Abstract:
A packer assembly features one or more elements that preferably swell when in contact with well fluids and have a feature in them that responds to an applied load in a given direction by retaining such a boost force with a locking mechanism. A single element can have two such mechanisms that respond to applied forces from opposed directions. Friction force for adhering the element to the mandrel is enhanced with surface treatments between them that still allow the locking mechanisms to operate.

Description:
FIELD OF THE INVENTION  
       [0001]     The field of this invention is generally plugs and packers for downhole use and more particularly packers that have a sealing element that swells and retains boost forces when subjected to pressure differentials.  
       BACKGROUND OF THE INVENTION  
       [0002]     Packers and plugs are used downhole to isolate zones and to seal off part of or entire wells. There are many styles of packers on the market. Some are inflatable and others are mechanically set with a setting tool that creates relative movement to compress a sealing element into contact with a surrounding tubular. Generally, the length of such elements is reduced as the diameter is increased. Pressure is continued from the setting tool so as to build in a pressure into the sealing element when it is in contact with the surrounding tubular.  
         [0003]     More recently, packers have been used that employ elements that respond to the surrounding well fluids and swell to form a seal. Many different materials have been disclosed as capable of having this feature and some designs have gone further to prevent swelling until the packer is close to the position where it will be set. These designs were still limited to the amount of swelling from the sealing element as far as the developed contact pressure against the surrounding tubular or wellbore. The amount of contact pressure is a factor in the ability to control the level of differential pressure. In some designs there were also issues of extrusion of the sealing element in a longitudinal direction as it swelled radially but no solutions were offered. A fairly comprehensive summation of the swelling packer art appears below:  
         [0000]     I. References Showing a Removable Cover Over a Swelling Sleeve  
         [0004]     1) Application US 2004/0055760 A1  
         [0005]      FIG. 2   a  shows a wrapping  110  over a swelling material  102 . Paragraph  20  reveals the material  110  can be removed mechanically by cutting or chemically by dissolving or by using heat, time or stress or other ways known in the art. Barrier  110  is described in paragraph  21  as an isolation material until activation of the underlying material is desired. Mechanical expansion of the underlying pipe is also contemplated in a variety of techniques described in paragraph  24 .  
         [0006]     2) Application US 2004/0194971 A1  
         [0007]     This reference discusses in paragraph  49  the use of water or alkali soluble polymeric covering so that the actuating agent can contact the elastomeric material lying below for the purpose of delaying swelling. One way to accomplish the delay is to require injection into the well of the material that will remove the covering. The delay in swelling gives time to position the tubular where needed before it is expanded. Multiple bands of swelling material are illustrated with the uppermost and lowermost acting as extrusion barriers.  
         [0008]     3) Application US 2004/0118572 A1  
         [0009]     In paragraph  37  of this reference it states that the protective layer  145  avoids premature swelling before the downhole destination is reached. The cover does not swell substantially when contacted by the activating agent but it is strong enough to resist tears or damage on delivery to the downhole location. When the downhole location is reached, pipe expansion breaks the covering  145  to expose swelling elastomers  140  to the activating agent. The protective layer can be Mylar or plastic.  
         [0010]     4) U.S. Pat. No. 4,862,967  
         [0011]     Here the packing element is an elastomer that is wrapped with an imperforate cover. The coating retards swelling until the packing element is actuated at which point the cover is “disrupted” and swelling of the underlying seal can begin in earnest, as reported in Column  7 .  
         [0012]     5) U.S. Pat. No. 6,845,322  
         [0013]     This patent has many embodiments. The one in  FIG. 26  is foam that is retained for run in and when the proper depth is reached expansion of the tubular breaks the retainer  272  to allow the foam to swell to its original dimension.  
         [0014]     6) Application US 2004/0020662 A1  
         [0015]     A permeable outer layer  10  covers the swelling layer  12  and has a higher resistance to swelling than the core swelling layer  12 . Specific material choices are given in paragraphs  17  and  19 . What happens to the cover  10  during swelling is not made clear but it presumably tears and fragments of it remain in the vicinity of the swelling seal.  
