Abstract:
A tie back assembly that uses expansion for connection and sealing is disclosed. The male component does not have any wall portions removed to hold a resilient seal. A seal is an option as anchoring and sealing can be accomplished by the expansion alone. The pressure rating of the connection is not reduced by material removed to accommodate a seal. A variety of expansion techniques can be used and the expansion can be done in a single trip with the insertion of the tie back assembly into the receptacle or in a separate trip.

Description:
FIELD OF THE INVENTION 
   The field of this invention is a seal or anchor assembly that can be inserted into a downhole seal bore and seal or anchor a tubing string to the bore as a result of expansion. 
   BACKGROUND OF THE INVENTION 
   Seal bores have been in use to allow a string to be lowered downhole and secured and sealed. Typically, a packer or plug has a polished bore in it to act as the receptacle for the lower end of a string run into the well from the surface after the packer or plug is set. At the lower end of the string is what is known as a tieback seal assembly. This assembly comprised a male component to go into the female seal bore. There is a single or multiple grooves on the male component to hold a seal. The seal can be an o-ring or a stack of chevron shaped rings. Regardless of the nature of the seal material used, there is an interference fit between the seal material and the surrounding bore to energize the seal material in the seal bore. Frequently, the seal bore is polished to minimize damage to the seal assembly during the insertion process. At times, guides or centralizers are used to assist in the alignment of the male component with the seal into the seal bore. One such device is illustrated in U.S. Pat. No. 5,330,001. Other art, such as U.S. Pat. Nos. 6,098,717 and 6,446,724 illustrate expanding one tubular into another. 
   Typically, the seal or seals are placed in a groove in the tieback assembly male component. The removal of metal that is necessary to form the groove or grooves for holding the seal or seals takes away a portion of the wall and reduces the pressure rating of the connection. What is needed and has not previously been provided is a connection that removes this pressure rating reduction due to the presence of the groove or grooves to hold a seal or seals. The present invention addresses this need by providing a tieback assembly where wall portions are not removed to provide a mounting location for a seal or seals. Instead, the concept of expansion in place is used. Where a seal is actually used, it can be in the form of an exterior coating that gets forced into contact with the seal bore receptacle as a result of expansion. Sealing or anchoring with metal-to-metal contact without the use of resilient seals is contemplated using the expansion technique. These and other advantages of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the claims, which appear below. 
   SUMMARY OF THE INVENTION 
   A tie back assembly that uses expansion for connection and sealing is disclosed. The male component does not have any wall portions removed to hold a resilient seal. A seal is an option as anchoring and sealing can be accomplished by the expansion alone. The pressure rating of the connection is not reduced by material removed to accommodate a seal. A variety of expansion techniques can be used and the expansion can be done in a single trip with the insertion of the tie back assembly into the receptacle or in a separate trip. Grip enhancing features are possible as is a temporary seal to give a surface signal that the connection is made prior to expansion. The tieback an be movably secured to the liner top to allow pulling out the seals without disconnection of the joint to permit cement delivery into the joint prior to reinsertion of the seals before the cement sets. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a section view of the joint with the tie back inserted into the receptacle and prior to expansion; 
       FIG. 2  is the view of  FIG. 1  after expansion of the tie back; 
       FIG. 3  is a run in view showing one form of grip enhancement; 
       FIG. 4  is the view of  FIG. 3  in the expanded position; 
       FIG. 5  shows a thread form of a grip enhancer; 
       FIG. 6  shows a surface roughness form of a grip enhancer; 
       FIG. 7  shows an alternative embodiment illustrating the use of a temporary seal, in the run in position; 
       FIG. 8  is the view of  FIG. 7  in the expanded position; 
       FIG. 9  is an alternative embodiment showing seals that engage on insertion and a retainer activated by an expansion tool, in the run in position; 
       FIG. 10  is the view of  FIG. 9  with the retainer engaged in the groove after expansion; and 
       FIG. 11  is the view of  FIG. 10  with the seals pulled out and a port exposed for cement passage, while the retainer still holds the connection together. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a liner top or other body  10  has a receptacle  12 . The receptacle  12  may be polished. A tie back  14  is located at the lower end of a tubing string  16 . The outside diameter  18  of the tie back  14  before expansion is less than the inside diameter  20  of the receptacle  12 . This dimensional relationship allows for easy insertion of the tie back  14  into the receptacle  12 . One or more seals, shown schematically as  22  are secured to the outside diameter as an option. The seal  22  can alternatively be secured to the receptacle  12 . The wall thickness  24  is not reduced to apply the seal  22 . The wall thickness  24  may be initially oversized for the intended pressure rating to compensate for any thinning of the wall during the expansion process. Alternatively, the seal  22  can be omitted and sealing contact between surfaces  26  and  28  can occur through expansion tool  30 , which is show schematically in  FIG. 1 . The wall thickness  24  may be constant. However, even the use of a seal  22  will not require a wall thickness reduction for such items as recesses or grooves that could decrease the pressure rating of the finished connection. Those skilled in the art will appreciate that a variety of known swage assemblies can be used. The expansion tool  30  can be delivered with the tubing  16  and the expansion initiated when the tie back  14  is inserted into the receptacle  12 . Alternatively, the expansion tool can be delivered in a separate trip, through tubing  16 . 
   As shown in  FIG. 2 , after expansion the seal  22 , if used, is compressed between surfaces  26  and  28 . The inside diameter  32  of the tie back  14  is at least equal to or greater than the diameter  34  immediately adjacent the receptacle  12 . With the tubing  16  secured to the body  10 , the expansion tool  30  can now be withdrawn through the tubing  16 . 
   Referring to  FIG. 3 , the tieback  14  or the body  10  can further include a profile  36  designed to penetrate the opposing member at expansion. The penetration is shown in  FIG. 4 . The profile  36  can be a series of parallel rings, a thread, a regular or irregular pattern of projections and/or depressions. Is can be on either member or on both and if on both the projection  36  on each member could be aligned or misaligned. As shown in  FIG. 5 , a thread  38  can be added to either body, although shown on the tieback  14 . A ring, either whole or split or segments banded together  40  can be secured to thread  38 . Alternatively, as shown in  FIG. 6 , a surface roughness  42  can be created preferably of randomly positioned carbide particles or equivalent hard material that will preferably penetrate the opposing body in expansion. The roughened surface can be on either body or both and if on both, the sections treated can be in alignment or can be misaligned. Similarly, the threaded ring  40  option shown in  FIG. 5  can be on one body or both, although it is preferred to put it on the tieback  14  so as to avoid removing material from body  10 . If the threaded ring  40  is on both bodies its placement can be aligned or misaligned. 
   Referring now to  FIG. 7 , a temporary seal  44  is installed on tieback  14 . This seal makes contact with the receptacle  12  during run-in. Its purpose is to allow a surface signal that the connection is made. It doesn&#39;t have to hold pressure perfectly and it is possible that it may be extruded out as a result of expansion, shown in  FIG. 8 . Once the tieback  14  is in the receptacle  12  the surface personnel can build pressure and know the connection is made by seeing a pressure buildup at the surface. It should be noted that the seals  22  shown in  FIG. 1  will not make receptacle  12  contact when the tieback is inserted. Seal  44  can be used with or without seals  22 . As shown in  FIG. 8 , the expansion alone can result in the seal even if the temporary seal  44  is squeezed out during expansion. 
   Turning now to  FIGS. 9–11 , the tieback  14 , comprises on or more seals  46 , although four are shown. These seals engage the receptacle  12  upon insertion. Many operators like to pump cement into the receptacle  12  after initially inserting the tieback  14  and then temporarily pulling it out. The problem that occurs when the cold cement is pumped into the receptacle  12  the tieback  14  shrinks in length to the point that the connection can come completely apart. Ideally, the operator only wants to get the seals  46  out of the receptacle  12  when the cement is pumped but not any further. The contraction due to the cement pumping made the connection come further apart than was desirable, so that re-insertion of the tieback  14  into the receptacle  12  could create a problem. Timing was important during this procedure because the cement was setting up. To solve this problem the body  10  is provided with a recess  48 . The tieback  14  has an inwardly oriented projection  50  preferably near its lower end  52 . When the expansion tool  54  is advanced past projection  50  it reverses the orientation of projection  50  so that it looks away from the central axis  56  and into recess  48 . A port  56  is provided in tieback  14 . As shown in  FIG. 11 , the tieback  14  can be pulled up until projection  50  catches in an end of recess  48 . In that position, port or ports  56  are exposed for cement flow and the seals  46  are out of the receptacle  12 . However, the connection is not fully apart and can&#39;t come apart even due to shrinkage from the flowing cold cement. Instead, a tensile stress develops in the tieback  14  that is resisted by projection  50  engaging the recess  48 . After the cement is pumped and before it sets, weight is set down on the tieback  14  to reinsert the seals  46 . 
   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.