Abstract:
Apparatuses for restricting fluid flow through a well conduit comprise a tubular member having a seat member disposed within the tubular member for receiving a plug element. One or both of the seat member or the plug element comprise at least one shape-memory material to facilitate the plug element being able to land on the seat and/or to facilitate the plug element to pass through a seat member or other restriction in the tubular member either before or after landing on a seat.

Description:
BACKGROUND 
       [0001]    1. Field of Invention 
         [0002]    The present invention is directed to apparatuses for restricting fluid flow through a conduit or tubular member within oil and gas wells and, in particular, to apparatuses having one or both of a shape-memory seat or plug element that facilitate either passing the plug element through a seat or restriction disposed in the tubular member, or facilitate landing the plug element on the seat. 
         [0003]    2. Description of Art 
         [0004]    Ball seats are generally known in the art. For example, typical ball seats have a bore or passageway that is restricted by a seat. The ball or plug element is disposed on the seat, preventing or restricting fluid from flowing through the bore of the ball seat and, thus, isolating the tubing or conduit section in which the ball seat is disposed. As force is applied to the ball or plug element, the conduit can be pressurized for tubing testing or tool actuation or manipulation, such as in setting a packer. Ball seats are used in cased hole completions, liner hangers, flow diverters, frac systems, and flow control equipment and other systems. 
         [0005]    Although the terms “ball seat” and “ball” are used herein, it is to be understood that a drop plug or other shaped plugging device or element may be used with the “ball seats” disclosed and discussed herein. For simplicity it is to be understood that the terms “ball” and “plug element” include and encompass all shapes and sizes of plugs, balls, darts, or drop plugs unless the specific shape or design of the “ball” is expressly discussed. 
       SUMMARY OF INVENTION 
       [0006]    Broadly, the apparatuses disclosed herein comprise a housing, a seat, and a plug element wherein one or both of the seat or the plug element comprises at least one shape-memory material. Depending on the embodiment, the seat and/or plug element comprise a first shape and a second shape. Either the first shape or the second shape is the operational shape of the seat and/or plug element and the corresponding other shape is the non-operational shape of the seat and/or plug element. Either the operational shape or the non-operational shape is the “memorized” shape, i.e., the shape toward which the seat and/or plug element is biased due to the shape-memory material out of which the seat and/or plug element is formed. The term “operational shape” is defined herein to mean the shape in which the plug element can be landed on the seat to restrict fluid flow through the conduit or tubular member in which the seat is disposed. 
         [0007]    In one specific embodiment, the plug element is formed of one or more shape-memory materials that provides a plug element that is soft or malleable/pliable such that the plug element can be pushed through one or more restrictions within the tubular member. Thus, in this particular embodiment, the plug element comprises an amorphous non-operational shape that can be changed by an outside stimulus, such as due to pressure acting on the plug element. After passing through one or more restrictions, the plug element can be triggered by another stimulus to change shape to its operational shape, such as into a hardened spherical shape or other desired or necessary shape to engage a seat to restrict fluid flow through the seat. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  is a partial cross-sectional view of a specific embodiment of an apparatus for restricting fluid flow through a conduit showing a seat in its first position with a plug element landed on the seat. 
           [0009]      FIG. 2  is a partial cross-sectional view of the apparatus of  FIG. 1  showing the seat in its second position with the plug element moving through the seat. 
           [0010]      FIG. 3  is a partial cross-sectional view of the apparatus of  FIG. 1  showing the seat returned to its first position after the plug element has moved through the seat. 
           [0011]      FIG. 4  is a partial cross-sectional view of another specific embodiment of an apparatus for restricting fluid flow through a conduit showing a seat in its first position with a plug element in its first position landed on the seat. 
           [0012]      FIG. 5  is a partial cross-sectional view of the apparatus of  FIG. 4  showing the seat in its first position with the plug element in its second position moving through the seat. 
           [0013]      FIG. 6  is a partial cross-sectional view of a tubular member having a restriction and a seat disposed therein, with a plug element being shown in multiple locations as moving down through the restriction, changing shape, and landing on the seat. 
       
    
    
       [0014]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0015]    Referring now to  FIGS. 1-3 , in one particular embodiment, an apparatus for restricting fluid flow is shown as ball seat  30  comprising tubular member  31  and seat member  40 . Tubular member  31  comprises outer wall surface  32  and inner wall surface  33  defining bore  34 . Bore  34  is divided into upper bore  35  and lower bore  36  by seat member  40 . Seat member  40  can be secured to inner wall surface  33  through any method or device know in the art. In one particular embodiment, seat member  40  is secured to inner wall surface  33  by threads (not shown) on inner wall surface  33  and an outer wall surface of seat member  40 . In another embodiment, seat member  40  is secured to inner wall surface  33  by bolts or other fasteners. In still another embodiment, seat member  40  is machined into inner wall surface  33  of tubular member such that tubular member  31  and seat member  40  are one piece, i.e., integral. 
