Patent Publication Number: US-7588077-B2

Title: Downhole tubular seal system and method

Description:
BACKGROUND OF THE INVENTION 
   In the hydrocarbon recovery industry it is often necessary to seal tubulars to one another in a downhole environment. Packers, for example, typically employ seals with packing elements that when actuated seal one tubular to another tubular. These seals can be complicated assemblies that require significant actuation forces to set as well as to maintain their seal integrity. Additionally, the reliability and durability of these seals in high pressure, high temperature and caustic environments often encountered downhole can be questionable. As such, a reliable downhole tubular to tubular seal that is easy to set would be welcomed in the art. 
   BRIEF DESCRIPTION OF THE INVENTION 
   Disclosed herein is a downhole tubular sealing system. The sealing system includes, a deformable tubular sealable to a first tubular and a second tubular. The deformable tubular includes, a first deformable portion configured to deform in a first radial direction, a second deformable portion configured to deform in a second radial direction, and a third deformable portion configured to deform in the first radial direction. The second deformable portion is positioned longitudinally between the first deformable portion and the third deformable portion and at least one of the first deformable portion and the third deformable portion is sealable to the first tubular when the first deformable portion or the third deformable portion is deformed. Further, the second deformable portion is sealable to the second tubular when the second deformable portion is deformed. 
   Further disclosed herein is a method of sealing downhole tubulars together. The method includes, positioning a deformable tubular in an annular space between a first tubular and a second tubular. The deformable tubular has a first deformable portion a second deformable portion and a third deformable portion. The second deformable portion is positioned longitudinally between the first deformable portion and the third deformable portion. Radially deforming the first deformable portion into contact with the first tubular. Radially deforming the second deformable portion into contact with the second tubular. Radially deforming the third deformable portion into contact with the first tubular. And sealingly engaging the first tubular to the second tubular by sealingly engaging the first tubular with at least one of the first deformable portion and the third deformable portion and sealingly engaging the second tubular with the second deformable portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
       FIG. 1  depicts a quarter cross sectional view of the tubular sealing system disclosed herein; 
       FIG. 2  depicts a deformable tubular disclosed herein shown in a deformed configuration within a sectioned tubular; and 
       FIG. 3  depicts a partial cross sectional view of the seal bead disclosed herein in a non-sealed configuration. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
   Referring to  FIG. 1 , the downhole tubular sealing system  10  disclosed herein is illustrated. The sealing system  10  includes a deformable tubular  14 , made of a strong deformable material such as metal, for example, positioned within an annular space  18  defined by a first tubular  22 , positioned radially outwardly of the deformable tubular  14 , and a second tubular  26 , positioned radially inwardly of the deformable tubular  14 . The deformable tubular  14  is sealable to both the first tubular  22  and the second tubular  26  when in a deformed configuration (as shown in  FIG. 2 ). The deformable tubular  14  has at least three deformable portions  30 ,  34 ,  38 , of which three are disclosed in this embodiment, positioned longitudinally along the deformable tubular  14 . The deformable tubular  14  is configured such that the second deformable portion  34  is located longitudinally between the first deformable portion  30  and the third deformable portion  38 . 
   Additionally, the deformable tubular  14  is constructed such that the second deformable portion  34  deforms radially in a direction opposite to a radial direction in which the first deformable portion  30  and the third deformable portion  38  deform. For example, in this embodiment, the second deformable portion  34  deforms radially inwardly and the first deformable portion  30  and the third deformable portion  38  deform radially outwardly. All three of the deformable portions  30 ,  34 ,  38 , in this embodiment, deform radially in response to axial compression thereof. The radial extent of the deformations is limited by contact that occurs between the deformable portions  30 ,  34 ,  38  and an inwardly facing surface  42  of the first tubular  22 , and an outwardly facing surface  46  of the second tubular  26 . More specifically, the deformable portions  30 ,  38  deform radially outwardly until seal beads  50  and  52 , positioned on the deformable portions  30  and  38  respectively, make contact with the inwardly facing surface  42 . Similarly, the second deformable portion  34  deforms radially inwardly until a seal surface thereon, disclosed herein as seal bead  54 , makes contact with the outwardly facing surface  46 . In this embodiment, the seal bead  52  sealably engages with the inwardly facing surface  42  while the seal bead  54  sealably engages with the outwardly facing surface  46 . The foregoing structure thus seals the first tubular  22  to the secondly tubular  26  through the sealing engagements of the tubulars  22 ,  26  with the deformable tubular  14  since the deformable tubular  14  has continuous walls between the seal bead  52  and the seal bead  54 . Forces causing the seal bead  54  to deform radially inwardly are magnified by the presence of the first deformable portion  30  and thereby increase the sealing integrity of the seal bead  54  with the surface  46 . Specifically how the first deformable portion  30  aids to sealing the deformable tubular  14  with the second tubular  26  will be described in greater detail below. 
