Abstract:
A reel configured to store an extended length of composite coiled tubing has a plurality of sections. In one embodiment, the reel has a drum and pair of detachable sidewalls. Each side wall includes a plurality of flanges. In another embodiment, the reel includes a radial splitline that defines substantially identical securably matable sections. Preferably, the reel can store at least 20,000 feet of composite coiled tubing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     1. Field of the Invention 
     The present invention relates to devices for handling coiled tubing for oil drilling operations. More particularly, the present invention relates to reels that have a capacity to hold extended lengths of coiled tubing. Still more particularly, the present invention relates to sectional transportable reels that have a capacity to hold extended lengths of coiled tubing. 
     2. Description of the Related Art 
     Coiled tubing, as currently deployed in the oilfield industry, generally includes small diameter cylindrical tubing made of metal or composites that have a relatively thin cross sectional thickness. Coiled tubing is typically much more flexible and much lighter than conventional drill string. These characteristics of coiled tubing have led to its use in various well operations. Coiled tubing is introduced into the oil or gas well bore through wellhead control equipment to perform various tasks during the exploration, drilling, production, and workover of a well. For example, coiled tubing is routinely utilized to inject gas or other fluids into the well bore, inflate or activate bridges and packers, transport well logging tools downhole, perform remedial cementing and clean-out operations in the bore, and to deliver drilling tools downhole. The flexible, lightweight nature of coiled tubing makes it particularly useful in deviated well bores. 
     Typically, coiled tubing is introduced into the oil or gas well bore through wellhead control equipment. A conventional handling system for coiled tubing can include a reel assembly, a gooseneck, and a tubing injector head. The reel assembly includes a rotating reel for storing coiled tubing, a cradle for supporting the reel, a drive motor, and a rotary coupling. During operation, the tubing injector head draws coiled tubing stored on the reel and injects the coiled tubing into a wellhead. The drive motor rotates the reel to pay out the coiled tubing and the gooseneck directs the coil tubing into the injector head. Often, fluids are pumped through the coiled tubing during operations. The rotary coupling provides an interface between the reel assembly and to a fluid line from a pump. Such arrangements and equipment for coiled tubing are well known in the art. 
     While prior art coiled tubing handling systems are satisfactory for coiled tubing made of metals such as steel, these systems do not accommodate the relatively long lengths of drill or working strings achievable with coiled tubing made of composites. Such extended lengths of composite coiled tubing strings are possible because composite coiled tubing is significantly lighter than steel coiled tubing. In fact, composite coiled tubing can be manufactured to have neutral buoyancy in drilling mud. With composite coiled tubing effectively floating in the drilling mud, downhole tools, such as tractors, need only overcome frictional forces in order to tow the composite coiled tubing through a well bore. This characteristic of composites markedly increases the operational reach of composite coiled tubing. Thus, composite coiled tubing can allow well completions to depths of 20,000 feet or more, depths previously not easily achieved by other methods. 
     Moreover, composites are highly resistant to fatigue failure caused by “bending events,” a mode of failure that is often a concern with steel coiled tubing. At least three bending events may occur before newly manufactured coiled tubing enters a well bore: unbending when the coiled tubing is first unspooled from the reel, bending when travelling over a gooseneck, and unbending upon entry into an injector. Such accumulation of bending events can seriously undermine the integrity of steel coiled tubing and pose a threat to personnel and rig operations. Accordingly, steel coiled tubing is usually retired from service after only a few trips into a well bore. However, composite coiled tubing is largely unaffected by such bending events and can remain in service for a much longer period of time. 
     Hence, systems utilizing composite coiled tubing can be safely and cost-effectively used to drill and explore deeper and longer oil wells than previously possible with conventional drilling systems. Moreover, completed but unproductive wells may be reworked to improve hydrocarbon recovery. Thus, composite coiled tubing systems can allow drilling operations into territories that have been inaccessible in the past and thereby further maximize recovery of fossil fuels. 
