Circulation sub

Abstract

A circulation sub tool includes a tool body with a bore extending therethrough, a sleeve movably disposed within the bore and having a sleeve bore extending therethrough, a collet disposed within the sleeve bore, and an activation dart configured to fit within the sleeve bore. The activation dart includes a dart body, a seal disposed on an outer surface of the dart body, and a channel recessed into the outer surface of the dart body.

What is claimed is: 
     
         1 . A circulation sub tool comprising:
 a tool body with a bore extending therethrough;   a sleeve movably disposed within the bore and having a sleeve bore extending therethrough;   a collet disposed within the sleeve bore; and   an activation dart configured to fit within the sleeve bore and comprising:
 a dart body; 
 a seal disposed on an outer surface of the dart body; and 
 a channel recessed into the outer surface of the dart body. 
   
     
     
         2 . The circulation sub tool of  claim 1 , further comprising:
 a dart catcher body coupled to the tool body and comprising a dart catcher bore extending therethrough; and   a cage disposed within the dart catcher body.   
     
     
         3 . The circulation sub tool of  claim 2 , wherein the cage comprises openings that permit fluid to pass through the circulation sub tool when the activation dart is positioned in the cage. 
     
     
         4 . The circulation sub tool of  claim 2 , wherein the cage has a length long enough to hold the activation dart, a second activation dart, and two deactivation darts. 
     
     
         5 . The circulation sub tool of  claim 1 , further comprising a spring that biases the sleeve in a first position. 
     
     
         6 . The circulation sub tool of  claim 1 , further comprising:
 a port formed through a wall of the tool body; and   a sleeve port formed through a wall of the sleeve.   
     
     
         7 . The circulation sub tool of  claim 6 , wherein when the sleeve is in a sleeve open position, the port formed through the wall of the tool body and the sleeve port formed through the wall of the sleeve are aligned. 
     
     
         8 . The circulation sub tool of  claim 6 , wherein when the sleeve is in a sleeve closed position, the port formed through the wall of the tool body and the sleeve port formed through the wall of the sleeve are not aligned. 
     
     
         9 . The circulation sub tool of  claim 6 , further comprising a deactivation dart comprising:
 a dart body; and   a seal disposed on an outer surface of the dart body,   wherein, when the activation dart is seated in the collet, the deactivation dart has a length that positions a portion of the dart body to block the sleeve port when the deactivation dart is resting on the activation dart.   
     
     
         10 . The circulation sub tool of  claim 1 , wherein the collet comprises a finger having a tab disposed on a distal end of the finger. 
     
     
         11 . The circulation sub tool of  claim 10 , wherein:
 the tab includes an angled face that contacts an angled face of the activation dart when the activation dart is seated in the collet; and   the angle of the angled faces tends to move the finger radially outward when a deactivation dart is landed on the activation dart.   
     
     
         12 . The circulation sub tool of  claim 10 , wherein the tab extends into a channel formed into a surface of the activation dart when the activation dart is seated in the collet. 
     
     
         13 . The circulation sub tool of  claim 1 , wherein the channel comprises:
 a first face that is frustoconical in shape; and   a second face that is perpendicular to a central axis of the dart body.   
     
     
         14 . The circulation sub tool of  claim 1 , wherein the activation dart comprises a bore that extends through the dart body. 
     
     
         15 . The circulation sub tool of  claim 14 , wherein the activation dart comprises a nozzle that is disposed within the bore that extends through the dart body. 
     
     
         16 . The circulation sub tool of  claim 15 , wherein the bore that extends through the dart body has a first portion with a first diameter and a second portion with a second diameter. 
     
     
         17 . The circulation sub tool of  claim 16 , wherein the nozzle is disposed in the second portion. 
     
     
         18 . The circulation sub tool of  claim 15 , wherein the nozzle comprises a beveled opening. 
     
     
         19 . The circulation sub tool of  claim 1 , wherein:
 the tool body comprises a guide pin that extends into a slot of the sleeve; and   the guide pin prevents rotational movement between the sleeve and the tool body.   
     
     
         20 . The circulation sub tool of  claim 1 , wherein the channel includes a first face that tends to push fingers of the collet open when the activation dart moves in a downhole direction and a second face that prevents the activation dart from moving uphole.