Abstract:
A plug for a seal bore in a packer mandrel has a shiftable annular member that can selectively open bypass ports to facilitate latching and then be shifted as part of a release from the plug by a running tool to close the bypass passage that go around a frangible barrier that will later be broken by impact force. The annular member has minimal structure internally to allow attachment of the running tool. The annular member drillout proceeds quickly with minimal cuttings and the frangible member is broken by impact. On an assembly with multiple packers getting plugs a trip is saved as a plug is delivered into a lower packer with a string supporting the packer above. The plug is set in the lower packer allowing release of the running string for subsequent placement and setting of the next packer in the same trip.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is completions and more particularly when portions of a zone are perforated, flow tested and isolated in sequence and thereafter the isolated zones are to be opened to produce through packers previously used for zone isolation. 
       BACKGROUND OF THE INVENTION 
       [0002]    In some completions after the well is drilled to the zone of interest, a packer is set on a string that conveys a perforating gun and a lowermost portion of the zone of interest is perforated. The gun is removed and a plug is delivered into the first packer to isolate the lower zone after an initial flow test is conducted. The lowermost region is now isolated and the process repeats in an uphole direction as many times as is necessary. The plug that can be used is a Model F Latching Packer Plug sold by Baker Hughes Incorporated. This plug has a selectively open bypass to facilitate mechanical latching when advancing the plug against formation pressure. The bypass prevents a potential liquid lock that would otherwise impede advancement of the plug until it latched to the packer bore with the seal assembly properly positioned in a polished bore normally extending below the packer mandrel. This plug has an unloader sub that can be selected for a bypass flow configuration or the bypass can be closed with a j-slot which also allows removal of the running string so that the packer is in effect a bridge plug. At a later time this plug will need to be removed to produce from the zone that is below it. If there are no obstructions above plug, its removal simply requires acquiring the j-pin mandrel at the top with a retrieval tool and pulling the plug out of the packer mandrel. If there are other packers above the packer in question with a Model F Plug in it then the plug has to be removed by other means such as drilling it out. Because the Model F is built to accomplish many objectives such as operating as a bypass device and holding differential pressure, trying to mill out such a plug can generate lots of cuttings that then have to be captured with wellbore cleanup tools such as the VACS Tool offered by Baker Hughes. The cuttings that do not get captured can migrate to undesired locations to make subsequent operations in the wellbore more problematic. Beyond that the Model F Plug is placed in a respective packer in a separate trip after the fired guns are removed and the initial flow test is conducted. As previously stated then another packer is run in and set with a string having a perforating gun and the process repeats. 
         [0003]    What is need is a plug design that contemplates drillout so that cuttings are minimized while a drift diameter that is made available is maximized while the drillout time is minimized. What is also needed is a way to save trips when dividing a zone into segments that each is flow tested and plugged and later produced necessitating plug removal when there are obstructions above. What is provided is a bottom hole assembly that can deliver and latch a suitable plug to a lower packer while delivering the packer above. In that instance the plug is set in the lower packer and the running tool releases from the set plug to allow the string to be manipulated to position and then set the packer above. This saves a trip in the hole compared to comparable systems used before. Those skilled in the art will more readily appreciate these and other aspects of the invention from a review of the detailed description and the associated figures while appreciating that the full scope of the invention is to be determined from the appended claims. 
