1. Field of the Invention
This invention relates broadly to Moineau devices in which a helical profiled rotor acts in conjunction with a helical profiled stator as a motor or a pump, and more specifically to the use of polymer materials for such Moineau devices.
2. Related Art
Moineau devices (sometimes referred to as progressive cavity devices) typically include a power section that includes a rotor with a profiled helical outer surface disposed within a stator with a profiled helical inner surface. The helical outer surface of the rotor sealably engages the helical inner surface of the stator to create cavities which progress axially as the rotor is rotated relative to the stator. In a Moineau pump, relative rotation is provided between the stator and the rotor which causes fluids (and possibly solids suspended therein) to be passed through the cavities of the device. In a Moineau motor, a fluid source is provided to the cavities of the device which causes the cavities to progress and induce relative motion between the stator and the rotor. Moineau pumps and motors have many uses. For example, a Moineau motor is often used in hydrocarbon extraction applications for drilling a subterranean well bore by applying drilling mud under pressure to the cavities of the motor, which induces relative motion between the stator and the rotor that is used to power a drill bit for drilling the well bore.
Conventional Moineau devices employ a steel rotor and an elastomeric material bonded to steel for the stator. The elastomeric material of the stator can be natural rubber, G.R.S., Neoprene, Butyl and Nitrile rubbers, soft PVC, fluoroelastomers, etc. The elastomeric material of the stator is required to be soft enough to maintain the sealed cavity, yet be hard enough to withstand the abrasive wear from the working contact between the rotor and the stator.
The present invention provides for materials and methods of manufacture for a Moineau device. The materials comprise a nanocomposite which includes a polymeric matrix with carbon nanotubes (e.g., single-walled carbon nanotubes, multi-walled carbon nanotubes) dispersed therein. In the preferred embodiment, the nanocomposite is part of the stator of the Moineau device and defines the profiled helical inner surface that sealably engages the rotor of the Moineau device. The nanocomposite can also be used to realize other components of the Moineau device, such as a portion of the rotor of the device.
According to one aspect of the invention, the carbon nanotubes of the nanocomposite material provide good thermal conduction. Thus, in portions of the stator and/or rotor of the Moineau device where local temperatures can increase and accelerate material degradation, the nanocomposite material is used such that the thermal conduction of the nanocomposite material will counteract the local build-up of heat. As a result, the Moineau device will be maintained at a temperature closer to average temperature of the environment and therefore will maintain better mechanical properties over time. The operational lifetime of the nanocomposite structure is also improved.
According to another aspect of the invention, the carbon nanotubes of the nanocomposite material provide improved mechanical properties (such as stiffness, tensile strength, visco-elasticity (e.g., heat dissipation due to physical interactions between the carbon nanotubes of the nanocomposite material)) of the stator and/or rotor of the Moineau device.
In another aspect, a method of manufacturing a stator of a Moineau device disposes a mandrel with a desired helical profile within a cylindrical casing. A void disposed between the mandrel and the cylindrical casing is filled with a nanocomposite material which includes a polymeric matrix with carbon nanotubes dispersed therein. The nanocomposite is cured. Subsequent to curing, the mandrel is removed from within the cylindrical casing. A bonding agent can be applied to the internal surface of the cylindrical casing to aid in bonding the nanocomposite material to the cylindrical casing. A release agent can be applied to the mandrel to aid in releasing the mandrel from the nanocomposite material. The nanocomposite material can be molded as part of a support structure underlying a resilient liner. In an alternate embodiment, the nanocomposite material can be molded as part of a resilient liner that defines the profiled helical inner surface of the stator.
In accordance with the present invention, the stator 20 of
The polymeric matrix of the nanocomposite material can be realized from one or more polymers selected from natural and synthetic polymers, including those listed in ASTM D1600-92, “Standard Terminology for Abbreviated Terms Relating to Plastics,” and ASTM D1418 for nitrile rubbers, blends of natural and synthetic polymers, and layered versions of polymers, wherein individual layers may be the same or different in composition and thickness. The term matrix as used herein is not meant to exclude any particular form or morphology for the polymeric component and is used merely as a term of convenience in describing the apparatus of the invention. The polymeric matrix of the nanocomposite material can include other materials, such as, but not limited to, fillers (e.g., metal fillers, ceramic fillers, silica fillers, carbon black), plasticizers, and fibers. The polymeric matrix may comprise one or more thermoplastic polymers, such as polyolefins, polyimides, polyesters, polyetheretherketones (PEEK), thermoplastic polyurethanes and polyurea urethanes, copolymers, and blends thereof, and the like; one or more thermoset polymers, such as phenolic resins, epoxy resins, and the like, and/or one or more elastomers (including natural and synthetic rubbers), and combinations thereof.
The polymeric matrix of the nanocomposite material can be realized from one or more elastomers. An elastomer as used herein is a generic term for a substance emulating natural rubber in that it stretches under tension, has a high tensile strength, retracts rapidly, and substantially recovers its original dimensions. Elastomers are made with polymer chains with different lengths. Each chain is typically made of thousands of units (monomers). Cohesion is provided by molecular entanglements and physical bonds between chains. Elasticity is provided by crosslinking, which are chemical bonds typically involving sulfur or peroxides. The term includes natural and man-made elastomers, and the elastomer may be a thermoplastic elastomer or a non-thermoplastic elastomer. The term includes blends (physical mixtures) of elastomers, as well as copolymers, terpolymers, and multi-polymers. Examples include ethylene-propylene-diene polymer (EPDM), various nitrile rubbers which are copolymers of butadiene and acrylonitrile such as Buna-N (also known as standard nitrile and NBR), carboxylated high-acrylonitrile butadiene copolymers (XNBR), and hydrogenated versions of these copolymers (HNBR). Other useful elastomers include polyvinylchloride-nitrile butadiene (PVC-NBR) blends, chlorinated polyethylene (CM), chlorinated sulfonate polyethylene (CSM), aliphatic polyesters with chlorinated side chains such as epichlorohydrin homopolymer (CO), epichlorohydrin copolymer (ECO), and epichlorohydrin terpolymer (GECO), polyacrylate rubbers such as ethylene-acrylate copolymer (ACM), ethylene-acrylate terpolymers (AEM), EPR, elastomers of ethylene and propylene, sometimes with a third monomer, such as ethylene-propylene copolymer (EPM), ethylene vinyl acetate copolymers (EVM), fluorocarbon polymers (FKM), copolymers of poly(vinylidene fluoride) and hexafluoropropylene (VF2/HFP), terpolymers of poly(vinylidene fluoride), hexafluoropropylene, and tetrafluoroethylene (VF2/HFP/TFE), terpolymers of poly(vinylidene fluoride), polyvinyl methyl ether and tetrafluoroethylene (VF2/PVME/TFE), terpolymers of poly(vinylidene fluoride), hexafluoropropylene, and tetrafluoroethylene (VF2/HPF/TFE), terpolymers of poly(vinylidene fluoride), tetrafluoroethylene, and propylene (VF2/TFE/P), perfluoroelastomers such as tetrafluoroethylene perfluoroelastomers (FFKM), highly fluorinated elastomers (FEPM), butadiene rubber (BR), polychloroprene rubber (CR), polyisoprene rubber (IR), polynorbornenes, polysulfide rubbers (OT and EOT), polyurethanes (AU) and (EU), silicone rubbers (MQ), vinyl silicone rubbers (VMQ), fluoromethyl silicone rubber (FMQ), fluorovinyl silicone rubbers (FVMQ), phenylmethyl silicone rubbers (PMQ), styrene-butadiene rubbers (SBR), copolymers of isobutylene and isoprene known as butyl rubbers (IIR), brominated copolymers of isobutylene and isoprene (BIIR) and chlorinated copolymers of isobutylene and isoprene (CIIR).
Thermoplastic elastomers are generally the reaction product of a low equivalent molecular weight polyfunctional monomer and a high equivalent molecular weight polyfunctional monomer, wherein the low equivalent weight polyfunctional monomer is capable, on polymerization, of forming a hard segment (and, in conjunction with other hard segments, crystalline hard regions or domains) and the high equivalent weight polyfunctional monomer is capable, on polymerization, of producing soft, flexible chains connecting the hard regions or domains. Thermoplastic elastomers differ from thermoplastics and elastomers in that thermoplastic elastomers, upon heating above the melting temperature of the hard regions, form a homogeneous melt which can be processed by thermoplastic techniques (unlike elastomers), such as injection molding, extrusion, blow molding, and the like. Subsequent cooling leads again to segregation of hard and soft regions resulting in a material having elastomeric properties, however, which does not occur with thermoplastics. Commercially available thermoplastic elastomers suitable for realizing the polymeric matrix of the nanocomposite include segmented polyester thermoplastic elastomers, segmented polyurethane thermoplastic elastomers, segmented polyamide thermoplastic elastomers, blends of thermoplastic elastomers and thermoplastic polymers, and ionomeric thermoplastic elastomers.
The polymeric matrix of the nanocomposite material can also be realized from a thermoplastic material. A thermoplastic material is a polymeric material (preferably, an organic polymeric material) that softens and melts when exposed to elevated temperatures and generally returns to its original condition, i.e., its original physical state, when cooled to ambient temperatures. During manufacturing, the thermoplastic material may be heated above its softening temperature, and preferably above its melting temperature, to cause it to flow and form a desired shape. After the desired shape is formed, the thermoplastic substrate is cooled and solidified. In this way, thermoplastic materials (including thermoplastic elastomers) can be molded into various shapes and sizes. Moldable thermoplastic materials that may be used are those having a high melting temperature, good heat resistant properties, and good toughness properties. Examples of thermoplastic materials suitable for use in the polymeric matrix of the nanocomposite material include PEEK, polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene (PES), polyphenylene sulfide (PPS). Other polymeric materials suitable for use in the polymeric matrix of the nanocomposite material include block copolymers (e.g., styrene-butadiene-styrene (SBS) rubber, copolyesters and polyureathanes), thermoplastic rubber combinations (e.g., ethylene propylene diene monomer (EPDM) rubber and polyphenylene ether (PPE), nitrile-butadiene rubber (NBR) and polyvinyl chloride, butyl rubber (IIR) and polypropylene (PP)).
The polymeric matrix of the nanocomposite material can also be realized from a thermoset material. A thermoset material is a polymeric material that hardens when exposed to elevated temperatures or otherwise cured. Once the material has been cured, it generally does not go back to its original state nor does it melt when reheated. Examples of thermoset materials suitable for use in the polymeric matrix of the nanocomposite include phenolic resins, epoxy resins, phenoxy, phenolic, ester, polyurethane, polyurea, and the like. Thermoset molding compositions known in the art can also be used, which generally include thermosetting resins containing inorganic fillers and/or fibers. Upon heating, thermoset monomers initially exhibit viscosities low enough to allow for melt processing and molding of an article from the filled monomer composition. Upon further heating, the thermosetting monomers react and cure to form hard resins with high stiffness. Non-limiting examples of suitable epoxies include the High Temperature Mould maker (C-1) liquid epoxy or other metal filled epoxies sold commercially by ITW-Devcon of Rushden, UK. Metal fillers typically used are steel, aluminum and/or titanium. Another non-limiting example of a suitable epoxy is the polycarbon fiber ceramic filled Novolac™ resin sold commercially by Protech Centreform Ltd. of Aberdeen, Scotland.
For many applications, the polymeric matrix of the nanocomposite can be cross-linked in order to limit creep induced by stresses during device operation. Alternatively, the polymeric matrix of the nanocomposite can be a semi-crystalline polymer with a high degree of crystallinity.
The stator 100 is preferably formed by dispersing carbon nanotubes within a polymeric matrix by mixing to form the nanocomposite material. A bonding agent can be applied to the internal wall 106 of the cylindrical casing 101 (
The stator 200 is preferably formed by dispersing carbon nanotubes within a polymeric matrix by mixing to form the nanocomposite material. A bonding agent can be applied to the internal wall of the cylindrical casing 201. A mandrel (not shown) is coated with a thin liner 203. The coated mandrel is disposed within the cylindrical casing 201. The mandrel is preferably realized from steel or other suitable material. The coated mandrel is used as a male mold core for molding the nanocomposite support structure 202 to the coated mandrel. A release agent can be applied to the outer surface of the mandrel before it is coated with the liner 203. The release agent avoids bonding of the nanocomposite/liner structure to the mandrel. The nanocomposite material is added to the void between the coated mandrel and the cylindrical casing 201 and then cured to form the nanocomposite support structure 202. The mandrel is released from the liner 203 (and the underlying nanocomposite support structure 202) and then removed from inside the cylindrical casing 201. The material of the liner 203 is a resilient material such as an elastomer and can be a nanocomposite elastomer if desired.
In alternate embodiments, it is possible to include a thin layer of metal (e.g., metallic foil) as the interface of the stator that sealably engages the rotor of the Moineau devices described herein. This configuration can be used with rotors that employ an elastomeric material for sealably engaging the interface of the stator. This configuration can be realized in conjunction with the manufacturing steps described above with respect to
In yet other embodiments, the nanocomposite structures described herein can be employed as part of the rotor of a Moineau device and thus provide improved mechanical properties (such as stiffness, tensile strength, visco-elasticity) as well as improved thermal conduction that minimizes localized high temperatures zones in the rotor of the Moineau device. For example,
Non-limiting examples of suitable bonding agents as described above include Cilbond™ line of bonding agents sold commercially by Chemical Innovations Limited of Lancashire, UK, the Chemlock™ line of bonding agents sold commercially by Lord Corporation of Cary, N.C., and the Chemosil™ line of bonding agents sold commercially by the Henkel Corporation of Dusseldorf, DE.
Non-limiting examples of suitable release agents as described above include the TraSys™ line of release agents sold commercially by E.I. du Pont de Nemours and Company of Wilmington, Del., and the Apticote™ 460M line of release agents sold commercially by Poeton Industries Limited of Gloucester, UK.
Additives can be added to the nanocomposite material to assist in binding the elastomer liners described above to the nanocomposite material. Non-limiting examples of such additives include zinc diacrylate (ZDA), zinc dimethacrylate (ZDMA), zinc monomethacrylate (ZMMA), the Duralink HTS™ line of additive sold commercially by Flexsys of Akron, Ohio, and the Ricobond 1731™ line and ZDA™ line of additive sold commercially by Sartomer Co. of Exton, Pa.
Similarly, an interlayer can be disposed between the support structures and elastomeric liners described above in order to assist in binding the elastomeric liners. Non-limiting examples of such interlayers include Poly BD 2035 thermoplastic polyurethane (TPU) resin sold commercially by Sartomer Co. of Exton, Pa.
There have been described and illustrated herein several embodiments of components of a Moineau device and methods of manufacturing same. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while a particular Moineau motor configuration has been disclosed, it will be appreciated that the inventions described herein can be used for Moineau pumps as well. Furthermore, while the invention is described in relation to a Moineau motor for drilling a borehole, it will be understood that the invention can be used in Moineau devices for other applications. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.
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