Ceramic ptc self-limited temperature heating oil pipe suitable for exploitation of thickened oil horizontal well

Abstract

The utility model relates to heating oil pipe technical field is a kind of ceramic PTC self-limiting heating oil pipe suitable for heavy oil horizontal well exploitation, it includes inner tube, oil pipe, inner tube is fixedly installed with oil pipe outside, oil pipe lower end is fixedly installed with coupling, inner tube outside is coated with inside heat conduction insulating layer by plasma spraying process, the outer wall of inside heat conduction insulating layer is coated with ceramic PTC heating layer using chemical solution spin coating method, ceramic PTC heating layer outside is installed with feed bus, ceramic PTC heating layer upper side and lower side are respectively installed with conducting ring, conducting ring is connected with feed bus, ceramic PTC heating layer outside is coated with outside heat conduction insulating layer by plasma spraying process.The utility model is reasonable and compact in structure, convenient to use, ceramic PTC heating layer uses ceramic PTC material as heating element, realizes self-limiting heating function, can be insulated and can be heat-conducted through heat conduction insulating layer, and the crude oil in and outside oil pipe is heated, to improve heating efficiency, accurate temperature control, reduce energy consumption.

Description

Technical Field

[0001] This utility model relates to the field of heated tubing technology, and is a ceramic PTC self-regulating heated tubing suitable for heavy oil horizontal well production. Background Technology

[0002] Heavy oil extraction is challenging due to its high viscosity and poor fluidity. Traditional methods include steam injection, hot water flooding, and chemical viscosity reduction, but these methods suffer from high energy consumption, low efficiency, and severe environmental pollution. In recent years, electric heating technology has been increasingly applied to heavy oil extraction. It directly heats the crude oil in the tubing and near the wellbore to reduce its viscosity, thereby improving its fluidity.

[0003] Currently, commonly used electric heating technologies mainly include resistance heating and electromagnetic heating. Resistance heating generates heat by passing an electric current through a resistance wire. It requires a fixed heating power to be preset based on parameters such as the initial viscosity of the crude oil, the well depth, and the formation temperature distribution. For example, for a specific heavy oil horizontal well, after detailed calculations, the heating power might be set at 220kW, with the aim of raising the heavy oil temperature to a suitable viscosity-reducing range within a certain production cycle. This heating power remains constant throughout the entire production process. However, it suffers from problems such as uneven heating, high energy consumption, and susceptibility to overheating and damage. Summary of the Invention

[0004] This invention provides a ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production, which overcomes the shortcomings of the prior art and can effectively solve the problems of uneven heating and easy overheating damage of existing in-well crude oil heating devices.

[0005] The technical solution of this utility model is achieved through the following measures: a ceramic PTC self-limiting heating tubing suitable for heavy oil horizontal well production, comprising an inner tube and an oil tube, with the oil tube fixedly installed outside the inner tube, and a coupling fixedly installed at the lower end of the oil tube. The outer side of the inner tube is coated with an inner thermally conductive and insulating layer by plasma spraying. The outer wall of the inner thermally conductive and insulating layer is coated with a ceramic PTC heating layer by chemical solution spin coating. A power supply bus is installed outside the ceramic PTC heating layer. Conductive rings are installed on the upper and lower sides of the ceramic PTC heating layer, and the conductive rings are connected to the power supply bus. The outer side of the ceramic PTC heating layer is coated with an outer thermally conductive and insulating layer by plasma spraying. A cable lead-out connector is installed outside the oil tube, and the cable lead-out connector is connected to the power supply bus.

[0006] The following are further optimizations and / or improvements to the above-mentioned utility model technical solution: Preferably, the inner thermally conductive insulating layer and the outer thermally conductive insulating layer are thermally conductive insulating layers made of aluminum nitride ceramic material.

[0007] Preferably, the inner tube is made of 42CrMoV material.

[0008] Preferably, the upper outer side of the oil pipe is threaded, the thread is a trapezoidal thread and is phosphated.

[0009] Preferably, each conductive ring has a mounting groove on its outer side, and a sealing rubber ring is installed in the mounting groove.

[0010] This utility model has a reasonable and compact structure and is easy to use. The ceramic PTC heating layer uses ceramic PTC material as the heating element to achieve self-limiting temperature heating function. The thermally conductive insulation layer can both insulate and conduct heat, heating both the crude oil inside and outside the oil pipe, thereby improving heating efficiency, precise temperature control and reducing energy consumption. Attached Figure Description

[0011] Appendix Figure 1 This is a schematic diagram of the front cross-sectional structure of an embodiment of the present utility model.

[0012] Appendix Figure 2 For the appendix Figure 1 A top-view sectional structural diagram.

[0013] The codes in the attached diagram are as follows: 1 is the cable lead-out connector, 2 is the oil pipe, 3 is the outer thermally conductive insulation layer, 4 is the ceramic PTC heating layer, 5 is the inner thermally conductive insulation layer, 6 is the inner tube, 7 is the conductive ring, 8 is the sealing rubber ring, 9 is the coupling, 10 is the power supply busbar, and 11 is the thread. Detailed Implementation

[0014] This utility model is not limited to the following embodiments, and the specific implementation method can be determined according to the technical solution of this utility model and the actual situation.

[0015] In this utility model, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as front, back, top, bottom, left, right, etc. The positional relationships are determined based on the layout direction of the attached diagram in the instruction manual.

[0016] The present invention will be further described below with reference to the embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1 , 2As shown, the ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production includes an inner tube 6 and a tubing 2. The tubing 2 is fixedly installed outside the inner tube 6, and a coupling 9 is fixedly installed at the lower end of the tubing 2. The outer side of the inner tube 6 is coated with an inner thermally conductive insulating layer 5 by plasma spraying. The outer wall of the inner thermally conductive insulating layer 5 is coated with a ceramic PTC heating layer 4 by chemical solution spin coating. A power supply bus 10 is installed on the outer side of the ceramic PTC heating layer 4. Conductive rings 7 are installed on the upper and lower sides of the ceramic PTC heating layer 4, and the conductive rings 7 are connected to the power supply bus 10. The outer side of the ceramic PTC heating layer 4 is coated with an outer thermally conductive insulating layer 3 by plasma spraying. A cable lead-out connector 1 is installed on the outer side of the tubing 2, and the cable lead-out connector 1 is connected to the power supply bus 10.

[0017] Before tubing 2 is lowered into the horizontal section of a heavy oil horizontal well, multiple units of this device are connected to form a tubing string. After lowering, the cable lead-out connector 1 is connected to an external power source via a cable. External power is transmitted to the feed bus 10 through the cable lead-out connector 1, and then the feed bus 10 stably delivers power to the conductive ring 7, which includes a positive conductive ring and a negative conductive ring. If the temperature of the crude oil in the formation downhole is low, the resistance of the ceramic PTC heating layer 4 is low, and current flows into the heating layer through the positive conductive ring 7 to generate heat. The heat is transferred to the crude oil in the inner tubing 6 through the inner thermally conductive insulation layer 5, and to the tubing 2 and the surrounding formation crude oil through the outer thermally conductive insulation layer 3. As the crude oil temperature rises, the resistance of the ceramic PTC heating layer 4 increases, the current decreases, and the heating power automatically decreases. When the temperature reaches 200℃, no current flows, achieving self-limiting temperature control and ensuring heating safety and energy saving. Compared with traditional downhole electric heating devices, this invention can automatically adjust the power according to the formation and crude oil temperature in the tubing, reducing energy consumption by 70%-90%. In a practical application at a heavy oil horizontal well, the average monthly power consumption of traditional electrically heated tubing was 1.5 million kWh, while using the heating tubing of this invention reduced the average monthly power consumption to 150,000-450,000 kWh. Tests showed that using the heating tubing of this invention significantly reduced the temperature difference of crude oil at different locations in the horizontal section of the heavy oil horizontal well, and the average viscosity reduction rate increased by 35%-45% compared to traditional electrically heated tubing, significantly improving crude oil fluidity and extraction efficiency. This invention effectively avoids problems such as localized overheating, current leakage, circuit failure, and mechanical damage, greatly reducing the probability of tubing damage and safety accidents.

[0018] Both the inner thermally conductive insulating layer 5 and the outer thermally conductive insulating layer 3 can serve as insulation and heat conduction layers, allowing heat to be transferred to the crude oil in the inner tube 6, as well as the oil pipe 2 and the surrounding formation crude oil, thus solving the problem of not being able to heat the formation crude oil.

[0019] Based on the requirements, N80 grade tubing was selected as the outer protective layer for tubing 2. The tubing underwent visual inspection and non-destructive testing to ensure that its quality met the API standard requirements. N80 tubing has high strength and good toughness, which can effectively resist mechanical impact and wear downhole. It is tightly wrapped around the outer thermally conductive insulation layer to form reliable protection for the internal structure.

[0020] The ceramic PTC heating layer 4 is made of ceramic PTC material, which has excellent electric heating performance and precise self-limiting temperature characteristics. At room temperature, the ceramic PTC material has low resistance and can generate heat through a large current; when the temperature rises to the Curie temperature, the resistance increases exponentially, and the current decreases rapidly, thus achieving automatic temperature control and ensuring that the heating oil pipe is not damaged by overheating. The positive temperature coefficient characteristic of the ceramic PTC material originates from the influence of changes in its internal crystal structure on the movement of charge carriers. At low temperatures, charge carriers move freely, and the resistance is low; as the temperature rises, the crystal structure changes, the movement of charge carriers is hindered, and the resistance increases. This invention uses a chemical solution spin coating method to coat the ceramic PTC heating layer 4 onto the outer wall of the inner thermally conductive insulating layer 5. During the coating process, the concentration of the solution, the spin coating speed, and the drying temperature are strictly controlled to achieve a ceramic PTC heating layer thickness of 1.6 mm, a room temperature resistance of 17 Ω, a Curie temperature of 200 °C, and other parameters set according to requirements.

