Abstract:
A packer for downhole use features interacting elements of swelling material. Preferably the elements are in contact for relative movement from an initial diameter for run in. As the elements swell, they move with respect to each other to enlarge the diameter of the assembly so that a sealing contact is made. Each element exerts a residual force on the adjacent element to enhance the seal. Each element is preferably coated with a material that allows well fluids to reach the swelling material and then later to stiffen and become impervious from exposure to such fluids. The assembly can be covered for run in to delay the onset of expansion until the target depth is reached for the packer to be set.

Description:
PRIORITY INFORMATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/647,816, filed on Jan. 31, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of this invention is packers that seal downhole annular spaces using a swelling action and more particularly where the seal is enhanced by interacting swelling components.  
       BACKGROUND OF THE INVENTION  
       [0003]     Packers have been in use downhole to separate zones in a wellbore. Many styles of such packers have been used. Some mechanically compress a sealing element when the packer mandrel is properly positioned. The compression can be initiated with hydraulic pressure that is applied in the wellbore or the compression force can be initiated by taking advantage of available hydrostatic pressure that is allowed to act on a piston against a lower pressure chamber in the packer body. Some packers are inflatables that are actuated when properly positioned by applied pressure through a valving system leading to an annular space under the inflatable element. In general, these inflatables have a stationary end and a sliding collar at the opposite end of the element that rides up the mandrel as the element is inflated.  
         [0004]     Other packers feature a sleeve of a material that swells that is mounted over a mandrel and covered by a protective material. The rationale is that the sleeve swells in contact with well fluids such as water or hydrocarbons. The outer cover is removable downhole so as to allow a predetermined time to deliver the packer to the desired position before the onset of swelling. Swelling that starts at a premature time could make it impossible to deliver the packer to the desired location or could result in sufficient damage to the sleeve during delivery that the resulting seal will either not occur or will fail under fairly low differential pressures. Some examples of prior art showing a swelling element with a delay feature to the swelling to allow delivery are: US 2004/0055760 A1; US 2004/0194971 A1; US 2004/0118572 A1; U.S. Pat. No. 4,862,967; U.S. Pat. No. 6,854,522; US 2004/0020662 A1; U.S. Pat. No. 3,918,523 and U.S. Pat. No. 4,612,985. Other designs involved putting a swelling material inside an inflatable element and some examples of such a design are: US 2005/0110217 A1; U.S. Pat. No. 6,073,692; U.S. Pat. No. 6,834,725; U.S. Pat. No. 5,048,605; U.S. Pat. No. 5,195,583 and Japan Application 07-334115. Some designs simply use an exposed element that begins to swell upon insertion with the idea that the swelling will progress slowly enough to allow enough time for the delivery to the desired location downhole. Some examples are: U.S. Pat. No. 6,848,505; PCT Application WO 2004/018836 A1; U.S. Pat. No. 4,137,970; US Application US 2004/0261990; Japan Application 03-166,459; U.S. Pat. Nos. 4,919,989 and 4,936,386; US Application US 2005/009363 A1; U.S. Pat. No. 6,854,522 and US Application US 2005/0067170 A1. Yet other design combine the swelling effect with swaging wherein the swelling member is held by a mechanical retainer for delivery and upon reaching the proper depth the expansion breaks the retainer or otherwise defeats it so that swelling can take place. This concept and many others focused on swaging to trigger packer setting are illustrated in U.S. Pat. No. 6,854,522 B2.  
         [0005]     What are needed and not found in the above mentioned prior art are techniques that enhance the seal obtainable from a swelling material using the configuration of the sealing element working in conjunction with the swelling principle employed. Furthermore the invention provides not only an enhanced seal from component interaction but the design of the individual components themselves also promote longevity of the seal by better encapsulating the swelling material and using the encapsulating material for ultimate contact with a surrounding tubular or borehole for an improved seal. These and other advantages of the present invention will be more readily understood by those skilled in the art from the discussion of the preferred embodiment, the drawings and the claims, which determine the scope of the invention.  