     However, these dramatic improvements in drilling operations require handling systems that can efficiently and cost-effectively deploy extended lengths of composite coiled tubing. In prior art coiled tubing handling systems, the reel assembly is generally the largest single component of the coiled tubing unit. The size of the reel assembly is often indirectly limited by various governmental codes and regulations. For example, on many domestic highway routes, additional fees are levied on tractor-trailer combinations that exceed a specified weight or size limitation. Further, because offshore platform space is at a premium, many drilling companies place strict requirements on the amount and size of equipment permitted on the rig at any given time. The size and load carrying limits of available barges or transport ships may also limit the physical size of the reel. 
     Nonetheless, a reel having a large storage capacity provides operational efficiencies. For example, two reels storing 12,000 feet of coiled tubing each can be deployed more efficiently than three reels storing 8,000 feet each. One reason for this efficiency is that a two reel configuration eliminates a reel change-out. That is, by carrying longer lengths at one time, large coiled tubing reels benefit drilling companies because they reduce the number of work stoppages required to insert a new reel of tubing into the work string. Because rig time is very expensive, it is often cost-effective to minimize the elapsed time for tubing deployment. 
     For these reasons, a coiled tubing system that both maximizes the length of tubing that can be deployed and minimizes the physical size of the unit is desired. Because composite coiled tubing can be deployed in lengths vastly greater than has been possible with steel coiled tubing, there is a need for a transportable reel that can store large quantities of coiled tubing. 
     In summary, while oil and gas recovery operations could greatly benefit from coil handling systems capable of handling long lengths of coiled tubing, the prior art does not disclose such handling systems. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention overcomes the deficiencies of the prior art by including the design of a reel assembly that can be disassembled for transportation. Such a reel assembly may be deployed more efficiently than prior art designs. One benefit of this design is that the empty reel assemblies can be removed from the coiled tubing platform without disturbing the operation of the remaining reel assemblies in order to provide room on the platform for the remaining reel assemblies to operate without obstruction. This design allows empty reels to be packaged and shipped in a manner that is more efficient than what was possible under the limitations of the prior art. 
     Other objects and advantages of the present invention will be apparent in the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more detailed description of the preferred embodiment of the present invention, reference will now be made to the accompanying drawings, wherein: 
     FIG. 1 illustrates an embodiment of the present invention mounted on a drilling rig; 
     FIG. 2 is an exploded view of one embodiment of a coiled tubing spool constructed in accordance with the present invention; 
     FIG. 3 is an end view of an embodiment of the present invention, showing one-half of one side wall removed; 
     FIG. 3 a  is an isometric view of the embodiment of FIG. 3; 
     FIG. 3 b  is an isometric view of the embodiment of FIG. 3 with reinforced wire mesh sidewalls; and 
     FIG. 4 is and end view of another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, a reel  20  constructed in accordance with the present invention is mounted on a cradle  24  located on a drilling rig  26  at a well site. Reel  20  stores an extended length of composite coiled tubing  28  that is run into a well bore  30 . Tubulars made of composites are discussed in pending application Ser. No. 09/081,961 filed May 20, 1998, titled “Well System,” which is hereby incorporated by reference for all purposes. Preferred embodiments of reel  20  that may be adapted to various well sites are described below. 
     Referring now to FIG. 2, a preferred embodiment of reel  20  includes a drum  40 , a first sidewall  42 , a second sidewall  44 , threaded studs  46 , and nuts  48 . Threaded studs  46  are preferably circumferentially arrayed on end faces  50 ,  52  of drum  40 . 
     First and second sidewalls  42 ,  44  retain the composite coiled tubing that may be spooled onto hub  42 . Because first and second sidewalls  42 ,  44  are substantially identical, only first sidewall  42  will be described in detail herein. Referring now to FIGS. 3 and 3 a , first sidewall  42  preferably comprises a plurality of sectional flanges  60  contiguously disposed on first drum face  50 . According to a preferred embodiment, flanges  60  include clearance holes  62  arranged to receive threaded studs  46 . A similar arrangement is provided for flanges  61  of second sidewall  44 . It will be understood that any number of releasable locking arrangements may be used to secure flanges  60  to drum  40 . For example, clamps (not shown) adapted to releasably receive flanges  60  may be provided on drum  40 . 
     It is known that composite coiled tubing spooled onto drum  40  does not impose significant loading along the axis of drum  40 . Accordingly, flanges  60  may be designed with an emphasis on minimizing shipping and handling difficulties. For example, flanges  60  may be formed as thin lightweight steel plates or as walls of reinforced wire mesh to reduce weight. Additionally, flanges may include perforations or be arranged in a non-contiguous fashion for further reductions in size and weight. Indeed, nearly any structure retains the coiled tubing on drum  40 , such as radially disposed bars (not shown), may also be used. 
     Drum  40  supports the composite coiled tubing spooled onto and payed out from reel  20 . Cradle  24  (FIG. 1) rotates drum  40  via an interconnecting axle  25 . Still referring to FIGS. 3 and 3 a , drum  40  includes a hub  41 , a centerpiece  43 , and a plurality of spokes  45 . Hub  41  is concentrically supported on centerpiece  43  by outwardly radiating spokes  45 . Hub  41  presents a winding surface  49  on which composite coil tubing seats. Arrangements for the winding surface are disclosed in commonly-owned U.S. application Ser. No. 09/443,407 entitled Reel for Supporting Composite Coiled Tubing, which is hereby incorporated by reference for all purposes. Lifting eyes (not shown) may be provided to facilitate shipment and manipulation of drum  40 . 
     Preferably, the diameter of hub  41  is selected to introduce a strain of 2% or less in the composite coiled tubing. Thus, for composite coiled tubing having a diameter of 2⅞ inches, the diameter of hub  41  should be approximately  144  inches or greater. Similarly, for composite coiled tubing having a diameter of 3{fraction (7/8 )} inches, the hub diameter should be approximately  194  inches or greater. It is expected that a hub diameter selected in accordance with the stated criteria will optimize the operating life of the composite coiled tubing. However, it should be understood that advances in composite materials may allow hub diameters that introduce strains of greater than 2% into the composite coiled tubing. 
     The several elements of drum  40  are preferably fabricated separately and can be assembled by standard welding procedures, threaded fasteners or any other suitable means. Preferably, drum  40  is formed to be shipped as a single unit. However, if the fabricated diameter of hub  40  is not within permissible transportation limitations, an axle split line  56  be used to break drum  40  into mating semicylindrical halves  58   a,b . Mating semicylindrial halves  58   a,b  can be joined using a variety of known methods, such as threaded fasteners (not shown). The use of additional splitlines will further reduce the size and weight of the individual sections that make up drum  40 . Furthermore, the joining method may take advantage of the operational characteristics of composite coiled tubing. For example, when pressurized drilling fluid is pumped into a well via composite coiled tubing, the portion of composite coiled tubing spooled on a reel tends to expand radially. This radial expansion results in a compressive force on hub  40  that may assist in maintaining the structural integrity of drum  40  that incorporates splitlines. 
     Referring now to FIG. 4, another embodiment of reel  20  includes mating first and second portions  70 ,  72 . Because first and second reel portions  70 ,  72  are substantially symmetrical, only first reel portion  70  will be described. First reel portion  70  is preferably formed as a single unit having a centerpiece  74  having outwardly radiating spokes  76  that support a hub  78 . Hub  78  provides a winding surface  80  for seating the composite coiled tubing. Sidewalls  82 ,  84  are fixed on hub end faces  79 . It will be appreciated that the unitary design of first reel portion  70  allows the use of numerous fabrication methods such as fillet welds, threaded fasteners, interlocking members, or combinations thereof To join first reel portion  70  to second reel portion  72 , a plurality of threaded studs  86  may be provided on spokes  76  of first portion  70 . Clearance holes  88  on second reel portion  72  are adapted to receive threaded studs  86 . Nuts (not shown) threaded onto threaded studs  86  secure first reel portion  70  to second reel portion  72 . It should be understood that first and second reel portions  70 ,  72  may be assembled by any suitable number of method and the described use of threaded studs is merely exemplary. Furthermore, it will be understood that reel  20  may be divided into more that two segments. Thus, acceptable arrangements of preferred reel  20  may include three or more portions that are readily releasable and engagable. 
     For 1500 meters of composite coiled tubing having 2⅞ inch gage, an exemplary reel may have a hub diameter of twelve feet and an overall diameter of eighteen feet. An exemplary disassembly arrangement may include first and second sidewalls that comprise eight flanges each. Such a disassembly arrangement would provide flanges with a maximum width of approximately seven feet and a drum diameter of twelve feet. Thus, the maximum dimension of any component to be transported is reduced from eighteen feet to twelve feet. The sidewall may be formed from more or fewer flanges. Additionally, a split line may be used to further reduce the size and weight of the drum. For composite coiled tubing having gages of 3½ inches, 4½ inches or greater, coiled tubing lengths of 1500 meters would necessitate larger reels. However, such reels would nonetheless breakdown into readily transportable components if designed in accordance with the present invention. 
     The above described embodiments of the present invention may be used for a well completion or workover operation where the well operator intends to use an extended length of composite coiled tubing. While the composite coiled tubing may be shipped on several separate spools and interconnected during injection into a well bore, a well operator may opt to utilize a single reel for subsequent composite coiled tubing handling. 
     Typically, a well operator selecting a reel in accordance with the present invention will employ a two-step process to arrive at an optimal design for a reel. The first step is to establish overall design dimensions of the reel with respect to the configuration of coiled tubing to be used. Usually, the overall dimensions of the reel are dictated by the required storege capacity, i.e., the length and gage of composite coiled tubing to be spooled, and the expected static and operational loads. The second step is to establish a disassembly design that facilitates the transportation and handling of the required reel. The disassembly configuration of the reel for a given well site is dictated by factors such as shipping costs, size restrictions along transport routes, the capacity of storage facilities at a well site, applicable safety regulations, and the weight limitations on lifting equipment such as cranes and cables. 
     Once the design has been established for the several components of the reel (hereinafter the master reel), the master reel components may be fabricated and shipped to the well site. Relatively short lengths of composite coiled tubing are delivered to the well site on small individual reels. During well operations, the short lengths of composite coiled tubing are made-up as required and sequentially injected into a well bore. Arrangements for such an operation are discussed in pending application Ser. No. 09/081,961 titled “Well System.” When operations require that the entire extended length of composite coiled tubing be tripped out of the well bore, the master reel is assembled and installed on a suitable platform. After establishing the appropriate connections, the entire extended length of composite coiled tubing may be spooled onto the master reel. It is contemplated that more than one master reel may be utilized during the spooling/retrieval process. The actual number of master reels, of course, depends on the length of the composite coiled tubing injected into the well. Thus, an extended length of tubing may be readily retrieved and deployed without having to spool the extended length of tubing onto several small reels. 
     It can be seen that once the present reel is loaded with the extended length of composite coiled tubing at a well site, the reel may be readily transported to other well sites in the vicinity. Moreover, if the reel is housed on a ship, the reel may be transported to nearly any offshore well. Thus, for well servicing operations subsequent to the initial operation, a reel made in accordance with the present invention reduces or even eliminates reel change-outs during both the injection and retrieval phases. 
     While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. Furthermore, where methods have been described, it should be understood that the individual steps of the methods may be executed in any order, unless a specific order is expressly prescribed. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.