WO2016153480A1

WO2016153480A1 - Nano-material structure for electric power transmission

Info

Publication number: WO2016153480A1
Application number: PCT/US2015/022098
Authority: WO
Inventors: Jinglei XIANG; Jason Holzmueller; William Goertzen; Gregory Howard MANKE
Original assignee: Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Technology B.V.; Schlumberger Technology Corporation
Priority date: 2015-03-24
Filing date: 2015-03-24
Publication date: 2016-09-29

Abstract

A technique facilitates transmission of electric power in a variety of environments, including severe environments. A conductive structure, e.g. power cable, is formed with a conductor element constructed with a superconductive graphitic nano-material. The superconductive graphitic nano-material may comprise carbon nanotubes or other suitable materials. The conductor element also is electrically insulated with respect to the surrounding environment. For example, the conductor element may be insulated with another nano-material, such as an insulative nanotube material or nanosheet material.

Description

PATENT APPLICATION

NANO-MATERIAL STRUCTURE FOR ELECTRIC POWER TRANSMISSION

DOCKET NO.: IS14.9485-WO-PCT

INVENTORS: Jinglei Xiang

Jason Holzmueller

Will Goertzen

Greg H. Manke

BACKGROUND

[0001] In many hydrocarbon well applications, power cables are employed to deliver electric power to various devices located in a wellbore. For example, power cables may be used to deliver electric power to downhole motors, such as motors employed in electric submersible pumping systems. However, wellbores often are drilled into severe environments having high pressures, high temperatures, and aggressive chemicals. These severe environments can cause detrimental effects with respect to the power cables. For example, the harsh environmental conditions can cause deterioration and sometimes malfunction of the components and materials used to construct the power cables.

SUMMARY

[0002] In general, a methodology and system are provided to facilitate transmission of electric power in a variety of environments, including severe environments. A conductive structure, e.g. power cable, is formed with a conductor element constructed with a superconductive graphitic nano-material, such as carbon nanotubes or other suitable materials. The conductor element also is insulated with respect to the surrounding environment. For example, the conductor element may be insulated with another nano-material, such as an insulating nanotube material or nanosheet material.

[0003] However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0005] Figure 1 is a schematic illustration of a well system comprising an example of an electric power conducting structure, e.g. power cable, coupled with an electrically powered device, according to an embodiment of the disclosure;

[0006] Figure 2 is a schematic illustration of an example of a conductive nano- material which may be used in the electric power conducting structure, according to an embodiment of the disclosure;

[0007] Figure 3 is a schematic illustration of an example of an insulating nano- material which may be used to insulate the conductive nano-material, according to an embodiment of the disclosure; [0008] Figure 4 is a schematic representation of an example of a method for forming an electric power conducting structure using co-axial solid state spinning in which insulating nanotubes are combined with conductive nanotubes to form a core- sheath structure, according to an embodiment of the disclosure; and

[0009] Figure 5 is a schematic representation of an example of another method for forming an electric power conducting structure using co-axial solution spinning and coagulation of an insulating nanosheet with conductive nanotubes to form a core-sheath structure, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

[0010] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0011] The present disclosure generally relates to a methodology and system provided to facilitate transmission of electric power in a variety of environments, including severe environments. A conductive structure has a conductor element formed with a superconductive graphitic nano-material, such as carbon nanotubes or other suitable materials. The conductor element also is insulated with respect to the surrounding environment to form the conductive structure. For example, the conductor element may be insulated with another nano-material, such as an insulating nanotube material or nanosheet material. In a variety of applications, the conductive structure may be formed as a power cable for delivering electric power to a specific powered device or devices. In well applications, for example, such a power cable may be used for transmission of electrical power in severe environments, such as various downhole environments. [0012] According to an embodiment, the conductive structure may be formed as a severe service dielectric system comprising superconductive graphitic nano-material, e.g carbon nanotubes/graphene, as the conducting element and boron nitride as an adhering insulation layer. The nano-material based dielectric system may be produced in a macroscopic continuous scale through, for example, co-axial solution spinning or solid state spinning to form a core-sheath structure. This type of conductor/insulator system can be used to increase the reliability of power transmission due to the desirable lattice alignment at the interface region forming highly effective bonding between the conductor and the dielectric/insulator. This type of conductor/insulator system further exhibits excellent physical properties including high thermal conductivity, good dielectric properties, and excellent chemical resistance with respect to both the conductive element and insulative element.

[0013] The dielectric system, e.g. power cable, is useful in a variety of applications, including severe service applications. Such severe service applications may involve use of the power cable or other conductive structure in high pressure

environments, high temperature environments, and/or aggressive chemical environments. The dielectric system provides highly reliable power transmission in such conditions and thus can be useful in a variety of downhole applications, such as electric submersible pumping system applications.

