Wellbore tractor with fluid conduit sheath

Abstract

A fluid conduit sheath for a wellbore tractor can provide transportation of a working fluid external to a wellbore tractor in a downhole environment. The fluid conduit sheath can further provide cooling to electrical devices in the wellbore tractor. The fluid conduit sheath can be configured to be disposed around the body of the wellbore tractor, defining a fluid conduit between the sheath and the wellbore tractor. Spacers can be used to maintain the position of the sheath relative to the tractor and also to couple the tractor to the sheath. The fluid conduit sheath can be advantageous in tractors whose internal components substantially preclude the use of an internal fluid conduit, such as tractors with electrically-actuated grippers.

1 . A tool for moving within a passage, comprising:
 an elongate body having an outer surface;   at least one gripper assembly engaged with the body, the gripper assembly having an actuated position in which the gripper assembly grips onto an inner surface of the passage to substantially limit relative movement between the gripper assembly and the inner surface, the gripper assembly having a retracted position in which the gripper assembly permits substantially free relative movement between the gripper assembly and the inner surface of the passage;   an actuator configured to move the gripper between the actuated position and the retracted position; and   a fluid conduit sheath disposed around at least a portion of the elongate body and having an inner surface such that the fluid conduit sheath defines a fluid conduit between the outer surface of the elongate body and the inner surface of the fluid conduit sheath.   
   
   
       2 . The tool of  claim 1 , wherein the elongate body has a circumference and the fluid conduit sheath comprises:
 a first segment defined by a substantially cylindrical profile disposed around substantially the entire circumference of the elongate body; and   a second segment configured to allow passage of the gripper assembly therethrough when the gripper assembly is in the actuated position.   
   
   
       3 . The tool of  claim 1 , further comprising a spacer separating the outer surface of the elongate body and the inner surface of the fluid conduit sheath. 
   
   
       4 . The tool of  claim 1 , further comprising a plurality of spacers separating the outer surface of the elongate body and the inner surface of the fluid conduit sheath. 
   
   
       5 . The tool of  claim 1 , wherein the actuator comprises a motor configured to be powered by electricity. 
   
   
       6 . The tool of  claim 5 , wherein the fluid conduit sheath is configured to direct fluid near the motor to cool the motor. 
   
   
       7 . The tool of  claim 1 , further comprising coiled tubing. 
   
   
       8 . A sheath for use with a tool for moving within a passage, the sheath comprising:
 a sheath body having an inner surface, the sheath body configured to be disposed around the tool such that the sheath body defines a fluid conduit between an outer surface of the tool and the inner surface of the sheath body; and   at least one spacer configured to separate the tool and the sheath body to maintain the position of the tool with respect to the sheath body.   
   
   
       9 . The sheath of  claim 8 , wherein the tool comprises an elongate body and a gripper assembly, the gripper assembly having an actuated position in which the gripper assembly grips onto an inner surface of the passage to substantially limit relative movement between the gripper assembly and the inner surface, the gripper assembly having a retracted position in which the gripper assembly permits substantially free relative movement between the gripper assembly and the inner surface of the passage; and
 wherein the sheath body comprises:
 a first portion configured to be disposed around the elongate body; and 
 a second portion configured to allow passage of the gripper assembly therethrough when the gripper assembly is in the actuated position. 
   
   
   
       10 . The sheath of  claim 9 , wherein the gripper assembly comprises three gripper arms and wherein the second portion of the sheath body comprises three apertures, the apertures sealed with respect to the tool such that fluid is retained in the fluid conduit, and each of the apertures configured to permit passage of a corresponding gripper arm therethrough when the gripper assembly is in the actuated position. 
   
   
       11 . The sheath of  claim 9 , wherein the sheath is comprised of a material selected to withstand elevated temperatures in the passage. 
   
   
       12 . A method of transporting fluid downhole in a tool for moving within a passage, the method comprising:
 providing a tool for moving within a passage, the tool comprising:
 an elongate body having an outer surface; 
 at least one gripper assembly engaged with the body, the gripper assembly having an actuated position in which the gripper assembly grips onto an inner surface of the passage to substantially limit relative movement between the gripper assembly and the inner surface, the gripper assembly having a retracted position in which the gripper assembly permits substantially free relative movement between the gripper assembly and the inner surface of the passage; 
 a fluid conduit sheath disposed around at least a portion of the elongate body and having an inner surface such that the fluid conduit sheath defines a fluid conduit between the outer surface of the elongate body and the inner surface of the fluid conduit sheath and; 
 transporting fluid through the fluid conduit external to the elongate body. 
   
   
   
       13 . The method of  claim 12 , wherein the tool further comprises an electrical component and wherein the fluid conduit sheath is configured to direct fluid near the electrical component to cool the electrical component. 
   
   
       14 . The method of  claim 13 , wherein the electrical component comprises an electric motor configured to cause the gripper assembly to move between its actuated position and its retracted position.