Downhole releasable connector

Abstract

A downhole releasable connector is described for releasably connecting a wireline to a downhole tool. The connector comprises a first portion arranged to be connected to a wireline and a second portion arranged to be connected to a downhole tool. A locking arrangement is arranged to lock the first and second portions together when in a first position and to release the first and second portions from each other when in a second position. A reversible drive mechanism is provided to move the locking arrangement between the first and second portions. As the drive mechanism is reversible, it is able to lock and unlock the locking arrangement and so release and reconnect the first and second portions of the connector so that it can be tested prior to use providing increased confidence in the tool and allowing inspection of critical parts within the release mechanism.

1 . A downhole releasable connector for releasably connecting a wireline to a downhole tool, the connector comprising
 a first portion arranged to be connected to a wireline and to receive an electrical supply from the surface and arranged to be connected to a second portion connected to and/or including a downhole tool;   a locking arrangement arranged to lock the first portion to the second portion when in a first position and to release the first portion from the second portion when in a second position and   a reversible drive mechanism to move the locking arrangement between the first and second positions;   wherein the first portion is arranged to conduct electricity therethrough from the electrical supply to the second portion via a pair of electrical contacts when in the first locked position and wherein movement of the locking arrangement to the released second position separates the two electrical contacts from each other such that the contact connected to the electrical supply is isolated from the external environment allowing equipment above the electrical contact, in use, to continue to operate in electrically conductive well fluids.   
     
     
         2 . A downhole releasable connector according to  claim 1 , wherein the first and second portions have a common axis and the reversible drive mechanism is arranged to reversibly move a locking member back and forth in the direction of the common axis. 
     
     
         3 . A downhole releasable connector according to  claim 1  or  claim 2 , wherein the locking member is arranged to force one or more latching members attached to one of the first and second portions outwardly into contact with one or more corresponding engagement surfaces on the other of the first and second portions when in a first locked position and to allow the one or more latching members to separate from the one or more corresponding engagement surfaces when in a second released position. 
     
     
         4 . A downhole releasable connector in accordance with any one of the preceding claims, wherein the pair of electrical contacts comprise a mechanically actuatable electrical switch for conducting electricity between the first and second portions when closed and for disconnecting supply to the second portion when opened upon release of the first and second portions from each other. 
     
     
         5 . A downhole releasable connector according to any one of the preceding claims, wherein one of the contacts is connected to a movable shaft of the locking arrangement. 
     
     
         6 . A downhole releasable connector according to  claim 5 , wherein the two electrical contacts are concentric rings, with the internal annular surface of one ring arranged to contact the external annular surface of the other ring when the first and second portions are locked together. 
     
     
         7 . A downhole releasable connector according to any one of the preceding claims, further comprising a valve arranged to equalise the internal and external pressure of the connector when the first and second portions are released from each other. 
     
     
         8 . A downhole releasable connector according to  claim 7 , wherein the valve is actuated by the locking arrangement, releasing the first and second portions from each other. 
     
     
         9 . A downhole releasable connector according to any one of the preceding claims, including a position sensor to determine the status of the locking arrangement. 
     
     
         10 . A downhole releasable connector according to  claim 9 , wherein the position sensor determines whether the locking arrangement is in a first locked position, a second released position or therebetween. 
     
     
         11 . A tool string including one or more releasable connectors according to any one of the preceding claims 
     
     
         12 . A method of operating a downhole releasable connector for releasably connecting a wireline to a downhole tool, the method comprising
 operating a drive mechanism in a first direction to move a locking arrangement to lock first and second portions of a tool string together and to close an electrical connection between the two by engaging two electrical contacts, one of which is arranged to receive an electrical supply from the surface, and   operating the drive mechanism in the reverse direction to move the locking arrangement to release the first and second portions from each other and to open an electrical connection between the two by separating the two electrical contacts such that the electrical contact arranged to receive an electrical supply from the surface is isolated from the external environment.   
     
     
         13 . A method of operating a downhole releasable connector according to  claim 12 , wherein operating the drive mechanism in the reverse direction opens a mechanically actuatable electrical switch preventing the conduction of electricity between the first and second portions. 
     
     
         14 . A method of operating a downhole releasable connector according to  claim 12  or  claim 13 , wherein operating the drive mechanism in the reverse direction actuates a valve equalising the internal and external pressure of the connector. 
     
     
         15 . A downhole releasable connector substantially as hereinbefore described with reference to the accompanying drawings. 
     
     
         16 . A tool string substantially as hereinbefore described with reference to the accompanying drawings. 
     
     
         17 . A method of operating a downhole releasable connector substantially as hereinbefore described with reference to the accompanying drawings.