Downhole tool having a shock-absorbing sleeve

Abstract

An apparatus having a shock-absorbing sleeve is disclosed. The apparatus comprises a housing, an axially moveable sleeve received in the housing and a sealed annular space having a fixed volume axially between the housing and the sleeve. A barrier axially moveable with the sleeve divides the annular space into a first and a second chambers. The first and second chambers are filled with uncompressible dampening fluid. One or more metering passages across the barrier fluidly connect the first and chambers. During the axial movement of the sleeve, the volume of the first chamber is reduced and that of the second chamber is increased, forcing the fluid in the first chamber to flow into the second chamber in a controlled manner to dampen the movement of the sleeve.

What is claimed is: 
     
         1 . A downhole apparatus comprising:
 a tubular housing along a tubing string;   a sleeve located within the housing and axially moveable therein from a first position to a second position; and   a first annular chamber radially intermediate the housing and the sleeve, said first annular chamber containing a first dampening fluid and being capable of controllably releasing the first dampening fluid under pressure; wherein   when the sleeve moves from the first position to the second position, the first dampening fluid is pressurized and controllably released for controlling the speed of the sleeve movement.   
     
     
         2 . The apparatus of  claim 1  wherein the first dampening fluid is a substantially incompressible fluid. 
     
     
         3 . The apparatus of  claim 2  wherein the first dampened fluid is grease. 
     
     
         4 . The apparatus of  claim 2  wherein the first dampened fluid has a viscosity index in the range between 80 and 110. 
     
     
         5 . The apparatus of  claim 2  wherein the first dampened fluid has a viscosity index of 90. 
     
     
         6 . The downhole apparatus of  claim 1  further comprising:
 a second annular chamber radially intermediate the housing and the sleeve, and axially immediately adjacent the first annular chamber; wherein the second annular chamber is in fluid communication with the first chamber for receiving the first dampening fluid released from the first chamber. 
 
     
     
         7 . The apparatus of  claim 6  wherein the first chamber has a first volume and the second chamber has a second volume, the first volume being smaller than the second volume. 
     
     
         8 . The apparatus of  claim 6  wherein the second chamber contains a second dampening fluid. 
     
     
         9 . The apparatus of  claim 8  wherein the first and second dampening fluids are like fluids. 
     
     
         10 . The apparatus of  claim 8  wherein the first and second dampening fluids are different fluids. 
     
     
         11 . The downhole apparatus of  claim 6  wherein the first and second chambers are formed from an annular space radially intermediate the housing and the sleeve, and wherein an annular barrier divides the annular space into the first and second chambers. 
     
     
         12 . The downhole apparatus of  claim 11  wherein the annular space is located at a fixed location with respect to the housing, and the annular barrier is fixed to the sleeve and moveable therewith, the movement of the annular barrier simultaneously reducing the volume of the first chamber and enlarging the volume of the second chamber. 
     
     
         13 . The apparatus of  claim 12  wherein said barrier comprises a seal arrangement for sealing between the sleeve and the housing. 
     
     
         14 . The apparatus of  claim 12  wherein the barrier is threadably engaged along the sleeve. 
     
     
         15 . The downhole apparatus of  claim 11  wherein the annular space is located at a fixed location with respect to the sleeve and moveable therewith, and the annular barrier is located at a fixed location with respect to the housing, the movement of the annular barrier simultaneously reducing the volume of the first chamber and enlarging the volume of the second chamber. 
     
     
         16 . The downhole apparatus of  claim 11  wherein the apparatus further comprises at least one metering passage fluidly connecting the first and second chambers across the barrier. 
     
     
         17 . The apparatus of  claim 16  wherein the at least one metering passage extends axially through the interface of the sleeve and the barrier. 
     
     
         18 . A method of moving a sleeve in a housing axially from a first position to a second position, said housing being used in a tubing string, said method comprising:
 providing a first annular chamber radially intermediate the housing and the sleeve;   enclosing a first dampening fluid in the first chamber;   moving the sleeve from the first position to the second position; and   during the movement of the sleeve,
 pressurizing the first dampening fluid in the first chamber, and 
 controllably releasing the pressurized first dampening fluid out of the first chamber for controlling the speed of the sleeve. 
   
     
     
         19 . The method of claim  25  further comprising:
 providing a second annular chamber radially intermediate the housing and the sleeve, and axially immediately adjacent the first annular chamber, wherein the second annular chamber is in fluid communication with the first chamber; and 
 receiving, in the second chamber, controlled release of fluid out of the first chamber during the movement of the sleeve. 
 
     
     
         20 . A method of moving a sleeve in a housing axially from a first position to a second position, said housing being used in a tubing string, said method comprising:
 providing a closed annular space radially intermediate the housing and the sleeve;   dividing the annular space into a first and a second chambers in fluid communication;   enclosing incompressible fluid in the first and second chambers;   moving the sleeve from the first position to the second position; and   during the movement of the sleeve,
 simultaneously reducing the volume of the first chamber and increasing the volume of the second chamber to pressurize the fluid in the first chamber and force the fluid in the first chamber to controllably flow into the second chamber for dampening the sleeve's movement.