Abstract:
The present invention provides for a completion system that can be deployed in a single downhole trip, yet still achieve desired completion objectives.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/435,633, filed on Dec. 19, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of Invention  
           [0003]    The present invention pertains to systems used to complete subsurface wells, and particularly to systems designed to reduce the number of trips required in and out of the well to complete the well.  
           [0004]    2. Related Art  
           [0005]    Oil and gas wells are very expensive to drill and complete. A major cost factor is the expense of having a rig at the well site. Significant savings can be realized if the time a rig is needed is minimized.  
           [0006]    One way to minimize rig expense is to provide a system that combines various completion operations. Once such a system is placed in the well, the rig can be removed and alternative, cheaper means can be used to operate the completion system. For example, a tubing conveyed perforating assembly may be used in combination with a sand control assembly, or a sand control assembly may be run in with production tubing. Combining originally separate systems reduces the number of required runs.  
           [0007]    However, existing combinations still require more than one trip to achieve commonly desired completion objectives. Also, one or more capabilities may be compromised in existing tools. The present invention addresses those issues.  
         SUMMARY  
         [0008]    The present invention provides for a completion system that can be deployed in a single downhole trip, yet still achieve desired completion objectives.  
           [0009]    Advantages and other features of the invention will become apparent from the following description, drawings, and claims.  
       
    
    
     DESCRIPTION OF FIGURES  
       [0010]    [0010]FIG. 1 is a schematic view, with partial cut-away, of a true rigless one-trip system according to an embodiment of the invention.  
         [0011]    FIGS.  2 A- 2 L are schematic views, with partial cut-away, of the one-trip system of FIG. 1, showing various operational configurations. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring to FIG. 1, a true rigless one-trip system  10  has, in accordance with an embodiment of the invention, an upper completion assembly  12  and a lower completion assembly  14 .  
         [0013]    Lower completion assembly  14  comprises a selective nipple  16 , a shroud  18 , an inner string  20 , a no-go nipple  22 , a firing head  24 , a safety spacer  26 , and a perforating gun  28 . Lower completion  14  may also include a pupjoint  30 . Pupjoints  30  are generally short sections of tubing used to join elements and to attain a desired spacing between those elements.  
         [0014]    Selective nipple  16  has a profile that selectively accepts and releasably secures a device having a mating profile while rejecting (i.e., allows to pass) those devices having non-conforming profiles. Selective nipple  16  is used to properly position a device in a wellbore.  
         [0015]    Shroud  18  is a pipe that is joined to the lower end of selective nipple  16 , but does not engage or otherwise interfere with the profile of selective nipple  16 . Shroud  18  initially serves to house and protect inner string  20 , which is initially disposed in the tubular interior of shroud  18 , and serves as a structural element from which other elements can attach.  
         [0016]    Inner string  20  comprises a sand exclusion device or sand screen  32  and a lock  34 . Inner string  20  may also include pupjoints  30  or blank pipe (not shown) for spacing, and may optionally include a lower sliding sleeve  36 . Though generally referred to herein as sand screen  32 , sand exclusion devices  32  include, but are not limited to, wire-wrapped perforated or slotted base pipes, mesh-enclosed perforated or slotted base pipes, and expandable screens such as bi-stable expandable elements. Sand screen  32  has a mating profile to engage the profile of selective nipple  16  and is initially disposed in lower completion assembly  14  with the matching profiles engaged and locked. Lock  34  prevents the unintended release of sand screen  32  from selective nipple  16 .  
         [0017]    No-go nipple  22  attaches to and extends from the lower end of shroud  18 . It has an interior profile like that of selective nipple  16  such that a mating profile such as the profile of sand screen  32  can be secured therein. However, whereas selective nipple  16  will, when lock  34  is not engaged and when sufficient downward force is applied, allow a mating profile to move downward in the wellbore past the profile, no-go nipple  22  will not allow such a mating profile to pass. Thus, no-go nipple  22  establishes a lower limit to which a mating profile such as that of sand screen  32  can travel.  
         [0018]    Firing head  24  attaches to the lower end of no-go nipple  22 . Firing head  24  can be, for example, hydraulically or mechanically actuated and has an automatic gun release to automatically detach spacer  26  and gun  28  upon detonation of gun  28 . Spacer  26  connects at its upper end to the lower end of firing head  24 , and at its lower end to the upper end of gun  28 . It is notable that gun  28  is not attached to inner string  20 , and particularly not attached to sand screen  32 . Gun  28  can be, among other choices, a conventional perforating gun or a tubing conveyed perforator.  
         [0019]    Upper completion assembly  12  comprises some combination of the following elements. Not all elements will necessarily be present in every possible embodiment because the particular requirements of a particular well may not dictate it. Generally, upper completion  12  comprises all or some of the following structural elements. At or near the earth&#39;s surface, a valve  38  is located. Valve  38  is sometimes referred to as a Christmas tree. Immediately below valve  38  and sealingly set in production casing  40  is a tubing hanger  42 . Production casing  40  is a type of pipe that is generally cemented in place in the wellbore and, though an integral part of the well completion, is not for our purposes considered part of upper completion  12 . Production casing  40  extends from the earth&#39;s surface down into the wellbore past the formation that is the zone of interest  
         [0020]    Upper completion  12  further comprises production tubing  44 , sealingly hung from tubing hanger  42 . For safety, a surface-controlled subsurface safety valve  46  is placed inline with production tubing  44 . If artificial lift is needed, gas lift mandrels  48  with dummy valves can be included and are shown in FIG. 1 some distance below safety valve  46 . Other forms of artificial lift can be used such as electrical submersible pumps. Upper sliding sleeves  50  may optionally be included as part of upper completion  12 . A production packer  52  attaches inline with production tubing  44  and a gravel pack extension  54  having a gravel packing sliding sleeve  56  may optionally be attached below packer  52 . The lowermost element of upper completion  12  connects to the upper end of selective nipple  16 .  
