Improved seal

Abstract

A seal arrangement includes a plurality of seal elements arranged in series. At least one seal element has a predetermined rated pressure and includes a relief arrangement permitting relief of pressure across the seal element at a predetermined level lower than said rated pressure.

1 . A downhole seal arrangement comprising a plurality of seal elements arranged in series, wherein at least one seal element has a predetermined rated pressure and comprises a relief arrangement contained therein for permitting relief of pressure across the seal element at a predetermined level lower than said rated pressure. 
     
     
         2 . The seal arrangement of  claim 1 , wherein the relief arrangement is adapted to permit relief of pressure across the seal element without affecting the integrity of the seal element. 
     
     
         3 . The seal arrangement of  claim 1 , wherein the seal arrangement is configured whereby pressure bleeding across the at least one seal element is at least in part held by an adjacent seal element. 
     
     
         4 . The seal arrangement of  claim 1 , wherein two or more seal elements of the seal arrangement include respective pressure relief arrangements. 
     
     
         5 . The seal arrangement of  claim 1 , wherein all of the seal elements include pressure relief arrangements. 
     
     
         6 . (canceled) 
     
     
         7 . The seal arrangement of  claim 1 , wherein at least one of the seal elements includes a swellable material. 
     
     
         8 . The seal arrangement of  claim 1 , wherein at least one of the seal elements includes a swellable elastomer. 
     
     
         9 . The seal arrangement of  claim 1 , wherein the seal arrangement comprises a base pipe providing mounting for a series of annular seal elements. 
     
     
         10 . The seal arrangement of  claim 8 , wherein the seal elements are axially spaced. 
     
     
         11 . The seal arrangement of  claim 1 , wherein activation of the seal elements results in the radial extension or expansion of the seal elements. 
     
     
         12 . The seal arrangement of  claim 1 , wherein the relief arrangement includes at least one valve. 
     
     
         13 . The seal arrangement of  claim 11 , wherein the at least one valve is adapted to permit a controlled flow or bleed of fluid when exposed to a predetermined pressure differential. 
     
     
         14 . The seal arrangement of  claim 11 , wherein the at least one valve is mounted within a seal element comprising a swellable material. 
     
     
         15 . The seal arrangement of  claim 1 , wherein the relief arrangement is provided by selecting an appropriate configuration or material for a portion of the seal element. 
     
     
         16 . The seal arrangement of  claim 14 , wherein at least one seal element includes a relatively hard surface-defining portion adapted to permit low flow rate fluid passage between the seal element and an opposing surface at a pressure differential lower than the normal rated pressure of the element. 
     
     
         17 . The seal arrangement of  claim 1 , wherein the relief arrangement is adapted to permit relief only in a single direction across the seal arrangement. 
     
     
         18 . The seal arrangement of  claim 1 , wherein the relief arrangement is adapted to permit relief in two opposite directions across the seal arrangement 
     
     
         19 . A downhole seal method comprising:
 providing a series of seal elements, wherein at least one seal element comprises a relief arrangement contained therein;   locating the seal elements downhole; and   permitting relief of pressure across the at least one seal element through the relief arrangement at a pressure differential below a predetermined rated pressure of the at least one seal element.   
     
     
         20 . The method of  claim 19 , comprising permitting relief of pressure across a plurality of the seal elements at a pressure differential below the rated pressure of the respective seal elements. 
     
     
         21 . The method of  claim 20 , comprising permitting equalization of pressure differential across multiple individual seal elements. 
     
     
         22 - 23 . (canceled) 
     
     
         24 . The method of  claim 18 , comprising locating the seal arrangement downhole. 
     
     
         25 . The method of  claim 18 , comprising providing at least one seal element including a swellable material and exposing the seal element to a suitable activator. 
     
     
         26 . The method of  claim 18 , wherein relief of pressure across the seal element occurs without affecting the integrity of the seal element. 
     
     
         27 . A downhole seal arrangement comprising:
 a base pipe; and   a plurality of seal elements arranged in series along the base pipe and configured to be activated to radially expand to engage and seal a surrounding bore wall, wherein at least one seal element has a predetermined rated pressure and comprises a relief arrangement contained therein for permitting relief of pressure across the seal element at a predetermined level lower than said rated pressure.   
     
     
         28 . A seal arrangement comprising a plurality of seal elements arranged in series, at least one seal element having a predetermined rated pressure and including a relief arrangement permitting relief of pressure across the seal element at a predetermined level lower than said rated pressure, wherein the relief arrangement includes at least one valve mounted within a seal element comprising a swellable material. 
     
     
         29 . A seal arrangement comprising a plurality of seal elements arranged in series, at least one seal element having a predetermined rated pressure and including a relief arrangement permitting relief of pressure across the seal element at a predetermined level lower than said rated pressure, wherein at least one seal element includes a relatively hard surface-defining portion adapted to permit low flow rate fluid passage between the seal element and an opposing surface at a pressure differential lower than the normal rated pressure of the element.