Abstract:
A pressure pulse signal is processed and a valve is operated to allow tubing or annulus pressure to move a piston against an atmospheric or low pressure chamber. Movement of the piston triggers the release of the dogs that previously held two components together for a separation. Redundant release mechanisms that respond to discrete pressure pulse signals are provided for backup purposes.

Description:
FIELD OF THE INVENTION 
     The field of the invention is tubular string disconnects and more particularly those controlled from the surface with a signal such as a pressure pulse pattern that results in valve movement making tubing or annulus pressure available to undermine at least on dog to allow disconnection. 
     BACKGROUND OF THE INVENTION 
     Disconnects are used downhole to release from a tool once it is set. If a work string delivering a tool gets stuck before or after delivery of a tool it is also advantageous to be able to release from the tool so that the string can be removed. After the string is removed a fishing or milling tool can be deployed to remove the stuck tool or portion of the string below the disconnect. 
     The two components are selectively held engaged against tension by one or more retainers such as dogs that extend through a window in one component into a recess in an opposing component and selectively held in that position by a sleeve or piston. An example of such a disconnect is U.S. Pat. No. 7,395,862 which has a dog 56 or U.S. Pat. No. 6,148,916 using a disconnect in the context of releasing a perforating gun where the release actuates the gun to fire. 
     Some tools release by applied tensile force above a predetermined value and can be locked against release at that value or unlocked using a remote signal such as an acoustic signal so that if the predetermined tension is then applied the connection will release. An example of this general design in an application of a fail-safe disconnect from a subsea well is U.S. Pat. No. 7,240,734, notably the unlatch tool 28. U.S. Pat. No. 6,880,637 uses hydrostatic pressure to actuate a release mechanism for a perforating gun. An electronic firing head responds to sonic signals to fire the gun. U.S. Pat. No. 6,591,912 shows the use of gas pressure developed from shooting off a perforating gun to actuate a release mechanism. U.S. Pat. No. 5,967,231 releases a wiper plug and delivers a signal that the plug has been released. US publication 2008/0041597 combines in a single assembly a release feature and a data gathering and transmission feature using a variety of telemetry techniques such as pressure pulses, acoustic or electromagnetic signals as described in paragraph 63. 
     The present invention operates a disconnect using preferably a pressure pulse signal that is processed at the disconnect. Upon receipt of the predetermined release signal a valve is operated to allow either annulus or tubing fluid pressure act against a piston on one of its ends with the opposite end preferably exposed to a low pressure or atmospheric chamber or tubing pressure. The piston movement breaks a shear pin and positions a recess opposite a locking dog to enable the separation of the two previously held components. Activation can come from the tubing or the annulus or both. The piston can be an annular sleeve or one or more rods. Piston movement can also be used in other applications to open or close a tubular wall port. Those skilled in the art will gain further insight into the present invention from a review of the detailed description of the preferred embodiment and the associated FIG. while recognizing that the full scope of the invention can be found in the appended claims. 
     SUMMARY OF THE INVENTION 
     A pressure pulse signal is processed and a valve is operated to allow tubing or annulus pressure to move a piston against an atmospheric or low pressure chamber. Movement of the piston triggers the release of the dogs that previously held two components together for a separation. Redundant release mechanisms that respond to discrete pressure pulse signals are provided for backup purposes. Alternative applications for opening or closing a tubular wall port or an inline valve such as during drill stem testing are envisioned. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The FIGURE is a split view with the connection intact on one side and separated on the other side. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The FIGURE illustrates an upper housing  10  having a connection thread  12 . Upper housing  10  has a lower end  14  at bottom sub  16  that has a plurality of openings or windows  18  through which extend retaining dogs  20 . The dogs  20  also extend into a groove  22  of housing  24  that has connection threads  26 . When the dogs  20  extend into groove  22  and are supported by surface  28  of piston  30  the housings  10  and  24  are secured to each other. Initially, a shear pin or pins  32  can also hold the housings  10  and  24  together. Pressure applied in passage  34  acts on the top of the piston  30  and that pressure is sealed with seals  36 ,  38 ,  40  and  42 . Seals  38  and  42  define a low pressure or atmospheric chamber  44  that aids in movement of piston  30  when triggered to move. 
