Title:
Nano particle reinforced polymer element for stator and rotor assembly
Kind Code:
A1


Abstract:
A nano particle reinforced polymer element of a stator and rotor assembly for a power section of a positive displacement fluid motor or a progressive cavity pump. Nano-sized particles are blended with an uncured polymer to improve the physical and chemical properties of the polymer. The use of nano-sized particles reduces the quantity of reinforcement material required to manufacture the polymer for the stator and rotor assembly and lowers the viscosity of the uncured polymer to improve manufacturing characteristics. The use of chemically functionalized nano particles improves the chemical and physical characteristics of the polymer.



Inventors:
Slay, Jeremy Buc (Fort Worth, TX, US)
Ray, Thomas Wayne (Tyler, TX, US)
Application Number:
12/002710
Publication Date:
06/18/2009
Filing Date:
12/18/2007
Assignee:
HALLIBURTON ENERGY SERVICES, INC., A DELAWARE CORPORATION (Houston, TX, US)
Primary Class:
Other Classes:
418/61.3, 418/178
International Classes:
E21B4/02; F01C1/107; F04C2/107; F04C15/00; F04C18/107
View Patent Images:
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Primary Examiner:
DAVIS, MARY ALICE
Attorney, Agent or Firm:
LAWRENCE R. YOUST (Dallas, TX, US)
Claims:
1. A stator and rotor assembly comprising: a stator having an inner surface; an inner core disposed within the inner surface of the stator and defining a cavity, the inner core comprising a polymer material having a plurality of nano particles integrated therein; and a rotor disposed within the cavity, operable to rotate within the inner core.

2. The stator and rotor assembly as recited in claim 1, wherein the stator further comprises a substantially cylindrical inner surface.

3. The stator and rotor assembly as recited in claim 1, wherein the rotor further comprises a spiral rotor.

4. The stator and rotor assembly as recited in claim 1, wherein the rotor further comprises a helical rotor.

5. The stator and rotor assembly as recited in claim 1, wherein the stator and rotor assembly is part of a positive displacement fluid motor.

6. The stator and rotor assembly as recited in claim 1, wherein the stator and rotor assembly is part of a progressive cavity pump.

7. The stator and rotor assembly as recited in claim 1, wherein the polymer material is selected from an elastomer, a thermoset and a thermoplastic.

8. The stator and rotor assembly as recited in claim 1, wherein the polymer material further comprises an elastomer selected from the group consisting of nitrile, carboxylated acrylonitrile butadiene, hydrogenated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, hydrogenated carboxylated acrylonitrile butadiene, tetrafluoroethylene and propylene, perfluoroelastomers, ethylene propylene, ethylene propylene diene, polychloroprene rubber, natural rubber, polyether eurethane and styrene butadiene rubber.

9. The stator and rotor assembly as recited in claim 1, wherein the polymer material further comprises a thermoplastic selected from the group consisting of polyphenylene sulfides, polyetherketone-ketones, polyetheretherketones, polyetherketones and polytetrafluorethylenes.

10. The stator and rotor assembly as recited in claim 1, wherein the nano particles further comprise nano clays.

11. The stator and rotor assembly as recited in claim 1, wherein the nano particles further comprise carbon nano fibers.

12. The stator and rotor assembly as recited in claim 1, wherein the nano particles are selected from the group consisting of single wall carbon nano tubes, multi-wall carbon nano tubes and carbon nano tube arrays.

13. The stator and rotor assembly as recited in claim 1, wherein the nano particles are selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins and polyhedral oligomeric silsesquioxane resins.

14. The stator and rotor assembly as recited in claim 1, wherein the nano particles are in the range from approximately 0.1 nanometers to approximately 500 nanometers, at the least dimension.

15. The stator and rotor assembly as recited in claim 1, wherein the nano particles are in the range from approximately 0.5 nanometers to approximately 100 nanometers, at the least dimension.

16. The stator and rotor assembly as recited in claim 1, wherein the nano particles are chemically functionalized.

17. A stator and rotor assembly comprising: a stator having an inner surface; an inner core disposed within the inner surface of the stator and defining a cavity, the inner core comprising a polymer host material having a plurality of nano structures integrated therein, the nano structures selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins, polyhedral oligomeric silsesquioxane resins, monomers, polymers and copolymers of any of these resins, carbon nanotubes and any of the preceding nano structures that are chemically functionalized; and a rotor disposed within the cavity, operable to rotate within the inner core.

18. The stator and rotor assembly as recited in claim 17, wherein the stator further comprises a substantially cylindrical inner surface.

