19.4.1 Gyro Tool Types and Running Modes
19.4.2 Gyro Error Sources
19.4.3 Gyro Weighting Functions
19.4.4 Gyro Error Magnitudes
19.4.5 Differences Between the Gyro and MWD Models
19.5 Error Model Implementation
19.5.1 Algorithm Flow
19.5.2 High Level Flow Chart
19.5.3 Inputs Required
19.5.4 Poorly Defined Functions
19.5.5 Test Cases
19.5.6 Consistent Naming of Error Sources
19.5.7 Backward Compatibility
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
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19.2.7 Transformation to Borehole Axes
19.2.6 Summing Error Terms and Propagation Modes
19.2.8 Bringing It All Together
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