JPS6240515B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to electrically insulating coated conduits used when extracting underground hydrocarbon resources by electrical heating. In the present specification, underground hydrocarbon resources refer to bitumen contained in oil sands or tar sands, and are hereinafter 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 normally exists several hundred meters underground as a layer approximately 50 meters thick, but due to the high viscosity of this oil, it is impossible to extract it by pumping it up at room temperature. The method used is to inject heated steam into the oil sand layer to raise the temperature of the oil, lower its viscosity, and then pump 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 approximately 30 to 200 meters apart, 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 is being 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 characteristics that this electrical insulator must have are (A) voltage resistance of several hundred to several thousand volts, not only at room temperature but also at temperatures that can reduce the viscosity of oil in the oil sand layer (approximately 300°C); at least
( ^B ) A temperature at which the water contained in the oil sand can reduce the viscosity of the oil sand layer (approximately 300°C).
(C) Mechanical strength that allows the electrode to be suspended; It is required to have sufficient mechanical impact strength to prevent damage from contact. Conventionally, attempts have been made to use polyethylene resin, nylon, epoxy resin, etc. for the above purpose;
Polyethylene resin is sensitive to heat and melts at temperatures below 100°C, while nylon is sensitive to hot water and undergoes hydrolysis at around 100°C. Furthermore, epoxy resins also undergo hydrolysis at around 150°C, resulting in decreased electrical insulation properties, making them impractical. The present inventors have conducted intensive research to develop a conduit coated with an electrical insulator that has all of the characteristics (A) to (C) above, and have found that Powdered polyetheretherketone resin with a particle size of 10 to 100 μm is applied to the outer circumferential surface of the conduit using an electrostatic coating method and melted at 380 to 450°C to form a resin coating on the conduit surface. , above (A)
The present inventors have discovered that it has all the characteristics of ~(C), and have completed the present invention. For example, the polyetheretherketone resin used in the present invention is represented by the following chemical structural formula,
Aromatic polyetheretherketones developed by Imperial Chemical Industries Ltd. in the UK include: Polyetheretherketone resin is in powder form and has the advantage that it can be applied and coated by electrostatic coating. The particle size of this resin is 10~100μ
m, preferably from 20 to 70 μm.
If the particle size is smaller than 10 μm, the powder will aggregate and it will not be possible to adhere the powder uniformly. In addition, if the particle size is larger than 100 μm, when the powder is applied and then heated and melted, it will not form a flat coating and air bubbles will be trapped inside the insulator, resulting in an insulator with excellent hot water resistance and electrical properties. cannot be obtained. As the metal conduit, for example, a steel pipe or a stainless steel pipe having excellent corrosion resistance and good electrical conductivity is suitable. The conduit is preheated to 380-450°C. When the conduit is not preheated and the preheating temperature is 380
If the temperature is lower than 0.degree. C., the strength of the fusion between the polyetheretherketone coating and the conduit is small, and the insulating coating will peel off from the conduit after being left in hot water. If the preheating temperature is higher than 450°C, thermal deterioration of the polyetheretherketone resin occurs, and the mechanical properties, hot water resistance, and electrical properties of the insulation coating deteriorate. Polyether ether ketone resin powder applied by conventional electrostatic powder coating method has a particle size of 380 to 450
It is melted by heating at a temperature of 380-430°C, preferably 380-430°C. If the melting temperature is lower than 380°C, the melt flow of the polyetheretherketone resin is insufficient and the coating is not uniform, causing air bubbles to be drawn inside the insulator, resulting in an insulator with excellent hot water resistance and electrical properties. cannot be obtained. If the melting temperature is higher than 450° C., thermal cracking of the polyetheretherketone resin occurs, and the mechanical properties, hot water resistance and electrical properties of the insulating coating deteriorate. Next, embodiments of the electrically insulated conduit of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view of the distal end of an electrically insulating coated conduit. As shown in FIG. 1, an insulator 3 made of polyetheretherketone resin is coated on the outer peripheral surface of a metal conduit 2 to which an electrode 1 is connected by electrostatic powder coating. Generally, the length of the conduit 2 is required to be about 200 to about 600 m, but since the length of one ordinary steel pipe or stainless steel pipe is 5 to 50 m, when inserting the tip into the oil sand layer It is operated while being joined. FIG. 2 is a partial cross-sectional view of a joint of an electrically insulating coated conduit. As shown in FIG. 2, when joining a conduit 2a coated with a polyetheretherketone resin insulator 3a and a conduit 2b coated with a polyetheretherketone resin insulator 3b, each conduit 2a and A taper screw 5 is cut at the end of 2b, and a coupling ring 4 is used to join the parts. 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 insulator 3c of polyether ether ketone resin. Next, the method of coating the polyetheretherketone electrical insulator 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 Powder of an aromatic polyetheretherketone resin manufactured by British Imperial Chemical Industries Ltd. having the above structural formula and having a particle size of 20 to 70 μm was electrostatically applied to a metal conduit preheated to 400°C. The polyether ether ketone coating was applied to the outer surface of the conduit by heating and melting at 400° C. for 10 minutes to form a polyether ether ketone film with a thickness of 0.5 mm. The electrostatic coating and heating and melting operations were repeated three more times (four times in total) to obtain a desired conduit insulator. Adhesive strength of the obtained insulator at 25℃ (Kg/
cm ² ), withstand voltage value (KV/mm) and its insulator 300
Table 1 shows the adhesion strength and withstand voltage values measured at 25°C after being immersed in hot water at 25°C for 500 hours. Examples 2 to 13 Experiments were conducted in the same manner as in Example 1, except that the preheating temperature of the metal conduit and the heating and melting conditions of the polyether ether ketone resin were changed to those shown in Table 1.
An electrical insulator was formed on the outer peripheral surface of the conduit, and the properties of the obtained electrical insulator are shown in Table 1. Comparative Examples 1 to 4 Experiments were conducted in the same manner as in Example 1, except that the preheating temperature of the metal conduit was changed to that shown in Table 1, and an electrical insulator was formed on the outer peripheral surface of the conduit. The properties of the obtained electrical insulator are shown in Table 1. Comparative Examples 5 to 7 Experiments were conducted in the same manner as in Example 1 except that polyetheretherketone resin powder having the particle size shown in Table 2 was used to form an electrical insulator on the outer peripheral surface of the conduit. The properties of the obtained electrical insulator are shown in Table 2.

【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 suitable as a conduit used for extracting hydrocarbon underground resources by electric heating method.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of the distal end of an electrically insulating coated conduit according to the present invention, and FIG. 2 is a partial sectional view of the joint of the conduit of FIG. In the figure, 2, 2a and 2b...conduit, 3, 3a and 3c
...Electrical insulation layer.

Claims (1)

[Claims] 1 Powdered polyether ether ketone resin with a particle size of 10 to 100 μm is adhered to the outer circumferential surface of a metal conduit that has been preheated to 380 to 450 °C using an electrostatic coating method.
A conduit for an electrode device for electric heating of hydrocarbon-based underground resources, fused at 380-450℃.