Energized Downhole Standoff

Abstract

Standoff devices and methods of their use are disclosed. In various embodiments, a standoff device includes a spring-loaded core rod whose longitudinal movement causes lateral extension members to extend outward to provide the desired standoff action. The core rod is initially restrained in its motion by a restraining part made of or including a fusible material. Melting of the fusible material causes release of the spring-loaded core rod and, as a result, outward extension of the lateral extension members. Further embodiments are described.

What is claimed is: 
     
         1 . A standoff device comprising:
 a spring-loaded core rod disposed along a longitudinal axis of the standoff device and configured to move longitudinally in a first direction upon release;   a restraining part formed at least in part from fusible material and restraining movement of the spring-loaded core rod, such that melting of the fusible material causes release of the spring-loaded core rod; and   one or more lateral extension members coupled to the core rod and configured to extend laterally outward upon longitudinal movement of the core rod in the first direction.   
     
     
         2 . The device of  claim 1 , wherein the one or more lateral extension members comprise one or more standoff arms hinged to the core rod, each standoff arm comprising a plurality of hinged links. 
     
     
         3 . The device of  claim 1 , wherein the one or more lateral extension members comprise an outer wedge engaging an inner wedge integrated with the core rod. 
     
     
         4 . The device of  claim 1 , further comprising an electric heating element adjacent the restraining part and a controller configured to supply current to the heating element. 
     
     
         5 . The device of  claim 4 , wherein the first restraining part comprises a plurality of sub-parts each having its own associated electric heating element. 
     
     
         6 . The device of  claim 1 , further comprising a return spring initially restrained in its motion by a second restraining part comprising a fusible material, melting of the fusible material of the second restraining part causing release of the return spring, the return spring upon release causing the core rod to move longitudinally in a second direction opposite the first direction. 
     
     
         7 . The device of  claim 6 , further comprising an electric heating element adjacent the second restraining part and a controller configured to supply current to the heating element. 
     
     
         8 . The device of  claim 6 , wherein the spring-loaded core rod comprises a head placed between an engaging spring and the restraining part, the tool further comprising a cage enclosing the engaging spring, the head, and the restraining part, the cage being placed between the return spring and the second restraining part. 
     
     
         9 . The device of  claim 1 , wherein the fusible material has a melting temperature corresponding to a specified downhole temperature. 
     
     
         10 . The device of  claim 1 , defining a central hollow core along the longitudinal tool axis. 
     
     
         11 . The device of  claim 1 , further comprising a housing including, at its ends, joints for integrating the standoff device into a tool string. 
     
     
         12 . The device of  claim 1 , further comprising one or more positional sensors for determining an operational state of the device. 
     
     
         13 . A method of using a standoff device, the method comprising:
 disposing the standoff device in a borehole; and   causing a fusible material associated with a restraining part of the standoff device to melt so as to release a spring-loaded core rod, thereby causing one or more lateral extension members to extend laterally from the standoff device into contact with a wall of the borehole.   
     
     
         14 . The method of  claim 13 , wherein causing the fusible material to melt comprises causing an electrical current to be applied to an electric heating element adjacent the fusible material. 
     
     
         15 . The method of  claim 14 , further comprising transmitting a control signal downhole to the standoff device, the electric current being applied in response to the control signal. 
     
     
         16 . The method of  claim 13 , further comprising causing a fusible material associated with a second restraining part initially restraining motion of a return spring to melt so as to release the return spring, release of the return spring causing the core rod to move so as to retract the one or more lateral extension members. 
     
     
         17 . The method of  claim 16 , further comprising retrieving the standoff device from the borehole following retraction of the one or more lateral extension members. 
     
     
         18 . The method of  claim 13 , wherein the fusible material is caused to melt prior to disposing the standoff device in the borehole. 
     
     
         19 . The method of  claim 13 , wherein causing the fusible material to melt comprises lowering the standoff device to a depth at which a borehole temperature exceeds a melting temperature of the fusible material. 
     
     
         20 . The method of  claim 13 , wherein the fusible material is caused to melt when the device is located in a horizontal borehole section, extension of the one or more lateral extension members causing lifting of the standoff device off a borehole wall. 
     
     
         21 . The method of  claim 13 , wherein the standoff device is placed in-line with a tool string.