JPS6245956B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conduit for an electrode device for electrically heating underground hydrocarbon resources, and more specifically, to an electrically insulating coating that supports a heating electrode used when extracting underground hydrocarbon resources by an electric heating method. This relates to conduits that have been 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
This oil exists in a layer approximately 50 meters thick several hundred meters underground, but due to its high viscosity, it cannot be extracted by pumping it up at room temperature. Conventionally, 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 bury a conduit made of steel or stainless steel pipe with an electrode at its lower end so that the electrode is located in the oil sand layer. , two such conduits are installed in parallel at an interval of about 30 to 200 m, and a voltage of several hundred to several thousand volts is applied between the two electrodes to raise the temperature of the oil sand layer by Joule heat, which increases the viscosity of the oil. A method of extracting oil by lowering the amount of oil was proposed. 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. No. If it is not coated with an electrical insulator, current will flow through the strata, and no current will flow 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. Therefore, the characteristics that the electrical insulator coated on the conduit must have are: (A) It can withstand several hundred to several thousand volts not only at room temperature but also at temperatures of about 300 degrees Celsius, which can reduce the viscosity of oil in the oil sand layer. withstand voltage characteristics and at least
( ^B ) The water contained in the oil sands layer is heated to a temperature of about 300°C which can reduce the viscosity of the oil sands layer; (C) Mechanical strength to allow the electrode to be suspended, and sufficient strength to prevent damage from 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. Must have mechanical impact strength. etc. are required. This invention was made in view of the above circumstances, and an object thereof is to provide a conduit for an electrode device for electric heating of hydrocarbon underground resources, which has excellent voltage resistance, heat resistance, mechanical strength, etc. It is. This invention will be described in detail below. The inventors of the present invention have conducted extensive research to develop a conduit coated with an electrical insulator that has all of the characteristics (A) to (C) above. , nickel, aluminum, chrome,
All of the above (A) to (C) can be achieved by forming a film of metal such as silicon or iron, or an alloy thereof, and then forming a film of polyether ether ketone resin by electrostatic powder coating. The inventors discovered that an electrical insulator having these characteristics could be obtained and completed the present invention. In general, thermal spraying methods used to form metal coatings include gas spraying or gas explosion thermal spraying, which uses a combustion flame of oxygen and fuel (acetylene, propane, hydrogen, etc.) as a heat source, or electrical energy. Examples include arc spraying, plasma jet spraying, and high frequency induction spraying using a heat source. By these methods, it is possible to form a film by laminating high-temperature metal particles on the outer peripheral surface of the conduit. Materials for the metal coating used in this invention include nickel (Ni), aluminum (Al), chromium (Cr), silicon (Si), iron (Fe), etc., which are metals different from those of the metal conduit, and Examples include alloys such as nickel-aluminum (Ni-Al), nickel-chromium (Ni-Cr), and silica-aluminum (Si-Al). These metal materials to be subjected to thermal spraying are powders or wires. Polyetheretherketone resin is used as an electrical insulator, and is represented by the following chemical structural formula. are preferred. Powder with a particle size of 10 to 100 μm is used as a material for polyether ether ketone resin. As the metal conduit, a steel pipe or a stainless steel pipe having excellent corrosion resistance and good electrical conductivity is suitable. When forming a film of polyetheretherketone resin on the surface of a metal conduit using electrostatic powder coating, apply polyetheretherketone resin powder to the conduit that has been preheated to 350 to 450°C, and then apply the coating again.
This powder is fused by heating to 350-450°C.
In that case, since the expansion coefficients of the polyether ether ketone resin coating and the metal conduit are greatly different, a large internal stress is generated on the fusion surface of the metal conduit and the polyether ether ketone resin coating, resulting in a decrease in adhesion. In this way, a film of polyetheretherketone resin is directly formed on the surface of a metal conduit.