[0014] Referring generally to Figure 1, an embodiment of a well system 20 is illustrated as comprising a downhole, electrically powered system 22, e.g an electric submersible pumping system. Electric power is provided to the electric submersible pumping system 22 or other powered system via a conductive structure 24 which in this application is illustrated as a power cable 25. In this example, the power cable 25 provides electric power to a powered component 26, such as a submersible motor which forms part of the electric submersible pumping system 22. The powered component 26, e.g. submersible motor, is delivered downhole into a wellbore 28 by a well string 30. In many applications, the submersible motor 26 or other powered component is delivered into a severe environmental region 32, such that the power cable 25 and powered component 26 may be subjected to high temperatures, high pressures, and/or aggressive chemicals. Depending on the application, however, the conductive structure 24/power cable 25 and the powered component 26 may have a variety of configurations and may be used in a variety of systems and applications.

[0015] The conductive structure 24 may comprise an electrical conductor element

34 (see, for example, Figure 2) and an insulation material 36 (see, for example, Figure 3). Electrical conductor element 34 may be formed of a superconductive graphitic nano- material. In some applications, the superconductive graphitic nano-material may be in the form of nanotubes 38, such as carbon nanotubes or graphene. For example, neat ultra-long carbon nanotubes may be synthesized and spun into yarns or fibers to form the electrical conductor element 34. Similarly, the insulation material 36 also may comprise a nano-material which may be in the form of nanotubes 40 and/or a nanosheet(s) 42.

[0016] Referring again to Figure 2, an example of a material which may be used to form electrical conductor element 34 is illustrated. In this example, electrical conductor element 34 is formed of individual carbon nanotubes 38 which may have different chirality. Chirality determines the electronic band structure and therefore the electrical conductivity of the material, e.g. semi-conductive versus metallic. In at least some power transmission applications, metallic carbon nanotubes may be useful to provide higher electrical conductivity compared to, for example, a semi-conductive counterpart. A number of different techniques may be used to form carbon nanotube- based fibers and to assemble those fibers.

[0017] According to an embodiment, the carbon nanotube-based fibers may be formed by solution spinning in which the carbon nanotubes 38 are dispersed in a surfactant or solubilized in acid and then coagulated into a fiber. In another embodiment, the carbon nanotube-based fibers may be formed by solid state spinning in which fibers are drawn from a vertically grown array of nanotubes or directly collected from aerogel formed in a reaction furnace. High-quality yarns with good mechanical, electrical, and thermal properties may be constructed by synthesizing carbon nanotubes 38 according to such techniques to provide long length, substantially defect free, and type specific carbon nanotubes. Various postprocessing techniques may be used to reduce or eliminate property degrading artifacts that may result from the spinning process.

[0018] Referring again to Figure 3, an example of material which may be used to form insulation material 36 is illustrated. In some applications, the insulation material 36 may be in the form of a structural analog to the carbon nanotubes 38. For example, the insulation material 36 may comprise nanotubes 40 and/or nanosheets 42. In an example, the insulation material 36 comprises nanotubes 40 and/or nanosheets 42 formed from boron nitride. With this type of insulation material 36, the boron and nitrogen atoms may be arranged in a honeycomb lattice structure to create the nanotubes 40 and/or nanosheets 42. Compared with metallic or semiconducting carbon nanotubes, boron nitride is an electrical insulator with a band gap of, for example, ca. 5 eV, independent of tube geometry. In addition, boron nitride nanotubes, e.g. hexagonal boron nitride nanotubes, possess a high chemical stability, excellent mechanical properties, and high thermal conductivity. Boron nitride nanotubes or nanosheets may be synthesized by chemical vapor deposition in a process of the type which also may be useful in forming carbon nanotubes.

[0019] As discussed briefly above, the dielectric system/conductive structure 24 may comprise electrical conductor element 34 in the form of carbon nanotubes 38 and insulation material 36 in the form of boron nitride nanotubes 40 or nanosheets 42. This dielectric system 24 may be manufactured by desired techniques to produce an end product in the form of a composite conductive structure 24 with carbon nanotubes 38 as the internal current carrying conductor element 34 surrounded by an outer dielectric layer of nanotubes 40 or nanosheets 42 to create a core-shell nanostructure.

[0020] An example of a technique for producing the conductive structure 24 comprises co-axial solid state spinning, as illustrated in the embodiment of Figure 4. According to this technique, ultra-long, substantially defect-free, type specific carbon nanotubes 38 may be grown on substrates through chemical vapor deposition. The carbon nanotubes 38 may then be combined into a yarn. To increase the strength of the final carbon nanotube yarn, the interconnectivity of the nanotubes 38 is promoted. For example, the chemical vapor deposition process leads to the tops and bottoms of the nanotubes 38 being more amorphous than the rest of the tubes due to the deposition process initially being less equilibrated.

[0021] The amorphous region on each nanotube 38 leads to an improvement in interconnectivity by forming more entanglement at the end of the tube with other nanotubes 38. In some applications, infiltration by polymer may be employed as an effective method to improve bonding among discrete carbon nanotubes 38 without compromising the electrical properties. The electrical properties are not compromised due to the fact that the infiltrated polymer does not break the connectivity of the nanotubes 38. The mechanical robustness of the produced fiber/yarn also may be increased by twisting the nanotube fibers in a spinning motion.

[0022] Co-axial spinning of the boron nitride nanotubes 40/nanosheets 42 on top of the carbon nanotubes 38 may be performed similarly to the technique of spinning carbon nanotubes, as illustrated in Figure 4. This technique enables formation of the insulation material 36 in a boron nitride sheath, e.g. shell surrounding the conductive carbon nanotubes 38. In this example, carbon nanotubes 38 are grown on a substrate or substrates 44 and joined to form the ultra-long, substantially defect free, type specific carbon nanotubes spun into a yarn 46 which forms a core 48 of the overall conductive structure 24, e.g power cable 25. In the specific embodiment illustrated, an outer insulation sheath 50 is formed of insulation material 36 to construct the core-sheath style conductive structure 24. By way of example, the outer insulation sheath 50 may be formed through the synthesis of vertically aligned boron nitride nanotubes 40 and/or nanosheets 42 as a thermal interface material.

[0023] Referring again to Figure 4, catalytic chemical vapor deposition similar to the synthesis of carbon nanotubes 38 can be used to grow the boron nitride nanotube forest on a substrate or substrates 52. The as-synthesized boron nitride forest may be joined in ultra-long boron nitride nanotubes 40 which are co-axially spun with the vertically aligned carbon nanotube forest into a core-sheath structure 54 with carbon nanotubes 38 being the conductor (core 48) and boron nitride being the dielectric layer (insulation sheath 50). Figure 4 provides a schematic representation of the solid state spinning process forming the core-sheath structure 54 which can be used as the insulated conductor structure 24 in a variety of well and non-well applications. In this example, the electrical conductor element 34 described above is in the form of core 48 and the insulation material 36 comprises sheath 50.

[0024] Another example of a technique for producing the conductive structure 24 comprises co-axial solution spinning, as illustrated in the embodiment of Figure 5.

According to this embodiment, carbon nanotubes 38 are dispersed in an appropriate material 56, such as a surfactant or a super acid. With respect to the example of dispersion in a super acid, during spinning carbon nanotubes tend to form a liquid crystal structure with well aligned nanotubes 38. The acid also effectively protonates the carbon nanotubes which contributes to a high electrical conductivity. Post processing treatment in a solution spun fiber also may directly impact the final mechanical, electrical and thermal properties of the fiber depending on the degree of coalescence among individual carbon nanotubes.

[0025] As discussed above, boron nitride can be synthesized in both nanotubes 40 and nanosheet form 42. In solution spinning, the nanosheets 42 of boron nitride may have a two-dimensional platelet structure which, in some applications, can be better than a one-dimensional tubular geometry to form a layer of dielectric cover on the surface of the carbon nanotube conductor element. Boron nitride nanosheet 42 is dispersible both in aqueous and non-aqueous solvent and can be "coated" directly onto the carbon nanotube yarn/fiber 46 simultaneously with the solution spinning and coagulation of carbon nanotubes 38. [0026] Figure 5 provides a schematic representation showing the formation of a core-sheath nano-insulation system. In this example, a carbon nanotube dispersion and a boron nitride nanosheet dispersion are combined by a spinning device 58, e.g. a yarn spinning device. The spun, core-sheath structure is dispensed into a coagulation bath 60 and coagulated into a fiber, e.g. yarn, which may be wrapped onto a spool 62. In some applications, the coagulation bath may be mounted on a rotating stage 64. The resulting fiber/yarn is thus formed into the core-sheath structure 54 having conductive core 48 and insulation sheath 50. In this example, the core-sheath structure 54 again serves as the conductive structure 24 for carrying electrical current via the conductive core 48 while being insulated by the surrounding insulation material forming sheath 50. In a variety of embodiments, the conductive structure 24 may be used as a power cable, e.g. power cable 25, for delivering power to downhole tools or other types of devices.

[0027] In a variety of applications, use of a boron nitride insulation material and a carbon nanotube conductor element enables construction of a perfect or near perfect lattice match between two nano-materials. The match is due to their identical honeycomb lattice structure. The enhanced interaction between boron nitride and carbon nanotubes through Van der Waals forces further promotes bonding between the two materials forming an excellent interface between the conductor element 34 (e.g. carbon nanotubes 38) and the dielectric/insulation layer 36 (e.g. boron nitride nanotubes 40 or nanosheets 42). The nano-materials comprising both the conductor and insulator portions of the power cable provide a better bonded insulation with excellent corrosion resistance and high temperature resistance as well as excellent partial discharge resistance. These characteristics of the conductive structure 24 enhance the reliability of the power transmission in harsh downhole and other harsh environments.

[0028] Depending on the application, the conductive structure 24 may be constructed in a variety of configurations and sizes. In downhole applications, the conductive structure 24 may be in the form of power cable 25 routed along a tubing string. For example, such a power cable 25 may be used to deliver electrical power to a submersible motor of an electric submersible pumping system employed in a harsh environment. For example, electric submersible pumping systems may be employed in intervention constrained wells in subsea environments or in steam assisted gravity drainage wells.

[0029] Additionally, the conductive structure 24 may comprise a variety of materials combined according to selected techniques. For example, carbon nanotubes or other types of nanotubes may be used to form the conductor element. Similarly, insulation materials other than boron nitride may be used to form the nano-material, e.g. nanotubes or nanosheets, applied as insulation to the conductor element. Both the conductive nano-materials and the insulation nano-materials may be twisted together to form fibers, e.g. yards. However, the materials may be combined in other types of patterns and according to other techniques to form a desired conductor-insulator structure.

[0030] In many applications, e.g. power cable applications, the core-sheath structure 54 may be useful. However, other types of structures, e.g. sandwich structures, may be employed to provide the desired conductive and insulative elements. In some applications, the conductive structure 24 may have a plurality of independent conductors insulated by appropriate insulative nano-material. In motor applications, for example, the conductive structure 24 may be formed as a power cable with three independent conductors for carrying three-phase power with each of the independent conductors insulated by the insulative nano-material.

[0031] Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

CLAIMS What is claimed is:

1. A system for use in a well, comprising: an electrically powered component;

a power cable coupled to the electrically powered component to supply the electrically powered component with electric power, the power cable comprising:

an electrical conductor element formed of a superconductive graphitic nano-material; and

an insulation material surrounding the electrical conductor element, the insulation material being formed of boron nitride.

2. The system as recited in claim 1, wherein the superconductive graphitic nano- material is formed of nanotubes.

3. The system as recited in claim 1, wherein the superconductive graphitic nano- material is formed of carbon nanotubes.

4. The system as recited in claim 1, wherein the superconductive graphitic nano- material is formed of graphene.

5. The system as recited in claim 1, wherein the insulation material is formed of nanotubes.

6. The system as recited in claim 1, wherein the insulation material is formed of a nanosheet.

7. The system as recited in claim 3, wherein the carbon nanotubes are coagulated into a fiber.

8. The system as recited in claim 1, wherein the electrically powered component comprises a motor, wherein the motor is positioned in an electric submersible pumping system.

9. The system as recited in claim 3, wherein ends of the nanotubes are entangled to improve interconnectivity.

10. A method, comprising : forming a conductor with a superconductive graphitic nano-material; and insulating the conductor with a nano-material comprising boron nitride to create a power cable.

11. The method as recited in claim 10, further comprising coupling the power cable to a downhole tool and routing the power cable along at least a portion of a wellbore.

12. The method as recited in claim 10, wherein forming comprises forming the

conductor with the superconductive graphitic nano-material in the form of nanotubes.

13. The method as recited in claim 12, further comprising infiltrating the nanotubes with a polymer.

14. The method as recited in claim 10, wherein forming comprises forming the

conductor with the superconductive graphitic nano-material in the form of carbon nanotubes.

15. The method as recited in claim 10, wherein forming comprises forming the

conductor with the superconductive graphitic nano-material in the form of graphene.

16. The method as recited in claim 14, wherein insulating comprises insulating the conductor with the nano-material in the form of nanotubes.

17. The method as recited in claim 14, wherein insulating comprises insulating the conductor with the nano-material in the form of at least one nanosheet.

18. A method, comprising : forming a conductor element with a superconductive graphitic nano- material;

insulating the conductor; and

conducting electricity via the conductor element in a downhole environment.

19. The method as recited in claim 18, wherein insulating comprises insulating the conductor element with insulation formed of a boron nitride nano-material.

20. The method as recited in claim 19, wherein forming comprises forming the conductor element with carbon nanotubes.