Patent ID: 9238959
Filing Date: 2016-01-19
CPC Classification: E21B

Claim Text:
1. An electromagnetic array configured for use in a subterranean borehole, the array comprising: a substantially cylindrical non-magnetic housing configured to be deployed in a subterranean borehole; at least first, second, third, and fourth, electromagnets deployed in the housing, the electromagnets being axially spaced apart and substantially co-axial with one another; a first subset of the electromagnets configured to generate magnetic flux in a first axial direction when connected with an electrical power source and a second subset of the electromagnets configured to generate magnetic flux in a second opposing axial direction when connected with the electrical power source such that a magnetic field pattern having at least first and second pairs of magnetically opposing poles is generated; and each of the first and second subsets includes at least two of the electromagnets; wherein at least the first electromagnets is electrically connected with a diode bridge which is configured to be connected with the electrical power source, the diode bridge being configured to provide an electrical current having a fixed polarity to the first electromagnet, irrespective of a polarity of the electrical power source; wherein at least the second electromagnet is configured to be connected directly with the electrical current source such that a polarity of electrical current provided to the second electromagnet is identical to a polarity of the electrical power source; and wherein the magnetic field pattern generated by the electromagnetic array (i) has a first non-zero number of the magnetically opposing poles when the electrical power source has a first polarity and (ii) has a second different non-zero number of the magnetically opposing poles when the electrical power source has a second opposite polarity, and wherein the magnetically opposing poles have the same magnetic polarity.