Patent ID: 7889596
Filing Date: 2011-02-15
Classification: E21B,G01V

Abstract:
1. A method for determining the position of a drill bit comprising determining a starting position ( determining a position of each of a plurality of seismic wave detectors, recording, by means of the detectors, data relating to transient seismic waves generated at the drill bit, identifying, based on the seismic wave data from the detectors, events (k determining for each of the detectors a seismic wave propagation velocity between the drill bit and the respective detector, determining a plurality of relative positions of the drill bit, based at least partly on the seismic wave propagation velocities and differences in arrival time (t determining, based at least partly on the starting position ( wherein the method comprises determining for each of at least some of the detectors, a first seismic wave propagation velocity (v determining, based at least partly on first seismic wave propagation velocities relating to at least some of the detectors, a position of the drill bit at a second event (k determining a second seismic wave propagation velocity (v