Patent Application
20100071911
A variety of packers are used in wellbores to isolate specific wellbore regions. A packer is delivered downhole on a tubing string and a packer sealing element is expanded against the surrounding wellbore wall to isolate a region of the wellbore. Often, two or more packers can be used to isolate several regions in a variety of well related applications, including production applications, service applications and testing applications.
In some well applications, slat packers are used to isolate specific regions of wellbores. Slat packers generally are able to support higher differential pressures and higher expansion rates because the slats act as an efficient anti-extrusion barrier for an internal bladder. Slat packers are formed with a tubular rubber bladder covered by metallic slats to support the internal pressure and the mechanical stress to which the packer is submitted. The slats are oriented longitudinally so as to have a high recovery ratio, however the recovery ratio decreases during inflation of the packer. As the packer is inflated, the slats generally slide over each other, but the packer remains totally covered by slats when fully inflated. A rubber sleeve is placed over the layer of slats along their exterior to avoid external leaks between the regions of the well isolated by the packer.
The ability to prevent extrusion of the tubular rubber bladder is important in high-temperature packers because constituents of the internal bladder lose their elastic and mechanical quality at high temperatures. With a slat packer, the internal bladder acts against the layer of slats. However, inflation and deflation of slat packers can be difficult at high hydrostatic pressure because the pressure inside the packer is not balanced with the pressure of the fluid in the well. As a result, the slats are pressed between the internal rubber bladder and the external rubber sleeve which limits the ability of the slats to slide with respect to each other. After several cycles of the packer, unwanted gaps can occur between slats and render the packer susceptible to extrusion of the tubular rubber bladder. Additionally, the rubber material of the sealing layer created by the rubber sleeve also limits the expansion of a slat packer. If the packer is substantially expanded, the rubber material can tear and create a leak. The use of more elastic materials, however, can result in loss of the elastic properties that allow the rubber material to retain its shape after expansion. As a result, the slat packer can be difficult to deflate in a satisfactory manner when such materials are utilized.
In general, the present invention provides a system and method for use in a wellbore to isolate specific regions in a wellbore. The system and methodology utilize a packer formed as an expandable packer with an internal expandable bladder. The internal expandable bladder is surrounded with a plurality of packer slats oriented in a manner to enable expansion and contraction of the packer. Additional features are incorporated into the bladder and/or slats to facilitate repeated expansion and contraction of the packer while preventing both leaks and extrusion of the bladder.
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 that facilitate formation of seals within a wellbore. For example, many types of production and treatment applications involve isolating a specific region or regions along a wellbore. The isolated regions can be created by expanding one or more packers within the wellbore to isolate regions along the wellbore with respect to each other. As described below, one or more slat packers can be moved to a desired position within a wellbore and expanded to form a seal against a surrounding wall, such as a wellbore casing.
In one embodiment, slat packers are uniquely constructed in a manner that reduces friction between slats by forming the slats with coatings. The slat designed enables a good sealing between the axial ends of the packer without using an external sleeve. As result, well fluid can move between the slats and balance the hydrostatic pressure during inflation of the packer. Each slat is linked to an internal bladder in a manner that facilitates expansion/contraction of the packer while ensuring a satisfactory recovery ratio.
In other embodiments, the conventional, external sealing sleeve also can be omitted. For example, the external sleeve can be omitted when the bladder is constructed as a folded bladder to increase the expansion ratio. In this embodiment, the slats are linked to corresponding folds in the bladder so there is no undue extension of the bladder during inflation of the packer. Use of the folded bladder also enables implementation of a variety of materials, such as thermoplastic materials and/or metallic materials that can be in the form of thin metallic sheets. The folded bladder design also allows easy deflation of the packer while applying a lengthwise tension.
Referring generally to
As illustrated in
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The packer slats 44 are attached to expandable internal bladder 42 at attachment regions 50. By way of example, slats 44 can be attached to expandable bladder 42 by gluing, vulcanization, or other suitable attachment mechanisms. Furthermore, packer slats 44 are oriented and attached to internal expandable bladder 42 in a manner such that gaps 52 are formed between adjacent slats 44 while packer 26 is in the contracted configuration and during expansion of packer 26 toward surrounding surface 38. The gaps 52 allow fluid in the well to penetrate into the mechanical structure of packer 26 between adjacent slats 44, as represented by arrows 54. The inflow of well fluid between slats 44 enables equalization of hydrostatic pressure so the slats 44 are not pressed against each other under hydrostatic pressure during expansion of packer 26. The fluid between slats facilitates relative movement of adjacent packer slats during expansion of expandable bladder 42 and packer 26. The formation of separated slats 44 comprising seal material 48 eliminates the need for an external sealing sleeve.
In
During actuation of packer 26 to the sealing configuration illustrated in
The plurality of slats 44 forms a secure, rigorous seal with respect to the surrounding wall 38. Because no external sleeve is necessary, the risk of losing the seal as a result of damage to the external sleeve is eliminated. Additionally, the risk of leaks along the slats is reduced because the seal material 48 on each individual slat 44 creates a secure seal both with the surrounding wall and between adjacent slats when the packer 26 is inflated to compress the slats 44 against each other. Additionally, fluid in the well can penetrate ends of packer 26 without affecting the seal so there is no need to incorporate additional components or to fill empty space in an effort to combat absolute pressure.
The design of packer 26 also promotes longevity and simplifies the manufacturing process because the packer only requires two layers in the form of expandable bladder 42 and the surrounding layer of slats 44. The structure of slats 44 also enables the use of harder seal materials, such as a hard rubber, for example a 90 shore A rubber. Furthermore, the overall structure of packer 26 allows the packer to be easily deflated while applying a lengthwise tension by simply removing fluid from an interior 62 of expandable bladder 42.
Referring generally to
When the packer 26 is in a contracted configuration or during inflation of packer 26 toward surrounding wall 38, the slats 44 are open in a manner that leaves gaps 52 between adjacent slats. The gaps 52 allow fluid in the well to penetrate the slats which creates a hydrostatic balance that facilitates relative movement of the slats 44 during expansion of packer 26. As illustrated in
The foldable bladder 64 can be formed from an elastomeric material, such as a rubber material, that is formed with folds 66 and coupled to slats 44. In other embodiments, the foldable bladder 64 can be formed with a thermoplastic material or a soft metal material 70 constructed with folds 66, as illustrated in
Use of the foldable bladder 64 requires less deformation of the internal bladder and enables dependable, repeatable inflation and deflation of the slat packer 26. The foldable bladder 64 simply folds and unfolds during corresponding radial movement of the slat packer 26.
The overall well system 20 can be constructed in a variety of configurations for use in many environments and applications. For example, one or more slat packers 26 can be combined with a variety of well tool strings 24 to facilitate well testing operations, well treatment operations, well production operations, and other well related operations. Additionally, the slat packer 26 can be constructed from several types of materials and components. The foldable bladder can be created from various elastomeric materials, metallic materials, composite materials, and other materials that can be folded in a manner to accommodate expansion and contraction of the packer. The slats 44 also can be formed in a variety of shapes and sizes and with individual or combined materials. Depending on the well application and environment, the slat material can be similar or distinct relative to the material used to construct foldable bladder 64. Furthermore, the slat packer 26 can be constructed in a variety of configurations with a variety of additional components/structures integrated into the packer design.
In any of the embodiments described above, the packer 26 may be symmetric about its lateral axis A (see
Also, 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, internal expandable bladder 42, seal material 48, and foldable bladder 64.
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.
