Abstract:
A handheld tool for straightening coiled tubing in a continuous manner. The tool is configured to straighten coiled tubing that has undergone plastifying deformation, for example, during winding about a coiled tubing reel. The tool is of enhanced mobility and may be employed to provide a straightened portion of coiled tubing without resorting to intermittent reverse kinking or corrugating of the coiled tubing. Rather, the substantially continuous character of the straightened portion of coiled tubing is well suited for stably and reliably accommodating a downhole tool for use within a well during hydrocarbon recovery applications.

Description:
FIELD 
     Embodiments described relate to coiled tubing applications in hydrocarbon wells. In particular, embodiments for dealing with residual bend in plastically deformed coiled tubing are detailed. 
     BACKGROUND 
     Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As such, tremendous emphasis is often placed on well access in the hydrocarbon recovery industry. That is, access to a well at an oilfield for monitoring its condition and maintaining its proper health is of great importance. As described below, such access to the well is often provided by way of coiled tubing. 
     Coiled tubing may be configured to deliver interventional or monitoring tools downhole and it may also accommodate fluid through its interior for a host of downhole applications. Furthermore, coiled tubing is particularly well suited for being driven downhole, to depths of perhaps several thousand feet, by an injector at the surface of the oilfield. Thus, with these characteristics in mind, the coiled tubing will also generally be of sufficient strength and durability to withstand such applications. For example, the coiled tubing may be of stainless steel or other suitable metal based material. 
     In spite of being constructed of a relatively heavy metal based material, the coiled tubing is plastically deformed and wound about a drum to form a coiled tubing reel. In this manner, the coiled tubing may be manageably delivered to the oilfield for use in a well thereat. Once positioned at the oilfield, the coiled tubing may be unwound from the reel and directed through the well by way of the noted injector equipment at the oilfield surface. However, due to the noted plastifying deformation, a residual bend is left in the coiled tubing as it is unwound for use. For certain applications, this residual bend may pose a problem. For example, in the case of highly deviated wells or extended reach wells of tens of thousands of feet in depth, it is likely that the bend in the coiled tubing will eventually result in helical locking up of the coiled tubing. Ultimately, this lock up will prevent the injector from driving the coiled tubing any further through the well. Thus, the coiled tubing may fail to reach the application site in the well. 
     In order to prevent helical lock up of coiled tubing in applications run in deviated or deep wells, the injector may be specially fitted with a reverse bend mechanism. The reverse bend mechanism may be a large heavy tool that is integrated into the body of the injector and configured to bend the coiled tubing in a manner opposite the plastifying deformation bend noted above. Thus, several thousand feet of coiled tubing may be straightened as it is run through the injector and driven downhole for the application. 
     Additionally, for many downhole applications, such as those targeting shallower depths in relatively vertical wells, the bent end of the coiled tubing may be problematic even though helical lock up may be of no significant concern. In such circumstances, the addition of a large and expensive reverse bend mechanism to the injector may accomplish little more than add to the weight and expense of equipment brought to the worksite. 
     Given the difficulty that a user encounters in feeding the bent end of the coiled tubing into the injector, a mobile, handheld reverse kinking mechanism is often employed by the user. The reverse kinking mechanism may be employed to reduce the amount of bend at the end of the coiled tubing thereby allowing the user to more easily feed the coiled tubing into the injector. For example, the user may slide the end of the coiled tubing through the mechanism a given amount and activate the mechanism. Activation of the mechanism involves physically inducing a kink, opposite the direction of the bend. This may be repeated in several isolated locations until the relatively uniform curvature at the end of the coiled tubing is replaced with a series of kinks that leave a repeating ‘w’ or corrugated appearance. While such ‘straightening’ is discontinuous and thus, not entirely straight, the now corrugated end of the coiled tubing may be easier for the user to manipulate and feed into the injector. 
