Abstract:
The subject disclosure provides a reel and a gooseneck which significantly reduce residual bending of the coiled tubing. The subject disclosure discloses a gooseneck that provides reverse bending forces to reduce the residual bending as a result of the reel. Further, the subject disclosure discloses a gooseneck having an adjustable radius during the coiled tubing operations which optimizes the residual bending process. The subject disclosure also discloses a heating and cooling module. The heating and cooling modules are attached to the gooseneck and are used to reduce fatigue of the coiled tubing and elongate the life cycle of the coiled tubing.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The subject disclosure generally relates to the field of coiled tubing and coiled tubing applications in hydrocarbon wells. More particularly, the subject disclosure relates to reducing residual bending and fatigue of coiled tubing. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    Coiled tubing refers to metal piping, used for interventions in oil and gas wells and sometimes as production tubing in depleted gas wells, which comes spooled on a large reel. Coiled tubing operations typically involve at least three primary components. The coiled tubing itself is disposed on a reel and must, therefore, be dispensed onto and off of the reel during an operation. The tubing extends from the reel to an injector. The injector moves the tubing into and out of the wellbore. Between the injector and the reel is a tubing guide or gooseneck. The gooseneck is typically attached or affixed to the injector and guides and supports the coiled tubing from the reel into the injector. Typically, the tubing guide is attached to the injector at the point where the tubing enters. As the tubing wraps and unwraps on the reel, it moves from one side of the reel to the other (side to side). 
         [0003]    Residual bend exists in every coiled tubing string. During storage and transportation, a coiled-tubing string is plastically deformed (bent) as it is spooled on a reel. During operations, the tubing is unspooled (bent) from the reel and bent on the gooseneck before entering into the injector and the wellbore. Residual bending is one of the technical challenges for coiled tubing operations and originates from the spool of the coiled tubing on the reel. Although the reel is manufactured in a diameter as large as possible to decrease the residual bending incurred on the coiled tubing, the maximum diameter of many reels is limited to several meters due to storage and transportation restrictions. 
         [0004]    Coiled tubing is susceptible to a condition known as helical buckling of the tubing which leads to lockup. Residual bending of the coiled tubing increase the susceptibility of the coiled tubing to helical buckling and lockup. As the coiled tubing goes through the injector head, it passes through a straightener; but the tubing retains some residual bending strain corresponding to the radius of the spool. That strain gives the tubing a helical form when deployed in a wellbore and can cause it to wind axially along the wall of the wellbore like a long, stretched spring. Ultimately, when a long enough length of coiled tubing is deployed in the well bore, frictional forces from the wellbore wall rubbing on the coiled tubing cause the tubing to bind and lock up, thereby stopping its progression. Lock up limits any further progression as the coiled tubing cannot be pushed further by a force applied at the surface. (Lubinski, A., Althouse, W. S., and Logan, J. L., “Helical Buckling of Tubing Sealed in Packers,” SPE 178, 1962). Such lock up limits the use of coiled tubing as a conveyance member for logging tools in highly deviated, horizontal, or up-hill sections of wellbores. Therefore, reducing the residual bending of the coiled tubing before the coiled tubing is placed into the wellbore can increase the extended reach of the coiled tubing (Zheng, A. and Adnan, S., “The Penetration of Coiled Tubing with Residual Bend in Extended-Reach Wells,” SPE 95239, 2007). Residual bending also decreases the fatigue life for coiled tubing, therefore, reducing residual bending will thus increase the fatigue life of coiled tubing (Bhalla, K., “Coiled Tubing Extended Reach Technology,” SPE 30404, 1995). Fatigue failure of coiled tubing is a serious concern because of plastic deformation caused by repeated bending on the reel and gooseneck. 
