A coiled tubing injector apparatus for inserting and/or removing coiled tubing from a well head comprising a first injector column and a second injector column forming a central pathway within a frame. The first and second injector columns each comprise an inner and outer band, the outer band containing a plurality of rolling elements for engaging the coiled tubing and the inner band creating drive force to energize the outer band. The inner band further comprises a wear plate designed to sustain the majority of wear for less costly maintenance and repair of injection heads.

[0001]    This application claims benefit of U.S. Provisional Application No. 61/610,643 filed Mar. 14, 2012. The application listed above is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to oilfield production equipment and, more particularly, to a coiled tubing injector apparatus for inserting and removing coiled tubing from a well. 
         [0004]    2. Description of the Prior Related Art 
         [0005]    Coiled tubing has seen a marked increase in use through the oil and gas industry since its inception. Coiled tubing operations have grown from the limited applications thought feasible in the early 1950's and are now considered a viable solution in multiple operations, including subsea wells, snubbing, fracturing, and even coiled tubing applications. Coiled tubing operations have grown more popular as a result of their rapid mobilization times and generally smaller footprint with respect to traditional well operations. Furthermore, they require less site crew and personnel, in addition to significant cost savings. As applications for coiled tubing have become more numerous, the strength and size of the coiled tubing has increased in options as well. Coiled tubing was generally less than 1 in. in diameter in the beginning, while it can be found now in sizes up to 4 in. in diameter. 
         [0006]    Coiled tubing rigs primarily consist of an injector head for inserting and removing the coiled tubing from the wellhead, a spool reel for storing and transporting the coiled tubing, a power pack to power the injector head, and a control room to operate the machinery. The injector head is responsible for gripping the coiled tubing, usually through a series of grippers powered by a chain design, which provide enough force to move the tubing when necessary, without impeding the structural stability of the tubing. Although the other components are required to functionally operate the system, the injector head is the integral part of a coiled tubing rig. 
         [0007]    The injector head comprises components that are subject to considerable wear and therefore require frequent maintenance. 
         [0008]    The following patents discuss background art related to the above discussed subject matter: 
         [0009]    U.S. Pat. No. 8,191,3520, issued Jun. 5, 2012, to Maschek, Jr. et al. discloses a gripper assembly for use within a coiled tubing injector unit. The gripper assembly comprises a carrier for securing the gripper to the chain drive mechanism of the coiled tubing injector unit and a gripping shoe carried by the carrier. The configuration of the gripper assembly permits removal and replacement of the gripping shoe. 
         [0010]    U.S. Pat. No. 6,910,530, issued Jun. 28, 2005, to Austbo et al. discloses a coiled tubing injector apparatus for use in inserting coiled tubing into a well, temporarily suspending the coiled tubing, and removing the coiled tubing from the well is described. The apparatus includes a base with a pair of spaced-apart carriages extending upwardly therefrom. The base is part of a frame positioned above a wellhead. The carriages each have a gripper chain drive system rotatably mounted thereon and movable therewith. An actuation and linkage system allows the carriages to move toward and away from one another in a lateral or transverse direction with respect to the superstructure and the base. Thus, the gripper chain systems comprise gripper chains that can be engaged or disengaged from the coiled tubing extending through the apparatus. A wetting fluid basin is positioned below the gripper chains, and support guides engage the coiled tubing below the gripper chains to prevent buckling of the coiled tubing. The gripper chain drive system includes idler sprockets mounted on an idler sprocket shaft. The position of first and second ends of the idler sprocket shaft are monitored, and may be adjusted to maintain a parallel relationship with a drive sprocket shaft on which are mounted drive sprockets supporting the gripper chain.. 
         [0011]    U.S. Pat. No. 6,347,664, issued Feb. 19, 2002, to Perio, Jr. discloses a coiled tubing injector head comprised of a plurality of endless chains, each of which are at least three links wide, that are positioned around a plurality of sprockets and/or idler rollers within the injector head. A plurality of gripper assemblies are positioned around the middle links of the endless chains. A bearing skate is positioned within the injector head, the bearing skate being comprised of a plurality of bearings in a staggered configuration, the bearings being adapted for rolling engagement with a portion of the gripper assemblies. An injector head is comprised of a plurality of halves, each of the halves being coupled to a positioning bar, the positioning bar having a plurality of openings formed therein, the openings adapted for use in varying the distance between the first and second halves. 
         [0012]    U.S. Pat. No. 6,173,769, issued Jan. 16, 2001, to Goode discloses a gripping element of a coiled tubing injector has a carrier and a removable gripping shoe mounted to the carrier. The removable shoe slides onto slots formed on the carrier and is floated on the carrier by inserting an elastomeric pad sandwiched between the carrier and shoe. A manually depressible spring along ones side of the carrier prevents the shoe from sliding out of the slots during operation of the injector. 
         [0013]    U.S. Pat. No. 5,918,671, issued Jul. 6, 1999, to Bridges, et al. discloses an injector for flexible tubing has endless drive conveyors on opposite sides of a pathway for the tubing. The drive conveyors include gripper blocks that work in opposing pairs along the tubing pathway. The pairs of gripper blocks are clamped to the tubing and moved along the tubing pathway to either inject the tubing into a well or withdraw the tubing from a well. The gripper blocks are clamped to the tubing by way of skates, which work in opposing pairs. The skates have rollers, with rollers contacting the gripper blocks. Each roller has two ends, which ends are received by bearings inside of mounts on the respective skate. 
         [0014]    The above discussed prior art does not address solutions provided by the present invention, which teaches a system that is useful for increasing reliability and reducing the frequency and time required for repairing and/or maintaining injection heads. Consequently, those skilled in the art will appreciate the present invention that addresses the above described and other problems. 
       SUMMARY OF THE INVENTION 
       [0015]    A first possible object of the present invention is to provide a more reliable coiled tubing injector system for deep wells and high snubbing forces. 
         [0016]    One possible object of the present invention is to provide an improved injector head assembly for a coiled tubing system. 
         [0017]    Another possible object of the present invention is to provide a coiled tubing injector requiring reduced maintenance costs and down time during operation. 
         [0018]    Yet another possible object of the present invention is to provide an improved chain on chain skate design for use with coiled tubing operations, including snubbing and workover operations. 
         [0019]    These objects, as well as other objects, advantages, and features of the present invention will become clear from the description and figures to be discussed hereinafter. It is understood that the objects listed above are not all inclusive and are intended to aid in understanding the present invention, not to limit the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    A more complete understanding of the invention and many of the advantages thereto will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein: 
           [0021]      FIG. 1  is an exploded perspective view of a portion of a coiled tubing injector apparatus showing a skate plate in accord with one possible embodiment of the present invention. 
           [0022]      FIG. 2  is a top elevational view of a part of a coiled tubing injector apparatus showing a chain drive and skate plate in accord with one possible embodiment of the present invention. 
           [0023]      FIG. 3  is an elevational view, in section, of a coiled tubing injector apparatus in accord with one possible embodiment of the present invention. 
           [0024]      FIG. 4  is a side elevational view of a coiled tubing injector, partially in section, of section  10  of  FIG. 3 , in accord with one possible embodiment of the invention; 
           [0025]      FIG. 5  is a perspective view of a coiled tubing injector apparatus in accord with one possible embodiment of the present invention 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an exploded view of internal assembly  1 , which is a portion of coiled tubing injector apparatus  100 , shown assembled in  FIG. 5 , in accord with one possible embodiment of the present invention. In one embodiment, existing coiled tubing injector units may be modified or retrofitted in accord with the present invention for longer and more reliable operation. In one embodiment, coiled tubing injector  100  utilizes a chain on chain skate design in which manufactured rollers may be connected to chain links, and is designed for various pulling and snubbing applications. Coiled tubing injector  100  can be used for conveying various sizes of coiled tubing into and out of wells for a variety of other oil and gas operations. 
         [0027]    Internal assembly  1  utilizes center plate  10 , which comprises a plurality of circular orifices in which cylinder retaining rings  35  retain hydraulic cylinders  40 , in the process of compressing grippers that are used to grip the pipe. Skate plate  20  is located on a first side of center plate  10  and may be mounted to center plate  10  by support posts  55 . Skate plate  20  may, in one embodiment, be rectangular shaped with elongated sides containing cutout portions that correspond with cylinder retaining rings  35  of center plate  10  so as not to interfere with the operation of hydraulic cylinders  40 . Skate plate  20  further comprises channel  90  sized to receive elongate wear plate  15 . In this embodiment, it is not necessary that the entire skate plate be comprised of hardened material designed for longer wear in response to friction. Moreover, wear to skate plate is limited for less expensive repairs. Wear plate  15  is clamped to skate plate  20  by a plurality of clamp plates  30 , which fit within recesses  95  formed along channel  90  of skate plate  20 . Wear plate  15  may be thicker than channel  90  and, if desired, extend outwardly from skate plate  20 . Recesses  95  and clamp plates  30  may be shaped differently than shown and could be elongate. Clamp plates  30  further each comprise at least one tongue  32  which fit within corresponding slots  22  of wear plate  15 . Tongue  32  may be rectangular, round, or the like. In another embodiment, clamp plates  30  may be machined onto wear plate  15  with tongue  32  for insertion into corresponding recess  95  on skate plate  20 . 
         [0028]    Cap screws  75  further secure clamp plates  30  to skate plate  20 , but do not bear any of the lateral forces created through operation of coiled tubing injector  100 . The lateral forces on clamp plates  30  are supported by the walls of recesses  95  and the walls of slots  22 , therefore cap screws  75  need only fasten clamp plates  30  to skate plate  20 , a force which is not resisted during operation. 
         [0029]    Tensioner assembly  60  is located on an opposite side of center plate  10  with respect to skate plate  20  and secured to center plate  10  by bolts  80  and socket head screw  65 . Other types of fasteners may be utilized for this operation. Tensioner assembly  60  supports a plurality of injector springs  85  corresponding with hydraulic cylinders  40  respectively. Injector springs  85  expand and compress in response to the force exerted by hydraulic cylinders  40  during operation. Cylinder spacers  45  are placed between hydraulic cylinders  40  and center plate  10  for alignment purposes and to provide extended operation to account for size differences in coiled tubing. Tensioner assembly  60  comprises at least two prong sets which are for connecting with at least two of side plates  25  for securing tensioner assembly  60  with skate plate  20 . Side plates  25  interlock with tensioner assembly  60  and then are secured to skate plate  20  by small cap screws  70 . In other embodiments, alternative means of attaching side plates  25  with skate plate  20  may be used including pins, clamps, and the like. Side plates  25  mate with wear plate  15  and guide chain assembly  50  around skate plate  20  and wear plate  15 . In one embodiment, wear plate  15  comprises track  17  upon which chain assembly  50  revolves along during operation of coiled tubing injector apparatus  100 , to be discussed in more detail hereinafter. 
         [0030]    Turning now to  FIG. 2 , a top view of internal assembly  1 , with respect to the view of  FIG. 1 , is depicted in accord with one possible embodiment of the present invention. Chain assembly  50  comprises a plurality of rollers interconnected by a series of chain links rotating along track  17  of wear plate  15  (See  FIG. 1 ). However, the present invention is not limited to the current depiction of chain assembly  50  and may include alternative configurations in accord with the present invention. In another embodiment, chain assembly  50  may further comprise a skate cylinder traction beam and an alternative drive chain tension system, i.e. chain sprockets, planetary gears, hydraulic motors and/or controls, and the like may be used to drive chain assembly  50 . Skate plate  20  is fashioned to fasten with center plate  10  so that it does not interfere with hydraulic cylinders  40  or cylinder retaining rings  35  during normal operation of coiled tubing injector apparatus  100 . 
         [0031]    In  FIG. 3 , a front sectional view of coiled tubing injector  100  is depicted in accord with a preferred embodiment of the present invention. Coiled tubing injector  100  comprises first injector component  170  and second injector component  175  housed within frame  110 . First injector component  170  and second injector component  175  may be identical or substantially identical in structure with regards to internal assembly  1  as described in conjunction with  FIG. 1  and oppose each other with respect to central pathway  145 . In operation, first injector component  170  and second injector component  175  are used in conjunction to insert and/or remove coiled tubing  140  from central pathway  145  using grippers  120 ,  122 . Grippers  120 , 122  interconnect with gripper bands  115 ,  117  respectively, with gripper band  115  revolving around gears or sprocket pair  130 ,  132 , and gripper band  117  revolving around gears or sprocket pair  125 ,  127  respectively. In an alternative embodiment, gripper bands  155 ,  177  may be fashioned with grippers  120 ,  122  as a single, unified component. 
         [0032]    Grippers  120 , 122  apply pressure to coiled tubing  145  after being energized by hydraulic cylinders  40  being operated either manually or automatically, typically at a control room or at controls on frame  110 . Hydraulic cylinders  40  are operable to expand and contract, thereby changing the pressure grippers  120 ,  122  apply onto coiled tubing  145 , as well as converging first injector component  170  and second injector component  175  towards each other. Grippers  120 ,  122  may comprise a semicircular channel which provides a better contact area with coiled tubing  140 , although various shapes of grippers  120 ,  122  may be employed consistent with the teachings of the present invention. In some embodiments, grippers  120 , 122  may, if desired, comprise a substantially resilient material to depress for engaging with smaller diameter tubing or expand to handle larger diameter tubing. 
         [0033]    In  FIG. 4 , an enlarged front view of Section  11  of coiled tubing injector  100  as shown in  FIG. 3  is depicted in accord with one possible embodiment of the present invention. Center plate  10 , skate plate  20 , and wear plate  15  are arranged as described in detail when discussing  FIG. 1 . Chain assembly  50  makes contact with gripper assembly  120  providing a drive force to move gripper assembly during operation of coiled tubing injector apparatus  100 . In this embodiment, gripper assembly  120  further comprises carriers  115  for direct contact with chain assembly  50 . This arrangement prevents any undue wear upon skate plate  20  and provides for quicker and easy replacement of wear plate  15  instead of the more expensive skate plate  20 , which is also harder to replace. 
         [0034]    Referring now to  FIG. 5 , coiled tubing injector apparatus  100  is shown with adjustable base  165  for adjusting to various size wellheads. Adjustable base  165  is supported by posts  150 ,  155 ,  160  while the components of coiled tubing injector apparatus  100  as described hereinbefore are contained within frame  110 .