A downhole microwave heating device using thermoelectric material for self-power supply and its working method

Abstract

The present invention discloses an underground microwave heating device and a working method thereof that uses thermoelectric materials for self-power supply. The power generation tube includes an insulating protection tube and a power generation unit. The P-type and N-type thermoelectric crystals of the power generation unit are arranged in the inner cavity of the insulating protection tube; the power conversion device is connected to the microwave transmitting device; when one power generation tube is used, the slips and the microwave transmitting device are respectively arranged at the two ends of the insulating protection tube, and several power generation units connected in series are connected to the power conversion device; when more than two power generation tubes are used, the insulating protection tubes of each power generation tube are sequentially connected into a row through an elastic structure, the slips are arranged on the insulating protection tube of the power generation tube at the head end, the microwave transmitting device is arranged on the insulating protection tube of the power generation tube at the end, the power generation units of all the power generation tubes are connected in series, and all the power generation units connected in series are connected to the power conversion device. The present invention can realize self-power supply by utilizing the temperature gradient of the bottom layer, without the need to additionally set up ground power generation equipment.

Description

Technical Field

[0001] The invention relates to the field of oil and gas field development, and in particular to a downhole microwave heating device which uses thermoelectric materials for self-power supply and a working method thereof. Background Art

[0002] Thermal oil recovery technology is a method of extraction by injecting heat into the formation or generating heat underground. It is a relatively effective method for extracting heavy oil and coalbed methane. Microwave heating technology is a new and efficient means in the heat injection extraction process. Compared with traditional reservoir heating methods, it has the advantages of low power consumption, strong penetration ability, high heat transfer efficiency and strong reservoir applicability. For heavy oil reservoirs, the content of colloid and asphaltene in heavy oil is high, so its viscosity is very high and its fluidity is poor, which greatly increases the difficulty of heavy oil extraction. The reservoir temperature can be increased by transmitting microwaves downhole, and the viscosity of heavy oil can be reduced in situ to make it have good fluidity. For coalbed methane extraction, coalbed methane reservoirs have the characteristics of strong adsorption, low permeability, low formation pressure and strong plasticity. Microwave radiation can quickly increase the temperature of coal seams, promote coalbed methane desorption, and further generate and extend cracks in the rock mass to improve the permeability of coal seams.

[0003] However, the existing microwave heating technology mainly places the generator at the wellhead, carries the microwave generator into the wellbore through a cable, and transmits the electric energy generated by the generator to the microwave generator through the cable, and the microwave generator works to generate microwaves to heat the reservoir. This requires additional power supply equipment, and the distance from the ground to the bottom of the well is long, the underground conditions are complicated, the electrical signal transmission is unstable, the microwave generator cannot operate normally, and the maintenance process is time-consuming and labor-intensive, which greatly increases the mining cost. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a downhole microwave heating device and a working method thereof that are self-powered by thermoelectric materials. The present invention can achieve self-power supply without the need for additional ground power generation equipment.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A downhole microwave heating device that uses thermoelectric materials for self-power supply, comprising slips, a transformer, a microwave transmitting device and at least one power generation tube, wherein the power generation tube comprises an insulating protective tube and a plurality of power generation units connected in series and arranged in the inner cavity of the insulating protective tube, wherein the power generation units comprise a P-type thermoelectric crystal and an N-type thermoelectric crystal connected in series with each other, and the P-type thermoelectric crystal and the N-type thermoelectric crystal are arranged in the inner cavity of the insulating protective tube along the length direction of the insulating protective tube; the transformer is connected to the microwave transmitting device;

[0007] When the power generation cylinder is one, the slips and microwave emitting device are respectively arranged at the two ends of the insulating protection cylinder, and a plurality of power generation units connected in series are connected to the power transformation device;

[0008] When more than two generator tubes are used, the insulating protection tubes of each generator tube are connected in sequence into a row through an elastic structure, the slip is arranged on the insulating protection tube of the generator tube at the head end, the microwave transmitting device is arranged on the insulating protection tube of the generator tube at the end, the power generation units of all the generator tubes are connected in series, and all the power generation units connected in series are connected to the transformer.