         [0016]     7) U.S. Pat. No. 3,918,523  
         [0017]     The swelling element is covered in treated burlap to delay swelling until the desired wellbore location is reached. The coating then dissolves of the burlap allowing fluid to go through the burlap to get to the swelling element  24  which expands and bursts the cover  20 , as reported in the top of Column  8 .  
         [0018]     8) U.S. Pat. No. 4,612,985  
         [0019]     A seal stack to be inserted in a seal bore of a downhole tool is covered by a sleeve shearably mounted to a mandrel. The sleeve is stopped ahead of the seal bore as the seal first become unconstrained just as they are advanced into the seal bore.  
         [0000]     II. References Showing a Swelling Material under an Impervious Sleeve  
         [0020]     1) Application US 2005/0110217  
         [0021]     An inflatable packer is filled with material that swells when a swelling agent is introduced to it.  
         [0022]     2) U.S. Pat. No. 6,073,692  
         [0023]     A packer has a fluted mandrel and is covered by a sealing element. Hardening ingredients are kept apart from each other for run in. Thereafter, the mandrel is expanded to a circular cross section and the ingredients below the outer sleeve mix and harden. Swelling does not necessarily result.  
         [0024]     3) U.S. Pat. No. 6,834,725  
         [0025]      FIG. 3   b  shows a swelling component  230  under a sealing element  220  so that upon tubular expansion with swage  175  the plugs  210  are knocked off allowing activating fluid to reach the swelling material  230  under the cover of the sealing material  220 .  
         [0026]     4) U.S. Pat. No. 5,048,605  
         [0027]     A water expandable material is wrapped in overlapping Kevlar sheets. Expansion from below partially unravels the Kevlar until it contacts the borehole wall.  
         [0028]     5) U.S. Pat. No. 5,195,583  
         [0029]     Clay is covered in rubber and a passage leading from the annular space allows well fluid behind the rubber to let the clay swell under the rubber.  
         [0030]     6) Japan Application 07-334115  
         [0031]     Water is stored adjacent a swelling material and is allowed to intermingle with the swelling material under a sheath  16 .  
         [0000]     III. References Which Show an Exposed Sealing Element that Swells on Insertion  
         [0032]     1) U.S. Pat. No. 6,848,505  
         [0033]     An exposed rubber sleeve swells when introduced downhole. The tubing or casing can also be expanded with a swage.  
         [0034]     2) PCT Application WO 2004/018836 A1  
         [0035]     A porous sleeve over a perforated pipe swells when introduced to well fluids. The base pipe is expanded downhole.  
         [0036]     3) U.S. Pat. No. 4,137,970  
         [0037]     A swelling material  16  around a pipe is introduced into the wellbore and swells to seal the wellbore.  
         [0038]     4) US Application US 2004/0261990  
         [0039]     Alternating exposed rings that respond to water or well fluids are provided for zone isolation regardless of whether the well is on production or is producing water.  
         [0040]     5) Japan Application 03-166,459  
         [0041]     A sandwich of slower swelling rings surrounds a faster swelling ring. The slower swelling ring swells in hours while the surrounding faster swelling rings do so in minutes.  
         [0042]     6) Japan Application 10-235,996  
         [0043]     Sequential swelling from rings below to rings above trapping water in between appears to be what happens from a hard to read literal English translation from Japanese.  
         [0044]     7) U.S. Pat. No. 4,919,989 and 4,936,386  
         [0045]     Bentonite clay rings are dropped downhole and swell to seal the annular space, in these two related patents.  
         [0046]     8) US Application US 2005/009363 A1  
         [0047]     Base pipe openings are plugged with a material that disintegrates under exposure to well fluids and temperatures and produces a product that removes filter cake from the screen.  
