Patent ID: 9360579
Filing Date: 2016-06-07
CPC Classification: E21B,G01V

Claim Text:
1. An apparatus 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, said 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 each of a series of positions of the steering tool along said underground bore, each of which 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 a portion of the intended path is exposed to the rotating dipole field; a receiver, forming another part of the steering tool, configured for receiving the rotating dipole field to produce magnetic information; and a processor that is configured to determine a first position of the steering tool, that is not exposed to the rotating dipole field, with a given accuracy based on the detected pitch orientation, the detected yaw orientation and a measured extension of the drill string, subject to the measurement error, and to determine a second position of the steering tool, that is exposed to the rotating dipole field, with an enhanced accuracy, based on the magnetic information in conjunction with the detected pitch orientation, the detected yaw orientation and the measured extension of the drill string to compensate for the accumulation of the measurement error along said portion of the intended path.