     Piston  30  has a recess  46  designed to accept the dogs  20  when moved into alignment with the dogs  20  as shown in the bottom of the FIG. Such movement of the piston  30  will initially break the shear pin or pins  32 . Note that the lower end  48  is exposed to tubing pressure in the passage  50  but can alternatively be directed into another low pressure or atmospheric chamber by a reconfiguration of the bottom sub  16 . Housing  10  has a lower extension  52  to define the cavity for the piston  30 . Although piston  30  is illustrated as a sleeve from its top near seal  38  to its lower end at the connection for the shear pin  32  other structures for the piston  30  are envisioned. The upper end above groove  46  can be one or more rods that are actuated in tandem or independently with redundant systems as will be explained below. Each rod can have a discrete port to within or outside the housings and the same or different signals to the processor  56  can allow pressure to reach discrete rods to create a release using tubing or annulus pressure. While release of the dogs  20  is illustrated with axial movement of the piston  30  other movements are envisioned that can remove support for the dogs  20  by moving surface  28  away from dogs  20 . Rotation of the piston to bring recess  46  in registry with dogs  20  is also contemplated as well as other movements that combine axial and rotational piston  30  movements. 
     Housing  10  has a port  54  that is preferably directed to the surrounding annulus for the communication of predetermined pulses of a particular magnitude and duration in a sequence that will be recognized by one or more battery operated processors referred to generally as  56  and located within a wall of the housing  10 . A communication port  58  is shown leading from the surrounding annular space to a valve  60 . Valve  60  operation is controlled by the processor  56 . While one valve  60  is illustrated there can be more such valves and they can direct fluid from the surrounding annulus or the tubing passage  50  to passage or passages  34  to drive a single annularly shaped piston  30  or a series of rod pistons against an annularly shaped lower end of the piston  30  that has the recess or recesses  46 . The processor  56  is capable of distinguishing several predetermined signals to drive different valves  60  either one at a time for alternative actuation of the piston  30  or to operate a plurality of valves  60  at the same time for an enhanced force applied to the piston  30  to effect a release of the dogs  20  so that housings  10  and  24  can separate. 
     The lower part of the FIG. shows the recess  46  in registry with dogs  20  that allows the dogs  20  to retract from groove  22  of housing  24  so that housing  10  can be removed with the tubing string connected at thread  12 . Groove  22  also serves as an attachment point for a fishing spear (not shown) that can engage the housing  24  if for any reason it needs to be fished out. 
     Valve  60  can be a sleeve that is released for movement by the processor  56  such that passage  34  is in communication with passage  58  as the sleeve moves against a low pressure or atmospheric chamber  62  as shown in the lower part of the FIG. where the separation has already occurred. Alternatively, valve  60  can be a ball or a plug valve or other designs suitable for on and off service. 
     Those skilled in the art will appreciate that what is illustrated is a disconnect that can be triggered with a signal in a variety of forms that can be recognized by a processor to then employ pressure in the annular space around the tool or in the tubing passage within the tool to get a piston moving to allow a connection to separate. There can be a single signal that is recognized to allow the separation or discrete signals so that alternative opportunities are available to trigger the release. One or more openings to annulus or tubing pressure can be provided that are opened to the same or different processed signals. The actuating piston can be shifted axially or rotated or it can undergo some combination of movements to undermine the dogs that hold the connection together. The transmitted signal can be a pressure pulse through annulus or tubing sides or it can be an acoustic signal through the tubular wall or other signal delivered using fiber-optic cable or electrical or magnetic fields to mention a few alternatives. Movement of the piston can be aided or completely driven by providing an opposed end of the piston configured to be exposed to a low pressure or atmospheric pressure chamber in the housing component in which it is disposed. Depending on the orientation of the inlet passage to the piston  30  the annulus pressure or the tubing pressure can also be increased from the surface to aid in the movement of the piston after the processor  56  opens one or more valves  60 . The same groove that was used to hold the components together with a dog or dogs can also after the separation be used to fish the lower component that remained in the wellbore after the component separation. The valve  60  can be retained by the processor against a pressure differential between port  58  coming from outside or inside said housings and chamber  62  until a release is needed. The processor can free the valve member, which can be an annular ring to move to expose passage  34  to tubing or annulus pressure or both depending on the configuration so that the dogs  20  get undermined by movement of piston or actuator  30  to release housing  10  from housing  24 . The housing components can be splined or otherwise prevented from relative rotation when held together with dogs  20 . 
     The illustrated preferred application for a disconnect can be adapted to open or close a tubular wall port or to open or close an inline valve such as a ball valve or another type for a safety or operational feature such as during a drill stem test. 
     The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.