Abstract:
A connector which joins two opposing sections of coil tubing or coil tubing to coil tubing tools so as to enable torque applied from one section to be transmitted to the other section is provided. The connector employs varying width and depth grooves into which portions of the sections of coil tubing are deformed so as to create the torque transmitting connection between the connector and sections of coil tubing. Each of the grooves have a narrow width portion and a wide width portion and corresponding shallow depth and deep depth portion. The narrow width portion of one of the grooves is approximately 180° out of phase from the narrow width portion of the other varying width groove.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to connectors for coil tubing and more specifically to a connector, which grips adjacent tubing sections so as to allow torque to be transmitted between such tubing sections. 
     BACKGROUND 
     Coil tubing is primarily used to perform various down hole operations in oil and gas wells. The depth of the well can be many thousands of feet which makes the continuous coil tubing reel very heavy and in some situations impossible to move in one piece. In offshore rigs, the weight of the coil tubing reel is limited by crane capability and other logistical issues related to the harsh working environment, which requires the coil tubing to be transported in two or three reels. Conventional methods of joining coil tubing requires a certified welder to weld two ends of coil tubing together without significantly de-rating the fatigue limit of the coil tubing, which is in the range of 30-40% for a manual butt weld. However, certified welders are very expensive and not always readily available. The equipment needed to insure a high integrity weld is also expensive and not always readily available. 
     There are several coil tubing connectors on the market which have attempted to address some of these issues. A dimple connector is one example of such a connector. It uses a dimpling method to join two ends of the coil tubing to a central connector. The center of the connector is formed with radial slots filled with elastomeric pieces. The dimple connector has an acceptable fatigue life and exhibits a good tensile strength; however, the elastomeric material is not suitable in all fluid environments. Furthermore, this design requires a hydraulic dimpling tool on location. 
     A simple roll-on type connector has also been proposed. However, such connectors do not have a good torque rating and hence are not practical for joining two ends or sections of coil tubing. Other connectors, such as slip connectors and splined connectors, are not spoolable and therefore are also not practical for joining spoolable coil tubing. 
     Therefore, there is a need in the coil tubing industry for a connector which has good tensile and fatigue strength, can be spooled easily on a reel, requires minimal equipment to install, and has good torque imparting characteristics. 
     SUMMARY 
     In one embodiment, the present invention is directed to a connector which joins two sections of coil tubing. The connector is defined by a generally cylindrical main body having a mid-section and opposing ends. The connector is further defined by a first pair of varying width and depth grooves formed in the mid-section of the main body adjacent to one of opposing ends of the main body and a second pair of varying width and depth grooves formed in the mid-section of the main body adjacent to the other opposing end of the main body. Each of the varying width and depth grooves in the first and second pairs of varying width and depth grooves has a narrow width and depth portion and a wide width and depth portion. The depth is shallow at the narrow portion of the groove and deep at the wide width portion of the groove. 
     In one embodiment, the narrow width portion of one of the varying width and depth grooves from the first pair of varying width and depth grooves is approximately 180° out of phase from the narrow width portion of the other varying width and depth groove from the first pair of varying width and depth grooves. Similarly, the narrow width portion of one of the varying width and depth grooves from the second pair of varying width and depth grooves is approximately 180° out of phase from the narrow width portion of the other varying width and depth groove from the second pair of varying width and depth grooves. Likewise, the wide width portion of one of varying width and depth grooves from the first pair of varying width and depth grooves is approximately 180° out of phase from the wide width portion of the other varying width and depth groove from the first pair of varying width and depth grooves and the wide width portion of one of the varying width and depth grooves from the second pair of varying width and depth grooves is approximately 180° out of phase from the wide width portion of the other varying width and depth groove from the second pair of varying width and depth grooves. In one embodiment, each of the grooves diverges from the narrow width portion to the wide width portion at an approximate angle of 3° also resulting in change of depth of grooves from 0.156 inches to 0.096 inches. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The present invention may be better understood by reference to one or more of these drawings in combination with the description of embodiments presented herein. However, the present invention is not intended to be limited by the drawings. 
         FIG. 1  is a schematic diagram illustrating the connector according to the present invention. 
         FIG. 2  is a perspective view of the spoolable connector shown in  FIG. 1 . 
         FIG. 3  is an enlarged view of the varying width and depth grooves of the connector shown in  FIGS. 1 and 2 . 
         FIG. 4  is a diagram illustrating the taper of the varying width and depth grooves. 
         FIG. 5  is a schematic diagram of an end of another type of connector having the varying width and depth grooves in accordance with the present invention. 
