In-Field Referencing

What is it?

In-Field Referencing (IFR) is the provision of magnetic field estimates at a series of locations and dates along a planned well-path which include estimates of the crustal field from local observations.

The magnetic field estimates are derived from a global model, the BGS Global Geomagnetic Model (BGGM), and from local absolute observations of the geomagnetic field collected during an aeromagnetic or marine survey, or sometimes a ground-based survey.

If the local data are measurements of the strength of the field, as is usually the case with aeromagnetic and marine surveys, BGS has developed a method of estimating the direction of the field, important for directional drilling, from this type of data. This is reported in SPE paper 49061.

BGS has been providing IFR services since the mid-1990s and the following map shows all locations where IFR services are readily available from the BGS (restrictions may apply). If your field is not present BGS can source suitable local magnetic data and set the field up for IFR services.

What is it for?

In-Field Referencing 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 with high accuracy using IFR 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 rapidly varying external field using nearby observatory data. This enhancement is referred to as Interpolation In-Field Referencing (IIFR).

How accurate is it?

Location-specific error estimates are derived when a new field is set up for IFR.

Map of where BGS IFR services are readily available

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For further information please contact us.

Ellen Clarke - Project Leader