19. The stator and rotor assembly as recited in claim 17, wherein the rotor further comprises a spiral rotor.

20. The stator and rotor assembly as recited in claim 17, wherein the rotor further comprises a helical rotor.

21. The stator and rotor assembly as recited in claim 17, wherein the stator and rotor assembly is part of a positive displacement fluid motor.

22. The stator and rotor assembly as recited in claim 17, wherein the stator and rotor assembly is part of a progressive cavity pump.

23. The stator and rotor assembly as recited in claim 17, wherein the polymer material is selected from an elastomer, a thermoset and a thermoplastic.

24. The stator and rotor assembly as recited in claim 17, wherein the polymer material further comprises an elastomer selected from the group consisting of nitrile, carboxylated acrylonitrile butadiene, hydrogenated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, hydrogenated carboxylated acrylonitrile butadiene, tetrafluoroethylene and propylene, perfluoroelastomers, ethylene propylene, ethylene propylene diene, polychloroprene rubber, natural rubber, polyether eurethane and styrene butadiene rubber.

25. A stator and rotor assembly comprising: a stator having an inner surface; an inner core disposed within the inner surface of the stator and defining a cavity, the inner core comprising an elastomer host material and chemically functionalized carbon nanotubes; and a rotor disposed within the cavity, operable to rotate within the inner core.

26. The downhole tool system as recited in claim 25 wherein the elastomer host material further comprises a copolymer of acrylonitrile and butadiene.

27. The downhole tool system as recited in claim 25 wherein the elastomer host material is selected from the group consisting of acrylonitrile butadiene, carboxylated acrylonitrile butadiene, hydrogenated acrylonitrile butadiene, highly saturated nitrile, carboxylated hydrogenated acrylonitrile butadiene, hydrogenated carboxylated acrylonitrile butadiene, ethylene propylene, ethylene propylene diene, tetrafluoroethylene and propylene, fluorocarbon and perfluorocarbon.

28. The downhole tool system as recited in claim 25 wherein the elastomer host material and the nanomaterial have interfacial interactions.

29. The downhole tool system as recited in claim 25 wherein the nanomaterial structurally complements the elastomer host material.

30. The downhole tool system as recited in claim 25 wherein the nanomaterial chemically complements the elastomer host material.

31. The downhole tool system as recited in claim 25 wherein the nanomaterial structurally and chemically complements the elastomer host material.

32. The stator and rotor assembly as recited in claim 25 wherein the stator and rotor assembly is part of a positive displacement fluid motor.

33. The stator and rotor assembly as recited in claim 25 wherein the stator and rotor assembly is part of a progressive cavity pump.

34. A stator and rotor assembly comprising: a stator having an inner surface and defining a cavity; a rotor disposed within the cavity, operable to rotate within the cavity; and a polymer layer disposed exteriorly on the rotor, the polymer layer having a plurality of nano particles integrated therein.

35. The stator and rotor assembly as recited in claim 34, wherein the stator and rotor assembly is part of a positive displacement fluid motor.

36. The stator and rotor assembly as recited in claim 34, wherein the stator and rotor assembly is part of a progressive cavity pump.

37. The stator and rotor assembly as recited in claim 34, wherein the polymer layer is formed from a material selected from an elastomer, a thermoset and a thermoplastic.

38. The stator and rotor assembly as recited in claim 34, wherein the polymer layer is formed from an elastomer selected from the group consisting of nitrile, carboxylated acrylonitrile butadiene, hydrogenated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, hydrogenated carboxylated acrylonitrile butadiene, tetrafluoroethylene and propylene, perfluoroelastomers, ethylene propylene, ethylene propylene diene, polychloroprene rubber, natural rubber, polyether eurethane and styrene butadiene rubber.

39. The stator and rotor assembly as recited in claim 34, wherein the polymer layer is formed from a thermoplastic selected from the group consisting of polyphenylene sulfides, polyetherketone-ketones, polyetheretherketones, polyetherketones and polytetrafluorethylenes.

40. The stator and rotor assembly as recited in claim 34, wherein the nano particles further comprise carbon nano fibers.

41. The stator and rotor assembly as recited in claim 34, wherein the nano particles are selected from the group consisting of single wall carbon nano tubes, multi-wall carbon nano tubes and carbon nano tube arrays.

42. The stator and rotor assembly as recited in claim 34, wherein the nano particles are selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins and polyhedral oligomeric silsesquioxane resins.

