JPH0241128B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrically insulated coated conduit used when extracting underground hydrocarbon resources by an electrical heating method. In the following explanation, underground hydrocarbon resources refer to bitumen contained in oil sands or tar sands, and are referred to as oil unless otherwise specified. In recent years, with the rise in the price of oil resources, serious consideration is being given to extracting oil from oil sand layers buried underground in countries such as Canada and Venezuela. This oil sand layer is usually underground
It exists in a layer approximately 50 meters thick 100 meters underground, but due to its high viscosity, it is impossible to extract it by pumping it up at room temperature, so currently heated steam is injected into the oil sand layer. The method used is to raise the temperature of the oil and lower its viscosity before pumping it. However, this method is inefficient and expensive, so a more productive method is to bury a conduit (steel pipe or stainless steel pipe) with an electrode at the tip so that the electrode is located in the oil sand layer. , two such oil extraction conduits are installed at an interval of approximately 30 to 200 m,
A method of extracting oil by applying a voltage of several hundred to several thousand volts between both electrodes, raising the temperature of the oil sand layer by Joule heat, and lowering the viscosity of the oil has been seriously considered. Because the resistivity of the oil sand layer is several times higher than that of the upper stratum, the portion of the conduit buried in the stratum must be covered with an electrical insulator to prevent current from flowing through the upper stratum. If it is not coated with an electrical insulator, current will flow through the geological formations and will not flow between the electrodes buried in the oil sands layer. Accordingly, there is a rapidly increasing need to develop conduits coated with electrical insulators that can withstand use under these special conditions. The following characteristics (A), (B), and (C) are required for this electrical insulator. (A) It must have a withstand voltage characteristic of several hundred to several thousand volts and a volume resistivity of at least 10 ⁶ Ω-cm or more, not only at room temperature but also at temperatures that can reduce the viscosity of oil in the oil sand layer (approximately 300°C). . (B) The temperature at which the water contained in the oil sand layer can reduce the viscosity of the oil sand layer (approximately 300℃)
It must be able to withstand hot water of approximately 300℃. (C) It must have mechanical strength to allow the electrode to be suspended and mechanical impact strength to the extent that it will not be damaged by contact with the hole wall when the electrode suspended at the tip of the conduit is buried in the oil sand layer through the buried hole. The present inventors have conducted extensive research to develop a conduit coated with an electrical insulator that has all of the characteristics (A) to (C) above, and as a result, the inventors have discovered that the conduit is made from epoxy resin and poly-para-vinylphenol resin. A prepreg of a resin composition (2) or a resin composition (2) to which an imidazole compound or a boron trifluoride amine complex is added and glass fiber containing 90% or more of silica is applied to the outer peripheral surface of the conduit. The inventors have discovered that a conduit coated with an electrical insulator having all of the properties (A) to (C) above can be obtained by wrapping the material in layers and heating and curing it, and have completed the present invention. The epoxy resin used in the present invention has two or more epoxy groups in its molecule, and a typical example thereof is a bisphenol type epoxy resin represented by the following structural formula. The value n of this bisphenol type epoxy resin is preferably up to 2. Commercially available products include Epicote 828, Epicote 834 (all manufactured by Yuka Ciel Epoxy Co., Ltd.), and Araldite.
Examples include GY-250 and Araldite GY-280 (both manufactured by Ciba-Geigi). Epoxy resins other than the bisphenol type epoxy resins mentioned above include novolac type epoxy resins. It is preferable that n of this novolac type epoxy resin is up to 2, and commercially available products include Araldite EPN1138 (manufactured by Ciba-Geigi), DEN431,
Examples include DEN438 (manufactured by Dow Chemical Company, USA). Further examples include cresol novolak type epoxy resins. This cresol novolak type epoxy resin
is up to 2, and m is up to 5. Commercially available products include Araldite ECN1235, Araldite
ECN1273, Araldite 1280, Araldite
1299 (all manufactured by Chibagaiki), etc.
