Wellhead isolation mandrel with centralizing device

Abstract

A wellhead isolation tool including a mandrel and a centralizing device. The centralizing device will align the tool so that the lower end of the mandrel sealingly engages the production casing. The mandrel has an open bore for allowing service tools to pass therethrough.

1 . A self-aligning wellhead isolation tool comprising:
 a tubular mandrel having first and second ends;   a centralizing device mounted to and extending radially outwardly from the mandrel adapted to engage the wellhead along at least a portion of the interior thereof to align the isolation tool; and   a sealing system operably associated with the mandrel, the sealing system operable to seal against the casing bore of a top casing joint in the wellhead to protect the wellhead during treatment of a well.   
   
   
       2 . The wellhead isolation tool of  claim 1  wherein the sealing system is mounted on the mandrel, and the mandrel and sealing system are insertable into the top casing to seal against the casing bore. 
   
   
       3 . The wellhead isolation tool of  claim 2 , the sealing system comprising a generally circular seal disposed about the mandrel. 
   
   
       4 . The wellhead isolation tool of  claim 2 , the sealing system comprising a plurality of seals disposed about the mandrel, each seal having an outer diameter, wherein the outer diameter of the seals increases from the lower end toward the upper end of the mandrel. 
   
   
       5 . The wellhead isolation tool of  claim 4 , wherein the sealing system comprises three longitudinally spaced seals disposed about the mandrel. 
   
   
       6 . The wellhead isolation tool of  claim 1 , wherein the centralizing device comprises:
 a plurality of bow springs; and   first and second collars slidably disposed about the mandrel, the bow springs being attached at first and second ends thereof to the first and second collars.   
   
   
       7 . The wellhead isolation tool of  claim 6 , wherein one of the first and second collars comprises a collet. 
   
   
       8 . The wellhead isolation tool of  claim 7 , the sealing system comprising at least one seal disposed about the mandrel, the at least one seal having an outer diameter sized to sealingly engage the casing bore of the top casing joint. 
   
   
       9 . The wellhead isolation tool of  claim 1 , the mandrel defining a mandrel bore capable of receiving service tools therethrough for conducting downhole service operations in the well. 
   
   
       10 . The wellhead isolation tool of  claim 1 , further comprising a perforating device positioned in the well, wherein the perforating device is lowered through the mandrel and suspended in the well. 
   
   
       11 . A wellhead isolation tool, comprising:
 a mandrel defining a flow passage for treatment fluids, the mandrel being insertable into a top casing bore in the wellhead; and   a sealing system mounted on the mandrel for sealing against the top casing bore, wherein the sealing system has a progressively larger diameter in a direction from a lower end of the mandrel upwardly toward the upper end of the mandrel.   
   
   
       12 . The wellhead isolation tool of  claim 11 , the flow passage being defined by a mandrel bore, wherein the mandrel bore is adapted to receive service tools therethrough. 
   
   
       13 . The wellhead isolation tool of  claim 11 , the sealing system comprising a plurality of seals mounted on the mandrel, the seals having progressively increasing outer diameters from a lowermost seal upwardly to an uppermost seal. 
   
   
       14 . The wellhead isolation tool of  claim 11  further comprising a centralizing device for centralizing the sealing system prior to insertion into the casing bore. 
   
   
       15 . The wellhead isolation tool of  claim 14 , the aligning device comprising a plurality of bow springs disposed about the mandrel. 
   
   
       16 . The wellhead isolation tool of  claim 15 , further comprising first and second collars slidably disposed about the mandrel, the bow springs being attached at first and second ends thereof to the first and second collars. 
   
   
       17 . The wellhead isolation tool of  claim 11 , wherein the mandrel defines a mandrel bore having a diameter large enough to accommodate the passage of service tools therethrough, so that well treatment services may be performed without removing the wellhead isolation tool from the wellhead. 
   
   
       18 . The wellhead isolation tool of  claim 17 , wherein the mandrel bore will accommodate the passage of a tool selected from the group consisting of bridge plugs, packers and perforating devices. 
   
   
       19 . A method of conducting multi-stage operations in a well comprising:
 deploying a wellhead isolation tool in a wellhead;   sealingly inserting a lower end of the wellhead isolation tool into a casing bore of a casing in the wellhead;   pumping a treating fluid through the wellhead isolation tool into the well and into a selected zone intersecting the well;   lowering a service tool through the wellhead isolation tool;   performing a selected service with the service tool; and   retrieving the service tool through the wellhead isolation tool.   
   
   
       20 . The method of  claim 19 , the treating fluid comprising a fracturing fluid. 
   
   
       21 . The method of  claim 19 , the service tool comprising a perforating device, the performing step comprising perforating casing in the well at an additional selected zone. 
   
   
       22 . The method of  claim 21 , comprising sequentially repeating the pumping, lowering, performing and retrieving steps for a desired number of selected zones. 
   
   
       23 . The method of  claim 19  wherein the service tool comprises at least a perforating device and a well sealing device, the performing step comprising sealing the well below the perforating device, and perforating the well at an additional selected zone. 
   
   
       24 . The method of  claim 23  further comprising pumping a treating fluid into the additional selected zone after the perforating step, and repeating the sealing and perforating step in the well at additional selected zones. 
   
   
       25 . The method of  claim 19  comprising aligning the lower end of the isolation tool with the casing bore prior to the inserting step. 
   
   
       26 . The method of  claim 25 , the wellhead isolation tool comprising a centralizing device for centralizing the wellhead isolation tool and aligning the lower end of the wellhead isolation tool with the casing bore. 
   
   
       27 . A method of preparing a well for production comprising:
 sealingly inserting a wellhead isolation tool through a wellhead at the well into a top casing bore;   pumping a treating fluid through the wellhead isolation tool into a selected zone intersecting the well;   lowering a tool string including at least a well plug through the wellhead isolation tool into the well;   setting the well plug in the well above the selected zone; and   perforating the casing adjacent an additional selected zone above the plug in the well without removing the wellhead isolation tool.   
   
   
       28 . The method of  claim 27 , wherein the lowering step comprises lowering a perforating device through the wellhead into the wellbore along with the well plug on a single tool string. 
   
   
       29 . The method of  claim 27  further comprising:
 pumping a treating fluid through the wellhead isolation tool into the well and through the perforations adjacent the additional selected zone to treat the additional selected zone;   lowering a tool string through the wellhead isolation tool, the tool string including at least a well plug; and   setting the well plug in the well above the additional selected zone.   
   
   
       30 . The method of  claim 27  further comprising sequentially repeating the pumping, lowering, setting and perforating steps upwardly in the well for a desired number of additional selected zones. 
   
   
       31 . The method of  claim 30 , further comprising aligning the wellhead isolation tool in the wellhead to align a mandrel of the wellhead isolation tool with the top casing bore prior to the inserting step. 
   
   
       32 . The method of  claim 30 , wherein the treating fluid comprises a fracturing fluid. 
   
   
       33 . The method of  claim 27 , wherein the treating fluid comprises a fracturing fluid. 
   
   
       34 . The method of  claim 27 , further comprising aligning the wellhead isolation tool in the wellhead to align a mandrel of the wellhead isolation tool with the top casing bore prior to the inserting step. 
   
   
       35 . The method of  claim 34 , comprising using a centralizing device mounted on the wellhead isolation tool to perform the aligning step. 
   
   
       36 . The method of  claim 27 , comprising using a centralizing device mounted on the wellhead isolation tool to perform the aligning step.