43. The stator and rotor assembly as recited in claim 34, wherein the nano particles are chemically functionalized.

44. A stator and rotor assembly comprising: a stator having an inner surface and defining a cavity; a rotor disposed within the cavity, operable to rotate within the cavity; and a polymer layer disposed exteriorly on the rotor, the polymer layer having a plurality of nano particles integrated therein, the nano particles selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins, polyhedral oligomeric silsesquioxane resins, monomers, polymers and copolymers of any of these resins, carbon nanotubes and any of the preceding nano structures that are chemically functionalized.

45. A stator and rotor assembly comprising: a stator having an inner surface and defining a cavity; a rotor disposed within the cavity, operable to rotate within the cavity; and a elastomer layer disposed exteriorly on the rotor, the elastomer layer having a plurality of chemically functionalized carbon nanotubes integrated therein.

46. A stator and rotor assembly comprising: a stator having an inner surface with a polymer layer disposed thereon defining a cavity; and a rotor disposed within the cavity and operable to rotate within the cavity, the rotor having a polymer layer disposed exteriorly thereon; wherein the polymer layer of the stator and the polymer layer of the rotor each have a plurality of nano particles integrated therein.

47. The stator and rotor assembly as recited in claim 46, wherein the stator and rotor assembly is part of a positive displacement fluid motor.

48. The stator and rotor assembly as recited in claim 46, wherein the stator and rotor assembly is part of a progressive cavity pump.

49. The stator and rotor assembly as recited in claim 46, wherein the polymer layer is formed from a material selected from an elastomer, a thermoset and a thermoplastic.

50. The stator and rotor assembly as recited in claim 46, wherein the polymer layer is formed from an elastomer selected from the group consisting of nitrile, carboxylated acrylonitrile butadiene, hydrogenated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, hydrogenated carboxylated acrylonitrile butadiene, tetrafluoroethylene and propylene, perfluoroelastomers, ethylene propylene, ethylene propylene diene, polychloroprene rubber, natural rubber, polyether eurethane and styrene butadiene rubber.

51. The stator and rotor assembly as recited in claim 46, wherein the polymer layer is formed from a thermoplastic selected from the group consisting of polyphenylene sulfides, polyetherketone-ketones, polyetheretherketones, polyetherketones and polytetrafluorethylenes.

52. The stator and rotor assembly as recited in claim 46, wherein the nano particles further comprise carbon nano fibers.

53. The stator and rotor assembly as recited in claim 46, wherein the nano particles are selected from the group consisting of single wall carbon nano tubes, multi-wall carbon nano tubes and carbon nano tube arrays.

54. The stator and rotor assembly as recited in claim 46, wherein the nano particles are selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins and polyhedral oligomeric silsesquioxane resins.

55. The stator and rotor assembly as recited in claim 46, wherein the nano particles are chemically functionalized.

56. A stator and rotor assembly comprising: a stator having an inner surface with a polymer layer disposed thereon defining a cavity; and a rotor disposed within the cavity and operable to rotate within the cavity, the rotor having a polymer layer disposed exteriorly thereon; wherein the polymer layer of the stator and the polymer layer of the rotor each have a plurality of nano particles integrated therein, the nano particles selected from the group consisting of polysilane resins, polycarbosilane resins, polysilsesquioxane resins, polyhedral oligomeric silsesquioxane resins, monomers, polymers and copolymers of any of these resins, carbon nanotubes and any of the preceding nano structures that are chemically functionalized.

57. A stator and rotor assembly comprising: a stator having an inner surface with a polymer layer disposed thereon defining a cavity; and a rotor disposed within the cavity and operable to rotate within the cavity, the rotor having a polymer layer disposed exteriorly thereon; wherein the polymer layer of the stator and the polymer layer of the rotor each have a plurality of chemically functionalized carbon nanotubes integrated therein.

Description:

FIELD OF THE INVENTION

This invention relates, in general, to a polymer element of a stator and rotor assembly for power sections of positive displacement downhole fluid motors and progressive cavity pumps and, in particular, to an improved polymer element of a stator or rotor element comprised of a nano particle reinforced polymer internally disposed in a stator lining or disposed as a uniform compliant layer along a rotor surface.

BACKGROUND OF THE INVENTION

Without limiting the scope of the present invention, its background will be described with reference to stator and rotor assemblies of power sections of positive displacement fluid motors and progressive cavity pumps, as examples.

A typical power section of a positive displacement fluid motor comprises a helical-shaped steel rotor that turns rotatably about the centerline of a polymer-lined stator and rotor assembly. A typical stator is a steel tube, lined with a bonded polymer with a helical-shaped inner cavity. High pressure fluid flows through the power section of the positive displacement fluid motor causing the rotor to turn rotatably within the stator. The positive displacement fluid motor converts the hydraulic energy of high pressure fluid to mechanical energy in the form of torque output at the rotor; for example, to turn a drill bit.

