Patent Publication Number: US-4544165-A

Title: Inflatable packer

Description:
This invention relates to inflatable packers generally, and in particular to inflatable packers that employ a sheath of individual overlapping strips of metal as reinforcing for the packer. 
     Inflatable packers generally include two annular packer heads mounted on a mandrel with at least one of the packer heads being free to move toward the other one as the packer is inflated. The packer consists of an inner sleeve of resilient material and an outer sleeve of elastomeric material. The reinforcing required to support the outer sleeve when the packer is set and subjected to a differential pressure is located between the sleeves. The sleeves and the reinforcing are attached to the packer heads in some manner. 
     Various ways have been used to attach the ends of individual reinforcing members to the packer heads. For example, see U.S. Pat. No. 3,837,947 entitled &#34;Method of Forming an Inflatable Member&#34;, which issued Sept. 24, 1974. This patent uses an adhesive mixture to bond the reinforcing members to the packer heads. Usually, however, the ends of each member is welded to the packer heads. In either case, great care must be exercised to see that the reinforcing members are positioned uniformly in the desired overlapping position, and is, therefore, time consuming and expensive. 
     In addition, with inflatable packers that are used in operations requiring the temporary sealing of the annulus of a well bore, such as drill stem testing operations, when the outer or inner sheath has failed or appears to be on the verge of failing, the packers are sent back to the shop for salvage. Usually, the reinforcing members are not reused, but the packer heads are. Where the reinforcing members are welded or otherwise bonded to the packer heads as was previously done, this makes the disassembly of the packer heads and the reinforcing members very expensive and even impractical in some cases. 
     Therefore, it is an object of this invention to provide an inflatable packer having a plurality of elongated members of resilient material arranged in side-by-side overlapping position to form a sheath to reinforce the sleeves of elastomeric material of the packer in which the ends of the reinforcing members are anchored to the packer heads by a mechanical lock arrangement that does not require the individual reinforcing members to be welded or otherwise bonded to the packer heads. As a result the packer heads and the reinforcing members can be quickly and easily disassembled by releasing the mechanical lock. 
     It is a further object of this invention to provide an inflatable packer in which each individual reinforcing member has a bend adjacent its ends along lines that make an angle with the longitudinal axis of the reinforcing member to allow the reinforcing members to overlap with their ends in alignment and to be held against movement relative to the packer heads by clamping the packer heads to the bend in the members. 
     It is another feature and object of this invention to provide reinforcing members that are self spacing in that they will move to a uniform spacing under the clamping force of the retaining sleeve. 
     It is a further object and feature of this invention to provide an inflatable packer having a plurality of individual reinforcing members of resilient material in overlapping position to form a reinforcing sheath with each reinforcing member having a strip of elastomeric material that is bonded to the inner edge of the member to engage the adjacent overlapping reinforcing member and prevent the inner sleeve from being extruded into the space between the reinforcing members when the inner sleeve is subjected to the pressure required to cause the members to bend outwardly and set the packer. 
     These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached drawings and appended claims. 
    
    
     In the drawings: 
     FIG. 1 is a view partly in elevation and partly in section of an inflatable packer with the ends of the reinforcing members of the packer anchored to the packer head in accordance with the preferred embodiment of this invention; 
     FIG. 2 is a view similar to FIG. 1 showing the packer inflated sealing the annulus between a pipe string and a well bore; 
     FIG. 3 is a view partially in section and partially in elevation of the upper end of the packer of FIG. 1 on an enlarged scale; 
     FIG. 4 is a sectional view taken along line 4--4 of FIG. 3; 
     FIG. 5 is a side view of a reinforcing member constructed in accordance with this invention; 
     FIG. 6 is a plan view of the reinforcing member of FIG. 5 showing its relationship with adjacent reinforcing members when they are arranged in overlapping position; and 
     FIG. 7 is a sectional view of the inner and outer sleeves of an inflatable packer material with an alternate embodiment of reinforcing members located between the sleeves. 
    
    
     The packer includes upper annular packer head 10 and lower annular packer head 11. Each packer head is an assembly of several pieces. The packer includes tubular mandrel 12, which is connected to upper packer head 10 by threads 14. The mandrel is not connected to lower packer head 11 but extends through it. In this way, the lower head can move upwardly toward the upper head when the packer is inflated, as shown in FIG. 2. The lower end of mandrel 12 is connected to and supports whatever pipe or equipment is located below the packer in the conventional manner. 
     The packer also includes inner sleeve 16 of elastomeric material and outer sleeve 18 also of elastomeric material. Located between the inner and outer sleeves of elastomeric material is a sheath of reinforcing members, indicated generally by the number 20. The ends of the two sleeves and the reinforcing members are all bonded, attached, or otherwise connected to packer heads 10 and 11. The manner in which the reinforcing members are attached will be described first. 
     In accordance with this invention, each reinforcing member, such as member 20a in FIG. 5, has a bend in it adjacent each end that in effect, moves end portions 22 and 24 of the reinforcing member into a plane that is parallel to but spaced from the plane of center section 26. Each bend is made along two parallel bend lines that are not perpendicular to the longitudinal axis of the reinforcing member. For example, bend 21 occurs along bend lines A and B, as shown in FIG. 6, and bend 23 is made along lines C and D. In the embodiment shown, the two sections of the member between the bend lines, i.e. the bent sections, make approximately a 45° angle with end sections 22 and 24 and center section 26. By having bend lines A, B, C, and D, at an acute angle to the longitudinal axis of the member, the members can be overlapped as shown in FIG. 6, while maintaining their ends in alignment. The angle of the bend is selected for the particular overlap desired and is also a function of the width and thickness of the member. 
     The structure for clamping the upper and lower packer heads to the end of the reinforcing members is the same so the method of assembly of only the upper packer head with the reinforcing members will be described in detail. 
     To assemble the upper packer head and the reinforcing members, as shown in FIGS. 3 and 4, the reinforcing members are arranged in a circle and loosely held by an O-ring or the like in overlapping position on a tubular support member of approximately the desired inside diameter of the sheath of reinforcing members. The ends of the reinforcing members are not supported by the mandrel so the ends of the members can be moved inwardly to allow outer anchor sleeve 30 to be slipped over the ends of the reinforcing members until internal cavity 34 of the anchor member is positioned over the end portions of the reinforcing members. The end wall of cavity 34 adjacent the bent sections of the members is inclined at about 45° to provide shoulder 38 that engages the bent sections. 
     To hold the ends of the reinforcing members in the cavity, portion 42a of inner anchor sleeve 42 is positioned inside the sheath opposite the cavity. The diameter of the cavity in outside anchor 30 and the outside diameter of portion 42a of sleeve 42 preferably are such that they will tightly engage the inside and outside surfaces of the reinforcing members. 
     The end of portion 42a of the inner anchor sleeve has beveled shoulder 46 at approximately the same angle as the bent sections of the reinforcing members to trap the bent sections between shoulder 38 and 46. 
     To move these shoulders together and into snug engagement with the bent portions of the reinforcing members, outside anchor sleeve 30 is internally threaded on its upper end. Threaded split ring 48 is used to force the outside anchor sleeve upwardly, as viewed in FIG. 3, and the inside anchor sleeve downwardly to force shoulders 38 and 46 respectively into firm engagement with the bent sections of the reinforcing members. At this time, as the sleeves start exerting force on the bent sections, the reinforcing members will move so that the clamping force exerted by the anchor sleeves will be substantially equally distributed among the individual reinforcing members. As a result, they will self-align themselves to have substantially the same overlap throughout the sheath. This occurs, as can be seen in FIG. 6, because as shoulder 38, which is indicated by a dotted line moves into engagement with the reinforcing members, they will be forced to adjust their position until the shoulder engages each member at the same point, which, in the example shown in FIG. 6, is the right hand edge of the members indicated by the letter E. The reinforcing members appear flat in FIGS. 5 and 6, but, preferably they are slightly curved in cross section, as shown in FIGS. 3 and 4. 
     The assembly of the upper packer head is completed by tapered pipe plug 49 that is made up in threads located in the split in ring 48 to expand the ring and force it into firm engagement with the internal threads on the outer anchor sleeve. Threaded sub 60 is connected to the outer anchor sleeve to support the packer through the internal threads provided on the anchor sleeve. Threaded sub 60 also provides the threads for connecting mandrel 12 into the pipe string and supporting it. 
     To complete the assembly of the packer after the packer head is clamped to the other end of the sheath of reinforcing members, inner sleeve 16 is positioned inside of the sheath of reinforcing members and anchored at each end in internal grooves 50 and 52 on the inside of inner anchor members 42 and 44 of the upper and lower packer heads. The sleeve is held in these grooves by expanded metal rings 54 and 56. Outer sleeve 18 is molded in place on the outside of the packer at which time it is bonded at each end to outer anchor sleeves 30 and 32 and to the reinforcing members. 
     Preferably, bends 21 and 23 should be in the opposite direction so that any turning moment caused by the force exerted by shoulder 38 at points E will be opposite to the turning moment imposed at points F by shoulder 40 of the lower head. 
     When the packer is inflated there is often a substantial pressure differential between the inside and outside of the packer. This pressure differential tends to force the elastomeric material of the inner sleeve into the openings that may exist between adjacent reinforcing members. The members will not move to a position where they do not continue to overlap, but they will, of course, move to where they are not overlapping as much and there can be cracks and openings between the members into which the elastomeric material of the inner sleeve can be extruded. When this occurs, it damages the inner sleeve and can reduce its useful life rapidly. 
     It is another feature of this invention to attach to the inner edge of each reinforcing member as shown in FIG. 7, strips 66a, 66b, and 66c of elastomeric material that are attached to overlapping reinforcing members 68a, 68b, and 68c. When the packer is inflated, inner sleeve 70 will engage the reinforcing members and also the elastomeric strips and force them into firm sealing engagement with the adjacent reinforcing member and keep the inner sleeve from being extruded into the space between the reinforcing members. 
     From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages that are obvious and that are inherent to the apparatus and structure. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
     Because many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.