   As mentioned above, deformation of the three deformable portions  30 ,  34 , and  38 , of the deformable tubular  14 , results from axial compression thereof. Such axial compression can be performed by any of a variety of actuation tools (not shown) that are known in the industry. In this embodiment the deformable tubular  14  has contact surfaces  62  and  66 , which essentially define the longitudinal extent of the deformable tubular  14  and provide surfaces for an actuation tool to contact during axial compression thereof. The redirection of axial compression of the deformable tubular  14  into radial deformation of the deformable portions  30 ,  34 ,  38  is facilitated by construction thereof. Such deformable construction can be created by local changes in physical strength of the material in the deformable portions  30 ,  34 ,  38 , for example. 
   Local changes in the physical strength of the deformable portions  30 ,  34  and  38  can be created by geometric features of the deformable portions  30 ,  34 ,  38 , as is the case with an embodiment disclosed herein. The deformable tubular  14  includes walls  70 ,  72 ,  74 ,  76 ,  78 , which form the deformable portions  30 ,  34  and  38  respectively. The walls  70 ,  72 ,  74 ,  76 ,  78  by being thinner than walls  82  are weaker and thus deform more readily than walls  82 . For example, the walls  78  on either side of seal bead  52  form legs  84  and  86 . Similarly, the walls  70  on either side of the seal bead  50  form legs  87  and  88 . The legs  84 ,  86 , having a greater radial dimension near the seal bead  52  as opposed to near either the wall  82  or the seal bead  54 , form a structure that tends to radially deform the legs  84 ,  86  in an outwardly direction in response to axial compression thereof. Additionally, in this embodiment the legs  84 ,  86  have an arcuate shape to further control the radial direction in which the walls  78  will deform. The walls  70  have a similar shape to that of the walls  78 , and as such the deformable portion  30  will also deform radially outwardly similar to that of the deformable portion  38 . In contrast, the radial relationship of the deformable portion  34  to the deformable portions  30  and  38  creates a structure that will cause the deformable portion  34  to deform radially inwardly in response to axial compression of the sealing system  10 . 
   As mentioned above, the presence of the first deformable portion  30  increases the inwardly directed forces on the second deformable portion  34  over what they would be without the first deformable portion  30  being present. This is due to the leg  88  of the first deformable portion  30  that is located between the seal beads  50  and  54 . The leg  88  need not be perfectly straight, but any out of straight configuration should be small such that the leg has substantial compressive strength over its length  89 . By being compressively strong, the leg  88  can become wedged between the inwardly facing surface  42  and the outwardly facing surface  46  in response to deformation of the first deformable portion  30 . Once the leg  88  is wedged, any additional axial compression of the deformable tubular  14  causes increased radial loading of the seal beads  50 ,  52  and  54  into the surfaces  42  and  46 . Adjusting the length  89  as compared to an annular dimension between the surfaces  42  and  46  can control the amount of radial loading in response to axial compression. For example, by setting the length  89  close to the annular dimension the force is increased. This is due to the increase in the angle of the leg  88  relative to an axis of the sealing system  10 . Such increases in radial forces between the deformable tubular  14  and the tubulars  22  and  26  will improve the sealing integrity therebetween. 
   The wedging action described above can also be used to control what pressures can be maintained by the sealing system  10 . For example, by setting a length of the leg  84  to become wedgably engaged between the first tubular  22  and the second tubular  26 , a pressure from downhole, in this embodiment, will put the wedged leg  84  into compression, thereby requiring the leg  84  to buckle before failure of the seal will occur. This wedging action causes an increase in downhole pressures to increase the sealing forces of both the seal bead  52  against the surface  42  and the seal bead  54  against the surface  46 , thereby improving the seal integrity in the process. Consequently, the sealing system  10  can seal much higher pressures with thinner walled components than conventional sealing systems. Consequently, actuation tools to actuate the sealing system  10  disclosed herein can be made smaller since less force is required to actuate the thin walled components. These smaller and thinner components and tools will save time and money in material and labor to construct while increasing robustness of seal integrity. The disclosed sealing system  10  also boosts seal integrity since the sealing components, specifically the deformable tubular  14 , can be made completely out of metal thereby increasing seal integrity over seals utilizing elastomers and polymers which can degrade chemically in high temperature, high pressure and caustic environments that are typically found downhole. 
   In addition to controlling the direction of deformation of the deformable portions  30 ,  34 ,  38 , thicknesses of the walls  70 ,  72 ,  74 ,  76 ,  78  can be used to control relative actuation timing of the three deformable portions  30 ,  34 ,  38 . For example, by making the walls  78  thinner than the walls  70 ,  72 ,  74  and  76 , and the wall  76  thinner than the wall  74 , the three deformable portions  30 ,  34 ,  38  can be made to deform in the sequence of deformable portion  38  first, deformable portion  34  second, and deformable portion  30  third. Such sequential control of deformation may be desirable since deformation and seal setting forces can be more accurately controlled if there is not a deformed and actuated seal located between the actuator and the deformable portion being actuated as could happen without adequate control of actuation sequences. 