       SUMMARY OF THE INVENTION 
       [0004]    A plug for a seal bore in a packer mandrel has a shiftable annular member that can selectively open bypass ports to facilitate latching and then be shifted as part of a release from the plug by a running tool to close the bypass passage that go around a frangible barrier that will later be broken by impact force. The annular member has minimal structure internally to allow attachment of the running tool. The annular member drillout proceeds quickly with minimal cuttings and the frangible member is broken by impact. On an assembly with multiple packers getting plugs a trip is saved as a plug is delivered into a lower packer with a string supporting the packer above. The plug is set in the lower packer allowing release of the running string for subsequent placement and setting of the next packer in the same trip. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a section view of a known packer having a passage therethrough and a seal bore at a lower end of the mandrel; 
           [0006]      FIG. 2  is a schematic illustration of possible liquid lock when installing a prior design plug into a packer open to formation pressure; 
           [0007]      FIG. 3A  is a schematic illustration of the running tool attached to the shiftable plug for run in with the bypass passages open; 
           [0008]      FIG. 3B  is the view of  FIG. 3A  where the running tool has shifted the bypass plug to close the bypass ports while releasing from the shifted plug; 
           [0009]      FIG. 4A  is a view of the plug in the run in configuration; 
           [0010]      FIG. 4B  is the view of  FIG. 4A  with the plug latched and the bypass passages closed; 
           [0011]      FIG. 5  shows a first packer set and the zone below it being perforated; 
           [0012]      FIG. 6  is the view of  FIG. 5  with a plug delivered into the lower packer as the next packer is also run into the well; 
           [0013]      FIG. 7  is the view of  FIG. 6  with the running tool released from the latched lower plug and the second packer repositioned for setting; 
           [0014]      FIG. 8  shows a perforating gun run through the second packer and set off; 
           [0015]      FIG. 9  shows a plug for the second packer delivered in the same trip as a third packer; 
           [0016]      FIG. 10  shows the second packer plugged and the running string repositioned for setting the third packer; 
           [0017]      FIG. 11  shows a perforating gun run through the third packer and shot; 
           [0018]      FIG. 12  shows the plug from the second packer is removed allowing tandem production from the top two intervals together; 
           [0019]      FIG. 13  shows the plug removed from the bottom packer allowing tandem production from the three illustrated intervals. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    By way of background,  FIG. 1  represents a known packer  10  having a mandrel  12  and a polished bore extension  14 . The packer  10  has a sealing element  16  flanked by upper slips  18  and lower slips  20 . An anchor latch  22  is used to retain a plug  24  as shown in  FIG. 2 . The plug  24  has a through passage  26  that is blocked by a barrier  28 . Seal assembly  30  lands in polished bore extension  14  and latch mechanism  32  lands and latches to anchor latch  22 . When flow is desired at a later time through passage  26  the barrier  28  is removed by drilling or other means. The issue with this design is when trying to latch the plug against formation pressure. Because the passage  26  is blocked by barrier  28  it will frequently require a great deal of force to essentially buck the formation pressure so that the plug  24  can sufficiently advance to allow it to latch. As previously discussed, the Baker Hughes Model F Packer Plug has an unloader feature that allows temporary bypassing of the passage barrier in the plug and then closing the bypass when a running tool is released from the plug. However, this tool is fairly complex and has a j-slot actuation mechanism and was not initially designed to be milled out in situation where there are uphole restrictions that prevent its normal removal with a fishing tool that grips a fishing neck at the tool upper end. Because of this trying to millout this plug will generate significant cuttings that need capture and take a great deal of time. 
         [0021]      FIGS. 3A and 3B  show a preferred way to provide a temporary bypass for plug latching while designing the components for rapid millout that provides a drift dimension at least as large as the mill doing the millout with minimal cuttings generation. The run in position is shown on  FIG. 3A  and  FIG. 4A  shows the entire plug  34  that has external seals  36  and an anchor latch  38  all of which operate as before when describing plug  24 . The difference is in movable plug  40  which has an annular or ring shape with spaced external seals  42  and  44  that are run in offset from bypass passage  46  to allow flow represented by arrow  48  to bypass the seal assembly  36  as the plug  34  is advanced into position to allow anchor latch  38  to anchor at  50  on the packer assembly  10 . The running tool  52  is illustrated very schematically and has a shearable member  54  attached to plug  40  at cross member  56 . Raising the running tool will raise the plug  40  until it hits shoulder  58  at which point the bypass passage  46  will be closed because seals  42  and  44  straddle its opening as shown in  FIG. 3B . Further pulling up will separate  54  and  54  so that the running tool  52  can be removed. The plug passage  60  is still plugged by a barrier  62  preferably one that can shatter on mechanical contact from an object such as a ceramic disc for example. Internally to the plug  40  is a web structure of struts, schematically illustrated as  63  extending from an inner wall  64  that are configured to allow retention to the running tool  52  until the plug  34  is latched to the packer  10 . Opening  66  is not to scale and is preferably just smaller than the passage  60  to allow for the creation of the shoulder  58 . As a result when it is time to produce through a packer  10  plugged with plug  34 , a mill that is not shown is advanced through opening  66  and simply mills the very open web structure  63 . On impact of the mill with the barrier  62  the barrier shatters and the passage  60  is open for production flow or other purposes. 
         [0022]    Those skilled in the art will appreciate that the barrier  62  can be removed in other ways such as reactively or thermally for example. The open web structure of the equalizing plug  40  when used in tandem with the barrier  62  allows fast millout with minimal cuttings to capture and a procedure that allows the millout to happen in a short time. The internal components of the structure  63  can be composites, ceramics or other non-metallics or soft metals to facilitate rapid millout. 
