Patent ID: 7775301
Filing Date: 2010-08-17
Classification: E21B,G01V

Abstract:
1. A Method for a system including a steering tool that is intended to form an underground bore along an intended path by steering and said steering tool is moved by a drill string, beginning from a starting position, said method comprising: providing a sensing arrangement, forming one part of the steering tool, for detecting a pitch orientation and a yaw orientation of the steering tool; moving the steering tool sequentially through a series of spaced apart positions along said underground bore; characterizing each of the spaced apart positions by a measured extension of said drill string; arranging at least one marker, proximate to the intended path, for transmitting a rotating dipole field such that at least a portion of the intended path is exposed to the rotating magnetic dipole; receiving the dipole field using a receiver that forms another part of the steering tool, with the steering tool at a current one of said spaced apart positions on said portion of the intended path, to produce magnetic information; and configuring a processor for using the detected pitch orientation, the detected yaw orientation and the measured extension of the drill string in conjunction with the magnetic information, corresponding to the current one of the positions of the steering tool, to determine a current location of the steering tool, relative to said starting position, with a given accuracy such that using only the detected pitch orientation, the detected yaw orientation and the measured extension of the drill string to determine the current location, without the magnetic information, results in a reduced accuracy in the determination of the current location, as compared to the given accuracy and including using as steering tool process equations where X, Y and Z represent the axes of a global coordinate system, {dot over (X)} is a first derivative of X with respect to arc length along an axis of the drill string, {dot over (Y)} is a first derivative of Y with respect to arc length along the axis of the drill string, Ż is a first derivative of Z with respect to arc length along the axis of the drill string, φ is the pitch angle of the steering tool and β is the yaw angle of the steering tool, and using as a distance measurement equation for each marker, where D represents the distance between a particular marker M and the steering tool and X M , Y M , Z M represents the coordinates of the particular marker in the global coordinate system.