Abstract:
The present invention generally relates to a connector arrangement for connecting a first tubular to a second tubular. In particular, the present invention relates to methods and apparatus for connecting the tubulars in such a way that the connection is prevented from becoming unmade in response to expansion of the tubulars. A connector mechanically mates a box end and a pin end of the tubulars together to form the connection. Additionally, mating castellations, surface finishes on the pin end and the box end, torque screws, and a variable pitch groove can provide resistance to relative rotation between the tubulars at the connection.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to tubular connections. In particular, the present invention relates to a method of connecting tubulars in such a way that the connection is prevented from becoming unmade in response to expansion of the tubulars. More particularly, the present invention relates to tubular connections that use a connector to mechanically mate a box end of a first tubular with a pin end of a second tubular. 
     2. Description of the Related Art 
     In order to access hydrocarbons in subsurface formations, it is typically necessary to drill a bore into the earth. The process of drilling a borehole and of subsequently completing the borehole in order to form a wellbore requires the use of various tubular strings. These tubulars are typically run downhole where the mechanical and seal integrity of the jointed connections are critically important in the original make-up of the tubulars, during expansion of the tubulars, and after expansion of the tubulars. 
     Typically threaded connections are used to connect multiple tubular members end-to-end. This is usually accomplished by providing tubulars that have a simple male to female threaded connection. The male end is generally referred to as a pin, and the female end as a box. The tubulars are connected, or “made-up,” by transmitting torque against one of the tubulars while the other tubular is typically held stationary. Torque is transmitted in a single direction in accordance with the direction corresponding with connection make-up. Any torque applied to the joint in the make-up direction will have the effect of continuing to tighten the threaded joint. 
     When running tubulars there is sometimes a requirement to run jointed tubulars that will later be expanded by various types of expansion mechanisms. The most basic type of expander tool employs a simple cone-shaped body which is run into a wellbore at the bottom of the casing which is to be expanded. The expander tool is then forced upward in the wellbore by both pulling on the working string from the surface and applying pressure below the cone. A basic arrangement of a conical expander tool is disclosed in U.S. Pat. No. 5,348,095, issued to Worrall, et al., in 1994 and that patent is incorporated herein in its entirety. Pulling the expanded conical tool has the effect of expanding a portion of a tubular into sealed engagement with a surrounding formation wall, thereby sealing off the annular region therebetween. More recently, rotary expander tools have been developed. Rotary expander tools employ one or more rows of compliant rollers which are urged outwardly from a body of the expander tool in order to engage and to expand the surrounding tubular. The expander tool is rotated downhole so that the actuated rollers can act against the inner surface of the tubular to be expanded in order to expand the tubular body circumferentially. Radial expander tools are described in U.S. Pat. No. 6,457,532 and that patent is incorporated herein by reference in its entirety. 
     Tubulars to be later expanded are typically run downhole where the mechanical and seal integrity of the connections, or joints, are critically important both in the original and expanded state of the tubulars. The current method of making-up expandable tubulars is by the design of modified threaded connections which can be applied and handled in the same way as conventional oil-field tubulars, i.e., stabbed into each other and screwed together by right hand or left hand rotation and finally torqued to establish the seal integrity. This method of connecting tubulars, though a reliable means of connecting non-expanding tubulars, is proving to be problematic when these tubulars are expanded. The reasons for this being mainly due to the changes in geometry of the connection during expansion due to the stresses applied at the threads, or joint area. For instance, conventional tubulars expanded at the joint may disengage allowing the lower tubing to fall into the wellbore. 
     It is well known and understood that during the expansion of solid all tubulars, the material in the tubing wall is plastically deformed in more than just the circumferential sense. In order for a tubular to increase in diameter by plastic deformation, the material to make-up the additional circumferential section of wall in the larger diameter must come from the tubing wall itself either by reduction in wall thickness or by reduction in tubular length or a combination of both. In a plain wall section of the tubular this process will normally take place in a relatively controlled and uniform way. However, at the point of a threaded connection, or joint, the changes in wall section, which are required in order to form an expandable threaded connection, introduce very complex and non-uniform stresses during and after expansion. These during-expansion stresses significantly change the thread form and compromise the connection integrity both in terms of its mechanical strength as well as in terms of its sealing capability. Specifically, elongation along the thread helix may result in a thinning of the thread profile perpendicular to the thread helix. 
