Abstract:
The present invention generally relates to an apparatus for use in a wellbore. In one aspect, the apparatus includes a first tubular having a connection means at the end thereof and a second tubular having a mating connection means at an end thereof. The connection means and mating connection means are constructed and arranged to form a connection between the tubulars. The apparatus further includes a swelling elastomer disposable between the connection means and the mating connection means, the swelling elastomer expandable upon contact with an activating agent. In another aspect, the invention provides a method for utilizing an expandable connection in a wellbore.

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 attaching and sealing two tubulars. More particularly still, the invention relates to maintaining a seal at the connection point between the two tubulars during the expansion operation.  
           [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 typically 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 overlaps 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]    Operators are continually searching for means to improve functionality and reduce costs in their drilling operations. This has been achieved in the past in relatively small increments by such things as discrete technological improvements and novel contracting strategies. It is inevitable that these incremental gains are diminishing. The industry needs a radical “next step.” The monobore well is this step.  
           [0007]    Monobore wells have a uniform through-bore from the surface casing to the production zones. Today, wells are constructed by progressively securing the borehole with several intermediate casings before the production casing is run. Monobore well technology will eliminate these intermediate casing strings through the use of expandable liners. Monobore wells consist of a sequence of expandable liners that are run through the existing casing, then expanded to achieve the same post-expansion through-bore. A monobore well features each progressive borehole section being cased without a reduction of casing size.  
           [0008]    Many conventional wells drilled today consist of a 26-inch or 30-inch conductor and 20-inch or 18 5.8-inch surface casing (or similar sizes), and have several intermediate casings before a 9 5.8-inch production casing is run. The monobore well offers the advantage of being able to start with a much smaller surface casing but still resulting in a 9 5.8-inch production casing. Because top-hole sizes are reduced, less drilling fluid is required and fewer cuttings are created which means less cleaning of the cuttings, and the environmental problem of drilling waste disposal is reduced. Also, with a smaller surface casing size (and only one other actual casing string), the wellhead can be simplified, as can the BOP&#39;S (blow out protectors) and risers. Many drilling plans include a contingency casing or liner to allow for problem zones. Careful planning of a monobore well enables problem zones to be secured without sacrificing a casing size in the well design. Additionally, running expandable liners instead of long casing strings will result in valuable time savings.  
           [0009]    Generally, expandable liners for a monobore well or a conventional well are constructed of 38-foot long tubulars. Each expandable liner includes a female thread at the top and a male thread at the bottom. Typically, the top and bottom threaded portions are expandable in the same manner as the expandable liner. A series of expandable liners are commonly screwed together as they are lowered in the wellbore. As the female thread is connected with the male thread, a metal-to-metal seal is created. Additionally, two external O-rings may be disposed on the threads between the two expandable liners to enhance the sealing effect between the male and female thread.  
           [0010]    After the entire length of expandable liner is deployed into the wellbore, the expandable liners are typically expanded by the use of a cone-shaped mandrel or by an expander tool. The expander tool is generally run into the wellbore on a tubular string and includes expandable, fluid actuated members disposed on a body. There are a number of advantages to expanding solids using a rotary tool as the expander tool, rather than existing methods involving driving a fixed cone through the pipe. For example, the process is controllable, thereby allowing expansion to be initiated when and wherever required. If necessary, the expander tool can be recovered in a mid-expansion position, and redeployed to continue the operation. Further, the rollers reduce the friction between the tool and the pipe, which allows the expandable liners to be expanded from the top down.  
           [0011]    While expanding expandable liners in a wellbore offers obvious advantages, there are problems associated with using the technology. By plastically deforming the expandable liner, the cross-sectional thickness of the expandable liner is necessarily reduced. As a result, the tight metal-to-metal seal created between the female thread and the male thread becomes slack, thereby jeopardizing the seal at the threaded connection. Simply increasing the initial cross-sectional thickness of the expandable liner to compensate for the reduced wall thickness after expansion results in an increase in the amount of force needed to expand the expandable liner.  
           [0012]    A need, therefore, exists for an expandable liner connection between two expandable tubulars that maintains its rigidity after the expansion process. There is a further need for an expandable liner connection providing an effective seal at the threaded connection between the expandable liner strings. There is yet a further need for an effective method for ensuring wellbore fluid will not leak through the expandable liners at the threaded connection.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention generally relates to an apparatus for use in a wellbore. In one aspect, the apparatus includes a first tubular having a connection means at the end thereof and a second tubular having a mating connection means at an end thereof. The connection means and mating connection means are constructed and arranged to form a connection between the tubulars. The apparatus further includes a swelling elastomer disposable between the connection means and the mating connection means, the swelling elastomer expandable upon contact with an activating agent.  
           [0014]    In another aspect, the invention provides a method for utilizing an expandable connection in a wellbore. The method includes running an assembly on a tubular string into the wellbore. The assembly includes a first tubular having a connection means, a second tubular having a mating connection means, the connection means and mating connection means are constructed and arranged to form a connection between the tubulars. The assembly also includes a swelling elastomer disposable between the connection means and the mating connection means. The method further includes the steps of applying a force to an inner surface of the connection and expanding the assembly radially outward. The method also includes the step of exposing the swelling elastomer to an activating agent, thereby ensuring that a space within the connection is substantially filled with the swelling elastomer.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    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.  