The rotor is typically a steel helix with a circular cross section with a smooth hard surface for wear resistance. The rotor is disposed inside the stator and a plurality of cavities defined by a seal plane between the rotor and the helical curve of the polymer core of the stator. As the rotor turns inside the stator, the seal plane between the rotor surface and the polymer lining of the stator rotates around the centerline of the stator, advancing the cavities lengthwise along the stator and rotor assembly. Each of the cavities is sealed from adjacent cavities by the seal plane.

The pressure differential that may be sustained across an individual stage of a power section is improved by maintaining a compression interference between the rotor and the stator.

Slip of the power section occurs when high pressure fluid bypasses the interface between the rotor and the stator without producing a resultant rotational force in the rotor. Slip results in speed and power reduction of a power section until, at some point, the power section stalls, allowing substantially all fluid to bypass the interface between the rotor and the stator with no resultant rotation produced by the power section.

Progressive cavity pumps, also known as progressing cavity pumps or eccentric screw pumps, are typically comprised of a helical steel rotor that turns rotatably within a helical-shaped, polymer-lined stator.

The rotor is typically turned by a mechanical means, such as a motor or subassembly of a drill string. As the rotor turns, the interface between the rotor and the stator rotates around the centerline of the stator, advancing the cavities lengthwise along the stator to force the contents of the cavities through the stages of the pump.

Failure of the polymer element of a power section of a positive displacement fluid motor or a progressive cavity pump typically occurs due to high mechanical loading, polymer fatigue, incompatibility of the fluid and polymer, or high temperature effects on the polymer element. Failure may be associated with a reduction in the performance of the polymer element or with catastrophic failure.

Mechanical failure of the polymer element occurs when the polymer is subject to conditions that exceed the critical strain limit or when the polymer is subject to excessive cyclic loading.

Excessive polymer temperatures generally result from high downhole temperature, hysteresis heat buildup caused by repeated flexing of the polymer by the lobes rotor and pressurized fluid or a combination and may lead to failure of the polymer element or the bond between the polymer and the metal surface of a stator and rotor assembly.

Excessive operating temperature may cause expansion of the polymer that increases the compressive interference between the rotor and the stator, further increasing hysteresis heat generation and wear.

Certain chemicals may react with the polymer element of the stator and rotor assembly and cause degradation of the polymer or the bond between the polymer and the metal surface by weakening the molecular bonding of the polymer. For example, synthetic oils or aromatic compounds found in drilling fluids and drilling fluids buffered with chemicals or composed of high alkalinity brine solutions may cause degradation of the polymer.

Polymer elements of stators are typically manufactured with elastomer compounds comprised of a nitrile-base polymer, reinforcing materials, curatives, accelerators, and plasticizers.

Stators are typically manufactured by an injection molding process that introduces a relatively high viscosity, uncured polymer compound into an annular space between a mold and the inner wall of the stator housing. It is preferred that the polymer element of the stator lining is formed evenly and uniformly to avoid inconsistent thickness of the polymer that may cause excessive flexure of the rotor and excessive stress in the polymer.

Uniform thickness of the polymer element of the stator may be difficult to achieve due to the length of the stator housing into which the uncured polymer is injected and the relatively high viscosity of the uncured polymer.

Therefore, need exists for an improved polymer compound for a stator and rotor assembly for a power section of a positive displacement fluid motor or a progressive cavity pump that has a high resistance to heat and abrasion, a low coefficient of friction, high durability, sustains repeated stress and strain loading without premature failure, and is resistant to chemical interaction. Additionally, need exists for a polymer for a stator or rotor for a power section of a positive displacement fluid motor or a progressive cavity pump that has a reduced uncured viscosity to allow for improved injection molding of a polymer element in a stator housing or molding onto the surface of a rotor.

SUMMARY OF THE INVENTION

While the stator and rotor assembly and the method of manufacturing the present invention are discussed in the context of a positive displacement fluid motor and a progressive cavity pump, it will be appreciated that the present invention is also applicable to other systems that require repetitive flexure of polymers.

The present invention discloses a stator and rotor assembly of a power section of a positive displacement fluid motor or a progressive cavity pump that includes a polymer element wherein the polymer is a polymer matrix reinforced with nano-sized particles to create a nano composite material with improved mechanical, thermal, physical, chemical, and processing properties.

