Downhole variable frequency cutting string heating apparatus for hydrate formations

Abstract

The application provides a device for downhole variable-frequency cutting string heating mining of a hydrate formation, relates to the auxiliary technical field of petrochemical oil and gas mining, and aims to solve the problem of low heating efficiency of the heat conduction mode of resistance heat production in the traditional heating method of oil and gas mining. The device for downhole variable-frequency cutting string heating mining of a hydrate formation comprises a main body and an outer shell arranged outside the main body. The main body comprises a power generation section, an oil inlet section and a heating section which are sequentially connected in communication. The power generation section comprises a cylinder shaft, a coil group and a brush group which are connected in circuit. The heating section comprises a core shaft and an integrated circuit which are connected in circuit, and a heating assembly connected with the core shaft and the integrated circuit, so that the heating efficiency of oil and gas medium is improved.

Description

Technical Field

[0001] This invention relates to the field of auxiliary technology for petrochemical oil and gas extraction, and in particular to a device for downhole frequency conversion cutting tubing heating extraction in hydrate formations. Background Technology

[0002] In the petrochemical industry, the economic extraction of natural gas hydrates and heavy oil has always held a pivotal position. Natural gas hydrates are crystalline substances formed from natural gas and water under high pressure and low temperature conditions, primarily distributed in seabed sediments and some terrestrial permafrost zones. With their wide distribution, high energy density, and organic carbon content twice that of coal, oil, and natural gas combined, natural gas hydrates are considered one of the most promising new, efficient, and clean energy sources, possessing enormous extraction potential. Currently, the main technologies for extracting natural gas hydrates include depressurization, chemical inhibition, and thermal activation.

[0003] The depressurization method disrupts the pressure stability of the hydrate layer by reducing the pressure of the underlying free gas layer, thus inducing hydrate decomposition. However, this method results in a low gas production rate and is prone to secondary hydrate formation during extraction, causing blockage near the wellbore and further reducing the gas production rate. The chemical inhibitor method involves injecting chemical reagents such as brine, methanol, and ethanol into the hydrate layer to alter the phase equilibrium conditions for hydrate formation, thereby promoting hydrate decomposition. While simple and convenient, this method's main drawbacks are the high cost and slow action of the injected chemical inhibitors, and the potential for underground environmental pollution.

[0004] The main extraction methods for natural gas hydrates include the heating method, also known as the thermal activation extraction method. This method involves directly heating the natural gas hydrate layer to raise its temperature above its equilibrium temperature, thereby causing the natural gas hydrate to decompose into water and natural gas. However, existing heating methods can only locally heat the natural gas hydrate layer, and the efficiency of thermal energy utilization and sustainable economics still need to be improved. Heavy oil, as a type of crude oil with high viscosity and specific gravity, has high flow resistance, making it difficult to flow from the oil layer into the wellbore or to be lifted from the wellbore to the surface. Therefore, heating is usually used to reduce the viscosity and pour point of heavy oil in order to extract it from the oil layer.

[0005] However, the heat conduction method using resistance heating in traditional heating methods has low heating efficiency. Summary of the Invention

[0006] In view of the aforementioned problem of low heating efficiency in the extraction of natural gas hydrates and heavy oil, the present invention provides a device for downhole variable frequency cutting tubing heating extraction in hydrate formations, which is used to improve the heating efficiency of natural gas hydrates and heavy oil.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A first aspect of the present invention provides an apparatus for downhole variable frequency cutting tubing heating mining of hydrate formations, comprising a main body and an outer shell sleeved outside the main body; the main body comprises a power generation section, an oil inlet section and a heating section connected in sequence; the power generation section comprises a cylindrical shaft, a coil group and a brush group connected by an electrical circuit; the heating section comprises a core shaft and an integrated circuit connected by an electrical circuit, and a heating component connected to both the core shaft and the integrated circuit;

[0009] The brush assembly is configured to transmit the current supplied by the external power source to the coil assembly to generate a magnetic field that causes the cylinder shaft to rotate and change direction. The magnetic field lines are cut by the coil assembly and generate a first current in the coil assembly. The first current is transmitted to the integrated circuit through the oil inlet section to generate an alternating magnetic field. The alternating magnetic field lines are cut by the mandrel to generate an alternating current on the surface of the mandrel, thereby inducing the heating element to generate heat to heat the oil and gas medium from the oil inlet section.

