Abstract:
A gravel pack screen assembly has one or more hollow flight augers that a continuous or segmented with multiple upwardly oriented gravel entrances and multiple downwardly oriented gravel exits. The gravel passes through the auger and around any bridge. The auger helps advance the screen into position as well as to centralize it during gravel deposition. The auger protects the screen during run in as well as the internal passages that pass through it due to its structural rigidity. An alternative embodiment features spirally wound tubes with staggered exit locations for better distribution of the gravel.

Description:
PRIORITY INFORMATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/424,401, filed on Nov. 7, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The field of this invention relates to alternate paths for gravel during downhole gravel packing operations and more particularly to spirally shaped paths in the form of a surrounding hollow auger for a gravel pack screen assembly. Spirally wrapped shunt tubes are further contemplated.  
         BACKGROUND OF THE INVENTION  
         [0003]    A common problem when gravel packing is that the gravel forms bridges and leaves gaping areas uncovered as the gravel that is subsequently delivered piles up behind the bridge or blockage. Another problem is the difficulty in delivering screen into long horizontal runs because of the limited weight available to advance the screen and the possibility that it may simply buckle in the wellbore and cease to further advance. Yet another issue is the need to centralize the screen as the gravel is delivered for deposition all around it. Another concern is damage to the screen assembly during run in. Gravel screens have been provided in the past with surrounding shrouds but the delivery to the desired location could still cause damage to the shroud and the underlying screen. Bridge formation is always a concern. Annular bridge formation can be aggravated by zones of low flow rates leading to deposition of undue amounts of gravel in concentrations in undesirable locations leading to a bridge ultimately forming.  
           [0004]    In the past, a solid auger on a gravel pack screen has been used to insert the screen into the wellbore after the gravel has been earlier deposited. The auger helps to advance the screen into the borehole location that is already pre-charged with gravel. This method is illustrated in U.S. Pat. No. 5,036,920. Augers have been used on perforating guns to get them out after they are fired, as illustrated in U.S. Patent Re. 34,451.  
           [0005]    Alternate paths for the gravel comprising longitudinally oriented narrow passages disposed parallel to each other have been used to try to deliver gravel beyond a sand bridge. Some examples are U.S. Pat. Nos.: 6,298,916; 5,161,618; 6,059,032; 5,842,516; 4,945,991; 5,161,613; 5,113,935; 5,419,394; 5,417,284; 5,435,391; 5,560,427; 5,848,645; 5,622,224; 5,588,487; 5,890,533; 6,227,303; 6,220,345; 5,476,143; 5,341.880; 5,515,915; 5,082,052; 6,409,219; 5,390,966; and 5,868,200. Also of interest is the Halliburton multiple path screen system called SurePac. Some of these references have shunt tubes that are internal and others feature external tubes. These designs address the specific problem of bridging but ignore some of the other issues such as protection of the screen, advancement of the screen into position and the potential damage to the shunt tubes when mounted externally.  
           [0006]    The present invention addresses in a cohesive design several parameters. The hollow flight or flights of augers are structurally rigid to allow rotation to advance the screen. The passages in the flights are also protected by the rigidity of the auger design. The screen is better protected during run in. The auger allows gravel to enter and exit in multiple locations to allow gravel to bypass bridges. The spiral flow pattern in the interior and along the exterior of the auger is more turbulent due to the centrifugal force from going around the screen, making it less likely that gravel will deposit within the auger or prematurely in the annulus. The auger centralizes prior to gravel delivery.  
           [0007]    The other advantages are offered by an alternative embodiment that features spirally wound shunt tubes. These tubes are open at discrete locations for escape of gravel. The spiral layout improves gravel distribution upon exit from the tubes.  
           [0008]    These and other advantages of the present invention will be more apparent 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  
         [0009]    A gravel pack screen assembly has one or more hollow flight augers that a continuous or segmented with multiple upwardly oriented gravel entrances and multiple downwardly oriented gravel exits. The gravel passes through the auger and around any bridge. The auger helps advance the screen into position as well as to centralize it during gravel deposition. The auger protects the screen during run in as well as the internal passages that pass through it due to its structural rigidity. An alternative embodiment features spirally wound tubes with staggered exit locations for better distribution of the gravel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an exterior view of a screen assembly with a single flight hollow auger mounted to it showing the flow of gravel through the hollow flight;  
         [0011]    [0011]FIG. 2 is a section view of an alternative embodiment showing the spirally wrapped tubes;  
         [0012]    [0012]FIG. 3 is the view along lines  3 - 3  of FIG. 2;  
         [0013]    [0013]FIG. 4 shows an outer view of the jacket mounted over joints in the screen assembly; and  
         [0014]    [0014]FIG. 5 is the view along lines  5 - 5  of FIG. 4. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Referring to FIG. 1 the screen assembly  10  can be made up of multiple sections such as  12  and  14  that are connected by a coupling  16 . The actual screen, shown by dashed line  18  is below an outer protective jacket  20 . The protective jacket  20  stops short of each coupling  16  so that the proper length of the assembly  10  can be put together for a given application. The auger  22  is hollow and has an inlet  24  near the top where gravel, represented by arrow  26  can enter. There is a plurality of exits  28  on the auger underside for the gravel  26  to exit. The auger  22  may be made continuous over the couplings  16  such as by installing the segments that pass the coupling  16  after it is assembled. Alternatively, the auger  22  can stop before some or all of the couplings  16  and resume on the protective jacket  20  immediately below the coupling  16 . In this manner there can be multiple inlets  24  where each section of auger  22  begins. Additionally or alternatively, there can be additional inlets on the uphole side  30  of auger  22  for the purpose of letting in gravel  26  at multiple points along a length of continuous auger  22 .  