         [0005]    Coiled tubing passing downward (generally running-in hole) undergoes at least three straining events: 1) as the coiled tubing is straightened upon leaving the reel and on approach to the gooseneck; 2) as the coiled tubing is curved over the gooseneck; and 3) as the coiled tubing is straightened on its way from the gooseneck to the injector head. Similarly, coiled tubing passing upward (generally pulling-out-of-hole) undergoes at least three straining events: 1) as the coiled tubing is extracted from the wellbore and curved over the gooseneck; 2) as the coiled tubing is straightened upon leaving the gooseneck and on approach to the reel; and 3) as the coiled tubing is being curved onto the reel. These strains in coiled tubing may cause residual bend in the tubing which may prevent it from straightening properly in the borehole or rolling properly on the reel. 
         [0006]    Residual bending is reduced by the straightener. The straightener applies compressive forces around the coiled tubing before the coiled tubing is placed into the wellbore, straightening the coiled tubing and reducing some of the residual bending in the coiled tubing. However, the tubing retains some residual bending. Furthermore, the straightener is unable to reduce fatigue of the coiled tubing or elongate the life cycle of the coiled tubing. 
         [0007]    Mueller et al, (U.S. Pat. No. 5,291,956) proposes a method for reducing the residual bending using a pulley. However, the pulley has a diameter near to the diameter of the reel and occupies additional space for the coiled tubing unit. 
         [0008]    The presently disclosed subject matter addresses the problems of the prior art by addressing residual bending and fatigue of the coiled tubing. The presently disclosed subject matter reduces residual bending and fatigue of the coiled tubing, which assists in extending the maximum reach of the coiled tubing in the wellbore and the life cycle of the coiled tubing respectively. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    In view of the above there is a need for an improved mechanism which reduces residual bending in coiled tubing. Further there is a need for an improved mechanism to reduce fatigue of the coiled tubing and elongate the life cycle. The subject technology accomplishes these and other objectives. The subject disclosure provides a method of reducing residual bending and fatigue in the coiled tubing by utilizing a reel and gooseneck. The subject disclosure discloses a gooseneck that provides an opposite bending moment to reduce the residual bending in the coiled tubing as a result of the reel. Further, the subject disclosure discloses a gooseneck having an adjustable radius during the coiled tubing operations which optimizes the residual bending reduction process. The subject disclosure also discloses a heating and cooling module. The heating and cooling modules are attached to the gooseneck and are utilized to increase the efficiency of the residual bending process and reduce fatigue of the coiled tubing. 
         [0010]    In accordance with an embodiment of the subject disclosure, an apparatus for reducing residual bending in coiled tubing is disclosed. A gooseneck is positioned to receive the coiled tubing from the coiled tubing reel and once positioned reverse bends the coiled tubing to an extent sufficient to remove residual bend resulting from the coiled tubing being coiled on the reel. 
         [0011]    In accordance with a further embodiment of the subject disclosure, a method for reducing residual bend from a reel is disclosed. A gooseneck is positioned to reverse bend the coiled tubing sufficiently to remove residual bend resulting from the coiled tubing being coiled on the reel. 
         [0012]    Further features and advantages of the subject disclosure will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0013]      FIG. 1  shows the coiled tubing operating environment for the subject disclosure; 
           [0014]      FIG. 2  represents a coiled tubing unit having a hydraulically operated tubing reel and shows the bending events that coiled tubing undergoes while moving from the coiled tubing reel to the main injector; 
           [0015]      FIG. 3  illustrates one embodiment of the subject disclosure; 
           [0016]      FIG. 4  illustrates a second embodiment of the subject disclosure; 
           [0017]      FIG. 5  illustrates the embodiment of  FIG. 1  with a heating and cooling module; 
           [0018]      FIG. 6  illustrates the embodiment of  FIG. 2  with a heating and cooling apparatus; 
           [0019]      FIG. 7  illustrates a gooseneck having an adjustable radius of curvature; and 
           [0020]      FIG. 8  is the bending moment M—curvature 1/ρ curve of coiled tubing under elastically-perfectly plastic deformation. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Embodiments of the present technology comprise a reel and a gooseneck which significantly reduce residual bending of the coiled tubing. 
