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5.
MWD Toolface Independent Error Terms S. Grindrod CDR-SM-03 Rev4 November 2009 available at www.iscwsa.org
6. Confidence Limits Associated with Values of the Earth's Magnetic Field used for Directional Drilling Susan Macmillan, Allan McKay, Steve Grindrod SPE/IADC-119851 7. A Comparison of Collision Avoidance Calculations Shola Okewummi, Andrew Brooks SPE/IADC-140183 8. Borehole Position Uncertainty; Analysis of Measuring Methods and Derivation of Systematic Error Model Chris J.M. Wolff and John P. DeWardt SPE-9223
Ap1.1.3
Abbreviations
BGGM
British Geological Survey Global Geomagnetic Model Highside – Lateral – Alonghole Co-ordinate system
HLA
IFR
In Field Referencing
IPM IGRF
Instrument Performance Model
International Geomagnetic Reference Field
ISCWSA
Industry Steering Committee for Wellbore Survey Accuracy
MWD
Measurement Whilst Drilling
NEV RSS SPE
North – East – Vertical Co-ordinate system
Root Sum Square
Society of Petroleum Engineers
Ap1.1.4 Nomenclature The following variables are used in the weighting functions: A m magnetic azimuth A true azimuth B magnetic total field B H horizontal component of magnetic field D along-hole depth Δ along-hole depth between survey stations G E h’sg y I inclination α toolface angle E h’s o on latitude Θ magnetic dip angle γ xy-accelerometer cant angle f
noise reduction factor for initialisation of continuous surveys
k
logical operator for accelerometer switching
v d
gyro drift
v rw
gyro random walk
w 12 w 34
misalignment weighting term misalignment weighting term
Ap1.1.5 Definition of Axes For clarity the following axes sets are used in the error model:
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