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BGS Global Geomagnetic Model

What is it?

The BGS Global Geomagnetic Model (BGGM) is a mathematical model of the Earth's magnetic field in its undisturbed state. It is revised every year to allow for the inclusion of new data collected since last revision and any development of the modelling methodology. With annual revisions it is also possible to minimise errors arising from predicting the field at some date after the time span of input data. The BGGM does not include the short-wavelength part of the crustal field or the rapidly varying external field.

What is it for?

The BGGM is widely used in the oil industry for directional drilling with Measurement-While-Drilling (MWD) magnetic survey tools. These tools measure the direction of the well-bore relative to the direction of the local geomagnetic field and are used to navigate wells towards precisely known underground targets. The local geomagnetic field is determined using the BGGM and the MWD data can then be used to give the drilling location in a geographic reference frame. An enhancement of this is to determine the local crustal field using either local absolute observations of the geomagnetic vector or transformation of local total intensity data collected during an aeromagnetic or marine survey. A further enhancement is to take account of the rapidly varying external field using nearby observatory data. These enhancements are referred to as In-Field Referencing (IFR) and Interpolation In-Field Referencing (IIFR) respectively.

How can I get it?

The model and associated software are available under licence from the BGS. Licence holders receive source code for incorporation into their own software throughout company, a Windows program for use throughout company, and documentation. Licence holders are invited to BGGM Users' Group/Geomagnetism Advisory Group meetings.

Install BGGM Software and Model 2017

Licence-holders for BGGM2017

Aker BP
Baker Hughes
Conoco Phillips
Lundin Norway AS
MS Energy Services
Scientific Drilling

How accurate is it?

Recent work on determining the accuracy of the BGGM (compared to "clean" downhole magnetometer measurements unadjusted for the local crustal fields and time-varying external fields) is reported in SPE paper 119851. The associated confidence limit files are available to download.

For further information please contact us at: bggm@bgs.ac.uk.

Susan Macmillan - Project Leader