     Additionally, due to the changes in geometry of the threads during expansion, thread jumping may also be an issue. Further, the larger elastic deformation caused by the reduced sections of the tubing wall at the roots of the thread will introduce much higher stresses than in other areas of the expanded tubular. This in turn may lead to joint failure due to these stresses approaching or exceeding the ultimate strength of the tubing material or by introduction of short cycle fatigue caused by the cyclic nature of some expansion processes being applied at these high stress levels. 
     Therefore, there exists a need for a tubular connection that can withstand torque and is prevented from becoming unmade during expansion of the tubular. There exists a further need for a connection that has a higher yield strength than that of the tubular body, or pipe wall. There exists still a further need for a connection that is free to move along its profile relative to the tubular wall during expansion of the tubular. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to tubular connections that can resist torque and maintain a connection after expansion within a wellbore. In accordance with the invention, a metal insert or connector, preferably a high tensile wire, is placed within a cavity formed between corresponding machined grooves of a first tubular and a second tubular after make-up. Depending upon wellbore characteristics, the connector may be coated with Teflon, an inert sealant, or other material known to those in the art for sealing purposes. 
     In operation, the connector is inserted through a slot in a wall of one tubular and into the continuous cavity, this cavity being the product of the alignment of matching groove patterns machined into a box portion and a pin portion of the tubulars. In a preferred embodiment, the slot or opening is milled through the wall of the box. The slot is further milled to align with an end of the recessed groove profile of that tubular. The groove is preferably helical in nature; however, multiple individual grooves, with individual insertion points, spaced out axially on the connection can also achieve the same desired effect. Since the groove is not limited to a radiused profile, it can be dovetail in shape, square, or have an infinite number of possible profiles. 
     Once the groove on the box aligns with the groove on the pin, the connector, preferably a wire that has a higher tensile strength than that of the box or pin, is inserted into the slot and along the recessed groove profile, that is through the continuous cavity. Essentially, the connector becomes the carrying mechanism between the box and the pin similar to the threads in a conventional threaded connection. 
     Reducing or eliminating relative rotation of the pipe on either side of the connection can be accomplished by a number of different embodiments. First, cutting variable pitch grooves on both the box and the pin can address these torque issues. In so doing, the two tubulars can not disengage when the box is rotated relative to the pin due to the immediate mismatch in the connector grooves unlike a normal threaded connection. Alternatively, the tubulars can possess castellated, or toothed, ends that essentially lock the tubular ends together. In this manner, the tubular walls possess a corresponding number of locking recesses and keys that resist torque once the connection is made. Further yet, the connection can employ close tolerance fits in conjunction with a variety of different surface finishes between the two mating parts. Therefore, torque has to then overcome the friction that develops between the two pieces. Still further yet, screws that engage both tubulars can be used to couple the two tubulars together. A further embodiment applies a combination of the embodiments described above. 
     In order to mitigate thinning of the inserted connector, partial cuts may be made on the inserted connector along its entire length. This causes the connector to separate into a multitude of shorter sections without compromising the cross section of the connector during expansion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is an elevation view schematically showing tubulars within a borehole and a representative expander tool at a joint between two tubulars. 
         FIG. 2  is an isometric view of an embodiment of a box end of a tubular with a recessed groove on an interior wall of the box end of the tubular and a slot in a wall of the box end of the tubular. 
         FIG. 3  is an isometric view of an embodiment of a pin end of a tubular with a corresponding recessed groove on an exterior wall of the pin end of the tubular. 
         FIG. 4  is a cross-sectional view of the tubulars shown in  FIG. 2  and  FIG. 3  in a mated or stabbed-in position. 
         FIG. 5A  is a view of another embodiment of a box end that has castellations. 
         FIG. 5B  is a view of another embodiment of a pin end that has mating castellations. 
         FIG. 6  is a view of another embodiment of a pin end that has a variable pitch groove. 
         FIG. 7A  is a view of another embodiment of a pin end with a right hand helix recess and a left hand helix recess. 
         FIG. 7B  is a view of another embodiment of a box end for mating with the pin end shown in  FIG. 7A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates an embodiment of the present invention in use within a wellbore  10 . Visible in  FIG. 1  is a representative rig  2 , a ground surface  6 , a formation  4 , a drill string or running string  8 , a first tubular  101 , a second tubular  201 , a representative expander tool  40  comprising a body  42  and an expansion member  45  or roller, a bore  400  running through the tubulars, and a connection  60  or joint, between the first tubular  101  and the second tubular  201 . 
