Abstract:
A method and apparatus for creating a seal between two coaxial strings of pipe. The method and apparatus have utility in one embodiment for sealing the annulus between the tubing and the casing within a hydrocarbon wellbore. According to the method of the present invention, an expander tool is positioned at a selected depth within the tubing, and then actuated in order to expand the tubing against the inner wall of the casing wall. The expander tool is rotated in order to provide a fluid seal in the annulus. In this way, the tubing string becomes its own packer. In the preferred embodiment, an elastomeric seal is provided around the outer surface of the tubing to enhance the fluid seal. Further, a slip ring is provided around the outer surface of the tubing to provide a gripping means between the tubing and the casing. In the preferred embodiment, rollers of the expander tool are aligned with the seal ring and slip ring before expansion.

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 sealing a tubular in a casing.  
           [0003]    2. Description of the Related Art  
           [0004]    Wellbores are typically formed by drilling and thereafter lining a borehole with 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 borehole in the earth. 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]    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.  
           [0007]    The sealing element is set when the rings move towards each other and compress the element therebetween, causing it to expand outwards into an annular area to be sealed 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 simulation 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.  
           [0008]    One problem associated with conventional sealing and slip systems of conventional downhole tools relates to the relative movement of parts required 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 direction, a run-in tool or other mechanical device must necessarily be placed in the wellbore with the sealing tool. Additionally, the slip means takes up annular space that is limited. Also, the body of a packer necessarily requires wellbore space and reduces the bore size available for production tubing, etc. Additionally, high temperatures and pressures in a wellbore can create problems due to the degradation of the elastomeric sealing element or the corrosion of the moving parts in a conventional slip assembly.  
           [0009]    Therefore, there is a need for a packer for sealing a downhole annular area which employs fewer moving parts. There is further a need for a packer which can be used to seal an annular area at high temperatures and high pressure differentials without experiencing physical degradation.  
         SUMMARY OF THE INVENTION  
         [0010]    A packer is provided that can effectively seal or pack-off a tubing-casing annulus under elevated pressures and temperatures. The packer defines an expandable tubular body that is fixed and sealed within a wellbore by plastic deformation.  
           [0011]    The packer is run into the wellbore as part of the production tubing string. The packer includes at least one elastomeric ring which is affixed to the outer surface of the tubular body. The sealing ring provides a seal between the tubular body and the casing that prevents production fluids from passing upwardly between the casing and the tubular. The packer further includes at least one slip ring, which is also affixed to the outer surface of the tubular body. The slip ring has a plurality of teeth that provide a gripping mechanism between the tubular body and the casing. In the preferred embodiment, the elastomeric ring is positioned above the slip ring.  
           [0012]    Once the tubular body is expanded, the elastomer rings are sealed between the tubular and casing. The tubular body thus becomes a packer. In this manner, the production string acts as its own packer.  
           [0013]    The packer is expanded by use of an expander tool. The expander tool is of a generally tubular nature, and employs pressure-actuated rollers which act against the inner surface of the tubular body in order to expand it against the casing. The rollers are movable from a first recessed position within the housing of the expander tool to a second extended position beyond the housing. In the preferred embodiment, the rollers have a unique multi-lobed surface contour that allows the uniform expansion of a tubular while reducing the potential of the tubular to crack.  
           [0014]    A method is further provided for sealing an annulus in a wellbore. The tubular body to be sealed to the casing is first prepared by applying at least two bands around the outside of the tubular body. The bands are spaced a distance apart, with the first band serving as the sealing ring. The second band serves as the gripping band, and is known as the slip ring. This slip ring is positioned furthest down hole along the tubular and is the first to enter the wellbore casing. When the tubular body is expanded, the slip ring allows the tubular body to grip the wall of the casing while the sealing ring seals the tubular to the casing.  
           [0015]    In practice, after the bands have been affixed to the tubular body, the tubular body is lowered into the wellbore casing. Once a desired depth has been reached, the expander tool is lowered into the wellbore casing on a working string. In one aspect of the present invention, the setting depth is located by a stop ring that has been previously installed in the production tubing  
           [0016]    The expander tool is actuated by pumping fluid down the work string and into the expander tool until the pistons are forced radially away from the housing and the rollers come in contact with the walls of the tubular body. Simultaneously, the expander is rotated within the tubular. As hydraulic pressure is increased, the tubular body is expanded until the outer wall of the tubular body is in firm contact with the inner wall of the casing and the elastomer rings are compressed between the tubular body and the casing. The tubular becomes, in effect, a packer and eliminates the need for a separate packer device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    So that the manner in which the above-recited features, advantages and objects 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 the 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 section view of a tubular body within a casing according to the present invention.  
