Abstract:
The present invention provides for an apparatus and method to deploy a completion assembly into a well while maintaining the well in an underbalanced condition.

Description:
[0001]     This application claims the benefit of U.S. Provisional Application 60/536,083 filed on Jan. 13, 2004 and U.S. Provisional Application 60/521,640 filed on Jun. 9, 2004. 
     
    
     BACKGROUND  
       [0002]     1. Field of Invention  
         [0003]     The present invention pertains to placing a completion assembly in a well, and particularly to placing a completion assembly in a well while keeping the well in an underbalanced condition.  
         [0004]     2. Related Art  
         [0005]     It is often desirable to place completion equipment such as a sand screen, for example, in a well without exceeding formation pressures. Exceeding formation pressures can damage the formation, disrupt a mud cake barrier, or otherwise inhibit production of well fluids. Limiting the wellbore pressure to be equal to or less than the formation pressure is known as maintaining an underbalanced condition in the well. Placing a completion assembly in a well while holding the well in an underbalanced condition can be hazardous because wellbore fluids will naturally flow from a region of high pressure to a region of lower pressure, including the surface. That can lead to uncontrolled production, known in the art as a blowout.  
       SUMMARY  
       [0006]     The present invention provides for an apparatus and method to deploy a completion assembly into a well while maintaining the well in an underbalanced condition.  
         [0007]     Advantages and other features of the invention will become apparent from the following description, drawings, and claims. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]      FIG. 1  shows a schematic view of a completion assembly constructed in accordance with the present invention.  
         [0009]      FIG. 2  shows a schematic view of a representative well (prior art) in which the completion assembly of  FIG. 1  can be run.  
         [0010]      FIGS. 3, 4 , and  5  show schematic views illustrating different steps in a method performed in accordance with the present invention.  
         [0011]      FIGS. 6 through 15  show schematic views illustrating different steps in a method performed in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]     Referring to  FIG. 1 , a completion assembly  10  comprising a liner hangar  12 , a sand control device  14 , a crossover  16 , an overshot  18 , and a bridge plug  20  is shown disposed in a casing  22  and an open well bore  24  in a well  26 .  
         [0013]     Liner hangar  12  is used to secure assembly  10  to casing  22  and to form a seal to prevent fluid flow between hangar  12  and casing  22 . Sand control device  14  can be a slotted liner, a wire-wrapped screen, a mesh-covered perforated base pipe, or other filtering device used to exclude fines or other particulates from a production stream.  FIG. 1  shows sand control device  14  attached to and suspended from hangar  12 .  
         [0014]     Crossover  16  is shown mounted between the lower end of sand control device  14  and the upper end of overshot  18 .  
         [0015]     Overshot  18  mounts to the lower end of crossover  16  and has a release mechanism designed to release bridge plug  20  from a set position. Overshot  18  engages bridge plug  20  when run sufficiently far into well  26 , as described further below.  
         [0016]     Bridge plug  20  can be, for example, a wireline-set retrievable bridge plug, a mechanically-set retrievable bridge plug, or an inflatable bridge plug, however any plugging device suitable to suspend production of well fluids from below plug  20  may be used. A double flapper check valve (not shown), a pump out plug (not shown), a plug catcher (not shown), a circulating nozzle (not shown), or other component may be included as part of bridge plug  20  if an application requires such components. Bridge plug  20  has a release mechanism that, when engaged by overshot  18 , causes the slips (or inflation bladder) securing bridge plug  20  to casing  22  to retract, thereby freeing bridge plug  20 .  
         [0017]      FIG. 2  shows a representative existing well  26  in which the present invention has application. Production in well  26  is impeded because of, for example, infill (not shown). Because of the poor flow, production has been suspended and well  26  plugged with a composite plug  28 . To refurbish well  26  in accordance with the present invention, composite plug  28  is removed, for example, by drilling, as shown in  FIG. 3 . The well is blown dry and an underbalancing fluid such as nitrogen-foamed water is injected. Thus, well  26  is held in an underbalanced condition.  
         [0018]     Drilling proceeds until the bottom of well bore  24  is reached, as shown in  FIG. 4 . Well  26  is circulated to remove the drilled debris and clean out well bore  24 . The drilling assembly is then removed and, if desired, an underreaming tool can be run in and well bore  24  underreamed. Drilling debris is again circulated out of well  26  to leave well bore  24  clean.  
         [0019]     Bridge plug  20  is run into well  26  on coiled tubing  30  and set against casing  22 , as shown in  FIG. 5 . That seals off well bore  24  and holds well  26  in an underbalanced state. Pressure above bridge plug  20  is bled off and coiled tubing  30  is removed from well  26 .  
         [0020]     Completion assembly  10  can be assembled by attaching overshot  18  to the lower end of crossover  16 , which is in turn connected to a joint of sand screen  14 . As many joints of sand screen  14  as are necessary can be joined to form the length necessary for well  26 . This can be done as a single operation because the assembly is not done in a lubricator of limited length. The operator has the entire upper portion of well  26 , that is, the portion above bridge plug  20 , in which to assemble completion assembly  10 . When sand screen  14  is of sufficient length, tubing hangar  12  is attached to the upper end of sand screen  14  and the entire assembly  10  is run into well  26  using, for example, coiled tubing  30 .  
         [0021]     Upon encountering bridge plug  20 , overshot  18  engages bridge plug  20  and the release mechanism in overshot  18  works in conjunction with the mating release mechanism in bridge plug  20  to release bridge plug  20  from casing  22 , as is well known in the art. Bridge plug  20  attaches to overshot  18  upon engagement by overshot  18  and is moved to the bottom of well bore  24 . Upon reaching the desired depth, liner hangar  12  is set to fix it to casing  22 . Once liner hangar  12  is set, coiled tubing  30  can be removed and well  26  is ready for further completion operations such as a gravel pack, or to be placed back on production.  
         [0022]     Alternatively, referring to  FIG. 6 , a work assembly  110  comprises a drill bit  112 , a mud motor  114 , and a coiled tubing  116 . The assembly  110  is shown disposed in a well  118  having a casing  120  in an upper portion of well  118  and an open well bore  122  in a lower portion of well  118 . Work assembly  110  is used to clean out well  118  by removing fill. Once the fill is circulated out of well  118 , work assembly  110  is removed.  
         [0023]      FIG. 7  shows a plugging device  124  being run into well  118 . Plugging device  124  is designed to temporarily suspend or block production from producing zones below plugging device  124 . As stated above, various types of plugging devices  124  can be used. For example, plugging device  124  may be a retrievable plug set mechanically or by wireline, or an inflatable bridge plug run on coiled tubing  116 . In some configurations a double flapper check valve, a pump out plug, a plug catcher, and a circulating nozzle may be run as part of well plugging device  124 . If a particular application so requires, additional components could be run as part of plugging device  124  as well.  
         [0024]     Once plugging device  124  is run in to its desired depth in well  118 , it is set or actuated to isolate the portion of well  118  above plugging device  124  from that below plugging device  124 . A pressure test can be performed to insure pressure integrity of plugging device  124 . The setting tool can be released from plugging device  124  and removed along with coiled tubing  116 , as shown in  FIG. 8 .  
         [0025]      FIG. 9  shows a liner assembly  126  comprising an overshot  128 , a screen  130 , blank pipe  132 , a liner hangar  134 , an inner string  136 , and a liner hangar setting tool  138 . Liner assembly  126  can be as long as necessary and assembled while well  118  is maintained in an underbalanced condition by virtue of plugging device  124 . Overshot  128  is releasably attached to inner string  136 , for example, by shear pins. Inner string  136  extends from liner hangar  134  to overshot  128 . Liner assembly  126  is run into well  118  on coiled tubing  116  such that overshot  128  joins plugging device  124 , as shown in  FIG. 10 . Inner string  136  allows for fluid communication between coiled tubing  116  and plugging device  124 . Plugging device  124  can then be deactivated (see  FIG. 11 ).  
         [0026]     Liner assembly  126  can be further lowered into well  118  while any residual fill is circulated out of the hole, as shown in  FIG. 12 . When plugging device  124  reaches the total depth of well  118 , weight can slowly be applied to release overshot  128  from inner string  136 , for example, when the shear pins shear (see  FIG. 13 ). That allows overshot  128  and plugging device  124  to retract within screen  130  as liner assembly  126  is lowered to the total depth of well  118  (see  FIG. 14 ).  
         [0027]     Liner hangar  134  can then be set using conventional means such as dropping a ball to seat in liner hangar setting tool  138 . Once liner hangar  134  is set, liner hangar setting tool  138 , along with overshot  128 , inner string  136 , and plugging device  124  can be released and removed from well  118  by coiled tubing  116 , as shown in  FIG. 15 .  
         [0028]     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.