Patent Abstract:
Disclosed herein is a downhole disconnectable and length compensatable tubular sealing system. The system includes, a seal connector having a first metal seal receptive of a separate seal nipple and pressure sealably engagable therewith and at least one expansion joint sealingly connected to the seal connector. The expansion joint includes, a section of metal tubing having a sealing surface thereon and a metal-to-metal seal slidably sealingly engaged with the sealing surface.

Full Description:
BACKGROUND OF THE INVENTION 
   The hydrocarbon recovery industry often has a need to seal tubulars to downhole structures. Such seals are exposed to caustic chemicals as well as high temperatures and high pressures that can degrade seals and that can result in undesirable leakage. Additionally, variations in temperature cause contraction and expansion of tubulars sealed to one another positioned within the wellbore. Such contraction and expansion can put stress on the seals, which may result in premature failure of the seals. The art, therefore, would be receptive to downhole tubular sealing systems that can maintain seal integrity during exposure to the foregoing conditions. 
   BRIEF DESCRIPTION OF THE INVENTION 
   Disclosed herein is a downhole disconnectable and length compensatable tubular sealing system. The system includes, a seal connector having a first metal seal receptive of a separate seal nipple and pressure sealably engagable therewith and at least one expansion joint sealingly connected to the seal connector. The expansion joint includes, a section of metal tubing having a sealing surface thereon and a metal-to-metal seal slidably sealingly engaged with the sealing surface. 
   Further disclosed herein is a method of length compensatingly sealably connecting a tubular to a downhole structure. The method includes, positioning a metal nipple sealingly engaged to an actuatable first metal seal within a downhole structure, actuating the first metal seal to thereby sealingly engage the first metal seal to the downhole structure, positioning a metal seal connector having a second metal seal at the metal nipple, radially deforming the second metal seal to sealingly engage the metal seal connector to the metal nipple and slidably sealingly engaging at least one first metal tubular to at least one second metal tubular with a metal-to-metal seal. Additionally, the at least one second metal tubular is sealingly engaged to the metal seal connector. 

   
     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 the tubular sealing system disclosed herein being run downhole; 
       FIG. 2  depicts a metal seal disclosed herein; and 
       FIG. 3  depicts the tubular sealing system of  FIG. 1  connected to a downhole nipple. 
   

   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 , an embodiment of the downhole disconnectable and length compensatable tubular sealing system  10 , disclosed herein, is illustrated. The tubular sealing system  10  includes, among other things, a seal connector  14  having an actuatable metal seal  18 , and an expansion joint  22 , both of which utilize all metal seals as disclosed herein as will be described below. The seal connector  14  is sealable to a nipple  26  with the actuatable metal seal  18 . The nipple  26  is sealable to a sealing surface  30  of downhole structure  32  such as a casing or wellbore, for example, with a metal seal  34  in a device such as a packer, for example. The foregoing structure allows a well operator to sealably connect and disconnect tubulars, suspended from the surface, to the nipple  26 , while the nipple  26  remains downhole and sealed to the structure  32 . The expansion joint  22  includes a first tubular  38  having a seal surface  42 , depicted herein as an inner diametrical surface thereon, and a metal-to-metal seal  46 , sealably attached to a second tubular  48 . This arrangement can be used to convey fluids, such as mud and steam, for example, downhole, as well as to recover hydrocarbons from downhole during production. By incorporating the metal seals  18 ,  34  and  46 , the sealing system  10  is able to withstand the high temperatures, high pressures and caustic environments often encountered downhole while sealingly compensating for contractions and expansions of tubulars within the system that occur with changes in temperature, including ultra high temperatures encountered with some steam injection processes. 
   Referring to  FIG. 2 , an embodiment of the metal seals  18 ,  34  and  46  is illustrated in a non-actuated and thus non-sealing configuration. The metal seals  18 ,  34  and  46  in this embodiment include a radially deformable portion  50 . The radially deformable portion  50  has areas of weakness  54 ,  58  that deform in response to axial compression of the metal seal  18 ,  34  and  46 . In this embodiment, the areas of weakness  54 ,  58  are formed by changes in thickness of a wall  62  of the seal  18 ,  34  and  46 . Alternate embodiments could have the areas of weakness formed in other ways such as by changes in material properties, for example. A direction of radial deformation of the seal  18 ,  34  and  46 , in this embodiment, is controlled by geometric relationships of each of the areas of weakness  54  and  58  to one another. For example, if the areas of weakness  58  are positioned at a larger radial dimension from an axis of the seals  18 ,  34  and  46  than the areas of weakness  54 , the areas of weakness  58  will tend to deform radially outwardly in response to axial compression thereof, as is the case for seals  34  and  46 . Such outward radial deformation can continue until an optional seal bead  66  contacts a seal surface of a mating component. Alternately, by positioning the areas of weakness  58  radially inwardly relative to the areas of weakness  54  the areas of weakness will tend to deform radially inwardly in response to axial compression thereof, as is the case for seal  18 . 
   Once seal bead  66  contacts a mating sealing surface, such as the seal surface  30  or  42 , additional axial compression of the seals  18 ,  34  and  46  will cause deformation of legs  70 , located on either longitudinal side of the seal bead  66 . Since the legs  70  are primarily in compression, due to the geometrical relationship of the legs  70  to the deformable areas  54 ,  58 , any deformation of the legs  70  will tend to be in the form of buckling. In order to control such buckling deformation of the legs  70  a non-straight configuration of the legs  70  may be desirable. In the embodiment of  FIG. 2 , for example, this non-straight configuration is an arc. Thus, the legs  70  will tend to deform in a bowed shape as they are compressed. This bowing shape is quite stable and permits the deformed legs  70  to retain elasticity such that they act as biasing members that spring back when the compressive loads are removed. As such, the seals  18 ,  34  and  46  are able to accommodate larger variations in dimensions of the mating seal surfaces  30 ,  42 , and  74  than they would with less elastic leg configurations. 
   The radial deformation of the seals  18 ,  34 ,  46  that results from axial compression of the seals  18 ,  34  and  46  provides another advantage to a well operator. Deformation of the seals  18 ,  34  and  46  is reversible. That is, axial expansion of the seals  18 ,  34  and  46 , after they have been radially deformed, causes the radial deformation to reverse such that the seals  18 ,  34  and  46  return to their original shape, or near original shape. After such reverse deformation, the metal seals  18 ,  34  and  46  are no longer sealingly engaged with their mating seal surfaces  30 ,  42  and  74  and as such can be withdrawn from their mating seal surfaces  30 ,  42  and  74 . Linear actuator tools, known in the industry, can, therefore, be used to axially compress and axially expand the seals  18 ,  34 ,  46  thereby causing increases and decreases in radial deformation thereof. 
   Referring again to  FIG. 1 , increases and decreases in radial deformation of the metal seal  18 , of the seal connector  14 , allows the metal seal  18  to sealably connect and disconnect from the nipple  26 . To seal the seal connector  14  to the nipple  26 , in this embodiment, the metal seal  18  is positioned around the nipple  26  and the metal seal  18  is axially compressed causing the metal seal  18  to deform radially inwardly until it makes contact with and sealingly engages with a seal surface  74  of the nipple  26 . It should be noted that alternate embodiments could have a nipple with a sealing surface on an inner radial surface as opposed to an outer surface thereof. Such a nipple would be sealable to a radially outwardly expandable metal seal similar to the seals  34  and  46 . The nipple  26 , by being made of metal, establishes a metal-to-metal seal with the metal seal  18  of the seal connector  14 . Additionally, alternate embodiments (not shown) could have the metal seal  18  already in a radially deformed configuration prior to being sealably connected to the nipple  26 . Such an embodiment would need piloting features to align the nipple  26  with the metal seal  18  prior to engagement therewith. A tapered or radiused nose on the nipple  26  would also be helpful in guiding the nipple  26  into the metal seal  18  to prevent damage to either component during assembly therebetween. 
   The metal seal  46  while being sealingly engaged with the seal surface  42  can also slide axially relative to the first tubular  38 . As such, an axial length of the seal surface  42  can be set according to the needs of each particular application to accommodate an axial expansion and contraction of the tubulars  38  and  48  that is expected due to the anticipated temperature changes that will be encountered. 
   Referring to  FIG. 3 , an axial length of the sealing engagement of the seal  46  with the surface  42 , in the expansion joint  22 , can be limited by locating a series of stops along the first tubular  38  and the second tubular  48 . For example, a first stop  78  on the first tubular  38  that is contactable with a second stop  82  on the second tubular  48  will limit an axially expansive travel of the expansion joint  22  when the first stop  78  comes into contact with the second stop  82 . Similarly, a third stop  86  on the first tubular  38  that is contactable with a fourth stop  90  on the second tubular  48  will limit axially compressive travel of the expansion joint  22  when the third stop  86  comes into contact with the fourth stop  90 . Such travel limits of the expansion joints  22  can allow a well operator to more precisely determine locations of components along a drill string after running downhole. 
   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.

Technology Classification (CPC): 4