[0009] Preferably, for a power generation tube, the P-type thermoelectric crystal and the N-type thermoelectric crystal in the insulating protection tube are isolated from each other by an insulating medium.

[0010] Preferably, in each power generation unit, the P-type thermoelectric crystal and the N-type thermoelectric crystal are parallel to each other, and in each power generation tube, a plurality of power generation units connected in series are parallel to each other and are arranged in a cluster in the insulating protection tube.

[0011] Preferably, the insulating protection cylinder comprises an inner cylinder and an outer cylinder which are coaxially arranged, and sealed end covers are respectively provided at both ends of the annular cavity between the inner cylinder and the outer cylinder, and the power generation unit is arranged in the annular cavity between the inner cylinder and the outer cylinder.

[0012] Preferably, a plurality of circles of the power generation units are arranged in the annular cavity between the inner cylinder and the outer cylinder, and the plurality of circles of the power generation units are arranged in the annular cavity in a concentric circle manner and are coaxial with the insulating protection cylinder;

[0013] In each circle of power generation units, there are a number of power generation units, which are connected in series to form a circle;

[0014] Each adjacent circle of power generation units is connected in series.

[0015] Preferably, in each circle of power generation units, the cross-sectional shape of the P-type thermoelectric crystals and the N-type thermoelectric crystals of each power generation unit is fan-shaped, and all the P-type thermoelectric crystals and the N-type thermoelectric crystals form a cylinder, and the cross-sectional shape of the cylinder is a circular ring.

[0016] Preferably, a cold-end annular ceramic thermally conductive substrate and a hot-end annular ceramic thermally conductive substrate are respectively provided at both ends of the insulating protection tube, and a first copper sheet and a second copper sheet for connecting a P-type thermoelectric crystal and an N-type thermoelectric crystal in series are respectively provided on the cold-end annular ceramic thermally conductive substrate and the hot-end annular ceramic thermally conductive substrate; thermally conductive silicone grease is evenly applied on both sides of the cold-end annular ceramic thermally conductive substrate and the hot-end annular ceramic thermally conductive substrate, and the thermally conductive silicone grease is used to fill the gaps on the surfaces of the cold-end annular ceramic thermally conductive substrate and the hot-end annular ceramic thermally conductive substrate.

[0017] Preferably, the elastic structure adopts a spring.

[0018] Preferably, the power conversion device includes a voltage stabilizer and an inverter;

[0019] After all the power generation units are connected in series, the positive pole of the whole is connected to one electrode of the voltage stabilizer, the other electrode of the voltage stabilizer is connected to one electrode of the input end of the inverter, the other electrode of the input end of the inverter is connected to the negative pole of the whole after all the power generation units are connected in series, and the microwave transmitting device is connected to the output end of the inverter.

[0020] The working method of the underground microwave heating device using thermoelectric materials for self-power supply as described above in the present invention includes the following process:

[0021] The downhole microwave heating device using thermoelectric materials for self-power supply is lowered into the oil pipe to the target layer and fixed with slips, and the deployment is completed;

[0022] After the underground microwave heating device using thermoelectric materials for self-power supply is put into operation, the power generation unit in the power generation tube generates electricity through the temperature difference at both ends, the transformer stabilizes the electricity generated by the power generation unit and converts it into alternating current, and the microwave transmitting device uses the alternating current converted by the transformer to transmit microwaves and heat the reservoir.