         [0020]    [0020]FIG. 2 is a perspective view of an expander tool according to the present invention. One of the roller assemblies is shown in an exploded state.  
         [0021]    [0021]FIG. 3 is a cross-sectional view of the expander tool of FIG. 1 according to the present invention cut across one row of rollers. The rollers are shown in three different positions in this view. In P 1 , the roller is shown in its recessed position. In P 2 , the roller is shown in its expanded state. And in P 3 , the roller is shown in an exploded view.  
         [0022]    [0022]FIG. 4 is a sectional view of the expander tool inside a tubular body. The rollers are in their recessed state within the plane of the expander tool body.  
         [0023]    [0023]FIG. 5 is a section view of a tubular body partially expanded by an expander tool. The rollers are in their expanded state.  
         [0024]    [0024]FIG. 6 is a cross-sectional view of a wellbore having a production tubing disposed therein. A tubular body within the production tubing has been expanded against the casing so as to form a packer. The expander tool is now being removed from the wellbore. 
     
    
     DETAILED DESCRIPTION  
       [0025]    [0025]FIG. 1 is a partial sectional view of a packer  10  according to the present invention. The packer  10  defines a tubular body  202  placed in series with a string of production tubing  202 . In the preferred embodiment, the tubular body  202  is simply a joint or portion of a joint of the production tubing  202  itself. However, it is within the scope of this invention to utilize a specially configured tubular body, such as a shorter and more malleable joint of pipe, for expansion into a string of casing  206 .  
         [0026]    The tubular body  202  is fabricated from a steel or metal alloy material. The material must be strong enough to withstand the high temperatures and pressure differentials prevailing within the downhole environment. However, it must be sufficiently malleable to be plastically deformed by expansion into the casing  206 .  
         [0027]    In the view of FIG. 1, the tubular body  202  has not been expanded. The tubular body  202  is disposed concentrically within a string of casing  206 . For purposes of the present inventions, the term concentrically means that two tubulars have been positioned coaxially, with one residing within the other. The outer surface of the tubular body  202  is separated from the inner surface of the casing  206  by an annulus  204  to permit a clearance between the casing  206  and the tubular body  202  during run-in. The casing  206  is generally formed of steel, iron or a similar material and is typically cemented into the wellbore  208 . A cemented annulus is shown at  220  in FIG. 1.  
         [0028]    Affixed to the outer surface of the tubular body  202  is a plurality of bands  212  and  210 . In the preferred embodiment for the apparatus of the present invention, the plurality of bands defines at least one sealing ring  212  and at least one slip ring  210 . The sealing ring  212  is preferably fabricated from an elastomeric material, and provides a circumferential seal between the tubular body  202  and the casing  206  when the tubular body  202  is expanded against the casing  206 . The seal ring  212  prevents production fluids from passing upwardly between the casing  206  and the production tubing  202  after the tubular body  202  has been expanded.  
         [0029]    The slip ring  210  has a plurality of teeth  214  formed along its outer surface. The purpose of the slip ring  210  is to provide a gripping means between the tubular body  202  and the casing  206  upon expansion of the tubular body  202 . The gripping teeth  214  are designed to grip the inner surface of the casing  206  and to prevent the tubular body  202  from slipping into the wellbore  208 . In the preferred embodiment, the slip ring  210  is circumferentially disposed about the outer surface of the tubular body  202 . However, it is within the scope of this invention to provide slip means of other configurations, such as a plurality of buttons (not shown) having carbide teeth, flame sprayed carbide aggregates, or other carbide-based gripping means.  
         [0030]    In one aspect, the elastomeric seal ring  212  is spaced apart from the slip ring  210  on the outer surface of the tubular body  202 . In the preferred embodiment, the seal ring  212  is positioned above the slip ring  210 .  
         [0031]    After the tubular body  202  is placed within the wellbore  208 , it is expanded so that the seal ring  212  and slip ring  210  are in contact with the casing  206 . Expansion is done through use of an expander tool, such as the expander tool  50  of FIG. 2. FIG. 2 is a partially exploded view of an expander tool  50 . The expander tool  50  comprises a housing that supports a plurality of roller assemblies  101 . The expander tool  50  includes a neck  104 , a shoulder  106 , a body  128  and a lower portion  130 . The neck  104  has a threaded interior  122 . The threads  102  extend along the length of the neck  104  and facilitate the connection of the expander tool  50  to a run-in string  302 .  
