This invention relates, in general, to thermally conductive polymer composites. The present invention relates, in particular, to downhole cables with polymer composites.
Within an electric submersible pump assembly, a cable extends downhole, terminating in a motor lead to provide power to an electric motor. When electrical power is transmitted through conductors, such as those found in a downhole electric submersible pump cable, heat is generated. Conductors are typically surrounded by insulation. Current electrical insulation polymers have poor thermal conductivity, causing heat to build up. Thermal conductivity values for standard insulation elastomers may range from 0.00238 W/cm K to 0.002428 W/cm K. In some cases, this forces a user to select a larger conductor size, which is costly. In some applications, due to space restraints, increasing conductor size is not practical.
A power cable for an electric submersible pump assembly is constructed with enhanced thermally conductive insulation. The insulation is formed by mixing a polymer with a filler material to create a thermally conductive composite material. Examples of polymers used may include EPDM rubber, nitrile rubber, HNBR rubber, Aflas rubber, FKM rubber, polypropylene (PP), polyethylene (PE), cross-linked PE or PP, thermoplastic elastomers, fluoropolymers, thermoplastics, and thermoset elastomers. Examples of fill materials used may include ceramic additives such as silicon oxide, aluminum oxide, zirconium oxide, silicon nitride, silicon carbide, aluminum nitride, boron carbide, boron nitride, and yitrium oxide, metal powders, and carbon in various forms. The thermally conductive material can be used as insulation around the conductors and also as jacket material for the cables. The thermally conductive composite polymers dissipate heat across the cable more efficiently and quickly than with a standard insulating material. The composite materials may have thermal conductivity values that range from 20 to 100 times that of standard insulation material.
Referring to
Insulation 28 and jacket material 32 can be constructed from various polymer compounds, including: EPDM rubber (Ethylene Propylene diene monomer), nitrile rubber, HNBR rubber, aflas rubber, FKM rubber, polypropylene, polyethylene, cross-linked PE or PP, thermoplastic elastomers, fluoropolymers, thermoplastics or thermoset elastomers. In this embodiment, filler materials 30 are included within the insulation 28 and jacket material 32. Alternately, the filler materials 30 could be located only in jacket material 32. The filler materials 30 may be used to improve thermal conductivity values of the insulation 28 and jacket material 32. In one embodiment, the filler materials 30 are uniformly distributed throughout the insulation 28 and jacket material 32. Examples of filler materials 30 include: ceramic additives such as silicon oxide, aluminum oxide, zirconium oxide, silicon nitride, silicon carbide, aluminum nitride, boron carbide, boron nitride, and yitrium oxide, metal powders, and carbon in various forms. Filler materials 30 are of higher thermal conductivity than the thermoplastic electrical insulation 28 or jacket material 32. The filler materials 30 are not absorbed into the thermo-plastic, rather they remain as discrete particles. Filler materials are typically electrically non-conductive. However, if the application does not require the conductors to be electrically insulated, electrically conductive filler materials could be employed. When reinforced with the various materials, the polymer compounds demonstrate improved thermal conductivity.
The loading for the insulation 28 and jacket material 32 may contain filler material levels ranging from 10 to 80%, and may be used with polymer concentrations of 20 to 90% to obtain a desired thermal conductivity. The enhanced composite polymer compounds may produce thermal conductivity values that range from 20 to 100 times the thermal conductivity values for standard insulation materials.
While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention. For example, although the cable is shown with a round, circular geometry, it could have a flat, rectangular geometry. Additionally, polymer composites could be employed in other similar applications, such as in a heater cable.
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Number | Date | Country | |
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20100096161 A1 | Apr 2010 | US |