[0023] The invention has the following beneficial effects:

[0024] After the downhole microwave heating device using thermoelectric materials for self-powering is lowered into the oil pipe, the power generation unit in the power generation tube generates electricity through the temperature difference at both ends, the transformer can stabilize the electricity emitted by the power generation unit and convert it into alternating current, and the microwave transmitting device can use the alternating current converted by the transformer to transmit microwaves and heat the reservoir. From the above, it can be seen that the downhole microwave heating device using thermoelectric materials for self-powering can achieve self-powering without the need to set up additional ground power generation equipment, and uses the temperature difference of the formation to generate electricity, converting thermal energy into electrical energy, achieving full utilization of energy, reducing power consumption, and saving energy and protecting the environment. In addition, the microwave heating device can quickly heat the reservoir, effectively reduce the viscosity of heavy oil or increase the permeability of the coal seam, thereby improving the oil and gas recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is an overall structural diagram of the underground microwave heating device of the present invention which utilizes thermoelectric materials for self-power supply.

[0026] Figure 2 It is a top view of the power generating tube of the present invention.

[0027] In the figure, 1-power generation device, 1-1-cold end annular ceramic heat-conducting substrate, 1-2-hot end annular ceramic heat-conducting substrate, 1-3-P-type thermoelectric crystal, 1-4-N-type thermoelectric crystal, 3-power conversion device, 4-microwave transmitting device, 5-first copper sheet, 6-second copper sheet, 7-insulating protection tube, 8-spring, 9-upper card seat, 10-lower card seat, 11-grip, 12-voltage regulator, 13-inverter, 14-microwave transmitter, 15-insulating protection box. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Reference Figure 1 and Figure 2 The present invention uses thermoelectric materials to power the underground microwave heating device for self-powering, which mainly includes 4 power generation devices 1; slips; power conversion devices 3; microwave transmitting devices 4. When introducing the scheme of the present invention, the following introduction content is described by setting two power generation cylinders as an example, and the specific introduction is as follows:

[0030] In the power generation device 1 (i.e., the power generation tube): the insulating protection tube 7 includes an inner tube and an outer tube arranged coaxially, and sealed end covers are respectively provided at both ends of the annular cavity between the inner tube and the outer tube. In the scheme of the present invention, the cold end annular ceramic heat conductive substrate 1-1 and the hot end annular ceramic heat conductive substrate 1-2 can be directly used as the end covers of the insulating protection tube 7, and two circles of power generation units are arranged in the annular cavity of the insulating protection tube (7). In the present invention, the dimensions of the cold end annular ceramic heat conductive substrate 1-1 are as follows: the inner diameter is 10mm-15mm, the outer diameter is 20mm-25mm, and the thickness is 0.5mm-0.8mm; the dimensions of the hot end annular ceramic heat conductive substrate 1-2 are as follows: the inner diameter is 10mm-15mm, the outer diameter is 20mm-25mm, and the thickness is 0.5mm-0.8mm; the cross section of the P-type thermoelectric crystal 1-3 ( Figure 1 The orientation shown is longitudinal in the up and down directions) and is fan-shaped with the following dimensions: outer diameter 10mm-18mm, inner diameter 5mm-15mm, height 100m, and center angle 11.25°-22.5°; the cross-sectional shape of the N-type thermoelectric crystal 1-4 is fan-shaped with the following dimensions: outer diameter 10mm-18mm, inner diameter 5-15mm, height 100m, and center angle 11.25°-22.5°; the shape of the first copper sheet and the second copper sheet is rectangular with the following dimensions: length 3mm-5mm, width 1.5mm-2mm, and thickness 0.4mm-0.6mm; the inner and outer tubes of the insulating protection tube 7 are made of 23 type fluororubber; the spring wire diameter of the spring 8 is 8mm-10mm, the middle diameter is 12mm-15mm, and the free height is 3cm-5cm. The transformer 3 and the microwave transmitting device 4 are installed at the lower end of the insulating protective tube 7 of the lower generator tube, and the slips are installed on the upper side wall of the insulating protective tube 7 of the upper generator tube.

[0031] To meet different needs, different materials can be used for P-type thermoelectric crystals 1-3 and N-type thermoelectric crystals 1-4. CoSb3 skutterudite is used for heavy oil reservoirs. Among the medium-temperature thermoelectric materials, CoSb3 skutterudite has good high-temperature stability and electrical transport performance, and is more suitable for deep-well heavy oil reservoirs. Bi-Te based alloys are used for coalbed methane reservoirs. The optimal mining temperature range of coalbed methane is 100℃-300℃, and the Bi-Te based alloy has the best thermoelectric performance under this temperature condition.

[0032] The slip adopts a conventional structure, which includes: an upper clamping seat 9, a lower clamping seat 10 and clamping teeth 11.

[0033] The substation 3 includes a voltage stabilizer 12 and an inverter 13. The voltage stabilizer 12 is of Im7818, Im7820 or Im7822 type. The inverter 13 is of 18v-22v to 220v-300v inverter. Both the voltage stabilizer 12 and the inverter 13 are installed in an insulating protection box 15, and the insulating protection box 15 is made of 23-type fluororubber.

[0034] The structure of the microwave transmitting device 4 includes an insulating protection box 15 and a microwave transmitter 14 installed in the insulating protection box 15. The length of the microwave transmitter 14 is 28cm-32cm, the width is 26cm-30cm, and the height is 16cm-20cm. For heavy oil reservoirs, the microwave transmitting frequency of the microwave transmitter 14 is 1000MHz-3000MHz, the power is 0.5kw-2kw, and the voltage is 220v-230v; for coalbed methane reservoirs, the microwave transmitting frequency of the microwave transmitter 14 is 2000MHz-4000MHz, the power is 1kw-3kw, and the voltage is 240v-300v.

[0035] The cold end annular ceramic heat conductive substrate 1-1 and the hot end annular ceramic heat conductive substrate 1-2 are the cold end electrode and the hot end electrode respectively, and can conduct the cold end temperature and the hot end temperature at the upper and lower ends of the insulating protection tube 7. Both sides of the cold end annular ceramic heat conductive substrate 1-1 and the hot end annular ceramic heat conductive substrate 1-2 can be evenly coated with thermal conductive silicone grease to fill the gaps on the substrate surface and improve the thermal conductivity.

[0036] The two ends of the P-type thermoelectric crystal 1-3 and the N-type thermoelectric crystal 1-4 are respectively welded between the cold-end annular ceramic heat-conducting substrate 1-1 and the hot-end annular ceramic heat-conducting substrate 1-2, see Figure 2In each circle of power generation units, P-type thermoelectric crystals 1-3 and N-type thermoelectric crystals 1-4 are alternately arranged in a ring structure, and each P-type thermoelectric crystal 1-3 and N-type thermoelectric crystal 1-4 is plated with a layer of insulating material on the side, and the insulating material can be rubber or resin. The adjacent P-type thermoelectric crystals 1-3 and N-type thermoelectric crystals 1-4 in the same power generation unit are connected by a first copper sheet 5 welded on the cold end annular ceramic thermal conductive substrate 1-1 and a second copper sheet 6 welded on the hot end annular ceramic thermal conductive substrate 1-2 to form a series circuit. A pair of P-type thermoelectric crystals 1-3 and N-type thermoelectric crystals 1-4 is the smallest power generation unit, the P-type thermoelectric crystal is the positive pole of the power supply, and the N-type thermoelectric crystal is the negative pole of the power supply. There are 24 pairs of power generation units welded between the ceramic thermal conductive substrates.

[0037] The inner tube of the insulating protection tube 7 is welded to the inner edge of the cold end annular ceramic heat conductive substrate 1-1 and the hot end annular ceramic heat conductive substrate 1-2, and the outer tube is welded to the outer edge of the cold end annular ceramic heat conductive substrate 1-1 and the hot end annular ceramic heat conductive substrate 1-2. The cold end annular ceramic heat conductive substrate 1-1 and the hot end annular ceramic heat conductive substrate 1-2 seal the two ends of the annular cavity between the inner tube and the outer tube to protect the power generation unit. The P-type thermoelectric crystal and the N-type thermoelectric crystal at the start and end are respectively welded with a copper core insulated cable, which passes through the insulating protective layer and is used to connect the next device.

