Drifting System

Abstract

Disclosed is a drifting system ( 300 ) comprising a drifting element ( 100 ) having a wall ( 114 ) defining a through flow passage ( 102 ) extending in an axial direction ( 104 ) of the drifting element and a catcher sub having a through hole. In accordance with embodiment of the herein disclosed subject matter the catcher sub has a seat for receiving the drifting element ( 100 ) in the through hole. The through flow passage ( 102 ) of the drifting element ( 100 ) has a first cross section of flow ( 106 ) in a first axial region ( 108 ) of the drifting element ( 100 ) and has a second, smaller cross section of flow ( 110 ) in a second axial region ( 112 ) of the drifting element ( 100 ) located downstream the first axial region ( 108 ). Further, the wall ( 114 ) of the drifting element ( 100 ) has a lateral outlet ( 116 ) extending from the through flow passage ( 102 ) in the second axial region ( 112 ) and/or from the through flow passage ( 102 ) at a location upstream the second axial region ( 112 ) through the wall.

1 . A drifting system comprising:
 a drifting element having a wall defining a through flow passage extending in an axial direction of the drifting element; and   a catcher sub having a through hole;   the catcher sub having a seat for receiving the drifting element in the through hole;   the through flow passage having a first cross section of flow in a first axial region of the drifting element;   the through flow passage having a second cross section of flow in a second axial region of the drifting element;   the first axial region being located upstream the second axial region;   the second cross section of flow being smaller than the first cross section of flow; and   the wall of the drifting element having a lateral outlet extending from the through flow passage in the second axial region and/or from the through flow passage at a location upstream the second axial region through the wall.   
     
     
         2 . The drifting system according to  claim 1 , wherein the catcher sub has at least one closure element closing the lateral outlet of the drifting element when the drifting element is received in the seat. 
     
     
         3 . The drifting system according to  claim 2 , wherein the closure element is a surface portion of the catcher sub facing the lateral outlet when the drifting element is received in the seat. 
     
     
         4 . The drifting system according to  claim 1 , wherein the lateral outlet is configured for generating through the lateral outlet a flow which is uniformly distributed about a circumference of the drifting element. 
     
     
         5 . The drifting system according to  claim 4 , wherein the lateral outlet comprises at least two outlet ports of identical cross section of flow; and
 the at least two outlet ports are evenly spaced about an outer circumference of the drifting element.   
     
     
         6 . The drifting system according to  claim 1 , wherein the lateral outlet comprises at least one outlet port extending through the wall from the through flow passage in the first axial region of the drifting element. 
     
     
         7 . The drifting system according to  claim 6 , wherein the drifting element has an outer conical surface portion, particularly in the first axial region; and
 the catcher sub has a conical inner surface portion forming the seat and being adapted for receiving the outer conical surface portion to thereby catch the drifting element.   
     
     
         8 . The drifting system according to  claim 1 , wherein the lateral outlet comprises at least one outlet port extending through the wall from the through flow passage in the second axial region of the drifting element. 
     
     
         9 . The drifting system according to  claim 5 , wherein at least one outlet port has a conical cross-section at least in an axial section plane, wherein the conical cross-section opens up towards the through flow passage. 
     
     
         10 . A drifting element comprising:
 a wall defining a through flow passage extending in an axial direction of the drifting element;   the through flow passage having a first cross section of flow in a first axial region of the drifting element;   the through flow passage having a second cross section of flow in a second axial region of the drifting element;   the first axial region being located upstream the second axial region;   the second cross section of flow being smaller than the first cross section of flow; and   the wall of the drifting element having a lateral outlet extending from the through flow passage in the second axial region and/or from the through flow passage at a location upstream the second axial region through the wall.   
     
     
         11 . A catcher sub for catching a drifting element according to  claim 10 , the catcher sub comprising:
 a through hole; and   a seat for receiving the drifting element in the through hole.   
     
     
         12 . The catcher sub according to  claim 11 , the catcher sub having an inner conical surface portion forming the seat. 
     
     
         13 . The catcher sub according to  claim 12 , the inner conical surface portion forming an angle with an upstream direction and the angle being smaller than 60 degrees. 
     
     
         14 . A method of operating the drifting system according to  claim 1 , the method comprising:
 pumping the drifting element down a drill string containing the catcher sub; and   monitoring a pressure in the drillstring above the drifting element.   
     
     
         15 . The method according to  claim 14 , wherein the through flow passage of the drifting element has a clearance diameter which is larger than a diameter of an activation seat of a tool that is located downstream the catcher sub, the method comprising:
 pumping the drifting element down the drillstring until an increase in the monitored pressure indicates landing of the drifting element in the seat of the catcher sub; and   pumping an activation element for the tool down the drillstring and through the through flow passage of the drifting element into the activation seat of the tool.   
     
     
         16 . A drifting system comprising:
 a drifting element having a wall defining a through flow passage extending in an axial direction of the drifting element;   a catcher sub having a through hole;   the catcher sub having a seat for receiving the drifting element in the through hole;   the through flow passage having a first cross section of flow in a first axial region of the drifting element;   the through flow passage having a second cross section of flow in a second axial region of the drifting element;   the first axial region being located upstream the second axial region;   the second cross section of flow being smaller than the first cross section of flow;   the wall of the drifting element having a lateral outlet extending from the through flow passage in the second axial region and from the through flow passage at a location upstream the second axial region through the wall;   the wall being a tubular wall extending from the through flow passage in the first axial region;   the lateral outlet comprising at least one first outlet port extending from the through flow passage in the first axial region through the wall to an conical outer surface of the drifting element;   the lateral outlet comprising at least one second outlet port extending from the through flow passage in the second axial region through the wall to an outer surface of the drifting element;   the lateral outlet being configured for generating through the lateral outlet a flow which is uniformly distributed about a circumference of the drifting element;   upstream the second axial region the wall of the drifting element comprising an inner conical surface portion which opens up in the upstream direction;   at least part of the inner conical surface portion being provided in the first axial region;   the inner conical surface portion leading to the larger cross section of flow in the first axial region compared to the cross section of flow in the second axial region;   the wall comprising, at least in the second axial region, an inner straight surface portion parallel to the axial direction;   the drifting element having an outer conical surface portion which is adapted for engaging a seat of a catcher sub;   the outer conical surface portion of the drifting element forming an acute angle with respect to the axial direction;   at least one of the outlet ports extending at an acute angle to the axial direction which acute angle is equal to or smaller than 90 degrees; and   the drifting element further comprising a fish neck.