     Unfortunately, corrugating the end of the coiled tubing with a reverse kinking mechanism as described above may still leave a difficult to manage coiled tubing end in certain regards. That is, while perhaps sufficient for feeding the injector, the user may deal with the end of the coiled tubing for a host of other reasons, some of which may call for a straighter coiled tubing end than the reverse kinking mechanism is able to provide. For example, a tool-string or even individual tools may be secured to the end of the coiled tubing for performance of monitoring and/or well intervention applications in the well. Securing such devices properly to the end of the coiled tubing may be critical to ensuring that the application is properly run without damage to, or loss of the devices. While the degree of bend may be reduced by the reverse kinking mechanism, in circumstances where the remaining bend in the coiled tubing end prevents a physically secure coupling of devices thereto, the user is placed in an unenviable predicament. That is, the user may be left with having to choose between risking device loss and having to re-run the application versus running the entire coiled tubing application through an otherwise unnecessary, more expensive and less available injector with incorporated reverse bend mechanism. 
     SUMMARY 
     A mobile tool for straightening a portion of coiled tubing is provided. The tool includes first and second rollers for positioning against one side of the coiled tubing. An additional intermediate roller is provided for positioning against a second opposite side of the coiled tubing. This intermediate roller is disposed between the first and second rollers and adjustably positionable relative thereto for the straightening of the portion of the coiled tubing. 
     A mobile tool for straightening a portion of coiled tubing may be provided that is made up of two separate frame portions. The first frame portion may accommodate an intermediate roller and a first opposite roller, whereas the second frame portion may accommodate a second opposite roller. The second frame portion may be coupled to the first frame portion for pivoting relative thereto. The portion of the coiled tubing may be disposed between the intermediate roller and the opposite rollers to allow the pivoting to effect the straightening. 
     A method of straightening a portion of coiled tubing is also disclosed. In one embodiment a mobile handheld tool may be provided with first and second rollers located at a side thereof and an intermediate roller located at another side thereof and between the first and second rollers. The portion of the coiled tubing may be inserted within the mobile handheld tool between the sides. Thus, a position of the intermediate roller relative to the first and second rollers may be adjusted for the straightening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an embodiment of a mobile coiled tubing (CT) straightening tool employed in straightening coiled tubing. 
         FIG. 2  is a side cross-sectional view of the mobile CT straightening tool and coiled tubing taken from  2 - 2  of  FIG. 1 . 
         FIG. 3  is an overview of an oilfield having a well for access by the coiled tubing upon straightening by the mobile CT straightening tool of  FIG. 1 . 
         FIG. 4A  is an enlarged view of the end of the coiled tubing with mobile CT straightening tool thereabout taken from  4 - 4  of  FIG. 3 . 
         FIG. 4B  is an enlarged view of the end of the coiled tubing of  FIG. 4A  having a straightened portion for coupling to a downhole tool. 
         FIG. 5  is a flow-chart summarizing an embodiment of straightening a bent end of coiled tubing. 
         FIG. 6  is an overview of the oilfield of  FIG. 3  with the well accommodating a downhole tool secured to a straightened portion of the end of the coiled tubing. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of mobile coiled tubing straightening tools are described with reference to certain coiled tubing applications herein. As such, certain configurations of coiled tubing and downhole tools are depicted. For example, a coiled tubing operation employing a perforation gun is shown in certain figures. However, a variety of other downhole tools may be utilized in conjunction with coiled tubing that is straightened by the straightening tool. Regardless, embodiments of the straightening tool may be handheld and provide substantially continuous straightening to allow for a secure coupling of a downhole tool to a straightened end of the coiled tubing. 
     Referring now to  FIG. 1 , an embodiment of a mobile coiled tubing straightening tool  100  is depicted. The straightening tool  100  is shown straightening a section of coiled tubing  110 . That is, as depicted, bent coiled tubing (B) may be inserted into the straightening tool  100  at the left side thereof. The tool  100  may then be adjusted as detailed herein and advanced leftward relative to the coiled tubing  110 . As such, straightened coiled tubing (S) may be emitted from the right side of the tool  100 . The straightening tool  100  is particularly user-friendly and beneficial in that it may be relatively lightweight and handheld or hand carried to a worksite. Furthermore, the tool  100  is equipped with a powered intermediate roller  150  to allow continuous straightening of the coiled tubing  110 . Thus, unlike conventional handheld coiled tubing straightening devices, the entirety of the coiled tubing  110  which passes through the tool  100  may be straightened (e.g. as the depicted straightened coiled tubing (S) reveals). 
