Improving directional drilling accuracy using magnetic referencing techniques

Within the drilling industry there is a need for accurate positional referencing to improve target acquisition and collision avoidance. British Geological Survey (BGS) provides services that improve the accuracy of magnetic referencing, based on estimations of the local magnetic field direction along the drill path. Several sources influence the magnetic field direction, all of which can have a significant impact: the dominant core field, smaller scale crustal perturbations, and mostly irregular disturbances originating above the atmosphere. Each source presents its own challenges when estimating the field at the drilling site. We present BGS's techniques to meet these challenges and so provide a complete picture of the local magnetic field. The BGS Global Geomagnetic Model (BGGM) is an industry standard main field model based on millions of satellite data and is able to predict the evolution of the field in the near-term. Recent advances in core-flow modelling are now being included to enhance its predictive capability. In-Field Referencing (IFR) utilises the BGGM and the harmonic properties of total field anomalies from airborne or marine surveys to estimate the combined core and crustal field vector. Interpolation In-Field Referencing (IIFR) completes the picture by combining IFR with data from nearby observatories to estimate the real-time field at the drill site. Where no nearby observatories exist, BGS has worked in partnership with drilling companies to install one. Uncertainties in directional referencing are of crucial importance to the drilling industry. We provide confidence levels for BGGM, IFR, and IIFR based on comparisons with independent data.