         [0016]    The pitch and/or diameter of auger  22  can be constant or variable. There can be a single auger  22  or nested augers. Auger  22  may be made of the same metallic material as the protective jacket  20  and attached by a variety of techniques, although welding is preferred. Alternatively the auger  22  can be non-metallic as can be the protective jacket  20 . They can be made integrally or the auger  22  can be mounted separately to jacket  20 . The inlets  24  and outlets  28  can have a variety of shapes and sizes guided by the need to maintain the structural integrity of the auger  22  during conditions of its rotation to advance the screen assembly  10  into position before the gravel  26  is deposited in a known manner. All or less than all of the length of the screen assembly  10  can be covered with the hollow auger  22 . Periodically, short cut passages  32  can extend longitudinally from the underside of auger  22  to the uphole side  30  immediately below as yet another path for the gravel  26  to take if auger  22  starts to plug internally.  
         [0017]    Those skilled in the art will appreciate that the presence of auger  22  creates turbulence around the screen assembly  10  so as to make it less likely in the first place that sand bridges will form. The presence of the hollow auger  22  allows the gravel alternate paths to enter at the start or along the way on each auger or segment thereof and to exit on the downhole side of the auger or its segments anywhere along the length where an outlet is provided and at all lower open ends of hollow auger  22 . The auger  22  acts as a centralizer on the trip downhole. It also protects the screen assembly  10  from mechanical damage during run in. The auger  22  also helps to advance the screen assembly into proper position. This can be useful in a nearly horizontal run where the ability to push the screen assembly  10  forward without buckling it may be severely limited. This problem can occur in regions of shale instability where contact by water based fluids makes the shale unconsolidated so that it can collapse into the wellbore. If this happens the alternate paths through the auger  22  allow gravel to also bypass the region of shale collapse. The auger  22  can be assembled to the protective jacket  20  such as by welding and then the assembly can be rolled over the screen material and secured to the base pipe underlying the screen material. Removal of the screen assembly  10 , should that become necessary, is made easier by just applying an uphole force to the screen assembly  10 . The auger  22  will put the screen assembly into rotation and the pitch of the auger  22  will drive the auger out of the gravel.  
         [0018]    Accordingly, the auger  22  in its various embodiments described above addresses several potential problems involved in running gravel pack screens. The alternate paths create internal turbulence and centrifugal force that helps to minimize blockages internally in the flow paths. Externally, turbulence is also created by auger  22  to help fight sand bridging.  
         [0019]    [0019]FIG. 2 illustrates an alternative embodiment of the present invention. The screen  30  is assembled in sections and connected by joints  32 . Illustratively, four shunt tubes  34 ,  36 ,  38 , and  40  as best seen in the section view of FIG. 5 are disposed on the outside of screen  30 . In the preferred embodiment, the shunt tubes  34 ,  36 ,  38 , and  40  are equally spaced and spirally wound on the same pitch over the length of the screen assembly. Mounted over each joint  32  is a jacket  42 . As shown in FIG. 2, at least one of the shunt tubes  34 ,  36 ,  38 , and  40  has an exit  44  under jacket  42 . It also has an entrance  46  under jacket  42 . Flow coming downhole through tube  34  exits and goes in three directions represented by arrows  46 ,  48 , and  50 . Arrow  46  shows the gravel exiting above the jacket  42 , arrow  48  shows the gravel exiting below the jacket  42  and arrow  50  shows the gravel re-entering tube  34  under jacket  42 . Jacket  42  provides a jumper path for each other tube such as tubes  36  and  40  shown in FIG. 2. Jacket  42  can have a discrete path for an individual tube or it can provide a common manifold so that flow from a variety of tubes can mix within the jacket and exit a different tube from the tube that a particular flow entered the jacket  42 . At the next joint  52 , a different tube  38  is open for flow in three possible directions as indicated by arrows  54 ,  56 , and  58 . In between joints  32  and  52  at least one tube such as  40  has open ends  60  and  62  to allow flow out from under open coupling  64 . Flow can go out above coupling  64  as indicated by arrows  66  and out below, as indicated by arrows  68 . Between joints such as  32  and  52  a single tube may have one or more couplings  64 . Alternatively more than one tube can have one or more couplings  64  between typical joints such as  32  and  52 . As another variation, more than one of tubes  34 ,  36 ,  38 , and  40  can have open ends under the jacket  42 . The jacket  42  can be made in pieces  70  and  72  and held together by one or more bolts  74 .  
         [0020]    Those skilled in the art will appreciate that the spiral winding will increase the overall length of the shunt tubes  34 ,  36 ,  38 , and  40  as the wrap around the screen  30  but the fluid velocity will be higher as the spiral flow path will aid distribution of the gravel as it emerges from any openings in the shunt tubes  34 ,  36 ,  38 , and  40 . The spiral pattern will also better protect the screen  30  on insertion and help to better center it when it reaches the desired location. Those skilled in the art will also appreciate that the number of tubes can be varied as well as their initial spacing and pitch. The diameter of an individual tube can be varied along its length. In the preferred embodiment if there are four tubes equally spaced and spirally wound on the same pitch, each tube will have breaks over a fourth of the length of the screens  30  with no or minimal zone overlap. Alternatively, jacket  42  can be eliminated in favor of a jumper tube at a joint such as  32  for those tubes that have no openings at that location while the tubes with openings can have a coupling such as  64  at a joint such as  32 .  
         [0021]    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: