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

Amir.Gergerechi@ptil.no