[0038] The above is a section of the power generation device. Multiple sections of the power generation device are connected by a spring 8 welded between the hot end annular ceramic heat conductive substrate of the previous section and the cold end annular ceramic heat conductive substrate of the next section. The spring material is copper or carbon steel. This connection method can control the length of the entire power generation device, meet different power generation voltage requirements, and can adapt to wells with a certain inclination.

[0039] The upper clamping seat 9 and the lower clamping seat 10 can be clamped on the outer wall of the power generation device, and the clamping teeth 11 can be engaged with the inner wall of the oil pipe. The clamping teeth 11 are fixed to the upper end of the power generation device, and the entire device can be suspended in the oil pipe.

[0040] In the transformer: one end of the voltage stabilizer 12 is connected to the positive pole of the generator, and the other end is connected to the input end of the inverter 13. The other input end of the inverter 13 is connected to the negative pole of the generator, and the connection is realized by a copper-core insulated cable. The voltage stabilizer 12 can stabilize the voltage provided by the generator at a DC low voltage, and the inverter 13 can invert the DC low voltage into an AC high voltage suitable for the microwave transmitter 14. The insulating protection box is sleeved on the outside of the voltage stabilizer 12 and the inverter 13 to play a protective role.

[0041] In the microwave transmitting device: the microwave transmitter 14 is connected to the output end of the inverter 13 through a copper core insulated cable, receives the output end voltage, and can transmit microwaves to heat the reservoir. The microwave transmitter is covered with a protective layer to play a protective role.

[0042] The operation steps of heating the reservoir using the downhole microwave heating device using thermoelectric materials for self-power supply of the present invention include:

[0043] 1. Before lowering the microwave heating device into the well, determine the number of sections of the required temperature difference power generation device according to the geothermal gradient. The calculation formula is:

[0044] 24×α×33.8×dT×n=U

[0045] Where: α is the Seebeck coefficient of a power generation unit, 4.5~5.5×10 -4 V / K; dT ​​is the geothermal gradient, 3.2~4.4℃ / 100m; U is the power generation voltage, 18v~22v for heavy oil reservoirs and 20v-25v for coalbed methane reservoirs; n is the number of nodes of the temperature difference power generation device, which is an integer.

[0046] 2. Connect the generators in series, and assemble two adjacent generators by spring welding.

[0047] 3. Figure 1 Taking the position shown as an example, the transformer and microwave transmitting device are sequentially connected to the lower part of the lowest section of the power generation device. After the assembly is completed, the entire downhole microwave heating device is lowered into the oil pipe. After the downhole microwave heating device reaches the predetermined position, the slips are set and the device is fixed.

[0048] 4. After the underground microwave heating device is stabilized, the two ends of each section of the power generation device are heated to produce a temperature difference, and automatic power generation begins. After the voltage is stabilized and inverted by the transformer, the microwave transmitting device is powered. The microwave transmitter transmits microwaves to the formation to heat the reservoir, increase the temperature of the heavy oil and reduce its viscosity, and generate micro cracks in the coalbed methane reservoir to increase the permeability.

[0049] The principle of the present invention is as follows:

[0050] Thermoelectric power generation technology is mainly based on the Seebeck effect, that is, after two different semiconductors form a closed loop, if there is a temperature difference between the two ends of the contact, an electromotive force is generated between the two contacts, and a current flows through the loop. Oil and gas wells are usually thousands of meters deep underground, and the geothermal gradient averages 3.2~4.4℃ / 100m, so the formation temperature at different depths underground is also different. The present invention utilizes the temperature difference underground, which is an important condition for thermoelectric power generation. The original components that adapt to the special conditions underground are assembled and designed into a thermoelectric power generation device to power the microwave transmitter. The temperature difference between the hot and cold ends of a single-section thermoelectric power generation device can reach up to 4.4℃, and the power supply voltage is 2V. At least 9 single-section thermoelectric power generation devices are needed to power the microwave transmitter.

