Abstract:
The present invention generally relates to an apparatus and method for engaging a first tubular and a second tubular in a wellbore. In one aspect, an apparatus for forming an expanded connection in a wellbore is provided. The apparatus includes a first tubular being radially expandable outward into contact with an inner wall of a second tubular upon the application of an outwardly directed force supplied to an inner surface of the first tubular. The apparatus further includes a plurality of formations formed on an outer surface of the first tubular, the formations constructed and arranged to provide a frictional relationship between the first tubular and the second tubular while leaving a fluid path when the first tubular is expanded to engage the inner wall of the second tubular. In another aspect, an apparatus for engaging a first tubular and a second tubular in a wellbore is provided. In yet another aspect, a method of completing a wellbore is provided.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    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.  
           [0003]    2. Description of the Related Art  
           [0004]    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.  
           [0005]    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.  
           [0006]    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 expansion 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. The use of expandable tubulars as liner hangers and packers allows for the use of larger diameter production tubing, because the conventional slip mechanism and sealing mechanism are eliminated.  
           [0007]    If the liner hanger is expanded by a cone-shaped mandrel, then a forgiving material is typically employed between the outer diameter of the liner hanger and the inner diameter of the larger tubular to accommodate any variances in the inner diameter of the larger tubular. It is this forgiving material that provides the mechanism for hanging the weight of the liner below the liner hanger. Typically, the forgiving material is made from a nitrile rubber compound or a similar material.  
           [0008]    It is usually desirable to expand the liner hanger to support the weight of a liner and then release the running tool from the liner prior to cementing the liner in place. Typically, the use of the cone-shaped mandrel requires that circulation ports be cut in the wall of the liner, directly below the liner hanger section to provide a fluid path for exiting wellbore fluid and cement during the cementing process. Then, following the cementing process, these ports must be isolated by expanding another elastomer clad section below the ports.  
           [0009]    While expanding liner hangers by the cone-shaped mandrel in a wellbore offers obvious advantages, however, there are problems associated with using the technology. For example, by using a forgiving material, such as a nitrile rubber compound, the liner hanging mechanism may only be effectively utilized in a wellbore that has a temperature of less 250° F. If the liner hanger is used in a higher temperature wellbore, then the rubber&#39;s ability to carry a load drops off dramatically due to the mechanical properties of the material. More importantly, the circulating ports that are cut into the wall of the liner below the liner hanger diminish the carrying capacity of the hanger due to a reduction of material through this section therefore limiting the length of the liner.  
           [0010]    A need therefore exists for a solid expandable hanger that provides for a cement bypass without compromising the carrying capacity of the hanger. There is a further need for a solid expandable hanger that is capable of enduring a high temperature installation. Furthermore, there is a need for an improved expandable liner hanger with a means for circulating fluids therearound.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention generally relates to an apparatus and method for engaging a first tubular and a second tubular in a wellbore. In one aspect, an apparatus for forming an expanded connection in a wellbore is provided. The apparatus includes a first tubular being radially expandable outward into contact with an inner wall of a second tubular upon the application of an outwardly directed force supplied to an inner surface of the first tubular. The apparatus further includes a plurality of formations formed on an outer surface of the first tubular, the formations constructed and arranged to provide a frictional relationship between the first tubular and the second tubular while leaving a fluid path when the first tubular is expanded to engage the inner wall of the second tubular.  
           [0012]    In another aspect, an apparatus for engaging a first tubular and a second tubular in a wellbore is provided. The apparatus includes a tubular body formed on the first tubular, having an inner surface and an outer surface, the tubular body being expandable radially outward into contact with an inner wall of the second tubular by the application of an outwardly directed force supplied to the inner surface of the tubular body. The apparatus further includes a plurality of formations formed around the circumference of the tubular body, the plurality of formations are constructed and arranged to provide a frictional relationship between the tubular body and the second tubular while leaving a fluid path through the expanded connection and a gripping means formed on the plurality of formations for further increasing friction between the tubular body and the second tubular upon expansion of the tubular body.  
