Shock resistant circulation sub

Abstract

A circulation sub and method of operating a circulation sub. The circulation sub includes a support member having a longitudinal axis and a piston movable along the longitudinal axis of the support member. A release member secures the piston to the support member. A force is applied along a length axis of the release member greater than a selected decoupling force threshold to decouple the support member from the piston, thereby allowing the piston to move along the longitudinal axis of the member.

What is claimed is: 
     
         1 . A circulation sub, comprising:
 a support member having a longitudinal axis;   a piston movable along the longitudinal axis of the support member; and   a release member configured to secure the piston to the support member and to release the piston from the support member when a force applied along a length axis of the release member is greater than a decoupling force threshold of the release member.   
     
     
         2 . The circulation sub of  claim 1 , wherein the decoupling force threshold of the release member is greater than the force applied along the length axis of the release member by one or more vibrators used to move the circulation sub in a wellbore. 
     
     
         3 . The circulation sub of  claim 1 , wherein the length axis of the release member is parallel to the longitudinal axis of the support member. 
     
     
         4 . The circulation sub of  claim 1 , wherein the release member is configured to break when a pressure differential between an inner bore of the circulation sub and a wellbore annulus applies the force on the release member greater than the decoupling force threshold. 
     
     
         5 . The circulation sub of  claim 1 , wherein the piston includes a ball seat for receiving a ball, wherein a fluid pressure applied to the received ball applies the force of the release member. 
     
     
         6 . The circulation sub of  claim 1 , wherein the release member further comprises a tensile stud, the tensile stud having a first end securable to the support member, a second end securable to the piston and a stud break section that defines the decoupling force threshold. 
     
     
         7 . The circulation sub of  claim 6 , wherein the stud break section has a diameter smaller than a diameter of a first stud end and a diameter of a second stud end. 
     
     
         8 . The circulation sub of  claim 1 , wherein the release member further comprises a ring having a first ring end secured to the support member and a second ring end secured to the piston, the ring includes a ring break section between the first ring end and the second ring end that defines the decoupling force threshold. 
     
     
         9 . The circulation sub of  claim 8 , wherein the ring break section includes one or more holes for reducing a strength of the ring break section with respect to the strength of the first ring end and the second ring end. 
     
     
         10 . The circulation sub of  claim 1 , wherein the release member secures the piston to the support member at a location radially offset from a longitudinal axis of the circulation sub. 
     
     
         11 . A method of operating a circulation sub, comprising:
 coupling a support member of the circulation sub and a piston using a release member; and   applying a force along a length axis of the release member greater than a selected decoupling force threshold to decoupling the support member from the piston, thereby allowing the piston to move along the longitudinal axis of the member.   
     
     
         12 . The method of  claim 11 , wherein the decoupling force threshold of the release member is greater than a force applied along the longitudinal axis of the circulation sub by one or more vibrators used to move the circulation sub in a wellbore. 
     
     
         13 . The method of  claim 11 , further comprising applying a pressure differential between an inner bore of the circulation sub and an annulus to apply the force on the release member greater than the selected decoupling force threshold. 
     
     
         14 . The method of  claim 11 , further comprising receiving a ball at the piston and applying the force along the length axis of the release member via a hydraulic pressure on the ball. 
     
     
         15 . The method of  claim 11 , wherein the release member further comprises a tensile stud, and the length axis of the tensile stud is parallel to the longitudinal axis of the support member. 
     
     
         16 . The method of  claim 15 , wherein the tensile stud includes a stud break section defining the decoupling force threshold, the stud break section having a diameter smaller than a diameter of a first stud end and a diameter of a second stud end. 
     
     
         17 . The method of  claim 11 , wherein the release member further comprises a ring having a first ring end secured to the support member and a second ring end secured to the piston, the ring includes a ring break section defining the decoupling force threshold. 
     
     
         18 . The method of  claim 17 , wherein the ring break section includes one or more holes for weakening the ring break section with respect to at least one of the first ring end and the second ring end.