Valve

Abstract

A downhole valve comprises a tubular body and a valve member. The valve member is normally closed and in the closed position may prevent or restrict passage of a working fluid through the body. The valve member is movable to an open position, a first working fluid pressure differential being necessary to move the valve member from the closed position and a lower second working fluid pressure differential being necessary to maintain the valve member in the open position.

1 . A downhole valve comprising:
 a tubular body;   a valve member, the valve member being normally closed to at least restrict passage of a working fluid through the body, and being movable to an open position, a first working fluid pressure differential being necessary to move the valve member from the closed position and a lower second working fluid pressure differential being necessary to maintain the valve member in the open position.   
   
   
       2 . The valve of  claim 1 , wherein the closed valve prevents flow through the valve. 
   
   
       3 . The valve of  claim 1 , wherein the closed valve permits flow through the valve. 
   
   
       4 . The valve of any preceding claim, wherein the valve member is configured to induce a fluid-flow related force tending to maintain the valve member open. 
   
   
       5 . The valve of any of the preceding claims, wherein the valve member defines a restriction, and flow of the working fluid through the valve member creates a pressure differential across at least a portion of the valve member. 
   
   
       6 . The valve of any of the preceding claims, wherein the body defines a valve seat. 
   
   
       7 . The valve of any of the preceding claims, wherein the valve is arranged to define a first area over which fluid pressure acts on the valve member when the valve member is in the closed position. 
   
   
       8 . The valve of  claim 7 , wherein the valve defines a larger second area configured to induce a valve-opening fluid pressure force when the valve member is open and fluid is flowing through the valve. 
   
   
       9 . The valve of  claim 7  or  8 , wherein the body defines a valve seat and said valve seat defines said first area. 
   
   
       10 . The valve of any of the preceding claims, wherein the valve member comprises a plug portion adapted for cooperating with a valve seat. 
   
   
       11 . The valve of  claim 10 , wherein the valve is arranged such that in the open position the plug portion is spaced from the valve seat. 
   
   
       12 . The valve of  claim 10  or  11 , wherein the plug portion is elongate. 
   
   
       13 . The valve of  claim 10 ,  11  or  12 , wherein the plug portion has a tapered leading end for cooperating with the valve seat. 
   
   
       14 . The valve of any of the preceding claims, wherein the valve member is biased towards the closed position. 
   
   
       15 . The valve of any of the preceding claims, wherein the valve is adapted to be selectively retained in the open position. 
   
   
       16 . The valve of  claim 15 , wherein the valve is provided in combination with a valve-locking member adapted to selectively retain the valve member in the open position. 
   
   
       17 . A downhole tool comprising:
 a tubular body;   a fluid flow responsive member normally configured in a first configuration and movable to a second configuration, the arrangement being such that the member is movable from the first configuration in response to a first fluid pressure differential across at least a part of the member while a lower second fluid pressure differential across at least a part of the member will maintain the member in the second configuration.   
   
   
       18 . The tool of  claim 17 , wherein the tool is configurable such that, in the first configuration, the tool defines a first flow restriction adapted to create a fluid pressure force over a first area of the fluid flow responsive member, and the tool defines a second flow restriction adapted to create a fluid pressure force over a larger second area of said member. 
   
   
       19 . The tool of  claim 18 , wherein, in the first configuration, the area of the first flow restriction is smaller than the area of the second flow restriction. 
   
   
       20 . The tool of  claim 18  or  19  wherein, in the second configuration, the second flow restriction defines the minimum flow area through the tool. 
   
   
       21 . The tool of  claim 18 ,  19  or  20 , wherein the area of the first flow restriction increases as the member moves towards the second configuration. 
   
   
       22 . The tool of any of  claims 17  to  21 , wherein the fluid flow responsive member is a valve member. 
   
   
       23 . The tool of any of  claims 17  to  22 , wherein the flow response member is adapted to be operatively associated with another tool or device. 
   
   
       24 . A method of retaining a column of fluid in a tubular body, the method comprising:
 providing a normally closed valve in a lower portion of a tubular body;   flowing fluid through the valve to maintain the valve open; and   at least reducing the fluid flow rate to allow the valve to close and retain a column of fluid thereabove.   
   
   
       25 . The method of  claim 24 , further comprising the step of increasing the fluid pressure above the closed valve to create a first pressure differential across a portion of the valve to open the valve and permit flow through the valve, and then creating a fluid flow-related pressure differential across a larger area portion of the valve to maintain the valve open. 
   
   
       26 . A method of controlling flow through an elongate tubular body, the method comprising:
 pumping fluid through a tubular body at a first flow rate, the body comprising a fluid flow-responsive member in a first configuration; and then   increasing the fluid flow rate to produce a first fluid pressure differential across a first area to create a first actuating force, the first actuating force moving said member towards a second configuration, and with said member in the second configuration fluid flow at a higher second flow rate producing a lower second fluid pressure differential across a larger second area to create a larger second actuating force to maintain the member in the second configuration.