Abstract:
An apparatus and method of creating a seal between two coaxial tubulars so as to create a hanger and a packer. A first tubular is disposed coaxially within a portion of a second, larger tubular. A portion of the first tubular is expanded into frictional contact with the second tubular, thereby creating a liner and a hanger. In one embodiment, a pattern of grooves and profile cuts are formed in the surface of a portion of the first tubular body. The grooves in one aspect define a continuous pattern about the circumference of the tubular body which intersect to form a plurality of substantially identical shapes, such as diamonds. The grooves and profile cuts serve to improve the tensile strength of the tubular body. At the same time, the grooves and profile cuts allow for expansion of the tubular body by use of less radial force. The grooves and profile cuts further provide a gripping means, providing additional frictional support for hanging the expanded tubular onto the inner surface of a surrounding second tubular.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 09/949,986 filed Sep. 10, 2001 and incorporated by reference herein in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1 Field of the Invention  
           [0003]    The present invention relates to wellbore completion. More particularly, the invention relates to an apparatus and method for creating an attachment and a seal between two tubulars in a wellbore.  
           [0004]    2 Description of the Related Art  
           [0005]    In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed, and the wellbore is lined with a string of steel pipe called casing. The casing provides support to the wellbore and facilitates the isolation of certain areas of the wellbore adjacent hydrocarbon bearing formations. The casing typically extends down the wellbore from the surface of the well to a designated depth. An annular area is thus defined between the outside of the casing and the earth formation. This annular area is filled with cement to permanently set the casing in the wellbore and to facilitate the isolation of production zones and fluids at different depths within the wellbore.  
           [0006]    It is common to employ more than one string of casing in a wellbore. In this respect, a first string of casing is set in the wellbore when the well is drilled to a first designated depth. The well is then drilled to a second designated depth, and a second string of casing, or liner, is run into the well to a depth whereby the upper portion of the second liner is overlapping the lower portion of the first string of casing. The second liner string is then fixed or hung in the wellbore, usually by some mechanical slip mechanism well-known in the art, and cemented. This process is typically repeated with additional casing strings until the well has been drilled to total depth.  
           [0007]    After the initial string of casing is set, the wellbore is drilled to a new depth. An additional string of casing, or liner, is then run into the well to a depth whereby the upper portion of the liner, is overlapping the lower portion of the surface casing. The liner string is then fixed or hung in the wellbore, usually by some mechanical slip mechanism well known in the art, commonly referred to as a hanger.  
           [0008]    Downhole tools with sealing elements are placed within the wellbore to isolate areas of the wellbore fluid or to manage production fluid flow from the well. These tools, such as plugs or packers, for example, are usually constructed of cast iron, aluminum or other alloyed metals and include slip and sealing means. The slip means fixes the tool in the wellbore and typically includes slip members and cores to wedgingly attach the tool to the casing well. In addition to slip means, conventional packers include a synthetic sealing element located between upper and lower metallic retaining rings.  
           [0009]    The sealing element is set when the rings move towards each other and compress the element there between, causing it to expand outwards into an annular area to be sealed and against an adjacent tubular or wellbore. Packers are typically used to seal an annular area formed between two coaxially disposed tubulars within a wellbore. For example, packers may seal an annulus formed between production tubing disposed within wellbore casing. Alternatively, packers may seal an annulus between the outside of the tubular and an unlined borehole. Routine uses of packers include the protection of casing from pressure, both well and stimulation pressures, as well as the protection of the wellbore casing from corrosive fluids. Other common uses include the isolation of formations or leaks within a wellbore casing or multiple production zones, thereby preventing the migration of fluid between zones. Packers may also be used to hold fluids or treating fluids within the casing annulus in the case of formation treatment, for example.  