         [0032]    The shoulder  106  of the expander tool  50  is formed to coaxially align and connect the neck  102  to the body  128 . In the embodiment shown, the body  128  is formed in a cylindrical shape with a plurality of apertures  108  formed therein. The apertures  108  are formed in two rows of three apertures  108  per row. The apertures  108  within each row are spaced equidistantly apart from each other, and the apertures  108  are generally co-planar to one another in a row. Other configurations of an expander tool  50  may be utilized for expanding a tubular body.  
         [0033]    The apertures  108  receive the roller assemblies  101 . The roller assemblies  101  include pistons  110  which move from a first recessed position within the apertures  108  to a second extended position. The roller assemblies  101  are shown in these two positions in FIG. 3. In position P 1 , the roller assembly  101  is shown in its recessed position. In P 2 , the roller assembly  101  is shown in its expanded state. The roller assembly  101  is also shown in an exploded view in P 3 .  
         [0034]    As demonstrated in FIG. 3, the pistons  110  are coupled to outwardly facing rollers  114 . The pistons  110  have a cylindrical shape with a seal  126  disposed on one end and a cup  116  formed in the opposite end. The pistons  110  are slidingly disposed in the apertures  108  first and are retained by a pair of retaining plates  118 A and  118 B. To prevent pistons  110  from falling out of the body  128 , a pair of flats  144 A and  144 B are formed in the sides of the pistons  110 . The flats  144 A,  144 B define a pair of flanges. The retaining plates  118 A and  118 B are fastened to the body  128  by socket head cap screws  120 . When fully extended, the flats  144 A,  144 B abut the plates  118 A and  118 B. The cup  116  formed within the piston  110  accommodates a portion of the roller  114  that is rotatably affixed by an axle  112  into the cup  116 . The axle  112  is disposed through an aperture  140 A formed in the piston  110 , then passes through a central bore  142  located in the roller  114  before being secured in a second aperture  140 B formed in the piston  110 .  
         [0035]    Disposed throughout the center of expander tool  50  runs a conduit  122 , seen in FIG. 3. The conduit  122  carries hydraulic fluid or mud to the pistons  110 . The conduit  122  couples hydraulic fluid to the radial conduits  124  in order to apply pressure to pistons  110  and force them radially outward from the body  128 .  
         [0036]    The rollers  114 , as seen in the perspective view of FIG. 1, have a contoured shape comprising three elliptical lobes  132 ,  136  and  138  (respectively top, center and bottom lobes) interspaced by two spacing sections  134 A and  134 B. In one embodiment, the roller  114  is formed from a single piece of material and has a bore  142  formed along its central axis. The top lobe  132  and the bottom lobe  138  are of similar proportions (diameter and radius), while the intermediate lobe  136  is smaller. Thus, a “bow-tie” shape is presented.  
         [0037]    Advantages have been discovered incident to the use of a bow-tie profiled roller  114  over the more conventional “barrel” shaped roller (not shown). The bow-tie shape allows for a narrower point of contact between the roller surface  114  and the tubular  202  to be expanded. In this respect, less force is required to expand a tubular  202  at a single radial point than over an extended surface area. This, in turn, facilitates the transition within the tubular  202  from elastic deformation to plastic deformation. Thus, a tighter seal can be accomplished. The bow tie profile further allows for two separate points of radial contact, an upper  132  and lower  138  point, thereby doubling the seal contact points  402 ,  406 . The intermediate roller point  136  aids further in the expansion of the tubular  202 .  
         [0038]    While the preferred embodiment for expansion of the tubular body  202  employs rollers  114  having a bow-tie profile, it is understood that other profiles may be employed for rollers  114 . It is within the scope of this invention to utilize other roller shapes such as a “barrel” shape, for example (not shown).  
         [0039]    In order to expand the tubular body  202  to form a packer  10 , an expander tool, such as the expander tool  50  of FIG. 2, is run into the tubing string  12 . The expander tool  50  is located at a depth adjacent the tubular body  202  to be expanded, as demonstrated in FIG. 4. To assist in the location of the expander tool  50 , a positioning member  216  may optionally be employed within the tubular body  202 . The positioning ring  216  is disposed within the interior of the tubular body  202 . The positioning ring  216  is formed having an interior chamfer or bevel  218  along its inner diameter. This bevel  218  serves as a landing profile, and is used to land the expander tool  50  of FIG. 1 within the tubular body  202 . The positioning ring  216  may be press-fit, welded or the like affixed to the interior surface of the tubular body  202 , and is positioned below the slip ring  210 . It is, however, within the scope of this invention to utilize other types of positioning members, or to use a locator in lieu of a positioning member.  
