Abstract:
A packer element has a biasing member incorporated with it. The element is either fabricated with the biasing element in a relaxed condition and then the element is stretched prior to insertion downhole or the element is created around the stressed biasing member and is held in that position until allowed to relax downhole. In either event the release of the element increases its diameter while shortening its length. Preferably, an advancing swage triggers the release to allow the element to expand as much as it can go or to the maximum relaxed diameter, whichever is larger. The swage then, preferably, drives the relaxed element toward the borehole wall or the casing.

Description:
PRIORITY INFORMATION 
   This application claims the benefit of U.S. Provisional Application No. 60/474,486 filed on May 30, 2003. 

   FIELD OF THE INVENTION 
   The field of this invention is downhole packers and more particularly those that are set with expansion force and finally those that use a bias to increase diameter independently of the applied expansion force. 
   BACKGROUND OF THE INVENTION 
   Annular spaces downhole are typically sealed with packers. Packers can be used in cased or open hole. One type of packer involves an element mounted to a mandrel, where the element is made of an elastomer. The packer is placed downhole and can be set by mechanical compression of the element. The longitudinal mechanical compression increases the diameter. Another technique has been to simply expand the mandrel to increase the outside diameter of the annularly shaped element. One such technique is the Poroflex® product from Halliburton, which uses a solid ribbed elastomer sleeve that is longitudinally compressed by an advancing swage. The driving of the swage also increases the mandrel diameter. The ribbing allows part of the sleeve to collapse on itself in a series of accordion folds. The forming of the folds is claimed to bridge the annular gap around the mandrel. The swage is sized so as not to collapse the accordion folds of the collapsed elastomer sleeve. This product is advertised for cased hole applications and appears unsuitable for open hole applications. It also has some uncertainties as to how well it will seal. Longitudinal compression will not always assure that the sleeve will collapse uniformly over the ribbed length. The sealing occurs by end contact of each accordion fold with the casing wall. The number of such ends in contact with the casing wall due to collapse and expansion is uncertain. The possibility, even in cased hole, exists for channeling between the fold ends and the casing wall. The element is not pre-stretched to reduce its run in diameter and therefore can get thinner after swaging to the point where the sealing integrity may be in question. Accordingly, a design is needed that can better address the above described sealing problems in cased hole and that has the ability to seal effectively in open hole. 
   The present invention employs an annular sleeve as the sealing element and mounts a biasing element with it. The biasing element stores a force, which is liberated downhole to longitudinally compress the element and increase its diameter. In a preferred embodiment the advancing swage liberates a stored force to allow the element diameter to grow to its relaxed dimension. Preferably, the advancing swage liberates this force and increases the mandrel dimension when the element is already at its relaxed diameter forcing the element into the borehole wall or the casing. How this is accomplished, so that those skilled in the art will readily appreciate the scope of the invention, will be explained more fully in the detailed description of the preferred embodiment and the claims, which appear below. 
   Relevant to the general area of sealing devices, with some illustrating downhole applications are U.S. Pat. Nos. 2,449,514; 4,545,433; 5,062,482; 6,543,780 B1 and Re. 32,831. 
   SUMMARY OF THE INVENTION 
   A packer element has a biasing member incorporated with it. The element is either fabricated with the biasing element in a relaxed condition and then the element is stretched prior to insertion downhole or the element is created around the stressed biasing member and is held in that position until allowed to relax downhole. In either event the release of the element increases its diameter while shortening its length. Preferably, an advancing swage triggers the release to allow the element to expand as much as it can go or to the maximum relaxed diameter, whichever is larger. The swage then, preferably, drives the relaxed element toward the borehole wall or the casing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a run in cross-section of a coiled spring embodiment shown in an open hole application; 
       FIG. 2  is the view of  FIG. 1  showing the coiled spring allowed to relax to expand the diameter of the element; 
       FIG. 3  is the view of  FIG. 2  showing the swage advanced to expand the mandrel under the already diametrally enlarged element; 
       FIG. 4  is an alternate embodiment to  FIG. 1  using a leaf spring and shown in the run in position; 
       FIG. 5  is the view of  FIG. 4  in the spring-relaxed position where the diameter of the element has enlarged; 
       FIG. 6  is the view of  FIG. 5  after expansion of the mandrel with a swage; 
       FIG. 7  is an alternative to  FIG. 1  without any biasing and where the element is stretched to reduce its run-in diameter; 
       FIG. 8  is the view of  FIG. 7  with the element in a relaxed position; 
       FIG. 9  is the view of  FIG. 8  after the mandrel is swaged; 
       FIG. 10  is a detailed view of the latch at run in; 
       FIG. 11  is the view of  FIG. 10  with expansion releasing the latch to allow the element to shrink in length and expand in diameter; 
       FIGS. 12–16  are a sequential view showing how the advancing swage releases the latch and passes through to finish the expansion. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a mandrel  10  with an element  12  that has a biasing element  14 , which, in this Figure happens to be a coiled spring. Those skilled in the art will recognize that other types of biasing elements are contemplated, such as: leaf springs (see  FIGS. 4–6 ), Belleville washers or even no biasing element at all (see  FIGS. 7–9 ). The advantage of pre-stretching is that the initial outside diameter is reduced. For example, in a monobore application, the mandrel  10  and the element  12  must fit through the casing  16  and after expansion in open hole  18 , assume an inside diameter  20  (see  FIG. 3 ) approximating that of the casing  16 . Without pre-stretching to reduce the outside diameter of the element  12  the element thickness has to be reduced for a given mandrel diameter. Later when expansion takes place in open hole, the element may not make sealing contact with the borehole wall  18 . 
