Downhole apparatus and method

Abstract

A downhole tool (32) comprises a tool housing (34) defining a central bore (35) and including a fluid port (20), and a valve member (40) mounted within the housing (34) and being movable from a closed position in which the fluid port (20) is blocked to an open position in which the fluid port (20) is opened. The tool (32) further comprises a catching arrangement (41) mounted within the housing (34) and comprising one or more radially movable seat members (106), and being configurable from a free configuration in which the seat members (106) permit an object (48) to pass through the tool (32), to a catching configuration in which the seat members (106) catch an object (48) passing through the tool (32).

What is claimed is: 
     
         1 . A downhole tool, comprising:
 a housing defining a central bore and including a fluid port;   a valve member mounted within the housing and being movable from a closed position in which the fluid port is blocked to an open position in which the fluid port is opened;   a catching arrangement mounted within the housing and comprising one or more radially movable seat members, and being configurable from a free configuration in which the seat members permit an object to pass through the tool, to a catching configuration in which the seat members catch an object passing through the tool; and   a variable choke arrangement operable to choke fluid flow through the fluid port.   
     
     
         2 . The downhole tool according to  claim 1 , wherein the variable choke arrangement provides a decreasing degree of choking to a flow through the fluid port once opened. 
     
     
         3 . The downhole tool according to  claim 2 , wherein the decreasing degree of choking permits the pressure within the tool to be gradually reduced following opening of the fluid port. 
     
     
         4 . The downhole tool according to  claim 1 , wherein the variable choke arrangement permits monitoring of the downhole tool. 
     
     
         5 . The downhole tool according to  claim 1 , wherein the choke arrangement comprises a dissipating member associated with the fluid port, said dissipating member being arranged to dissipate in response to flow through the fluid port. 
     
     
         6 . The downhole tool according to  claim 5 , wherein the dissipating member defines an orifice, wherein said orifice is enlarged in response to flow through the fluid port. 
     
     
         7 . The downhole tool according to any preceding claim, wherein the variable choke arrangement is mounted on the housing. 
     
     
         8 . The downhole tool according to  claim 1 , wherein the variable choke arrangement is operable to prevent premature release of an object from the catching arrangement. 
     
     
         9 . The downhole tool according to  claim 1 , wherein the downhole tool comprises a release arrangement. 
     
     
         10 . The downhole tool according to  claim 9 , wherein the release arrangement comprises a release member. 
     
     
         11 . The downhole tool according to  claim 10 , wherein the release member is mounted within the housing. 
     
     
         12 . The downhole tool according to any of  claims 10 , wherein the release member is axially movable by the catching arrangement between a supporting position in which the release member permits the catching arrangement to be configured in its catching configuration by radially supporting the seat member in a radially inward or retracted position, towards a de-supporting position in which the release member permits the catching arrangement to be configured in a release configuration by removing the radial support to the seat members, allowing the seat members to be moved radially outwardly to permit release of a previously caught object. 
     
     
         13 . The downhole tool according to  claim 9 , wherein the release arrangement is actuated by axial movement of the catching arrangement. 
     
     
         14 . The downhole tool according to  claim 9 , wherein the release arrangement is actuated by establishing a pressure condition in the downhole tool. 
     
     
         15 . The downhole tool according to  claim 9 , wherein the choking arrangement functions to prevent premature actuation of the release arrangement. 
     
     
         16 . The downhole tool according to  claim 10 , wherein the housing defines a release recess and the release member covers this release recess when said release member is located within its supporting position, and the release member is movable within the housing towards its de-supporting position to uncover the release recess and thus permit the seat members to be moved radially outwardly and received within the release recess to permit release of an object. 
     
     
         17 . The downhole tool according to  claim 10 , wherein the release member defines a load profile, and the catching arrangement defines a load profile configured to engage a load profile on the release member to permit the catching arrangement to apply a force on the release member to move the release member towards its de-supporting position. 
     
     
         18 . The downhole tool according to  claim 10 , wherein at least one seat member comprises a load profile configured to engage a load profile on the release member to permit the release member to be moved by the catching arrangement. 
     
     
         19 . The downhole tool according to  claim 10 , wherein the catching arrangement is biased in a direction opposite to the direction in which the release member is moved to be positioned within its de-supporting position. 
     
     
         20 . A method for delivering a fluid into a wellbore, comprising:
 arranging a downhole tool within a wellbore, wherein the tool comprises:
 a tool housing defining a central bore and a fluid port; 
 a valve member mounted within the housing and initially arranged to at least partially block the fluid port; 
 a catching arrangement mounted within the housing and comprising one or more radially movable seat members, wherein the catching arrangement is initially configured in a free configuration in which the seat members permit an object to pass through the tool; and 
 a variable choke arrangement operable to choke fluid flow through the fluid port; 
   actuating the valve member to move to open the fluid port;   reconfiguring the catching arrangement from its free configuration to a catching configuration in which the seat members can catch an object passing through the tool;   delivering a fluid through the central bore and outwardly through the open fluid port; and   variably choking flow through the fluid port using the variable choke arrangement.