Abstract:
A gravel packing system featuring pressure actuated sliding sleeve valves mounted to an exterior annulus around a blanking pipe for screen sections is disclosed. An internal sliding sleeve valve is provided for subsequent closure of access through the screens. The presence of the annulus between the blanking pipe and the screen permits a backup access through perforating the blanking pipe while not damaging the screen. The sliding sleeve valves that are mounted internally and externally on the blanking pipe are removable apart from the screen section that already has gravel packed around it, if they fail to operate and need repair.

Description:
PRIORITY INFORMATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/370,911 on Apr. 8, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The field of this invention is downhole gravel packing systems with valves to isolate or allow access to various zones.  
         BACKGROUND OF THE INVENTION  
         [0003]    Typically in a gravel pack completion, a sump packer is set in the wellbore and the formation is perforated. The perforating gun is removed and a gravel packing assembly is installed. Screens are part of this assembly as is a crossover tool. The crossover tool is secured to a production packer. The production packer is set and the crossover is configured in a manner so as to allow pumping gravel through the production packer and into the annular space outside the screens. Return fluid, less the deposited gravel, goes through the production screen and through a valve in a blank pipe in the screen, back through the crossover and out the annular space above the set production packer. A closing tool on a wash pipe in a concentric string closes the sliding sleeve valve(s) when the crossover tool is pulled at the conclusion of the gravel packing operation. After the production string is run to the production packer, access to the formation involved using wireline or service string through the production packer to shift the internally mounted sliding sleeve(s) to gain access to the producing formation. This technique is illustrated in U.S. Pat. No. 5,609,204 assigned to OSCA Inc. of Lafayette, La.  
           [0004]    Subsequently, OSCA developed internally mounted pressure actuated circulating valves. These valves were integral to each section of screen assembly. Each screen section had a non-perforated base pipe having the sliding sleeve valve over a series of openings mounted on each screen section. For long screen intervals, numerous valves were required to be manipulated for full access to the producing zone. The close fit of these sliding sleeves to the screen and the integral construction did not allow for alternate access to the formation if such valves refused to open. Additionally, the integral construction with the screen sections precluded removal of such valves if they failed to operate without removing the entire screen assembly integral to such sliding sleeve valves. The presence of gravel exterior to the screens made it problematic to remove the screen assembly after deposition of the gravel.  
           [0005]    Other commercially available systems from Schlumberger and Weatherford used isolation ball valve systems as opposed to concentric isolation string hookups.  
           [0006]    The present invention seeks to address several limitations in the prior systems. It not only allows access to multiple zones with pressure actuated valves that open after pressure is applied and then removed, but it also allows through the use of a redundant valve, the ability to close off the access to a given layer should that be necessary, while maintaining the capability of re-accessing the zone at a later date. Should the main valves not open in response to application and removal of pressure, the annular gap to the screen allows for access through the blank pipe without damaging the screen. Additionally, by placing the access valves on a removable portion of the inner string, the invention permits removal of the access valve while leaving the screen and surrounding gravel pack in place. The use of this inner string, separate from the screen, also permits the use of systems which manipulate the entire concentric string itself in order to provide alternate flow paths during packing operations. These and other benefits of the invention will become clearer to those skilled in the art from a review of the description of the preferred embodiment and the claims, which appear below.  
         SUMMARY OF THE INVENTION  
         [0007]    A gravel packing system featuring pressure actuated sliding sleeve valves mounted to an exterior annulus around a blanking pipe for screen sections is disclosed. An internal sliding sleeve valve is provided for subsequent closure of access through the screens. The presence of the annulus between the blanking pipe and the screen permits a backup access through perforating the blanking pipe while not damaging the screen. The sliding sleeve valves that are mounted internally and externally on the blanking pipe are removable apart from the screen section that already has gravel packed around it, if they fail to operate and need repair. 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is an elevation view of the assembly in the run in position;  
         [0009]    [0009]FIG. 2 is the views of FIG. 1 shown in the circulate position;  
         [0010]    [0010]FIG. 3 is the views of FIG. 2 shown in the reverse position;  
         [0011]    [0011]FIG. 4 is the views of FIG. 3 shown in the pull out position;  
         [0012]    [0012]FIG. 5 is the views of FIG. 4 shown in the produce position;  
         [0013]    [0013]FIG. 6 is a split view of the pressure actuated sliding sleeve valve in the open and closed positions;  
         [0014]    [0014]FIG. 7 illustrates the way of getting alternate access through the blanking pipe if the sliding sleeve valve does not operate properly;  
         [0015]    FIGS.  8 - 10  illustrate the pull out feature of the concentric pipe assembly;  
         [0016]    FIGS.  11 - 14  are an alternate to FIGS.  1 - 5  allowing returns by raising the concentric pipe instead of using a sliding sleeve valve adjacent the screen that is closed when the wash pipe is removed with the run-in string.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    The gravel packing assembly of the present invention is illustrated in FIG. 1. A cased wellbore  10  is illustrated with a run in string  12  supporting a setting tool  14  to actuate the packer  16 . A crossover tool  18  is supported from the setting tool  14  and a wash pipe  20  is, in turn, supported off the crossover tool  18 . Down below is a sump packer  22  that has earlier been set in the well, generally before perforations  24  have been made, using a perforating gun of a type well known in the art.  