         [0040]    The expander tool  50  is lowered into the tubular body  202  until the lower portion  130  abuts the bevel  218  of the positioning ring  216 . The rollers  214  of the expander tool  50  are preferably aligned with the seal ring  210  and slip ring  212 , respectively.  
         [0041]    [0041]FIG. 4 is a partial sectional view of the expander tool  50  inside the tubular body  202  according to the present invention. FIG. 4 displays the expander tool  50  with the pistons  110  and the rollers  114  retracted within the perimeter of the body  128  as it would appear during run-in. FIG. 4 also depicts the mating relationship between the mating cone  130  and the positioning ring  216  when the expander tool  50  is positioned for use in the tubular body  202 . The positioning ring  216  positions the pistons  110  and the rollers  114  into alignment with the bands  212  and  210 . The expander tool  50  is lowered into the tubular body  202  by a run-in string of pipe  302  threaded to the neck portion  104  of the expander tool  50 .  
         [0042]    [0042]FIG. 5 is a section view of the tubular body  202  being expanded by the expander tool  50  according to the present invention. In practice, after the expander tool  50  has been lowered into the tubular body  202  at the end of run-in string  302  and aligned with positioning ring  216 , hydraulic fluid or mud (not shown) is pumped from the fluid source through the string of pipe  302  into the body  128 . A fluid source is shown schematically at  414 . The fluid travels through conduits  212  into the piston apertures  108 , forcing the roller assemblies  101  radially outward. As such, the pistons  110  move radially outward and rollers  114  come in contact with and begin to plastically deform tubular body  202 . At the same time, the expander tool  50  is rotated from the surface of the well (shown schematically at  412 ) or by a mud motor (not shown), causing a series of annular rings  402 ,  404  and  406  to be initially formed along the interior surface of the tubular body  202 .  
         [0043]    The pumped fluid exits the expander tool  50  through one or more nozzles at the lower portion  130  of the tool  50 . In the embodiment of FIG. 5, a single nozzle  152  serves as a sized orifice, and also as the outlet port for bore  122 . As fluid is pumped through the nozzle  152 , critical flow is reached. In one embodiment, the pistons  110  are actuated at the point of critical flow. As the hydraulic fluid is pumped through the central aperture  122 , differential pressure created between the hydraulic fluid being pumped into the housing and the hydraulic fluid flowing through the housing out conduit  122  creates the radial forcing pressure on the pistons  110 . As the rollers  114  create the annular rings  402 ,  404  and  406  within the interior surface of the tubular body  202 , the exterior portion of the tubular body  202  is expanded outward toward the casing  206 . The outward expansion of the tubular body  202  continues until seal ring  210  and slip ring  212  are compressed against the interior surface of the casing  206 . Sufficient pressure is applied by the rollers  114  to create a contoured seal between the elastomeric ring  212  and the casing  206 . Further, the pressure is enough to prevent slip ring  210  from moving within the casing  206 .  
         [0044]    To provide yet a greater seal between the tubular body  202  and the casing  206 , the run-in string  302  may be translated vertically within the wellbore  208 . This has the effect of lifting and lowering the expander tool  50  so as to expand an additional length of the tubular body  202 . However, this additional step is considered optional by the inventors, and is not required when a bow-tie shaped profile is employed for the rollers  114 .  
         [0045]    After the tubular body  202  has been expanded and sealed within the casing  206 , hydraulic pressure is removed or released. In one embodiment, a pressure differential causes the pistons  110  to be retracted into the body  128  of the expander tool  50  and allows the expander tool  50  to be removed from the tubular body  202 . In another embodiment, the rollers  114  are braised inward with some brazens member.  
         [0046]    After the expansion operation, the expander tool  50  can then be withdrawn from the wellbore  208  by pulling the working tubular  302 . FIG. 6 is a cross-sectional view of a wellbore  208  having a production tubing  202  disposed therein, and showing an expander tool  50  being removed form the wellbore  208 . The production tubing  202  has been expanded against the casing  206  so as to form a packer  10 . The expander tool is now being removed from the wellbore  208 . The production tubing  202  now functions as both a conduit for production fluids and also as an annular packer  10 .  
         [0047]    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.