Centralized Wiper Plug

Abstract

A wiper plug has a elastomeric fin assembly straddled by centralizers that have the capacity to flex through restrictions while being strong enough to centralize and scrape a surrounding tubular wall. The centralizers reduce wear on the rib/fin assembly particularly on long horizontal runs. The centralizers can be a continuous spiral or a series of circumferentially offset spiral segments on a common hub. The spiral segments contain brushes extending from a base where the base and the mounting slot have a dovetail relationship for fixation to the wiper plug body. The plug body consist of three separate segments that are threaded together in order to trap the brush segments in the dovetail channels.

We claim: 
     
         1 . A wiper plug for downhole use, comprising:
 a mandrel;   a wiper fin between spaced centralizers on said mandrel.   
     
     
         2 . The wiper plug of  claim 1 , wherein:
 at least one of said centralizers further comprises a continuous helix extending for at least 360 degrees.   
     
     
         3 . The wiper plug of  claim 1 , wherein:
 at least one of said centralizers further comprises circumferentially spaced helical segments.   
     
     
         4 . The wiper plug of  claim 3 , wherein:
 adjacent said segments have axially overlapping or aligned opposed ends.   
     
     
         5 . The wiper plug of  claim 3 , wherein:
 an open helical passage is defined between adjacent segments.   
     
     
         6 . The wiper plug of  claim 1 , wherein:
 at least one of said centralizers comprises bristles.   
     
     
         7 . The wiper plug of  claim 1 , wherein:
 at least one of said centralizers comprises a continuous flexible material.   
     
     
         8 . The wiper plug of  claim 1 , wherein:
 at least one of said centralizers is mounted to said mandrel in a dovetailed groove.   
     
     
         9 . A wiper plug for downhole use, comprising:
 a mandrel;   a seal assembly and at least one centralizer on said mandrel, said centralizer comprising a continuous helix or spaced helical segments.   
     
     
         10 . The wiper plug of  claim 9 , wherein:
 adjacent said segments have axially overlapping or aligned opposed ends.   
     
     
         11 . The wiper plug of  claim 9 , wherein:
 said segments are secured in place on one end by shoulder of center mandrel.   
     
     
         12 . The wiper plug of  claim 9 , wherein:
 an open helical passage is defined between adjacent segments.   
     
     
         13 . The wiper plug of  claim 9 , wherein:
 said centralizer comprises bristles.   
     
     
         14 . The wiper plug of  claim 9 , wherein:
 said centralizer comprises a continuous flexible material.   
     
     
         15 . The wiper plug of  claim 9 , wherein:
 said centralizer is mounted to said mandrel in a dovetailed groove.