Abstract:
A coil tube injector head comprising at least two gearbox units, wherein each gearbox unit drives a gripper assembly comprising a plurality of gripper assembly links. The gripper assembly links comprise a gripper surface that engages a length of coil tubing and one or more roller bearings that engage a bearing plate. The coil tube injector head further comprises a skid plate that is coupled to the bearing plate and receives pressure from one or more traction cylinders. The assembly of the claimed embodiments further allows for ease of maintenance and service of the coil tube injector by operators in the field of oil and gas production.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/811,219, filed Apr. 12, 2013, which is incorporated herein by reference for all purposes. 
     
    
     BACKGROUND 
       [0002]    Hydrocarbons are an important resource which are often retrieved from ground by performing various subterranean operations. When performing subterranean operations, coil tube injector heads may be used to direct coil tubing (e.g., tubing which may be in a range of from approximately 1″ to approximately 3½″) into and out of a wellbore. The injectors provide a means of gripping the tubing to perform a controlled feeding operation. Injector heads are rated against the pushing/pulling force they can generate and the feedrate at which the tubing can be passed. 
         [0003]    A complete injector head may comprise several components. For instance, the injector head may include an injector head assembly; a crash frame (providing a degree of mechanical protection during service); a service platform (allowing the operators to manage the operation of coil tube injection during service); and a gooseneck (which controls the feed of the tubing into the injector from a separate coil tube spool). 
         [0004]    The basic premise of a coil tube injector is to simply grip the tubing with sufficient traction so that it does not slip when performing the desired subterranean operations, and then either pushing the tubing into a well or extracting it out. To achieve this goal, generally there are two sets of grippers, attached to a chain drive mechanism. The drives are generally hydraulically powered and when combined with a reduction gearbox provide sufficient torque to adequately move the loads. It is desirable to have an injector head which can operate smoothly and which can be easily maintained and serviced without disrupting ongoing subterranean operations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings. 
           [0006]      FIG. 1  is an illustration of a coil tube injector configuration in accordance with certain embodiments of the present disclosure. 
           [0007]      FIG. 2A  is a first perspective view of the injector head assembly of  FIG. 1  in accordance with an illustrative embodiment of the present disclosure. 
           [0008]      FIG. 2B  is a second perspective view of the injector head assembly of  FIG. 1  in accordance with an illustrative embodiment of the present disclosure. 
           [0009]      FIG. 2C  is a third perspective view of the injector head assembly of  FIG. 1  in accordance with an illustrative embodiment of the present disclosure. 
           [0010]      FIG. 3A  is a side close up view of the injector head assembly of  FIGS. 2A-C  in accordance with certain embodiments of the present disclosure. 
           [0011]      FIG. 3B  is a cross-sectional view of the injector head assembly of  FIG. 3A  in accordance with certain embodiments of the present disclosure. 
           [0012]      FIG. 3C  is a cross-sectional view of the injector head assembly of  FIG. 3A  with one side of the crash frame removed, in accordance with certain embodiments of the present disclosure. 
           [0013]      FIG. 4  is a close up view of one of the chain links of a gripper/chain assembly in accordance with certain embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Illustrative embodiments of the present invention are described in detail herein. In the interest of clarity, not all features of an actual implementation may be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation specific decisions must be made to achieve the specific implementation goals, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of the present disclosure. 
         [0015]    To facilitate a better understanding of the present invention, the following examples of certain embodiments are given. In no way should the following examples be read to limit, or define, the scope of the invention. Embodiments of the present disclosure may be used with any wellhead system. Embodiments of the present disclosure may be applicable to horizontal, vertical, deviated, or otherwise nonlinear wellbores in any type of subterranean formation. Embodiments may be applicable to injection wells as well as production wells, including hydrocarbon wells. 
         [0016]    The terms “couple” or “couples” as used herein are intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect mechanical or electrical connection via other devices and connections. 
         [0017]    The methods and systems disclosed herein are not limited to any particular unit size. For instance, in certain implementations, the injector head unit may be an ‘80 k’ (80,000 psi) unit. However, the design concept can easily be upscaled and downscaled to suit the actual requirements. The methods and systems disclosed herein are directed to an actual operation constraint with regard to ease of operation and maintenance, making a ‘simple’ unit which is easily maintained and therefore, can be kept in production. 
         [0018]    A coil tube injector in accordance with an illustrative embodiment of the present disclosure is generally denoted with reference numeral  100  in  FIG. 1 . As shown in  FIG. 1 , a coil tube injector  100  is comprised of an injector head assembly  102 , a crash frame  104  that provides mechanical protection to the injector head assembly  102 , a service platform  106  that allows the operators to perform service on the coil tube injector  100  and manage the operation of the coil tube injector  100  during service, and a gooseneck  108  that controls the feed of the coil tubing  110  into the injector head assembly  102  from an external coil tube spool (not shown). Specifically, a spool (not shown) may be disposed near the coil tube injector  100  and a coil tubing  110  may be drawn from the spool and directed over the gooseneck  108 , and through the injector head assembly  102 , into the wellbore. 
         [0019]      FIGS. 2A-C  depict different perspectives of a close up view of the injector head assembly  102  of  FIG. 1 , in accordance with an illustrative embodiment of the present disclosure. As shown in  FIGS. 2A-C , the injector head assembly  102  may include a pair of gearbox units  202 A,  202 B, each coupled to a corresponding gripper/chain assembly  204 A,  204 B, respectively. In certain implementations, the gearbox units  202 A,  202 B may be a hydraulic drive gearbox unit. Accordingly, each gripper/chain assembly  204 A,  204 B may be driven by the corresponding gearbox unit  202 A,  202 B. The injector head assembly  102  may further include one or more traction cylinders  206  that operate to apply pressure to skid plates  208 . 
         [0020]    Turning now to  FIG. 3A-C , the operation of the traction cylinders  206  and the skid plate  208  in accordance with an illustrative implementation of the present disclosure is disclosed in further detail. Specifically,  FIG. 3A  depicts a side close-up view of the injector head assembly  102  of  FIG. 1  and  FIGS. 2A-2C .  FIG. 3B  depicts a cross-sectional view of the injector head assembly  102  of  FIG. 3A . Similarly,  FIG. 3C  depicts a cross-sectional view of the injector head assembly of  FIG. 3A  with one side of the crash frame  104  removed to show the components as they are configured therein. 
         [0021]    As shown in  FIG. 3A-C , each skid plate  208  is coupled to a bearing plate  212 . The skid plates  208  and the bearing plates  212  may be made from any suitable material known to those of ordinary skill in the art. For instance, in certain illustrative embodiments, the skid plates  208  may be made from high grade aluminum and the bearing plates  212  may be made from hardened steel. The bearing plates  212  provide the wearing surface that is in contact with the roller bearings of the gripper/chain assembly  204 , as discussed in more detail below. 
         [0022]      FIG. 4  depicts a close-up view of one of a chain link of a gripper/chain assembly  204 A,  204 B which is denoted generally with reference numeral  400 . In certain illustrative embodiments, the chain link  400  may consist of a roller bearing  402  on one side and a gripper  404  on the other side. As shown in  FIG. 4 , the roller bearing  402  may be disposed on the side opposite to the gripper  404 . 
         [0023]    Each gripper/chain assembly  204 A,  204 B may have a plurality of chain links  400  each having one or more roller bearings  402  and one or more grippers  404  as shown in  FIG. 4 . The grippers  404  are configured to engage a length of coil tubing running through the injector head assembly  102 . In certain illustrative embodiments, each gripper  404  may be configured as a semi-cylinder shaped cut-out allowing the surface of the gripper  404  to engage a greater area of the coil tubing  110  and more evenly apply pressure to the coil tubing  110 . The cut-out for a gripper  404  may be sized differently to engage with different sizes of coil tubing  110 . As shown in  FIGS. 3A-C  and  FIG. 4 , the gripper  404  may be coupled to roller bearings  402 , which in turn engage a bearing plate  212 . The use of roller bearings  402  serves to reduce friction between the gripper/chain assembly  204 A,  204 B and the corresponding bearing plate  212  by allowing the roller bearings  402  to roll across the surface of the bearing plate  212 . Multiple links in the gripper/chain assembly  204  may be coupled through chain links  400 . This arrangement permits an operator to replace/repair either one gripper  404  at a time or to replace/repair the entire gripper/chain assembly  204 A,  204 B in one service operation. Replacing the entire gripper/chain assembly  204 A,  204 B in one operation ensures that all grippers  404  operate in a similar condition, i.e., a singular worn item does not get maintained with the system. This also allows service to be performed in a shorter amount of time. 
         [0024]    Returning to  FIGS. 3A-C , the bearing plates  212  which are coupled to corresponding skid plates  208  provide a wearing surface for rollers  402  on the gripper/chain assembly  204 . The traction cylinders  206  provide the force to push and pull the skid plate  208  so as to engage the bearing plate  212  with the gripper/chain assembly  204 . Accordingly, the traction cylinders  206  can move the skid plates  208 , and in turn, the bearing plates  212 , between different positions to apply more, or less pressure, on to the coil tubing  110 . For instance, the traction cylinders  206  may move the skid plates  208  and the bearing plates  212  between a first position which is further from the coil tubing  110  being directed through the injector head assembly  102  and a second position which is closer to the coil tubing  110 . Accordingly, this configuration of the bearing plates  212  provides for reduced friction under load and provides a means of controlling the pressure on each gripper  404  as it is engaged within the load cycle via the skid plate  208  and traction cylinders  206 . 
         [0025]    Specifically,  FIG. 3B  provides an illustration of the injector head assembly  102  focusing on the interaction of the skid plate  208 , the bearing plate  212 , and each gripper/chain assembly  204 A and  204 B. The operation of the injector head assembly  102  is now discussed in conjunction with one of the gripper/chain assemblies  204 A. The other gripper/chain assembly  204 B operates in the same manner. As shown in  FIG. 3B , traction cylinders  206  apply pressure to the skid plate  208 , which in turn applies pressure to the bearing plate  212 . This brings the bearing plate  212  into contact with the gripper/chain assembly  204 A, enabling the roller bearings  402  of the gripper/chain assembly  204 A to roll across the surface of the bearing plate  212 . Additionally, the pressure to the bearing plate  212  engages the grippers  404  of the gripper/chain assembly  204 A with a length of coil tubing that is being directed between the two gripper chain assemblies  204 A and  204 B. 
         [0026]      FIG. 3C  is an illustration of an injector head assembly  102  focusing on the motion of each gripper/chain assembly  204 A,  204 B and the corresponding hydraulic drive gearbox unit  202 A,  202 B. As shown in  FIG. 3C , each gripper/chain assembly  204 A,  204 B is coupled to a corresponding drive motor  205 A,  205 B which is driven by the gear box unit  202 A,  202 B. The drive motors  205 A,  205 B provide a counter rotation arrangement to direct the coil tubing  110  into the well (or to pull the coil tubing  110  out). Specifically, the drive motors  205 A,  205 B are configured to turn in opposite directions such that the two facing sides of the two gripper/chain assemblies  204 A,  204 B move in the same vertical direction, i.e., move up together or move down together. In this configuration, one or more grippers  404  from each gripper/chain assembly  204 A,  204 B is able to engage with a length of coil tubing  110  running between the two facing sides of the two gripper/chain assemblies  204 A,  204 B. 
         [0027]    In operation, the traction cylinders  206  are pressured, moving the skid plates  208  towards the centrally located coil tubing  110  as it is passing through the gripper/chain assemblies  204 A,  204 B. Once the gripper/chain assemblies  204 A,  204 B engage with the coil tubing  110 , a reaction force is applied back through the bearing plates  212  and the skid plates  208 , thereby allowing a precise control of the position and load being applied to the coil tubing  110 . This arrangement is replicated about the vertical centerline of the injector head assembly  102 , allowing the gripper/chain assemblies  204 A,  204 B to encapsulate the coil tubing  110  and move the coil tubing  110  up or down as directed by the drive motors  205 A,  205 B. Accordingly, the traction cylinders  206  apply pressure to the skid plates  208 , to bring the bearing plates  212  into contact with the gripper/chain assembly  204 A,  204 B so as to engage a coil tube  110 . 