     In operation, the first tubular  101  and the second tubular  201  are mated together at the surface  6  with the only deviation from normal stab-in and threading procedures being that of adding a connector (not shown) into a continuous cavity formed by matching recessed grooves (not shown) of the tubulars  101 ,  201  as described in detail later in the specification. The stab-in procedure can be preformed with tubulars arranged in a pin up and a box down configuration or a configuration with the pin down and the box up. After run-in, the tubulars can be expanded from within by any method known to those skilled in the art. The expansion process can be run in any axial and/or rotational direction within the tubulars  101 ,  201 . As shown, a running tool with an expander element  40  or tool attached thereto is run up the bore  400  of the tubulars. At a desired location, an operator expands the tubulars. When the expander tool  40  reaches the connection  60  between the first tubular  101  and the second tubular  201 , an internal wall of the pin portion of the second tubular  201  expands into the higher tensile strength connector (not shown) and dissipates force into a wall of the box portion of the first tubular  101 . The connection  60  between the tubulars  101 ,  201  is capable of being expanded without losing its mechanical or sealing integrity. The connector insert (not shown) that is located between the recessed grooves of the two tubulars  101 ,  201  does not thin or plastically deform in the same degree as the tubulars  101 ,  201 . 
       FIG. 2  is an isometric view of a box end  100  of a first tubular  101 . As shown, an inside diameter of the box end  100  comprises a recessed groove  110 . As further shown, a wall of the box end  100  includes a slot  130  or opening that a connector (not shown) may be inserted through. The slot  130  allows insertion of the connector along the recessed groove  110 . Consequently, the slot  130  is preferably in alignment with the recessed groove  110 .  FIG. 3  is an isometric view of a pin end  200  of a second tubular  201 . As shown, an outside diameter of the pin end  200  comprises a corresponding recessed groove  210  that matches the profile of the groove  110  of the box end  100  (shown in  FIG. 2 ). The grooves  110 ,  210  shown in  FIG. 2  and  FIG. 3  are an example of a radius groove that is circular in nature; however, the grooves  110 ,  210  can have any number of different profiles such as multiple individual grooves  110  axially separated with individual insertion slots  130  or grooves  110 ,  210  that are dovetail in shape or square. 
       FIG. 4  is a cross-sectional view of the first tubular  101  shown in  FIG. 2  and the second tubular  201  shown in  FIG. 3  in a mated or stabbed-in position. As shown, the pin end  200  can have a tapered outside diameter that mates with a tapered inside diameter of the box end  100  in order to increase a carrying capacity of the connection  60 . In operation, the pin end  200  stabs into the box end  100  of the adjoining first tubular  101  and the corresponding groove  210  aligns with the recessed groove  110  on the box end  100  to form a continuous cavity  301 , or closed pathway, that a connector  300 , or wire, may be placed within. When the pin end  200  stabs into the box end  100 , an end  120  of the box end  100  contacts a shoulder  220  of the pin end  200  to allow for alignment of the grooves  110  on the box end  100  with the corresponding grooves  210  on the pin end  200 , such that the connector  300  can be inserted. To further aid in aligning the grooves  110 ,  210 , identifying marks or locating tabs (not shown) such as alignment arrows may be placed on an exterior of the tubulars  101 ,  201  so that when a mark of the second tubular  201  is in linear alignment with a mark on the first tubular  101  an operator would know that the grooves  110 ,  210  of the two tubulars  101 ,  201  are in alignment and the continuous cavity  301  exists. 
     An inside surface  112  (see  FIG. 2 ) of the box end  100  and an outside surface  212  (see  FIG. 3 ) of the pin end  200  can comprise a finish that when mated as shown in  FIG. 4  provides a frictional resistance between the box end  100  and the pin end  200  that prevents relative rotation between the first tubular  101  and the second tubular  201 . Additionally, a torque screw  114  (see  FIG. 2 ) in the box end  100  can engage the pin end  200  in order to prevent relative rotation between the first tubular  101  and the second tubular  201 . The surface finishes and torque screws are examples of torque locking devices. 
