Abstract:
A release mechanism for a downhole tool is actuated by radial movement of a locking member. The locking member provided as much as full circumferential support in the locked position and once released can be prevented from re-gripping the previously connected elements. Illustrative examples of the mechanism for radial movement for release comprise sleeves that expand and radially oriented pistons. Shear pins or collets are not used to hold the components together in the preferred embodiment. Internal pressure fluctuations before initiating the release sequence will not cause unwanted release. The mechanism is applicable to a variety of downhole tools and is illustrated in the context of a hydraulic release.

Description:
FIELD OF THE INVENTION  
       [0001]     The field of this invention is a release device for downhole tools that relies on expansion or radial movement to effect release of components previously held together.  
       BACKGROUND OF THE INVENTION  
       [0002]     Downhole tool frequently involve mechanisms to hold one portion of the tool to another. This is sometimes accomplished using shearable members such as shear pins or similar devices such as spring loaded collets. Typically pistons are used with such locking elements to respond to built up pressure after landing a ball on a seat and adding pressure from above. Some of the problems with these designs lead to premature failure of the locking device creating a problem downhole. If the tool is a disconnect, for example, it may release prematurely forcing a fishing operation to retrieve the lowermost portion that falls in the wellbore. One of the reasons for the premature failure of the shear pins is the weight of the piston that has to ultimately move to break the shear pin or release a collet. Due to cyclical loading during run in or from operation of adjacent downhole equipment such as downhole pumps the shock loads on the piston combined with its weight can be sufficient to shear a pin or otherwise allow relative movement of tool components at an inopportune time.  
         [0003]     Other limitations of prior designs is that the locking members that were used to hold the components fixed to each other provided only discrete areas of contact about the periphery of the components causing elevated stress levels due to the minimal contact areas and creating another weakness that has in the past lead to premature failure.  
         [0004]     What is needed is a design to eliminate these premature failures with a design that does not become even more complex than the prior designs sought to be upgraded. The present invention offers solutions that meet this need. The shear pin or collet designs that were prone to failure in the past have been eliminated. In an embodiment of the invention locking components offer as much as 360 degree support to minimize shear failure. Unlocking is accomplished by radial movement of the locking members to release the grip between the members initially held together. Once the release is accomplished a lockout feature can be provided to prevent re-engagement. Radial movement can be accomplished in a variety of ways with pistons or a sleeve that bends responsive to applied internal pressure or by other mechanisms. The design that provides as much as full circumferential contact prior to unlocking can also take on a variety of forms. The application can be for a host of downhole tools although aspects of the preferred embodiment will be described in the context of a hydraulic release tool.  
         [0005]     The prior art release tools that suffered from the limitations described above are represented by the following list of U.S. patents, presented as some examples of the issues affecting the prior art designs of hydraulic disconnects: U.S. Pat. Nos. 5,526,888; 6,527,048; 6,439,305; 6,408,946; 6,349,767; 6,318,470; 6,053,262; 6,053,250; 5,984,029; 5,960,884; 5,787,982; 5,718,291 and 4,984,632. Also of interest is U.S. Application 2004/0045704.  
         [0006]     Those skilled in the art will appreciate the varied applications of the present invention and its advantages from a detailed discussion of two embodiments and the claims, which appear below.  
       SUMMARY OF THE INVENTION  
       [0007]     A release mechanism for a downhole tool is actuated by radial movement of a locking member. The locking member provided as much as full circumferential support in the locked position and once released can be prevented from re-gripping the previously connected elements. Illustrative examples of the mechanism for radial movement for release comprise sleeves that expand and radially oriented pistons. Shear pins or collets are not used to hold the components together in the preferred embodiment. Internal pressure fluctuations before initiating the release sequence will not cause unwanted release. The mechanism is applicable to a variety of downhole tools and is illustrated in the context of a hydraulic release. 
     
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0008]      FIGS. 1   a - 1   b  show the run in position of the preferred embodiment in a half section view;  
         [0009]      FIGS. 2   a - 2   b  are the view of  FIGS. 1   a - 1   b  but in the beginning to release position;  
         [0010]      FIGS. 3   a - 3   b  are the view of  FIGS. 2   a - 2   b  but in the fully released position;  
         [0011]      FIGS. 4   a - 4   b  are a half section view of an alternative embodiment in the run in position;  
         [0012]      FIG. 5  is a section view along lines  5 - 5  of  FIG. 4   b.   
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]     Referring to  FIGS. 1   a - 1   b , the upper body  10  is secured releaseably to lower body  12  through locking ring  14 . Preferably, locking ring  14  is made of segments that are held against the upper body  10  by band springs  16  or other biasing member or members. The number and placement of the band springs  16  is variable with the application. In the preferred embodiment the band springs  16  straddle the first projection-depression mating profile  18  that is disposed between the upper body  10  and the locking ring  14 . A second projection-depression mating profile  20  is disposed between the locking ring  14  and the lower body  12 . Profiles  18  and  20  can take a variety of configurations. Those skilled in the art will appreciate that the greater the number of undulations the smaller the shear load on each undulation. Similarly, the greater the height from valley to peak the smaller the shear load on each undulation. To the extent the locking ring  14  is in segment, the segments can take the full circumference for run in to reduce the shear load on each undulation. While the locking ring  14  is a complete sleeve that either expands for release or breaks into segments in response to a radial force, there again the shear load on each undulation is reduced. In fact, any form of locking profile that will resist shear loading can be used for profiles  18  and  20 . To hold the profiles  18  and  20  together during run in and to prevent chatter that can cause premature wear, a spring  22  is supported off the lower body  12  to push against sleeve  24  that bears against the upper body  10 . A wiper ring  26  prevents debris from reaching cavity  28  where spring  22  resides while letting pressure in passage  30  pass to the back side of expansion sleeve or actuator  32 . Along the same lines one or more ports  34  are covered by a flexible ring  36  to handle pressure surges in passage  30  by lifting off ports  34  to equalize pressure on both sides of expansion sleeve  32 .  
         [0014]     Upper body  10  has a seat  38  to catch an object (not shown) to allow pressure buildup through ports  40 . Upper seals  42  have preferably a greater diameter than lower seals  44  so that pressure directed through ports  40  bows out the sleeve  32 , as shown in  FIG. 2   a . Since the upper end of the locking ring  14  overlays the expanding portion of sleeve  32 , outward movement of sleeve  32  spreads apart profile  18  and narrows any gap in profile  20  with the result being release of the lower body  12  from the upper body  10 . The locking ring  14  moves radially a sufficient distance so that a shoulder  46  moves away from shoulder  48  at the lower end of sleeve  32 . Since the diameter of seals  42  is greater than seals  44  the pressure entering ports  40  puts a net downward force on sleeve  32  as well as pushing a part of it out to move the locking ring  14  radially outwardly. As soon as shoulder  46  clears shoulder  48  the net downward force moves sleeve  32  down until it lands on travel stop  50 , as shown in  FIG. 3   b . In this position, the sleeve  32  prevents the locking ring  14  from moving radially inwardly to reconnect profile  18 . In this preferred design, once release occurs the tool is prevented from reconnecting to the run in position.  
         [0015]     It should be noted that a rupture disc or equivalent removable barrier  52  is used to open a circulation port if for any reason an emergency circulation path is needed prior to dropping the flow blockage device. A fishing neck  54  on the lower body  12  becomes exposed after tool separation to facilitate fishing out the lower body  12  and anything attached to it, if desired. Seal  56  keeps out annulus pressure and allows pressurizing into ports  40  when seat  38  is obstructed. One or more matched flats  58  can be provided where the lower body  12  overlaps upper body  10  to allow torque transmission through the tool when the components are attached as in the run in position shown in  FIGS. 1   a - 1   b.    
         [0016]     In operation, the tool stays together until an object is dropped to obstruct seat  38 . Pressure buildup in passages  40  flex the sleeve  32  radially outwardly to the point where locking ring  14  is forced radially outwardly as well. The profile  18  disengages and shoulder  46  moves radially and clear of shoulder  48  at the lower end of sleeve  32 . A net force downwardly exists on sleeve  32  because the diameter of seals  42  exceeds the diameter of seals  44 . As a result the sleeve  32  is forced under the now expanded locking ring  14  to prevent band springs  16  from reconnecting profile  18 .  
         [0017]     An alternative embodiment is shown in  FIGS. 4 and 5 . An upper body  60  is connected to a lower body  62  by a locking ring  64  that has a profile  66  to engage the lower body  62  and a profile  68  to engage the upper body  60 . One or more band springs  70  bias the locking ring  64  inwardly closing the profile  68 . At least one port  72  leads from passage  74  to a piston or actuator  76 . Piston  76  has a seal ring  78  and a retainer  80  to hold it in a retracted position shown in  FIG. 4   b . Preferably retainer  80  is a flexible c-ring. Port  82  extends from passage  74  to annular space  84  sealed by locking sleeve  86  and seals  88  and  90 . Due to the diameter of seal  88  being larger than the diameter of seal  90  a net downward force is applied to sleeve  86  from pressure in port  82 . Pressure in port  72  pushes the piston  76  out against the force of the retainer  80  and forces the locking ring  64  radially outwardly to undo the profile  68  for a release. As that happens sleeve  86  is pushed down and under the locking ring  64  preventing it from moving back in radially.  
         [0018]     Other features of this embodiment include a rupture plug or equivalent removable barrier  92  for the same purpose previously stated. A fishing neck  94  and a seal  96  to isolate annulus pressure. A passage  98  is for equalizing pressure surges in passage  74  across the piston  76 . A seat  100  catches an object and allows pressure buildup in passages  72  and  82 . A spring similar to  22  can also be employed in this embodiment for the same purpose.  
         [0019]     Those skilled in the art will appreciate the wide application of the present invention to downhole tools of many types. The disadvantage of the prior designs featuring longitudinally shifting pistons that are movable after a shear or breakable element is removed and replaced with an actuating member that moves radially. The piston or actuating member does not need a restraint primarily because of its radial direction of movement. Longitudinal movement of the actuating member is simply precluded from the manner in which the parts are assembled. Pressure surges internally do not cause premature release because the actuator for release is pressure balanced and will not move until the desired time. The engagement between the components against shear forces tending to separate them can be a majority to as much as full 360 degree contact in one or multiple layers such that contact stresses in a particular location are minimized. Lower circumferential contact lengths are also envisioned. A positive lock feature is incorporated to prevent re-engagement of the components once they are released from each other. The radial movement of the actuating member can occur by expansion of a sleeve, radial movement of one or more pistons or by other equivalent structures. Because this movement is radial shock loading from running in and stopping is not an issue as the manner in which the parts are assembled and subsequently move prevents them from actuation under shock loading in an uphole or downhole direction.  
         [0020]     While the preferred embodiment has been set forth above, those skilled in art will appreciate that the scope of the invention is significantly broader and as outlined in the claims which appear below.