         [0048]     9) U.S. Pat. No. 6,854,522  
         [0049]      FIG. 10  of this patent has two materials that are allowed to mix because of tubular expansion between sealing elements that contain the combined chemicals until they set up.  
         [0050]     10) US Application US 2005/0067170 A1  
         [0051]     Shape memory foam is configured small for a run in dimension and then run in and allowed to assume its former shape using a temperature stimulus.  
         [0000]     IV. Reference that Shows Power Assist Actuated Downhole to Set a Seal  
         [0052]     1) U.S. Pat. No. 6,854,522  
         [0053]     This patent employs downhole tubular expansion to release potential energy that sets a sleeve or inflates a bladder. It also combines setting a seal in part with tubular expansion and in part by rotation or by bringing slidably mounted elements toward each other.  FIGS. 3, 4 ,  17 - 19 ,  21 - 25 ,  27  and  36 - 37  are illustrative of these general concepts.  
         [0054]     The various concepts in U.S. Pat. No. 6,854,522 depend on tubular expansion to release a stored force which then sets a material to swelling. As noted in the  FIG. 10  embodiment there are end seals that are driven into sealing mode by tubular expansion and keep the swelling material between them as a seal is formed triggered by the initial expansion of the tubular.  
         [0055]     What has been lacking is a technique for automatically capturing applied differential pressures to a set element, particularly when set by swelling in reaction to exposure to well fluids, and retaining that force in the element to retain or/and boost its sealing capabilities downhole. The present invention offers various embodiments that capture boost forces from differential loading in the uphole or downhole directions and various embodiments to accomplish such capture in a single element or multiple elements on a single or multiple mandrels. Those skilled in the art will more readily appreciate the scope of the invention from a review of the description of the preferred and alternative embodiments, the drawing and the claims that appear below and define the full scope of the invention.  
       SUMMARY OF THE INVENTION  
       [0056]     A packer assembly features one or more elements that preferably swell when in contact with well fluids and have a feature in them that responds to an applied load in a given direction by retaining such a boost force with a locking mechanism. A single element can have two such mechanisms that respond to applied forces from opposed directions. Friction force for adhering the element to the mandrel is enhanced with surface treatments between them that still allow the locking mechanisms to operate. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0057]      FIG. 1  is a section view showing a sealing element that is fixed on one end and has the locking feature for capturing a boost force in one direction at the opposite end and shown in the run in position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0058]      FIG. 1  will be used to illustrate a variety of variations of the present invention. What is illustrated in the Figure is a mandrel  10  for a packer P. Mounted to the mandrel  10  is an element  12  that preferably is of the type that swells in contact with well fluids using materials described in the patents and applications discussed above. A covering (not shown) can also be applied to the element  12  to provide a time delay to allow the packer P to be positioned close to where it needs to be set. The materials that accomplish this delay using a cover that goes away after a time exposure to well fluids and predetermined temperatures are also discussed in the patents and applications above.  