[0010] The present invention has at least the following beneficial effects:

[0011] By designing a three-section device for downhole variable frequency cutting tubing heating and extraction of hydrate formations, consisting of a power generation section, an oil inlet section, and a heating section, the device utilizes the sliding electrical contact between the cylinder shaft and the brush assembly in the power generation section to transmit current to the coil assembly and then to the integrated circuit in the heating section to induce an alternating magnetic field. The alternating current is then generated on the core shaft in the heating section to induce the heating component to generate a large amount of heat, thereby efficiently heating the oil and gas medium entering from the oil inlet section.

[0012] In the above-mentioned device for downhole variable frequency cutting string heating mining of hydrate formations, the heating component may optionally include a coil and a heating element disposed between the outer shell and the mandrel, wherein the coil and the heating element are spaced apart along the axial direction of the heating section, and the coil and the heating element are axially symmetrically distributed on both sides of the mandrel.

[0013] In the above-mentioned device for downhole variable frequency cutting string heating mining of hydrate formations, the heating section may optionally include a first heat insulation component connected around the integrated circuit;

[0014] The first heat insulation component includes a heat insulation ring, a first heat insulation ring, and a second heat insulation ring. The heat insulation ring is connected to one end of the integrated circuit near the oil inlet section. The radial direction of the spindle is a first direction. The first heat insulation ring and the second heat insulation ring are disposed opposite to each other on both sides of the integrated circuit along the first direction.

[0015] In the above-mentioned device for downhole variable frequency cutting string heating mining of hydrate formations, a second heat insulation component may be provided between the coil and the heating element;

[0016] The second heat insulation component includes a heat insulation sheet, a heat insulation plate, and a heat insulation sleeve. The heat insulation sheet is disposed between the heat insulation ring and the coil, and the heat insulation sleeve is fitted over the heating sheet and covers part of the surface of the heating sheet.

[0017] In the above-mentioned device for downhole variable frequency cutting string heating mining of hydrate formations, the heating section may optionally include a second sealing assembly connected to the surface of the heat insulation ring facing away from the integrated circuit.

[0018] The second sealing assembly includes a first sealing ring, a second sealing ring, a second sealing ring, and a third sealing ring. The first sealing ring and the second sealing ring are both sleeved on the end of the mandrel near the oil inlet section, and the first sealing ring is wrapped around the second sealing ring. The second sealing ring and the third sealing ring are both sleeved on the end of the mandrel away from the oil inlet section, and the third sealing ring is wrapped around the second sealing ring.

[0019] In the above-mentioned device for downhole variable frequency cutting string heating mining of hydrate formations, it is optional that the heat insulation ring, the first heat insulation ring, the second heat insulation ring, the heat insulation sheet and the heat insulation sheet are all made of ceramic material.

[0020] In the above-mentioned device for downhole variable frequency cutting string heating mining of hydrate formations, optionally, the second sealing ring is attached to the heat insulation ring, the end of the second sealing ring away from the heat insulation ring is covered by a second end cap, and the second end cap is located between the mandrel and the outer shell.

[0021] In the above-mentioned device for downhole variable frequency cutting tubing heating mining of hydrate formations, optionally, a first sealing assembly is provided on the side surface of the cylinder shaft near the outer shell, the first sealing assembly being a sealing sleeve and a first sealing ring installed opposite to each other on the surface of the cylinder shaft.

[0022] In the above-mentioned device for downhole frequency conversion cutting string heating mining of hydrate formations, optionally, a limiting component is provided between the coil group and the outer shell, and the axial direction of the spindle is a second direction, which is used to limit the coil group along the second direction;

[0023] The limiting components are limiting sleeves and limiting rings respectively fitted onto both ends of the coil group along the second direction.

[0024] In the above-mentioned device for downhole variable frequency cutting tubing heating and mining of hydrate formations, optionally, a first end cap is connected to the end of the cylinder shaft away from the oil inlet section, and the first end cap covers the sealing sleeve and the limiting sleeve. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A structural cross-sectional view of the device for downhole frequency conversion cutting tubing heating mining of hydrate formations provided in an embodiment of the present invention;

[0027] Figure 2 An enlarged cross-sectional view of the power generation section of the device for downhole frequency conversion cutting string heating mining of hydrate formations provided in an embodiment of the present invention;

[0028] Figure 3 An enlarged cross-sectional view of the heating section of the device for downhole variable frequency cutting string heating mining of hydrate formations provided in an embodiment of the present invention;

[0029] Figure 4 The external overall structure front view of the device for downhole frequency conversion cutting string heating mining of hydrate formations provided in an embodiment of the present invention;

