Braking device for tool strings

Abstract

An embodiment of the invention discloses a restraint mechanism ( 12 ) of a braking device ( 10 ) for location in tubing ( 16 ) such as the casing of an oil or gas well. The braking device ( 10 ) forms part of a tool string which is run into the tubing ( 16 ) on a wireline and, in the event that the wireline breaks or is severed, the braking device ( 10 ) and the associated tool string falls through the tubing. The restraint mechanism ( 12 ) includes a sensor assembly ( 18 ), and a brake mechanism ( 22 ). The sensor assembly ( 18 ) senses the uncontrolled movement and provides an appropriate output causing activation of the brake mechanism ( 22 ), bringing the braking device ( 10 ) and tool string to a controlled stop.

1 . A restraint mechanism for restraining a member adapted to be moved axially through tubing, the restraint mechanism comprising: 
 a brake for selectively restraining the member in the tubing; and    brake activating means for activating the brake on sensing a condition indicative of uncontrolled movement of the member.    
     
     
         2 . A restraint mechanism as claimed in  claim 1 , wherein the member comprises an elongate body housing the brake and the brake activating means.  
     
     
         3 . A restraint mechanism as claimed in either of claims  1  or  2 , further comprising a sensor for sensing uncontrolled movement of the member.  
     
     
         4 . A restraint mechanism as claimed in  claim 3 , wherein the sensor is adapted to provide a continuous output as the member is moved within the tubing, and indicates uncontrolled movement of the member when the output reaches a predetermined value.  
     
     
         5 . A restraint mechanism as claimed in  claim 3 , wherein the sensor is adapted to only provide an output on the member experiencing uncontrolled movement.  
     
     
         6 . A restraint mechanism as claimed in any preceding claim, wherein the brake is adapted to be moved between a retracted position and an extended position, for restraining the member in the tubing.  
     
     
         7 . A restraint mechanism as claimed in  claim 6 , wherein the brake is initially retained in the retracted position.  
     
     
         8 . A restraint mechanism as claimed in either of claims  6  or  7 , wherein the brake is biassed towards one of the retracted or extended positions.  
     
     
         9 . A restraint mechanism as claimed in any one of  claims 6  to  8 , wherein the brake is retained in the extended position following activation by the brake activating means.  
     
     
         10 . A restraint mechanism as claimed in any preceding claim, wherein the brake comprises a plurality of circumferentially disposed slips adapted to be moved to an extended position.  
     
     
         11 . A restraint mechanism as claimed in  claim 10 , wherein the slips define a ratchet arrangement to retain the extension of the slips.  
     
     
         12 . A restraint mechanism as claimed in any one of  claims 3  to  11 , wherein the sensor comprises an accelerometer for sensing the rate of change of velocity of the member.  
     
     
         13 . A restraint mechanism as claimed in  claim 12 , wherein the restraint mechanism further comprises a processor, coupled to the accelerometer, for receiving data concerning the acceleration of the member, and for providing an appropriate output in the event that the member experiences uncontrolled movement, to activate the brake.  
     
     
         14 . A restraint mechanism as claimed in any preceding claim, wherein the brake activating means comprises a solenoid latch.  
     
     
         15 . A restraint mechanism as claimed  claim 14 , wherein the brake comprises a plurality of circumferentially disposed slips which are retained in a retracted position by one or more radially movable locking keys disposed in the member, each key being adapted to engage a portion of a slip, and being maintained in the retaining position by the solenoid latch.  
     
     
         16 . A restraint mechanism as claimed in any preceding claim, wherein the brake activating means comprises one or more extendable members which are adapted to extend in the event of uncontrolled movement of the member.  
     
     
         17 . A restraint mechanism as claimed in  claim 16 , wherein the extendable members are pivotably coupled to a body of the member.  
     
     
         18 . A restraint mechanism as claimed in either of claims  16  or  17 , wherein the extendable members are coupled to each other in a scissors configuration.  
     
     
         19 . A restraint mechanism as claimed in any one of  claims 16  to  18 , wherein the extendable members comprise two arms.  
     
     
         20 . A restraint mechanism as claimed in any one of  claims 16  to  19 , wherein the member is adapted to be supported, from a support member coupled to the brake activating means, and the weight of the member and any associated tools suspended via the brake activating means retains the brake activating means in the retracted position.  
     
     
         21 . A restraint mechanism as claimed in any one of  claims 16  to  20 , wherein the brake activating means further comprises an activating member, coupled to the extendable members, for moving the extendable members between a retracted position and an extended position.  
     
     
         22 . A restraint mechanism as claimed in  claim 21 , wherein the activating member is coupled at a first end to the support member and at a second end to the extendable members.  
     