         [0028]    In certain implementations, the skid plate  208 , which may be manufactured from high grade aluminum, may be guided via slides which are disposed on the skid plate  208 . In certain implementations, there may be four slides, one located at each corner of the skid plate  208 . Composite bearings may be used to ensure that the skid plate  208  slides smoothly on the guides. The traction cylinders  206  provide the force to push and pull the skid plate  208 . The skid plate  208  is of a robust design to minimize the amount of deflection it will experience under the load condition. Minimizing the distortion ensures that the bearing plate  212  provides a smooth and level surface on which the roller bearings  402  of the gripper/chain assembly  204  can run. 
         [0029]    Returning now to  FIGS. 2A-2C , the injector head assembly  102  may further include one or more tensioning cylinders  210 . In certain implementations, the tensioning cylinders  210  may be disposed to apply a force in a direction that is substantially perpendicular to the direction of the force applied by the traction cylinders  206 . The tensioning cylinders  210  are configured to apply sufficient force to ensure there is no chain ‘slap’ during operation. Specifically, the tensioning cylinders  210  are operable to maintain a desired degree of tension within the chain/gripper assembly  204 . In certain implementations, the amount of force (pressure) applied to the traction cylinders  206  is proportional to the amount of grip force that will be exerted to the coil tubing  110 . 
         [0030]    In certain implementations, the traction cylinders  206  and the tensioning cylinders  210  are located or accessible from the outside of the injector head assembly  102 . For instance, as shown in  FIGS. 2A-C , the traction cylinders  206  and the tensioning cylinders  210  may be mounted to an outer side of the crash frame  104 . Accordingly, a single cylinder (either traction cylinder  206  and/or tension cylinder  210 ) may be removed and disengaged from the skid plate  208  to allow for replacement and/or repair of the cylinder. The remaining cylinders will continue to operate. As a result, the operable items may be repaired/replaced insitu and the injector head assembly  102  can remain in position above the well while it is being serviced. Additionally, in a preferred embodiment, the cylinders may all be of the same specification, simplifying the replacement of any cylinder during maintenance. 
         [0031]    Accordingly, the use of the roller bearings  402  which run against the bearing plate  212  under the load condition reduces the friction when operating under a load. Additionally, the interaction of the bearing plates  212  with the roller bearings  402  of the gripper/chain assembly  204  provides a means of controlling the pressure applied by each gripper/chain assembly  204 A,  204 B as it engages the coil tubing  110 . Specifically, the applied pressure by each gripper/chain assembly  204  in a load cycle may be controlled by an operator using the traction cylinders  206  which apply pressure to the roller bearings  402  through the skid plates  208  and the bearing plates  212 . 
         [0032]    Moreover, the bearing plates  212  are sacrificial items given the arduous nature of coil tubing. The bearing plates  212  may be accessed from the front and rear of the injector head assembly  102  and they may be easily removed to the sides of the injector head assembly. Accordingly, the bearing plates  212  may be easily replaced and/or repaired in situ. 
         [0033]    Additionally, the gripper/chain assemblies  204 A,  204 B (including the grippers  404  and the roller bearings  402 ) are highly loaded during service. Accordingly, in certain implementations, the vertical space may be maximized to allow additional gripper assemblies to be in the load path, thus reducing the load to individual grippers  404 , which in turn extends the life of the injector head assembly  102 . Further, the grippers  404  are an integral part of the gripper/chain assembly  204 . Accordingly, in certain implementations, a gripper carrier allows individual replacement of grippers  404 . In another embodiment, the whole gripper/chain assembly  204  may be replaced in one operation. This results in a quick service period to change gripper size (e.g., going from 1½″ to 2″) and ensures that all grippers operate in a similar condition, i.e., a singular worn item does not get maintained with the system. When the gripper/chain assembly  204  or the grippers  404  do become worn out, an effective replacement can be made in a short time period which may be in a matter of minutes. Operational time is typically of great importance when performing subterranean operations. Accordingly, the longer the machine can operate and maintain performance the better. 
         [0034]    In certain embodiments, different components may be manufactured from high grade aluminum which is sufficiently strong while giving a reduced weight compared to steel (steel being roughly 2½ times the weight of aluminum). The benefit of reduced weight is the ease of handling during installation, making the operator&#39;s job easier and therefore more productive. 
         [0035]    Therefore, the present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified, and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.