[0051] The main method of heavy oil recovery by microwave heating is to change the fixed structure between heavy oil molecules through microwave oscillation, thereby enhancing molecular vibration, changing its chemical composition, and causing high-loss components to decompose by overheating. In addition, microwave heating increases the temperature of the oil layer. The two work synergistically to reduce the viscosity of the heavy oil.

[0052] Microwave heating of coalbed methane is due to the fact that microwave radiation can quickly increase the temperature of the coal seam, promote coalbed methane desorption, and increase gas activity. At the same time, the temperature difference thermal stress caused by uneven heating can further generate and extend cracks and pores in the rock mass, thereby increasing the permeability of the coal seam.

[0053] From the above, it can be seen that the present invention can self-power the microwaves to heat the reservoir underground, thereby reducing energy consumption and improving oil and gas recovery.

[0054] Example 1

[0055] In a heavy oil block of a certain oil field, the geothermal gradient is 3.8℃ / 100m, the well depth is 2180m, and the dimensions of the downhole microwave heating device using thermoelectric materials for self-power supply are selected according to the diameter of the downhole oil pipe: the cold end annular ceramic heat conductive substrate, inner diameter 10mm, outer diameter 20mm, thickness 0.6mm; the hot end annular ceramic heat conductive substrate, inner diameter 10mm, outer diameter 20mm, thickness 0.6mm; P-type thermoelectric crystal, outer diameter 11mm, 17mm, inner diameter 7mm, 13mm, height 10mm 0m, center angle 11.25°, 22.5°; N-type thermoelectric crystal, outer diameter 11mm, 17mm, inner diameter 7mm, 13mm, height 100m, center angle 11.25°, 22.5°; P-type and N-type thermoelectric crystal materials are CoSb3 cobaltite; copper sheet, length 4mm, width 1.5mm, thickness 0.4mm; spring, spring wire diameter 8mm, middle diameter 12mm, free height 5cm; microwave transmitter, length 28cm, width 26cm, height 20cm. The voltage regulator model is Im7818 voltage regulator, and the inverter model is 18v to 220v inverter.

[0056] The specific steps of heating the reservoir using the self-powered downhole microwave heating device using the thermoelectric material of this embodiment are as follows:

[0057] (1) The Seebeck coefficient of the power generation unit under this reservoir condition is 5.0×10 -4 V / K, the generating voltage is 18v, and according to the formula, the number of generating units required is 12.

[0058] (2) Fix the slips on the upper end of the first section of the power generation device. Each section of the power generation device is connected by spring welding. The transformer and microwave transmitting device are connected in sequence below the temperature difference power generation device.

[0059] (3) The assembled device is lowered into the oil pipe to the target layer, and the device is locked with a slip. The device is deployed.

[0060] (4) After the device has been stable for 30s-60s, it can start to work normally and emit microwaves to heat the reservoir.

[0061] (5) The device needs to be cleaned and maintained every 3-4 months. If there is no serious damage, it is only necessary to clean the scale on the surface of the device. If serious corrosion occurs, the insulation protection tube needs to be replaced and the internal circuit needs to be checked for damage.

[0062] The microwave heating frequency is 2450MHz, the heating power is 0.8kw, and the voltage is 220v. After the microwave action, the formation temperature rises by 100℃, the crude oil viscosity decreases by 34.36%, and the recovery rate increases by 27.7%.

