Abstract:
A technique improves the ability to inject coiled tubing at a variety of wells. A telescopic, anti-buckling guide is designed to support the coiled tubing to prevent buckling under operating loads. The telescopic, anti-buckling guide also facilitates connection to a variety of well control stacks of different heights without requiring vertical movement of the coiled tubing injector and without the need for pressure containment members in the guide.

Description:
BACKGROUND 
       [0001]    Coiled tubing rigs rely on coiled tubing injectors to inject coiled tubing into a well. Generally, the bottom of the coiled tubing injector is mounted directly to a stripper assembly through which the coiled tubing moves prior to entering a well stack and the well. Attempts have been made to provide greater flexibility in the ability to connect a given coiled tubing injector to a variety of well stacks by using telescoping risers between the stripper assembly and the well stack. However, the use of telescoping risers incurs a high cost and a high level of active maintenance. Additionally, the telescoping risers are required to maintain wellbore pressure. 
       SUMMARY 
       [0002]    In general, the present invention provides a system and method for improving the ability to inject coiled tubing at a variety of wells. The system and method utilize a telescopic, anti-buckling guide through which coiled tubing is moved before entering the stripper assembly and ultimately entering the well. The telescopic, anti-buckling guide is designed to support the coiled tubing to prevent buckling under operating loads. Additionally, the telescopic, anti-buckling guide facilitates connection to a variety of well control stacks of different heights without requiring vertical movement of the coiled tubing injector and without the need for pressure containment members in the guide. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
           [0004]      FIG. 1  is a schematic front view of a telescopic, anti-buckling guide system, according to an embodiment of the present invention; 
           [0005]      FIG. 2  is a side view of the telescopic, anti-buckling guide, according to an embodiment of the present invention; 
           [0006]      FIG. 3  is an orthogonal view of a lower guide member of the telescopic, anti-buckling guide illustrated in  FIG. 2 , according to an embodiment of the present invention; 
           [0007]      FIG. 4  is an orthogonal view of an upper guide member of the telescopic, anti-buckling guide illustrated in  FIG. 2 , according to an embodiment of the present invention; and 
           [0008]      FIG. 5  is an exploded view of the telescopic, anti-buckling guide system, according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
         [0010]    The present invention relates to a system and methodology for facilitating the injection of coiled tubing into a well. A telescopic, anti-buckling guide enables deployment of a coiled tubing injector head onto a well control stack without requiring vertical movement of the injector head. The telescopic character of the guide also enables adjustment of the distance between the coiled tubing injector and the well control stack which allows the injector head to be used with well control stacks of different heights without requiring vertical movement of the injector head. The guide also supports the coiled tubing and prevents buckling of the coiled tubing between the coiled tubing injector and a stripper assembly positioned at the top of a well control stack. 
         [0011]    Generally, the telescopic, anti-buckling guide provides a conduit for directing the coiled tubing from the injector head without requiring pressure seals. All pressure containing equipment can be located within the well control stack which reduces the cost and simplifies the structure of the telescopic, anti-buckling guide. For example, the cost of manufacturing the guide is reduced, and there are no maintenance requirements that would otherwise be associated with pressure seals. By avoiding the need to contain pressure, the telescopic, anti-buckling guide also avoids the need for locks that would otherwise be necessary to prevent unwanted expansion of the guide when exposed to internal well pressure. 
         [0012]    One embodiment of a guide system  10  is illustrated in  FIG. 1  as positioned at a well site  12 . In this example, guide system  10  comprises a telescopic, anti-buckling guide  14  connected between a coiled tubing injector  16  and a well stack, such as well control stack  18 . In the embodiment illustrated, telescopic anti-buckling guide  14  is directly connected to a stripper assembly  20  positioned generally at the top of well control stack  18 . 
         [0013]    Well control stack  18  is positioned on a surface  22  above a well  24  having a wellbore  26 . Well control stack  18  comprises pressure control equipment  28  to control the internal well pressure within wellbore  26  and to prevent unwanted passage of well fluids through well control stack  18 . Pressure control equipment  28  may comprise one or more members that can form the desired pressure seals able to hold back the internal well pressure. For example, blowout preventers or other pressure seals can be used. In the embodiment illustrated, all pressure control and all pressure control equipment is located below telescopic, anti-buckling guide  14  in, for example, well control stack  18 . Accordingly, telescopic, anti-buckling guide  14  can be manufactured without pressure seals. 
         [0014]    Coiled tubing injector  16  is designed to deliver coiled tubing  30  (shown in dashed lines) into well  24 . Pressure control equipment  28  can be used to form a seal with the coiled tubing  30  to prevent passage of internal well pressure. Furthermore, telescopic, anti-buckling guide  14  is sized to support coiled tubing  30  and to prevent buckling of the coiled tubing between the coiled tubing injector  16  and the well control stack  18 , e.g. between coiled tubing injector  16  and stripper assembly  20 . Guide  14  supports coiled tubing  30  against buckling when exposed to operating loads. 
