Downwell system with differentially swellable packer

Abstract

A packer assembly comprises a tubular member and a packer system that circumferentially overlies the tubular member. The packer system includes end portions and a central portion disposed between the end portions. The central portion and the end portions are formed of material that swells when contacted with a swelling fluid. The central and end portions are constructed to swell upon contact with the swelling fluid so that the central portion swells to a diameter defined by a wall of the wellbore more rapidly than the end portions. In such a configuration, the central portion of the packer system can be fully swollen prior to the full swelling of the end portions.

1 . A packer assembly for a wellbore, comprising:
 a tubular member; and   a packer system that circumferentially overlies the tubular member, the packer system including end portions and a central portion disposed between the end portions;   wherein the central portion and the end portions are formed of material that swells when contacted with a swelling fluid; and   wherein the central and end portions are constructed to swell upon contact with the swelling fluid so that the central portion swells to a diameter defined by a wall of the wellbore more rapidly than the end portions.   
     
     
         2 . The packer assembly defined in  claim 1 , wherein the central portion is formed of a different material than the end portions. 
     
     
         3 . The packer assembly defined in  claim 2 , wherein the central portion includes separation caps located at axial ends of the central portion that encourage swelling of the central portion in a radial direction. 
     
     
         4 . The packer assembly defined in  claim 3 , wherein the separation caps include apertures located to permit swelling fluid to contact the axial ends of the central portion. 
     
     
         5 . The packer assembly defined in  claim 2 , wherein the central portion abuts a portion of the packer system formed of material that swells when contacted with a swelling fluid. 
     
     
         6 . The packer assembly defined in  claim 4 , wherein the central portion abuts an intermediate portion that is sandwiched between the central portion and one of the end portions. 
     
     
         7 . The packer assembly defined in  claim 2 , wherein the central portion comprises EPDM and a swelling agent. 
     
     
         8 . The packer assembly defined in  claim 6 , wherein the end portion comprises EPDM. 
     
     
         9 . The packer assembly defined in  claim 1 , wherein the central portion and the end portions are part of a unitary packer member. 
     
     
         10 . The packer assembly defined in  claim 8 , wherein the central portion has an outer diameter that is greater than an outer diameter of the end portions. 
     
     
         11 . The packer assembly defined in  claim 9 , wherein the unitary packer member is tapered from the central portion to the end portions. 
     
     
         12 . The packer assembly defined in  claim 8 , wherein the central portion and the end portions comprise the same material. 
     
     
         13 . A packer assembly for a wellbore, comprising:
 a tubular member; and   a packer system that circumferentially overlies the tubular member, the packer system including end portions and a central portion disposed between the end portions;   wherein the central portion and the end portions are formed of material that swells when contacted with a swelling fluid; and   wherein the central portion is formed of a first material, the end portions are formed of a second, different material, and the first material swells more rapidly in the swelling fluid than the second material.   
     
     
         14 . The packer assembly defined in  claim 13 , wherein the packer assembly is gapless between the central portion and the end portions. 
     
     
         15 . The packer assembly defined in  claim 13 , wherein at least one gap is present between the central portion and each end portion, and wherein a separation cap is mounted on axial ends of the central portion. 
     
     
         16 . The packer assembly defined in  claim 15 , wherein each of the separation caps includes apertures located to permit swelling fluid to contact the axial ends of the central portion. 
     
     
         17 . The packer assembly defined in  claim 13 , wherein the first material comprises EPDM and a swelling agent. 
     
     
         18 . The packer assembly defined in  claim 17 , wherein the second material comprises EPDM. 
     
     
         19 . A packer assembly for a wellbore, comprising:
 a tubular member; and   a packer system that circumferentially overlies the tubular member, the packer system including end portions and a central portion disposed between the end portions;   wherein the central portion and the end portions are formed of material that swells when contacted with a swelling fluid; and   wherein the central portion has a first diameter and the end portions have a second diameter that is less than the first diameter.   
     
     
         20 . The packer assembly defined in  claim 19 , wherein the central portion and the end portions are part of a unitary packer member. 
     
     
         21 . The packer assembly defined in  claim 20 , wherein the packer member is tapered from the central portion to the end portions. 
     
     
         22 . The packer assembly defined in  claim 19 , wherein the central portion and the end portions comprise the same material.