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BACKGROUND 
       [0001]    1. Field of Invention 
         [0002]    The present invention is directed to expandable leak path preventers for use in downhole tools, and in particular, to expandable seal inserts disposed in downhole tools that expand upon exposure to certain fluids to provide leak path seals in the downhole tools. 
         [0003]    2. Description of Art 
         [0004]    Hydraulic set tools such as packers and liner hangers use dynamic seals on the setting pistons. These dynamic seals are often “life of the well” seals meaning that the seals must not fail, i.e., they must hold differential pressure, during the entire life of the well. Alternatively, the dynamic seals, although not “life of the well” seals, are seals that at some point in their useful life will be subjected to differential pressures after the downhole tool is actuated or set. For example, after a packer is set, a plug may be placed in the tailpipe of the packer for an upper end workover. In such a case, the dynamic seals in the packer will be subjected to differential pressures that may cause the dynamic seals to fail. 
         [0005]    In the event that the dynamic seals fail, the failed downhole tool must be removed and a new replacement or repaired downhole tool must be run-in and set in place of the failed downhole tool. 
       SUMMARY OF INVENTION 
       [0006]    Broadly, fluid activated downhole tools such as packers and liner hangers include at least one expandable seal member or insert, formed from an expandable material, disposed within the actuating chamber of the downhole tool. The actuating chamber includes the actuator, e.g., the setting piston. In one embodiment, the actuating chamber is in fluid communication with the bore of the downhole tool through a port. As fluid, e.g., hydraulic fluid, is pumped down through the downhole tool to set the downhole tool, it travels through the port and into the actuating chamber to move the actuator and set the downhole tool. In another embodiment, the port provides fluid communication between the actuating chamber and the wellbore environment. In this embodiment, as fluid, e.g., wellbore fluid, is permitted access through port, such as through a rupture disk that breaks when the downhole tool reaches a location having a certain pressure, to move the actuator within the actuating chamber to the set position. 
         [0007]    In one embodiment, two expandable seal inserts are placed in the actuating chamber above and below the point where the port communicates with the actuating chamber. As the actuator is actuated by the fluid, the expandable seal inserts begin to expand due to their contact with the fluid. After the actuator sets the downhole tool, the expandable seal inserts continue to expand until a seal is formed over the port and the actuator. Thus, the expandable material inserts provide a secondary seal to the actuator&#39;s normal dynamic seals and a primary seal across the port. In certain downhole tools, the expandable seal inserts may also provide a secondary seal to one or more dynamic seals disposed opposite the actuator that are part of the assembled downhole tool. 
         [0008]    In one embodiment, a fluid actuated downhole tool for an oil or gas well is disclosed. The downhole tool has a run-in position and a set position and comprises a housing with a longitudinal bore therethrough; an actuating chamber, the actuating chamber having an actuator operatively associated therein for moving the downhole tool from the run-in position to the set position; and an expandable seal insert disposed within the actuating chamber, adjacent a leak path, the expandable seal insert being formed from an expandable material, wherein the expandable seal insert expands and seals the leak path when contacted with a fluid for actuating the downhole tool, the fluid causing the actuator to move the downhole tool from the run-in position to the set position. 
