Navigating underground using the Earth’s magnetic field

The Earth’s magnetic field is ubiquitous and is still widely used as a reference direction with relatively low-cost sensors. One particular area of application is underground, in directional drilling. As hydrocarbon fields become increasingly “busy” with historic wells, and the reservoir targets become smaller and smaller, the magnetic field estimates used to determine well positions need to be accurate and with well-defined uncertainties. In this poster we describe the magnetic referencing services the British Geological Survey provide in order to promote safe and efficient directional drilling, and the latest developments in defining the associated uncertainties.