Patent ID: 8983782
Filing Date: 2015-03-17
Classification: E21B

Abstract:
1. A method of guiding a probe to a target, the method including placing a magnetic field generator at the target; guiding the probe to a region of the target, the probe carrying a survey sensor pack; using the survey sensor pack to obtain a plurality of survey readings of a shape of a path of the probe relative to the target and a distance between readings of the survey sensor pack; using the survey sensor pack to obtain a plurality of magnetic beacon readings using a magnetic field generated by the magnetic field generator to determine a position of the path of the probe relative to, and past, the target; comparing a selected number of the survey readings in proximity to the target with a corresponding number of the magnetic beacon readings and determining a difference between each survey reading and its associated magnetic beacon reading to determine a spacing of the path of the probe at the position of the probe past the target; and withdrawing the probe to a position upstream of the target, compensating for that spacing and repositioning the probe so that, on a further pass of the probe towards the target, the probe is placed on a corrected path to intersect the target.