The polymer element may be manufactured from a nano particle polymer composite that includes a polymer host and one or more of a plurality of nano-sized structures. Introduction of nano particles to the uncured polymer may improve the physical properties of the polymer by reducing processing viscosity, improving impact strength, improving stress relaxation resistance, improving compression set properties, increasing tear strength, reducing creep, increasing resistance to thermal and hysteresis failure, and improving resistance to chemical degradation of the polymer.

The polymer host material may be polymers, including but not limited to, elastomers, thermosets, or thermoplastics.

The polymer host material may be an elastomer, such as nitrile, a copolymer of acrylonitrile and butadiene (NBR), or carboxylated acrylonitrile butadiene (XNBR), or hydrogenated acrylonitrile butadiene (HNBR), commonly referred to as highly saturated nitrile (HSN), or carboxylated hydrogenated acrylonitrile butadiene (XHNBR), or hydrogenated carboxylated acrylonitrile butadiene (HXNBR).

The polymer host material may be a flurocarbon (FKM), such as tetrafluoroethylene and propylene (FEPM), or perfluoroelastomer (FFKM).

The polymer host material may also be polychloroprene rubber (CR), natural rubber (NR), polyether eurethane (EU), styrene butadiene rubber (SBR), ethylene propylene (EPR), or ethylene propylene diene (EPDM) or similar elastomers.

The polymer host material may be a thermoplastic, such as polyphenylene sulfide (PPS), polyetherketone-ketone (PEKK), polyetheretherketone (PEEK), polyetherketone (PEK), polytetrafluorethylene (PTFE) or polysulphones (PSU).

The nano structures of the nano composite material may include nano-sized particles approximately 0.1 nanometers to approximately 500 nanometers in the smallest dimension. Nano structures may be from a variety of shapes, such as plates, spheres, cylinders, tubes, fibers, three-dimensional structures, linear molecules, molecular rings, branched molecules and crystalline, amorphous, or symmetric shapes.

Nano particles may be from a variety of materials, such as carbon, silica, calcium, calcium carbonate, inorganic clays, or minerals. The nano structures may be formed from materials, such as nano clays, carbon nano fibers, carbon nano tubes or nano arrays.

The polymer host material and the nano structures may interact via interfacial interactions, such as co-polymerization, crystallization, van der Waals interactions, covalent bonds, ionic bonds, and cross-linking interactions. The interfacial interactions may be improved by chemical functionalization of the nano particles.

Incorporation of nano particles in the polymer improves the particle reinforced polymer matrix by reducing processing viscosity, improving impact strength, improving stress relaxation resistance, improving compression set properties, increasing tear strength, increasing resistance to thermal and hysteresis, reducing heat buildup failure, increasing thermal conductivity, reducing creep, improving resilience and abrasion resistance, and improving resistance to chemical degradation of the polymer.

Nano particle reinforced polymers generally require lesser amounts of filler material than traditional fillers to achieve comparable physical properties. The lesser amount of nano material required to reinforce a cured polymer has a concomitant effect of lowering the uncured viscosity of the polymer and thereby improving the ability to manufacture longer and thinner profiles of polymer stator elements and improving physical properties at elevated temperatures.

In another aspect, the nano particle composite structures may be chemically functionalized to enhance the effective surface area of the composite structure and improve the availability of potential chemical reactions or catalysis sites for chemical functional groups on the nano composite structure and increase the interaction between the polymer matrix and the nano particles.

In an alternate embodiment, the inner surface of the stator may be a helical curve-shaped surface with a plurality of lobes dispersed longitudinally along the inner surface of the stator, and the rotor may be a steel helix coated with a uniform layer of compliant polymer of sufficient thickness to hydraulically engage the helical curve-shaped surface of the stator.

In another aspect, the present invention is directed to a method for forming a stator assembly of a power section of a positive displacement drill motor or a progressive cavity pump that comprises injection molding a nano particle reinforced polymer comprised of a polymer host material and one or more nano-sized structures into an annular area between a mold disposed inside a metal stator housing and the stator housing and curing the elastomer.

In an alternate embodiment, the method comprises steps that include coating a rotor with a nano particle reinforced polymer layer of sufficient uniform thickness to hydraulically engage a helical curve-shaped surface of the stator housing.