         [0021]    In operation, one-trip system  10  is run into the well, as shown in FIG. 2A. Guns  28  are positioned adjacent the formation that is the zone of interest. Multiple guns  28  can be simultaneously run if there are multiple zones of interest. Once one-trip system  10  is in place, the rig can be removed from the well site. The remainder of the completion operations do not require the use of a rig, but instead use a continuous medium such as coiled tubing  58 , wireline, or slickline, for example, for mechanical manipulation or fluid transport from the earth&#39;s surface.  
         [0022]    To secure one-trip system  10  in place in the wellbore, packer  52  is actuated and tested for integrity (FIG. 2B). Packer  52  may be actuated by various means, such as hydraulically or mechanically, depending on the packer type. Gun  28  is then fired to perforate production casing  40 . Upon firing, gun  28  and spacer  26  disconnect from lower completion assembly  14  and drop to the bottom of the well (FIG. 2C). The well can be perforated in an overbalanced, balanced, or underbalanced condition. Various means can be used to fire gun  28  (e.g., hydraulic, mechanical, or electrical). If necessary, sand screen  32  may be open at its bottom end to allow passage of actuating devices.  
         [0023]    Well fluids can be controlled in different ways. The fluids can be forced back into the formation, or, if available, upper sliding sleeve  50  can be opened to allow circulation using the upper well annulus (FIGS. 2D and 2E). Coiled tubing  58  is then run into the well to engage sand screen  32 . Lock  34  is unlocked and sufficient downward force is applied to the coiled tubing  58  to displace sand screen  32  from selective nipple  16  (FIG. 2F). Sand screen  32  is moved until adjacent the perforations made by guns  28  (FIG. 2G). In that position the profile of sand screen  32  mates with the profile of no-go nipple  22 . Lock  34  is re-engaged to lock sand screen  32  in place and the coiled tubing  58  is pulled out of the hole (FIG. 2H).  
         [0024]    To perform the gravel pack operation, various options are available. In one option, a plug  60  is placed in selective nipple  16  and gravel pack sliding sleeve  56  is opened (FIG. 21). The sand control treatment fluid (“gravel”) can be pumped into the well using either the coiled tubing  58  or production tubing  44 . The gravel will exit through ports in extension  54  revealed by the opened sleeve  56 . Gravel travels down the annulus and fills the voids around sand screen  32  (FIG. 2J). When the gravel is packed (“screenout”), usually indicated by a sharp rise in pressure, pumping operations can be halted and the coiled tubing  58  can be used to remove any excess sand. As the coiled tubing  58  is pulled out of the hole, plug  60  is removed, gravel pack sliding sleeve  56  is closed (FIG. 2K), and the well is ready to be placed on production (FIG. 2L).  
         [0025]    In another option not requiring plug  60  but using lower sliding sleeve  36 , gravel is pumped through coiled tubing  58  to pack the space between shroud  18  and sand screen  32 , up to the level of lower sleeve  36 . Lower sliding sleeve  36  is opened using coiled tubing  58  and gravel is further pumped using either coiled tubing  58  or production tubing  44 . Gravel flows through ports exposed by lower sleeve  36  into the well annulus, packing the annulus in the region of shroud  18 . As before, once screenout occurs, pumping operations can be halted and the coiled tubing  58  can be used to remove any excess sand. As the coiled tubing  58  is pulled out of the hole, lower sliding sleeve  36  is closed, and the well is ready to be placed online. If artificial lift is necessary, gas lift mandrels  48  (or other lift means) can easily be actuated. Upper sleeve  56  can be opened to allow annular production, if desired.  
         [0026]    The operational steps described above vary slightly if sand exclusion device  32  is an expandable screen. Also, the lower portion of the well (“rathole”) needs to be extended slightly to accommodate sand accumulation during gravel pack operations. To operate with expandable screen  32 , one-trip system  10  is run in place, the rig is removed, packer  52  is set, and gun  28  is fired and dropped, all as before. Then, gravel or fracturing fluid is pumped through coiled tubing  58  or production tubing  44  through the open gravel pack sleeve  56  until screenout occurs. Coiled tubing  58  then latches onto expandable screen  32 , dislodges it from selective nipple  16 , and moves it downward until it locks into place in no-go nipple  22 . Coiled tubing  58  then engages an expander tool (not shown) and forces the expander tool downward, expanding expandable screen  32  radially outward so that expandable screen  32  is pressed against casing  40 . Upon reaching the bottom of expandable screen  32 , the expander tool can be disengaged from coiled tubing  58  and left in the lower end of expandable screen  32 . As coiled tubing  58  is retrieved from the well it can close sleeve  56 . Coiled tubing  58  can also open optional valves such as the valves in gas lift mandrel  48  to aid production.  
         [0027]    Though the embodiments described refer to sand control techniques, one-trip system  10  may also be used similarly for fracturing operations in which high pressure fluid is injected into the desired subsurface formation and proppants are used to keep the fractures open.  
         [0028]    In the preceding description, directional terms, such as “upper,” “lower,” “vertical,” “horizontal,” etc., may have been used for reasons of convenience to describe the one-trip system  10  and its associated components. However, such orientations are not needed to practice the invention, and thus, other orientations are possible in other embodiments of the invention.  
         [0029]    Although only a few example embodiments of the present invention are described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example 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. 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.