Downhole device actuator and method

Abstract

A temperature activated actuator installed on a tubular to actuate an adjacent device may include one or more shape-memory alloy elements. The elements may be coupled between a first portion and a second portion of a device, or the elements may be coupled between the tubular and a portion of the device. The elements are activated by raising the temperature to a transition temperature to cause metallurgical phase transformation, causing the elements to shrink and displace at least a portion of the device. The actuator may be used, for example, to actuate a centralizer from a run-in mode to a deployed mode or, alternately, to actuate a packing member from a run-in mode to an isolating mode. A nickel-titanium alloy, for example, may be used as the shape-memory alloy material from which the shape-memory element is made.

What is claimed is: 
     
         1 . An apparatus for use in a wellbore, comprising:
 a radially-expandable member comprising first and second axial ends, the first and second axial ends being offset from one another along a longitudinal axis of the radially-expandable member, the longitudinal axis being generally parallel to the wellbore when the radially-expandable member is positioned in the wellbore;   a first collar disposed adjacent the first axial end of the radially-expandable member;   a second collar disposed adjacent the second axial end and of the radially-expandable member; and   one or more shape memory elements extending between the first and second collars, wherein the one or more shape memory elements are configured to contract along the longitudinal axis and adduct the first and second collars toward one another when a temperature of the one or more shape memory elements reaches a transition temperature, wherein the first and second collars are configured to bear on the first and second axial ends, respectively, of the radially-expandable member when the one or more shape memory elements contract, so as to radially expand the radially-expandable member.   
     
     
         2 . The apparatus of  claim 1 , wherein the radially-expandable member comprises a packing element of a packer. 
     
     
         3 . The apparatus of  claim 1 , wherein the radially-expandable member comprises a rib of a centralizer. 
     
     
         4 . The apparatus of  claim 1 , wherein at least one of the one or more shape memory elements couples to the first collar at a position that is circumferentially offset from a position at which the at least one of the one or more shape memory elements couples with the second collar, such that adducting the first and second collars causes the first collar to rotate relative to the second collar. 
     
     
         5 . The apparatus of  claim 1 , wherein the first and second axial ends are annular in shape and extend substantially perpendicular to the longitudinal axis, the first and second collars being configured bear on the first and second axial ends, respectively, in a face-to-face engagement. 
     
     
         6 . The apparatus of  claim 5 , wherein the first and second axial ends are forced closer together along the longitudinal axis when the first and second collars are adducted. 
     
     
         7 . The apparatus of  claim 1 , wherein at least one of the one or more shape-memory elements comprises a nickel-titanium alloy. 
     
     
         9 . The apparatus of  claim 1 , wherein the first collar is secured in position on the tubular, and the second collar is movable relative to the tubular by contraction of the one or more shape-memory elements. 
     
     
         10 . The apparatus of  claim 1 , further comprising:
 an electrical resistance heating element configured to heat at least one of the one or more shape-memory elements; and   a battery electrically coupled to the electrical resistance heating element.   
     
     
         11 . The apparatus of  claim 1 , further comprising a mechanical fuse configured to restrain the first collar from movement relative to the second collar, the mechanical fuse comprising at least one shear member configured to fail in response to an application of a threshold amount of force applied by contraction of the one or more shape-memory elements. 
     
     
         12 . A method for expanding a radially-expandable member, comprising:
 positioning a first collar on a tubular adjacent to a first axial end of the radially-expandable member, wherein the tubular is configured to be deployed into a wellbore;   positioning a second collar on the tubular adjacent to a second axial end of the radially-expandable member, wherein the first and second axial ends are offset along a longitudinal axis of the tubular, wherein one or more shape memory elements are coupled with and extend between the first and second collars; and   raising a temperature of the one or more shape memory elements to at least a transition temperature, wherein the one or more shape memory elements are configured to contract when the temperature is greater than or equal to the transition temperature, wherein the one or more shape memory elements contracting forces the first and second collars toward one another such that the first and second collars bear on the first and second axial ends, respectively, of the radially-expandable member, causing the radially-expandable member to expand.   
     
     
         13 . The method of  claim 12 , wherein raising the temperature comprises energizing an electric heater thermally coupled to the one or more shape memory elements. 
     
     
         14 . The method of  claim 12 , wherein raising the temperature comprises running the one or more shape memory elements into the wellbore to a depth, wherein a temperature in the wellbore at the depth is at least as high as the transition temperature of the one or more shape memory elements. 
     
     
         15 . The method of  claim 12 , wherein the radially-expandable member comprises a packing element of a packer, wherein raising the temperature of the one or more shape memory elements causes the packing member to seal with the wellbore. 
     
     
         16 . The method of  claim 12 , wherein the radially expandable member comprises a rib of a centralizer, wherein raising the temperature of the one or more shape member elements causes the rib to expand radially outward to provide a standoff between the tubular and the wellbore. 
     
     
         17 . An apparatus for isolating a portion of a wellbore, comprising:
 a radially-expandable packing element disposed on a tubular and comprising a first annular axial end and a second annular axial end, the first and second annular axial ends being separated along a longitudinal axis of the radially-expandable packing element, the longitudinal axis extending generally parallel to the tubular, the first and second annular axial ends extending substantially perpendicular to the longitudinal axis;   a first collar disposed axially adjacent to the first annular axial end of the radially-expandable packing element;   a second collar disposed axially adjacent to the second annular axial end of the radially-expandable packing element; and   one or more shape memory elements coupled with and extending between the first and second collars, wherein the one or more shape memory elements are configured to contract when a temperature thereof reaches a transition temperature, wherein the one or more shape memory elements contracting causes the first and second collars to bear on the first and second annular axial ends, respectively, of the radially-expandable packing element so as compress the radially-expandable element along the longitudinal axis and radially expand the radially-expandable packing element.   
     
     
         18 . The apparatus of  claim 17 , wherein the one or more shape memory elements extend through the radially-expandable packing element. 
     
     
         19 . The apparatus of  claim 17 , further comprising a battery and an electric heater, the electric heater being thermally coupled to the one or more shape memory elements and electrically coupled with the battery. 
     
     
         20 . The apparatus of  claim 17 , wherein the first collar is fixed to the tubular and the second collar is slidable relative to the tubular.