[0021] The conductive ring 7 includes a positive conductive ring and a negative conductive ring, made of copper-nickel-chromium alloy, which has good conductivity, corrosion resistance, and mechanical strength. The feed bus 10 uses a highly conductive copper busbar with a silver-plated surface to reduce resistance. The feed bus 10 is arranged along the axial direction of the tubing 2 and reliably connected to the positive and negative conductive rings 7. Its function is to efficiently transmit electrical energy to the conductive rings 7, which then power the ceramic PTC heating layer 4. The cable lead-out connector 1 adopts a sealed structure design, with the interior filled with high-temperature and high-pressure resistant insulating sealant to prevent downhole fluid from entering. The exterior of the connector is wrapped with high-strength alloy steel, which has good pressure resistance and corrosion resistance. Its function is to reliably connect the feed bus 10 inside the tubing to the external cable, ensuring stable power transmission and preventing damage to the connector from the harsh downhole environment.

[0022] The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production can be further optimized and / or improved according to actual needs: Example 2: As shown in the attached document Figure 1 , 2As shown, the inner thermally conductive insulating layer 5 and the outer thermally conductive insulating layer 3 are made of aluminum nitride ceramic material. Aluminum nitride has high thermal conductivity and good insulation properties, with a thermal conductivity of 170-230 W / (mK) and high insulation resistance. It can effectively and quickly transfer the heat generated by the ceramic PTC heating layer 4 to the crude oil in the inner tube 6 and the crude oil outside the oil pipe 2, while preventing current leakage into the inner tube 6 and avoiding electrochemical corrosion. It is uniformly coated on the outer wall of the inner tube by a thermal spraying process, with a thickness of generally 0.6 mm-1.2 mm.

[0023] Example 3: As shown in the attached document Figure 1 , 2 As shown, inner tube 6 is a fitting made of 42CrMoV material. 42CrMoV (42CrMoV) has excellent corrosion resistance, resisting the erosion of various corrosive media in formation fluids (such as hydrogen sulfide, carbon dioxide, chloride ions, etc.). It also possesses good high-temperature and high-pressure resistance, ensuring long-term stable operation in complex downhole environments and guaranteeing stable crude oil transportation. The wall thickness of inner tube 6 is designed according to the specific operating conditions of the oil well, generally ranging from 8mm to 12mm. The coupling 9 is made of the same 42CrMoV alloy as inner tube 6.

[0024] Example 4: As shown in the appendix Figure 1 , 2 As shown, the upper outer side of the oil pipe 2 is provided with a thread 11, which is a trapezoidal thread and is phosphated. The thread 11 is used to connect to the upper set of couplings 9. The surface of the thread 11 is phosphated to improve its wear resistance and corrosion resistance.

[0025] Example 5: As shown in the attached document Figure 1 , 2 As shown, each conductive ring 7 has a mounting groove on its outer side, and a sealing rubber ring 8 is installed in the mounting groove to ensure good sealing performance.

[0026] The above technical features constitute various embodiments of this utility model, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production, characterized in that... It includes an inner tube and an oil pipe. An oil pipe is fixedly installed on the outside of the inner tube. A coupling is fixedly installed at the lower end of the oil pipe. The outer side of the inner tube is coated with an inner thermally conductive and insulating layer by plasma spraying. The outer wall of the inner thermally conductive and insulating layer is coated with a ceramic PTC heating layer by chemical solution spin coating. A power supply bus is installed on the outside of the ceramic PTC heating layer. Conductive rings are installed on the upper and lower sides of the ceramic PTC heating layer, and the conductive rings are connected to the power supply bus. The outer side of the ceramic PTC heating layer is coated with an outer thermally conductive and insulating layer by plasma spraying. A cable lead-out connector is installed on the outside of the oil pipe, and the cable lead-out connector is connected to the power supply bus.

2. The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production according to claim 1, characterized in that... The inner and outer thermally conductive insulating layers are made of aluminum nitride ceramic material.

3. The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production according to claim 1 or 2, characterized in that... The inner tube is made of 42CrMoV material.

4. The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production according to claim 1 or 2, characterized in that... The upper outer side of the oil pipe is threaded, the thread is a trapezoidal thread and is phosphated.

5. The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production according to claim 3, characterized in that... The upper outer side of the oil pipe is threaded, the thread is a trapezoidal thread and is phosphated.

6. The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production according to claim 1, 2, or 5, characterized in that... Each conductive ring has a mounting groove on its outer side, and a sealing rubber ring is installed in the mounting groove.

7. The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production according to claim 3, characterized in that... Each conductive ring has a mounting groove on its outer side, and a sealing rubber ring is installed in the mounting groove.

8. The ceramic PTC self-regulating heating tubing suitable for heavy oil horizontal well production according to claim 4, characterized in that... Each conductive ring has a mounting groove on its outer side, and a sealing rubber ring is installed in the mounting groove.

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