Patent Application
20100294516
A variety of packers are used in wellbores to isolate specific wellbore regions. A packer is delivered downhole on a conveyance and expanded against the surrounding wellbore wall to isolate a region of the wellbore. Once set against the surrounding wellbore wall, the packer can be subjected to substantial heat, pressures and forces. Consequently, flexible rubber packer layers can undergo undesirable extrusion which has a detrimental effect on the function of the packer.
Some packers employ anti-extrusion layers to limit the undesirable extrusion. However, expansion/inflation of the packer under high temperature and high-pressure conditions can cause unwanted movement and/or disruption of the anti-extrusion layer. Often, existing packer designs are not suitable for controlling anti-extrusion layer movement during packer inflation and particularly during multiple inflation cycles.
Undesirable movement of the anti-extrusion layer can be induced by a variety of factors related to operation of the packer in a downhole environment. By way of example, rubber materials may creep under the influence of inflation pressure which can result in unwanted additional expansion of the anti-extrusion layer and an undesirable shortening ratio. Expansion of the packer also can cause disorganization of anti-extrusion layer fibers which again increases the shortening ratio. The crossing or disruption of fibers in the anti-extrusion layer also may create high friction points that again influence the shortening ratio. The combination of excessive friction and unwanted local shortening ratio creates a substantial pulling force on the anti-extrusion layer at the packer extremities. If the pulling force is not controlled or countered, the anti-extrusion layer can be pulled free of the packer extremities or otherwise damaged in a manner that detrimentally affects the functionality of the packer.
In general, the present invention provides a system and method for controlling anti-extrusion layer movement during packer inflation. A packer is designed with a packer nipple having retention features which uniquely engage layers of the packer. The retention features are positioned at a plurality of distinct retention regions. Each retention feature is designed to engage a specific layer of the packer. An individual retention feature may be designed to secure the anti-extrusion layer.
Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
The present invention generally relates to a system and method for constructing a packer designed to better withstand the rigors of actuation in a downhole environment. According to one embodiment, the packer is designed to maintain the placement of an anti-extrusion layer during multiple inflation cycles of the packer while in the high temperature well environment. Maintaining desired placement of the anti-extrusion layer helps ensure packer efficiency over the life of the packer.
Generally, the packer comprises a plurality of expandable layers that are held at their opposed, longitudinal ends by mechanical extremities. In one example, the plurality of expandable layers comprises inner and outer bladders, an anti-extrusion layer, and a mechanical layer that may be formed of cables or other mechanical components to strengthen the packer. At least one of the mechanical extremities comprises retention features designed to individually retain selected packer layers. For example, retention features may be provided to independently secure the anti-extrusion layer. Additionally, the retention features also may be designed to independently secure other packer layers, such as the inner bladder layer and/or the mechanical layer.
One or more of the improved packers can be used in a given well system to isolate regions of the wellbore. For example, packers can be used in cooperation with, or formed as part of, a variety of well completions. The well completions are deployed downhole for use in various production operations, servicing operations, or other well related operations.
Referring generally to
Referring generally to
The expandable portion 34 is constructed with a plurality of packer layers 46 arranged adjacent one another in a radial direction. In the embodiment illustrated, packer layers 46 comprise an inner bladder layer 48 that may be formed of a rubber material or other elastomeric material. Radially outward of inner bladder layer 48 is an anti-extrusion layer 50 positioned to prevent unwanted extrusion of the elastomeric material. The anti-extrusion layer 50 may be formed from a variety of materials that enable expansion and contraction of expandable portion 34. For example, anti-extrusion layer 50 may be formed from fibers or a combination of fibers and mechanical cables. Additionally, the anti-extrusion layer 50 may extend from one mechanical extremity to the other or may extend axially inward a desired, but limited, distance from each mechanical extremity 36.
Packer layers 46 also may comprise a mechanical layer 52 which may be formed with metal, e.g. steel, cables or other structural components. By way of example, mechanical layer 52 comprises a plurality of steel cable layers 54, e.g. two steel cable layers, and is located radially outward of anti-extrusion layer 50. Depending on the application, mechanical layer 52 also may be designed with four cable layers, six cable layers, or other numbers of cable layers 54. Packer layers 46 may further include an outer bladder or seal layer 56 which is the radially outermost layer of expandable portion 34. Seal layer 56 is designed to seal against the surrounding wellbore wall, e.g. casing, to isolate the desired region of wellbore 22. At least some of the individual packer layers 46 are independently retained at one or both of the mechanical extremities 36 via retention features 58 located at unique retention regions, as described in greater detail below. In one example, the retention features 58 are located along a radially outward exterior of the packer nipple 38.
In various applications, it is important to independently retain the anti-extrusion layer 50 against pulling forces that can occur during actuation, e.g. expansion, of packer 26. The design of anti-extrusion layer 50 can affect the forces experienced by the anti-extrusion layer 50 and by the specific retention feature 58 used to independently retain the anti-extrusion layer. In the schematic example illustrated in
Referring generally to
The actual engagement of individual layers 46 by retention features 58 may be accomplished by a variety of mechanisms. According to one embodiment, mechanical layer 52 comprises a crimped end portion 68 that is retained between inner packer nipple 38 and outer skirt 40. For example, crimped skirt system 42 may comprise a crimped engagement region 70, as illustrated in
The mechanical layer retention region 66 of inner nipple 38 also may comprise a crimped surface region 74, as illustrated in
Retention features 58 also may comprise a variety of other mechanisms and surfaces. For example, inner bladder gripping region 62 may comprise a series of surface undulations 76, as illustrated in
In the example illustrated, the multilevel profile 78 is positioned and designed to cooperate with crimping feature 72 of skirt portion 42 to securely grip the anti-extrusion layer 50 when crimped between inner packer nipple 38 and outer skirt 40. In this particular design, the anti-extrusion layer 50 is longer than inner bladder 48 to enable independent retention of the individual layers via distinct retention features 58. This avoids use of the inner bladder layer 48, which has a relatively poor shear resistance, to secure the anti-extrusion layer 50. Instead, the anti-extrusion layer 50 is held by the multilevel profile 78 which may be formed in a metal material used to construct inner nipple 38. The skirt and nipple designs may be optimized for efficient retention of the anti-extrusion layer 50 after crimping of the plurality of layers between the inner packer nipple 38 and outer skirt 40.
Referring generally to
In
In any of the embodiments described above where a component is described as being formed of rubber or comprising rubber, the rubber may include an oil resistant rubber, such as NBR (Nitrile Butadiene Rubber), HNBR (Hydrogenated Nitrile Butadiene Rubber) and/or FKM (Fluoroelastomers). In a specific example, the rubber may be a high percentage acrylonytrile HNBR rubber, such as an HNBR rubber having a percentage of acrylonytrile in the range of approximately 21 to approximately 49%. Components suitable for the rubbers described in this paragraph include, but are not limited to, inner bladder layer 48, outer seal layer 56, and elastomeric material between expandable layers.
As described above, well system 20 and packer 26 may be constructed in a variety of configurations for use in many environments and applications. The packer 26 may be constructed from many types of materials and with components/layers positioned in various arrangements. Additionally, individual packer retention features can be arranged to hold a variety of selected, expandable packer layers. The specific surfaces and features used to independently grip specific packer layers are selected according to the packer design and layer material. Additionally, a variety of components and/or materials can be used in cooperation with select packer layers, e.g. the anti-extrusion layer 50, to aid in retention during repeated expansion and contraction of the packer. The design and components of the packer extremities also can be adjusted according to the design of the overall packer. In some applications, the retention features are used at both packer extremities while in other applications the retention features are used at only one of the packer extremities.
Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.