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 an elevation view of a stator and rotor assembly comprised of a stator housing, a contoured metal rotor disposed internally in the stator housing and a helically-lobed polymer element lining the stator housing according to an embodiment of the present invention;

FIG. 2 is a cross section illustration of a contoured metal rotor disposed internally in a stator housing, said housing having an improved polymer element lining the stator housing according to an embodiment of the present invention;

FIG. 3 is a cross section illustration of a contoured metal rotor disposed internally in a stator housing, said rotor having an improved polymer layer that engages the helical curve-shaped surface of the stator housing;

FIG. 4 is a schematic illustration of a nano particle composite polymer material comprised of a polymer host material and interlinked nano particles according to an embodiment of the present invention;

FIG. 5 is a schematic illustration of a nano particle composite polymer material comprised of a polymer host material and interlinked nano tubes or nano fibers according to an embodiment of the present invention;

FIG. 6 is a schematic illustration of a single-wall carbon nano tube;

FIG. 7 is a schematic illustration of a multi-wall carbon nano tube;

FIG. 8 is a schematic illustration of a single-wall carbon nano tube imbedded in a polymer host material and interlinked nano particles according to an embodiment of the present invention;

FIG. 9 is a schematic illustration of a nano particle composite polymer material comprising a polymer host material and a nanostructure according to an embodiment of the present invention;

FIG. 10 is a schematic illustration of a silicon-based nanostructure according to an embodiment of the present invention;

FIG. 11 is a schematic illustration of a silicon-based nanostructure according to an embodiment of the present invention;

FIG. 12 is a schematic illustration of a silicon-based nanostructure according to an embodiment of the present invention;

FIG. 13 is a schematic illustration of a silicon-based nanostructure according to an embodiment of the present invention; and

FIG. 14 is a schematic illustration of a nano particle composite polymer material, including a polymer host material, a plurality of nanostructures and an additive according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous details are set forth to provide an understanding of the present invention. It should 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 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.

The present invention generally relates to a system and method of manufacture for an improved polymer element of a stator and rotor assembly. The system and method are useful, for example, with a variety of applications related to a power section of a positive displacement fluid motor or a progressive cavity pump or a fluid pulse generating device; for example, Halliburton's Pulsonix Deep Wave technology.

Referring generally to FIG. 1, a system 25 is illustrated according to an embodiment of the present invention. In this embodiment, a stator and rotor assembly 25 is comprised of a stator 20 comprising an external tubular member 21 having an internal core of a polymer material 22 molded therein to define an elongated annular space 23. The rotor 24 is formed of a rigid material, for example, metal, and is disposed axially within the annular space 23.

In this embodiment, the tubular member 21 may be a metal tube and the uncured polymer may be molded into the tubular member by utilizing a helical-shaped mold (not shown) that is extended through center of the tubular member 21 before the uncured polymer 22 is injected into the annular space 23 between the mold and the inner wall of the tubular member 21. The mold is subsequently removed from the annular space 23 after the polymer 22 is cured. The polymer may be cured by applying heat treatment or pressure or a combination.

Referring generally to FIG. 2, a cross section of a stator and rotor assembly 25′ is illustrated according to an embodiment of the present invention. The rotor 24′ may be machined of metal with an elongated helical configuration. The outer surface of the rotor 24′ is preferably polished and may even be coated with a friction-reducing surface to reduce the torque necessary to overcome friction between the polymer element 22′ of the stator 20′ and the rotor 24′ which are in contact with one another with an interference fit.

In one embodiment of stator and rotor assembly 25′, the annular space 23′ in the stator 20′ is a two-start helical thread which extends in the same direction as that of the thread of the rotor 24′, wherein each thread of the two-start configuration has a pitch length double that of the rotor 24′.

Referring generally to FIG. 3 and in alternative embodiments of the present invention, the rotor 24″ may have a plurality of lobes 26″ of quantity N and the polymer element 22″ of the stator 20″ may have a number N+1 of threads forming the annular space 23″ of the stator 20″.

In alternative embodiments of the present invention, the inner surface of the stator 20″ may be a helical curve-shaped profile with a plurality of lobes 29″ dispersed longitudinally along the inner surface of the stator 20″. In the alternate embodiment, the rotor 24″ may be bonded to an outer layer of compliant polymer 28″ of sufficient uniform thickness to hydraulically engage the helical curve-shaped inner surface of the stator 20″.

Referring again to FIG. 1, as the rotor 24 is rotated relative to the stator 20 within the annular space 23 of the stator 20, the single-start thread of the rotor 24 progressively contacts the two-start threads of the annular space 23 to form a series of pockets which progress from one end of the stator and rotor assembly 25 to the other. While rotating, the central axis of the rotor 24 orbits about the central axis of the stator 20. One end of the rotor 24 is provided with a connective end for receiving a tool (not shown). The rotor 24 rotates the tool and imparts the above-described orbital movement.

In an alternate embodiment of the present invention, the stator and rotor assembly 25 function as a power section of a positive displacement mud motor and the output of the rotor 24 is affixed to a drive shaft (not shown) connected to a downhole well tool; for example, a drill bit (not shown).