           [0010]    One problem associated with conventional sealing and slip systems of conventional downhole tools relates to the relative movement of the parts necessary in order to set the tools in a wellbore. Because the slip and sealing means require parts of the tool to be moved in opposing directions, a run-in tool or other mechanical device must necessarily run into the wellbore with the tool to create the movement. Additionally, the slip means takes up valuable annular space in the wellbore. Also, the body of a packer necessarily requires wellbore space and reduces the bore diameter available for production tubing, etc.  
           [0011]    A recent trend in well completion has been the advent of expandable tubular technology. It has been discovered that both slotted and solid tubulars can be expanded in situ so as to enlarge the inner diameter. This, in turn, enlarges the path through which both fluid and downhole tools may travel. Also, expansion technology enables a smaller tubular to be run into a larger tubular, and then expanded so that a portion of the smaller tubular is in contact with the larger tubular therearound. Tubulars are expanded by the use of a cone-shaped mandrel or by an expander tool with expandable, fluid actuated members disposed on a body and run into the wellbore on a tubular string. During expansion of a tubular, the tubular walls are expanded past their elastic limit. Examples of expandable tubulars include slotted screen, joints, packers, and liners. The use of expandable tubulars as hangers and packers allows for the use of larger diameter production tubing, because the conventional slip mechanism and sealing mechanism are eliminated.  
           [0012]    While expanding tubulars in a wellbore offers obvious advantages, there are problems associated with using the technology to create a hanger or packer through the expansion of one tubular into another. By plastically deforming the tubular, the cross-sectional thickness of the tubular is necessarily reduced. Simply increasing the initial cross-sectional thickness of the tubular to compensate for the reduced tensile strength after expansion results in an increase in the amount of force needed to expand the tubular.  
           [0013]    More importantly, when compared to a conventional hanger, an expanded tubular with no gripping structure on the outer surface has a reduced capacity to support the weight of a liner. This is due to a reduced coefficient of friction of the outer surface of an expandable tubular in comparison to the slip mechanism having teeth or other gripping surfaces formed thereon. In another problem, the expansion of the tubular in the wellbore results in an ineffective seal between the expanded tubular and the surrounding wellbore.  
           [0014]    A need therefore exists for an expandable tubular connection with increased strength. There is a further need for an expandable tubular connection providing an improved gripping surface between an expanded tubular and an inner wall of a surrounding tubular. Yet a further need exists for an expandable tubular configured to allow metal flow upon expansion to insure contact and sealing capabilities between an expanded tubular and an inner wall of a surrounding tubular. There is yet a further need for an expandable tubular with an increased capacity to support the weight of a liner.  
         SUMMARY OF THE INVENTION  
         [0015]    The present invention generally relates to an apparatus and method for engaging a first tubular and a second tubular in a wellbore. The present invention provides a tubular body formed on a portion of a first tubular. The tubular body is expanded so that the outer surface of the tubular body is in frictional contact with the inner surface of a surrounding second tubular. In one embodiment, the tubular body is modified by machining grooves and profile cuts into the surface, thereby reducing the amount of radial force required to expand the tubular body on the first tubular into the surrounding tubular.  
           [0016]    The tubular body optionally includes hardened inserts, such as carbide buttons, for gripping the surrounding tubular upon contact. The gripping mechanism increases the capacity of the expanded tubular to support its weight and to serve as a hanger. In another aspect, the outer surface of the expandable tubular body optionally includes a pliable material such as an elastomer within grooves and profile cuts formed on the outer surface of the tubular for increasing the sealing capability of the expandable tubular. As the tubular is expanded, metal flow causes the profile cuts to close up, thereby causing the pliable material to extrude outward. This extrusion of the pliable material insures contact with the casing and improves the sealing characteristics of the interface between the expanded tubular and the casing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    So that the manner in which the above recited features and advantages of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.  
         [0018]    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.  
         [0019]    [0019]FIG. 1 is a perspective view of a tubular having profile cuts that intersect corners of the grooves formed in the outer surface, and having inserts of a hardened material also disposed around the outer surface.  
         [0020]    [0020]FIG. 2 is a section view of the tubular of FIG. 1.  
         [0021]    [0021]FIG. 3 is an exploded view of an exemplary expander tool.  
         [0022]    [0022]FIG. 4 is a partial section view of a tubular of the present invention within a wellbore, and showing an expander tool attached to a working string also disposed within the tubular.  
         [0023]    [0023]FIG. 5 is a partial section view of the tubular of FIG. 4 partially expanded by the expander tool.  
         [0024]    [0024]FIG. 6 is a partial section view of an expanded tubular in the wellbore with the expander tool and working string removed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    [0025]FIG. 1 is a perspective view of the apparatus of the present invention. The apparatus  200  defines a tubular body formed on a portion of a larger tubular. The tubular body  200  shown in FIG. 1 includes a series of relief grooves  210  and profile cuts  205  machined into the outer surface. However, it is within the scope of the present invention to machine some or all of the grooves  210  into the inner surface of the expandable tubular  200 . The relief grooves  210  and profile cuts  205  serve to reduce the thickness of the tubular  200 , thereby reducing the amount of material that must be plastically deformed in order to expand the tubular  200 . This reduction in material also results in a reduction in the amount of force needed to expand the tubular  200 .  
         [0026]    As shown in FIG. 1, the grooves  210  are machined in a defined pattern. Employment of a pattern of grooves  210  serves to increase the tensile properties of the tubular  200  beyond those of a tubular with straight grooves simply cut around the circumference of the tubular. This improvement in tensile properties is due to the fact that the variation in cross-sectional thickness will help to prevent the propagation of any cracks formed in the tubular. The pattern of grooves depicted in FIG. 1 is a continuous pattern of grooves  210  about the circumference of the body  200 , with the grooves  210  intersecting to form a plurality of substantially identical shapes. In the preferred embodiment, the shapes are diamonds. However, the scope of this invention is amenable to other shapes, including but not limited to polygonal shapes, and interlocking circles, loops or ovals (not shown).  
         [0027]    In one embodiment, the profile cuts  205  are formed on the surface of the shapes created by the grooves  210 . The profile cuts  205  are formed at a predetermined depth less than the grooves  210  so that the profile cuts  205  will not substantially affect the compressive or tension capabilities of the tubular  200  upon expansion. The profile cuts  205  may be horizontal cuts, vertical cuts or combinations thereof to divide each shape into two or more portions. Preferably, the profile cuts  205  intersect the corners of the grooves  210  as depicted on FIG. 1.  
         [0028]    [0028]FIG. 1 also depicts inserts  220  interdisposed within the pattern of grooves  210  and profile cuts  205 . The inserts  220  provide a gripping means between the outer surface of the tubular  200  and the inner surface of a larger diameter tubular (not shown) within which the tubular  200  is coaxially disposed. The inserts  220  are made of a suitably hardened material, and are attached to the outer surface of the tubular  200  through a suitable means such as soldering, epoxying or other adhesive method, or via threaded connection. In the preferred embodiment, carbide inserts  220  are press-fitted into preformed apertures in the outer surface of tubular body  200 . After expansion, the inserts  220  are engaged with the inner surface of a larger diameter tubular (not shown), thereby increasing the ability of the expanded tubular  200  to support the weight of the tubular below the expanded portion.  
         [0029]    In the embodiment shown in FIG. 1, carbide inserts  220  are utilized as the gripping means. However, other materials may be used for fabrication of the inserts  220  so long as the inserts  220  are sufficiently hard to be able to grip the inner surface of an outer tubular during expansion of the tubular body  200 . Examples of fabrication materials for the inserts  220  include ceramic materials (such as carbide) and hardened metal alloy materials. The carbide inserts  220  define raised members fabricated into the tubular body  200 . However, other embodiments of gripping means may alternatively be employed. Such means include but are not limited to buttons having teeth (not shown), or other raised or serrated members on the outer surface of the expandable tubular  200 . Alternatively, the gripping means may define a plurality of hardened tooth patterns added to the outer surface of the tubular body  200  between the grooves  210  themselves.  