   The present invention, as shown in  FIG. 1 , involves building a relaxed spring into the un-stretched element  12  and then stretching the assembly and holding it in that position for run in. Preferably, retainer  22  is fixed to mandrel  10  while retainer  24  is temporarily secured by a latch or another equivalent device shown schematically as  26 . Advancing the swage  28  releases the latch  26  and allows the element  12  to shorten in length and to grow in diameter, aided by the stored force in spring  14 . Spring  14  wants to get shorter when latch  26  is tripped. Now, as shown in  FIG. 2  element  12  has shrunk in length and grown in diameter so that its outside diameter is substantially larger than during the run in. Now, when the swage  28  advances under the element  12  there is a better assurance that the element  12  will seal against the borehole wall  18 . Those skilled in the art will appreciate that the illustrated embodiments of the device can be used in cased as well as in open hole. 
   An alternative way to make the device in  FIG. 1  is to build an element  12  over an extended spring  14  and hold the element against shrinkage until it is delivered through casing  16 . When the swage  28  is advanced and latch  26  is released, the spring  14  can relax and shorten the element  12  to make its diameter increase before the swage  28  expands the mandrel  10  under the element  12 . 
   The spring  14  may be bonded to element  12 , which is preferably a cured elastomer. The boding may be total or partial. Alternatively, there may be no bonding at all. The spring  14  can be totally imbedded in the element  12  or it may be partially embedded or mounted externally in a manner that its relaxation will reduce the length and increase the diameter of the element  12 . 
     FIGS. 4–6  operate identically to  FIGS. 1–3  and may be manufactured in the two ways described above for  FIGS. 1–3 . Again, the casing is  16 ′. The difference is that the spring is a leaf spring  30  that collapses on itself when latch  26 ′ is released. Those skilled in the art will appreciate that the leaf spring  30  may be composed of segments that are independent or tied together or a solid ring. Similarly, spring  14  can be one or more springs which could be stacked or nested. Each coil spring can have a constant or variable diameter or a constant or a plurality of pitches. The wire diameter can vary, as can the materials of construction even within a single spring. If Belleville washers are used, they can be stacked in one direction or stacked in more than one direction and can incorporate material and dimensional variations to obtain the desired performance. 
   Ideally, after the element  12  or  12 ′ has attained its relaxed large diameter shown in  FIGS. 2 and 5 , the expansion of mandrel  10  or  10 ′ will ensure that there is tight sealing contact with the borehole wall. Since expansion of mandrel  10  can further reduce its length, there is an added force created on the element  12  tending to longitudinally compress it. The element  12  makes contact with the borehole  18  over a substantial portion of its length, as compared with the contact of the accordion folded ends of the Halliburton product. 
     FIGS. 7–9  illustrate the same element  12 ″ that now is without any associated biasing structure. It is simply initially stretched to reduce its outer dimension for run in. Advancing the swage  28 ″ will allow it to shrink in length and expand in diameter. The mandrel  10 ″ can then be expanded to get the element  12 ″ up against the borehole wall  18 ″. Here again, expansion of the mandrel past retainer  24 ″ will result in a further compression of element  12 ″ that is trapped between retainer  24 ″, now fixed to mandrel  10 ″ due to expansion and retainer  22 ″ that was initially connected to mandrel  10 ″. This is because diametral expansion results in a shortening of length of the mandrel  10 ″. Alternatively, the swage  28 ″ can actually drive the retainer  24 ″ along mandrel  10 ″ so that the element  12 ″ is compressed against retainer  22 ″. 
     FIGS. 10 and 11  show respectively, the latch mechanism  26  which is preferably a ring  32  that shears on movement of the swage  28  to allow the element  12  to shrink, shown in the run in and released position. Other devices that release on mandrel expansion are within the scope of the invention.  FIG. 10  shows ring  24  having a hook  40  that is retained by ring  32 . Ring  32  can be assembled in pieces that are held to each other by a breakable member  42 . Ring  32  is held from moving longitudinally by retaining rings  44  and  46  that are mounted on either side of it. Rings  44  and  46  can be overlapping open rings that simply grow in diameter when the swage  28 , see  FIG. 11 , breaks the breakable member  42  to release the hook  40  to allow the spring  14 , if used, to draw up ring  24  while the element  12  shrinks in length and grows in diameter.  FIGS. 12–16  show in sequence the latch release procedure just described as seen from a larger perspective. In  FIGS. 12 and 13 , the swage  28  approaches the latch mechanism  26 . In  FIG. 14  the latch mechanism  26  is released.  FIG. 15  shows that on further advance of the swage  28 , the latch mechanism  26  has shifted because the mandrel  10  has shrunk in length due to the expansion.  FIG. 16  shows the swage  28  passing under the element  12 , which is now pressed firmly against the casing wall  18 . 
   Those skilled in the art will appreciate that the present invention reduces the element thickness by stretching it. It can then pass through casing into open hole and be released. If a biasing member is used, it will aid in the longitudinal shrinking and the radial expanding of the element. The swage can be the trigger for the release of the element and ultimately the device that expands the mandrel to force the already relaxed and larger in diameter element against the borehole wall. 
   The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.