Abstract:
Systems and methods for installing an elastomeric element onto a packer mandrel or other existing oil field tubular equipment. In particular aspects, the packer device has a swellable elastomeric packer element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 12/134,559 which was filed Jun. 6, 2008 and which claims the priority of U.S. Provisional Patent Application Ser. No. 60/933,471 filed Jun. 6, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to packer devices. In particular aspects, the invention provides devices and methods for securing a packer element to a packer mandrel. 
         [0004]    2. Description of the Related Art 
         [0005]    Packers are used to create a fluid seal within a wellbore between a tool string and the wellbore wall. Packer devices incorporate elastomeric sealing elements that surround a central mandrel. Particular variations of these packers are those that employ elements that respond to the surrounding well fluids and swell to form a seal. The packer device is incorporated into a wellbore toolstring and disposed into the wellbore. When the packer is to be set, the packer element is extruded or expanded radially, as is known in the art, to contact and form a seal against the wellbore wall. 
         [0006]    In certain situations, there are problems with timely delivery and cost associated with conventional packer elements because of the limited number of manufacturers capable of making the parts and delays associated with material procurement and processes required to manufacture the conventional packers. One way of mitigating manufacturing lead time and costs is to create vulcanized or cured rubber sleeves that can be slid over a mandrel, which, in this case, could be any existing oilfield tubular equipment, and adhered directly. The inner diameter of the cured sleeve is sized to form to the outer diameter of the mandrel, and with a cured sleeve of the rubber element, the strength of the rubber requires the assistance of machinery to allow the sleeve of rubber to be slid over the end of the mandrel to the desired position. The inventor has observed that a packer sealing or barrier element formed of an elastomer that expands or swells upon contact with wellbore fluids can be adhered directly to a mandrel or other existing oil field tubular equipment without the use of assisting machinery by wrapping a helically-cut, cured sleeve of rubber around the desired position of the mandrel. If the element is merely slipped onto the mandrel from an end, in the manner of a continuous cylindrical sleeve, any adhesive can be wiped off, possible resulting in a poor bond of the packer element to the mandrel. Wrapping a helically cut sleeve over the area prepared with adhesive would eliminate the wiping effect created by a solid sleeve in addition to eliminating the need for assisting machinery. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention provides systems and methods for installing an elastomeric element onto a packer mandrel or other existing oil field tubular equipment. In particular aspects, the invention relates to the assembly of a packer device having a swellable elastomeric packer element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The structure and operation of the invention will be more readily understood with reference to the following drawings, which are illustrative thereof and among which like components are numbered with like reference numerals: 
           [0009]      FIG. 1  illustrates an exemplary curing mandrel having elastomeric material applied to it. 
           [0010]      FIG. 2  depicts removal of cured elastomer from the curing mandrel. 
           [0011]      FIG. 3  illustrates the operation of applying the cured elastomer to a packer mandrel. 
           [0012]      FIG. 4  illustrates an exemplary operation for disposing an uncured elastomer upon a packer mandrel. 
           [0013]      FIG. 5  depicts an exemplary technique for curing uncured elastomer upon the packer mandrel using curing wraps. 
           [0014]      FIG. 6  depicts that arrangement shown in  FIG. 5  now with an exemplary heating source applied. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    In accordance with an embodiment of the present invention, uncured elastomer  10  is disposed onto a generally cylindrical curing mandrel  12  of desired size, as illustrated in  FIG. 1 . These rubbers or elastomers are of the type that will swell in response to contact with fluids of the type found within a wellbore. No bonding material is used between the curing mandrel  12  and the elastomer  10 . The elastomer  10  is then cured in place on the curing mandrel  12  in a manner known in the art. Upon completion of curing, the cured elastomer  10  is then removed from the curing mandrel  12 . In a preferred embodiment, the cured elastomer  10  is removed by first cutting through the elastomer  10 . It is further preferred that the cuts  14  form a spiral or helical pattern so that the cured elastomer that is to be removed is in a substantially helical pattern. The elastomer  10  is then unwrapped from the curing mandrel  12  as indicated by the arrow  16  in  FIG. 2 . 
         [0016]    The cured elastomer  10  is then applied and secured to the outer radial surface of a generally cylindrical packer mandrel or other tubular oilfield equipment  18 , as depicted in  FIG. 3 . It is noted that the packer mandrel  18  preferably has the same or similar diameter to that of the curing mandrel  12  so that the elastomer  10  can be wrapped onto the packer mandrel  18 , as in the direction depicted by arrow  19  in  FIG. 3 , and form a complete and substantially intact cylinder without discontinuities. Preferably, a bonding agent is used to help bond the elastomer  10  to the packer mandrel  18 . In a currently preferred embodiment, the bonding agent comprises a suitable epoxy. A heated liquid elastomer is preferably also applied to the seams corresponding to the cuts  14  previously made in the elastomer  10  to adhere the cuts/seams  14  together and integrate the elastomer  10 . The elastomer  10  is preferably then retained in place upon the packer mandrel  18  using clamps or similar means while the bonding agent sets and dries. Once the bonding agent has adequately set and cured, the completed packer device can be run into a wellbore in a manner that is known in the art. 
         [0017]    It is preferred to use the system and method of the present invention with elastomers that are reactive or swell in response to wellbore fluids. With packers that incorporate such reactive or swellable elastomer, it is desired to have the packer element  10  secured to the packer mandrel  18  along substantially the entire axial length of the packer element  10  and about the entire circumference of the interface between the packer mandrel  18  and the packer element  10 . A barrier packer  20  is created that is reactive to fluids within the wellbore. 
         [0018]    In a variation of the system and method of the invention, the elastomer  10  is put on a rubber mill and cut into long strips or extruded into an uncured cylindrical pre-form  15  using a rubber extruder and appropriately formed extruder die, as is known in the art. A curing mandrel  12  is not needed for the application of uncured rubber. For the case of uncured strips of rubber, the elastomer  10  is wrapped around the desired area of the packer mandrel  18 , already prepared with an appropriate bonding agent in the manner described for the mandrel  18  below. For the case of an uncured, extruded cylindrical pre-form  15 , the uncured pre-form  15  is placed onto the surface of the packer mandrel  18 , as depicted in  FIG. 4 . It is noted that the mandrel  18  has already been prepared with an appropriate bonding agent in the same manner as for the uncured rubber strips. For the case of the extruded cylindrical pre-form  15 , the interior diameter  20  of the pre-form would to be adequately large enough to permit the pre-form  15  to easily slide over the pipe mandrel  18  to the approximate location prepared with the bonding agent without wiping the bonding agent from the surface of the mandrel  18 . 
         [0019]    Curing is then conducted upon the assembled packer assembly  22 . One currently preferred method of curing the elastomer  15 , as illustrated in  FIG. 5 , is to wrap curing wraps  26  around the uncured elastomer  15 . Curing wraps  26  are usually a film or tape, typically fashioned from nylon, with a significant shrinkage of approximately 7% to 11% that occurs during the curing process. The curing wraps  26  may be wrapped over the uncured elastomer  15  in an overlapping spiral pattern known to those familiar with rubber wrapping processes, although other suitable wrapping patterns may be used. During curing of the elastomer  15 , the curing wraps  26  shrink, which applies a significant radially-inward compressive load to the elastomer  15  that is curing underneath. A heating source, such as a band heater  28 , of a type known in the art, is then disposed over the curing wraps  26 .  FIG. 6  illustrates the packer device  22  now disposed within an annular band heater  28  to cause the elastomer  15  to be cured by applied heat. The band heater  28  is activated by a power source  30  to cure the elastomer  15 . As the uncured elastomer  15  heats up during the cure cycle, any spaces or voids will knit together and close from the vulcanization. The bonding agent will activate and begin bonding the curing elastomer  15  to the mandrel  18 . The length of the curing cycle will be determined by the thickness of the elastomer  15  being cured. Generally, the curing process requires that the elastomer be maintained at a temperature of about 300° to about 320° F. for around 1.5 hours. Heat may alternatively be applied by any of a number of known heating sources, including, for example, heating blankets similar to those used for annealing welds on large pieces, as is known in the art. Alternatively, the elastomer  10  may be cured using a specialized mobile molding unit, of a type know to those of skill in the art. Where a mobile. molding unit is used for the curing process, curing wraps  26  are not necessary to the curing process. 
         [0020]    In a related aspect, the invention contemplates preparation of the packer mandrel  18  prior to affixing the elastomer  10  thereto. The packer mandrel  18  is preferably prepared by sandblasting, grinding, or buffing with sand paper or a similar abrasive material to remove rust and scale from the outer radial surface of the packer mandrel  18 . It is then cleaned with a solvent to remove oils and other chemicals. Then, a primer and bonding agent for uncured rubber or an epoxy for the cured rubber is applied to the area. Finally, the elastomer  10  is wrapped over the mandrel  18  prior to curing. In the case of a cured piece of rubber, the rubber is wrapped over the epoxy. 
         [0021]    Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.