           [0013]    In yet another aspect, a method of completing a wellbore is provided. The method includes placing a first tubular coaxially within a portion of a second tubular, the first tubular including a plurality of formations on an outer surface thereof to provide a frictional relationship between the first tubular and the second tubular while leaving a fluid path through the expanded connection and positioning an expander tool within the first tubular at a depth proximate the plurality of formations on the first tubular. The method further includes urging the expander tool axially through the first tubular to expand the first tubular into frictional contact with the second tubular and forming a fluid path through an overlapped portion between the first and second tubulars. The method also includes circulating cement through the wellbore and subsequently through the fluid path to secure the first tubular in the wellbore and expanding at least one tubular seal to close off the fluid path and create a fluid seal between the first and second tubulars. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    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.  
         [0015]    [0015]FIG. 1 is a cross-sectional view illustrating a solid expandable hanger of the present invention in a run-in position.  
         [0016]    [0016]FIG. 2 is a cross-sectional view illustrating an expander tool partially expanding the solid expandable hanger.  
         [0017]    [0017]FIG. 3 is a cross-sectional view taken along line  3 - 3  of FIG. 1 illustrating the expander tool in the solid expandable hanger prior to expansion.  
         [0018]    [0018]FIG. 4 is a cross-sectional view taken along line  4 - 4  of FIG. 2 illustrating the expander tool during the expansion of the solid expandable hanger.  
         [0019]    [0019]FIG. 5 is a cross-sectional view illustrating the release of the running tool prior to a cementing operation.  
         [0020]    [0020]FIG. 6 is a cross-sectional view illustrating the cementation of the liner assembly within the wellbore.  
         [0021]    [0021]FIG. 7 is a cross-sectional view illustrating the expansion of the liner seal after the cementing operation.  
         [0022]    [0022]FIG. 8 is a cross-sectional view illustrating the fully expanded solid expandable hanger after the running tool has been removed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    The present invention relates to a method and an apparatus for forming a solid expandable hanger connection with a surrounding casing. Generally, a liner assembly including a liner hanger is disposed in a wellbore proximate the lower end of the surrounding casing. Next, an expander tool is urged axially through the liner hanger to radially expand the hanger into frictional contact with the surrounding casing and to form a plurality of cement bypass ports. Thereafter, cement is circulated through the wellbore and eventually through the plurality of cement bypass ports to cement the liner assembly within the wellbore. Subsequently, a liner seal is radially expanded to seal off the plurality cement bypass ports.  
         [0024]    [0024]FIG. 1 is a cross-sectional view illustrating a solid expandable hanger  200  of the present invention in a run-in position. At the stage of completion shown in FIG. 1, a wellbore  100  has been lined with a string of casing  110 . Thereafter, a subsequent liner assembly  150  is positioned proximate the lower end of the casing  110 . Typically, the liner assembly  150  is lowered into the wellbore  100  by a running tool  115  disposed at the lower end of a working string  130 .  
         [0025]    At the upper end of the running tool  115  is an upper torque anchor  140 . Preferably, the torque anchor  140  defines a set of slip members  145  disposed radially around the torque anchor  140 . In the embodiment of FIG. 1, the slip members  145  define at least two radially extendable pads with surfaces having gripping formations like teeth formed thereon to prevent rotational movement. As illustrated, the torque anchor  140  is in its recessed position, meaning that the pads  145  are substantially within the plane of the casing  110 . In other words, the pads  145  are not in contact with the casing  110  so as to facilitate the run-in of the liner assembly  150 . The pads  145  are selectively actuated either hydraulically or mechanically or combinations thereof as known in the art.  
         [0026]    A spline assembly  225  is secured at one end to the torque anchor  140  by a plurality of upper torque screws  230  and secured at the other end to an axially movable expander tool  125  by a plurality of lower torque screws  235 . As used herein, a spline assembly means a mechanical torque connection between a first and second member. Typically, the first member includes a plurality of keys and the second member includes a plurality of keyways. When rotational torque is applied to the first member, the keys act on the keyways to transmit the torque to the second member. Additionally, the spline assembly permits axial movement between the first and second member while maintaining the torque connection. In this respect, the torque anchor  140  maintains the expander tool  125  rotationally stationary while permitting the expander tool  125  to move axially.  