       SUMMARY OF THE INVENTION  
       [0006]     A packer for downhole use features interacting elements of swelling material. Preferably the elements are in contact for relative movement from an initial diameter for run in. As the elements swell, they move with respect to each other to enlarge the diameter of the assembly so that a sealing contact is made. Each element exerts a residual force on the adjacent element to enhance the seal. Each element is preferably coated with a material that allows well fluids to reach the swelling material and then later to stiffen and become impervious from exposure to such fluids. The assembly can be covered for run in to delay the onset of expansion until the target depth is reached for the packer to be set. The elements can be pivotally mounted to a mandrel where swelling initiates pivoting and sealing action. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  shows, in section, the overlapping petals of swellable material in the small diameter position for run in;  
         [0008]      FIG. 2  is the view of  FIG. 1  showing the petals swollen to a sealing position;  
         [0009]      FIG. 3  is an alternative embodiment shown in section and in the run in position where curved wings are pivotally mounted to a mandrel and retracted;  
         [0010]      FIG. 4  is the view of  FIG. 3  with the elements rotated out after swelling where the annular space is sealed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]     The packer of the preferred embodiment is shown in  FIG. 1 . It has a mandrel  10  that is surrounded by petals  12 . In the preferred embodiment the petals  12  are crescent-shaped or arcuate in their contact surfaces to promote relative movement of one with respect to an adjacent petal as they swell. Preferably each petal has an end  13  that rests on the mandrel  10  with an opposite end  15  that overlays the end  13 ′ of an adjacent petal  12 . There is an initial gap  31  that closes as the elements  12  swell. The illustrated arrangement works similarly to an iris when swelling is initiated. Optionally the petals  12  can be retained as they swell with a band that grows with them (not shown) because of its elastic qualities or one that stretches and snaps at a given point of swelling. In that way the petals retain their relative positions better as they swell. The length can vary to suit the desired application. The cross-sectional shape can also vary and the contact surfaces during swelling do not need to be arcuate but could also be straight. Regardless of the cross-sectional shape, the interaction of the petals  12  upon swelling is to interact with each other so that the sealing force they ultimately provide is not simply defined solely by expansion that occurs during swelling. Rather, it is a combination of the dimension change from swelling as enhanced by the overlapping layout of the petals  12  that boosts the sealing force beyond that simply provided from mere swelling of a plurality of petals. A shape change for at least one of the petals  12  is contemplated as seen by comparing  FIGS. 1 and 2 . However, in the ultimate shape created, the adjacent petals  12  interact with each other when sealing is complete to enhance the force against the surrounding tubular or wellbore (not shown).  
         [0012]     The petals  12  can preferably have an individual covering  14  that is preferably a resin coated initially porous bag. The bag initially lets well fluid though to the petal  12  to initiate its swelling process. The well fluids can be hydrocarbons, water or combinations thereof or other materials already in the wellbore or subsequently added to the wellbore after the mandrel  10  is placed in the desired location. Exposure to the particular fluid that made the petal  12  swell will eventually cure a resin material  16  that coats the bag  14 . Alternatively, resin material  16  can be within the petal  12  and can set up as a given petal swells to increase the integrity of the ultimate seal. Alternatively the petal  12  can simply be coated with a resin or other material  16  that initially allows fluid to pass and with time and exposure to a fluid downhole cures or sets up or otherwise gets firm. In this manner there is no bag  14 . The petals  12  can be made from an expandable material; examples of which are, a super absorbing polymer (SAP), gas producing water reactive materials, epoxy foams, etc. Possible hardenable materials include: Portland cement, water-hardenable urethane, alkyd, diisocyanate, etc. This material winds up being encased in bags  14  that desirably become impervious and more rigid so that they can seal against the borehole or surrounding tubular more effectively. The petals can be made of a variety of materials known to swell and the material selection can be tailored to the fluids expected in the well or those on hand to be introduced later. While multiple petals are contemplated, the invention further comprises other no-petal arrangements of a material that swells and hardens to form a downhole seal.  
         [0013]     The petals can also be mechanically reinforced to increase the pressure holding capacity, as illustrated in  FIGS. 3 and 4 . This can be done in many ways. Examples include: metal ribs hinged to the well pipe that are folded close to the pipe during run in then pivot out radially between the pipe and wellbore to strengthen the plug, fiber strands mixed with the expandable material, reinforcing cloth attached to the pipe that is folded close to the pipe during run in then unfolds when the expanding material grows to a position to strengthen the plug. Many other configurations are possible. Specifically, in  FIG. 3  wings  34  that can be metal or another rigid material are connected at a pivot  36  mounted to the base pipe or mandrel  38 . Each wing  34  supports an element  40  that can be attached to the wing  34  in a variety of ways. The wing can be enveloped by the element  40  or the element can be mounted on one side or the other of a particular wing  34 . The element can be in the form of an expandable bag that surrounds a swelling material. In some instances the surrounding bag can initially allow well fluids or fluids added to the well to flow through it to initiate swelling within and thereafter harden to become more rigid and, possibly, impermeable. To allow time for run in before any swelling starts, an outer cover  42  can be applied over the elements  40  as a group or individually on one or more elements  40 . This cover  42  protects the elements  40  during run in and also delays the advance of well fluid into the swellable material. Here again, the elements  40  when they swell, as shown in  FIG. 4 , take the shape of the annulus  44  and cause a pivoting motion about pivots  36  so that swelling elements  46  interact with each other to enhance the sealing force in the annular space  44 . The presence of the wings simply increases the interaction effect of adjacent swelling elements  40 . The bags or enclosures for the swelling material on the wings  34  can have reinforcing material such as fiberglass, Kevlar® or carbon fiber. The reinforcement allows better resistance to applied differential pressures after swelling has occurred and the annular space  44  is sealed. The swelling filler material can be water activated urethane or super absorbing polymer, for example. These materials swell when exposed to drilling fluids, for example. The outer cover  42  can be designed to slowly disappear in drilling fluid over a fairly long period of time with times as long as several days possible. Some possible materials for the cover  42  that can cover over all the elements  40  or some of them are PVA, EVOH or WSPET. Alternatively, the outer cover  42  can cover the elements  40  for run in but be porous to allow well fluids to reach the elements and have elastic capabilities to allow the swelling and then turn rigid from the well fluid exposure. Thus instead of or in addition to covering each element  40  individually with a cover that first passed fluid and then hardens, the assembly of all the petals or even groups of them can be similarly covered.  
         [0014]     In operation the cover disappears after the assembly has been placed at the desired location. The wings  34  can make contact with the wellbore for sealing as acted upon by the elements  40 . Depending on the configuration the elements  40  can make the seal on the wellbore wall reinforced by the wings  34  attached to them. Alternatively, a combination of contacting wings  34  or elements  40  doing the sealing is envisioned. The swellable material that is surrounded by a bag and defines an element  40  can also permeate the surrounding bag to help make it impervious by filling voids therein. The surrounding bag material can also harden and become more rigid to strengthen the overall performance of the assembly. A water activated urethane material on the bag can help the element  40  become harder to add sealing strength to the assembly.  
         [0015]     Additionally, and optionally, an outer sheath  18  can be placed all around the coated bags  14  or individually around each or some of the bags  14 . Doing this delays the access of the triggering fluid to the expandable material that preferably comprises the petals  12  until the assembly is properly located in the well. The sheath can be made of a material that dissolves over time in the well fluids or in other ways fails or goes away over time or with an applied force, such as expansion from within the mandrel with a swage, for example. Alternatively, there can be an outermost layer that delays the swelling action of the petals  12  that goes away by a variety of mechanisms, as stated above and just inside of it can be a porous flexible housing  20  that simply retains the petals  12  in an adjacent relationship as they swell. In this arrangement shown in  FIG. 2  it is the housing  20  that will contact the wellbore or surrounding tubular (not shown) urged outwardly by the force from the expanding petals  12 . The housing  20  can become impervious and/or get harder with exposure to well fluids. The arrangement of the petals  12  will enhance the sealing force as they swell and move relatively to each other to increase the contact force for sealing above and beyond the use of a simple cylindrical sleeve. The use of an initially porous material  16  to cover the petals  12  further improves the sealing capability of the assembly in that it maintains the structural integrity of the petals  12  that happen to be covered with the material  16 .  
         [0016]     The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.