Page | 177 Ap1.3.1 MWD Tool Types ................................................................................................................................... 146 Ap1.3.2 MWD Error Sources .............................................................................................................................. 146 Ap1.3.3 MWD Weighting Functions ................................................................................................................... 147 Ap1.3.4 MWD Error Magnitudes ........................................................................................................................ 147 Ap1.3.5 Relative Contribution of the Various Error Terms ................................................................................ 148 Ap1.3.6 Revisions to the MWD Error Model ...................................................................................................... 149 Ap1.4 Gyro Error Model .......................................................................................................................................... 150 Ap1.4.1 Gyro Tool Types and Running Modes ................................................................................................... 150 Ap1.4.2 Gyro Error Sources ................................................................................................................................ 151 Ap1.4.3 Gyro Weighting Functions..................................................................................................................... 151 Ap1.4.4 Gyro Error Magnitudes ......................................................................................................................... 152 Ap1.4.5 Differences Between the Gyro and MWD Models ............................................................................... 152 Ap1.5 Error Model Implementation ........................................................................................................................ 152 Ap1.5.1 Algorithm Flow ...................................................................................................................................... 152 Ap1.5.2 High Level Flow Chart............................................................................................................................ 153 Ap1.5.3 Inputs Required..................................................................................................................................... 154 Ap1.5.4 Poorly Defined Functions ...................................................................................................................... 154 Ap1.5.5 Test Cases.............................................................................................................................................. 154 Ap1.5.6 Consistent Naming of Error Sources ..................................................................................................... 154 Ap1.5.7 Backward Compatibility ........................................................................................................................ 155 Ap1.6 Standardisation ............................................................................................................................................. 155 Ap1.6.1 Why Do My Standard ISCWSA Results Not Agree with Yours?............................................................. 155 Ap1.6.2 Non Standard Error Sources.................................................................................................................. 155 20. Anti-collision Techniques ....................................................................................................................................... 101 20.1 Minimum Separation Methods and Limits ....................................................................................................... 101 20.2 Definition of Separation Factor......................................................................................................................... 102 20.3 Separation Vector Method ............................................................................................................................... 102 20.4 Pedal Curve Method ......................................................................................................................................... 103 20.5 Scalar (Expansion) Method ............................................................................................................................... 103 20.6 Probability of Collision ...................................................................................................................................... 104 20.6.1 Difference between Separation Factor and Probability Based Rules ........................................................ 104 20.7 Acceptable Risk of Collision .............................................................................................................................. 104 20.8 A simplified Calculation of Probability of Collision ........................................................................................... 105 20.9 Anti-collision Scanning and Reporting .............................................................................................................. 106 20.10 The Ellipse of Uncertainty Report ................................................................................................................... 107 20.11 Safe Scanning Intervals ................................................................................................................................... 108 20.12 Travelling Cylinder Plot ................................................................................................................................... 109 20.12.1 Reading the Traveling Cylinder Plot ......................................................................................................... 109 20.13 Travelling Cylinder Options ............................................................................................................................. 110 20.14 s ng V “ op” g ms ............................................................................................................................ 112 20.15 Using Ladder Plots........................................................................................................................................... 113 21. Planning for Minimum Risk ............................................................................................................................... 114 21.1 Designing the wellpath ..................................................................................................................................... 115
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