JPH0125198B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conduit for an electrode device for electric heating of underground hydrocarbon resources, and more specifically, a conduit coated with electrical insulation for an electrode device used when extracting hydrocarbon underground resources by an electric heating method. It is related to. In the following description, 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 50m thick 100m deep underground, but due to its high viscosity, it cannot be extracted by pumping it up at room temperature, so heated steam is injected into the oil sand layer. The method used was 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 install a conduit such as a steel or stainless steel pipe with an electrode supported at its tip so that the electrode is located in the oil sand layer. Two such oil extraction conduits are installed approximately 30 to 200 meters apart.
A voltage of several hundred to several thousand volts is applied between both electrodes,
A method has been proposed in which oil is extracted by increasing the temperature of the oil sand layer using Joule heat and lowering the viscosity of the oil. In this case, the resistivity of the oil sand layer is several times higher than that of the upper stratum, so the part of the conduit buried in the stratum must be covered with an electrical insulator to prevent current from flowing through the upper stratum. It won't happen. If not covered with an electrical insulator, current will flow through the strata.
This is because current no longer flows between the electrodes buried in the oil sand layer. Accordingly, there is a rapidly increasing need to develop conduits coated with electrical insulators that can withstand use under these special conditions. The characteristics that such electrical insulators must have are: (A) withstand voltage characteristics of several hundred to several thousand volts not only at room temperature but also at temperatures of approximately 300°C, which can reduce the viscosity of oil in the oil sand layer; as well as at least
Must have a volume resistivity of approximately 10 ⁶ Ω-cm. (B) Water contained in the oil sand layer is heated to a temperature of approximately 300°C, which can reduce the viscosity of the oil sand layer, so it can withstand hot water of approximately 300°C. (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. etc. are required. This invention was made in view of the following circumstances, and 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. An inorganic paint made of alkali silicates or metal phosphates is applied to the outer circumferential surface of the conduit, hardened to form a first coating, and then coated with polyether ether by electrostatic powder coating. To provide a conduit for an electrode device for electric heating of hydrocarbon underground resources, which is coated with an electrical insulator having all the characteristics of (A) to (C) above by forming a second coating made of a ketone resin. The purpose is to Examples of the polyetheretherketone resin used in the present invention include aromatic polyetheretherketones represented by the following chemical structural formula and developed by Imperial Chemical Industries Ltd. in the UK. As this polyetheretherketone resin, powder having a particle size of 10 to 100 μm is used. Further, as the metal conduit, a steel pipe or a stainless steel pipe, which has excellent corrosion resistance and good electrical conductivity, is suitable. The inorganic paint of alkali silicate that forms the first film is prepared by adding alumina or silica as a filler to an aqueous solution of sodium silicate, potassium silicate, or lithium silicate, and adding (i) phosphoric acid, (ii) phosphorus as a hardening agent. metal phosphates, such as acid aluminum, zinc phosphate, magnesium phosphate and iron phosphate;
(iii) metals such as zinc and magnesium; (iv) zinc oxide;
Metal oxides such as magnesium oxide and zirconium oxide; (v) metal carbonates such as zinc carbonate, magnesium carbonate, calcium carbonate, and aluminum carbonate;
(vi) Metal sulfates such as zinc sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; or (vii) metal chlorides such as zinc chloride, magnesium chloride, calcium chloride, and aluminum chloride. Inorganic paints using metal phosphates include aqueous solutions of aluminum phosphate, calcium phosphate, magnesium phosphate, iron phosphate, or zinc phosphate, with alumina or silica added as a filler, and aluminum oxide, silicon oxide, or oxide as hardeners. Titanium, iron oxide or tin oxide is used. Next, in order to form a second coating of polyetheretherketone resin on the surface of the metal conduit using the electrostatic powder coating method, the powder is applied to the conduit that has been preheated to 350 to 450°C, and then Heat to ~450°C to melt the powder. Here, it is known that the expansion coefficients of the polyetheretherketone resin coating and the metal conduit are significantly different, and a large internal stress is generated at the fused surface of the metal conduit and the coating, resulting in a decrease in adhesion. Therefore, if a polyether ether ketone resin film is directly formed on the outer circumferential surface of a conduit, the polyether ether ketone resin film will disappear if the pipe is subjected to repeated hydrothermal cycles at 25°C and 300°C in water. It peels off from the pipe surface and cannot be put to practical use. On the other hand, the above-mentioned inorganic paint of alkali silicate or metal phosphate is applied to the outer circumferential surface of the conduit, and after drying the moisture, it is heated at a predetermined temperature to cause a reaction to form an inorganic coating, and then Polyetheretherketone resin coating has a high degree of adhesion and can be heated at 25℃ and 300℃.
It has been confirmed that it can withstand hot water cycles at ℃, and is suitable as an insulating coating for conduits in oil sand layer heating electrode devices. Next, one embodiment of the structure of the conduit insulator of the present invention will be described. FIG. 1 is a partial vertical cross-sectional view of the tip of a conduit coated with electrical insulation. It is covered with an insulator 3 made of a film. Generally, the length of the 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, it is difficult to insert the tip into the oil sand layer. Insert the conduits while joining them one after another. FIG. 2 is a partial vertical cross-sectional view of the aforementioned joint portion of the electrically insulating coated conduit, and as shown in the figure, a conduit 2a coated with an electrically insulating layer 3a and a conduit 2 coated with an electrically insulating layer 3b.
When joining the conduits 2a and 2b, tapered threads 5 are cut at the ends of each of the conduits 2a and 2b, and the couplings 4 are used to join the conduits 2a and 2b. In that case, in order to prevent electrical leakage from the joint, the joint, that is, the coupling 4
A similar electrically insulating layer 3c is further coated over the surface and the end of the conduit. Next, insulating layers 3 and 3 in FIGS. 1 and 2
The coating conditions and properties of a, 3b, or 3c 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 The weight composition ratio of the solid content is 100 parts of sodium silicate,
100 parts alumina, 5 parts aluminum phosphate,
A water-based inorganic paint with a solid content concentration of 20% is applied to the outer circumferential surface of the conduit, and heated at 90°C for 2 hours and 200°C for 5 hours to cure, forming a first inorganic coating with a thickness of 0.05 mm. Ta. Next, the conduit with the inorganic coating formed thereon was preheated to 380°C, and polyetheretherketone resin powder was applied by electrostatic powder coating, and the mixture was heated and melted at 380°C for 10 minutes to form a thick film on the outer circumferential surface of the conduit. A second coating of 0.3 mm of polyetheretherketone was formed. The electrostatic powder coating and heating and melting operations were repeated three more times (four times in total) to obtain the desired insulator coating for the conduit. Adhesive strength (Kg/cm ² ) and withstand voltage (kV/mm) at 25°C of the insulator coating obtained in this way.The insulator was immersed in water and heated to 300°C. After holding for a period of time, cool to 25°C. This process was regarded as one cycle, and after 5 cycles of hot water cycles, the adhesion strength and withstand voltage values measured at 25° C. are shown in Table 1 as Example 1. Examples 2 to 14 An electrical insulator was formed on the outer circumferential surface of a conduit by changing the composition ratio of the solid content of the inorganic paint and its heat curing conditions, and keeping the other conditions the same as in Example 1. The characteristics of Examples 2 to 14 are shown in Table 1.
It was shown as Comparative Examples 1 and 2 Table 2 shows the properties of electrical insulators in which a polyetheretherketone resin coating was directly formed on the outer peripheral surface of untreated and blasted conduits.

【table】

[Table] As is clear from the results shown in Tables 1 and 2, in the electrically insulating coated conduit of the present invention, the insulator has excellent electrical properties, mechanical properties, and hot water resistance. It is particularly effective as a conduit for an electrical heating electrode device used to extract underground hydrocarbon resources by electrical heating.

[Brief explanation of drawings]

FIG. 1 is a partial vertical sectional view of an embodiment of the present invention.
FIG. 2 is a partial vertical sectional view of the joint of FIG. 1. 1... Electrode, 2, 2a and 2b... Conduit,
3, 3a, 3b and 3c... electrical insulating layer, 4...
...Cup ring, 5...Taper screw.

Claims (1)

[Scope of Claims] 1. A device in which current is passed through a metal conduit to an electrode, including a first coating made of an inorganic paint formed on the outer peripheral surface of the metal conduit, and an electrostatic powder coated on the first coating. A conduit for an electrode device for electric heating of hydrocarbon underground resources, characterized in that it is provided with a second coating made of polyetheretherketone resin by body coating. 2. A conduit for an electrode device for electric heating of hydrocarbon underground resources according to claim 1, wherein the inorganic paint is an alkali silicate salt. 3. A conduit for an electrode device for electric heating of hydrocarbon underground resources according to claim 1, wherein the inorganic paint is a metal phosphate.