     The connector  300  is preferably a wire with a higher tensile strength than that of the box end  100  and the pin end  200 . The shape of the connector  300  preferably matches the shape of the cavity  301 . Therefore, a cross section of the connector  300  can be round, square, dovetail or any shape matching the cavity  301 . Additionally, partial cuts into the radius of the connector  300  and along the entire length of the connector  300  can be made in order to mitigate thinning of the connector  300  since the connector  300  separates at these partial cuts into a multitude of shorter sections without compromising the cross section of the connector  300  during expansion of the tubulars  101 ,  201 . 
     Sealing arrangements (not shown) for use with the connection  60  are also envisioned. These sealing arrangements can include the use of a coating on the connector  300  such as a sealant, Teflon, or other material. The use of gaskets or o-rings comprised of an elastomer, some other non-metallic material, or a metallic material positioned between the pin end  100  and the box end  200  can provide a seal. Additionally, a metal to metal seal between an end  240  of the pin end  200  and an inside portion  140  of the box end  100  can provide a seal. 
     After the connector  300  is inserted into the cavity  301 , it is possible that a portion of the connector  300  will extend out of the slot  130  (shown in  FIG. 2 ). For run-in, this portion of the connector  300  can be cut or machined in order to achieve a flush tubular exterior. A set screw (not shown) may be used to seal the slot  130  (shown in  FIG. 2 ) once the connector  300  is inserted. In operation, this is achieved by having the slot  130  pre-tapped in order to receive the set screw. Additionally, the box end  100  can include trapping profiles (not shown) on an outside diameter of the box end  100  adjacent the slot  130  in order to clip the end of the connector  300  out of the way. 
       FIG. 5A  and  FIG. 5B  are views of another embodiment of the present invention.  FIG. 5A  depicts a box end  100  of a first tubular  101  similar to the box end shown in  FIG. 2  with the addition of castellations  540  on an end  120  of the box end  100 .  FIG. 5B  depicts a pin end  200  of a second tubular  201  similar to the pin end shown in  FIG. 3  with the addition of mating castellations  640  on a shoulder  220 . Therefore, incorporating that from above provides a connection between the tubulars  101 ,  201  that resists rotation between the tubulars  101 ,  201  due to the castellations  540 ,  640 . The castellations  540 ,  640  can be square shaped, toothed, or any shape capable of preventing rotational movement between the tubulars  101 ,  201  once the pin end  200  is stabbed into the box end  100  and the castellations  540  mate with the mating castellations  640 . Therefore castellations  540 ,  640  are examples of torque locking devices. 
       FIG. 6  is an isometric view of another embodiment of the present invention. Visible in  FIG. 6  is a pin end  200  of a second tubular  201  with a variable pitch groove  720 . Similar to the connection described in  FIG. 4 , the pin end  200  mates with a box end of a first tubular (not shown) that has a corresponding variable pitch groove within the box end in order to form a continuous cavity with a variable pitch. Therefore, a connector positioned within the continuous cavity with the variable pitch resists rotational movement between the tubulars. Unlike conventional threaded tubulars that cannot be fitted with variable pitch threads, the use of the connector between the two tubulars allows the connection formed using the embodiment shown in  FIG. 6  the ability to resist torque. Therefore, the variable pitch groove  720  itself provides another example of a torque locking device. 
     Additionally,  FIG. 7A  and  FIG. 7B  illustrate another embodiment of the present invention that uses two or more separated recesses with alternating helixes to connect a first tubular  101  with a second tubular  201 . As shown in  FIG. 7A , a pin end  200  of the second tubular  201  has a first groove  700  that forms a right hand helix and a second groove  701  that forms a left hand helix. In addition to the first groove  700  and second groove  701 , there can be additional independent alternating helix grooves.  FIG. 7B  illustrates a box end  100  of the first tubular  101  with multiple slots  130  in order to allow insertion of connectors (not shown) into each of the grooves  700 ,  701 . Using separate grooves  700 ,  701  with alternating helixes prevents relative rotation between the first tubular  101  and the second tubular  201 . Therefore, the grooves  700 ,  701  with alternating helixes provide another example of a torque locking device. 
     The connection arrangements shown above are but an example of a connector of the present invention. Other arrangements and embodiments may be utilized within the spirit and scope of the present invention. As such, while the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.