     
         23 . A restraint mechanism as claimed in either of claims  21  or  22 , wherein the brake activating means further comprises biassing means, the biassing means serving to bias the activating member and therefore the extendable members towards the extended position.  
     
     
         24 . A restraint mechanism as claimed in any one of  claims 16  to  23 , wherein the brake activating means includes a damper to prevent transient shocks or accelerations of the member from activating the brake.  
     
     
         25 . A restraint mechanism as claimed in any one of  claims 3  to  11 , further comprising a sensor for sensing uncontrolled movement of the member, and wherein the sensor comprises a mechanical sensor assembly.  
     
     
         26 . A restraint mechanism as claimed in any one of  claims 3  to  11 , or  claim 25 , wherein the sensor comprises a wheel adapted to engage an inner surface of the tubing and thus sense relative movement between the sensor and the tubing.  
     
     
         27 . A restraint mechanism as claimed in  claim 26 , wherein the wheel is biassed into engagement with the tubing by a spring-loaded arm.  
     
     
         28 . A restraint mechanism as claimed in any preceding claim, wherein the brake activating means activates the brake in response to fluid pressure.  
     
     
         29 . A restraint mechanism as claimed in any one of  claims 3  to  12 ,  26 ,  27  or  28 , further comprising a sensor for sensing uncontrolled movement of the member, and wherein the brake activating means comprises a pump coupled to the sensor.  
     
     
         30 . A restraint mechanism as claimed in  claim 29 , wherein the pump is an axial flow pump coupled to the sensor by a pump drive shaft.  
     
     
         31 . A restraint mechanism as claimed in either of claims  29  or  30 , wherein the pump has a fluid conduit connected in a closed loop between a pump outlet and a pump inlet, and a restriction therein for restricting fluid flow in the conduit and, in use, maintaining fluid pressure higher at the outlet than at the inlet.  
     
     
         32 . A restraint mechanism as claimed in any one of  claims 29  to  31 , further comprising a pressure compensator to compensate for variations in hydrostatic pressure as the member is moved through the tubing.  
     
     
         33 . A restraint mechanism as claimed in any one of  claims 29  to  32 , wherein the brake comprises a plurality of circumferentially disposed slips which are initially retained in a retracted position by a lock mechanism, wherein the lock mechanism is fluid pressure activated and comprises an axially movable piston, said piston disposed in communication with an outlet of the pump.  
     
     
         34 . A restraint mechanism as claimed in  claim 33 , wherein the piston is axially movable to selectively release the brake, and is biassed towards a brake retaining position.  
     
     
         35 . A restraint mechanism as claimed in either of claims  33  or  34 , wherein the slips are retained in a retracted position by one or more radially movable locking keys which are adapted to each engage a profile of a portion of a respective slip, said keys being maintained in the retaining position by a part of the piston.  
     
     
         36 . A restraint mechanism as claimed in any one of  claims 3  to  11 , wherein the sensor comprises a pressure sensitive element for detecting pressure differentials resulting from movement of the member through fluid-filled tubing.  
     
     
         37 . A restraint mechanism as claimed in any preceding claim, wherein the member defines a fluid passage through which fluid flows as the member is moved through the tubing, the passage containing a piston which is responsive to fluid pressure to activate the brake.  
     
     
         38 . A restraint mechanism as claimed in  claim 37 , wherein the passage defines a flow restriction, such that the pressure differential across the piston is flow-related.  
     
     
         39 . A restraint mechanism as claimed in  claim 38 , wherein the flow restriction is adjustable, to vary a brake activation value.  
     
     
         40 . A restraint mechanism as claimed in any one of  claims 37  to  39 , wherein the brake comprises a plurality of circumferentially disposed slips and wherein the piston is coupled to a cam to urge the slips to an extended position.  
     
     
         41 . A member adapted to be suspended from a support member in tubing and to be moved axially therein, the member having a restraint mechanism comprising: 
 a brake; and    brake activating means for activating the brake in the presence of a condition indicative of uncontrolled movement of the member.    
     
     
         42 . A member adapted to be moved axially through tubing, the member having a restraint mechanism comprising: 
 a sensor for sensing uncontrolled movement of the member;    a brake adapted to be activated to engage the tubing to restrain the member therein; and    brake activating means for activating the brake on receipt of an output from the sensor indicative of uncontrolled movement of the member.    
     
     
         43 . A method of restraining a member from uncontrolled movement through tubing, the method comprising the steps of: 
 providing a brake; and.    activating the brake to restrain the member when a condition indicative of uncontrolled movement of the member is experienced.    
     
     
         44 . The method of  claim 43 , further comprising the step of providing a sensor for sensing uncontrolled movement of the member, the sensor being capable of generating a sensor output indicating an uncontrolled movement of the member, to activate the brake.