Wellbore subsurface safety valve using a magnetic coupling

Abstract

A safety valve comprises a drive portion and an actuator portion. The drive portion comprises a first magnet assembly. A first magnetic field emitted from the first magnet assembly is biased towards a first operative side of the first magnet assembly. The first operative side is oriented toward a center of the wellbore. The actuator portion comprises a second magnet assembly magnetically coupled to the first magnet assembly.

1 . A safety valve comprising:
 a drive portion comprising a first magnet assembly, wherein a first magnetic field emitted from the first magnet assembly is biased towards a first operative side of the first magnet assembly and wherein the first operative side is oriented toward a center axis of the safety valve; and   an actuator portion comprising a second magnet assembly magnetically coupled to the first magnet assembly.   
     
     
         2 . The safety valve of  claim 1 , wherein a second magnetic field emitted from the second magnet assembly is biased towards a second operative side of the second magnet assembly and wherein the second operative side is oriented towards the first operative side. 
     
     
         3 . The safety valve of  claim 2 , wherein the first magnet assembly comprises a first spatially rotated array of magnets and the second magnet assembly comprises a second spatially rotated array of magnets. 
     
     
         4 . The safety valve of  claim 1 , wherein the first magnetic field being biased towards the first operative side of the first magnet assembly comprises the first magnetic field emitted from the first magnet assembly being non-zero on the first operative side and about zero on a non-operative side. 
     
     
         5 . The safety valve of  claim 4 , wherein the first magnetic field emitted from the first magnet assembly on the non-operative side is contained within a magnetic circuit. 
     
     
         6 . The safety valve of  claim 5 , wherein the magnetic circuit comprises a ferromagnetic backing plate located on the non-operative side of the first magnet assembly. 
     
     
         7 . A safety valve comprising:
 an outer housing;   a drive portion comprising a first magnet assembly and positioned within the outer housing;   an actuator portion comprising a second magnet assembly and positioned concentrically within the drive portion, wherein a first magnetic field emitted from the first magnet assembly is biased towards the actuator portion;   a pressure separator located between the drive portion and the actuator portion; and   a valve mechanism configured to be opened and closed by movement of the actuator portion.   
     
     
         8 . The safety valve of  claim 7 , further comprising a hydraulic input configured to apply hydraulic pressure to the drive portion, wherein the drive portion is configured to move linearly within the outer housing upon application of the hydraulic pressure. 
     
     
         9 . The safety valve of  claim 8 , wherein the actuator portion is configured to move linearly within the outer housing in response to the drive portion moving linearly within the outer housing via a magnetic coupling between the first magnet assembly and the second magnet assembly. 
     
     
         10 . The safety valve of  claim 7 , wherein the first magnet assembly comprises a spatially rotated array of magnets. 
     
     
         11 . The safety valve of  claim 10 , wherein the first magnet assembly comprises a backing plate located between the first magnet assembly and the outer housing, wherein the backing plate is configured to contain a first portion of the first magnetic field emitted from the first magnet assembly within a magnetic circuit. 
     
     
         12 . The safety valve of  claim 11 , wherein the first portion of the first magnetic field is about zero. 
     
     
         13 . The safety valve of  claim 7 , wherein the outer housing is composed of a ferromagnetic steel. 
     
     
         14 . The safety valve of  claim 7 , wherein the first magnet assembly comprises a receptacle enclosing a spatially rotated array of magnets, wherein the receptacle has a relative magnetic permeability of less than 10. 
     
     
         15 . A method comprising:
 placing a subsurface safety valve into a wellbore, wherein the subsurface safety valve comprises an outer housing, an actuator portion, and a drive portion;   causing the actuator portion of the subsurface safety valve to move in a first direction via a magnetic coupling between an actuator magnet assembly of the actuator portion and a drive magnet assembly of the drive portion of the subsurface safety valve; and   opening the subsurface safety valve via said causing the actuator portion of the subsurface safety valve to move in the first direction,   wherein a first magnetic field emitted by the drive magnet assembly is biased towards the actuator portion and the first magnetic field is oriented toward a center axis of the subsurface safety valve.   
     
     
         16 . The method of  claim 15 , wherein said causing the actuator portion of the subsurface safety valve to move in the first direction comprises applying hydraulic pressure to the drive portion and causing the drive portion to move in the first direction, wherein the magnetic coupling is configured to move the actuator portion in the first direction in response to the drive portion moving in the first direction. 
     
     
         17 . The method of  claim 15 , further comprising:
 causing the actuator portion of the subsurface safety valve to move in a second direction via the magnetic coupling; and   closing the subsurface safety valve via said causing the actuator portion of the subsurface safety valve to move in the second direction.   
     
     
         18 . The method of  claim 15 , wherein the first magnetic field being biased towards the actuator portion comprises the first magnetic field being non-zero on a first side of the drive portion and about zero on a second side of the drive portion, wherein the first side of the drive portion is adjacent to the actuator portion. 
     
     
         19 . The method of  claim 18 , wherein the second side of the drive portion is adjacent to the outer housing. 
     
     
         20 . The method of  claim 19 , wherein the outer housing is ferromagnetic.