         [0027]    The axially movable expander tool  125  is disposed on a threaded mandrel  135 . Expander tools are well known in the art and are generally used to radially enlarge an expandable tubular by urging the expander tool axially through the tubular, thereby swaging the tubular wall radially outward as the larger diameter tool is forced through the smaller diameter tubular member. In the embodiment shown, the expander tool  125  includes female threads formed on an inner surface thereof that mate with male threads formed on the threaded mandrel  135 . As the threaded mandrel  135  is rotated, the expander tool  125  moves axially through the hanger  200  to expand it outward in contact with the casing  110 . It is to be understood, however, that other means may be employed to urge the expander tool  125  through the hanger  200  such as hydraulics or any other means known in the art. Furthermore, the expander tool  125  may be disposed in the hanger  200  in any orientation, such as in a downward orientation as shown for a top down expansion or in an upward orientation for a bottom up expansion. Additionally, an expandable tool may be employed. Preferably, the expandable tool moves between a first smaller diameter and a second larger diameter, thereby allowing for both a top down expansion and a bottom up expansion depending on the directional axial movement of the expandable tool.  
         [0028]    Disposed below the threaded mandrel  135  is a swivel  120 . Generally, the swivel  120  permits the relative rotation of a threaded mandrel  135  while the supporting torque anchor  140 , and the hanger  200 , remain rotationally stationary. A downhole tool  160  with extendable members  165  is located below the swivel  120 .  
         [0029]    As shown in FIG. 1, the downhole tool  160  is in its extended position, meaning that the extendable members  165  are in contact with the inner surface of the liner assembly  150  so as to secure the liner assembly  150  to the running tool  115 . The extendable members  165  are selectively actuated either hydraulically or mechanically or both as known in the art. Furthermore, a fluid outlet  170  is provided at the lower end of the downhole tool  160 . The fluid outlet  170  serves as a fluid conduit for cement to be circulated into the wellbore  100  in accordance with the method of the present invention.  
         [0030]    The liner assembly  150  includes the expandable hanger  200  of this present invention. The expandable hanger  200  comprises of a plurality of formations that are illustrated as a plurality of ribs  205  formed on the outer surface of the hanger  200 . The plurality of ribs  205  are circumferentially spaced around the hanger  200  to provide support for the liner assembly  150  upon expansion of the hanger  200 . As illustrated, a plurality of inserts  210  are disposed on the ribs  205 . The inserts  210  provide a gripping means between the outer surface of the hanger  200  and the inner surface of the casing  110  within which the liner assembly  150  is coaxially disposed. The inserts  210  are made of a suitably hardened material, and are attached to the outer surface of the ribs  205  of the hanger  200  through a suitable means such as soldering, epoxying or other adhesive methods, or via threaded connection. In the preferred embodiment, inserts  210  are press-fitted into preformed apertures in the outer surface of the ribs  205  of the hanger  200 . After expansion, the inserts  210  are engaged with the inner surface of the surrounding casing  110 , thereby increasing the ability of the expanded hanger  200  to support the weight of the liner assembly  150  below the expanded portion.  
         [0031]    In the preferred embodiment, the inserts  210  are fabricated from a tungsten carbide material. However, another fabrication material may be employed, so long as the material has the capability of gripping the inner surface of the casing  110  during expansion of the hanger  200 . Examples of fabrication materials for the inserts  210  include ceramic materials (such as carbide) and hardened metal alloy materials. The carbide inserts  210  define raised members fabricated into the hanger  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 ribs  205  of the hanger  200 . The gripping means may also include a plurality of long inserts defined on the outside diameter of the hanger  200 , thus creating a plurality of flutes (not shown) between the plurality of long inserts. Alternatively, the gripping means may define a plurality of hardened tooth patterns added to the outer surface of the ribs  205  of the hanger  200 .  
         [0032]    In the embodiment shown in FIG. 1, the liner assembly  150  includes a liner seal  155  disposed below the expandable hanger  200 . The primary purpose of the liner seal  155  is to seal off the expandable hanger  200  after a cementation operation is complete, as will be discussed in a subsequent paragraph. Generally, the liner seal  155  creates a fluid seal between the liner assembly  150  and the casing  110  upon expansion of the liner seal  155 . In the preferred embodiment, the liner seal  155  is fabricated from an elastomeric material. However, other material may be employed that is capable of creating the fluid seal sought to be obtained between the expanded portion of the liner assembly  150  and the casing  110 . Typically, the liner seal  155  is disposed around the liner assembly  150  by a thermal process, or some other well known means.  
         [0033]    Although the liner assembly  150  in FIG. 1 shows only one liner seal  155  disposed below the expandable hanger  200 , the invention is not limited to this particular location or the quantity illustrated. For instance, any number of liner seals may be employed with the expandable hanger  200  of the present invention and the liner seals may be placed in any location adjacent the expandable hanger  200  to create a fluid seal between the liner assembly  150  and the casing  110 . For example, the liner seal  155  may be employed both above and below the expandable hanger  200  to form a fluid seal between the liner assembly  150  and the casing  110 .  
         [0034]    [0034]FIG. 2 is a cross-sectional view illustrating the expander tool  125  partially expanding the solid expandable hanger  200 . As shown, the liner assembly  150  is positioned proximate the lower end of the casing  110 . Thereafter, the upper torque anchor  140  is actuated, thereby extending the pads  145  radially outward into contact with the surrounding casing  110 . Subsequently, rotational force is transmitted through the working string  130  to the threaded mandrel  135 . The swivel  120  permits the threaded mandrel  135  to rotate in a first direction while the torque anchor  140 , the spline assembly  225 , expander tool  125 , and liner assembly  150  remain stationary. As the threaded mandrel  135  rotates, the expander tool  125  moves axially in a first direction through the expandable hanger  200  causing the hanger  200  to expand radially outward forcing the inserts  210  to contact the inner surface of the casing  110  as illustrated. The expander tool  125  continues to expand the entire length of the expandable hanger  200  until it reaches a predetermined point above the liner seal  155 . At that point, the expansion is stopped to prevent expanding the liner seal  155 , in anticipation of cementing.  
         [0035]    [0035]FIG. 3 is a cross-sectional view taken along line  3 - 3  in FIG. 2 to illustrate the orientation of the expander tool  125  in the solid expandable hanger  200 . As clearly shown, the expander tool  125  includes a plurality of formations illustrated as a plurality of expander ribs  175  and a plurality of expander flutes  185  circumferentially spaced around the expander tool  125 . The plurality of expander ribs  175  are generally tapered members defining a first outer diameter at a first end smaller than a second outer diameter at a second end thereof. Also clearly shown, the hanger  200  includes a plurality of hanger flutes  220  disposed between the plurality of ribs  205 .  
         [0036]    [0036]FIG. 4 is a cross-sectional view taken along line  4 - 4  of FIG. 2 illustrating the expander tool  125  during the expansion of the solid expandable hanger  200 . The expander tool  125  is oriented in the expandable hanger  200  by aligning the plurality cone flutes  185  with the plurality of ribs  205 . Therefore, as the expander tool  125  moves axially through the hanger  200 , the cone ribs  175  apply a force on the hanger flutes  220 , causing them to expand out radially, which in turn urges the ribs  205  on the hanger  200  out radially as the inserts  210  penetrate the surrounding casing  110 . At this point the hanger flutes  220  are free to move out radially while the radially stationary ribs  205  are accommodated by the cone flutes  185 . Given that the radial extension of the hanger flutes  220  are dictated by the diameter of the cone ribs  175 , they never contact the surrounding casing  110 . In this manner, the cement bypass ports  215  are formed therefore providing a fluid passageway between the hanger  200  and the surrounding casing  110  during the cementing operation.  
         [0037]    [0037]FIG. 5 is a cross-sectional view illustrating the release of the running tool  115  prior to a cementing operation. It is desirable to release the running tool  115  from the liner assembly  150  prior to cementing it in the wellbore  100  to prevent the foreseeable difficulty of releasing the tool  115  after the cementation operation. As shown, the torque anchor  140  is also in its recessed position, meaning that the pads  145  have been retracted and are no longer in contact with the casing  110 . Furthermore, the hanger  200  supports the weight of the liner assembly  150  therefore the downhole tool  160  is deactivated, meaning that the extendable members  165  have been retracted and are no longer in contact with the inner surface of the liner assembly  150  so as to release the liner assembly  150  from the running tool  115 .  
         [0038]    [0038]FIG. 6 is a cross-sectional view illustrating the cementation of the liner assembly  150  within the wellbore  100 . Preferably, cement is pumped through the working string  130 , the running tool  115 , and the fluid outlet  170  to a cement shoe (not shown) or another means known in the art to distribute the cement. As indicated by arrow  180 , the cement is circulated up an annulus  190  formed between the liner assembly  150  and the wellbore  100  and past the liner seal  155  into the cement bypass ports (not shown) of the expandable hanger  200 . Thereafter, the cement flows through the bypass ports and exits into the inner diameter of the surrounding casing  110 .  
         [0039]    [0039]FIG. 7 is a cross-sectional view illustrating the expansion of the liner seal  155  after the cementing operation. As shown, the liner assembly  150  has been completely cemented in the wellbore  100 . As further shown, the torque anchor  140  is once again actuated, thereby extending the pads  145  radially outward into contact with the surrounding casing  110 . Subsequently, rotational force is transmitted through the working string  130  to the threaded mandrel  135 . The swivel  120  permits the threaded mandrel  135  to rotate in the first direction while the supporting torque anchor  140 , the spline assembly  225 , and the expander tool  125  remain rotationally stationary. As the threaded mandrel  135  rotates in the first direction, the expander tool  125  moves axially in the first direction through the expanded portion of the hanger  200  and then through the liner seal  155 . Subsequently, the liner seal  155  expands radially outward forcing the elastomeric material to form a fluid seal between the liner assembly  150  and the surrounding casing  110 . Alternatively, a rotary expansion tool (not shown) or a cone shaped mandrel (not shown) may be employed to expand the liner seal  155 . In either case, the cement bypass ports (not shown) are sealed off to prevent any further migration of fluid through the expandable hanger  200  from micro-annuluses that may have formed during the cementing operation.  
         [0040]    [0040]FIG. 8 is a cross-sectional view illustrating the fully expanded solid expandable hanger  200  after the running tool  115  has been removed. As shown, the expandable hanger  200  is fully engaged with the lower portion of the surrounding casing  110  and consequently supporting the entire weight of the liner assembly  150  by way of the inserts  210  on the hanger ribs  205 . As further shown, the liner seal  155  has been expanded radially outward and is therefore creating the lower fluid seal between the liner assembly  150  and the surrounding casing  110 .  
         [0041]    Creating an attachment and a seal between two tubulars in a wellbore can be accomplished with methods that use embodiments of the expandable hanger as described above. A method of completing a wellbore includes placing a first tubular coaxially within a portion of a second tubular, the first tubular including a plurality of formations on an outer surface thereof to provide a frictional relationship between the first tubular and the second tubular while leaving a fluid path through the expanded connection. The method also includes positioning an expander tool within the first tubular at a depth proximate the plurality of formations on the first tubular. The method further includes urging the expander tool axially through the first tubular to expand the first tubular into frictional contact with the second tubular and forming a fluid path through an overlapped portion between the first and second tubulars. Therefore, the apparatus and methods disclosed herein for using embodiments of the expandable hanger permits the connection of two tubulars within a wellbore.  
         [0042]    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.