         FIGS. 6A and 6B  are schematic diagrams of two sections of an off-center clamp used to crimp the varying width and depth grooves. 
         FIG. 7  is an axial view of two halves of the section of the off-center clamp shown in  FIG. 6A . 
         FIG. 8  is an axial view of two halves of the section of the off-center clamp shown in  FIG. 6B . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described with reference to the following exemplary embodiments. Referring now to  FIG. 1 , a spoolable connector is shown generally by reference number  10 . The spoolable connector connects two sections of a coil tubing (not shown). The spoolable connector  10  is generally cylindrical in shape and formed of a metal alloy such as AISI-SAE 4130 Modified, but as those of ordinary skill in the art will appreciate other suitable metals or materials may be used to form the spoolable connector so as to give it its desired tensile and fatigue strength yet make it ductile enough to bend. The spoolable connector  10  is defined by a main body having a mid-section  12  and opposing ends  14  and  16 . The spoolable connector  10  further includes a pair of circular grooves  18  and  20  formed in the mid-section  12  of the main body. 
     One of the circular grooves  18  is disposed adjacent to opposing end  14  of the main body and the other circular groove  20  is disposed adjacent to opposing end  16  of the main body. A generally circular or ring-shaped seal (not shown) fits within the circular groove  18  in use (i.e., when the connector is installed). The seal prevents fluids from flowing into or out of the corresponding section of coil tubing. A second generally circular or ring-shaped seal fits within the circular groove  20  in use and also performs the function of sealing the respective corresponding section of coil tubing to the connector thereby preventing fluid from flowing into or out of the coil tubing. The seals, generally circular (e.g., O-ring shaped), V-ring shaped, molded on or bonded and machined may be formed of rubber, elastomer, a soft metal, or other suitable material with or without backups formed of metal, plastic or any combination of these, which prevents fluids from flowing into and out of sections of the coil tubing. The circular grooves  18  and  20  are machined into the main body of the spoolable connector  10  using conventional machining techniques. As those of ordinary skill in the art will appreciate more or less seals and corresponding grooves may be provided depending upon the application and environment. For example, one, two or more circular grooves may be provided of differing width and depth on each end  14 ,  16  of the connector  10 . 
     The spoolable connector  10  further comprises opposing sets of varying width and depth grooves  22  and  24  formed at opposing ends of the mid-section.  12  of the main body. In one exemplary embodiment, one of the opposing sets of varying width and depth grooves  22  is disposed adjacent to the circular groove  18 . The other opposing set of varying width and depth grooves  24  is disposed adjacent the other circular groove  20 . Each of these grooves extends approximately 360° around the circumference of the main body and are off-plane from an adjacent groove. 
     Each of the grooves has a varying width and depth. The width varies from a minimum distance w (narrow width) to a maximum distance W (wide width), which is 180° apart from the minimum distance. In one embodiment, the minimum distance w is approximately 0.375 inches and the maximum distance W is approximately 0.445 inches, as illustrated in FIG.  3 . In one embodiment, the taper of the groove between the distance w and the distance W is approximately 3°, as illustrated in  FIG. 4 . The depth varies from a minimum depth d at a narrow width portion w to a maximum depth D at wider width portion W. In one embodiment, the minimum depth d is 0.096 inches and the maximum depth D is 0.156 inches. 
     As shown in  FIG. 3 , the center of the groove nearest the end  16  (groove  24   a ) is offset a distance OD 1  from the centerline CL of the connector  10  and the center of the groove nearest the mid-section  12  (groove  24   b ) is offset a distance OD 2  from the centerline CL. The offset distance OD 1  is shown below the centerline CL in  FIG. 3  and the offset distance OD 2  is shown above the centerline CL. Accordingly, the distance between the centerline of the groove  24   a  and centerline of the cylindrical body (OD 1 ) is approximately 0.018 inches. The distance between the centerline of the groove  24   b  and the centerline of the cylindrical body (OD 2 ) is approximately 0.03 inches. Alternatively, the offset distance OD 1  and OD 2  can be the same. Thus, the grooves  24   a  and  24   b  have offset radii and varying width and depth. 
     In one exemplary embodiment, the distance between the varying width and depth grooves  22  and  24  nearest the mid-section  12  from each other is 4 inches or greater. Distances of 4 inches or greater enable greater bending of the spoolable connector  19  around the spool. As those of ordinary skill in the art will appreciate, the number, length, width, depth and exact orientation of the varying width and depth grooves may be varied. 