         [0018]    Suspended from the isolation packer  16  is a frac sleeve valve  26 , which is run in the open position. Below the sleeve valve  26  are tubulars or blank pipe  28  followed by a two-pin sub  30 . The external assembly connected to the two pin sub  30  comprises a tubular  32  followed by a breakaway coupling  34  (seen more easily in the enlarged view in FIG. 8). Shear pin  36  holds coupling  34  together and seal  38  prevents leakage, when the coupling  34  is intact. Below coupling  34  are additional tubulars  40  followed by a screen or screens  42  to a length as required by the depth of the formation producing through perforations  24 . The specific screen construction can vary and many known designs can be used. It is worthy of emphasis that there is an annular gap  44  between the screen  42  and the internal blanking pipe  46 . Continuing on below the screen  42  is a production pipe  48  that sealingly extends into a seal bore  50  in the sump packer  22 .  
         [0019]    Starting on the inside of the two-pin sub  30  is a valve assembly  52 , shown in larger detail in FIG. 6. The valve assembly  52  supports blanking pipe  46 , which has a sliding sleeve valve  54  in it and a seal assembly  56  at its lower end to sealingly engage the production pipe  48 . Sliding sleeve valve  54  is run in open and is subsequently closed when the wash pipe  20  is removed and closure mechanism  58  engages the sliding sleeve valve  54 , as shown in FIG. 4.  
         [0020]    Referring now to FIG. 6, the valve assembly  52  further comprises an internal sliding sleeve  60  having an opening or openings  62  that are in alignment with opening or openings  64  in the tubular  66 . Stated differently, for run in, openings  64  are not obstructed by sliding sleeve  60  but are obstructed by sliding sleeve  67  mounted externally to the tubular  66 . Sliding sleeve  67  has a pair of seals  76  and  78  that span openings  64  and are at unequal diameters such that pressure applied within tubular  66  tends to put an unbalanced force on sliding sleeve  67  moving it in a direction that breaks shear pin  70  while moving in a direction to compress spring  72 . When applied pressure is released, spring  72  moves sliding sleeve  67  until a snap ring  68  expands into groove  80  to lock the sliding sleeve  67  in the open position. Spring  72  is disposed in annular space  74 .  
         [0021]    [0021]FIG. 7 illustrates some back up techniques to deal with the issue of a particular sliding sleeve valve  67 , of which there are preferably one in each producing formation, fails to open with the applied pressure technique just described. The primary backup technique is to remove the wash pipe  20  and the cross-over  18  and run in a shifting tool  82  on slick line or equivalent  84  and operate sliding sleeve  54  back to the open position. It should be remembered that removing the wash pipe  20  causes the closure mechanism  58  to close sliding sleeve  54 . If that doesn&#39;t work a mini-perforating tool  86  run in on slick line or equivalent  84  can be positioned in blanking pipe  46 to penetrate only into the annular gap  44 , without risk of doing damage to tubulars  40  in a manner that would allow formation fluid to bypass the screens  42 .  
         [0022]    The operation of the assembly shown in FIGS.  1 - 5  will now be described. As previously stated, the sump packer  22  is run in and set in the cased wellbore  10 . Perforation in the known manner creates perforations  24 . A run in string  12  supports the assembly as previously described until it reaches the perforations  24 . The packer  16  is set. If needed a squeezing operation into perforations  24  can take place. Arrows  88  in FIG. 1 show the flow direction of treatment chemicals as going down the run in string  12  and through crossover  18  into annular space  90  and into the perforations  24 . The position of the crossover  18  in FIG. 1 prevents return flow uphole even though sliding sleeve valve  54  is open at this time.  
         [0023]    Going to FIG. 2, the circulation of gravel outside the screen  42  occurs as a result of a pick up of the cross-over  18  to allow fluid to flow through screen  42 , leaving the gravel behind in annular space  90 . Fluid continues through sliding sleeve valve  54  and down to the bottom of the wash pipe  20 , then up to the cross-over  18  and through it and into the annular space  92  above packer  16  and out to the surface, as shown by arrow  94 .  
         [0024]    When the gravel has been duly deposited, the cross-over  18  is picked up, as shown in FIG. 3, and flow into annular space  92  arrives from the surface to go through the cross-over  18  and back up the run in string  12 . This flow pattern, illustrated by arrows  96  allows the remaining gravel in the system to be flushed out to the surface.  
         [0025]    The next step, shown in FIG. 4, is to pull out the crossover tool  18  and the wash pipe  20 . As a result, the closure mechanism  58  closes sliding sleeve valve  54 . This movement of the crossover tool  18  allows a closure mechanism  98  mounted on it to close frac sliding sleeve valve  26 .  