         [0022]    In  FIG. 1  the operating environment of the subject disclosure is shown. Coiled tubing operation comprises a truck  103  and/or trailer  109  that supports power supply  105  and tubing reel  107 . An injector unit head  111  feeds and directs coiled tubing  113  from the tubing reel into the subterranean formation. The configuration of  FIG. 1  shows a horizontal wellbore configuration which supports a coiled tubing trajectory  115  into a horizontal wellbore  117 . The subject disclosure is not limited to a horizontal wellbore configuration but may also be used in vertical and deviated wells, both on land and offshore. Downhole tool  119  is connected to the coiled tubing, as for example, to conduct flow or measurements, or perhaps to provide diverting fluids. 
         [0023]      FIG. 2  depicts a coiled tubing assembly  211 . The coiled tubing assembly  211  is composed of coiled tubing  203 , reel  201  and a gooseneck  205 . When the coiled tubing assembly is run into the wellbore the coiled tubing  203  spooled onto the reel  201  is unwound first and then delivered through a levelwind assembly  212  and a coiled tubing brake  214  in a controllable way. The coiled tubing spooled on the reel  201  is plastically deformed, resulting in residual bending in the coiled tubing. The forces and strains placed upon coiled tubing when it is used in a coiled tubing unit  211  are apparent from viewing  FIG. 2 . Coiled tubing undergoes numerous bending events each time it is run into and out of a wellbore. Coiled tubing  203  is straightened when it emerges from the reel by way of the levelwind assembly  212 . A levelwind assembly for a coiled tubing reel guides coiled tubing onto a reel when the coiled tubing is removed from an oil or gas well and guides coiled tubing from the reel when the coiled tubing is injected into an oil or gas well. Levelwind assemblies are known to those skilled in the art. One such levelwind assembly is describe in U.S. Pat. No. 6,264,128, entitled “Levelwind Assembly for Coiled Tubing Reel”, incorporated herein in its entirety by reference. Coiled tubing brake  214  on the levelwind assembly  212  is shown. The coiled tubing  203  is guided by the gooseneck  205 , and is straightened as it goes into the injector head  207  for entry into the wellbore. Of course, each bending event is repeated in reverse when the tubing is later extracted from the wellbore. These bending events weaken the tubing each time it is used, and tubing use must be monitored. Tubing is discarded when it has been used beyond an acceptable safety limit as indicated by reaching predicted fatigue limits. The coiled tubing, typically made of steel, is plastically deformed every time it is spooled off the reel, bent over the gooseneck, straightened through the chains, and in the reverse process. It is known that the fatigue resistance of steel is severely degraded when it is plastically deformed. Residual bending in the coiled tubing  203  is not reduced when the coiled tubing  203  is guided by the gooseneck  205 . When the coiled tubing  203  slides through the injector head  207 , the injector head  207  exerts a compressive force around the coiled tubing which straightens the coiled tubing. Finally, after the coiled tubing is straightened by the injector head  207 , the residual bending in the coiled tubing  209  is reduced before the coiled tubing  209  is run into the wellbore. 
         [0024]      FIG. 3  show a reel  301  of coiled tubing  305  stored on a drum in a clockwise direction  309 . As the coiled tubing  305  slides through the gooseneck  303  the coiled tubing  305  unwinds in a counter-clockwise direction  311 , and continues unwinding in a counter-clockwise direction  311  as it is placed into a wellbore (not shown). The reel  301  spooled with coiled tubing  305  rotates in a clockwise direction  309  while the coiled tubing  305  is guided by the gooseneck  303  in a counter-clockwise direction  311  when the coiled tubing is run into a wellbore. Once the coiled tubing  305  leaves the reel  301 , the residual bending existing in the coiled tubing  305  is compensated by an opposite bending moment exerted by the gooseneck  303  and the residual bending in the coiled tubing  307  is reduced. The opposite bending moment means the sign of the bending moment M is different, i.e. clockwise or anti-clockwise. Once the coiled tubing  305  has travelled through the gooseneck  303 , residual bending in the coiled tubing  305  will be significantly reduced. Residual bending of the coiled tubing is significantly reduced as a result of the reverse unwinding of the coiled tubing, in this instance in a counter-clockwise direction. The radius profile of the gooseneck  303  is adjustable during the coiled tubing operation for optimal reduction of residual bending. 
         [0025]      FIG. 4  shows a reel  401  of coiled tubing  403  stored on a drum in a counter-clockwise direction  411 . The reel  401  spooled with coiled tubing  403  rotates in a counter-clockwise direction  411  and the coiled tubing is guided by a first section of the gooseneck  409  in the same counter-clockwise direction when running the coiled tubing into well. A second section of the gooseneck  407  enables rotation of the coiled tubing in a clockwise direction  415 . The coiled tubing  403  enters a first section  409  of the gooseneck in a counter-clockwise direction  413 . The gooseneck further comprises a second section  407 . The coiled tubing  403  enters in a clockwise direction  415  into the second section  407  of the gooseneck. The residual bending existing in the coiled tubing  403  is compensated by an opposite bending moment exerted by the second section  407  of the gooseneck on the coiled tubing  403  and the residual bending in the coiled tubing  405  is reduced. Once the coiled tubing moves through the second section  407  of the gooseneck the residual bending in the coiled tubing  403  will be significantly reduced. The radius profile of the second section  407  of the gooseneck is adjustable for optimal reduction of residual bending. 
         [0026]      FIG. 5  illustrates the schematic of  FIG. 3  further comprising a heating and cooling module.  FIG. 5  depicts a reel  505  of coiled tubing  507  stored on a drum in a clockwise direction  513 . A heating module  503  is attached to the gooseneck  501  and a cooling module  509  surrounds the coiled tubing  507 . The heating module  503  heats the coiled tubing  507  and enables the residual bending reduction process in a high temperature. In certain non-limiting examples the temperature may reach 600° C. A high temperature increases the efficiency of reducing residual bending and reducing fatigue of the coiled tubing  507 . The cooling module  509  controls the temperature of the coiled tubing  507  ensuring the high temperature is in an area close to the gooseneck  501 . Thus, the cooling module  509  confines the high temperature of the coiled tubing  507  to a region close to the gooseneck  501 . 
         [0027]      FIG. 6  illustrates the schematic of  FIG. 4  further comprising heating and cooling modules.  FIG. 6  depicts a reel  609  of coiled tubing  613  stored on a drum in a counter-clockwise direction  615 . A heating module  603  is attached to a second section  603  of gooseneck and a cooling module  605  surrounds the coiled tubing  613  on either end of the gooseneck  601 . Similar to the embodiment of  FIG. 5  the heating module  603  heats the coiled tubing  605  and enables the residual bending reduction process in a high temperature. A high temperature increases the efficiency of reducing residual bending and reducing fatigue of the coiled tubing  605 . The cooling module  605  controls the temperature of the coiled tubing  605  ensuring the high temperature is in an area close to the second section  611  of the gooseneck. Thus, the cooling module  605  confines the high temperature of the coiled tubing  613  to a region close to the area of the second section  611  of the gooseneck. 
         [0028]    The configuration of the gooseneck  303  and the second section of the gooseneck  407  are adjustable during an individual coiled tubing operation or multiple coiled tubing operations. For the individual coiled tubing operation, the configuration of the gooseneck  303  or  407  changes as different locations of the coiled tubing are guided by the gooseneck  303  or  407 . The magnitude of the residual bending of the coiled tubing varies depending on the location of the coiled tubing on the reel. The coiled tubing spooled on the outside of the reel experiences less plastic deformation than the coiled tubing spooled on the inner side of the reel. The radius of curvature of the gooseneck  303  or  407  may be adjusted from a large curvature to a smaller curvature as more coiled tubing is unwound from the reel when the coiled tubing is run into the wellbore. 
         [0029]    For the multiple coiled tubing operations, the configuration of the gooseneck  303  or  407  changes as the diameter of the reel changes. The magnitude of the residual bending of the coiled tubing varies depending on the diameter of the reel. The coiled tubing spooled on large reels experiences less plastic deformation than the coiled spooled on smaller reels. The radius of curvature of the gooseneck  303  or  407  is adjusted to a larger radius if the coiled tubing is spooled on a larger reel. The radius of curvature of the gooseneck  303  or  407  is adjusted to a smaller radius if the coiled tubing is spooled on a smaller reel. 
         [0030]      FIG. 7  schematically illustrates a gooseneck  701  with an adjustable radius of curvature. The gooseneck has the largest radius of curvature when segment  714 , segment  715 , segment  716 , and the plurality of other segments (not listed) are expanded. Joint  713  is fixed on the segment  714 . Joint  705  and joint  709  are fixed on the gooseneck base  703 . When the radius of curvature of the gooseneck decreases, segment  715  collapses into segment  714 . At the same time, upper supporting arms  711  rotate around joint  713  and lower supporting arms  707  rotate around joint  705  and joint  709  to achieve a new balanced position. When the radius of curvature of the gooseneck further decreases, segment  716  also collapses into segment  714 , upper arms  711  and lower arms  707  change their positions accordingly, to a different balanced position. One skilled in the art will appreciate that adjusting the radius of curvature can be accomplished using many other techniques known to those skilled in the art and not described in the subject disclosure. 
         [0031]    The significance of the residual bending can be described quantitatively by using bending strain. The maximum magnitude of the bending strain ε max  in a given pipe cross-section usually occurs on the outside of the pipe. The radius of the reel is ρ 0  and the coiled tubing outside diameter is D o . When the number of the loops of the coiled tubing spooled on the reel is n, the curvature ρ of the coiled tubing of the i th  loop is: 
         [0000]      ρ=β 0   +i·D   o ( i= 1, 2  . . . n )  (1)
 
         [0000]    The relationship between the maximum bending strain ε max , curvature 1/ρ, and the pipe outside diameter D o  is: 
         [0000]      |ε max |=|( D   o /2)(1/ρ)|  (2)
 
         [0000]    As can be seen from Eq. (2), the residual bending is significant when the pipe outside diameter D o  is large and the radius ρ is small. As can be seen from Eq. (1), the radius ρ is small when the radius of the reel ρ o  is small and the number of the loops n is small. 
         [0032]      FIG. 8  depicts the bending moment M—curvature (ρ) of a pipe undergoing a series of deformations. In a non-limiting example this pipe may be a portion of coiled tubing. The material is assumed to be elastically-perfectly plastic. In a first deformation from A to B the pipe undergoes linear elastic bending. Further bending from B to C results in deformation which is elastic-plastic, this means that some parts of a cross-section are deforming plastically and some parts of a cross-section are deforming elastically. The deformation from A to C may be representative of placing a straight coiled tubing string onto a reel. The pipe unloads elastically from C-D, the curvature at D would be the residual bend if no further deformation occurred e.g. if a coiled tubing was unwound from the reel without a straightening process. If the pipe is then straightened, the deformation will unload elastically from D to E and then elastically-plastically from E to F. At F, the pipe will be straight. If the pipe then unloads elastically, it will proceed from F to G and have a residual bend shown by the curvature at G. If the pipe is then reverse-bent, the deformation will proceed from F to G′, with further elastic-plastic deformation. Upon unloading elastically from G′, the pipe returns to the initial state A with no residual bend, providing G′ has been selected appropriately. In one non-limiting example G′ would be estimated by reverse bending to the same curvature as seen at G, i.e. reverse bending by the same amount as the residual curvature if in the absence of the reverse bend operation. 
         [0033]    Reverse bending may also occur elsewhere in the coiled tubing e.g. injector. Although the embodiments of the subject disclosure have been described with respect to coiled tubing, the mechanisms disclosed may reduce residual bending of tubing in general. 
         [0034]    While the subject disclosure is described through the above exemplary embodiments, it will be understood by those of ordinary skill in the art that modification to and variation of the illustrated embodiments may be made without departing from the inventive concepts herein disclosed. Moreover, while the preferred embodiments are described in connection with various illustrative structures, one skilled in the art will recognize that the system may be embodied using a variety of specific structures. Accordingly, the subject disclosure should not be viewed as limited except by the scope and spirit of the appended claims.