     Continuing with reference to  FIG. 1 , the straightening tool  100  is equipped with first  140  and second  180  passive rollers. The central portions of these rollers  140 ,  180 , along with the above-noted intermediate roller  150 , are concavely shaped to correspondingly accommodate the coiled tubing  110  as shown. Additionally, the passive rollers  140 ,  180  are positioned at an opposite side of the body of the tool  100  relative to the intermediate roller  150 . In the embodiment shown, these rollers  140 ,  180  are passive in the sense that they are configured to passively rotate about passive hubs  145 ,  185  while guiding and supporting movement of the coiled tubing  110  from left to right as depicted. It is the powered intermediate roller  150  on the other hand which is configured to drive the noted movement of the coiled tubing  110 . However, in alternate embodiments, rollers  140 ,  180  aside from the intermediate roller  150  may similarly be directly powered. 
     Powering of the intermediate roller  150  may be achieved through coupling an external power source to the power hub  155 . For example, in the embodiment shown, the power hub  155  is equipped with a mechanical drive shaft or socket  167  for receiving a manual, pneumatic or hydraulic wrench. Once coupled to the socket  167 , the wrench may be employed to rotate the hub  155  and roller  150  in a counterclockwise direction (see arrow  250  of  FIG. 2 ). As such, the coiled tubing  110  may be forced from left to right as described above. 
     Moving the coiled tubing  110  from left to right results in straightening as described above. As detailed further below, this is due to the fact that the powered roller  150  and the passive rollers  140 ,  180  are shifted from an initial position of loosely receiving bent coiled tubing (B) (as depicted in  FIG. 4A ), to a position of induced deflection as shown in  FIG. 1  (also see  FIG. 2 ). In the position of induced deflection, all of the coiled tubing  110  from the location of the powered roller  150  to the right end as shown, is actually reverse bent and deflected upward by the roller  150 . The amount of reverse bending or deflection is determined based roughly on the calculated amount necessary to overcome the plastic deformation originally induced in the coiled tubing  110  (e.g. during placement about a coiled tubing reel  310  for delivery to the oilfield  375  as shown in  FIG. 3 ). Overcoming such induced plastic deformation results in the straight coiled tubing (S) as shown. 
     In the embodiment of  FIG. 1 , shifting of the powered  150  and passive  140 ,  180  rollers relative to one another is achieved through use of separate frames  125 ,  175  which are pivotally coupled to one another at a pivot joint  130 . However, other mechanisms may be employed to achieve such relative change in roller positioning. Nevertheless, as depicted, the intermediate roller  150  and a first passive roller  140  are accommodated by a first frame  125 , whereas the second passive roller  180  is alone accommodated by a second frame  175 . Due to the presence of the pivot joint  130 , the second passive roller  180  may initially be in a loose position with the second frame  175  deflected away from the face  165  of the first frame  125  as shown in  FIG. 4A . The second frame  175  may then subsequently be pivoted into closer range of the face  165  as depicted in  FIG. 1 . In this manner, the position of the second passive roller  180  may be tightened and the initial deflection or reverse bend in the coiled tubing  110  initiated as detailed further below with respect to  FIG. 2 . Additionally, with rotation of the powered roller  150  as noted above, this reverse bending may continue beyond the initial isolated reverse bend location, thereby resulting in a continuous straightening of the coiled tubing  110  as described. 
     Control over movement of the second frame  175  toward the first  125  about the pivot joint  130  as described above, may be achieved by way of an adjustment mechanism  195 . As shown in  FIG. 1 , the adjustment mechanism  195  may be a conventional bolt which is securely located through a block mount  197  of the second frame  175  and threaded into a block mount  160  of the first frame  125 . As such, turning of the mechanism  195  may be employed to position the second frame  175  relative the first  125 , for example, moving the second frame  175  closer to the face  165  of the first  125  to begin the straightening process. 