         [0009]    A further feature of the downhole tool is that the downhole tool may further comprise a port in fluid communication with the actuating chamber, wherein the expandable seal insert is disposed adjacent the port thereby causing the port to become sealed by the expandable seal insert when the downhole tool is in the set position. Another feature of the downhole tool is that the port may be in fluid communication with bore. An additional feature of the downhole tool is that the actuator may include outer and inner wall surfaces in sliding engagement with respective outer and inner wall surfaces of the actuating chamber, the leak path including the sliding engagement between outer and inner wall surfaces of the actuator with the respective outer and inner wall surface of the actuating chamber, and the expandable seal insert being disposed adjacent the actuator thereby allowing the sliding engagement between outer and inner wall surfaces of the actuator with the respective outer and inner wall surface of the actuating chamber to become sealed by the expandable seal insert when the downhole tool is in the set position. Still another feature of the downhole tool is that the leak path may include at least one internal dynamic seal, and wherein the expandable seal insert is disposed adjacent at least one of the at least one internal dynamic seals thereby allowing the at least one of the at least one internal dynamic seals to become sealed by the expandable seal insert when the downhole tool is in the set position. A further feature of the downhole tool is that the actuator may comprise a piston in sliding engagement with the actuating chamber, the piston comprising at least one dynamic seal and the expandable seal insert being connected to the piston. Another feature of the downhole tool is that the downhole tool may include at least two expandable seal inserts, one of the at least two expandable seal inserts being disposed adjacent a port in fluid communication with the actuating chamber and another of the at least two expandable seal inserts being disposed adjacent the actuator. An additional feature of the downhole tool is that the actuator may comprise a piston in sliding engagement with the actuating chamber, the piston comprising at least one dynamic seal and the expandable seal insert being connected to the piston. Still another feature of the downhole tool is that the expandable material comprises a swellable polymer. A further feature of the downhole tool is that the expandable seal insert may comprise an encapsulating dissolvable material encapsulating the expandable material prior to setting the downhole tool. Another feature of the downhole tool is that the encapsulating material may comprise a bio-degradable polymer. An additional feature of the downhole tool is that the biodegradable polymer may comprise a polyvinyl-alcohol based polymer. Still another feature of the downhole tool is that the downhole tool may be a packer. 
         [0010]    In another embodiment, an improved downhole tool has a run-in position and a set position and is actuatable by a fluid. The improvement comprises at least one expandable seal insert disposed along at least one leak path, each of the at least one expandable seal inserts being capable of expanding and sealing at least one of the at least one leak paths. 
         [0011]    A further feature of the improved downhole tool is that at least one of the at least one expandable seal inserts may be disposed within an actuating chamber of the downhole tool. Another feature of the improved downhole tool is that at least one of the at least one expandable seal inserts may be connected to an actuator. An additional feature of the improved downhole tool is that at least one of the at least one expandable seal inserts may be disposed within an actuating chamber of the downhole tool adjacent a port in fluid communication with the actuating chamber. Still another feature of the improved downhole tool is that at least one of the at least one expandable seal inserts comprises a sleeve disposed within an actuating chamber of the downhole tool. 
         [0012]    In an additional embodiment, a method of preventing formation of a leak path in an actuated downhole tool in its set position is disclosed. The method comprises the steps of: (a) actuating a downhole tool with a fluid, wherein during actuation, the downhole tool is moved from a run-in position to a set position; (b) contacting an expandable seal insert comprising an expandable material with the fluid causing the expandable seal insert to expand; and (c) sealing a leak path in the downhole tool due to the expansion of the expandable seal insert, thereby by preventing fluid leakage through the leak path with the expanded expandable seal insert. 
         [0013]    A further feature of the method is that the expandable seal insert may be expanded by dissolving a dissolvable material initially disposed between the expandable seal insert and the fluid. Another feature of the method is that step (b) may be performed during actuation of the downhole tool from the run-in position to the set position. An additional feature of the method is that step (b) may be performed after actuation of the downhole tool from the run-in position to the set position. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a partial cross-sectional view of a packer shown in the run-in or unset position. 
           [0015]      FIG. 2  is a partial cross-sectional view of the bottom portion of the packer shown in  FIG. 1   
           [0016]      FIG. 3  is a partial cross-sectional view of the bottom portion of the packer referred to in  FIG. 1  shown in the set position. 
       
    
    
       [0017]    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 
       [0018]    Referring now to  FIGS. 1-3 , downhole tool  40  is a packer. Downhole tool  40  comprises a longitudinal bore  44 , a setting port  46  in fluid communication with bore  44 , actuating chamber  48 , and actuator  50 . Actuator  50  is shown in this embodiment as a piston having dynamic seals  51 ,  52 . 
