Inflatable packer assembly

Abstract

Conventional formation evaluation with dual inflatable packers includes the steps of pressurizing the packers so as to isolate an annular portion of the borehole wall, collecting one or more samples of formation fluid via the isolated portion of the borehole wall, and depressurizing the packers so as to permit movement of the mandrel within the borehole. A sampling method and apparatus that utilize one or more of the following to advantage is provided: restricting deformation of the packers during inflation using an annular bracing assembly; actively retracting the packers using ambient borehole pressure; and substantially centralizing the mandrel intermediate the packers so as to resist buckling of the mandrel.

1 . An inflatable packer assembly, comprising:
 an expandable tubular element;   a pair of annular end supports for securing respective ends of the tubular element about a mandrel disposed within the tubular element, wherein at least one of the end supports is axially movable along the mandrel; and   a retractor configured to urge the at least one movable end support axially away from the other end support.   
   
   
       2 . The inflatable packer assembly of  claim 1  wherein the retractor is configured to apply a force on the at least one movable end support in a direction that is substantially parallel to an axis of the mandrel. 
   
   
       3 . The inflatable packer assembly of  claim 1  wherein one of the end supports is fixed with respect to the mandrel. 
   
   
       4 . The inflatable packer assembly of  claim 1  wherein the at least one movable end support is a lower end support. 
   
   
       5 . The inflatable packer assembly of  claim 1  wherein the at least one movable end support comprises a first surface in fluid communication with an interior of the expandable tubular element and a second surface in fluid communication with the wellbore, the first surface area exceeding the second surface area. 
   
   
       6 . The inflatable packer assembly of  claim 1  wherein the retractor comprises a stop member limiting axial movement of the at least one movable end support. 
   
   
       7 . The inflatable packer assembly of  claim 1  wherein the retractor comprises a pressure chamber having a lower pressure than a wellbore pressure. 
   
   
       8 . The inflatable packer assembly of  claim 7  wherein the pressure chamber is defined by a plurality of seals disposed on the at least one movable end support. 
   
   
       9 . The inflatable packer assembly of  claim 1  wherein the retractor is configured to urge the tubular element towards a deflated position. 
   
   
       10 . The inflatable packer assembly of  claim 1  wherein the expandable tubular element is a first expandable tubular element, the annular end supports are first annular end supports, the retractor is a first retractor, and the inflatable packer assembly further comprises:
 a second expandable tubular element;   a pair of second annular end supports for securing respective ends of the second tubular element about the mandrel, wherein at least one of the second end supports is axially movable along the mandrel; and   a second retractor configured to urge the at least one movable second end support axially away from the other second end support.   
   
   
       11 . The inflatable packer assembly of  claim 10  wherein one of the second end supports is fixed with respect to the mandrel. 
   
   
       12 . The inflatable packer assembly of  claim 10  wherein the at least one movable second end support is a lower second end support. 
   
   
       13 . The inflatable packer assembly of  claim 10  wherein the second retractor is configured to urge the second tubular element towards a deflated position. 
   
   
       14 . A method for using an inflatable packer assembly, comprising:
 inflating an expandable tubular element of the inflatable packer assembly in a bore, the inflatable packer assembly comprising:
 a pair of annular end supports securing respective ends of the tubular element about a mandrel disposed within the tubular element, wherein at least one of the end supports is axially movable along the mandrel; and 
 a retractor configured to urge the at least one movable end support axially away from the other end support; and 
   deflating the expandable tubular element by allowing the retractor to urge the at least one movable end support axially away from the other end support.   
   
   
       15 . The method of  claim 14  wherein the bore is a wellbore penetrating a subterranean formation. 
   
   
       16 . The method of  claim 15  wherein allowing the retractor to urge the at least one movable end support axially away from the other end support comprises actively retracting the expandable tubular using a wellbore pressure applied to the movable end supports. 
   
   
       17 . The method of  claim 16  wherein using a wellbore pressure applied to the movable end supports comprises exposing a first surface and a second surface of the at least one movable end to the wellbore pressure, the first surface area exceeding the second surface area. 
   
   
       18 . The method of  claim 15  wherein allowing the retractor to urge the at least one movable end support axially away from the other end support comprises exposing a surface of the at least one movable end support to a pressure lower than a wellbore pressure. 
   
   
       19 . The method of  claim 14  wherein one of the end supports is fixed with respect to the mandrel. 
   
   
       20 . The method of  claim 14  wherein axial movement of the at least one movable end support is limited by a stop.