     The second frame  175  may also be equipped with a guidance mechanism  190  to limit the degree of movement which may be achieved by way of the adjustment mechanism  195 . In this manner, overcorrected bending of the coiled tubing  110  may be avoided. As shown, the guidance mechanism  190  may again be a conventional bolt. In this case, however, the mechanism  190  may be threaded through a retainer  192  of the second frame  175  only. That is, rather than adjustably coupling to the first frame  125 , the guidance mechanism  190  may act as a stop, merely abutting the face  165  of the first frame  125 . Thus, the guidance mechanism  190  may prevent further tightening of the second frame  175  relative the first  125  once the appropriate calculated distance therebetween has been achieved. Thus, the unintended formation of any new bent portion of coiled tubing  110  may be avoided. As detailed further herein below, effectively calculating such a distance and setting the positioning of the guidance mechanism  190  may be determinative of the overall degree of straightening of the coiled tubing  110  that is ultimately achieved. 
     Continuing now with added reference to  FIG. 2 , a cross-sectional view of the straightening tool  100  about the coiled tubing  110  is depicted. In particular, the described tightening of the second roller  180  reveals the force (F) that is imparted by the powered roller  150  on the coiled tubing  110 . As shown, his downward force (F) induces a certain amount of reverse bend or upward deflection (D). From the perspective of a central axis  200  through the coiled tubing  110 , a bent axis portion (B′) may be converted to a straightened axis portion (S′) from a location  250  immediately adjacent the powered roller  150 . This straightening may move beyond a mere reverse kink at an isolated location. That is, the straightening tool  100  may be employed in a continuing manner, with the straightened axis portion (S′) extending as the powered roller  150  rotates counterclockwise (see arrow  250 ) and the passive rollers  140 ,  180  rotate clockwise (see arrows  240 ,  280 ). 
     Continuing with reference to  FIGS. 1 and 2 , with added reference to  FIG. 3 , a more specific example of straightening of coiled tubing  110  is described here with reference to rough calculations for achieving the straightening. For example, consider a conventional steel-based coiled tubing  110  with an outer radius of about 2 ⅞ inches and a wall thickness of about 0.19 inches. From a reel  310 , it would not be uncommon to see such a coiled tubing  110  with a significant bend radius, perhaps about 380 inches. Thus, in order to allow for reliable coupling of a downhole tool  360  to the coiled tubing  110 , the end thereof may be straightened as described herein. 
     Given a coiled tubing  110  as noted above, the amount of deflection for effective straightening may be roughly calculated according to the following equation.
 
Δ x =(σ/ R   o ) ( l   2 /12 E )
 
In this case Δx is the deflection or displacement that is roughly employed to achieve straightening, whereas σ represents the plastifying yield stress of the coiled tubing  110 , R o  its outer radius, l the length (l) between the passive rollers  140 ,  180  as depicted in  FIG. 2 , and E is the modulus of elasticity found in the coiled tubing material. Thus, with particular reference to the straightening tool  100  and the coiled tubing dimensions and materials noted above, it would be feasible to see values such as 80,000 psi for the plastifying yield stress (σ), 1.4375 inches for the outer radius (R o ) of the coiled tubing  110 , about 20 inches for the length (l) between the passive rollers  140 ,  180 , and 30 million psi as the modulus of elasticity (E).
 
     Running the calculations with such values as those noted above would result in a displacement (Δx) of about 0.062 inches in order to achieve straightening as depicted in  FIGS. 1 and 2 . Thus, based on predetermined dimensional criteria, the guidance mechanism  190  may be set to allow no more than 0.062 inches of deflection, the straightening tool  100  loosely positioned over the end of the coiled tubing  110 , and the adjustment mechanism  195  tightened until the guidance mechanism  190  meets the face  165  of the first frame  125 . At this time, an isolated location of straightening may be obtained that may then be extended through the coiled tubing  110  as the powered roller  150  is rotated as described herein. 
     With particular reference to  FIG. 3 , an overview of an oilfield  375  is shown. In this depiction, the value of having available a handheld straightening tool  100  of less than about 25 inches in length may be appreciated in a practical sense. As shown, the coiled tubing  110  is plastically deformed about a coiled tubing reel  310  and delivered to the oilfield  375  by way of a coiled tubing truck  325 . The truck  325  is positioned adjacent interventional surface equipment  300  and a well  385  to be accessed by the coiled tubing  110 . In the embodiment shown, well access by the coiled tubing  110  is utilized in order to deliver a downhole tool  360  through the well  385  to a relatively shallow dowhole location adjacent a formation  390  as described further with reference to  FIG. 6 . Given that the coiled tubing  110  is to accommodate a downhole tool  360 , the lightweight mobile straightening tool  100  may be manually positioned at the end of the tubing  110  and employed as described above. 
