Method and apparatus for catching darts and other dropped objects

Abstract

A dart or other dropped object having a rigid nose is dropped or launched down hole, typically during cementing operations, until it lands on a resilient seat within a dart catcher receptacle. By increasing a pressure differential across the landed dart to a predetermined amount, the dart extrudes through the seat and passes into a ported catcher sub. The seat member can be constructed of engineered composite material that does not yield in response to passage of the dart and returns to its original size following such passage.

What is claimed: 
     
         1 . A dart catcher apparatus comprising:
 a) a dart having a rigid nose defining an outer diameter; and   b) a housing having a central through bore, wherein a portion of said through bore has a reduced internal diameter defining a seat having an inner diameter smaller than said outer diameter of said nose, and wherein said seat comprises resilient material adapted to expand to allow passage of said rigid dart nose in response to a predetermined axial force acting on said dart.   
     
     
         2 . The dart catcher assembly of  claim 1 , wherein said seat is at least partially constructed of composite material. 
     
     
         3 . The dart catcher assembly of  claim 1 , wherein said seat does not permanently yield during passage of said dart. 
     
     
         4 . The dart catcher assembly of  claim 1 , wherein said seat returns to substantially its original size following passage of said dart. 
     
     
         5 . The dart catcher assembly of  claim 1 , further comprising a receptacle disposed below said seat adapted to receive a dart passing through said seat. 
     
     
         6 . The dart catcher assembly of  claim 5 , wherein said receptacle comprises a substantially cylindrical housing defining an inner chamber and at least one flow port extending from said inner chamber through said housing. 
     
     
         7 . The dart catcher assembly of  claim 6 , wherein said at least one flow port comprises an elongate aperture. 
     
     
         8 . A method for catching dropped objects in a well comprising:
 a) introducing a dart having a rigid nose defining an outer diameter into said well;   b) receiving said dart on a seat in a dart catcher assembly, wherein said dart catcher assembly comprises a housing having a central through bore defining said seat, and wherein said seat has an inner diameter smaller than said outer diameter of said dart nose and is at least partially constructed of resilient material adapted to deform to allow passage of said rigid dart nose in response to a predetermined axial force;   c) applying axial force to said dart; and   d) passing said dart through said seat.   
     
     
         9 . The method of  claim 8 , wherein said seat returns to substantially its original size following passage of said dart. 
     
     
         10 . The method of  claim 9 , wherein said seat does not permanently yield in response to passage of said dart. 
     
     
         11 . The method of  claim 9 , wherein said dart catcher apparatus further comprises a receptacle disposed below said seat adapted to receive a dart passing through said seat. 
     
     
         12 . The method of  claim 11 , wherein said receptacle comprises a substantially cylindrical housing defining an inner chamber and at least one flow port extending from said inner chamber through said housing. 
     
     
         13 . The method of  claim 12 , wherein said at least one flow port comprises an elongate aperture.