[0063] Example 2

[0064] In a coalbed methane block in North China, the geothermal gradient is 4.2℃ / 100m and the well depth is 1900m. According to the diameter of the downhole oil pipe, the downhole microwave heating device using thermoelectric materials for self-power supply has the following dimensions: cold end annular ceramic thermal conductive substrate, inner diameter 12mm, outer diameter 22mm, thickness 0.5mm; hot end annular ceramic thermal conductive substrate, inner diameter 12mm, outer diameter 22mm, thickness 0.5mm; P-type thermoelectric crystal, outer diameter 13mm, 19mm, inner diameter 9mm, 15mm, height 10mm. 0m, center angle 11.25°, 22.5°; N-type thermoelectric crystal, outer diameter 13mm, 19mm, inner diameter 9mm, 15mm, height 100m, center angle 11.25°, 22.5°; P-type and N-type thermoelectric crystal materials are Bi-Te based alloy; copper sheet, length 5mm, width 2mm, thickness 0.5mm; spring, spring wire diameter 10mm, middle diameter 14mm, free height 3cm; microwave transmitter, length 30cm, width 28cm, height 18cm. The voltage regulator model is Im7820 voltage regulator, and the inverter model is 20v to 300v inverter.

[0065] The specific steps of heating the reservoir using the self-powered downhole microwave heating device using the thermoelectric material of this embodiment are as follows:

[0066] (1) The Seebeck coefficient of the power generation unit under this reservoir condition is 5.5×10 -4 V / K, the generating voltage is 20v, and according to the formula, the number of generating units required is 11.

[0067] (2) Fix the slips on the upper end of the first section of the power generation device. Each section of the power generation device is connected by spring welding. The transformer and microwave transmitting device are connected in sequence below the temperature difference power generation device.

[0068] (3) The assembled device is lowered into the oil pipe to the target layer, and the device is locked with a slip. The device is deployed.

[0069] (4) After the device has been stable for 30s-60s, it can start to work normally and emit microwaves to heat the reservoir.

[0070] (5) The device needs to be cleaned and maintained every 3-4 months. If there is no serious damage, it is only necessary to clean the scale on the surface of the device. If serious corrosion occurs, the insulation protection tube needs to be replaced and the internal circuit needs to be checked for damage.

[0071] The microwave heating frequency is 4000MHz, the heating power is 2kw, and the voltage is 300v. After the microwave action, the effective affected area reaches 100m, the coal seam permeability increases by 140%-180%, and the annual cumulative gas production can reach 2.9 times that of conventional mining.

Claims

1. A downhole microwave heating device using thermoelectric materials for self-power supply, It is characterized in that The invention comprises a slip, a transformer (3), a microwave transmitting device (4) and at least one power generating tube, wherein the power generating tube comprises an insulating protective tube (7) and a plurality of power generating units connected in series and arranged in the inner cavity of the insulating protective tube (7), wherein the power generating units comprise P-type thermoelectric crystals (1-3) and N-type thermoelectric crystals (1-4) connected in series with each other, and the P-type thermoelectric crystals (1-3) and N-type thermoelectric crystals (1-4) are arranged in the inner cavity of the insulating protective tube (7) along the length direction of the insulating protective tube (7); the transformer (3) is connected to the microwave transmitting device (4); When one power generating cylinder is used, the slips and the microwave transmitting device (4) are respectively arranged at the two ends of the insulating protective cylinder (7), and a plurality of power generating units connected in series are connected to the power transformation device (3); When more than two generator cylinders are used, the insulating protective cylinders (7) of the generator cylinders are sequentially connected into a row through an elastic structure, the slip is arranged on the insulating protective cylinder (7) of the generator cylinder at the head end, the microwave transmitting device (4) is arranged on the insulating protective cylinder (7) of the generator cylinder at the tail end, the power generation units of all the generator cylinders are connected in series, and all the power generation units connected in series are connected to the power conversion device (3); For a power generation tube, a P-type thermoelectric crystal (1-3) and an N-type thermoelectric crystal (1-4) in an insulating protection tube (7) are isolated by an insulating medium; A cold-end annular ceramic heat-conducting substrate (1-1) and a hot-end annular ceramic heat-conducting substrate (1-2) are respectively provided at both ends of the insulating protection tube (7); a first copper sheet (5) and a second copper sheet (6) for connecting a P-type thermoelectric crystal (1-3) and an N-type thermoelectric crystal (1-4) in series are respectively provided on the cold-end annular ceramic heat-conducting substrate (1-1) and the hot-end annular ceramic heat-conducting substrate (1-2); thermal grease is evenly applied on both sides of the cold-end annular ceramic heat-conducting substrate (1-1) and the hot-end annular ceramic heat-conducting substrate (1-2); the thermal grease is used to fill the gaps on the surfaces of the cold-end annular ceramic heat-conducting substrate (1-1) and the hot-end annular ceramic heat-conducting substrate (1-2).

2. According to claim 1, a downhole microwave heating device using thermoelectric materials for self-power supply, It is characterized in that In each power generation unit, the P-type thermoelectric crystals (1-3) and the N-type thermoelectric crystals (1-4) are parallel to each other, and in each power generation tube, a plurality of power generation units connected in series are parallel to each other and arranged in a cluster in an insulating protection tube (7).

3. According to claim 1, a downhole microwave heating device using thermoelectric materials for self-power supply, It is characterized in that The insulating protection cylinder (7) comprises an inner cylinder and an outer cylinder which are coaxially arranged, and sealed end covers are respectively provided at both ends of the annular cavity between the inner cylinder and the outer cylinder, and the power generation unit is arranged in the annular cavity between the inner cylinder and the outer cylinder.

4. According to claim 3, a downhole microwave heating device using thermoelectric materials for self-power supply, It is characterized in that A plurality of circles of the power generation units are arranged in the annular cavity between the inner cylinder and the outer cylinder, and the plurality of circles of the power generation units are arranged in the annular cavity in a concentric circle manner and are coaxial with the insulating protection cylinder (7); In each circle of power generation units, there are a number of power generation units, which are connected in series to form a circle; Each adjacent circle of power generation units is connected in series.

5. The downhole microwave heating device using thermoelectric materials for self-power supply according to claim 4, It is characterized in that In each circle of power generation units, the cross-sectional shape of the P-type thermoelectric crystals (1-3) and the N-type thermoelectric crystals (1-4) of each power generation unit is a fan ring, and all the P-type thermoelectric crystals (1-3) and the N-type thermoelectric crystals (1-4) form a cylinder, and the cross-sectional shape of the cylinder is a circular ring.

6. The downhole microwave heating device using thermoelectric materials for self-power supply according to claim 1, It is characterized in that The elastic structure adopts a spring (8).

7. The downhole microwave heating device using thermoelectric materials for self-power supply according to claim 1, It is characterized in that The power conversion device (3) comprises a voltage stabilizer (12) and an inverter (13); The positive electrode of all the power generation units connected in series is connected to an electrode of the voltage stabilizer (12), the other electrode of the voltage stabilizer (12) is connected to an electrode at the input end of the inverter (13), the other electrode at the input end of the inverter (13) is connected to the negative electrode of the whole after all the power generation units are connected in series, and the microwave transmitting device (4) is connected to the output end of the inverter (13).

8. A method for operating a downhole microwave heating device using thermoelectric materials for self-power supply according to any one of claims 1 to 7, It is characterized in that The process includes the following: The downhole microwave heating device using thermoelectric materials for self-power supply is lowered into the oil pipe to the target layer and fixed with slips, and the deployment is completed; After the underground microwave heating device using thermoelectric materials for self-power supply is deployed, the power generation unit in the power generation cylinder generates electricity through the temperature difference at both ends, the transformer (3) stabilizes the voltage of the electricity generated by the power generation unit and converts it into alternating current, and the microwave transmitting device (4) uses the alternating current converted by the transformer (3) to transmit microwaves and heat the reservoir.

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