         [0016]    [0016]FIG. 1A is a cross-sectional view illustrating an expandable liner of this present invention and a running assembly being lowered into the wellbore on a work string.  
         [0017]    [0017]FIG. 1B is an enlarged cross-sectional view illustrating a swelling elastomer disposed on a threaded connection between the upper tubular and the lower tubular.  
         [0018]    [0018]FIG. 2 is an exploded view of an exemplary expander tool.  
         [0019]    [0019]FIG. 3 is a cross-sectional view illustrating the expandable liner partially expanded into contact with the wellbore by the expander tool.  
         [0020]    [0020]FIG. 4A is a cross-sectional view of the expandable liner fully expanded into contact with the surrounding wellbore.  
         [0021]    [0021]FIG. 4B is an enlarged cross-sectional view illustrating the swelling elastomer providing an effective seal at the threaded connection. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    [0022]FIG. 1 is a cross-sectional view illustrating an expandable liner  150  of the present invention and a running assembly  170  being lowered into the wellbore  100  on a work string  140 . As depicted, a casing string  105  is disposed in the wellbore  100 , however, it should be noted that aspects of this present invention are not limited to use with a partially cased wellbore, but rather can be also be used with a cased or uncased wellbore. An uncased wellbore is known in the industry as an open hole wellbore that typically remains open to provide a flow path for hydrocarbons from the surrounding formation. Thereafter, the wellbore may be closed by employing the present invention in a similar manner as described below.  
         [0023]    The running assembly  170  includes an upper torque anchor  160  to secure the running assembly  170  and the expandable liner  150  in the casing  105 . As shown in FIG. 1A, the upper torque anchor  160  is in a retracted position to allow the running assembly  170  to place the expandable liner  150  in the desired location for expansion of the liner  150 . Additionally, a lower torque anchor  125 , which is disposed below the upper torque anchor  160 , is used to attach the expandable liner  150  to the running assembly  170 . A motor  145  is disposed at the lower end of the torque anchor  125  to provide rotational force to turn an expander tool  115 .  
         [0024]    [0024]FIG. 1A depicts the expander tool  115  with rollers  116  retracted, so that the expander tool  115  may be easily moved and placed in the desired location for expansion of the liner  150 . When the expander tool  115  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 expandable liner  150 , thereby expanding the liner  150  into the wellbore  100 . Generally, hydraulic fluid (not shown) is pumped from the surface to the expander tool  115  through the work string  140 .  
         [0025]    The expandable liner  150  includes an upper tubular  180  having an inner surface  183  and an outer surface  184 . The upper tubular  180  also includes a connection means or a threaded portion  182  on the inner surface  183  which is typically known to one skilled in the art as a female thread. As shown, the expandable liner  150  further includes a lower tubular  185  having an inner surface  188  and an outer surface  189 . Additionally, the lower tubular  185  includes a connection means or threaded portion  187  on the outer surface  189 , which is typically known to one skilled in the art as a male thread. The connecting means of the upper and lower tubulars may be brought together to form a threaded connection  175 .  
         [0026]    [0026]FIG. 1B is an enlarged cross-sectional view illustrating a swelling elastomer  205  disposed on the threaded connection  175  between the upper tubular  180  and the lower tubular  185 . A coating of the swelling elastomer  205  may be applied to the threaded portion  182  of the upper tubular  180  prior to the connection to the lower tubular  185 . Thereafter, the threaded portion  182  on the upper tubular  180  mates with the threaded portion  187  on the lower tubular  185  to form the threaded connection  175 . In this respect, the swelling elastomer  205  creates a fluid tight seal between the tubulars  180 ,  185  by filling the voids between the metal-to-metal seal created in the threaded connection  175 . Alternatively, the swelling elastomer  205  may be applied to the threaded portion  187  on the lower tubular  185  prior to the connection to the upper tubular  180 . Alternatively still, the swelling elastomer  205  may be applied to both the threaded portion  182  on the upper tubular  180  and the threaded portion  187  on the lower tubular  185 . Preferably, a very thin coat of swelling elastomer  205  is applied to the threaded portions  182 ,  187 . However, the thickness of the swelling elastomer  205  coating may vary depending on the size and the type of thread used to connect the tubulars  180 ,  185 . Additionally, FIG. 1B illustrates the threaded connection  175  with the swelling elastomer  205 . However, it should be understood that this invention is not limited to threaded connections but rather could be used with other types of expandable connections.  
         [0027]    In one embodiment, the swelling elastomer  205  is a cross-linked polymer that will swell multiple times its initial size upon activation by an activating agent. Generally, the activating agent stimulates the polymer chains of the swelling elastomer  205  both radial and axially. In the preferred embodiment, an activating agent such as a wellbore fluid or some form of hydraulic fluid activates the swelling elastomer  205 . However, other embodiments may employ different types of swelling elastomers that are activated by other forms of activating agents.  
         [0028]    To keep the swelling elastomer  205  in an inactivated state during the run-in operation, the elastomer  205  is maintained within a predetermined location. In the preferred embodiment, the threaded portions  182 ,  187 , substantially enclose the swelling elastomer  205 , thereby preventing any fluid or activating agent from contacting the swelling elastomer  205 .  
         [0029]    The expandable liner  150  of the present invention is expanded by the expander tool  115  acting outwardly against the inside surfaces  183 ,  188  of the upper and lower tubulars  180 ,  185 . FIG. 2 is an exploded view of an exemplary expander tool  115  for expanding the liner  150 . The expander tool  115  has a body  102  that 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  115 .  
         [0030]    The central body part  102  of the expander tool  115  shown in FIG. 2 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  115 . 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  115  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  115  by way of the radial perforations in the tubular core. In this manner, pressurized fluid provided from the surface of the well, via the work string (not shown), can actuate the pistons  120  and cause them to extend outward allowing the rollers  116  contact the inner surfaces  183 ,  188  of the tubulars  180 ,  185 .  
         [0031]    [0031]FIG. 3 is a cross-sectional view illustrating the expandable liner  150  partially expanded into contact with the wellbore  100  by the expander tool  115 . The upper torque anchor (not shown) is energized to ensure the running assembly and the expandable liner  150  will not rotate during the expansion operation. Hydraulic pressure is increased to a predetermined pressure to actuate the pistons in the expander tool  115 . Upon actuation of the pistons, the rollers  116  are extended until they contact the inner surface  183  of the expandable tubular  180 . The rollers  116  of the expander tool  115  are further extended until the rollers  116  plastically deform the tubular  180  into a state of permanent expansion. The motor (not shown) rotates the expander tool  115  during the expansion process, and the tubular  180  is expanded until the outer surface  184  contacts the inner surface of the wellbore  100 . As the expander tool  115  expands the expandable liner  150 , the cross-sectional thickness of the expandable liner  150  is necessarily reduced. Therefore, as the rollers  116  expand the threaded connection  175 , the initially tight fit between the threaded portions  182 ,  187  become slackened, thereby affecting the seal at the threaded connection  175 . The slacked threaded connection  175  allows wellbore fluid in an annulus  165  to contact the swelling elastomer  205 , thereby causing the polymer chains of the elastomer  205  to shift positions, and expand the swelling elastomer  205  both laterally and radially as shown in FIGS. 4A and 4B.  
         [0032]    [0032]FIG. 4A is a cross-sectional view of the expandable liner  150  fully expanded into contact with the surrounding wellbore  100 . As depicted, the upper tubular  180 , the threaded connection  175  and the lower tubular  185  are fully expanded into the wellbore  100 . As clearly shown on FIG. 4B, the swelling elastomer  205  has sealed off any voids in the threaded connection  175 . In this manner, the liner  150  of this present invention may be expanded into the wellbore  100  without any leakage of the wellbore fluid through the threaded connection  175  of the liner  150 .  
         [0033]    [0033]FIG. 4B is an enlarged cross-sectional view illustrating the swelling elastomer  205  providing an effective seal at the threaded connection  175 . As shown, the threaded portions  182 ,  187  have shifted as the wall of the tubulars  180 ,  185  became thin during the expansion operation. The slack between the threaded portions  182 ,  187  breaks the fluid tight seal, thereby allowing wellbore fluid in the annulus to leak through the threaded connection  175  to expose the swelling elastomer  205  to the wellbore fluid. Subsequently, the wellbore fluid activates the swelling elastomer  205 , thereby causing the polymer chains to expand the swelling elastomer  205  both laterally and radially to fill the voids of the connection. In this manner, the fluid tight seal between the threaded portion  182  of the upper tubular  180  and the threaded portion  187  of the lower tubular  185  is preserved. As a result, wellbore fluid is prevented from leaking through the threaded connection  175 .  
         [0034]    In operation, the expandable liner assembly and a running assembly are lowered to a desired location in the wellbore on a work string. Thereafter, the upper torque anchor is activated to secure the liner assembly and running assembly in the wellbore. After the expander tool is located at the desired depth, hydraulic pressure is increased to a predetermined pressure to actuate the pistons in the expander tool. Upon actuation of the pistons, the rollers are extended until they contact the inner surface of the expandable liner. The rollers of the expander tool are further extended until the rollers plastically deform the liner into a state of permanent expansion. The motor rotates the expander tool during the expansion process, and the liner is expanded until the outer surface contacts the inner surface of the wellbore. As the expander tool expands the liner, the cross-sectional thickness of the expandable liner is necessarily reduced. Therefore, as the rollers expand the threaded connection, the initially tight fit between the threaded portions become slack, thereby affecting the seal at the threaded connection. The slackness at the threaded connection allows wellbore fluid in the annulus to contact the swelling elastomer, thereby causing the polymer chains of the elastomer to shift positions, and expand the swelling elastomer both laterally and radially to fill the voids in the threaded connection.  
         [0035]    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.