         [0015]    The telescopic capability enables guide  14  to be compressed or extended as necessary to enable the connection of stripper assembly  20  to a variety of well control stacks  18  of different heights without requiring vertical movement of coiled tubing injector  16 . When a coiled tubing injection operation is completed or the coiled tubing injector  16  is to be moved to another well stack, the stripper assembly  20  can simply be uncoupled from well control stack  18 . Once uncoupled, the stripper assembly  20  is lifted upwardly to compress telescopic, anti-buckling guide  14  so as to clear well control stack  18  without requiring vertical movement of coiled tubing injector  16 . The coiled tubing injector  16 , guide  14  and a stripper assembly  20  can then be moved to the next desired location. 
         [0016]    One embodiment of telescopic, anti-buckling guide  14  is illustrated in  FIG. 2 . In this embodiment, guide  14  comprises an upper guide  32  and a lower guide  34  that are telescopically engaged. In the example illustrated, upper guide  32  and lower guide  34  are interlocking, sliding cylindrical tubes that slide over one another. For example, lower guide  34  may be sized to slidably receive upper guide  32  therein. However, upper guide  32  can be sized to slidably receive lower guide  34  within its interior; or upper guide  32  and lower guide  34  may be provided with other interlocking, telescopic configurations. 
         [0017]    By way of example, lower guide  34  may comprise a body portion  36  that is tubular in shape and has a hollow interior  38  sized to slidably receive upper guide  32 . As also illustrated in  FIG. 3 , lower guide  34  may further comprise a mount  40  that is configured for connection with stripper assembly  20 . Mount  40  may be in the form of a mounting flange  42  that is attached to stripper assembly  20  by a suitable fastener mechanism, such as a threaded engagement, a plurality of threaded fasteners, one or more weldments, or a combination of mechanisms. Lower guide  34  further comprises an expanded housing  44  that may be located generally between mount  40  and body portion  36 . Expanded portion  44  comprises a window  46  positioned to provide access to a portion of stripper assembly  20  when stripper assembly  20  is engaged with telescopic, anti-buckling guide  14 . For example, window  46  can be used to provide access to stripper assembly retaining pins  48  (see  FIG. 2 ). Additionally, lower guide  34  may comprise other features, such as a side connector  50  that can be used to facilitate movement and positioning of lower guide  34  and/or telescopic, anti-buckling guide  14 . 
         [0018]    By way of further example, upper guide  32  may comprise a body portion  52 , as further illustrated in  FIG. 4 . In this embodiment, body portion  52  is generally tubular and includes a hollow interior  54 . Body portion  52  is sized so that its outside diameter fits within the inside diameter defined by hollow interior  38  of lower guide body portion  36 . Furthermore, hollow interior  54  is sized to support a coiled tubing  30  against buckling when coiled tubing  30  is moved through telescopic, anti-buckling guide  14 . Upper guide  32  may further comprise a connector  56  that is configured for connection with coiled tubing injector  16 . Connector  56  may comprise a flange  58  designed for connection to coiled tubing injector  16  by a suitable fastener mechanism, such as a threaded fastener end, a plurality of threaded fasteners, one or more weldments, or a combination of mechanisms. 
         [0019]    As illustrated in the expanded view of  FIG. 5 , body portion  52  of upper guide  32  is slidably engaged with body portion  36  of lower guide  34  to form the main body of telescopic, anti-buckling guide  14 . A retention ring or other mechanism  60  can be used to, for example, prevent inadvertent separation of upper guide  32  from lower guide  34  once combined. Additionally, a variety of guides, e.g. inserts,  62  can be used to selectively size the hollow interior of guide  14  according to the size of coiled tubing  30  that is to be delivered through telescopic, anti-buckling guide  14  and into well  24 . A connection end  64  of stripper assembly  20  is inserted into the interior of the expanded portion  44  and exposed via window  46 . In many operations, stripper assembly  20  is retained in engagement with telescopic, anti-buckling guide  14  during movement from one well stack to another. 
         [0020]    Depending on a variety of factors, including well stack size and style, environment, coiled tubing injector type, and well operation performed, the size and configuration of telescopic anti-buckling guide  14  may vary. The telescopic characteristics can be achieved with a variety of upper and lower guides that are coupled together for selective expansion and contraction. The internal diameters of cylindrical style guides can be adjusted to accommodate different coiled tubing sizes, and a variety of inserts or other mechanisms can be used to provide the desired guidance of coiled tubing into well control stack  18  and well  24 . Furthermore, the telescopic, anti-buckling guide  14  can be designed with ends configured for engagement with a variety of coiled tubing injectors and stripper assemblies. 
         [0021]    Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.