         [0016]    Seat member  40  comprises seat  42  and inner wall surface  43  defining seat member bore  44 . In the embodiment of  FIGS. 1-3 , seat  42  is curved so as to be reciprocal in shape to a plug member shown as a spherical ball  50 . Seat  42  provides a sealing surface for engagement with ball  50 . The term “sealing surface” is defined herein to mean the contact area between seat  42  and ball  50 . 
         [0017]    In the embodiment of  FIGS. 1-3 , seat member  40  is formed out of one or more shape-memory materials. Suitable shape-memory materials include shape-memory polymers and shape-memory alloys. Shape-memory polymers and shape-memory alloys are materials that “remember” their original shapes. Shape-memory polymers and shape-memory alloys can change shape, stiffness, position, natural frequency, and other mechanical characteristics in response to a stimulus such as temperature, electromagnetic fields, chemical solutions, light, and the like. Examples of shape-memory polymers include, but are not limited to, polyurethanes, polyurethanes with ionic or mesogenic components, block copolymers consisting of polyethyleneterephthalate and polyethyleneoxide, block copolymers containing polystyrene and polybutadiene, polyesterurethanes with methylenebis and butanediol, and epoxy resins. Examples of shape-memory alloys include, but are not limited to, nickel-titanium alloys also referred to as Nitinol, copper-aluminum-nickel alloys, copper-zinc-aluminum alloys, and iron-manganese-silicon alloys. 
         [0018]    In operation of the embodiment of  FIGS. 1-3 , ball seat  30  is secured to a work or tubing string (not shown) and lowered into the wellbore (not shown). A downhole tool (not shown) is disposed in the work string above ball seat  30 . Upon reaching the desired location within the wellbore, plug element, shown in this embodiment as ball  50 , is transported down the tubing string until it lands on seat  42  of seat member  40 . Thereafter, fluid, such as hydraulic fluid, is pumped down the tubing string causing downward force or pressure to act on ball  50  to force ball  50  into seat  42 . The fluid pressure above ball  50  is increased until it reaches the actuation pressure of the downhole tool causing the downhole tool to perform its intended function, e.g., open a valve, set a packer, set a bridge plug, and the like. 
         [0019]    After the downhole tool has performed its intended function, additional fluid pressure or other stimulus, such as heat, acidity, electromagnetic pulse(s), light, etc., can be exerted on ball  50  to force ball  50  further into and, ultimately, through seat member  40  as illustrated in  FIGS. 2-3 . During passage of ball  50  through seat member  40 , seat member  40  is deformed such that the diameter of seat member bore  44  is enlarged to permit passage of ball  50  through the bore  44  as illustrated in  FIG. 2 . After passage of ball  50  through seat member  40 , seat member  40  is caused by the shape-memory material to return to its original shape (as shown in  FIG. 3 ) so that another plug element can be transported through the tubing string and landed on seat  42 . Accordingly, ball seat  30  is reusable for actuation of another downhole tool or for performance of any other suitable downhole operation, e.g., acid stimulation. 
         [0020]    Referring now to  FIGS. 4-5 , in another embodiment, an apparatus for restricting fluid flow is shown as ball seat  130  comprising tubular member  131  and seat member  140 . Tubular member  131  comprises outer wall surface  132  and inner wall surface  133  defining bore  134 . Bore  134  is divided into upper bore  135  and lower bore  136  by seat member  140 . Seat member  140  can be secured to inner wall surface  133  through any method or device know in the art such as those discussed above with respect to the embodiments of  FIGS. 1-3 . 
         [0021]    Seat member  140  comprises seat  142  and inner wall surface  143  defining bore seat member bore  144 . In the embodiment of  FIGS. 4-5 , seat  142  is curved so as to be reciprocal in shape to a plug member shown as a spherical ball  150 . Seat  142  provides a sealing surface for engagement with ball  150 . 
         [0022]    In the embodiment of  FIGS. 4-5 , ball  150  is formed out of one or more shape-memory materials such as those identified above with respect to the embodiment of  FIGS. 1-3 . 
         [0023]    In operation of the embodiment of  FIGS. 4-5 , ball seat  130  is secured to a work or tubing string (not shown) and lowered into the wellbore (not shown). A downhole tool (not shown) is disposed in the work string above ball seat  130 . Upon reaching the desired location within the wellbore, plug element, shown in this embodiment as ball  150 , is transported down the tubing string until it lands on seat  142  of seat member  140 . Thereafter, fluid, such as hydraulic fluid, is pumped down the tubing string causing downward force or pressure to act on ball  150  to force ball  150  into seat  142 . The fluid pressure above ball  150  is increased until it reaches the actuation pressure of the downhole tool causing the downhole tool to perform its intended function, e.g., open a valve, set a packer, set a bridge plug, and the like. 
         [0024]    After the downhole tool has performed its intended function, additional fluid pressure or other stimulus, such as heat, acidity, electromagnetic pulse(s), light, etc., can be exerted on ball  150  to force ball  150  further into and ultimately, through seat member  140  as illustrated in  FIG. 5 . During passage of ball  150  through seat member  140 , ball  150  is deformed such that ball  150  can pass through seat member bore  144  as illustrated in  FIG. 2 . After passage of ball  150  through seat member  140 , ball  150  can return to its original shape due to the shape-memory material so that it can be transported further through the tubing string to land on another seat member for actuation of another downhole tool or for performance of any other suitable downhole operation, e.g., acid stimulation. 
         [0025]    Alternatively, the activation of the shape-memory material can transform the shape of ball  150  to the shape shown in  FIG. 5 . In other words, the shape of ball  150  as manufactured using the shape-memory material is the shape shown in  FIG. 5  and the shape toward which ball  150  is biased. Thus, after passing through seat member  140 , ball  150  is maintained in the shape shown in  FIG. 5 . 
         [0026]    Referring now to  FIG. 6 , in another embodiment, an apparatus for restricting fluid flow is shown as ball seat  230  comprising tubular member  231  and seat member  240 . Tubular member  231  comprises outer wall surface  232  and inner wall surface  233  defining bore  234 . Bore  234  is divided into upper bore  235  and lower bore  236  by seat member  240 . Seat member  240  can be secured to inner wall surface  233  through any method or device know in the art such as those discussed above with respect to the embodiments of  FIGS. 1-5 . 
         [0027]    Seat member  240  comprises seat  242  and inner wall surface  243  defining bore seat member bore  244 . In the embodiment of  FIG. 6 , seat  242  is curved so as to be reciprocal in shape to a plug member shown as a spherical ball  250 . Seat  242  provides a sealing surface for engagement with ball  250 . In  FIG. 6 , ball  250  is shown in multiple locations as being transported through tubular member  231  from the top of  FIG. 6  toward the bottom of  FIG. 6 . In other words, it is to be understood that  FIG. 6  shows a single ball  250  in multiple positions as it is transported in the direction of the arrow. 
         [0028]    Disposed with bore  234  above seat member  240  is restriction  248 . Restriction  248  can be any structural component or device that can be found within a tubing string. For example, restriction  248  can be another seat, a bridge plug, a packer, or other downhole tool that has a narrow passageway through which fluid flow is permitted from above to below restriction  248 . 
         [0029]    Ball  250  is formed of a shape-memory material such as those identified above. Initially, ball  250  is transported through bore  234  in its non-operational shape which comprises a plurality of shapes. In other words, ball  250  has an amorphous shape. Due to its amorphous shape, ball  250  is able to pass through restriction  248 . 
         [0030]    As illustrated in  FIG. 6 , ball  250  is initially transported through tubular member  231  in the direction of the arrow while in its operational shape, i.e., a spherical ball shape that is reciprocal to the shape of seat  242 . Upon reaching restriction  248 , however, the movement of ball  250  is restricted. Because ball  250  has an amorphous shape, pressure acting in the direction of the arrow forces ball  250  into passageway  249  disposed through restriction  248 . Upon passing through passageway  249 , ball  250  returns to its operational shape due the shape memory material forming ball  250 . However, ball  250  remains malleable or pliable. 
         [0031]    After passing restriction  248 , ball  250  is contacted with a stimulus, such as an increase in temperature or an increase or decrease in the acidity of the fluid within upper bore  235 . The stimulus causes ball  250  to retain its operational shape so that it can land on seat  242  as shown at the bottom of  FIG. 6 . The stimulus is maintained during downhole operations that require ball  250  to remain on seat  242 . Thereafter, the stimulus can be removed and an increase in pressure will force ball  250  through seat member bore  244  in a manner similar to the manner discussed above with respect to the embodiment of  FIGS. 4-5 . Upon being pushed through seat member bore  244 , seat member  240  is ready to receive another plug element so that an additional downhole operation can be performed. 
         [0032]    In certain other embodiments, the seat member and/or plug element can be formed of a shape-memory material that can be manipulated by outside stimuli such as temperature or acidity. In such embodiments, an operator of the tubing string can manipulate the shape of the seat member and/or plug element depending on the temperature, acidity, or other outside stimuli acting on the seat member and/or plug element. Thus, the size of the opening through a seat member can be customized and/or the plug element can be allowed to pass through one or more restrictions within the tubing string until the operator desires the plug element to achieve its operational shape and land on a seat member. 
         [0033]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, although the apparatuses described in greater detail with respect to  FIGS. 1-6  are ball seats having a ball as their respective plug elements, it is to be understood that the apparatuses disclosed herein may be any type of seat known to persons of ordinary skill in the art that include a radially expandable seat member. For example, the apparatus may be a drop plug seat, wherein the drop plug temporarily restricts the flow of fluid through the wellbore. Therefore, the terms “plug” and “plug element” as used herein encompasses a ball as shown and discussed with respect to the embodiments of the Figures, as well as any other type of device that is used to restrict the flow of fluid through a seat. Further, in all of the embodiments discussed with respect to  FIGS. 1-6 , upward, toward the surface of the well (not shown), is toward the top of  FIGS. 1-6 , and downward or downhole (the direction going away from the surface of the well) is toward the bottom of  FIGS. 1-6 . However, it is to be understood that the seats may have their positions rotated. In addition, the ball seats can be used in any number of orientations easily determinable and adaptable to persons of ordinary skill in the art. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.