Abstract:
A wellbore expandable connection, which includes a tubular pin member having an outwardly facing tapered threaded section and a tubular box member having an inwardly facing tapered threaded section. The threaded sections form a connection of a predetermined integrity when the tubular pin member is mated with the tubular box member. The integrity of the connection is substantially maintained during radial expansion of the connection.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the present invention generally relate to wellbore completion, and more particularly, to tubular connections. 
   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 typically run into a wellbore at the bottom of the casing that 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., 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 that 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, issued to Simpson et al., 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 uses threaded connections that 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 wall 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, the changes in wall section, such as that of the box or pin, introduce very complex and non-uniform stresses during and after expansion. These during-expansion stresses may 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. 
   Therefore, a need exists for an improved tubular connection that is capable of being expanded without losing its mechanical or sealing integrity. 
   SUMMARY OF THE INVENTION 
   Embodiments of the present invention are generally directed to a wellbore expandable connection, which includes a tubular pin member having an outwardly facing tapered threaded section and a tubular box member having an inwardly facing tapered threaded section. The threaded sections form a connection of a predetermined integrity when the tubular pin member is mated with the tubular box member. The integrity of the connection is substantially maintained during radial expansion of the connection. 
   In one embodiment, the wall thickness of the pin member along a substantial portion of the outwardly facing threaded section is substantially constant. 
   In another embodiment, the wall thickness of the box member along a substantial portion of the inwardly facing threaded section is substantially constant. 

   
     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  illustrates a threaded connection in greater details in accordance with one embodiment of the invention. 
       FIG. 3  illustrates a threaded connection in accordance with another embodiment of the invention. 
       FIG. 4  illustrates a threaded connection in accordance with yet another embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     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  according to normal stab-in and threading procedures. The stab-in procedures 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 tool  40  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 an internal 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. 
     FIG. 2  illustrates a threaded connection  200  in greater details in accordance with one embodiment of the invention. The connection  200  includes a pin member  210  formed at a threaded section of the first tubular  101  and a box member  220  formed at a threaded section of the second tubular  201 . In one embodiment, the threaded sections of the pin member  210  and the box member  220  are tapered. The pin member  210  includes helical threads  212  extending along its length. The box member  220  includes helical threads  224  that are shaped and sized to mate with the helical threads  212  during the make-up of the threaded connection  200 . The threaded sections of the pin member  210  and the box member  220  form the connection  200  of a predetermined integrity when the pin member  210  is mated with the box member  220 . Additionally, depending upon wellbore characteristics, the threads may be coated with Teflon, an inert sealant, or other material known to those in the art for sealing purposes. The threads may be dovetail threads, as described in U.S. Pat. No. 3,989,284, issued to Blose, and that patent is incorporated herein by reference. The threads may be machined on plain end tubulars, tubulars with both ends upset, tubulars with one plain end and one end upset, or other connection types as typically used in the oil and gas industry. One of ordinary skill in the art can appreciate that embodiments of the present invention are not limited to only certain kinds of tubular ends or thread types. 
   In one embodiment, the box member  220  is constructed such that the wall thickness  250  of the box member  220  along a substantial portion of the threaded section is substantially constant, thereby allowing the threaded section of the box member  220  to bend in parallel with the threaded section of the pin member  210  during expansion. As such, the outer surface  230  of the box member  220  along the threaded section may be substantially in parallel with the inner surface  235  of the box member  220  along the threaded section and the outside diameter of the box member  220  along the threaded section may be less than the outside diameter of the box member  220  along the non-threaded section. In this manner, the connection  200  is capable of being radially expanded without substantially losing its mechanical or sealing integrity. 
     FIG. 3  illustrates a threaded connection  300  in accordance with another embodiment of the invention. The connection  300  includes a pin member  310  formed at a threaded section of the first tubular  101  and a box member  320  formed at a threaded section of the second tubular  201 . In one embodiment, the threaded sections of the pin member  310  and the box member  320  are tapered. The pin member  310  includes helical threads  312  extending along its length. The box member  320  includes helical threads  324  that are shaped and sized to mate with the helical threads  312  during the make-up of the threaded connection  300 . The threaded sections of the pin member  310  and the box member  320  form the connection  300  of a predetermined integrity when the pin member  310  is mated with the box member  320 . Additionally, depending upon wellbore characteristics, the threads may be coated with Teflon, an inert sealant, or other material known to those in the art for sealing purposes. The threads may be dovetail threads, as described in U.S. Pat. No. 3,989,284, issued to Blose, and that patent is incorporated herein by reference. The threads may be machined on plain end tubulars, tubulars with both ends upset, tubulars with one plain end and one end upset, or other connection types as typically used in the oil and gas industry. One of ordinary skill in the art can appreciate that embodiments of the present invention are not limited to only certain kinds of tubular ends or thread types. 
   The pin member  310  is constructed such that the wall thickness  350  of the pin member  310  along a substantial portion of the threaded section is substantially constant, thereby allowing the threaded section of the pin member  310  to bend in parallel with the threaded section of the box member  320  during expansion. As such, the outer surface  335  of the pin member  310  along the threaded section may be substantially in parallel with the inner surface  330  of the pin member  310  along the threaded section and the inside diameter of the pin member  310  along the threaded section may be less than the inside diameter of the pin member  310  along the non-threaded section. In this manner, the connection  300  is capable of being radially expanded without substantially losing its mechanical or sealing integrity. 
     FIG. 4  illustrates a threaded connection  400  in accordance with yet another embodiment of the invention. The connection  400  includes a pin member  410  formed at a threaded section of the first tubular  101  and a box member  420  formed at a threaded section of the second tubular  201 . In one embodiment, the threaded sections of the pin member  410  and the box member  420  are tapered. The pin member  410  includes helical threads  412  extending along its length. The box member  420  includes helical threads  424  that are shaped and sized to mate with the helical threads  412  during the make-up of the threaded connection  400 . The threaded sections of the pin member  410  and the box member  420  form the connection  400  of a predetermined integrity when the pin member  410  is mated with the box member  420 . Additionally, depending upon wellbore characteristics, the threads may be coated with Teflon, an inert sealant, or other material known to those in the art for sealing purposes. The threads may be dovetail threads, as described in U.S. Pat. No.  3 , 989 , 284 , issued to Blose, and that patent is incorporated herein by reference. The threads may be machined on plain end tubulars, tubulars with both ends upset, tubulars with one plain end and one end upset, or other connection types as typically used in the oil and gas industry. One of ordinary skill in the art can appreciate that embodiments of the present invention are not limited to only certain kinds of tubular ends or thread types. 
   The pin member  410  is constructed such that the wall thickness  450  of the pin member  410  along a substantial portion of the threaded section is substantially constant. As such, the outer surface  435  of the pin member  410  along the threaded section may be substantially in parallel with the inner surface  430  of the pin member  410  along the threaded section and the inside diameter of the pin member  410  along the threaded section may be less than the inside diameter of the pin member  410  along the non-threaded section. 
   The box member  420  is constructed such that the wall thickness  451  of the box member  420  along a substantial portion of the threaded section is substantially constant. As such, the outer surface  431  of the box member  420  along the threaded section may be substantially in parallel with the inner surface  436  of the box member  420  along the threaded section and the outside diameter of the box member  420  along the threaded section may be less than the outside diameter of the box member  420  along the non-threaded section. In this manner, the connection  400  is capable of being expanded without substantially losing its mechanical or sealing integrity. Although embodiments of the invention are described with reference to a box member, other types of tubular resembling a box member, such as a coupling, are also contemplated by the embodiments of the invention. 
   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.