         [0026]    At this point, shown in FIG. 5, production tubing  100  with a seal assembly  102  is tagged into the packer  16 . Pressure can be applied from the surface through the production tubing  100  and it will communicate to every closed valve assembly  52  in the wellbore. Each valve assembly  52  has a shear pin  70  and the various shear pins at different intervals can be set at different levels. Operating personnel, depending on the amount of pressure applied can open all or some of the valves  67 . As long as pressure is applied, shown as arrow  104  none of the valves  67  will actually be biased to open. This allows the pressure to be progressively raised to a level to break all shear pins  70  before the applied pressure can escape through opening of any of the sliding sleeve valves  67 . If the pressure is subsequently removed from the surface, production starts from the perforations  24  through the opened sliding sleeve valves  67  to the surface through the production tubing  100 , as indicated by arrow  106 .  
         [0027]    FIGS.  8 - 10  illustrate a feature that allows leaving the screens  42  in place while removing the valve assembly  52  with blanking pipe  46  and seal assembly  56  from sump packer  22 . A retrieving tool  108  is run in and engaged to packer  16  before packer  16  is released, as shown in FIG. 8. The detailed portion of FIG. 8 shows what happens after the packer  16  is released and an upward pull breaks shear pin  36  of breakaway coupling  34 . When coupling  34  comes apart, the retrieving tool  108  pulls out valve assembly  52 , blanking pipe  46 , sliding sleeve valve  54  and seal assembly  56 , as shown in FIG. 9. Subsequently a replacement assembly of the same components is run back into the cased wellbore  10  except that a packoff overshot  110  with a seal  112 , which replaces the seal  38  in the breakaway coupling  34  that used to be there, is sealingly connected to the remaining half of the breakaway coupling  34 . The ability to replace this assembly without pulling the screens is an advantage since after gravel packing, the screen  42  may be very difficult to dislodge.  
         [0028]    FIGS.  11 - 14  disclose essentially the same method as FIGS.  1 - 5  except that sliding sleeve valve  54  has been eliminated. The closure mechanism  58  on the wash pipe  20  now will have a different purpose. A telescoping joint  114  is in the retracted position for run in leaving a gap  116  between the seal assembly  56  and the sump packer  22 . In FIG. 11, the crossover  18  is in position to allow a squeeze job into the perforations  24  with no return path available. In FIG. 12, the crossover  18  has been raised allowing return flow through gap  116  as shown by arrows  118 . In this manner the gravel is deposited outside of screen  42 . FIG. 13 shows the crossover  18  raised to allow reversing out the gravel in the system, as previously described. FIG. 14 shows closure mechanism  58  engaging telescoping joint  116  to push it down. This motion also forces the seal assembly  56  down into sump packer  22  to sealingly close off gap  116 . Thereafter, the valve assembly  52  is operated in the manner previously described. The advantage of this variation is to address the concerns of some operators that sliding sleeve valve  54  will not fully close when the wash pipe  20  and its closure mechanism  58  are moved out of the cased wellbore  10 . Different solutions that provide for the requisite open and closed position of gap  116  than the preferred method described above are contemplated within the scope of the invention. The placement of the device that allows the relative movement can vary and the initial position can also be closed for run in so that gap  116  must be created with relative movement after run in.  
         [0029]    When desired to isolate any given formation, a tool can engage the respective sliding sleeve  60  to close off on or more formations through their respective access ports  64 .  
         [0030]    Those skilled in the art will now appreciate that the apparatus and methods described above provide for several advantages over prior systems for gravel packing. The sliding sleeve valves  67  that are disposed in annular gap  44  and on the outside of tubular  66  are far fewer in number for a producing zone than the prior system provided by OSCA and previously described. In fact a single sliding sleeve valve  67  can be used for a single producing zone regardless of its thickness as measured by the screen footage for screen  42  to produce that zone. The construction of the screens used in the OSCA system dictates a sliding sleeve valve for each screen section because of the nature of the flow through the screen. On the other hand, the present invention has a large annular area  44  inside the screen  42  to allow a single set of openings  64  to service an entire producing zone. The present invention allows for backup access through sliding sleeve valve  54  or through perforation of blanking pipe  46  without damage to tubulars  40  due to the presence of annular area  44 , as shown in FIG. 7. Alternatively, as shown in FIGS.  11 - 14  the gap  116  can be employed for production if the valve assembly  52  fails to open.  
         [0031]    he other option is to use the removability feature shown in FIGS.  8 - 10  to replace the valve assembly  52  which failed to open. By providing redundancy through sliding sleeve valves  67  on the outside of tubular  66  and  60  on the inside combined with using as little as one such assembly for a producing zone, there is a greater assurance that a particular zone can be subsequently isolated and re-opened by manipulation of sliding sleeve valve  60 . Additionally, the sliding sleeve valves  67  are in a protected location from circulating fluids in annular gap  44  so that they are more likely to reliably operate when needed.  
         [0032]    The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.