Any of them can be suitably used in the present invention. Examples of curing agents that can react with these epoxy resins include Maruzen Resin M (manufactured by Maruzen Oil Co., Ltd.), which is a poly-para-vinylphenol resin. Furthermore, Maruzen Resin MB (manufactured by Maruzen Sekiyu), a brominated poly-para-vinylphenol resin, etc., all of which are suitably used in the present invention. Specific examples of imidazole compounds include 2-methylimidazole, 2-ethylimidazole, 2
-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-undenelimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, cyanoethylated-2-methylimidazole,
Examples include cyanoethylated-2-ethyl-4-methylimidazole, cyanoethylated-2-undecylimidazole, and cyanoethylated-2-phenylimidazole. Specific examples of boron trifluoride amine complexes include boron trifluoride monoethylamine, boron trifluoride dimethylaniline, boron trifluoride benzylamine, and boron trifluoride-2
- Examples include methylimidazole. As the glass fiber, a glass fiber containing 90% or more of silica is used. If the silica content of the glass fiber is less than 90%, the surface of the glass fiber will be dissolved by hot water at 300°C, lowering the volume resistivity of the insulator and lowering its mechanical strength. The prepreg can be made into an insulator by wrapping the prepreg around the outer circumferential surface of the conduit and then heating and curing it. As the metal conduit, for example, a steel pipe or a stainless steel pipe, which has excellent corrosion resistance and good electrical conductivity, is suitable. The length of the conduit is determined depending on the depth of the underground oil sand layer, but usually about 200 to 600 meters is required. Next, embodiments of the electrically insulating coated conduit of the present invention will be described. FIG. 1 is a partial cross-sectional view of the distal end of an electrically insulating coated conduit. As shown in FIG. 1, prepreg is wrapped around the outer circumferential surface of a metal conduit 2 to which an electrode 1 is connected, and then heated and cured to cover it with an electrically insulating layer 3. Generally, the length of conduit 2 is required to be approximately 200 to 600 m, but since the length of each ordinary steel pipe or stainless steel pipe is 5 to 50 m, when inserting the tip into the oil sand layer is inserted while bonding. FIG. 2 is a partial cross-sectional view of a joint of an electrically insulating coated conduit. As shown in FIG. 2, when connecting a conduit 2a coated with an electrically insulating layer 3a and a conduit 2b coated with an electrically insulating layer 3b, taper threads 5 are cut at the ends of each conduit 2a and 2b, and the coupling 4. In that case, in order to prevent electrical leakage from the joint, the joint, that is, the surface of the coupling 4 and the end of the conduit, are further coated with an electrically insulating layer 3c. Next, the method of coating the prepreg electrical insulating layer and its properties will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Example 1 A glass fiber tape having a thickness of 0.20 mm and a width of 30 mm and having a silica content of 90% or more was coated with 100 parts of Epikote 828 (parts by weight, hereinafter the same), 64 parts of Resin M, and boron trifluoride-2- 1 part methylimidazole, 155 parts methyl ethyl ketone and 10 parts methyl alcohol
impregnated with a varnish consisting of parts, then air-dried and
A prepreg tape was produced by heating and drying at 80°C. This prepreg tape was wound 8 times on the outer circumferential surface of the conduit in a half-overlapping manner, and heated to 130°C for 1 hour, 150°C for 1 hour, and 180°C under pressure using heat shrink tape.
It was heated and cured for 2 hours. Tensile strength (Kg/cm ² ) and dielectric breakdown voltage (kV/mm) at 25°C of the obtained electrical insulating layer, and after immersing the insulating layer in hot water at 300°C for 500 hours at 25°C.
The tensile strength and dielectric breakdown voltage values measured in Table 1 are shown in Table 1. Examples 2 to 8 Experiments were conducted in the same manner as in Example 1, except that the composition of the prepreg impregnating varnish and the heat curing conditions were changed to those shown in Table 1, and an electrically insulating layer was formed on the outer peripheral surface of the conduit. Table 1 shows the properties of the electrically insulating layer obtained.

[Table] Next, a comparative example in which conditions are further specified with respect to the above-mentioned example will be described. Comparative Example 1 An experiment was conducted in the same manner as in Example 1, except that an E-glass fiber tape with a silica content of 52% was used instead of a glass fiber tape with a silica content of 90% or more. A layer was formed. Table 2 shows the properties of the electrically insulating layer obtained. Comparative Example 2 An experiment was conducted in the same manner as in Example 1, except that instead of the glass fiber tape with a silica content of 90% or more, an S glass fiber tape with a silica content of 65% was used. A layer was formed. Table 2 shows the properties of the electrically insulating layer obtained. Comparative example 3 Bisphenol type epoxy resin Epicoat 828
Chitsonox, an alicyclic epoxy resin, replaces
An experiment was conducted in the same manner as in Example 1 except that 100 parts of 221 (manufactured by Chitsuso Co., Ltd.) and 100 parts of Resin M were used to form an electrically insulating layer on the outer peripheral surface of the conduit. Table 2 shows the properties of the electrically insulating layer obtained.

[Table] As is clear from the results listed in Tables 1 and 2, the electrically insulating coated conduit of the present invention:
The insulating layer has excellent electrical properties, mechanical properties, and hot water resistance, making it suitable for use as a conduit for extracting hydrocarbon underground resources by electrical heating.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of the distal end of an electrically insulating coated conduit. FIG. 2 is a partial cross-sectional view of a joint of an electrically insulating coated conduit. In the figure, 2, 2a and 2b are conduits, 3, 3a,
3b and 3c are electrically insulating layers. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A fiber prepreg consisting of a resin composition consisting of an epoxy resin and a poly-para-vinylphenol resin and a silica component of 90% or more is attached to the outer peripheral surface of a metal conduit, and then heated and cured. Electrical insulation coated conduit. 2. The electrically insulating coated conduit according to claim 1, wherein the epoxy resin is a bisphenol type epoxy resin. 3. The electrically insulating coated conduit according to claim 1, wherein the epoxy resin is a novolak type epoxy resin. 4. The electrically insulating coated conduit according to claim 1, wherein an imidazole compound or a boron trifluoride amine complex is added to the resin composition.