US20050109502A1 - Downhole seal element formed from a nanocomposite material - Google Patents

Abstract

A seal element (70) for providing a static or dynamic seal between two components (74, 78) in a downhole tool includes a polymer host material (212) and a plurality of nanostructures (220) forming a nanocomposite material (210). The polymer host material (212) has a plurality of regions of free volume (222) that receive the nanostructures (220). The nanostructures (220) and the polymer host material (212) form interfacial interactions that improve the useful life of the seal element (70) by minimizing seal failures associated with explosive decompression, extrusion, spiral failure, abrasion, temperature degradation and the like.

Description

TECHNICAL FIELD OF THE INVENTION
• The present invention relates, in general, to a seal element and backup system for use in downhole tools positioned within a wellbore that traverses a subterranean hydrocarbon bearing formation and, in particular, to a downhole seal element formed from a nanocomposite material including a polymer host material and a nanomaterial.
BACKGROUND OF THE INVENTION
• Without limiting the scope of the present invention, its background will be described with reference to explosive decompression of static seals, as an example.
• A seal is a device used to close a gap or make a joint fluid-tight with respect to both liquids and gases. For example, static seals involve sealing surfaces that do not move relative to one another and dynamic seals involve sealing surfaces that do move relative to one another. In particular, static seals are zero-leakage barriers that provide a long-term complete physical barrier in a potential leakage path to which they are applied. To achieve this, the static seals must be resilient to flow and fill any irregularities in the surface being sealed while resisting extrusion into the clearance gap between the surfaces under full system pressure.
• Despite their dependability and reliability, static seals in oil-field equipment can be damaged by explosive decompression when the pressure on the system containing the static seals is released. Seals usually have naturally occurring flaws that are 40 microns or less in size. Under pressure, fluid and gases can enter these voids and reach equilibrium. Moreover, as the pressure decreases, a positive internal pressure in the voids is created that increases the amount of fluid and gases that can enter these voids. If the system containing the static seals is depressurized too rapidly, the liquids and gases that enter these void sites in the static seal can cause damage which is typically exhibited by surface blisters, ruptures and fractures. Internal damage may also accompany the surface damage and occur without external evidence thereof.
• The effects of explosive decompression can be minimized by slowly reducing the applied pressure to ambient. For example, the NACE Standard TM 0187-87, Evaluating Elastomeric Materials in Sour Gas Environments, recommends a decompression procedure that includes a bleed-down rate of 20 psi per minute or 100 psi and a waiting period of five minutes before continuing with another pressure reduction of 100 psi. Due to the importance of static seals, solutions to explosive decompression have not been limited to decompression procedures.
• The primary structural factors that control a static seal's resistance to explosive decompression are the critical pressure, the flaw size and the shear modulus of the static seal. The critical pressure is the pressure at which the voids in the seal element expand and begin to blister or rupture. The flaw size represents the size of the naturally occurring voids in the static seal. The shear modulus, is a measure of the hardness and cross-link density, i.e., the number of connections between the polymer chains that make up the static seal, of the static seal. The critical pressure and flaw size are inherent properties of the static seal that have proven difficult to improve. Hence, existing static seals have been improved by adding reinforcing seals such as back-up rings. The reinforcing seals have shown themselves to costly and inadequate, however.
• Therefore, a need has arisen for a downhole seal element that comprises a material which minimizes the effects of explosive decompression. A need has also arisen for such a downhole seal element that minimizes the critical pressure and the flaw size of the seal element. Further, a need has arisen for such a seal element that has an improved shear modulus.
SUMMARY OF THE INVENTION
• Accordingly, the present invention provides a downhole seal element that comprises a material which minimizes the effects of explosive decompression. The downhole seal element of the present invention minimizes the critical pressure and the flaw size of the seal element while improving the shear modulus. The seal element of the present invention overcomes the limitations of the existing seals by utilizing a nanocomposite material comprising a polymer and a nanomaterial.
• In one aspect, the present invention is directed to a seal element for providing a seal between two components in a downhole tool. The seal element is formed from a polymer host material having a nanomaterial integrated therewith to form a nanocomposite material. The nanomaterial in combination with the polymer not only minimizes the likelihood of explosive decompression, but also improves a variety of additional seal properties, thereby preventing numerous types of downhole seal failures such as extrusion, spiral failure, abrasion, temperature degradation and the like.
• In one embodiment, the seal element of the present invention may be an O-ring seals, D-seals, T-seals, V-seals, X-seals, flat seals, lip seals, back-up rings, bonded seals and packing elements, for example. The polymer host material may comprise an elastomer, a thermoset, a thermoplastic or the like. In particular, the polymer host material may comprise an elastomer such nitrile butadiene (NBR) which is a copolymer of acrylonitrile and butadiene, carboxylated acrylonitrile butadiene (XNBR), hydrogenated acrylonitrile butadiene (HNBR) which is commonly referred to as highly saturated nitrile (HSN), carboxylated hydrogenated acrylonitrile butadiene (XHNBR), hydrogenated carboxylated acrylonitrile butadiene (HXNBR), ethylene propylene (EPR), ethylene propylene diene (EPDM), tetrafluoroethylene and propylene (FEPM), fluorocarbon (FKM), perfluoroelastomer (FEKM) and the like. The polymer host material may be formed from a thermoplastic such as polphenylene sulfide (PPS), polyetheretherketones such as (PEEK), (PEK) and (PEKK), polytetrafluoroethylene (PTFE) and the like. The polymer host material may be formed from a thermoset such as epoxies and phenolics.
• The seal element may further include a reinforcement material such as a powder material, a fiber reinforcement material or a metal reinforcement material. The nanomaterial may be a metal oxide, a nanoclay, a carbon nanostructure or the like and equivalents thereof. The nanomaterial may comprise nanoparticles having a scale in the range of approximately 0.1 nanometer to approximately 500 nanometers. For example, the nanomaterial may be formed from a silicon-based material such as a polysilane resin, a polycarbosilane resin, a polysilsesquioxane resin, a polyhedral oligomeric silsesquioxane resin or the like and equivalents thereof. The polymer host material and the nanomaterial may have interfacial interactions such as copolymerization, crystallization, van der Waals interactions and cross-linking interactions.
• In another aspect, the present invention is directed to a downhole tool that has a first component having a groove and a second component positioned relative to the first component forming a gap therebetween. A seal element is positioned in the groove and extends across the gap into sealing contact with the second component. The seal element is formed from a nanocomposite material inlcuding a polymer host material and a plurality of nanostructures.
• In one embodiment, first component of the downhole tool is stationary relative the second component when the downhole tool is in an operational configuration. In another embodiment, first component and the second component move relative to one another when the downhole tool is in an operational configuration wherein the relative movement is either translational, rotational or both.
• In yet another embodiment, the first component and the second component are tubular components. In this embodiment, the first component may be positioned interiorly or exteriorly of the second component. The first and second components may form a portion of a device such as drill bits, mud motors, flow control devices, safety devices, valves, sliding sleeves, telemetry equipment, perforating guns, testing devices and pumps.
• In another aspect, the present invention is directed to a seal assembly for providing a seal in a wellbore annulus. The seal assembly has a generally tubular mandrel and a seal element positioned exteriorly of the mandrel such that the seal element is operable to substantially prevent fluid flow in the wellbore annulus when the seal assembly is in a sealing configuation. The seal element comprising a nanocomposite material including a polymer host material and a plurality of nanostructures.
BRIEF DESCRIPTION OF THE DRAWINGS
• For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:
• FIG. 1 is a schematic illustration of an offshore oil and gas platform performing completion operations wherein the sealing material of the present invention is advantageously deployed;
• FIG. 2 is a schematic illustration of an offshore oil and gas platform performing production operations wherein the sealing material of the present invention is advantageously deployed;
• FIG. 3 is a schematic illustration of an O-ring seal comprising a nanocomposite material in accordance with the teachings of the present invention;
• FIG. 4 is a schematic illustration of an O-ring seal with back-up rings comprising a nanocomposite material in accordance with the teachings of the present invention;
• FIG. 5 is a schematic illustration of a T-seal comprising a nanocomposite material in accordance with the teachings of the present invention;
• FIG. 6 is a schematic illustration of a X-seal comprising a nanocomposite material in accordance with the teachings of the present invention;
• FIG. 7 is a schematic illustration of a V-ring stacking assembly comprising a nanocomposite material in accordance with the teachings of the present invention;
• FIG. 8 is a cross-sectional view of a section of composite coiled tubing comprising a nanocomposite material in accordance with the teachings of the present invention;
• FIG. 9 is a schematic illustration of a packing mandrel comprising a nanocomposite material in accordance with the teachings of the present invention;
• FIG. 10 is a nanoscopic view of a nanocomposite material including a polymer host material and a nanostructure used in a downhole tool in accordance with the teachings of the present invention;
• FIG. 11 depicts the structural formula of one embodiment of a silicon-based nanostructure used in a downhole tool in accordance with the teachings of the present invention;
• FIG. 12 depicts the structural formula of a second embodiment of a silicon-based nanostructure used in a downhole tool in accordance with the teachings of the present invention;
• FIG. 13 depicts the structural formula of a third embodiment of a silicon-based nanostructure used in a downhole tool in accordance with the teachings of the present invention;
• FIG. 14 depicts the structural formula of a fourth embodiment of a silicon-based nanostructure used in a downhole tool in accordance with the teachings of the present invention; and
• FIG. 15 is a nanoscopic view of a nanocomposite material including a polymer host material, a plurality of nanostructures and an additive used in a downhole tool in accordance with the teachings of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the present invention.
• Referring initially toFIG. 1, an offshore oil and gas platform performing drilling operations is schematically illustrated and generally designated10. Asemi-submersible platform12 is centered over a submerged oil andgas formation14 located belowsea floor16. Asubsea conduit18 extends fromdeck20 ofplatform12 towellhead installation22 includingblowout preventers24.Platform12 has ahoisting apparatus26 and aderrick28 for raising and lowering pipe strings such asdrill string30.
• Awellbore32 extends through the various earthstrata including formation14. Acasing34 is cemented within a portion ofwellbore32 bycement36.Wellbore32 has anopen hole portion38 that is being extended in the illustrated embodiment. Specifically,drill string30 includes adrill bit40 and areamer42 on its downhole end.Drill bit40 andreamer42 are being rotated by pumping a fluid throughmud motor44. During the drilling process, the subterraneanstructures surrounding wellbore32 may be evaluated using a measurement-while-drilling (MWD) or logging-while-drilling (LWD)tool46. Information obtained usingtool46 may be sent to the surface viatelemetry tool48 that may transfer information via mud pulses, acoustic waves, electromagnetic waves or the like.
• Shortly afterdrill bit40 intersectsformation14, drilling may be stopped to allow formation testing before significant mud invasion or filter cake build up occurs. For example, pumpassembly50 may be operated to draw down the formation pressure information14 so that formation fluids can be quickly pumped intoformation evaluation tool52.Formation evaluation tool52 is used to obtain a representative sample of formation fluid or gather other formation data with a minimum of drilling downtime. Using MWD/LDW tool46 andformation evaluation tool52 valuable information can be obtained relating toformation14 such as permeability, porosity, fluid resistivity, temperature, pressure, bubble point, viscosity and the like.
• As should be understood by those skilled in the art, a variety of the tools indrill string30 utilize polymeric and elastomeric components. For example,drill bit40 includes a pressure-compensated reservoir that has a lubricant therein that lubricates the bearings between each of the journal pins ofdrill bit40 and its respective rotary cutter. An elastomeric diaphragm is positioned within the pressure-compensated reservoir to pressurize the lubricant. In addition, there is an elastomeric seal element positioned between each journal pin and rotary cutter ofdrill bit40 that retains the lubricant in the bearing surfaces and prevents fluids from the exterior ofdrill bit40 from entering the bearing surfaces.
• As another example,mud motor44 utilizes a stator having an elastomeric inner housing having a plurality of lobes that interact with the spiral wound lobes of the rotor such that when drilling fluid is pumped therethrough, the rotor rotates relative to the stator and imparts rotation to drillbit40. In addition,mud motor44 utilizes a plurality of elastomeric seals to retain lubricant in the bearing surfaces and prevent drilling fluids from contacting the bearing surfaces. Likewise,telemetry tool48,pump assembly50formation evaluation tool52 as well as other tools typically used drilling the drill of a wellbore, either in combination with or instead of the aforementioned tools, utilize polymeric and elastomeric components.
• Referring next toFIG. 2, offshore oil andgas platform10 is depicted following a completion operation. Specifically, aproduction tubing string54 has been installed withinwellbore32 which is now fully cased. In addition, casing34 has been perforated atformation14 using perforatingguns56 which have been released into the rat hole ofwellbore32.Production tubing string54 includes a sandcontrol screen assembly58 that is positioned between a pair ofseal assemblies60 that isolate production toformation14. Uphole of sand control screen assembly58 a fluidloss control valve62 is positioned that prevents the loss of fluid from withinproduction tubing string54 toformation14 during completion operations uphole offormation14. For example, following a treatment operation within the production interval atformation14 such as a gravel pack, fracture stimulation, frac pack or the like, a service tool including a variety of tools may be pulled uphole such that a treatment operation may be performed on a formation (not pictured) uphole offormation14. During this subsequent treatment operation, fluid loss intoformation14 is prevented by fluidloss control valve62.
• Also depicted withinproduction tubing string54 is atubing test valve64 that allows for the periodic pressure testing ofproduction tubing string54 during installation thereof.Production tubing string54 also includes a plurality of landing nipples, such aslanding nipple66, which is used to receive, for example, wireline set tools such as permanent and temporary bridge plugs as well as other types of flow control devices. A slidingslide door valve68 is depicted withinproduction tubing string54. Slidingslide door valve68 may be used to selectively permit and prevent fluid communication between the interior ofproduction tubing string54 and the wellbore annulus.Production tubing string54 includes one or more subsurface safety valves, such assafety valve69, that prevent out of control well conditioned from traveling to the surface.
• Many of these completion tools and production tools, as well as numerous other downhole tools utilize polymeric and elastomeric components. As an example, perforatinggun56 utilizes numerous seals so that atmospheric pressure can be maintained within the shaped charge carrier. Also,seal assemblies60 have polymeric and/or elastomeric seal elements that are radially expanded to create a seal betweenproduction tubing string54 andcasing34. Likewise, fluidloss control valve62,tubing test valve64, slidingside door valve68,subsurface safety valve69, a multi-position gravel packing valve as well as numerous other valving and flow control devices utilize polymeric and/or elastomeric seals between gaps in metal components. Furthermore, polymeric and/or elastomeric seals may be used on devices that are permanently or temporarily positioned with landingnipple66 such as a bridge plug or other plugging device.
• As should be understood by those skilled in the art, numerous downhole tools including those specified above with reference toFIGS. 1 and 2, utilize polymeric and elastomeric seals to provide both static and dynamic sealing between stationary and moving metal components. For example, as seen inFIG. 3, an O-ring seal70 is positioned within agroove72 oftubular component74 and extends across agap76 betweentubular component74 andtubular component78. In this configuration, O-ring seal70 prevents the passage of fluid pressure throughgap76 from one side of O-ring70 to the other. It should be noted that O-rings are one of the simplest and most versatile types of seal with a wide range of applications. For example, O-ring seal70 is suitable for use in downhole tools whereintubular component74 andtubular component78 are stationary relative to one another or whereintubular component74 andtubular component78 move relative to one another in either a translational action, a rotational action or both.
• In certain high pressure applications, an O-ring may be susceptible to extrusion into the gap between components. In such situations, as seen inFIG. 4, an O-ring seal80 may be used on conjunction with one or more back-up rings84,86. As illustrated, O-ring seal80 and back-up rings82,84 are positioned within a groove86 oftubular component88 and extend across agap90 betweentubular component88 andtubular component92. Together, O-ring seal80 and back-up rings82,84 prevent the passage of fluid pressure throughgap90 from one side of O-ring seal80 to the other.
• In addition to O-ring seals, there are a variety of other types of seals having a wide array of geometries. For example, as seen inFIG. 5, a T-seal100 is positioned within agroove102 intubular component104. T-seal100 cooperates with a pair of back-uprings106,108 that are positioned within an expanded portion ofgroove102. T-seal100 and back-uprings106,108 extend acrossgap110 betweentubular component104 andtubular component112 to provide a seal therebetween. In particular, the arrangement of T-seal100 and back-uprings106,108 is particularly suited for dynamic sealing applications such as moving piston applications since back-uprings106,108 have a wide profile that provides support for the leg region of T-seal100 during piston stroking loads.
• As another example,FIG. 6 depicts anX-ring seal120 positioned withingroove122 oftubular component124 and extending acrossgap126 betweentubular component124 andtubular component126.X-ring seal120 may be used in place of an O-ring in a variety of static and dynamic applications.X-ring seal120 has a 4-lobe configuration such that two sealing areas are created per side as opposed to one sealing area on an O-ring. In addition,X-ring seal120 requires less squeeze to maintain an effective seal which reduces friction and increasing seal life.
• In some applications, a series of seals is desirable to prevent potential leakages. As seen inFIG. 7, a packingstack assembly130 includes an O-ring132 in the center having two sets of oppositely facing V-ring stacks134,136 each having four V-rings and each having an outer female adaptor. Due to the shape of the V-rings, packingstack assembly130 provide pressure seals in both directions and have high extrusion resistance allowing packingstack assembly130 to handle relatively large extrusion gaps.Packing stack assembly130 is suitable for use in a variety of downhole tools including packer seal units, wireline retrievable locks and safety valves.
• While several examples of seal for use in downhole tools have been depicted and discussed herein, the teachings of the present invention are equally applicable to other types of seal having other geometry configurations including, but not limited to, D-rings, U-rings, lip seals, flat seals, symmetric seals, cup seals, wipers or the like and equivalents thereof.
• As should be understood by those skilled in the art, numerous downhole tools utilize polymeric and elastomeric materials in function other than seals. For example,FIG. 8 depicts a section of composite coiledtubing140 that includes aninner fluid passageway142 defined by aninner thermoplastic liner144 that provides a body upon which to construct the compositecoiled tubing104 and that provides a relative smoothinterior bore146.Fluid passageway142 provides a conduit for transporting fluids such as production fluids, hydraulic fluid, treatment fluids/slurries and the like. Layers of braided or filament wound material such as Kevlar or carbon encapsulated in a matrix material such asepoxy surround liner144 forming a plurality of generally cylindrical layers, such aslayers148,150,152,154 and156 of composite coiledtubing140. A pair of oppositely disposedinner areas158,160 are formed within composite coiledtubing140 betweenlayers152 and154 by placing layered strips of carbon or other stiff material therebetween.Inner areas158,160 have conduits that may be employed for a variety of purposes, such as running power lines, control lines, communication lines or the like.
• As another example,FIG. 9 depicts aseal assembly170 that may be used to provide a seal between a production tubing string and a casing string or open hole of a wellbore as discussed above with reference toFIG. 2.Seal assembly170 includes amandrel172 that provides structural support for the various seal elements and provides an inside passageway for fluid flow.Mandrel172 may be formed from a metal such as carbon steel, a composite material such as that discussed above with reference toFIG. 8, or a polymeric material such as a thermoplastic.Seal assembly170 includes acenter element174 that is a soft elastomeric element which provides the primary seal and is the first to deform and contact both the mandrel and casing during setting operations. Oncecenter element174 compresses, endelements176,178 begin to energize and expand out into contact with the casing. As such,center element174 and endelements176,178 combine to seal the annular space between packingmandrel172 and the casing.Respective wire meshs180,182, brass back-upshoes184,186 and elastomeric back-upshoes186,188 provide an anti-extrusion system.
• Each of the elastomeric or polymeric components for downhole tools discussed above as well as equivalents thereof can be formed from a nanocomposite material of the present invention to improve various properties of the material and enhance the useful life of the nanocomposite components and therefore the useful life of the downhole tools.FIG. 10 depicts a nanoscopic view of ananocomposite material210 for use in downhole tools.Nanocomposite material210 is formed from apolymer host material212 that includes multiple polymers, such aspolymers214,216,218 and a plurality of nanostructures such as the depictednanostructure220.Polymer host material212 exhibits microporocity as represented by a plurality of regions of free volume, such asregion222. In the illustrated embodiment,nanostructure220 is positioned withinfree volume region222.
• Nanostructure220 structurally and chemically complements the microporocity ofpolymer host material212. More specifically, asnanostructure220 has a greater surface area thanpolymer host material212, due to the nano-size and nano-volume ofnanostructure220,nanostructure220 is integrated withpolymer host material212 and forms interfacial interactions withpolymer host material212 atregion222. The interfacial interactions, including copolymerization, crystallization, van der Waals interactions and cross-linking interactions, are formed betweennanostructure220 andmultiple polymers214,216,218 to not only improve the tensile strength, compression set and temperature stability ofpolymer host material212, but also the extrusion resistance, explosive decompression resistance and abrasion resistance ofhost polymer material212, thereby resulting in an extended life for the diaphragms, seal elements, packing element and other downhole component that are formed fromnanocomposite material210 of the present invention.
• Polymer host212 may comprise any combination of elastomers, thermosets and thermoplastics, for example. Elastomers are thermoset materials commonly referred to as rubbers. In particular, elastomers are polymeric materials that over a range of temperatures are capable of recovering substantially in shape and size after removal of a deforming force.
• More specifically,polymer host212 may be formed from a nitrile elastomer such as nitrile butadiene (NBR) which is a copolymer of acrylonitrile and butadiene, carboxylated acrylonitrile butadiene (XNBR), hydrogenated acrylonitrile butadiene (HNBR) which is commonly referred to as highly saturated nitrile (HSN), carboxylated hydrogenated acrylonitrile butadiene and the like.Polymer host212 may also be formed from other elastomers such as ethylene propylene (EPR), ethylene propylene diene (EPDM), tetrafluoroethylene and propylene (FEPM), fluorocarbon (FKM), perfluoroelastomer (FEKM) or the like and equivalents thereof.
• For example, the use of an HSN elastomer providespolymer host212 with the properties of elasticity, good chemical resistance, high mechanical strength and good resistance to abrasion at elevated temperatures as well as a low coefficient of friction and excellent wear resistance. As compared with standard nitrile elastomers, HSN elastomers are hydrogenated to reduce the number of carbon-carbon double bonds. The hydrogenation process preferable eliminates between about 90% and 99.5% of the double bonds in the nitrile. The removal of the carbon-carbon double bonds reduces the reaction of agents such as hydrocarbons, oxygen, hydrogen sulfide and ozone with the elastomer. Attack by such agents can reduce the tensile strength, elongation and compression set resistance of the elastomer composition.
• Thermosets refer to non-elastomeric cross-linked materials that become stiff and strong when processed with the aid of a curing agent and heat. Phenolics and 2-part epoxies, fall under this category, for example. Thermoplastic materials are commonly known as plastics because of their relative hardness when compared to elastomers. Typically, thermoplastics are made of long polymer molecules that deform under thermal expansion but have a limited amount of elastic recovery. Thermoplastic materials are typically produced by sintering or melt processing under temperature and pressure. Thermoplastics include polyetheretherketones such as (PEEK), (PEK) and (PEKK), polphenylene sulfide (PPS), polytetrafluoroethylene (Teflon®) and the like.
• For example, the use of PEEK providespolymer host212 with the properties of a high performance semi-crystalline engineering thermoplastic. As compared with standard thermoplastics, PEEK thermoplastics are acceptable for an extremely wide range of applications where good thermal and chemical properties are essential. In particular, PEEK thermoplastics exhibit compatibility with acids (HCl/HF), bases, and both alphatic and aromatic hydrocarbons. Hence, PEEK thermoplastics may be employed in downhole environments that may have caustic chemicals or high-temperature aqueous solutions.
• Nanostructure220 comprises nanoparticles having a scale in the range of approximately 0.1 nanometers to approximately 500 nanometers.Nanostructure220 may be formed by a process including sol-gel synthesis, inert gas condensation, mechanical alloying, high-energy ball milling, plasma synthesis, electrodeposition or the like.Nanostructures220 may include metal oxides, nanoclays, carbon nanostructures and the like.
• Metal oxide nanoparticles include oxides of zinc, iron, titanium, magnesium, silicon, aluminum, cerium, zirconium or the like and equivalents thereof, as well as mixed metal compounds such as indium-tin and the like. In one embodiment, a plasma process is utilized to form metal oxide nanoparticles having a narrow size distribution, nonporous structures and nearly spherical shapes. Nanoclays are naturally occurring, plate-like clay particles such as montmorillonite (MMT) nanoclay. In one embodiment, the nanoclays are exfoliated in the polymer host via a plastic extrusion process. Carbon nanostructures include carbon nanotubes, carbon nanofibers (CNF), nanocarbon blacks and calcium carbonates.
• In one embodiment,nanostructure220 may be formed from polysilane resins (PS)224, as depicted inFIG. 11, polycarbosilane resins (PCS)226, as depicted inFIG. 12, polysilsesquioxane resins (PSS)228, as depicted inFIG. 13, or polyhedral oligomeric silsesquioxane resins (POSS)230, as depicted inFIG. 14, as well as monomers, polymers and copolymers thereof or the like and equivalents thereof. In the formulas presented inFIGS. 11-14, R represents a hydrogen or an alkane, alkenyl or alkynl hydrocarbons, cyclic or linear, with 1-28 carbon atoms, substituted hydrocarbons R—X, aromatics Ar and substituted aromatics Ar—X where X represents halogen, phosphorus or nitrogen containing groups. The incorporation of halogen or other inorganic groups such as phosphates and amines directly into onto these nanoparticles can afford additional improvements to the mechanical properties of the material. For example, the incorporation of halogen group can afford additional heat resistance to the material. These nanostructures may also include termination points, i.e., chain ends, that contain reactive or nonreactive functionalities such as silanols, esters, alcohols, amines or other R groups.
• Preferably,nanostructures220 are integrated withpolymer host material212 prior to curing. In one embodiment,nanostructures220 are integrated intopolymer host material212 by adding or blendingnanostructures220 in a preceramic state withpolymer host material212 such that whennanostructures220 are heated above their decomposition point,nanostructures220 convert into a ceramic. Alternatively,nanostructures220 may be integrated withpolymer host material212 after curing using a deposition process such as spraying.
• Referring next toFIG. 15, a nanocomposite material for use in a downhole environment in accordance with the teachings of the present invention is nanoscopically depicted and generally designated240. One or more additives may be compounded or mixed with the base polymer to modify and enhance desirable properties. For example, a seal element of the present invention may preferably be formed from an elastomeric material that is produced by a curing method that involves compounding or mixing the base polymer with various additive or agents such as graphite, a peroxide curing agent, furnace black, zinc oxide, magnesium oxide, antioxidants, accelerators, plasticizers, processing aids or the like and combinations thereof which modify various properties of the base polymer.
• Use of nanostructures in combination with these additives can further enhance desirable properties. As illustrated, apolymer interphase region242 is defined by polymer host material. An additive244 is associated withpolymer interphase region242. Nanomaterials246-254 stabilize and reinforceinterphase region242 ofnanocomposite240 and, in particular, nanomaterials246-254 reinforce the polymers andcomplement additive244 by strengthening the bonding between the polymers andadditive244.
• Additive244 extends the performance envelope and lifetimes of the polymer material by providing strength to the nanocomposite matrix while preserving the desirable qualities of the nanocomposite. While the additives listed hereinbelow tend to improve certain properties when compounded or mixed with the base polymer ofnanocomposite210, the improvement in one property tends to be counteracted by a reduction in the performance envelope of another property. For example, compounding the base polymer with an additive may result in an increase in the temperature stability of the base polymer but may also result in a reduction in the abrasion resistance of the base polymer or vice versa.Nanocomposite material240 of the present invention, however, overcomes these property trade off problems by integrating the aforementioned nanomaterials into the base polymer either instead of or in addition to other additives.
• Many additives such as powder fillers, fibers, and metals can be used. Powder fillers can be used to drive the total material cost down or to add structural integrity to the material. For example, carbon black is often used as a mechanical reinforcement to improve the strength, stiffness, wear resistance, UV and ozone degradation resistance, and liquid absorption resistance of polymers and in particular, elastomers. The strength can be increased up to 10 times with the addition of carbon black. The structure of carbon black results in isotropic properties and also allows it to bond very well with polymers. Silica powders are also used to reinforce elastomers, add strength and stiffness, and add color. Silicone rubber is commonly made with silica fillers.
• In addition, polymers can be reinforced with a variety of fibers, such as fiberglass, asbestos (obsolete), oriented polymer fibers, and (e.g., Kevlar), for example, to improve the mechanical performance of materials. These fibers can increase the strength, toughness, extrusion resistance, and wear resistance of elastomers while decreasing the ultimate elongation. Metal reinforcements can be in the form of wires, rings, springs, and tubes. Metal reinforcements provide a great deal of structural integrity but can be difficult to bond to some elastomers. In this respect, particular nanomaterials can be employed to bond the polymer to the metal reinformements in order to increase the strength of the polymer.
• As previously alluded to, nanomaterials prevent material failures, such as seal failures, by strengthening the bonding within a polymer and between a polymer and a reinforcer such as a macroscopic reinforcer. By way of example, nanocomposites prevent explosive decompression and the hardening, cracking and softening that occurs to seals over time. Nanomaterials are small enough to fill the voids that liquids and gases enter. Moreover, nanomaterials create strong bonds with the polymer host within these voids. This prevents explosive decompression and the hardening, cracking and softening caused by corrosive chemicals.
• By way of another example, nanomaterials minimize extrusion, nibbling, spiral failures and abrasion, for example. Extrusion and nibbling can occur due to cyclic pressure loading. Extrusion occurs when differential pressure across a seal forces material into an existing extrusion gap between tool components. Spiral failure usually occurs with O-rings that have a long stroke length. Some parts of the ring will slide while other parts roll and are sliced by the edge of the O-ring groove. Abrasion is a common problem with rotary seals or with seals that involve long stroke lengths. Seals can also be abraded while running into or pulling out of the hole if wear ring are not used. With respect to each of these failures the interactions that the nanomaterial forms with the polymer maintain the chemical bonds within the polymer and prevent extrusion, nibbling, spiral failures, and abrasion, which are caused by the decoupling and breaking of bonds within the polymer.
• By way of further example, in existing polymers, over time an elastomer becomes stretched and begins to permanently deform into its new shape. This time dependent lack of elastic recovery can be accelerated with increased temperature and is commonly referred to as compression set. The stiffness is controlled by the crosslink density and increases as the crosslink density increases. As nanomaterials increase the crosslinking density, nanomaterials can extend the life of elastomers significantly.
EXAMPLE
• The mechanical properties, such as tensile strength, elongation, and Young's modulus, for example, of the nanocomposite can be tailored over a wide range for the specific downhole conditions by varying the amount and type of nanostructure incorporated into the polymer host. By way of example, the following table illustrates particular nanostructures integrated into a polymer host by adding or blending the nanostructure in a preceramic state with the polymer host such that the nanostructure when heated above its decomposition point converts into a ceramic. The polymer host used in this example is a polyether block-polyamide copolymer (PEBAX), i.e., a thermoplastic. It should be appreciated however, that similar results would be achieved with other thermopolastics such as polypropylene, polyolefins, nylons, polyethers, polyesters, styrene-butadiene-styrere triblocks, and the like.

  TABLE 1
  	Peek	Breaking	Young's	Melting
  Materials	Stress	Stress	Modulus	Temperature
  (% weight)	(psi)	(in/in)	(psi)	(° C.)

  PEBAX/PCS 80/20	2313	7.0	1894	118
  PEBAX/PS 80/20	2210	9.4	74	118
  PEBAX/PS 50/50	448	3.8	2253	110
  PEBAX 100	2778	8.2	617	119

  
  As illustrated in Table 1, the mechanical properties of the PEBAX material may be greatly improved by the addition of a nanostructure such asPS224 orPCS226. Specifically, the addition of 20% by weight ofPCS226 to the PEBAX approximately triples the Young's Modulus of the PEBAX while maintaining approximately the same breaking stress and melting temperature. Similarly, the addition of 20% by weight ofPS224 to the PEBAX increases the breaking stress. Moreover, the addition of 50% by weight ofPS224 dramatically increases the Young's modulus.
• By way of another example, the nanostructure phenylsilicone improves the stability and heat resistance of polyphenylene ether. In particular, the functionalized epoxy group of the polyphenylene ether reacts with the amino group of the silicon nanostructure to form a nanocomposite that demonstrates improved stability and heat resistance.
• While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.

Claims (38)

1. A seal element for providing a seal between two components in a downhole tool, the seal element comprising:

a polymer host material; and

a nanomaterial integrated with the polymer host material to form a nanocomposite material.

2. The seal element as recited inclaim 1 wherein the seal element comprises a seal selected from the group consisting of O-ring seals, D-seals, T-seals, V-seals, X-seals, flat seals, lip seals, back-up rings, bonded seals and packing elements.

3. The seal element as recited inclaim 1 wherein the polymer host material is selected from the group consisting of elastomers, thermosets and thermoplastics.

4. The seal element as recited inclaim 1 wherein the polymer host material comprises an elastomer selected from the group consisting of NBR, XNBR, HNBR, XHNBR, HXNBR, HSN, EPR, EPDM, FEPM, FKM and FEKM.

5. The seal element as recited inclaim 1 wherein the polymer host material comprises a thermoplastic selected from the group consisting of polphenylene sulfides, polyetheretherketones and tetrafluoroethylenes.

6. The seal element as recited inclaim 1 wherein the nanocomposite material further comprising a reinforcement material selected from the group consisting of powder materials, fiber reinforcement materials and metal reinforcement materials.

7. The seal element as recited inclaim 1 wherein the nanomaterial further comprises nanoparticles having a scale in the range of approximately 0.1 nanometer to approximately 500 nanometers.

8. The seal element as recited inclaim 1 wherein the nanomaterial is selected from the group consisting of metal oxides, nanoclays and carbon nanostructures.

9. The seal element as recited inclaim 1 wherein the nanomaterial further comprises silicon.

10. The seal element as recited inclaim 1 wherein the nanomaterial is selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins and polyhedral oligomeric silsesquioxane resins.

11. The seal element as recited inclaim 1 wherein the polymer host material and the nanomaterial have interfacial interactions selected from the group consisting of copolymerization, crystallization, van der Waals interactions and cross-linking interactions.

12. A downhole tool comprising:

a first component having a groove;

a second component positioned relative to the first component forming a gap therebetween; and

a seal element positioned in the groove and extending across the gap into sealing contact with the second component, the seal element comprising a nanocomposite material.

13. The downhole tool as recited inclaim 12 wherein the seal element is selected from the group consisting of O-ring seals, D-seals, T-seals, V-seals, X-seals, flat seals and lip seals.

14. The downhole tool as recited inclaim 12 wherein the nanocomposite material further comprises a polymer host material and a plurality of nanostructures.

15. The downhole tool as recited inclaim 14 wherein the polymer host material further comprises an elastomer.

16. The downhole tool as recited inclaim 15 wherein the elastomer is selected from the group consisting of NBR, XNBR, HNBR, XHNBR, HXNBR, HSN, EPR, EPDM, FEPM, FKM and FEKM.

17. The downhole tool as recited inclaim 14 wherein the nanostructures further comprise nanoparticles having a scale in the range of approximately 0.1 nanometer to approximately 500 nanometers.

18. The downhole tool as recited inclaim 14 wherein the nanostructures further comprise a material selected from the group consisting of metal oxides, nanoclays and carbon nanostructures.

19. The downhole tool as recited inclaim 14 wherein the nanostructures further comprise silicon.

20. The downhole tool as recited inclaim 14 wherein the nanostructures are selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins and polyhedral oligomeric silsesquioxane resins.

21. The downhole tool as recited inclaim 14 wherein the polymer host material and the nanostructures have interfacial interactions selected from the group consisting of copolymerization, crystallization, van der Waals interactions and cross-linking interactions.

22. The downhole tool as recited inclaim 12 wherein the first component is stationary relative the second component when the downhole tool is in an operational configuration.

23. The downhole tool as recited inclaim 12 wherein the first component and the second component move relative to one another when the downhole tool is in an operational configuration.

24. The downhole tool as recited inclaim 23 wherein the first component and the second component move translationally relative to one another when the downhole tool is in the operational configuration.

25. The downhole tool as recited inclaim 23 wherein the first component and the second component move rotationally relative to one another when the downhole tool is in the operational configuration.

26. The downhole tool as recited inclaim 12 wherein the first component and the second component are tubular components.

27. The downhole tool as recited inclaim 12 wherein the first component is positioned interiorly of the second component.

28. The downhole tool as recited inclaim 12 wherein the first component is positioned exteriorly of the second component.

29. The downhole tool as recited inclaim 12 wherein the first component and the second component form a portion of a device selected from the group consisting of drill bits, mud motors, flow control devices, safety devices, valves, sliding sleeves, telemetry equipment, perforating guns, testing devices and pumps.

30. A seal assembly for providing a seal in a wellbore annulus, the seal assembly comprising:

a generally tubular mandrel; and

a seal element positioned exteriorly of the mandrel, the seal element operable to substantially prevent fluid flow in the wellbore annulus when the seal assembly is in a sealing configuation, the seal element comprising a nanocomposite material.

31. The seal assembly as recited inclaim 30 wherein the nanocomposite material further comprises a polymer host material and a plurality of nanostructures.

32. The seal assembly as recited inclaim 31 wherein the polymer host material further comprises an elastomer.

33. The seal assembly as recited inclaim 32 wherein the elastomer is selected from the group consisting of NBR, XNBR, HNBR, XHNBR, HXNBR, HSN, EPR, EPDM, FEPM, FKM and FEKM.

34. The seal assembly as recited inclaim 31 wherein the nanostructures further comprise nanoparticles having a scale in the range of approximately 0.1 nanometer to approximately 500 nanometers.

35. The seal assembly as recited inclaim 31 wherein the nanostructures further comprise a material selected from the group consisting of metal oxides, nanoclays and carbon nanostructures.

36. The seal assembly as recited inclaim 31 wherein the nanostructures further comprise silicon.

37. The seal assembly as recited inclaim 31 wherein the nanostructures are selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins and polyhedral oligomeric silsesquioxane resins.

38. The seal assembly as recited inclaim 31 wherein the polymer host material and the nanostructures have interfacial interactions selected from the group consisting of copolymerization, crystallization, van der Waals interactions and cross-linking interactions.

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