   Varying wall thicknesses of the walls  70 ,  72 ,  74 ,  76 ,  78 , can control deformation, of the deformable portions  30 ,  34 , and  38 . In  FIG. 2 , for example, the deformable portion  38  is deformed longitudinally nonsymetrically about the seal bead  52 . The leg  84  on an uphole side of the seal bead  52 , in this embodiment, has undergone more deformation than the leg  86  on a downhole side of the seal bead  52 . As a result, the deformable tubular  14  when made from a workhardenable material, such as steel, for example, can be made to be workhardened to varying degrees at different locations. Controlling the degree of work hardening in different locations of the deformable tubular  14  can permit a designer of the sealing system  10  to control the amount of pressure that can be maintained by the sealing system  10  without leakage, for example, since the material strength due to the work hardening can be precisely estimated. Such pressure control via workhardening of the materials can used in unison with the pressure control via wedging of legs as described above. 
   Additionally, the thicknesses of the walls  70 ,  72 ,  74 ,  76 ,  78  can be used to prevent over compression of the seals  50 ,  52  and  54 . For example, as described above, the wall thicknesses controlled both the deformation and sequence of actuation of the deformable portions  30 ,  34 , and  38 . As such, the deformable portion  38 , as shown in the embodiment in  FIG. 2 , deformed first, followed by the deformable portion  34  and finally deformable portion  30 . Once all three deformable portions  30 ,  34 ,  38  are deformed and the seal beads  50 ,  52  and  54  are sealably engaged with the surfaces  42  and  46 , additional axial compression of the deformable tubular  14  does not increase compression of the seal bead  54 , but instead causes additional deformation of the leg  87 . Such control allows a designer of the seal system precise control over the maximum sealing engagement forces at specific seals. 
   Seal integrity can also be enhanced by seal redundancy. Seal redundancy between the deformable tubular  14  and the first tubular  22  can be achieved by using both seal beads  50  and  52  to seal to the first tubular  22 . Using both seal beads  50 ,  52 , however, could have a negative effect on sealability due to fluid presence causing a hydraulic lock between the first deformable portion  30  and the second tubular  26 , for example, and as such may be undesirable. Whether or not to utilize both seal beads  50  and  52  for sealing can therefore be made on an application-by-application basis. In this embodiment, apertures  90  in walls  70  have been incorporated to provide a fluid bypass around the seal of the seal bead  50 . 
   Referring to  FIG. 3 , in order to improve seal integrity in situations where one or both of the inwardly facing surface  42  and the outwardly facing surface  46  are not smooth surfaces, for example, it may be desirable to use a soft material  92  in the seal beads  50 ,  52 ,  54  of the deformable tubular  14 . Such a soft material can more easily conform to imperfections in the surfaces  42 ,  46  than the base material of the deformable tubular  14 , to facilitate sealing. Making the complete deformable tubular  14  out of a soft material could significantly decrease the pressure at which the sealing system  10  is reliable and may therefore be undesirable. Embodiments of the invention can, therefore, use a material softer than the balance of the deformable tubular  14  only at the seal beads  50 ,  52  and  54 , for example. A coating or plating of a softer metal than the balance of the deformable tubular  14  such as lead or copper, for example, could be deposited onto the surface  50 ,  52 , and  54 . Alternately, a softer material  92  such as an elastomer or a polymer, for example, could be positioned within a cavity  94  on the beads  50 ,  52 ,  54 . 
   In addition to increasing a resiliency of the sealing system  10  through the use of softer materials at the seal engagement the resiliency can be further increased by controlling stress of the deformable tubular  14  in the area of the seal beads  52 ,  54  so that legs  84 ,  86 ,  88 ,  89  act as springs. One way to accomplish this is to form the deformable tubular  14  so that a surface  98  of the seal beads  50 ,  52 ,  54  is not parallel to the surfaces  42 ,  46  to which they will seal. For example, by setting the surface  98  at a small angle  102  relative to the surface  42 ,  46  the legs  84 ,  86 ,  88 ,  89  are made to flex in response to radial deformation of the deformable portion  38 , which causes the surface  102  to become parallel with the surface  42 ,  46 . By being small the angle  102  can precisely control the amount of flexing, and thus stress, that the legs  84 ,  86 ,  88 ,  89  undergo, thereby preventing plastic deformation. This method provides a designer of the sealing system  10  with a reliable way to control elastic deformation of the deformable tubular  14  when in the deformed and sealed configuration. 
   While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.