[0030] Figure 5 This is a three-dimensional structural schematic diagram of a device for downhole frequency conversion cutting tubing heating mining of hydrate formations, provided in an embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] 100 - Outer shell;

[0033] 200-Power Generation Section;

[0034] 201-First end cap; 202-Sealing sleeve; 203-Limiting sleeve; 204-Coil assembly; 205-Cylinder shaft; 206-Limiting ring; 207-Needle roller bearing; 208-Bearing sleeve; 209-Turbine cylinder; 210-Pin; 211-First sealing ring; 212-Brush assembly; 213-Permanent magnet;

[0035] 300 - Inlet section;

[0036] 400 - Heating section;

[0037] 401-First sealing ring; 402-Heat insulation ring; 403-First heat insulation ring; 404-Second heat insulation ring; 405-Heat insulation sheet; 406-Coil; 407-Heat insulation sheet; 408-Heating sheet; 409-Heat insulation sleeve; 410-Mandrel; 411-Second sealing ring; 412-Second sealing ring; 413-Second end cap; 414-Integrated circuit; 415-Third sealing ring. Detailed Implementation

[0038] As described in the background section, petrochemical industry personnel have been continuously striving to improve the efficiency and economy of natural gas hydrate and heavy oil extraction. Among related technologies, heating methods have always occupied a dominant position as a relatively balanced extraction technology. However, it suffers from the problem of insufficient heating efficiency due to traditional resistance heating. After research, the inventors discovered that the main reason for this problem is that when using resistance ohmic heat as a heat source, controlling the heating frequency is the key to determining the heating efficiency.

[0039] It should be noted that the heating technology mentioned above mainly refers to electromagnetic heating technology, which utilizes ohmic loss and the thermal effect generated by the flow of current to heat natural gas hydrate formations and heavy oil reservoirs. Based on the frequency of the current in the transmission line, electromagnetic heating technology can be divided into two categories: low-frequency heating, mainly resistance heating, with a heating frequency generally less than or equal to 60Hz; and high-frequency heating, which can be further divided into radio frequency heating and microwave heating. In the process of using high-frequency heating technology, high-frequency electromagnetic waves act on the dielectric material, causing polarization and thus rapidly raising the temperature of the heated material.

[0040] To address the aforementioned technical problems, this invention provides a three-section device for downhole variable frequency cutting tubing heating and extraction in hydrate formations, comprising a power generation section, an oil inlet section, and a heating section. In the power generation section, a cylindrical shaft forms a sliding electrical contact with a brush assembly to transmit current to a coil assembly, which then flows to an integrated circuit in the heating section to induce an alternating magnetic field. This field, in turn, generates an alternating current on the spindle in the heating section, triggering a heating element to generate a large amount of heat, thereby efficiently heating the oil and gas medium entering from the oil inlet section.

[0041] In particular, the device for downhole variable frequency cutting string heating extraction in hydrate formations is well adapted to downhole extraction operations in heavy oil and hydrate formations, such as auxiliary downhole extraction equipment like variable frequency cutting string heating extraction operations.

[0042] To make the above-mentioned objectives, features, and advantages of the embodiments of the present invention more apparent and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] This invention provides a device for downhole variable frequency cutting of tubing for heated mining in hydrate formations, combined with... Figure 1 , Figure 4 and Figure 5 It includes a main body and an outer shell 100 fitted outside the main body. The main body includes a power generation section 200, an oil inlet section 300 and a heating section 400 connected in sequence. The outer shell 100 can be integrally formed, or it can be segmented and matched according to the size of the power generation section 200, the oil inlet section 300 and the heating section 400 and then detachably connected. This can improve the flexibility of disassembly and assembly of the outer shell 100 and facilitate installation, maintenance and disassembly.

[0044] The power generation section 200 includes a coil group 204, a cylindrical shaft 205, a permanent magnet 213, and a brush group 212. The coil group 204 includes a rotor coil and a stator coil. The permanent magnet 213 is connected to the stator coil by a wire to form a stator assembly.

[0045] As will be understood by those skilled in the art, the rotor coil is also known as the magnetic field winding; the stator coil is also known as the stator winding, which has three coils and is also called a three-phase winding, and the connection methods include star connection and delta connection.

[0046] When the power generation section 200 is working, an external power source supplies electricity to the rotor coil. The brush group 212 transmits the current supplied by the external power source to the rotor coil, thereby generating an axial magnetic field along the cylindrical shaft 205. The cylindrical shaft 205 serves as both the rotor shaft and the output shaft, used to transmit torque and convert electrical energy into kinetic energy. Under the action of the axial magnetic field, it rotates, and the axial magnetic field rotates synchronously, thereby changing the direction of the magnetic field. The stator coil cuts the magnetic lines of force and generates alternating current. In this way, it can stably and efficiently provide the heating section 400 with current for heat generation. Moreover, the coil group 204, as a coil winding that can generate a magnetic field, can further enhance the magnetic flux density inside the power generation section 200 and is easy to adjust, thereby increasing the power generation capacity.

[0047] Based on the above embodiments, an improvement can be made by having a needle roller bearing 207 slidably connected to the outer side of the cylindrical shaft 205. With this design, compared with ordinary bearings, the radial structure of the needle roller bearing is more compact, reducing the cross-sectional area while still having a high load-bearing capacity.

[0048] Furthermore, a bearing sleeve 208 is provided on the outside of the needle roller bearing 207, which serves to support and protect the needle roller bearing 207.

[0049] As one possible implementation, the end of the cylinder shaft 205 near the oil inlet section 300 is connected to a turbine cylinder 209, which rotates to tension the transmission belt installed inside the generator section 200 to ensure the transmission stability inside the generator section 200.

[0050] Optionally, a plurality of pins 210 are installed on the side wall of the turbine cylinder near the oil inlet section 300 for threaded connection between the generator section 200 and the oil inlet section 300, thereby enhancing the stability of the connection structure between the two.

[0051] In some embodiments, a first sealing component is provided on the side surface of the cylindrical shaft 205 near the housing 100 to improve the airtightness of the cylindrical shaft 205 and ensure the power generation efficiency of the power generation section 200; for example, such as Figure 2 As shown, the first sealing assembly consists of a sealing sleeve 202 and a first sealing ring 211 that are mounted opposite each other on the surface of the cylinder shaft 205.

[0052] Based on the above embodiments, a further improvement can be made by providing a limiting component between the coil assembly 204 and the outer casing 100 to axially limit the coil assembly 204 within the heating section 400, thereby preventing the coil assembly 204 from axially moving due to external forces and causing unstable power generation; for example, combined with Figure 2 The limiting components are limiting sleeves 203 and limiting rings 206 respectively sleeved along the axial direction at both ends of the coil group 204.

[0053] Furthermore, the end of the cylinder shaft 205 away from the oil inlet section 300 is connected to a first end cover 201, and the first end cover 201 covers the sealing sleeve 202 and the limiting sleeve 203. In this way, it simultaneously provides structural support and protection for the sealing sleeve 202, the limiting sleeve 203 and the cylinder shaft 205.

[0054] The oil inlet section 300 is used for the entry of oil and gas media. For example, the surface of the oil inlet section 300 may be provided with multiple openings at circumferential intervals to facilitate the entry of oil and gas media into the device for downhole frequency-controlled cutting tubing heating and extraction of hydrate formations, whereby they are heated by the heating section 400.

[0055] The heating section 400 includes a spindle 410 and an integrated circuit 414 that are electrically connected, as well as a heating element connected to the spindle 410 and the integrated circuit 414.

[0056] Integrated circuit 414 receives the current emitted by power generation section 200 to generate an alternating magnetic field. The alternating magnetic field lines are cut by spindle 410, thereby generating an alternating current, i.e. eddy current, on the surface of spindle 410, which in turn induces the heating component to generate heat to heat the oil and gas medium from oil inlet section 300.

[0057] It should be noted that the above process is similar to the working principle of a microwave heater. A microwave heater applies an external electric field to the material being heated through a microwave generator, and this electric field alternates and rapidly and continuously changes the direction of the applied electric field. This causes the molecules of the heated material to move in accordance with the changing direction of the electric field. Under the combined effect of intermolecular forces, the inertia of molecular motion, and the thermal motion of molecules, the molecular motion is interfered with and hindered. Essentially, this process is similar to the effect of frictional heating. The energy generated by microwaves is converted into molecular kinetic energy, accelerating the random motion of molecules, and thus rapidly raising the temperature of the heated material, achieving microwave heating. The higher the frequency of the applied electric field, the faster the polar molecules of the heated material oscillate, and the greater the amplitude, resulting in increased heat generation.

[0058] Furthermore, the heating component includes a coil 406 and / or a heating element 408 disposed between the outer casing 100 and the spindle 410, and further, combined with Figure 3 The heating element consists of a coil 406 and a heating element 408 spaced apart along the axial direction of the heating section 400, and the coil 406 and the heating element 408 are axially symmetrically distributed on both sides of the spindle 410, which further improves the heat generation efficiency of the heating element.

[0059] In other possible implementations, the heating section 400 may also include a first heat insulation component connected around the integrated circuit 414 to block heat from the outside, especially the large amount of heat generated by the heating component, so as to prevent the integrated circuit 414 from being damaged by heat and failing, causing abnormal function of the heating section.

[0060] Furthermore, the first heat insulation component includes a heat insulation ring 402, a first heat insulation ring 403, and a second heat insulation ring 404. The heat insulation ring 402 is connected to one end of the integrated circuit 414 near the oil inlet section 300. The radial direction of the spindle 410 is the first direction, and the axial direction of the spindle 410 is the second direction. The first heat insulation ring 403 and the second heat insulation ring 404 are arranged opposite to each other on both sides of the integrated circuit 414 along the first direction. This design ensures the heat insulation performance of the integrated circuit 414 while improving the space utilization rate of the first heat insulation component around the integrated circuit 414.

[0061] In some embodiments, such as Figure 3As shown, a second heat insulation component is provided between the coil 406 and the heating element 408. This can suppress heat exchange between the coil 406 and the heating element 408, reduce heat loss of the heating component along the first direction, thereby improving the heat transfer efficiency along the second direction, and thus significantly enhancing the heating efficiency of the device used for downhole frequency conversion cutting string heating mining in hydrate formations.

[0062] Based on the above embodiment, an improvement can be made by using multiple coils 406 and heating elements 408. These multiple coils 406 and heating elements 408 are spaced apart along a first direction within the heating section 400, with the coils 406 and heating elements 408 alternating in distribution. For example, as shown in the figure, a heating element 408 is positioned between every two coils 406. The second heat insulation component includes a heat insulation sheet 405, a heat insulation sheet 407, and a heat insulation sleeve 409. The heat insulation sheet 405 is positioned between the heat insulation ring 402 and the coil 406, further providing heat insulation between the control area of ​​the integrated circuit 414 and the heat-generating area of ​​the heating element. The heat insulation sleeve 409 is fitted over the heating element 408 and covers part of the surface of the heating element 408. Thus, in addition to providing structural and heat insulation protection for the heating element, it also... Figure 1 and Figure 3 By reducing the heat conduction area perpendicular to the paper surface, the heat conduction efficiency of the heating element 408 in a specific one-dimensional direction is enhanced, namely the heat conduction efficiency parallel to the paper surface and along the first direction.

[0063] In more possible embodiments, the materials of the heat insulation ring 402, the first heat insulation ring 403, the second heat insulation ring 404, the heat insulation sheet 405 and the heat insulation sheet 407 are preferably ceramic materials, which not only ensures the heat insulation capability of the heat insulation component from the structural layout, but also further enhances the heat insulation from the material dimension.

[0064] Furthermore, the heating section 400 also includes a second sealing assembly connected to the surface of the heat insulation ring facing away from the integrated circuit 414, for improving the sealing performance of the heating section 400.

[0065] Furthermore, the second sealing assembly includes a first sealing ring 401, a second sealing ring 411, a second sealing ring 412, and a third sealing ring 415. The first sealing ring 401 and the second sealing ring 412 are both sleeved on the end of the spindle 410 near the oil inlet section 300, and the first sealing ring 401 encircles the second sealing ring 412. The second sealing ring 411 and the third sealing ring 415 are both sleeved on the end of the spindle 410 away from the oil inlet section 300, and the third sealing ring 415 encircles the second sealing ring 411. Through the above-mentioned multi-stage sealing structure, the sealing of both ends of the heating section 400 is further strengthened, which provides enhanced protection for the internal components of the heating section 400, including corrosion prevention and electromagnetic interference prevention.

[0066] In one possible implementation, the second sealing ring 411 is attached to the heat insulation ring 402, and the end of the ring away from the heat insulation ring 402 is covered by a second end cap 413. The second end cap 413 is located between the spindle 410 and the outer shell 100 to provide structural support and protection for the end of the heating section 400 away from the oil inlet section 300. In particular, when the heat insulation ring 402 is made of ceramic material, due to its inherent hardness and brittleness, the second end cap 413 plays a limiting and stabilizing role for the heat insulation ring 402 in the second direction, thereby avoiding the problem of material defects caused by the heat insulation ring 402 contacting and colliding with the outer shell 100 due to instability caused by external force. That is, the second end cap 413 plays a structural buffer role between the second sealing ring 411 and the outer shell 100.

[0067] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0069] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0070] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0071] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0072] It should be noted that the embodiments referred to in the specification, such as "one embodiment," "embodiment," "exemplary embodiment," and "some embodiments," may include specific features, structures, or characteristics, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for downhole variable frequency cutting of tubing for heated mining in hydrate formations, characterized in that, The system includes a main body and an outer casing fitted over the main body. The main body includes a power generation section, an oil inlet section, and a heating section connected in sequence. The power generation section includes a cylindrical shaft, a coil group, a permanent magnet, and a brush group connected by an electrical circuit. The heating section includes a core shaft and an integrated circuit connected by an electrical circuit, as well as a heating element connected to both the core shaft and the integrated circuit. The coil group includes a rotor coil and a stator coil, and the permanent magnet is connected to the stator coil via a wire to form a stator assembly. The brush assembly is configured to transmit the current supplied by the external power source to the coil assembly to generate a magnetic field that causes the cylinder shaft to rotate and change direction. The magnetic field lines are cut by the coil assembly and generate a first current in the coil assembly. The first current is transmitted to the integrated circuit through the oil inlet section to generate an alternating magnetic field. The alternating magnetic field lines are cut by the mandrel to generate an alternating current on the surface of the mandrel, thereby inducing the heating element to generate heat to heat the oil and gas medium from the oil inlet section.

2. The device for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 1, characterized in that, The heating component includes a coil and a heating element disposed between the outer casing and the spindle. The coil and the heating element are spaced apart along the axial direction of the heating section, and the coil and the heating element are axially symmetrically distributed on both sides of the spindle.

3. The device for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 2, characterized in that, The heating section also includes a first heat insulation component connected around the integrated circuit; The first heat insulation component includes a heat insulation ring, a first heat insulation ring, and a second heat insulation ring. The heat insulation ring is connected to one end of the integrated circuit near the oil inlet section. The radial direction of the spindle is a first direction. The first heat insulation ring and the second heat insulation ring are disposed opposite to each other on both sides of the integrated circuit along the first direction.

4. The device for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 3, characterized in that, A second heat insulation component is provided between the coil and the heating element; The second heat insulation component includes a heat insulation sheet, a heat insulation plate, and a heat insulation sleeve. The heat insulation sheet is disposed between the heat insulation ring and the coil, and the heat insulation sleeve is fitted over the heating sheet and covers part of the surface of the heating sheet.

5. The device for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 4, characterized in that, The heating section also includes a second sealing assembly connected to the surface of the heat insulation ring facing away from the integrated circuit. The second sealing assembly includes a first sealing ring, a second sealing ring, a second sealing ring, and a third sealing ring. The first sealing ring and the second sealing ring are both sleeved on the end of the mandrel near the oil inlet section, and the first sealing ring is wrapped around the second sealing ring. The second sealing ring and the third sealing ring are both sleeved on the end of the mandrel away from the oil inlet section, and the third sealing ring is wrapped around the second sealing ring.

6. The apparatus for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 5, characterized in that, The heat insulation ring, the first heat insulation ring, the second heat insulation ring, the heat insulation sheet, and the heat insulation sheet are all made of ceramic material.

7. The apparatus for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 6, characterized in that, The second sealing ring is in contact with the heat insulation ring, and a second end cap is fitted on the end of the second sealing ring away from the heat insulation ring, and the second end cap is located between the mandrel and the outer shell.

8. The apparatus for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 1, characterized in that, The cylindrical shaft is provided with a first sealing component on the side surface near the outer casing. The first sealing component consists of a sealing sleeve and a first sealing ring that are mounted opposite each other on the surface of the cylindrical shaft.

9. The apparatus for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 8, characterized in that, A limiting component is provided between the coil assembly and the outer shell, and the axis of the spindle is a second direction, which is used to limit the coil assembly along the second direction; The limiting components are limiting sleeves and limiting rings respectively fitted onto both ends of the coil group along the second direction.

10. The apparatus for downhole frequency conversion cutting tubing heating mining of hydrate formations according to claim 9, characterized in that, The end of the cylinder shaft away from the oil inlet section is connected to a first end cover, and the first end cover covers the sealing sleeve and the limiting sleeve.

Images