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Positional Uncertainty for Measurement While Drilling (MWD) in the Barents Sea
Amir Gergerechi
Petroleum Safety Authority Norway
Objective of Study
Objective of Study
Present challenges related to positional uncertainties for
directional drilling using MWD in the Barents Sea,
specifically for deviated wellbores.
Mitigating solutions to these challenges
BACKGROUND
Well positioning
Anti-collision
Well control
Relief well
Background
Vertical vs Horisontal
Magnetic directional surveying
Source: The Artic University of Norway
Industry Steering Committee on
Wellbore Survey Accuracy (ISCWSA)
The Operator’s Wellbore Survey Group (OWSG), A sub-committee of ISCWSA
Produces a set of industry-standard error models
These error models, commonly called "tool codes", represent the expected uncertainties when using various technologies and methods
Ellipses of Uncertainty (EOU)
RESULT
Earth’s magnetic crustal
anomalies, 3D heatmap
Crustal VariationThe Earth’s crust contains magnetic minerals
Crustal anomalies is usually the biggest source of error for geomagnetic measurements
Crustal Variation(IFR1)
IFR 1: Models local
variations using air or
shipborne magnetic
measurements
Solar storm and Earth’s magnetic field
Diurnal Variation (IFR2)
Interpolated In-Field Referencing IFR2
The Earth’s magnetic field extends into space where it
meets solar winds (charged particles from the sun)
Measuring real time magnetic disturbance field
Total magnetic field(IFR1+IFR2)
Earth's magnetic field
RECOMMENDATIONS
RECOMMENDATIONS
IFR1 requires detailed magnetic maps over the entire area of interest
IFR2 adds a real-time magnetic observatory within 50 km of the drilling site
Good drilling practices and attention to the magnetic properties of the
drilling assembly reduce positional uncertainty to acceptable levels.
The positional uncertainty can be reduced as much as 60 percent compared
with standard MWD surveying
Heat map of distances to the nearest observatory
Thank you for attention