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

1. Field of the Invention

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.

2. Description of the Prior Related Art

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.

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.

The injector head comprises components that are subject to considerable wear and therefore require frequent maintenance.

The following patents discuss background art related to the above discussed subject matter:

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.

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..

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.

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.

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.

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

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.

One possible object of the present invention is to provide an improved injector head assembly for a coiled tubing system.

Another possible object of the present invention is to provide a coiled tubing injector requiring reduced maintenance costs and down time during operation.

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.

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

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:

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.

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.

FIG. 3 is an elevational view, in section, of a coiled tubing injector apparatus in accord with one possible embodiment of the present invention.

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;

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

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.

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.

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.

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.

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.

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.

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.

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.

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.