     With added reference to  FIGS. 4A and 4B , straightening of the coiled tubing  110  and coupling of the downhole tool  360  thereto is described.  FIG. 4A  in particular is an enlarged view of the straightening tool  100  as it is initially loosely positioned over the end of the coiled tubing  110 . By way of comparison to  FIG. 1 , the second frame  175  is relatively more distanced from the first frame  125  about the pivot joint  130 . Note the longer appearance of the adjustment mechanism  195 . Thus, all of the rollers  140 ,  150 ,  180  may stably interface the coiled tubing  110 , yet without, at this point, deformably effecting straightening as detailed hereinabove. Nevertheless, once positioned, straightening techniques employing the straightening tool  100  may ensue as described above. 
     Ultimately, as depicted in  FIG. 4B , straightened coiled tubing (S) may be provided that is mechanically well suited for coupling to a downhole tool  360 . In the embodiment shown, the straightening tool  100  may be particularly advantageous for use where coupling of a downhole tool  360  is of primary concern with regard to straightening. For example, as shown in  FIG. 4B , the coiled tubing  110  is left with both bent coiled tubing (B) and the noted straightened coiled tubing (S). However, given the shallow depth of the application to be run with the coiled tubing  110 , the value of straightening lies primarily in the stable securing of the downhole tool as opposed to say avoiding downhole helical lock-up of the coiled tubing  110 . Thus, bent coiled tubing (B) may be of no significant concern so long as the end of the coiled tubing is straightened. As such, the need for a conventional expensive, heavy, and comparatively immobile straightening tool incorporated into the body of the coiled tubing injector  350  may be obviated. 
     In addition to coupling of the downhole tool  360 , the straightened coiled tubing (S) may present well for coupling of other devices. For example, another section of coiled tubing may be more easily coupled to the straightened coiled tubing (S) by way of a coupling collar, welding, or another mechanism adjoining the tubings. That is, the straightening tool  100  may be employed in order to extend the length of coiled tubing for an operation in a user friendly manner by straightening the ends of separate coiled tubing sections which may then be adjoined via a coupling collar, weld or mechanism as noted. 
     Referring now to  FIG. 5 , a method of employing an embodiment of a straightening tool is summarized in the form of a flow chart. That is, the tool may be loosely positioned over the end of coiled tubing as indicated at  515 . As shown at  535 , the position of rollers of the tool may then be adjusted relative to one another in order to initiate straightening at a given location of the tubing. One of the rollers may then be powered to rotate as noted at  550 , thereby extending reverse bend over a continuous length of the coiled tubing to provide straightening. With the straightened portion of coiled tubing available, a downhole tool may be coupled thereto as indicated at  580 . Additionally, as indicated at  565 , depending on physical characteristics of the downhole tool, it may be coupled to the straightened portion of the coiled tubing after the tubing is run through a coiled tubing injector. 
     Referring now to  FIG. 6 , the downhole tool  360  is depicted as a perforation gun for forming perforations  600  into the formation  390  adjacent the well  385 . Such techniques may be pursued to aid in hydrocarbon recovery from the formation  390 . Regardless, the location of the perforations  600  is relatively shallow. Thus, the primary concern presented by a plastically deformed and bent coiled tubing  110  relates to securing of the downhole tool  360  thereto, as opposed to avoiding downhole helical seizure of the tubing. Thus, a lightweight, handheld mobile coiled tubing straightening tool  100  as depicted and described with reference to  FIGS. 1-4  may be employed to ensure coiled tubing straightening sufficient for adequate security of the downhole tool  360 . 
     Embodiments described hereinabove provide a coiled tubing straightening tool and techniques for straightening coiled tubing that are user-friendly and effective. The straightened coiled tubing may be continuously straightened without intermittent curvature or corrugated dimensions. Thus, security of a downhole tool coupled to the straightened portion of coiled tubing may be enhanced. Furthermore, the continuous straightening may be provided by way of a handheld, mobile, relatively inexpensive straightening tool. 
     The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.