         [0030]    The embodiment of FIG. 1 also depicts a pliable material  230  disposed within the grooves  210  and profile cuts  205 . The pliable material  230  increases the ability of the tubular  200  to seal against an inner surface of a larger diameter tubular upon expansion. In the preferred embodiment, the pliable member  230  is fabricated from an elastomeric material. However, other materials are suitable which enhance the fluid seal sought to be obtained between the expanded portion of tubular  200  and an outer tubular, such as surface casing (not shown). The pliable material  230  is disposed within the grooves  210  and profile cuts  205  by a thermal process, or some other well known means. A thin layer of the pliable material  230  may also encapsulate the inserts  220  and facilitate the attachment of the inserts  220  to the tubular  200 .  
         [0031]    [0031]FIG. 2 is a section view of a portion of the tubular  200  of FIG. 1. In this view, the inserts  220  are shown attached to the tubular  200  in the areas between the grooves  210  and at an intersection of the profile cuts  205 . In this respect, the inserts  220  are interdispersed within the pattern of grooves  210  and profile cuts  205 . FIG. 2 also clearly shows the reduction in cross-sectional thickness of the tubular  200  created by the grooves  210  and profile cuts  205  before expansion. FIG. 2 further shows the profile cuts  205  formed at a depth less than the grooves  210 .  
         [0032]    The inserts  220  in FIG. 2 have a somewhat conical shape projecting from the outer surface of the tubular  200  to assist in engagement of the inserts  200  into an outer tubular (shown in FIG. 4). For clarity, the inserts are exaggerated in the distance they extend from the surface of the tubular. In one embodiment, the inserts extend only about 0.03 inches outward prior to expansion. In another embodiment, the raised members  220  are initially recessed, either partially or completely, with respect to the tubular  200 , and then extend at least partially outward into contact with the casing after expansion. Such an embodiment is feasible for the reason that the wall thickness of the tubular  200  becomes thinned during the expansion process, thereby exposing an otherwise recessed raised member.  
         [0033]    The tubular body  200  of the present invention is expanded by an expander tool  100  acting outwardly against the inside surface of the tubular  200 . FIG. 3 is an exploded view of an exemplary expander tool  100  for expanding the tubular  200 . The expander tool  100  has a body  102 , which is hollow and generally tubular with connectors  104  and  106  for connection to other components (not shown) of a downhole assembly. The connectors  104  and  106  are of a reduced diameter compared to the outside diameter of the longitudinally central body part of the tool  100 . The central body part  102  of the expander tool  100  shown in FIG. 3 has three recesses  114 , each holding a respective roller  116 . Each of the recesses  114  has parallel sides and extends radially from a radially perforated tubular core (not shown) of the tool  100 . Each of the mutually identical rollers  116  is somewhat cylindrical and barreled. Each of the rollers  116  is mounted by means of an axle  118  at each end of the respective roller  116  and the axles are mounted in slidable pistons  120 . The rollers  116  are arranged for rotation about a respective rotational axis that is parallel to the longitudinal axis of the tool  100  and radially offset therefrom at 120-degree mutual circumferential separations around the central body  102 . The axles  118  are formed as integral end members of the rollers  116 , with the pistons  120  being radially slidable, one piston  120  being slidably sealed within each radially extended recess  114 . The inner end of each piston  120  is exposed to the pressure of fluid within the hollow core of the tool  100  by way of the radial perforations in the tubular core. In this manner, pressurized fluid provided from the surface of the well, via a working string  310 , can actuate the pistons  120  and cause them to extend outward whereby the rollers  116  contact the inner wall of a tubular  200  to be expanded.  