         [0059]     In the Figure, the element assembly  12  has an uphole end  14  and a downhole end  16 . In one variation that is shown, the uphole end  14  is abutting a block  18  and is further secured to it and between itself and mandrel  10  with an adhesive or some type of bonding material  20  compatible with well materials and temperatures. Block  18  can be a ring welded to the mandrel  10  or can be attached with adhesive or threads or can be integral to the mandrel. While the element  12  can swell radially along its length, differential loading from the uphole end  14  toward the downhole end  16  will not budge the element away from block  18  due to the presence of bonding material  20 . In the embodiment of the Figure, any net downhole force from such loading will not add an additional sealing force into the element  12  because the upper end of the embodiment in the Figure is bonded and stationary, unlike the opposite end that has a ratchet feature, as will be described below. However, if there is differential loading after the element  12  swells to a sealing position the result will be that pressure applied in that direction will cause the downhole end  16  to ride toward uphole end  14  thus shortening the length of the element  12  while increasing its internal pressure. This increase in internal pressure will enhance the sealing force of the element to allow it to withstand even greater differentials going from the downhole end  16  to the uphole end  14 . To lock in that boost force that comes from loading due to increasing pressure conditions near the downhole end  16 , it is desirable to lock in such boost forces when they occur. To accomplish this, the mandrel  10  has a series of serrations or other rough surface treatment  22  adjacent downhole end  16 . The element  12  has an undercut  24  where ring  26  is secured with an adhesive or other bonding material  28  adjacent a ring  30  with an interior serrated surface  32 . Surfaces  22  and  32  ride over each other in one direction like a ratchet but lock upon relative movement in an opposed direction. Ring  30  is also bonded to element  12  with adhesive such as  28 . Rings  26  and  30  can be separate or unitary. In this version, the central section  34  is not bonded to mandrel  10 . This allows the length of the element  12  to decrease in response to a net force when the element  12  is set and compressed from an uphole directed force. Such a force results in ratcheting between surfaces  22  and  32  to lock in a greater force into the swelled element  12  against a surrounding tubular or an open hole (neither of which are shown).  
         [0060]     Those skilled in the art will appreciate that the design shown in  FIG. 1  can be inverted so that net forces in the downhole direction or toward the right in  FIG. 1  will result in locking in a greater sealing force in the element  12 .  
         [0061]     Another variation is to use two packers P mounted adjacent each other with opposed orientations for the locking device so that net forces in an uphole or downhole direction will each result in capturing a greater sealing force in the element  12 . Alternatively, a single mandrel  10  can house two elements of the type shown in  FIG. 1  except that they are in mirror image orientation to allow capturing additional sealing force in the element  12  regardless of the direction of the net applied force. In yet another alternative, the assembly shown in undercut  24  can be disposed on opposed ends of the same element with a binder such as  20  being disposed only in the middle portion  34 . In that manner, a net force in either direction will cause a ratcheting action that retains a greater sealing force in the element  12 .  
         [0062]     While a ratchet based system for locking in additional sealing force has been illustrated other mechanisms that permit unidirectional compression of the element from applied differential pressure loads on a set element  12  downhole are well within the scope of the invention.  
         [0063]     Referring again to  FIG. 1  an additional feature can be added to deal with the issue of relative movement during delivery to the packer P to the desired location for setting. Portions of the mandrel  10  can receive a roughening surface treatment in the form of grooves or adhered particles that will enhance the grip on element  12 . Of course, the location of such treatment of the mandrel  10  need to be placed in locations where longitudinal compression of the element  12  from pressure loading will not be impaired. For example, in the embodiment literally shown in  FIG. 1  the block  18  will adequately resist shifting of the element  12  during run in. The middle section  34  will need to permit sliding to allow the ratcheting movement between teeth  22  and  32 . To prevent premature ratcheting during run in, a ring  36  can retain end  16  during run in and can be made of a material that dissolves or goes away over time to let the ratcheting or other pressure enhancing device hold in the greater sealing force from pressure loading on the set element  12 . This can be in the form of a coated threaded ring where the coating only dissolves after a time exposure at a given temperature. After that the well fluids attack the ring to the point of failure and the swelling of the element  12  can begin to set the packer P. Alternatively, the swelling of the element  12  can defeat the retainer  36  as could simply swaging the mandrel  10 .  
         [0064]     However, if the version shown in  FIG. 1  is revised so what is depicted at end  16  is also at end  14  in a mirror image, then it would make sense to surface treat the mandrel  10  in the middle section  34  as that section would not be moving during normal operation of the packer P. The surface treatment on the mandrel  10  can also act to hold the boost force from pressure loading that is anticipated once the packer P goes in service. Alternatively the element  12  itself can have a surface treatment where it contacts the mandrel  10  or both can be treated in the area of contact. Surface treatment on the mandrel can be multiple grooves, for example.  
         [0065]     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: