Abstract:
An inflatable packer or bridge plug utilized in well bores comprises a tubular elastomeric bladder that is circumferentially surrounded by flexible metallic rib elements. At opposite ends of the packer, the ribs are secured to the inside bore of respective end sleeves by welding and by non-welded bonding. The rib ends are corner bead welded to the end sleeve bore wall to overlie a circumferential undercut of the sleeve bore wall. A second, circumferential weld bead fuses an adjacent sleeve ring to the first and integrates peripheral elements of the ribs. One or more radial vents into the undercut facilitates distribution of a low temperature bonding compound such as epoxy or polyester resins or braze metal or solder. The welding procedures are carried to completion before the bonding agents are applied.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the art of well drilling and earth boring. More particularly, the invention relates to packer devices for closing annular space between well tubing and well casing or the borehole wall. 
     2. Description of Related Art 
     An inflatable packer is a downhole tool which can be inflated with well fluid to seal off the annular space between a well casing and a casing liner, for example. Alternatively, inflatable packers are used to seal the annulus between a tubing string and the inside wall surface of the casing, or the liner or the raw borehole wall. 
     The utilities for inflatable well packers are myriad. They may be used to support a column of cement above a lost circulation zone. They may also be used to isolate producing zones from cement contact. At times they are used to centralize a casing during cementing operations. Also, they may be used to isolate production zones from lost circulation zones for gravel pack operation. 
     Inflatable packers of the prior art typically provide structures for reinforcing and protecting the inflatable bladder. Most frequently, these structures take the form of woven or braided steel cable or a cladding of lapped steel ribs. In the case of braided cable reinforcement, a closed tube of braided material is secured at opposite ends to the packer end collars by a compression assembly between a pair of conical clamping surfaces in a manner similar to that disclosed by U.S. Pat. Nos. 4,191,383; 4,372,562; and 4,424,861. In some cases, the end attachment of braided reinforcement is supplemented by epoxy polymer that is injected into the braided cable interstices between the conical clamping surfaces. 
     Lapped steel ribs for packer reinforcement are secured to the respective end collars by means of a corner weld between the end-face formed by the lapped strip ends and the inside bore surface of the packer end collars. U.S. Pat. Nos. 5,143,154; 5,280,824; 5,361,479; 5,363,542; and 5,439,053 illustrate this latter type of packer reinforcement and assembly. 
     When the bladder element of a reinforced packer is expanded, the reinforcing element is at risk of structural failure. In the case of a lapped rib reinforcement, the usual point of failure is along the corner-weld bead. 
     It is an object of this invention, therefore, to strengthen the structural attachment of packer reinforcement ribs to the packer end collars. 
     Another object of the invention is to provide additional lines and means of lap rib attachment to packer end collars. 
     Also an object of the invention is the provision of structural redundancy for securing lapped rib reinforcement to a packer end collar. 
     A still further object of the invention is to double, in some cases, the force required to separate a lapped rib assembly from a packer end collar. 
     An additional object of the invention is to increase the ultimate tensile strength of the reinforcing rib assembly for an inflatable packer by distributing the load on the ribs over a larger area and thus reducing the stresses on a single weld or single line of attachment to the inflatable element sleeve. 
     SUMMARY OF THE INVENTION 
     These and other objects of the invention are accomplished by an inflatable well packer of the ribbed type in which the ribs are secured to the inside bore of the packer sleeves by a plurality of welds and by a low temperature bonding material such as an injection molded epoxy resin. 
     The packer ribs are assembled and held by a welding jig in the required end-weld position relative to a packer end sleeve. Preceding the end sleeve, in coaxial assembly over the jig held ribs, a cylindrical stress ring and a bonding ring are loosely positioned. The packer end sleeve is positioned over the jig confined ribs and the ribs are end-welded to the interior bore of the end sleeve. Next, the outer annulus of the bonding ring is positioned adjacent to the inner annulus of the of the end sleeve with a small separation gap therebetween. This separation gap is filled with one or more circumferential weld beads with care given to fuse the bonding ring and end sleeve material with the outer elements of the rib material 
     An axial length segment of the bonding ring is undercut and vented with one or more radial borings to facilitate the injection and circumferential distribution of a low temperature bonding agent such as epoxy or polyester resin around the circumference of the rib assembly. Preferably, the bonding agent is injected and cured after the fusion welding is completed. The bonding agent support may be used in conjunction with the circumferential weld bead or independently thereof. 
     If not an integral portion of the bonding ring, a stress ring is positioned coaxially over the ribs and axially against the inner end annulus of the bonding ring. Preferably, the stress ring is secured with a crimped lip. 
     With both ends of the ribs secured to the end sleeves and bonding rings, one or more outer cover segments of elastomer are either calendared onto or molded about the perimeter of the rib assembly between the end sleeves. The cover segments are bandaged and the entire assembly is heat cured. If so provided, the bonding agent may be simultaneously heat cured. 
     After completion of the rib and cover segment assembly, the inflation bladder is inserted within the rib enclosure and secured by such means as a wedge ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which like elements have been given like reference characters throughout the several figures of the drawings: 
     FIG. 1 is an axial length quarter section of a well packer incorporating the present invention; 
     FIG. 2 is an enlargement of the FIG. 1 area designated by the perimeter of enclosure A of FIG. 1; 
     FIG. 3 is a partial section of an alternative sleeve configuration; 
     FIG. 4 is an axial length quarter section of a third embodiment of the invention; and 
     FIG. 5 is a partial section of a fourth embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to drawing FIG. 1, the assembly designated generally by reference character  10  is the inflatable element of a more expansive packer assembly having similarities to that of U.S. Pat. No. 4,372,562. In particular, the inflatable element  10  concentrically overlies a cylindrical or tubular mandrel having a central, fluid carrier bore axially through the packer assembly. In particular, the inflatable element provides a fluid tight seal between the mandrel and opposite ends of the inflatable element. 
     Opposite ends of the inflatable element  10  comprise the axial alignment of an inner sleeve  12 , and outer ring  14  and a stress ring  16 . Adjacent annular ends of the inner sleeve  12  and the outer ring  14  are beveled to facilitate joinder of the ends by a circumferential weld bead  24 . The opposite end of outer ring  14  is machined to provide a circumferential lip  29  that is rolled, peened or crimped into the crimp channel  25  around the outer perimeter of the stress ring  25 . 
     The internal bore wall of the outer ring  14  includes a circumferential undercut  26  as shown by FIG.  2 . The undercut is ported by one or more injection apertures  28 . 
     Secured to the internal bore of the inner sleeve  12  by means of a corner or filet weld  22  is a cylindrical assembly  20  of lapped, stainless steel ribs. The outer circumferential elements of the lapped ribs lie adjacent to the internal bore walls of the outer ring  14  as well as the stress ring  16  and thereby span across the undercut  26  in the outer ring  14  and the weld bead  24 . The weld bead  24  fuses the outer perimeter elements of the ribs  20  with the end elements of the inner sleeve  12  and the outer ring  14  thereby integrating the sleeve  12  and ring  14  into a singular end sleeve unit. 
     A low temperature bonding agent secures the outer perimeter elements of the ribs  20  to the outer ring  14  across the undercut  26 . Preferably, such a low temperature bonding agent is a polymer resin such as an epoxy or polyester compound that may be injected into the undercut  26  through the port(s)  28 . However, some applications may find greater utility for a braze metal or high-strength solder. Each of these low temperature bonding agents have distinctive properties and useful applications as are well known to the art. The phrase “low temperature bonding agent” is used to distinguish the physical characteristics of a weld that fuses and mixes the base metals of a joint from those of a superficial adhesion or molecular interface bonding. 
     After the ribs  20  are secured to the integrated sleeve and stress ring  16 , the elastomer bladder  30  is positioned within the internal rib tube and secured at respectively opposite ends by wedge rings  32 . These rings  32  have a conical end face  33  and threaded serrations  34  around the outer perimeter. The wedge rings  32  are pressed into the sleeve bore to compress the tubular ends of the elastomer bladder  30  against the smoothed corner weld bead  22 . A locking ring  36  is turned on threads  38  into the outer face of the wedge ring  32  to secure and maintain the compressive force on the bladder  30 . 
     The outer perimeter of the lapped rib assembly  20  is girdled by one or more outer covers  40  of elastomer material such as natural or nitrile rubber. When the bladder  30  is expanded, these outer covers provide the contact interface to seal the packer structure to the surrounding wall. 
     The individual rib elements  20  are preferably fabricated of a high tensile strength steel. A stainless steel composition is a further fabrication preference. After forming, shaping and if required, heat treating, the individual rib elements are surface distressed as by sandblasting or knurling for example for the purpose of promoting a bonded interface with the low temperature bonding agent used in the undercut. The outer ring  14  may also be surface distressed at and along the sleeve undercut  26  and other locations corresponding to the low temperature bonding agent. 
     After the assembly preparation, the individual rib elements are brought together in an assembly jig and held at the required tubular position while the stress rings  16  and outer rings  14  are positioned loosely over the tube ends. Next, an inner sleeve  12  is positioned over the respective tube ends and the ends of the ribs are welded to the inside bore wall with a corner weld  22 . 
     The outer ring  14  is then positioned end-to-end with the sleeve  12 . Depending on many variables, a gap of about ⅛ in., for example, may be set between the adjacent ends. Between the adjacent sleeve and ring ends, a circumferential weld bead  24  is laid in one or more weld passes. The first of these passes is set fuse elements of the ribs  20  into the bead that includes the sleeve  12  and ring  14  edges. 
     When the welding procedures have been completed, the desired low temperature bonding agent is applied between the ribs  20  and the outer ring  14 . In the case of a polymer resin such as epoxy or polyester, the compound may be injected through the injection port  28  into the under cut  26  for distribution around the rib tube  20  perimeter. The resin may be a catalyst cured or, if desired, heat cured in cooperation with the preparation of the outer covers  40 . 
     Alternatively, the low temperature bonding agent may be braze metal or silver solder and preapplied to the undercut. After the rib assembly  20  is in place, the low temperature flow metal is heated conductively through the outer ring  14  and caused to flow between the lapped ribs. In another example, the braze or solder may be caused to flow through the aperture  28  for distribution around the rib tube. 
     Following placement of the low temperature bonding agent, the stress ring  16  is positioned adjacent to the inner edge of the ring  14  and under the crimp lip  29 . Here, the lip  29  is either crimped, peened or rolled into the crimp channel  25  to unitize the stress ring with the sleeve. 
     The outer covers  40  are next fabricated by a wrapped layup of rubber or other suitable polymer or by an injection mold of such material. The rough mold or layup is then tightly wrapped (bandaged) with a binder fabric such as nylon and heat cured. The curing procedure may also include the polymer resin that was used between the ribs  20  and the outer ring  14 . When the curing step is complete, the bandaging is removed and the outer covers are dimensionally sized. 
     At this point, the premolded bladder tube  30  is inserted through the ribbed tube  20  and the wedge ring  34  pressed into compressed position against the corner weld bead  22 . Finally, the lock ring  36  is turned over internal threads  38  to secure the assembly. 
     Tests conducted on several permutations of the invention include those for ultimate tensile load to provide a strength comparison baseline. These tests included a tube of  80  ribs that were secured at opposite ends to respective end sleeves by corner welds between the rib ends and an internal bore of each sleeve. The sleeve material was  1030  carbon steel. The ribs were 0.015 in. thick×0.750 in. wide×16.00 in. long and of 301 stainless steel material. The rib tube layup mandrel had a 2.362 in. o.d. The average ultimate load sustained by the test examples was 64,000 pounds. 
     Additional test examples were fabricated in conformance with those above except that the sleeve bores were undercut and injected with epoxy resin. Rib tubes respective to the test examples were secure to the sleeves by both end welding and by epoxy bonding. The average tensile loads sustained by these examples was 110,000 pounds: an increase of 72% over the baseline configuration. 
     A second baseline configuration was constructed having 130 stainless steel ribs distributed around a 3.000 in. o.d. layup mandrel. The rib tube was end welded to carbon steel sleeves. The ribs were 0.020 in. thick, 1.000 in. wide and 16.00 in. long. The average ultimate load sustained by this baseline configuration was 237,500 pounds. A modification of this second baseline configuration additionally included one circumferential weld bead about the rib tube o.d. The modified test specimen sustained an average ultimate load of 332,500 pounds: an increase of 40% over the baseline configuration. 
     The FIG. 3 invention embodiment includes two supplemental sleeve rings  42  and  44  between the inner sleeve  12  and the stress ring  16 . In this case, the inner sleeve  12  is corner welded to the rib tube  20  outside perimeter with a first tube O.D. bead  50 . This first tube O.D. weld  50  is additional to the traditional rib end bead  22 . 
     Thereafter, the first outer ring  42  is positioned and secure to the inner sleeve  12  with a first sleeve O.D. bead  52 . 
     Next, the second rib tube O.D. bead  54  is applied followed by a second sleeve O.D. bead  56  that secures the second outer ring  44  to the first outer ring  42 . In this example, the stress ring  16  is secured to the second outer ring  44  in a manner corresponding to that of FIG.  2 . It will be understood, however, that the stress ring  16  may be secured by means of a weld bead if desired. 
     A third embodiment of the invention, illustrated by FIG. 4, incorporates an integral or single piece sleeve  62  having a stress relieving end nose  69 . This third embodiment includes no welded connection between the rib tube and the sleeve  62 . Instead, the rib tube end is welded to an independent collar  64  and the sleeve and collar are coaxially engaged mechanically against respective abutment faces. The internal bore of the sleeve includes a counterbored inside step-face  68 . The reinforcing rib tube  20  is end-welded with a bead  66  to the end of the rib collar piece  64 . The rib collar  64  includes an outside step-face  65  that mechanically engages the inside step-face  68  of the sleeve. If desired, a low temperature bonding agent may be applied to the inside bore wall of the sleeve  62  and /or the outside perimeter of the rib tube  20  prior to coaxial assembly and induced to flow together after assembly by heat or capillary force. 
     The fourth invention embodiment of FIG. 5 also includes a single piece sleeve  82  in which the internal bore is undercut with a cavity  86 . The cavity is ported by injection apertures  88  for insertion of a low temperature bonding agent as previously described. As with the FIG. 4 embodiment, the ribs  20  are end-welded by a bead  66  to a collar  64  that mechanically interlocks with mutual engaging step-faces  65  and  68 . Following coaxial assembly, the cavity  86  is injected with epoxy resin, for example. 
     Although our invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent of those of ordinary skill in the art in view of the disclosure,. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention