Field of the Invention

[0001] This invention relates to expandable packers for use in oil and gas well and the like. In particular, the invention provides a packer structure that can reduce problems with extrusion of elastomeric material by the packer when expanded in a well, and that allows packers to be contracted for movement to other locations.

Background and Prior Art

[0002] Packers are devices that can be run into wells in a contracted state (relatively smaller outer diameter) and then activated to cause the packer element to expand (relatively larger outer diameter) to seal against the wall of the well and provide a fluid barrier. In the type of packer to which the invention relates, the packer element is in the form of an elastomeric sleeve mounted on a tool body. The packer element is caused to expand radially by squeezing it axially, typically by means of a slickline activated setting tool including an arrangement of sliding mandrels. Such devices can be retrievable or permanent set devices, such as retrievable packers, bridge plugs, straddle packers, shut-in tools and the like. GB2467040 and US2850101 disclose embodiments of packers.

[0003] Expansion packers of this type suffer from a number of potential problems in use. One such problem is extrusion of the elastomeric material. If there is space between the end plate and the wall of the well, the elastomeric of the packer element can extrude through this space due to the differential pressure across the packer element. US7290603 proposes one solution to extrusion of the packer element by providing circumferential rings of overlapping seal elements at either end of the packer element. As the packer element is compressed between pressure rings having an inclined surface against which the rings of seal elements are urged, the overlapping parts of the seal elements slide over each other to allow the diameter of the ring to expand until the ring of elements contacts the wall of the borehole to provide a barrier to extrusion of the packer element. The seal elements are mounted on spring which lie in grooves formed in the outer surface of the tool above and below the packer element.

[0004] The tool described in US7290603 suffers from a number of problems. Although the seal elements are provided with overlapping regions to present a continuous ring extrusion barrier, there are still spaces through which packer material can extrude. Furthermore, the grooves in which the springs mounting the seal elements are situated can become blocked with debris, preventing smooth operation of the seal elements.

[0005] Other problems can arise with expandable packers due to permanent or semipermanent deformation of the packer elastomer. The particular properties of the elastomer used for the packer element can be selected to provide the necessary physical behavior of the packer. Elastomers suitable for use in high temperatures, or in the presence of severe levels of H2S (for example, up to 50%) or C02 (for example, up to 15%) are often unsuitable for use as expandable packers, suffering from excessive extrusion in known packer tool construction. Elastomers that can provide sufficient physical properties without excessive extrusion, can suffer from problems of permanent deformation preventing effective release when it comes time to remove the packer. Chemical curing, compression set and explosive decompression can cause permanent or semi-permanent deformation of the packer element that can led to difficulty in retrieving the packer through restrictions in the well. Even though elastomers can be found that have good properties for chemical curing and compression set, problems can still arise due to rapid decompression caused by sudden pressure drops in the well. To deal with this problem, mechanical pulling systems can be provided that pull the expansion element axially so as to reduce its outer diameter when it is time to remove the packer from its deployed position.

[0006] This invention proposes solutions to problems discussed above, providing an effective expandable sealing ring to address extrusion, and a pulling mechanism to aid unsetting.

Summary of the Invention

[0007] A first aspect of the invention provides an expandable packer tool comprising: a mandrel tool body; a sleeve-like packer element mounted on the tool body; a setting mechanism that is operable to axially compress the packer element such that the diameter of the packer element in its compressed state is increased compared to it uncompressed state; and a ring of seal elements disposed around the tool body on either side of the packer element, and arranged to engage the packer element so that expansion of the packer element causes the ring of seal elements to expand in a corresponding manner so as to form an extrusion barrier; wherein the ring of seal elements comprises wedge-shaped seal members comprising first seal members having a inner base wider than an outer surface, and second seal members having an inner base narrower than an outer surface, the ring comprising alternating first and second members, the inclined faces of each wedge-shaped member engaging the corresponding faces of adjacent members.

[0008] The first and second seal members can have curved outer surfaces such that when the ring is in its expanded condition, the ring has a substantially circular outer surface.

[0009] The first and second seal members can also have substantially flat axial faces.

[0010] Each seal member can be located at one end of a mounting arm that is pivotally connected to the tool body at its other end. A sleeve can be provided around the outside of the mounting arms.

[0011] The inclined surfaces of the first seal members can be arranged to act on the corresponding surfaces of the second seal members to urge them outwards when the packer element is compressed; and the inclined surfaces of the second seal members can be arranged to act on the corresponding surfaces of the first seal members to urge them inwards when the packer element is uncompressed. The second seal members can be normally biased radially inwardly.

[0012] When the packer element has a conical end surface, the seal members can be provided with an inclined inner face that engages on the conical end surface such that urging the seal members and the packer element together causes the seal members to be urged radially outwardly.

[0013] The packer element can comprise a cut-out in its inner surface near at least one end; and the setting mechanism comprises an inner mandrel that has an outward projection that engages in the cut-out so that the inner mandrel can exert a pulling force on the packer element.

[0014] The cut-out can be in the form of a circumferential groove and the outward projection is in the form of a circumferential rim.

[0015] A second aspect of the invention provides an expandable packer tool comprising: a mandrel tool body; a sleeve-like packer element mounted on the tool body; and a setting mechanism that is operable to axially compress the packer element such that the diameter of the packer element in its compressed state is increased compared to it uncompressed state; wherein the packer element comprises a cut-out in its inner surface near at least one end; and the setting mechanism comprises an inner mandrel that has an outward projection that engages in the cut-out so that the inner mandrel can exert a pulling force on the packer element.

[0016] These and further aspects of the tool will be described in more detail below.

Brief Description of the Drawings

[0018] Figure 1 shows a part sectioned view of a tool according to the invention;

Figure 2 shows a more detailed view of part of the tool of Figure 1;

Figure 3 shows an end view of the ring of seal elements when the packer is in an uncompressed state;

Figure 4 shows the ring of seal elements when the packer is in an expanded state; Figure 5 shows an partial view of the tool in an uncompressed state; Figure 6 shows a partial view of the tool in an expanded state; and Figure 7 shows a detailed view of part of Figure 6. Detailed Description

[0019] The tool shown in Figure 1 comprises a central mandrel 10 on which the various functional components of the tool are mounted. An elastomeric packer element 12 in the form of a sleeve is positioned around the mandrel 10. A packer sleeve 14 is located around the central mandrel 10 and acts on the packer element 12 to compress the element to expand its outer diameter to seal against the wall of the well. Retrieving rings 16 are positioned around the outer surface of the tool to the side of the packer elementl2. Rings of seal elements 18 are positioned on either side of the packer element 12 to act as an extrusion barrier when deployed.

[0020] Figure 2 shows a more detailed section of part of the tool shown in Figure 1 (with parts omitted for clarity). The end of the packer element 20 is provided with a conical surface 22. This can either be provided directly on the packer element itself, as shown, or as part of a separate structure such as a metal ring connected to the end of the element 20. The inner edge of the packer element 22 is provided with a cut-out in the form of an inward-facing circumferential groove 24. A retraction member is provided within the tool body in the form of an inner sleeve 26 that has an outwardly-directed circumferential rim 28 that engages in the groove 24. The retraction member 26 allows an axial pull to be applied to the packer element 20 so as to cause it to retract when the packer is unset. This can be sufficient to counteract the effect of permanent set or deformation due to chemical curing compression set or explosive decompression effects so that the packer returns to a sufficiently small outer diameter to pass through and restrictions in the well.

[0021] A series of arms 30 are pivotally connected to the tool body at one end 32 and carry seal members 34 at the other end. The seal members 34 are described in more detail below. Each seal member 34 has an inclined end face 36 that bears against the conical surface 22. A protective collar 38 is positioned around the arms 30 to limit ingress of debris which might otherwise affect functioning of the device.

[0022] The seal members 34 are provided in two wedge-shaped forms, a first, inner wedge 34a that has a base wider than its upper end, and a second, outer wedge 34b that has a base narrower than it upper end. The side faces 40 of each wedge are substantially flat, and the upper surfaces 42 are curved such that when all of the members are positioned with their outer surfaces aligned (see Figure 4), a substantially continuous, circular circumferential surface is formed.

[0023] When the tool is in its unexpanded state, the inner wedges are retracted radially inwardly so that the upper ends 42 of the inner wedges 34a lie below those of the outer wedges 34b (see Figures 3 and 5). In this case, the outer diameter of the ring is substantially the same as that of the unexpanded packer element (see Figure 5). As the packer is set, the inclined faces 36 of the seal members 34 are urged against the conical surface 22 of the packer element 20. This causes the inner wedges 34a to be forced radially outwards, the inclined surfaces of the inner wedges 34a acting on the corresponding faces of the outer wedges 34b, similarly forcing them outwards and apart until the outer surfaces of the wedges form a circular surface adjacent the wall of the well.

[0024] The flat side faces provide a substantially continuous extrusion barrier (Figures 4, 6 and 7). The outer wedges 34b can be normally biased in the contracted position (Figure 3) so that releasing the set on the packer allows the tool to retract to the unexpanded state, the inclined surfaces of the outer wedges acting on the corresponding surfaces of the inner wedges to force them inwardly and contract the diameter of the ring.

[0025] The wedges 34 can be provided with radiussed edges to limit the potential for damage to the packer member. The flat side faces of the seal elements also limit the axial and radial stress on the arms when in the expanded position and contacting the wall of the well.

[0026] This invention provides an expandable support system for a retrievable bridge plug and packer system that can be made suitable for use in high H ₂ S applications and high temperature applications. The particular elastomer for use with the packer can be selected according to requirements. However, it will be appreciated that its use is not restricted to such applications and can be applied in any well environment.

[0027] The system has two aspects, one being the expandable seal ring which can help prevent extrusion of the elastomer in hostile conditions and the other being a related attachment of the packer element to the tool body which enables the packer to be stretched when retracted and therefore makes the recovery of the tool easier.

[0028] Because the pivoting arm mechanism is relatively simple and also closed, debris problems can be reduced. The wedges provide an essentially continuous metal face that avoids problems associated with the profiled shape of the prior art tool extrusion barrier.

[0029] The fact that the front and rear faces of the expanding extrusion ring can be flat means that there can be no axial force exerted down the length of the arms of the extrusion ring. This not only simplifies the design and minimizes the components but also ensures that the axial force can be transmitted directly across the head of the segment sandwiched between a steel insert in the packer and the body of the tool. The retraction of the arms can therefore driven directly by this axial load (rather than a secondary spring) which forces the fingers down and under the outermost retrieving tube.

[0030] From the point of view of the pulling down of the packer element this also means that the retraction of the element can be linked to the retraction of the extrusion ring and can happen at the same time. The axial load can be translated into retraction force so that if the tool hangs up in any way, any additional over-pull force only serves to retract the tool further rather than cause the tool to balloon back out again as is the case with prior art designs. Whilst the function of the segmented ring and the packer pull down are linked in this design there is no reason why the pull down feature cannot be used standalone without the extrusion ring so that the advantage of axial load on the tool causing enhanced retraction is retained. Further changes can be made within the scope of the invention.