Patent Publication Number: US-2016245038-A1

Title: Swellable Seal with Backup

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase Application under 35 U.S.C. §371 and claims the benefit of priority to International Application Serial No. PCT/US2013/068776, filed on Nov. 6, 2013, the contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to well tools that utilize swellable seals. 
     Downhole conditions in a well present numerous sealing challenges. For example, seals in a well must often withstand extended exposure to high pressures and temperature. In such conditions, commonly used elastomer seals tend to extrude into the gap between the component carrying the seal and the surface sealed against, and ultimately fail. Complex backup ring designs have been developed to address this problem, by bridging the gap and supporting the extrusion against extrusion. However, the backup ring designs are actuated only when the seals are pressurized. Also, in the context of a stinger or stab, where one well component is sealed in a bore of another well component, multiple seals and thus multiple backup rings are used. To accommodate the multiple seals in a small space, O-rings or chevron seals are used. However, the effectiveness of such seals is dependent to the cleanliness and surface finish of the surface sealed against. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic side view of a well incorporating a tubing string. 
         FIG. 2  is an side cross-sectional view of an example of two well components incoporporating a sealing assembly. 
         FIGS. 3A and 3B  are detail views of the example well components, showing an end of the sealing assembly prior to the seal swelling and after the seal has swelled. 
         FIG. 4  is a perspective view of an example backup member showing the undulations. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Referring first to  FIG. 1 , a well includes a substantially cylindrical wellbore  10  that extends from a wellhead  22  at the surface  12  downward into the Earth into one or more subterranean zones of interest  14  (one shown). The subterranean zone  14  can corresponding to a single formation, a portion of a formation, or more than one formulation accessed by the well, and a given well can access one or more than one subterranean zone  14 . In certain instances, the formations of the subterranean zone are hydrocarbon bearing, such as oil and/or gas deposits, and the well will be used in producing the hydrocarbons and/or used in aiding production of the hydrocarbons from another well (e.g., as an injection or observation well). The concepts herein, however, are applicable to virtually any type of well. A portion of the wellbore  10  extending from the wellhead  22  to the subterranean zone  14  is lined with lengths of tubing, called casing  16 . 
     The depicted well is a vertical well, extending substantially vertically from the surface  12  to the subterranean zone  14 . The concepts herein, however, are applicable to many other different configurations of wells, including horizontal, slanted or otherwise deviated wells, and multilateral wells. 
     A tubing string  18  is shown as having been lowered from the surface  12  into the wellbore  10 . The tubing string  18  is a series of jointed lengths of tubing coupled together end-to-end and/or a continuous (i.e., not jointed) coiled tubing, and includes one or more well tools (e.g., one shown, well tool  20 ). The string  18  has an interior, center bore that enables communication of fluid between the wellhead  22  and locations downhole (e.g., the subterranean zone  14  and/or other locations). In other instances, the string  18  can be arranged such that it does not extend from the surface  12 , but rather depends into the well on a wire, such as a slickline, wireline, e-line and/or other wire. 
     The concepts herein apply to a sealing arrangement that can be used in a number of different contexts to seal between well components in a well. For example, the sealing arrangement can be used in the well tool  20 . In certain instances, the well tool  20  is of a type having an inner tubing component nested in an outer tubing component, with the sealing arrangement described herein configured to seal between the tubings. The sealing arrangement, however, need not be limited to sealing components of the same tool or device. For example, in certain instances, the well tool  20  is a packer type tool (e.g., packer, bridge plug, frac plug and/or other) that has the sealing arrangement configured to seal the tool  20  to the inner surface of the casing  16 , a liner or other component in the well to seal the annulus around the tubing string  18 . In another example, the tubing string  18  can be placed in the well in two parts, with an uphole component that has a stab or stinger that is received into a corresponding bore of the downhole component. In this instance, the sealing arrangement is configured to seal to the bore of the other component, and thus seal between the two tubings. In yet another example, a running tool or actuating tool can be used to operate the well tool  20  or another component in the well. In this instances, the running or actuating tool has a stinger or stab that is received into a corresponding bore of the tool or device being actuated, and the sealing arrangement is configured to seal between the stinger/stab and bore. Other examples exist and are within the concepts herein. 
     Referring to  FIG. 2 , two well components  30 ,  32  are shown in a half side cross-sectional view. In the present example, the well components  30 ,  32  are two elongate tubings (e.g., tubings of a well tool, a packer and casing, a stinger and bore, or other), concentrically nested within each other. The inner tubing (component  32 ) includes a seal groove  24  sized to receive an elongate swellable elastomer seal  26  and backup members  28 . Each of the seal groove  24 , swellable seal  26  and backup members  28  are annular or ring shaped to encircle the tubular well components  30 ,  32 . An annular gap  34  is formed between the well components  30 ,  32 . Although described herein in connection with tubular well components, the same concepts could be applied to non-cylindrical, flat or other shapes. Thus, the seal  26 , backup members  28  and other aspects need not be annular. 
     The elongate swellable elastomer seal  26  is made from a swellable elastomer that swells or expands on contact with a specified fluid, e.g., oil, water, and/or other. Notably, the swellable elastomer swells in all directions uniformly, unless constrained. Therefore, in the example with the annular swellable elastomer seal  26  in the seal groove  24 , the seal  26  swells radially outward, as well as axially within the groove  24 , parallel to centerline of the well components  30 ,  32 . The seal  26  is elongate in that it axial dimension is longer than its radial dimension, but other configurations of seal  26  could be provided. In certain instances, the radial dimension of the seal  26  is selected to provide a gap with the component  30  to allow the seal  26  (and component  32 ) to be inserted and withdrawn from component  30 . 
     A backup member  28  is provided at each end of the seal  26 , axially between the seal  26  and opposing axial ends of the seal groove  24 . In other instances, only one backup member  28  is provided. The backup member  28  is a wave backup member made as a wave spring, or configured similarly to a wave spring, with one or more axial undulations  36  distributed around the backup member  28 . In certain instances, the undulations can be distributed evenly around the backup member  28 , for example, as in  FIG. 4  showing four undulations  36  distributed at 90° from each other. Although shown as smooth, curving sine wave like undulations  36 , the undulations could be more abrupt and/or a different shape. The backup member  28  is constructed of a thin, flat material with parallel sidewall surfaces, and the undulations  36  are configured so that when the member  28  is axially compressed toward flat, they expand the backup member  28  circumferentially, and correspondingly radially outward. In certain instances, the backup member  28  can be sized to lightly contact or provide a gap with the component  30  in an unexpanded (not axially compressed) free state. Such a configuration allows the backup member  28  to slide axially through the component  30  without much or any resistance, allowing the component  32  to be inserted and withdrawn into the component  30 . The number and amplitude A of the undulations  36  can be selected so that when the backup member  28  is compressed, it bridges the gap  34  and abuts and presses on the component  30 . The number of undulations  36  and the amplitude A of the undulations can be selected to provide a contact pressure against the component  30  to provide an adequate degree of backup that prevents the swellable seal  26  from extruding through gap  34 . In certain instances, the backup member  28  is provided with a chamfer  38  on its inner diameter oriented toward the seal  26  to facilitate the member  28  expanding and centering on the seal  26 . 
     The backup member  28  can be constructed of a number of different materials. In certain instances, the member  28  can be constructed of a material having a higher hardness and/or yield strength than the elastomer of the swellable seal  26  to facilitate the backup member  28  providing an effective backup. In certain instances, the material is selected based on its ability to survive the high, downhole temperatures. Some example materials for the backup member include metal, polymer, composite and/or other materials or mixes of materials. 
     In operation, with the components  30 ,  32  residing in the well and the backup members  28  and seal  26  residing in the seal groove  24 , the swellable seal  26  is contacted with the specified fluid. The seal  26  responds by swelling into contact and sealing to the component  30 . In certain instances, the seal formed by the seal  26  is gas tight.  FIG. 3A  is a detail view about the axial end of the seal groove  24 , showing the swellable elastomer seal  26  prior to swelling and the backup  28  unexpanded. When the swellable elastomer seal  26  is in contact with the specified fluid, it swells and expands both radially and axially. In axially expanding, the swellable elastomer seal  26  compresses the backup members  28  against the axial end wall of the seal groove  24 . The undulations of the backup members  28  axially compress, and cause the backup members  28  to expand radially into abutting contact with the component  30 , as shown in  FIG. 3B . Then, as the seal  26  begins to hold a pressure differential, the seal  26  is supported against extrusion through the gap  34  by the low pressure side backup member  28  pressing against the component  30 . By providing two backup members  28 , the pressure differential can be reversed and the opposing backup member  28  will support the seal  26  against extrusion through the gap  34 . 
     Notably, by using a swellable elastomer seal  26 , the surface finish of the surface sealed against on the component  30  need not be tightly controlled, as the swellable seal  26  provides a contact pressure that facilitates sealing rougher surfaces than non-swelling seals. In the context of a stinger or stab, the component  30  need not be provided with a polished bore receptacle. Also, the seal  26  can provie more surface area for sealing than a conventional O-ring or chevron seal. In certain instances, the greater surface area and/or the contact pressure from swelling will allow the swellable seal  26  to seal, even if damaged. Because the seal  26  swells in contact with fluid, a pressure differential is not necessary to achieve a seal or to actuate the backup members  28  into supporting the seal  26 . The swelling also facilitates insertion of the component  32  into component  30 , because the seal  26  need not contact component  30  until in contact with the specified fluid. Once sealing, the seal  26  resists withdrawal of the component  32  from component  30 . In certain instances, because of the simplicity of the backup members  28 , the cost to manufacture can be less than other more complex backups and chevron seals. 
     A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims.