CROSS-REFERENCE TO RELATED APPLICATIONS

The following is based on and claims priority to Provisional Application Ser. No. 60/538,975, filed Jan. 23, 2004.

BACKGROUND

In a variety of subterranean environments, such as wellbore environments, downhole tools are used in many applications. For example, downhole tools may be used to construct completions having, for example, packers, safety valves, flow controllers, gas lift valves, sliding sleeves and other tools. The downhole tools often have parts that are sealed with respect to each other via polymeric seal components.

A wellbore or other subterranean region, however, can create a harsh environment for many materials, including conventional polymeric materials. Extreme heat, high differential pressures, chemical attack and other factors can lead to deterioration and failure of such materials.

SUMMARY

In general, the present invention provides a system and methodology for improving the life and/or function of downhole tools. The system and methodology utilize nano-scale filler modified polymers in certain downhole components to substantially improve material properties that enhance the functionality of the downhole components in many subterranean environments.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

FIG. 1 is a front elevation view of a completion positioned in a wellbore and having downhole tools, according to an embodiment of the present invention;

FIG. 2 is a schematic illustration of an embodiment of a nano-filler modified polymer that may be used with, for example, the system illustrated in FIG. 1;

FIG. 3 is a schematic illustration of another embodiment of a nano-filler modified polymer that may be used with, for example, the system illustrated in FIG. 1;

FIG. 4 is a front elevation view of an embodiment of a downhole tool using a nano-filler modified polymer;

FIG. 5 is a front elevation view of another embodiment of a downhole tool using a nano-filler modified polymer;

FIG. 6 is a cross-sectional view of a portion of a downhole tool having a seal, according to another embodiment of the present invention;

FIG. 7 illustrates another embodiment of a seal that can be used with a downhole tool, according to an embodiment of the present invention;

FIG. 8 illustrates another embodiment of a seal that can be used with a downhole tool, according to an embodiment of the present invention;

FIG. 9 illustrates another embodiment of a seal that can be used with a downhole tool, according to an embodiment of the present invention;

FIG. 10 illustrates another embodiment of a seal that can be used with a downhole tool, according to an embodiment of the present invention;

FIG. 11 illustrates another embodiment of a seal that can be used with a downhole tool, according to an embodiment of the present invention

FIG. 12 is a schematic illustration of a tool having a seal, according to another embodiment of the present invention; and

FIG. 13 is another schematic illustration of a tool having a seal, according to an embodiment of the present invention.

DETAILED DESCRIPTION

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 enhancing the life and/or function of downhole tools. The system and method are useful with, for example, a variety of downhole completions and other production equipment. However, the devices and methods of the present invention are not limited to use in the specific applications that are described herein.

Referring generally to FIG. 1, a system 20 is illustrated according to an embodiment of the present invention. In this embodiment, system 20 is a located in a subterranean environment within a wellbore 22. Wellbore 22 is drilled or otherwise formed in a geological formation 24 containing, for example, desirable production fluids, such as hydrocarbon based fluids. Wellbore 22 may be lined with a casing 26 having perforations 28 through which fluids flow between geological formation 24 and the interior of wellbore 22.

In this embodiment, downhole tools 30 are deployed within the wellbore 22 by a deployment system 32. Deployment system 32 may be any of a variety of types of deployment systems, such as production tubing, coiled tubing, cable or other suitable deployment devices. Each of these deployment systems is able to move the downhole tools 30 to a desired location in wellbore 22. Depending on the specific application, the types of downhole tools 30 selected may vary substantially. Often, the downhole tools are assembled in a cooperative arrangement and referred to as a completion.

By way of example, the completion illustrated in FIG. 1 comprises a packer 34 having a polymeric sealing element 36. Sealing element 36 can be activated between a radially contracted state and an expanded state to form a seal with casing 26, as illustrated. The completion may further comprise a flow control device 38, such as a valve or sliding sleeve. If the completion is used to produce fluid upwardly towards a wellhead 40, the downhole tools may comprise a gas lift or electric submersible pumping system having, for example, a submersible motor 44, a motor protector 46 and a submersible pump 48 powered by submersible motor 44. Many of these downhole tools can be operated to facilitate the production of fluid, e.g., valve 38 can be adjusted to control flow, or submersible pump 48 can be operated to produce fluid flow. However, a variety of other completions, including well test completions, well servicing completions and well treatment completions can be used, and the resultant downhole tools are selected based on the type of completion.

In the various completions described above, at least some of the downhole tools utilize polymeric components, e.g. sealing element 36. As described more fully below, the polymeric components utilize nano-scale filler modified polymers to improve material properties and thereby provide substantial benefit with respect to the life and/or functionality of downhole tools 30. With nano-filler modified polymers, as used herein, the filler constituents are primarily nano-scale, generally on the order of a few nanometers. Nano-filler modified polymers can provide significant performance improvements over the base polymers and over reinforced polymers that use conventional fillers in which the reinforcement constituents are much larger, e.g., on the order of microns. For example, polymers with nano-scale fillers show improvements in material strength, modulus and other properties. Due to the resulting high aspect ratio, many material properties of nano-filler modified polymers are substantially improved over those of conventional polymers or polymeric composites at a much lower volume fraction of filler relative to the non-filler material.

Referring generally to FIG. 2, an example of a nano-filler modified polymeric material 50 is illustrated. In this embodiment, material 50 comprises a polymeric material 52, formed of polymer chains 54, and a plurality of nano-fillers 56 serving as cross-linking agents. The nano-fillers 56, in this example, comprise nano-tubes and/or nano-fibers. Nano-tubes can be formed as multiwall nano-tubes, single wall nano-tubes or arrays of nano-tubes. Also, nano-tubes can be formed from a variety of materials, but one example of a useful material is carbon. Carbon nano-tubes exhibit extremely desirable combinations of mechanical, thermal and electrical properties for many applications. For example, carbon nano-tube fillers can be used to substantially increase the tensile strength of the modified polymeric material 50, to increase the current carrying capacity of the material and to increase the heat transfer capability of the material. The enhancement of such properties is beneficial in a variety of downhole components, some of which are discussed in greater detail below. Nano-fibers, on the other hand, can be made from, for example, graphite, carbon, glass, cellulose substrate and polymer materials.

Another embodiment of nano-filler polymeric material 50 is illustrated in FIG. 3. In this embodiment, polymer material 52 has polymer chains 54 linked by nano-fillers 58 comprising nano-particles or nano-clay. Nano-particles can be made, for example, from metals, graphite, carbon, diamond, ceramics, metal oxides, other oxides and polymer materials. Nano-clay can be made, for example, from montmorillonite, bentonite, hectorite, attapulgite, kaolin, mica and illite. Certain types of nano-clay can be used, for example, in applications that benefit from the enhancement of specific material properties, such as increasing the tensile strength of material 50.

Polymer material 52 can be made from a variety of types of plain or modified elastomeric or thermoplastic materials. Examples of the elastomers include nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), carboxyl nitrile rubber (XNBR), silicone rubber, ethylene-propylene-diene copolymer (EPDM), fluoroelastomers (FKM, FEPM) and perfluoroelastomer (FFKM). Examples of thermoplastics include Teflon®, polyetheretherketone (PEEK), PP, PE, PS and PPS.

These modified polymer nanocomposites can be used for many downhole applications, such as seal applications. For example, nano-filler modified polymers can be used as a packer sealing element 36, O-rings, backup rings and other types of seals. The nano-fillers 56, 58 can be selected to improve the material properties of the polymeric components, including improvements in tensile strength, compressive strength, tear/shear strength, modulus, compression set, chemical resistance, heat resistance and heat/electrical conductivity properties.

Nano-filler modified polymers can be prepared via a variety of processes. Examples of such processes include solution processes, mesophase mediated processes, in situ polymerization and physical mixing or compounding. Also, a variety of curing methods can be used, including thermal curing, microwave radiation curing and electronic beam radiation curing. The nano-fillers also can be modified prior to manufacture of the polymer nanocomposites to achieve optimum dispersion of nano-fillers. Additionally, functionalized nano-fillers may serve as cross-linking agents in polymer blends. Such techniques can even be used to cross-link thermoplastic materials.

Referring generally to FIG. 4, one example of a downhole tool 30 is schematically illustrated in the form of packer 34. Packer 34 is used, for example, to separate a lower portion 60 of wellbore 22 from an upper portion 62 of the wellbore. Packer 34 uses some type of sealing element 36 to form a seal between the packer body 64 and the wall of wellbore 22, e.g. casing 26, at a desired seal region. The expanded sealing element also can be used as an anchor. Thus, packer 34 can utilize sealing element 36 as both a seal and an anchor within the wellbore. The downhole tool 30 also may be formed as a bridge plug with sealing element 36.

Sealing element 36 provides an example of a tool component formed at least partially of nano-filler modified polymers. Sealing element 36 also might be formed in a variety of configurations, such as the illustrated embodiment having a pair of end rings 66 and a center element 68. The end rings 66 and center element 68 are formed of nano-filler modified polymers and may comprise a mixture of materials. For example, end rings 66 and center element 68 may be formed of nano-filler modified elastomers in one embodiment. However, in another embodiment, center element 68 is formed of a nano-filler modified elastomer while end rings 66 are formed of nano-filler thermoplastic materials.

In FIG. 5, another embodiment of a downhole tool 30 is illustrated. The downhole tool may comprise, for example, a valve, such as a safety valve, or a sliding sleeve. In any event, the downhole tool 30 comprises a housing 70 having an internal element 72, e.g. slide or valve member, that moves relative to housing 70. A seal is formed between housing 70 and internal element 72 via a seal member 74 disposed at a desired seal region. Seal member 74 is formed of a nano-filler modified polymer to enhance the material properties of seal member 74 and thereby improve the life and/or functionality of downhole tool 30. The specific form of seal member 74 used in a given tool 30 may vary substantially, depending on such factors as tool function, tool type or environment in which the downhole tool is operated. Examples of various seals that can be used in downhole tools are illustrated and described with reference to FIGS. 6 through 11.

Referring first to FIG. 6, seal member 74 is disposed between a first component 76 and a second component 78 that slides relative to first component 76. The relative sliding components can be components from a variety of downhole tools, including valves, sliding sleeves and pumps. In this embodiment, seal member 74 comprises an O-ring seal 80. O-ring seals often serve as simple bi-directional static seals. The seal member 74 also may comprise a pair of backup rings 82 disposed on opposite sides of O-ring 80. O-ring 80 and backup rings 82 all may be formed of nano-filler modified polymers. For example, O-ring 80 may be formed of a nano-filler modified elastomer, and backup rings 82 may be formed of nano-filler reinforced thermoplastic materials.

Another seal example is illustrated in FIG. 7. In this embodiment, seal member 74 comprises a T-seal having a generally T-shaped center portion 84 and a pair of reinforcement rings 86. T-seals are used in downhole tools that require, for example, a bi-directional dynamic seal between relative reciprocating components. Depending on the application, the T-seal may be made of nano-filler modified thermoplastics, nano-filler modified elastomers or a combination of the two polymer types.

Referring generally to FIG. 8, seal member 74 is illustrated as a V-packing or chevron seal stack. A chevron seal stack comprises multiple component seal sets having multiple seal lips energized by differential pressure. These types of seals are used in a variety of downhole applications and are suitable for internal dynamic seal applications. In the embodiment illustrated, the seal stack comprises seal sets 88 and 90 formed of softer and relatively harder polymeric materials, respectively. For example, the seal sets 88, 90 may form a seal stack of alternating softer and harder polymeric materials. In this example, seal sets 88 are formed of nano-filler modified elastomer materials, and seal sets 90 are formed of nano-filler modified thermoplastic materials.

Additional examples of nano-filler modified polymeric seals are illustrated in FIGS. 9 through 11. In each of these examples, seal member 74 comprises a spring energized seal formed as a unidirectional static or dynamic seal. For example, in FIG. 9, seal member 74 comprises a seal body 92 having seal surfaces 94 and a recessed interior 96. A U-shaped spring number 98 is disposed in recessed interior 96 to force seal surfaces 94 outwardly.

A similar embodiment is illustrated in FIG. 10, except the U-shaped spring number 98 is replaced with a spring number 100 having a generally circular or oval cross-section. Similar to the embodiment described with respect to FIG. 9, spring number 100 biases seal surfaces 94 in an outward direction. Another similar embodiment is illustrated in FIG. 11. In this example, seal body 92 comprises a pair of adjacent recessed interiors 96 that contain spring members 102. Spring members 102 may be formed in a variety of configurations, including a pair of U-shaped spring members as illustrated in FIG. 11. In any of the embodiments illustrated in FIGS. 9-11, nano-filler modified elastomers or thermoplastics are used according to the design parameters of a given downhole tool and/or environment.

The nano-filler modified polymeric components discussed above are examples of some components that can be used in downhole applications. However, additional types of seals and other components also can be formed from such materials to improve material properties and provide downhole tools better able to withstand the harsh subterranean environments in which they function. Other component examples include a soft seat 106 used with a downhole tool 30, as illustrated in FIG. 12. Soft seats 106 may be used on downhole tools such as valves. A specific example is a safety valve having a soft seat 106 to provide an initial seal between a flapper 108 and a hard metal seat 110. Such soft seats can be formed of nano-filler modified thermoplastics or elastomeric materials.

Another example is a tool 112 having a bonded seal 114 formed of a nano-filler modified polymeric material bonded to a metal or composite carrier 116 at a bond region 118. Such bonded seals are used in a variety of tools 112, including service pistons, reciprocating clutches, power pistons and other components. Furthermore, other non-seal downhole tool components also can be formed from nano-scale filler modified polymers.

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. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.