Wellhead Sealing System and Method

Abstract

A system for sealing a wellhead. The system includes a setting frame, a driver cylinder selectively applying an axial motion, an adaptor attached to the wellhead, and a power mandrel operatively attached to the driver cylinder. The system may also include a setting sleeve attached to the power mandrel, with the setting sleeve having a packer element, wherein the setting sleeve is responsive to a pressure applicator and retractor device so that the packer element is expanded within the master valve. A method of isolating a wellbore is also disclosed.

I claim: 
     
         1 . An apparatus for sealing a surface wellhead, wherein said wellhead contains a master valve, the apparatus comprising:
 a driver cylinder for selectively applying an axial motion;   an adaptor, operatively attached to the wellhead, said adaptor having an inner bore in communication with an inner portion of the wellhead;   a setting frame operatively attached to said adaptor;   a packing stack member operatively attached to said adaptor, said packing stack member having a seal unit;   a power mandrel operatively attached to said driver cylinder;   a setting sleeve operatively attached with said power mandrel, said setting sleeve having a packer element and wherein said setting sleeve is adapted to sealingly engage said seal unit,   pressure applicator and retractor means, operatively attached to said power mandrel, for transferring an applied rotational force to said setting sleeve so that said packer element is expanded within an inner bore of the master valve.   
     
     
         2 . The apparatus of  claim 1  wherein the wellhead further contains a tubing hanger that has a tubing string hanging therefrom, the apparatus further comprising:
 internal engaging means, operatively attached to said power mandrel, for selectively engaging the inner bore of the wellhead. 
 
     
     
         3 . The apparatus of  claim 2  wherein the internal engaging means comprising:
 a distal mandrel attached to said power mandrel; 
 a protrusion rotatably attached to said distal mandrel, said protrusion having a radial position and an axial position, wherein in the radial position, said protrusion engages an inner portion of the tubing hanger. 
 
     
     
         4 . The apparatus of  claim 2  wherein said internal engaging means comprises a grapple-spear assembly for anchoring into the internal portion of the master valve. 
     
     
         5 . The apparatus of  claim 2  wherein said pressure applicator and retractor means comprises:
 an external thread means located on said power mandrel; 
 a nut member disposed about said setting sleeve, said nut member having an internal thread means operatively associated with the external thread means on said power mandrel; 
 a shell member engaging said nut member; 
 a set screw for attaching said shell member to said setting sleeve; 
 and wherein rotation of said nut member moves said setting sleeve relative to said power mandrel. 
 
     
     
         6 . A method of isolating a wellbore having a master valve, the method comprising:
 closing the master valve so that the wellbore is isolated;   attaching a master valve adaptor to the wellhead;   installing a packer assembly to the master valve adaptor, wherein said packer assembly comprises: a setting frame; a setting sleeve operatively associated with a power mandrel, said setting sleeve having a packer element; a pressure applicator and retractor device, threadedly connected to said power mandrel, for providing a rotational force transferred to said setting sleeve, wherein said setting sleeve being responsive to the transferred rotational force so that said packer element is expanded within an inner bore of the master valve;   forming a seal with said setting sleeve engaging a packing stack on said master valve adaptor;   opening the master valve;   retaining a pressure from the wellbore at the packing stack;   placing a downward force on said power mandrel so that said power mandrel and said setting sleeve are pushed down into the wellhead;   applying a rotational force with said pressure applicator and retractor device and transferring the rotational force to said setting sleeve so that said setting sleeve is moved downward and said packer element is compressed and expanded within an inner bore of said master valve.   
     
     
         7 . The method of  claim 6  further comprising:
 opening a vent valve in said adaptor; 
 testing whether said packer element is sealing pressure. 
 
     
     
         8 . The method of  claim 7  further comprising:
 removing the setting frame from the packer assembly. 
 
     
     
         9 . The method of  claim 8  further comprising:
 removing said master valve adaptor from the wellhead. 
 
     
     
         10 . The method of  claim 9  further comprising:
 observing a rise in the pressure from the wellhead; 
 reattaching the master valve adaptor to the wellhead. 
 
     
     
         11 . The method of  claim 6  wherein the packer assembly further comprises internal engaging means, operatively attached to said power mandrel, for selectively engaging the internal portion of the master valve, and the method further comprises:
 mounting a driver cylinder to said packer assembly; 
 attaching the driver cylinder to said power mandrel; 
 creating an upward force so that a set of shear dogs engage a tubing hanger; 
 shearing said shear dogs; 
 pulling said power mandrel and said setting sleeve from said master valve. 
 
     
     
         12 . The method of  claim 6  wherein the packer assembly further comprises a grapple-spear assembly, operatively attached to said power mandrel, for selectively anchoring to the internal portion of the master valve, and the method further comprises:
 mounting a driver cylinder to said packer assembly; 
 attaching the driver cylinder to said power mandrel; 
 rotating the power mandrel in order to set the grapple-spear assembly; 
 pulling up on the power mandrel in order to cause the grapple-spear assembly to anchor said packer assembly in the internal portion of the master valve. 
 
     
     
         13 . A system for sealing a wellhead, said wellhead containing a tubing hanger therein, the system comprising:
 an adaptor, operatively attached to said wellhead, said adaptor having an inner bore in communication with an inner portion of the wellhead;   a driver cylinder for selectively applying an axial motion, said driver cylinder being operatively associated with said adaptor;   a power mandrel operatively attached to said driver cylinder;   a setting sleeve operatively attached with said power mandrel, said setting sleeve having a packer element, and wherein said setting sleeve is adapted to sealingly engage said seal unit;   pressure applicator and retractor means, operatively attached to said power mandrel, for transferring an applied rotational force to said setting sleeve, wherein said setting sleeve being responsive to the rotation force so that said packer element is expanded within an inner bore of the master valve;   internal engaging means, operatively attached to said power mandrel, for selectively engaging an internal portion of the wellhead.   
     
     
         14 . The apparatus of  claim 13  wherein the internal engaging means comprising:
 a distal mandrel attached to said packer mandrel; 
 a protrusion pivotly attached to said distal mandrel, said protrusion having a radial position and an axial position, wherein in the radial position, said protrusion engages an inner portion of said tubing hanger. 
 
     
     
         15 . The apparatus of  claim 14  further comprising:
 a shear member operatively attached to said packer mandrel for shearing the packer mandrel from said distal mandrel. 
 
     
     
         16 . The apparatus of  claim 13  wherein the internal engaging means comprise:
 a grapple having an outer profile and an inner profile; 
 a spear having an outer spiral, said outer spiral of said spear operatively engaged with the inner profile of the grapple in order to selectively engage and disengage the grapple with the internal portion of the wellhead. 
 
     
     
         17 . A method of isolating a wellbore having a master valve, the master valve having an inner portion in communication with the wellbore, the method comprising:
 closing the master valve so that the wellbore is isolated;   attaching an adaptor to the master valve;   installing a packer assembly to the adaptor, said packer assembly containing a setting sleeve and a power mandrel;   forming a seal by engaging a packing stack member within said adaptor with said setting sleeve;   opening the master valve;   retaining a pressure from the wellbore at the packing stack member;   placing a downward force on said power mandrel and said setting sleeve of said packer assembly so that the power mandrel is pushed down into the wellhead;   applying a rotational force to a pressure applicator and retractor device and transferring the rotational force to said setting sleeve and creating a downward force on a packer element on said packer assembly thereby compressing and expanding the packer element in the inner portion of the master valve   setting a grapple-spear assembly in the inner portion of the master valve.   
     
     
         18 . The method of  claim 17  further comprising:
 opening a vent valve in said adapter; 
 testing whether said packer element is sealing pressure. 
 
     
     
         19 . The method of  claim 18  further comprising:
 removing said adaptor from the wellhead. 
 
     
     
         20 . The method of  claim 17  further comprising:
 observing a rise in the pressure from the wellhead; 
 reattaching the adaptor to the master valve. 
 
     
     
         21 . The method of  claim 17  wherein the grapple-spear assembly includes an inner spear mandrel operatively associated with an outer grapple member.