         [0019]    Referring now to  FIGS. 2-3 , actuating chamber  48  includes two expandable seal inserts  60 ,  62 , one disposed below port  46  (expandable seal insert  62 ) and one disposed above port  46  (expandable seal insert  60 ). In the embodiment shown in  FIGS. 1-3 , expandable seal insert  60  is affixed or connected to actuator  50  such that as actuator  50  moves from the run-in position ( FIG. 2 ) to the set position ( FIG. 3 ), expandable seal insert  60  moves with actuator  50 . As shown in  FIGS. 2-3 , expandable seal inserts  60 ,  62  are sleeves disposed within actuating chamber  48 . It is to be understood, however, the expandable seal inserts  60 ,  62  may have any shape desired or necessary to seal one or more leak path after setting of the downhole tool. 
         [0020]    Each expandable seal insert  60 ,  62  comprises, at least in part, an expandable material that is capable of expanding and sealing against the walls of actuating chamber  48  of downhole tool  40 . In one specific embodiment, expandable seal inserts  60 ,  62  are formed completely out of the expandable material. In other embodiments, expandable seal inserts  60 ,  62  include non-expandable components such as stiffing rings or other support structures or substrates to which the expandable material is connected. 
         [0021]    Suitable expandable materials include urethane and polyurethane materials, including polyurethane foams, biopolymers, and superabsorbent polymers. In one embodiment, the expandable materials swell by absorbing fluids such as water or hydrocarbons. Nitriles and polymers sold as 1064 EPDM from Rubber Engineering in Salt Lake City, Utah are acceptable expandable materials. In one embodiment, the expandable material comprises a swellable polymer such as cross-linked or partially cross-linked polyacrylamide, polyurethane, ethylene propylene, or other material capable of absorbing hydrocarbon or aqueous, or other fluids, and, thus, swelling to provide the desired seals. In another embodiment, the expandable material is a shape-memory material, for example, a metal shape-memory material or a compressed elastomer or polymer that is held in the compressed state by a dissolvable material such as those discussed below. 
         [0022]    In one embodiment, the expandable materials or the expandable seal inserts  60 ,  62  themselves may be encapsulated with a layer of material dissolvable by fluids such as water or hydraulic fluid. As used herein, the term “encapsulated” and “encapsulating” means that the dissolvable material forms an initial barrier between the fluid and the expandable materials or the expandable seal inserts  60 ,  62 . In such embodiments, the encapsulated layer allows the use of expandable materials, and expandable seal inserts  60 ,  62  formed from expandable materials, that expand virtually instantaneously upon contacting the fluid by protecting the expandable materials until expansion is desired. 
         [0023]    Encapsulating dissolvable materials for encapsulating the expandable materials may be any material known to persons of ordinary skill in the art that can be dissolved, degraded, or disintegrated over an amount of time by a temperature or fluid such as water-based drilling fluids, hydrocarbon-based drilling fluids, or natural gas. Preferably, the encapsulating dissolvable material is calibrated such that the amount of time necessary for the dissolvable material to dissolve is known or easily determinable without undue experimentation. Suitable encapsulating dissolvable materials include polymers and biodegradable polymers, for example, polyvinyl-alcohol based polymers such as the polymer HYDROCENE™ available from Idroplax, S.r.l. located in Altopascia, Italy, polylactide (“PLA”) polymer 4060D from Nature-Works™, a division of Cargill Dow LLC; TLF-6267 polyglycolic acid (“PGA”) from DuPont Specialty Chemicals; polycaprolactams and mixtures of PLA and PGA; solid acids, such as sulfamic acid, trichloroacetic acid, and citric acid, held together with a wax or other suitable binder material; polyethylene homopolymers and paraffin waxes; polyalkylene oxides, such as polyethylene oxides, and polyalkylene glycols, such as polyethylene glycols. These polymers may be preferred in water-based drilling fluids because they are slowly soluble in water. 