     In one exemplary embodiment, the pair of opposing sets of varying width and depth grooves  22  and  24  mate with crimped sections of the opposing sections of coil tubing. A crimping tool known in the art is used to deform the coil tubing into the sets of partial grooves  22  and  24 . A crimpling tool is a C-shaped pipe cutting tool with the cutting wheel replaced with a roller indenter. The roller indenter has dimensions matching the groove dimensions on the connector. 
     An installation clamp  23   a ,  23   b  as shown in  FIGS. 6A and 6B  is used to crimp the corresponding sections of coil tubing on to the varying width and depth grooves  22  and  24 . The installation clamp  23   a ,  23   b  is placed over the coil tubing (which is positioned over the connector) at the corresponding location on the connector where the varying width and depth grooves  22  and  24  are to be formed. The installation clamp  23   a ,  23   b  consists of two sections  25  and  27  with each section further divided in two halves  25   a  and  25   b , and  27   a  and  27   b , respectively, axial views of which are shown in  FIGS. 7 and 8 , respectively. The centerline of installation clamp  23   a ,  23   b  is off center by distance OD 2 . The purpose of two sections is to allow the roller indenter to be able to crimp the coil tubing. The purpose of two halves are ease of assembly. The crimping tool is then placed over the installation clamp with the indenter portion between the gap of two sections  25  and  27  of installation clamp. This allows the roller indenter to push sections of coil tubing onto the varying width and depth grooves. 
     Since the installation clamp  23  is off-center by the off-center distance of varying width and depth grooves  22  and  24 , the crimping tool rotates eccentrically on the coil tubing resulting in lesser penetration at the thick portion of installation clamp  25  and deeper penetration at the thin portion of installation clamp. This results in a narrow width and shallow depth at the thin portion of the installation clamp position on the coil tubing and a wider width and deeper depth at the thick portion of the installation clamp position on the coil tubing. The crimping tool has a screw-type feed mechanism, which presses the sections of coil tubing to the desired depth as the roller indenter is pushed against it. 
     Because the grooves are of varying width and depth they lock with the coil tubing and hence the sections of coil tubing do not rotate relative to the spoolable connector thereby enabling the spoolable connector  10  to effectively transmit torque between the two opposing sections of coil tubing. The varying width of the groove acts as a wedge so as to grip the opposing sections of coil tubing rotationally, thereby enabling the connector to effectively transmit torque between the opposing sections of coil tubing. The varying depth compresses the portions of coil tubing harder on the connector thereby preventing any rotation. The varying width and depth grooves  22  and  24  are machined into the main body of the spoolable connector  10  using conventional machining techniques. 
     The spoolable connector  10  further has a plurality of radial slots  26  and  28  disposed on each of the opposing ends  14  and  16 , respectively. Each of the plurality of radial slots  26  and  28  extends partially around the circumference of the main body of the spoolable connector  10 . In one embodiment, each of the opposing ends  14  and  16  has four radial slots each of which extends approximately 270° around the circumference of the main body and is 90° out of phase from an adjacent radial slot.  FIG. 2  shows a perspective view of the spoolable connector  10  illustrating the opposing pairs of circular grooves  18  and  20 , the opposing sets of offset grooves  22  and  24  and the opposing radial slots  26  and  28 . 
     Each of the opposing ends  14  and  16  further include a plurality of longitudinal grooves  30  and  32  formed along each of said opposing ends. In one embodiment according to the present invention, each of the opposing ends  14  and  16  has multiple longitudinal grooves formed there along equally spaced from one another around the circumference of the main body. In one exemplary embodiment, six equally-spaced longitudinal grooves  30  and  32  are provided. The longitudinal grooves  30  and  32  accommodate the weld seam typically found on the inside surface of the opposing sections of coil tubing. It saves the time and expense of having to remove the weld seam, which is difficult especially for distances greater than six inches. Although only one such seam exists, having multiple longitudinal grooves provides for ease of installation of the opposing sections of coil tubing over the spoolable connector  10  with minimal axial misalignment and therefore decreases the amount of torsional preload applied to the spoolable connector  10 . The longitudinal grooves  30  and  32  are machined into the opposing ends of the spoolable connector  10  using conventional machine techniques. 
     Referring now to  FIG. 5 , an alternate connector utilizing the varying width and depth grooves of the present invention is shown. This embodiment places the circular groove  20 ′ for the seal between the varying width and depth grooves  24   a ′ and  24   b ′ and the mid-section  12 ′ rather than placing it between the varying width and depth grooves and the end  16 ′. This connector also does not have a plurality of radial slots  28  or plurality of longitudinal grooves. As those of ordinary skill in the art will appreciate, the varying width and depth grooves of the present invention have applicability in other types of connectors, i.e., those not necessarily dedicated to joining two ends of coil tubing. 
     Therefore, the present invention 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.