Patent ID: 7816922
Filing Date: 2010-10-19
Classification: E21B

Abstract:
1. A method for surveying a borehole having a known or predictable magnetic profile, said profile resulting from controlled magnetization of wellbore tubulars, the method comprising: (a) positioning a downhole tool having a magnetic field measurement device in the borehole, said tool positioned within sensory range of a magnetic field from a target well, wherein (i) the target well comprises a plurality of magnetized wellbore tubulars positioned in the target well, each magnetized wellbore tubular having at least one pair of opposing magnetic poles located between longitudinally opposed ends of the wellbore tubular, and said magnetized wellbore tubulars coupled to one another; (b) measuring a local magnetic field using the magnetic field measurement device; and, (c) processing the local magnetic field measured in (b) to determine at least one of (i) a distance or (ii) a direction from the borehole to the target well.