Conduits (not shown) may be attached to opposite ends of the stator and rotor assembly 25, which conduits provide inlet and outlet ports for the pumped fluid.

As indicated above, the diameter of the cross section of the annular space 23 of the stator 20 is the same or less than the diameter of the circular shape of the rotor 24, thus providing an interference fit between the inner surface of the stator polymer 22 and the outer surface of the rotor 24. At the points of contact between the stator 20 and the rotor 24, there may be distortion of the polymer material 22 as the stator 20 engages with the rotor 24. The points of engagement trace the elongated path of the rotor 24 as it rotates and contacts the polymer material 22. The annular spaces 23 formed by the points of engagement between the rotor 24 and polymer material 22 move progressively toward an outlet end of the stator and rotor assembly 25 as the rotor 24 rotates relative to the stator 20. The points of engagement define a seal between the annular spaces 23. The more effective the seal between the rotor 24 and polymer material 22, the greater the differential pressure that may be achieved without stalling of the stator and rotor assembly 25; thereby producing a higher output torque.

In an alternate embodiment of the present invention, the stator and the rotor assembly 25 comprise a progressive cavity pump. In this embodiment, the rotor 24 is turned rotatably by a drive source (not shown), for example, a motor, and a fluid is pumped from stage to stage of the pump to an outlet by the progressing annular spaces 23 of the stator and rotor assembly 25. In this embodiment, the more effective the seal between the rotor 24 and the polymer material 22, the greater the discharge pressure of the pump.

The elastomers of the stator and rotor assembly 25 of the present invention are preferably formed from a polymer material that has improved properties for substantially recovering in shape and size after removal of a deforming force; that is, a polymer material that exhibits physical and mechanical properties relative to elastic memory and elastic recovery. Accordingly, elastomers of the stator and rotor assembly 25 of the present invention are preferably formed from a polymer material produced by a curing method that involves compounding or mixing a base polymer with filler additives or agents that reinforce the polymer and improve the physical and chemical properties of the cured polymer 22.

In the various embodiments of the present invention, the polymer material of the stator and rotor assembly 25 may be manufactured from a polymer composite that includes a polymer host reinforced with a plurality of nano-sized filler material. Introduction of nano-sized filler particles to the uncured polymer may improve the physical and chemical properties of the cured polymer by reducing improving impact strength, improving stress relaxation resistance, improving compression set properties, improving durability and modulus, increasing tear strength, reducing creep, increasing resistance to thermal and hysteresis failure and improving resistance to chemical degradation of the polymer.

The filler material is generally a nano-sized material in the range from approximately 0.1 nanometers to approximately 500 nanometers, at the least dimension.

Nano particle reinforced polymers generally require smaller amounts of filler material than traditional fillers to achieve comparable improvements in physical and chemical properties as compared to polymers with significantly larger particles or non-reinforced polymers. The smaller amount of nano material required to reinforce the elastomer has a concomitant effect of lowering the uncured viscosity of the elastomer thus improving the ability to form longer and thinner profiles of polymer elements of stator and rotor assemblies.

Referring generally to FIG. 4, a polymer reinforced with nano-sized particles is illustrated 50. In this embodiment, a polymer composite 50 comprises a polymer host material, formed of polymer chains 52, and reinforced with a plurality of nano-sized particles 54 functionalized with chemical agents that serve as cross-linking agents.

The polymer host material may be elastomers, thermosets or thermoplastics.

The polymer host material may be an elastomer, such as nitrile, a copolymer of acrylonitrile and butadiene (NBR), or carboxylated acrylonitrile butadiene (XNBR), or hydrogenated acrylonitrile butadiene (HNBR), commonly referred to as highly-saturated nitrile (HSN), or carboxylated hydrogenated acrylonitrile butadiene (XHNBR), or hydrogenated carboxylated acrylonitrile butadiene (HXNBR).

In an alternative embodiment of the present invention, the polymer host material may be a flurocarbon (FKM), such as tetrafluoroethylene and propylene (FEPM), or perfluoroelastomer (FFKM).

In an alternative embodiment of the present invention, the polymer host material may also be polychloroprene rubber (CR), natural rubber (NR), polyether eurethane (EU), styrene butadiene rubber (SBR); ethylene propylene (EPR), ethylene propylene diene (EPDM) or similar elastomers.

In an alternative embodiment of the present invention, the polymer host material may be a thermoplastic (TPE), such as polyphenylene sulfide (PPS), polyetherketone-ketone (PEKK), polyetheretherketone (PEEK), polyetherketone (PEK), polytetrafluorethylene (PTFE), or polysulphone (PSU).

Nano structures may include shapes, such as plates, spheres, cylinders, tubes, fibers, three-dimensional structures, linear molecules, molecular rings, branched molecules and crystalline, amorphous, and symmetric shapes.

Nano particles may be from a variety of materials, such as carbon, silica, metals, graphite, diamond, ceramics, metal oxides, other oxides, calcium, calcium carbonate, inorganic clays, minerals, and polymer materials. For example, the nano structures may be formed from silicon material, such as polysilane resins, polycarbosilane resins (PCS), polysilsesquioxane resins (POS) and polyhedral oligomeric silsesquioxane resins (POSS).

Nano clay may be derived, for example, from montmorillonite, bentonite, hectorite, attapulgite, kaolin, mica and illite.

Nano tubes can be formed from a variety of materials, for example, carbon. Carbon nano tubes exhibit desirable combinations of mechanical, thermal and electrical properties for applications defined by the present invention. Nano fibers may be derived, for example, from graphite, carbon, glass, cellulose substrate and polymer materials. Carbon nano tubes are generally in the range from approximately 0.5 nanometers to approximately 100 nanometers, at the least dimension. Carbon nano fibers are generally in the range from approximately 10 nanometers to approximately 500 nanometers, at the least dimension. Nano clays are generally in the range from approximately 0.1 nanometers to approximately 100 nanometers, at the least dimension.

Referring generally to FIG. 5, in an alternate embodiment, the polymer composite 55 comprises a polymer host material, formed of polymer chains 52 and reinforced with nano-sized particles 56 comprised of nano tubes or nano fibers. As illustrated in FIG. 5, nano tubes can be formed as single-wall nano tubes. As illustrated in FIG. 7, nano tubes also can be formed as multi-wall nano tubes. As illustrated in FIG. 8, nano tubes can be formed as arrays of nano tubes.

Nano particles may include metal oxides of zinc, iron, titanium, magnesium, silicon, aluminum, cerium, zirconium and equivalents thereof, as well as mixed metal compounds, such as indium-tin and equivalents thereof.

Referring generally to FIG. 9, in an alternate embodiment, nano structure 160 may be formed from polysilane resins (PS), as depicted in FIG. 10, polycarbosilane resins (PCS), as depicted in FIG. 11, polysilsesquioxane resins (PSS), as depicted in FIG. 12, or polyhedral oligomeric silsesquioxane resins (POSS), as depicted in FIG. 13, as well as monomers, polymers and copolymers thereof. In the formulas presented in FIGS. 10, 11, 12 and 13, R represents a hydrogen or an alkane, alkenyl or alkynl hydrocarbons, cyclic or linear, with 128 carbon atoms, substituted hydrocarbons R—X, aromatics where X represents halogen, phosphorus or nitrogen-containing groups. The incorporation of halogen or other inorganic groups, such as phosphates and amines, directly onto these nano particles may afford additional improvements to the mechanical properties of the material. For example, the incorporation of halogen group may afford additional heat resistance to the material. These nano structures may also include termination points, such as chain ends that contain reactive or nonreactive functionalities, such as silanols, esters, alcohols, amines or R groups.

Referring generally to FIG. 9, a nano composite material 150 forming an elastomer element of a stator and rotor assembly 25 of the present invention is depicted. Nano composite material 150 is comprised of a polymer host material 152 that may include a plurality of polymers 154, 156, 158 and a plurality of nano structures. 160. The polymer host material 152 exhibits microporocity as represented by a plurality of regions of free volume 162. The nano particles 160 are positioned within free volume region 162.

The polymer host material 152 and the nano structures 160 may interact via interfacial interactions, such as co-polymerization, crystallization, van der Waals interactions, covalent bonds, ionic bonds, and cross-linking interactions between nano structure 160 and polymers 154, 156, 158 to improve the physical and chemical characteristics of the polymer thereby resulting in an extended life for the stator and rotor assembly 25 of the present invention.

In an alternative embodiment, the nano particle structures may be functionalized to enhance the effective surface area and improve the availability of potential chemical reactions or catalysis sites for chemical functional groups on the nano structure. Surface functionalization introduces chemical functional groups to a surface, such as the surface of the polymer, thereby providing a surface layer with increased surface area and containing uniform pores with a high effective surface area, thus increasing the number of potential chemical reactions or catalysis sites on the nano particle structure.

While the present invention has been illustrated and described with reference to particular apparatus and methods of use, it is apparent that various changes can be made thereto within the scope of the present invention as defined by the appended claims.