When repeated hydrothermal cycles at 25°C and 300°C in water, the polyetheretherketone resin coating peels off from the conduit surface, making it unusable for practical use. However, metal conduits with a metal coating of 0.2 mm or less formed by thermal spraying have a high adhesion strength of polyether ether ketone resin, and
It can also withstand 300℃ hydrothermal cycles.
It is suitable as an insulating coating for a conduit in an oil sand layer heating electrode device. Next, one embodiment of the present invention will be described.
In FIG. 1, a metal coating 3 is formed by thermal spraying on the outer peripheral surface of a metal conduit 2 to which an electrode 1 is connected and supported, and an insulating coating 4 is further formed by electrostatic powder coating. Generally, the length of the metal 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, the tip of the pipe is inserted into the oil sand layer. In case these 5~
Insert the 50m pieces while connecting them one after another. FIG. 2 shows the junction of electrically insulating coated conduits: a conduit 2a coated with a metal coating 3a and an electrically insulating coating 4a, and a conduit 2a coated with a metal coating 3b and an electrically insulating coating 4b.
When joining conduit 2b coated with
are cut and joined using a coupling ring 6. In that case, in order to prevent electrical leakage from the joint, the surface of the joint, that is, the surface of the coupling ring 6 and the conduit 2a,
An electrically insulating layer 4c is further coated over the end portion 2b. Next, the method for forming an insulating film made of polyetheretherketone resin and its properties will be explained in more detail by giving examples and comparative examples.
The invention is not limited only to these examples. Example 1 Nickel powder was sprayed onto the outer circumferential surface of a metal conduit using a plasma jet spraying method to a film thickness of 0.1 mm.
A nickel film was formed. Next, the metal conduit on which the metal coating was formed was preheated to 380°C, and polyetheretherketone resin powder was applied by electrostatic powder coating, and the metal conduit was heated and melted at 380°C for 10 minutes to coat the outer periphery of the metal conduit. A polyetheretherketone film with a thickness of 0.3 mm was formed on the surface. The electrostatic powder coating and heating and melting operations were repeated three more times, a total of four times, to obtain the desired electrically insulating coating. Adhesive strength (Kg/cm ² ) and withstand voltage value (kV/mm) at 25°C of the electrically insulating film thus obtained
and its insulating coating was placed in water and heated to 300℃,
After holding in hot water at 300℃ for 100 hours, cool to 25℃. This process is 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 10 An experiment was conducted under the same conditions as in Example 1 except that the metal coating was replaced with one shown in Table 1. An electrical insulation coating was formed on the outer peripheral surface of the conduit, and the characteristics of the obtained electrical insulation coating were evaluated. are shown in Table 1 as Examples 2 to 10. Comparative Examples 1-2 Table 2 shows the characteristics of the electrically insulating coating when the polyetheretherketone resin coating was directly formed on the outer peripheral surface of the conduit.

【table】

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

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view of an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of the junction of the conduit of FIG. 1; 2, 2a and 2b...metal conduit, 3, 3a and 3b...metal coating, 4, 4a and 4c...insulating coating, 5...tapered screw, 6...coupling.

Claims (1)

[Claims] 1. In a conduit of an electrode device for electric heating of hydrocarbon underground resources that is buried underground with an electrode supported at the lower end, a metal conduit and a metal conduit formed on the outer circumferential surface of the metal conduit by a thermal spraying method. and a metal coating made of a metal different from the metal conduit, and an electrically insulating coating made of polyetheretherketone resin formed on the surface of the metal coating by electrostatic powder coating. Hydrogen underground resource conduit for electrical heating electrode equipment. 2. A conduit for an electrode device for electric heating of hydrocarbon underground resources according to claim 1, wherein the metal coating is made of a metal selected from nickel, aluminum, chromium, silicon, and iron. 3. A conduit for an electrode device for electric heating of hydrocarbon underground resources according to claim 1, wherein the metal coating is an alloy selected from nickel-aluminum, nickel-chromium, and silica-aluminum.