         [0024]    In one specific embodiment having an encapsulating dissolvable material, the expandable material is one or more chemical components that undergo a chemical reaction when expandable seal inserts  60 ,  62  are contacted with the fluid being pumped through bore  44  and port  46  of the downhole tool. For example, the expandable material may be a combination of solid particles of magnesium oxide and monopotassium phosphate encapsulated by one or more of the above-referenced encapsulating dissolvable materials. After the dissolution of the encapsulating dissolvable material, the chemical components of the expandable material react in the presence of the fluid, e.g., water or hydraulic fluid, causing the chemical components to form a gel phase and, ultimately, a crystallized solid ceramic material magnesium potassium phosphate hexahydrate which is a chemically bonded ceramic. In such embodiments, the encapsulating dissolvable material may also be used to separate one or more chemical component from one or more another chemical component to prevent premature reaction and expansion. 
         [0025]    In selecting the appropriate expandable material and, if necessary or desired the encapsulating material, for expandable seal inserts  60 ,  62 , the amount of time necessary for actuator  50  to more from the run-in position ( FIG. 2 ) to the set position ( FIG. 3 ) should be taken into consideration. If the expandable seal inserts  60 ,  62  expand prematurely, downhole tool  40  may not be completely set. 
         [0026]    As shown in  FIGS. 2-3 , packer  40  includes dynamic seals  51 ,  52  and static seal  53 , all of which are potential leak paths after downhole tool  40  is moved to the set position ( FIG. 3 ). Expandable seal inserts  60 ,  62  are disposed adjacent these dynamic seals and, in the embodiment shown in  FIGS. 2-3 , adjacent port  46 . It is to be understood, however, that expandable seal inserts  60 ,  62  may be disposed such that port  46 , or one or more dynamic seals  51 ,  52  or static seal  53 , do not have an expandable seal insert disposed adjacently thereto. Moreover, one or more expandable seal inserts may be disposed in downhole tool  40 , or other downhole tools at locations other than within actuating chamber  48 . In other words, despite expandable seal inserts  60 ,  62  being shown disposed within actuating chamber  48 , it is to be understood that expandable seal inserts  60 ,  62  may be disposed at any location within a downhole tool where leak paths are known to occur. 
         [0027]    In operation, downhole tool  40  is disposed within a wellbore at the desired location. Hydraulic fluid (not shown) is pumped down bore  44 , through port  46 , and into actuating chamber  48 . As the pressure from the hydraulic fluid increases, actuator  50  is forced upwards causing downhole tool  40  to move from its run-in position ( FIG. 2 ) to its set position ( FIG. 3 ). In so doing, expandable seal insert  60  moves upward with actuator  50 . The hydraulic fluid not only forces actuator  50  from its run-in position to its set position, the hydraulic fluid also causes expandable seal inserts  60 ,  62  to expand. As expandable seal inserts  60 ,  62  expand, port  46  is blocked by expandable seal insert  62 . Leak paths located at dynamic seals  51 ,  52  and static seal  53  are likewise blocked by expandable seals  60  and  62 , respectively. As a result, expandable seal insert  62  provides a primary seal over port  46  and a secondary seal over static seal  53 , and expandable seal insert  60  provides secondary seals over dynamic seals  51 ,  52 . 
         [0028]    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, downhole tool  40  may be a liner hanger, or any other downhole tool or component that has a run-in position and set position, wherein the downhole tool is moved from the run-in position to the set position using a fluid such as hydraulic fluid or other wellbore fluid. Additionally, one or more expandable seal inserts may be disposed in numerous locations throughout the downhole tool to provide primary, secondary, tertiary, etc. seals when the expandable seal inserts contact a fluid either during or after setting the downhole tool. Further, the expandable seal inserts may be customized based upon the size needed to provide the appropriate seal. Moreover, the expandable seal inserts may customized based upon the amount of time necessary to set the downhole tool prior to the expanding seal inserts providing the appropriate seal. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

Summary:
Expandable seal members or inserts are included as part of fluid activated downhole tools such as packers and liner hangers. The expandable seal inserts comprise one or more expandable materials that expand and seal against the chamber carrying the actuator of the downhole tool. Fluid flowing in the downhole tool to actuate and, thus, set the downhole tool, also causes the expandable seal inserts to expand. In so doing, the expandable seal inserts provide seals, some redundant to dynamic seals and static seals already present in the downhole tool, to assist in preventing leaks in the downhole tool that may otherwise cause the downhole tool to fail.