         [0034]    [0034]FIG. 4 is a partial section view of a tubular  200  of the present invention in a wellbore  300 . The tubular  200  is disposed coaxially within the casing  400 . An expander tool  100  attached to a working string  310  is visible within the tubular  200 . Preferably, the tubular  200  is run into the wellbore  300  with the expander tool  100  disposed therein. The working string  310  extends below the expander tool  100  to facilitate cementing of the tubular  200  in the wellbore  300  prior to expansion of the tubular  200  into the casing  400 . A remote connection (not shown) between the working, or run-in, string  310  and the tubular  200  temporarily connects the tubular  200  to the run-in string  310  and supports the weight of the tubular  200 . In one embodiment of the present invention, the temporary connection is a collett (not shown), and the tubular  200  is a string of casing.  
         [0035]    [0035]FIG. 4 depicts the expander tool  100  with the rollers  116  retracted, so that the expander tool  100  may be easily moved within the tubular  200  and placed in the desired location for expansion of the tubular  200 . Hydraulic fluid (not shown) is pumped from the surface to the expander tool  100  through the working string  310 . When the expander tool  100  has been located at the desired depth, hydraulic pressure is used to actuate the pistons (not shown) and to extend the rollers  116  so that they may contact the inner surface of the tubular  200 , thereby expanding the tubular  200 .  
         [0036]    [0036]FIG. 4 also shows the carbide inserts  220  attached to the outer surface of the tubular  200 . Because the tubular  200  has not yet been expanded, the carbide inserts  220  are not in contact with the casing  400  so as to form a grip between the tubular  200  and casing  400 . FIG. 4 also shows the pliable material  230  disposed within the grooves  210  and the profile cuts  205 .  
         [0037]    [0037]FIG. 5 is a partial section view of the tubular  200  partially expanded by the expander tool  100 . At a predetermined pressure, the pistons (not shown) in the expander tool  100  are actuated and the rollers  116  are extended until they contact the inside surface of the tubular  200 . The rollers  116  of the expander tool  100  are further extended until the rollers  116  plastically deform the tubular  200  into a state of permanent expansion. The working string  310  and the expander tool  100  are rotated during the expansion process, and the tubular  200  is expanded until the tubular&#39;s outer surface contacts the inner surface of the casing  400 . As the tubular  200  contacts the casing  400 , the inserts  220  begin to engage the inner surface of the casing  400 .  
         [0038]    The grooves  210  are also expanded during this expansion process, thereby causing some of the metal around the grooves  210  to flow away from the grooves  210 . The metal flow is redistributed in the shallower profile cuts  205 , thereby closing the profile cuts  205 . As the profile cuts  205  close, the pliable material  230  in the profile cuts  205  extrudes outward into contact with the casing  400 . Further, the pliable material  230  in the grooves  210  fills a space remaining between the grooves  210  and the casing  400 . After the pliable material  230  contacts the casing  400 , the interface between the expanded tubular  200  and the casing  400  is sealed. The working string  310  and expander tool  100  are then translated within the tubular  200  until the desired length of the tubular  200  has been expanded.  
         [0039]    [0039]FIG. 6 is a partial section view of an expanded tubular  200  in a wellbore  300 , with the expander tool  100  and working string  310  removed. FIG. 6 depicts the completed expansion process, after which the expanded portion of the tubular  200  defines both a packer and a hanger. As a packer, the expanded portion of the tubular  200  seals the annular area between the casing  400  and the tubular  200 . As a hanger, the expanded portion of the tubular  200  supports the weight of the tubular  200 .  
         [0040]    [0040]FIG. 6 shows the engagement between the inserts  220  and the inner surface of the casing  400 . The engagement enables the expanded portion of the tubular  200  to support an increased weight in comparison to an expanded tubular without inserts. The inserts  220  axially and rotationally fix the outer surface of the expanded tubular  200  to the inner surface of the casing  400 . Further, the profile cuts  205  are closed and the pliable material  230  that was in the profile cuts  205  and the grooves  210  is disposed in the interface between the expanded tubular  200  and the casing  400 .  
         [0041]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be directed without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.