Patent ID: 9133703
Filing Date: 2015-09-15
Classification: E21B,G01V

Abstract:
1. In a system including a steering tool that is moved by a drill string and steered in a way that is intended to form an underground bore along an intended path, beginning from a starting position, an apparatus comprising: a sensing arrangement, forming one part of the steering tool, for detecting a pitch orientation and a yaw orientation of the steering tool at a series of spaced apart positions of the steering tool along said underground bore, each of which spaced apart positions is characterized by a measured extension of said drill string such that each of the detected pitch orientation and yaw orientation are subject to a measurement error; at least one marker positioned 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 dipole field; a receiver, forming another part of the steering tool, for receiving the rotating dipole field with the steering tool at a current one of said spaced apart positions to produce magnetic information; and a processor that is configured 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 a last determined position as part of the series of spaced apart positions, with a given accuracy that compensates for said measurement error such that using only the detected pitch orientation, the detected yaw orientation and the measured extension of the drill string to determine the current position, without the magnetic information, would result in a reduced accuracy in the determination of the current location as said measurement error accumulates with each successive position in said series of positions, as compared to the given accuracy.