         [0023]    Referring now to  FIGS. 5-13  another aspect of the invention will be illustrated that relates to the feature of saving a trip in the hole by delivering a plug for one packer in the same trip as the packer that is due to be set above. In  FIG. 1  a first packer  70  of a type previously described is run and set in position. A string  72  that supports a perforating gun  74  is then run through the packer  70 . When the gun  74  is properly located, the gun  74  is fired into the formation lower zone  76 .  FIG. 6  shows that the gun  74  is removed and what is next run in is a first plug  78  on a running tool  52  as previously described. The assembly is delivered on a running string  80  that also supports the second packer  82 . The assembly is advanced until the first plug  78  lands in first packer  70  with the plug  40  in the  FIG. 3A  position so that the first plug  78  can be latched as previously described. After latching, a pickup force is applied to the string  80  to get the plug  40  to move up as previously described and to release the running tool  52  from the first plug  78  also in the manner previously described. The string  80  can then be raised to locate second packer  82  at the proper spacing from first packer  70 . It is worth noting at this point that after setting the first packer  70  a flow test can be run on the lower zone  76  before the first plug  78  is installed in the first packer  70 . Also, a portion of the running tool  52  or all of it can remain with the second packer  82  after release from the first plug  78  as shown in  FIG. 7 . While illustrated schematically, those skilled in the art will appreciate that the running tool  52  has a passage therethrough to accommodate subsequent flow therethrough in either direction. 
         [0024]      FIG. 8  shows gun  84  below the second packer  82  perforating an intermediate zone  86  while supported on string  90 . First packer  70  is plugged with plug  78  and second packer  82  is set. As previously described for  FIGS. 5-7  the process is the same for  FIGS. 8-10  except the action is higher up in the wellbore. As shown in  FIG. 9  a string  88  delivers a third packer  92  and a second plug  94 . The assembly is advanced to land plug  94  in second packer  82  and latch to it. Again the running tool  52  shifts a plug  40  and there is a shear release from the second plug  94 . The string  88  is picked up to position the third packer  92  the desired distance from second packer  82  and the string  88  is removed. At this point in  FIG. 10  the first and second packers  70  and  82  are plugged and perforation of the upper zone  96  with gun  98  can take place. As stated before, a flow test can take place after each gun firing before the packer in question is plugged. In the case of  FIG. 11 , production from zone  96  can begin with plug  94  in place. As shown in  FIG. 12  the plug  94  has been milled out as previously described so that tandem production from zones  96  and  86  can take place. Subsequently, when plug  78  is drilled out production from all three zones including  76  can take place in tandem. 
         [0025]    Those skilled in the art will appreciate that the design of the packer plugs lends itself to rapid millout with minimal cuttings and in minimal time. A breakable barrier  62  in conjunction with a ring shaped plug  40  with an internal web of struts  63  or other structure that is fairly minimal allows this to happen. The structure is sufficient for attaching the running tool  52  and for a shear release that separates items  54  and  56 . In a completion with multiple zones or a sectioned single zone that takes multiple perforations separated with packers such as illustrated in  FIGS. 5-13  the ability to deliver the next packer when plugging a previous packer saves rig time. The prior Model F Baker Hughes plug is delivered in a separate trip and is principally designed to be removed when whole with a fishing tool. When there is an obstruction above and a plug such as the Model F has to be milled there are delays due to the need to remove significant portions of a metallic body not designed to be milled. The present system mounts the running tool for a plug to the lower end of a subsequent packer allowing the two to be delivered in tandem and then separated for subsequent setting of the packer after latching the plug that it formerly supported. The plug structure of having an open through passage closed with a removable member with bypass passage in the plug wall allows the use of a ring shaped valve associated with the running tool that is secured to the ring shaped plug with a minimal internal structure such that a pickup force slides the plug to close the bypass and shears for release. This leaves very little structure to mill out. A retaining shoulder at the plug top acts as a travel stop for the bypass plug as the running tool is shear released. The mill is sized to fit the opening at the plug top to provide the larger drift dimension for subsequent fluid flow or tools. The plug is designed to break on impact with the mill after the mill gets through the struts in the equalizer valve that previously held the running tool before the valve was shifted and the running tool shear released from the valve. The connection between the running tool actuator and the valve  40  can be a peripheral shear ring on the inside wall of the tubular valve such as an  1 -shaped ring one side of which comes out with the running tool actuator  54 ,  56  as opposed to leaving in any part of the actuator to later mill out. Doing the release this way only leaves a part of the shear ring inside the valve  40  so that there is virtually nothing to mill out and leaving the possibility open to breaking the barrier  62  with a sinker bar and without milling. 
         [0026]    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: