Underground steam generator and thermal recovery system

Abstract

The invention discloses an underground steam generator and a thermal recovery system, and belongs to the technical field of thickened oil recovery, and the underground steam generator comprises a metal heating element which is provided with a fluid channel, a liquid inlet and a steam outlet, and the liquid inlet and the steam outlet are communicated with the two ends of the fluid channel and used for heating fluid in the fluid channel; the induction coil is arranged in the connecting line direction of the two ends of the fluid channel, winds and sleeves the circumferential direction of the metal heating element, and the induction coil is used for introducing alternating current; and the insulating layer is sleeved on the induction coil. The thermal recovery system comprises an underground part and a ground part, wherein the underground part comprises the underground steam generator, a liquid conveying pipeline, a connecting wire and a testing pipeline. The transmission process of steam from the ground to the underground can be omitted, heat loss caused by the transmission process is avoided, the heat energy utilization rate is effectively increased, and high efficiency, energy conservation, low carbon and emission reduction are achieved.

Description

Technical Field

[0001] This application belongs to the technical field of heavy oil exploitation, and particularly relates to a downhole steam generator and a thermal recovery system. Background Art

[0002] At present, the main heavy oil thermal recovery methods are steam soaking, steam flooding and SAGD. All three methods require the construction of a steam station on the ground. The steam generated by the steam station is transported through the ground steam transmission pipeline to each injection well, and then through the tubing in each injection well to the target oil layer underground. The high-temperature steam is used to reduce the viscosity of the crude oil for exploitation or displacement. The disadvantages of the traditional ground steam station steam injection thermal recovery technology are as follows:

[0003] (1) Large heat loss and low energy efficiency utilization rate: The heat loss generated by the ground steam generating equipment is about 15%-20%, the heat loss from the steam station to the injection wellhead is about 5%-10%, and the heat loss from the wellhead to the target oil layer is about 20%. The overall energy efficiency utilization rate is low.

[0004] (2) Low downhole steam dryness: The steam dryness at the outlet of the ground steam generating equipment is 75%. After being transported through the ground steam transmission pipeline and the injection wellbore, the steam dryness reaching the downhole is low, only 40%. It cannot meet the requirements of the thermal recovery process.

[0005] (3) Environmental pollution: When the ground steam generating equipment burns fossil fuels, a large amount of heat is carried away, generating SO X , NO X , particulate matter, polluting the surrounding environment.

[0006] (4) Poor mobility of equipment: The ground steam generating equipment and its auxiliary supporting devices are bulky and have poor mobility, which is not suitable for the operation requirements of scattered oil wells.

[0007] (5) Limited reservoir depth: Except that the application depth of steam soaking reaches 1800 meters, the steam flooding with higher recovery rate is mainly applied to reservoirs with a depth within 1200 meters. The use depth of the reservoir is limited.

[0008] (6) Increased wellbore input cost: The wellbore of the steam injection well needs to adopt special cementing techniques, such as heat-insulating casing, etc., and high temperature is likely to cause casing damage, resulting in an increase in workover costs.

[0009] To overcome the above deficiencies, an electromagnetic downhole steam generator for heavy oil thermal recovery is provided, which provides a new choice of development tool for heavy oil development and has far-reaching significance. Summary of the Invention

[0010] This application aims to at least to some extent solve the technical problem of low thermal energy utilization rate. To this end, this application provides a downhole steam generator and a thermal recovery system, which can eliminate the transmission process of steam from the ground to the downhole, avoid heat loss caused by the transmission process, effectively improve the thermal energy utilization rate, and achieve high-efficiency energy conservation and low-carbon emission reduction.

[0011] In a first aspect, an embodiment of this application provides a downhole steam generator, which is applied to a downhole formation and includes:

[0012] A metal heating element, which is provided with a fluid channel and a liquid inlet and a steam outlet communicating with both ends of the fluid channel, and is used to heat the fluid in the fluid channel;

[0013] An induction coil, which is arranged along the direction connecting both ends of the fluid channel, wound and sleeved on the circumference of the metal heating element, and the induction coil is used to pass an alternating current;

[0014] An insulating layer, which is sleeved on the induction coil.

[0015] In an optional implementation manner, the inner wall of the metal heating element is recessed with a thread groove, so that the fluid channel forms a thread structure.

[0016] In an optional implementation manner, it further includes an isolation layer, the isolation layer is sleeved on the circumference of the insulating layer, and the isolation layer is an isolation magnetic material.

[0017] In an optional implementation manner, it further includes an outer protection tube, and the outer protection tube is sleeved on the circumference of the isolation layer.

[0018] In an optional implementation manner, it further includes an insulating sleeve, and the insulating sleeve wraps the outer wall of the induction coil.

[0019] In an optional implementation manner, the inner walls of the metal heating element at the liquid inlet and the steam outlet are set to be of variable diameter, the inner diameter at the end of the liquid inlet is smaller than the inner diameter of the fluid channel, and the inner diameter at the end of the steam outlet is smaller than the inner diameter of the fluid channel.

[0020] In an optional implementation manner, it further includes an upper end cover and a lower end cover, the upper end cover is arranged at one end of the liquid inlet of the metal heating element, and the lower end cover is arranged at one end of the steam outlet of the metal heating element.

[0021] In an optional implementation manner, it further includes an electrical connector, the electrical connector is arranged on the upper end cover, the electrical connector is connected to the induction coil, and the electrical connector is used to electrically connect the induction coil.

[0022] In a second aspect, an embodiment of the present application provides a thermal recovery system, which includes a downhole part and a surface part. The downhole part includes the above-mentioned downhole steam generator, as well as a liquid infusion pipeline, a wiring, and a test pipeline. The liquid infusion pipeline is connected to the liquid inlet, the wiring is connected to the induction coil, and the other ends of the liquid infusion pipeline and the wiring extend and are connected to the surface part. The test pipeline extends from the surface part into the fluid channel.

[0023] In an alternative embodiment, the surface part includes a water purification treatment device, a surface power device, and a wellhead sealing device. The surface power device is connected to the wiring through the wellhead sealing device, and the water purification treatment device is connected to the liquid infusion pipeline through the wellhead sealing device.

[0024] As can be seen from the above technical solutions, the beneficial effects of the present application are as follows:

[0025] 1. The present application is applied to the downhole formation. In the formation, an alternating current is passed through the induction coil to generate an alternating magnetic field environment around the metal heating element. The induction coil is separated from the surrounding formation by an insulating layer to prevent the energized induction coil from being affected by the surrounding environment. Due to the characteristics of the metal, the metal heating element will generate heat under the change of the alternating magnetic field. The fluid entering the fluid channel through the liquid inlet can contact the metal heating element and increase in temperature. After passing through a section of the fluid channel and reaching the vaporization temperature, a vapor-liquid two-phase flow is formed. The fluid continuously heats up during the flow from the liquid inlet to the steam outlet, and finally forms steam when it reaches the steam outlet and is discharged from the steam outlet. In this way, the process of generating steam is completed after the fluid flows through the metal heating element, which can eliminate the transmission process of steam from the surface to the downhole, avoid heat loss caused by the transmission process, effectively improve the thermal energy utilization rate, and achieve high efficiency, energy conservation, low carbon emissions and emission reduction.

[0026] 2. The present application can provide fluid through the surface part, supply the fluid to the downhole steam generator through the liquid infusion pipeline, and at the same time electrically connect the induction coil through the wiring. In this way, when the fluid passes through the downhole steam generator, steam can be generated, and the generated steam can directly enter the target formation, thereby avoiding the loss of dryness, which is beneficial to reducing the viscosity of heavy oil, increasing the fluidity of heavy oil, and thus improving the recovery rate and the thermal energy utilization rate; at the same time, due to the adoption of the test pipeline, the steam temperature and pressure signals fed back by the sensors of the downhole test pipeline can be collected, so that dynamic electrical parameter regulation can be implemented in combination with the steam quality on the surface. By adjusting the power supply to the induction coil, real-time intelligent linkage regulation of the downhole steam generator can be achieved. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other embodiments and accompanying drawings can also be obtained based on these drawings.

[0028] Figure 1 The figure shows a schematic diagram of an embodiment of the downhole steam generator of the present invention;

[0029] Figure 2 The figure shows a schematic diagram of an embodiment of the thermal recovery system of the present invention;

[0030] Reference numerals: 100, downhole part; 110, downhole steam generator; 111, upper end cover; 112, lower end cover; 113, metal heating element; 1131, liquid inlet; 1132, steam outlet; 1133, fluid channel; 1134, thread groove; 114, induction coil; 115, insulating sleeve; 116, insulating layer; 117, isolation layer; 118, outer protection tube; 119, electrical connector; 120, liquid delivery pipeline; 130, wiring; 140, packer; 150, test pipeline; 200, ground part; 210, water purification treatment device; 220, ground power device; 230, wellhead sealing device. Detailed implementation manners

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] It should be noted that all directional indications in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0033] In the present invention, unless otherwise clearly defined and limited, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0034] In addition, in the present invention, descriptions such as "first" and "second" are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] The present application will be described below with reference to the accompanying drawings and specific embodiments:

[0036] Please refer to Figure 1 , in the first aspect embodiment of the present application, a downhole steam generator 110 is provided, which is applied to the downhole formation and is specifically used by being lowered into the downhole casing. Since the present application is applied to the formation, each component constituting the present application needs to meet certain temperature and pressure resistance indexes and be applicable to the formation environment. The downhole steam generator 110 includes: a metal heating element 113, an induction coil 114, and an insulating layer 116. The metal heating element 113 has a columnar or tubular structure with a certain length and is hollow inside. The metal heating element 113 is provided with a fluid channel 1133, a liquid inlet 1131 and a steam outlet 1132 that communicate with both ends of the fluid channel 1133. The fluid channel 1133 is arranged along the structural length direction of the metal heating element 113. The two open ends of the metal heating element 113 respectively form the above-mentioned liquid inlet 1131 and steam outlet 1132. When used downhole, the liquid inlet 1131 is located above the steam outlet 1132. The metal heating element 113 is made of high-temperature-resistant alloy steel, or other metal materials that are easy to conduct heat can also be used. The metal heating element 113 generates a large amount of heat under the action of an alternating magnetic field and is used to heat the fluid in the fluid channel 1133, ultimately forming wet saturated steam. By using the principle of electromagnetic induction for heating, it has a large calorific value, a high energy density, and the advantage of rapid heating. Moreover, induction heating is a non-contact heating method, which can greatly extend the service life of the device.

[0037] The induction coil 114 adopts a spiral structure and is made of hollow copper tube. Other coil materials can also be used. The induction coil 114 is arranged along the connection direction of the two ends of the fluid channel 1133, that is, it extends from one end close to the liquid inlet 1131 to the end close to the steam outlet 1132. The induction coil 114 is wound around and sleeved on the circumference of the metal heating element 113. The induction coil 114 is used to pass an alternating current. The two ends of the induction coil 114 can be connected to the power supply on the ground through the wiring 130, and the alternating current is provided for the induction coil 114 by the alternating power supply on the ground. The insulating layer 116 is made of insulating material, and mineral insulating materials such as asbestos and silicate can also be used. The insulating layer 116 is sleeved on the induction coil 114 in a cylindrical shape. Thus, a three-layer structure of the metal heating element 113, the induction coil 114 and the insulating layer 116 is formed from the inside to the outside. The three-layer structure is closely attached and can adopt an interference fit method, with stable connection. It should be noted that the length of the metal heating element 113 is related to the number of winding turns of the induction coil 114 and also related to the set current magnitude. If the current magnitude is designed, then the length of the metal heating element 113 is related to the number of winding turns. The more the number of turns, the lower the requirement for the length of the metal heating element 113. This is because the more the number of turns, the greater the magnetic field intensity generated by the induction coil 114. Under the alternating magnetic field, the more heat is generated by the metal heating element 113, and the better the heating effect on the passing water flow. The water flow can be heated to the steam state more quickly. Then, the length of the metal heating element 113 required for the water flow to change from the liquid state to the vapor-liquid two-phase flow and then to the steam state is relatively short. After the number of turns decreases, a longer metal heating element 113 is required to heat the water flow to the steam state.

[0038] In the prior art, steam thermal recovery is to generate steam on the ground and then inject the steam into the underground formation through a pipe string. However, this method has a low thermal energy utilization rate. The heat loss generated by the ground steam generation equipment is about 15%-20%, the heat loss from the steam station to the injection wellhead is about 5%-10%, and the heat loss from the wellhead to the target oil layer is about 20%. Generally speaking, the thermal energy loss caused by the transmission process is 25%-30%. In this application, it is applied to the underground formation. By passing an alternating current through the induction coil 114 in the formation, an alternating magnetic field environment is generated around the metal heating element 113. The induction coil 114 is separated from the surrounding formation through the insulating layer 116 to prevent the energized induction coil 114 from being affected by the surrounding environment. And for the metal heating element 113, due to the characteristics of the metal, it will generate heat under the change of the alternating magnetic field. The fluid entering the fluid channel 1133 through the liquid inlet 1131 can contact the metal heating element 113 to increase the temperature. After passing through a section of the fluid channel 1133 and rising to the vaporization temperature, a vapor-liquid two-phase flow is formed. The fluid continuously heats up during the flow from the liquid inlet 1131 to the steam outlet 1132, and finally forms steam when it reaches the steam outlet 1132 and is discharged from the steam outlet 1132. In this way, the fluid completes the process of generating steam after flowing through the metal heating element 113, which can eliminate the transmission process of steam from the ground to the underground, avoid heat loss caused by the transmission process, effectively improve the thermal energy utilization rate, and achieve high-efficiency energy conservation and low-carbon emission reduction.

[0039] In an alternative embodiment, the inner wall of the metal heating element 113 is recessed with a thread groove 1134. The thread groove 1134 is spiral and extends from one end to the other end of the fluid channel 1133, so that the fluid channel 1133 forms a thread structure. The thread groove 1134 plays a role in guiding the fluid inside the metal heating element 113, enabling the water to flow through the inner wall of the metal heating element 113 in a spiral acceleration form, increasing the liquid kinetic energy, and allowing the water flow to exchange heat with the metal heating element 113 more fully, thus improving the heat exchange efficiency. In an alternative embodiment, the inner walls of the metal heating element 113 at the liquid inlet 1131 and the steam outlet 1132 are of variable diameter. The inner diameter at the end of the liquid inlet 1131 is smaller than the inner diameter of the fluid channel 1133, and the inner diameter at the end of the steam outlet 1132 is smaller than the inner diameter of the fluid channel 1133. That is, the liquid inlet 1131 adopts an expanded diameter design, and the expansion can cause water body disturbance and increase the kinetic energy, making the water entering the fluid channel 1133 easier to flow along the thread groove 1134. While the steam outlet 1132 adopts a reduced diameter design, and the necking can increase the pressure of the steam and prevent the phenomenon that the bottom hole cannot be injected due to excessive pressure.

[0040] In an alternative embodiment, the downhole steam generator 110 further includes an insulating sleeve 115 that wraps around the outer wall of the induction coil 114. The insulating sleeve 115 is made of an insulating material to form insulation outside the induction coil 114. With the use of the insulating sleeve 115 and the insulating layer 116, a double-layer insulation protection is formed outside the induction coil 114, ensuring that the induction coil 114 does not leak electricity, operates efficiently, and has high safety performance. In an alternative embodiment, a shielding layer 117 is further included. The shielding layer 117 is sleeved circumferentially on the insulating layer 116. The shielding layer 117 is a magnetic shielding material such as ferrite, aluminum, nickel-iron alloy, etc. The shielding layer 117 can block the electromagnetic field inside the shielding layer 117. The use of the shielding layer 117 not only reduces the heat loss of the metal heating element 113 and further improves the heating efficiency, but also prevents the electromagnetic field generated by the electromagnetic coil from entering the casing, protects the casing from high-temperature casing deformation, and avoids the influence of the alternating magnetic field on the metal outside the shielding layer 117. In an alternative embodiment, an outer protective tube 118 is further included. The outer protective tube 118 is sleeved circumferentially on the shielding layer 117. The outer protective tube 118 can be made of a corrosion-resistant metal material such as stainless steel. Thus, the downhole steam generator 110 has a multi-layer structure, which from the inside to the outside are the metal heating element 113, the induction coil 114, the insulating layer 116, the shielding layer 117, and the outer protective tube 118. The adjacent layers are tightly fitted, such as by an interference fit method, which ensures that the induction coil 114 does not contact the external environment and does not shift, and can be energized and operate in a relatively stable state.

[0041] In an alternative embodiment, the downhole steam generator 110 further includes an upper end cover 111 and a lower end cover 112. Both the upper end cover 111 and the lower end cover 112 are circular disks. The upper end cover 111 and the lower end cover 112 are made of insulating materials. The upper end cover 111 is disposed at one end of the liquid inlet 1131 of the metal heating element 113, and the upper end cover 111 is provided with an opening communicating with the liquid inlet 1131. The lower end cover 112 is disposed at one end of the steam outlet 1132 of the metal heating element 113, and the lower end cover 112 is provided with an opening communicating with the steam outlet 1132. The outer diameters of the upper end cover 111 and the lower end cover 112 match the outer diameter of the outer protection tube 118. In this way, the upper end cover 111 and the lower end cover 112 are respectively connected to both ends of the metal heating element 113, the induction coil 114, the insulating layer 116, the isolation layer 117 and the outer protection tube 118. The upper end cover 111 and the lower end cover 112 are respectively connected at both ends by bonding, screw connection or other connection methods convenient for fixing. The upper end cover 111 and the lower end cover 112 can play a protective role and ensure the long-term service life of the structure under complex downhole working conditions. In an alternative embodiment, it further includes an electrical connector 119. The electrical connector 119 is disposed on the upper end cover 111. A through hole is opened on the upper end cover 111, and the electrical connector 119 is disposed therein. The electrical connector 119 is connected to the induction coil 114 on the inner side of the device for electrically connecting the induction coil 114. The outer side of the electrical connector 119 is connected to a cable, and is connected to a power source on the ground through the cable.

[0042] The working process of this embodiment is as follows: Water enters the fluid channel 1133 of the metal heating element 113 through the upper end cover 111 and then through the liquid inlet 1131. The water flows in a spiral rotation form along the thread groove 1134. While the thread groove 1134 fully increases the internal disturbance of the fluid, it enables the water to be in full contact with the metal heating element 113, improving the heat transfer performance and heat transfer uniformity. Electric power is transmitted into the induction coil 114 wrapped by the insulating layer 116 in the downhole steam generator 110 through the electrical connector 119 on the upper end cover 111. After the induction coil 114 is energized, an alternating magnetic field is generated, causing the metal heating element 113 to generate a large amount of heat. A large amount of high-temperature and high-pressure steam is generated instantly when the water flow passes through the high-temperature metal heating element 113. Utilizing the expansion pressure of the steam during vaporization, it is directly transmitted downward to reach the steam outlet 1132, and finally sprays out from the steam outlet 1132 and is directly pressed into the heavy oil reservoir.

[0043] Please refer to Figure 2, in the embodiments of the second aspect of the present application, a thermal recovery system is provided, which includes a downhole part 100 and a surface part 200. The downhole part 100 includes the above-mentioned downhole steam generator 110, as well as an infusion pipeline 120, a wiring 130, a test pipeline 150 and a packer 140. The infusion pipeline 120 uses pipe fittings for downhole use, such as oil pipes. The wiring 130 uses cable wires. The test pipeline 150 is a logging tool with sensors and can monitor the temperature and pressure downhole. The system also includes an interface device. The interface device is in the form of a double-joint structure and can allow both the cable wire and the infusion pipeline 120 to pass through. The interface device is fixed on the upper end cover 111. The joint device can be fixed on the upper end cover 111 by screws. After passing through the interface device, the infusion pipeline 120 is communicated with the liquid inlet 1131. After passing through the interface device, the wiring 130 is connected to the induction coil 114. The other ends of the infusion pipeline 120 and the wiring 130 extend and are connected to the surface part 200. The test pipeline 150 extends from the surface part 200 into the fluid channel 1133. Through the test pipeline 150, the real-time monitoring of the steam temperature and pressure can be realized. The packer 140 is arranged between the downhole steam generator 110 and the formation. Specifically, the packer 140 is sleeved on the outer wall of the outer protection pipe 118 and is fixed at the required downhole position through the packer 140.

[0044] In the existing steam generation system, a steam generation device is set on the ground, and then the steam is transported to the downhole formation through pipelines. The steam generated in this way not only has a low thermal energy utilization rate, but also has a serious dryness loss when the steam reaches the target formation, which is not conducive to the viscosity of heavy oil at the bottom of the well. In the present application, the surface part 200 can provide fluid, and the fluid is provided to the downhole steam generator 110 through the infusion pipeline 120. At the same time, the induction coil 114 is electrically connected through the wiring 130. In this way, when the fluid passes through the downhole steam generator 110, steam can be generated, and the generated steam can directly enter the target formation, thus avoiding dryness loss, being beneficial to reducing the viscosity of heavy oil, increasing the fluidity of heavy oil, and further improving the recovery rate and the thermal energy utilization rate. At the same time, due to the use of the test pipeline 150, the steam temperature and pressure signals fed back by the sensors of the downhole test pipeline 150 can be collected. In this way, dynamic electrical parameter regulation can be implemented in combination with the steam quality on the ground. Through the power supply adjustment of the induction coil 114, the real-time intelligent linkage regulation of the downhole steam generator 110 can be realized.

[0045] In an alternative embodiment, the surface portion 200 includes a water purification treatment device 210, a surface power device 220, and a wellhead sealing device 230. The wellhead sealing device 230 uses a conventional seal. The surface power device 220 is connected to the wiring 130 through the wellhead sealing device 230. The surface power device 220 can use a power source that can provide alternating current. For example, the surface power device 220 is a power supply interface device for industrial alternating current. The surface power device 220 can provide alternating current to the downhole through the wiring 130. The wiring 130 uses a cable, and a special cable can be used. One end of the cable is connected to the power source, and the other end passes through the wellhead sealing device 230 and enters the casing, and then extends to the bottom of the well and is connected to the electrical connector 119, so as to transmit the alternating current on the surface to the induction coil 114; the water purification treatment device 210 is connected to the infusion pipeline 120 through the wellhead sealing device 230. The water purification treatment device 210 is a conventional water purification device. After the water flows through the water purification treatment device 210, the calcium and magnesium ions in the water are mainly reduced, the water is softened, and then the water is connected to the wellhead sealing device 230, enters the casing, and then enters the liquid inlet 1131 of the downhole steam generator 110 through the infusion pipeline 120 from the water supply port of the sealed wellhead, and also reduces the possibility of scaling in the fluid passage 1133.

[0046] The working process of this embodiment is as follows: The water flows through the surface water purification treatment device 210, enters from the water supply inlet of the wellhead sealing device 230, and is transmitted to the liquid inlet 1131 of the downhole steam generator 110 through the infusion pipeline 120. The power passes through the surface power device 220, enters from the power supply inlet of the wellhead sealing device 230, is transmitted to the interface device through the special cable, and is connected to the electrical connector 119 after passing through the interface device; the test pipeline 150 is connected to the surface power device 220, enters from the power supply inlet of the wellhead sealing device 230, descends to the steam generator and then passes through the fluid passage 1133 and extends out of the bottom of the steam generator; the water directly generates the required high-quality steam in the fluid passage 1133 in the downhole and injects it into the target layer. The test pipeline 150 monitors the steam temperature and pressure in real time and feeds back to the surface power device 220, and the surface power device 220 adjusts the current of the cable to achieve intelligent linkage control of the electrical parameters.

[0047] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", "optional examples" or "optional implementation manners", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0048] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0049] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. An underground steam generator, characterized in that, Applied to the underground formation, including: A metal heating element (113) is provided with a fluid channel (1133) and a liquid inlet (1131) and a steam outlet (1132) communicating with both ends of the fluid channel (1133), and is used to heat the fluid in the fluid channel (1133); An induction coil (114) is arranged along the direction of the connection line of both ends of the fluid channel (1133), wound and sleeved on the circumference of the metal heating element (113), and the induction coil (114) is used to pass an alternating current; An insulating layer (116) is sleeved on the induction coil (114).

2. The downhole steam generator according to claim 1, wherein, The inner wall of the metal heating element (113) is recessed with a thread groove (1134), so that the fluid channel (1133) forms a thread structure.

3. The downhole steam generator according to claim 1, wherein, It further includes an isolation layer (117), the isolation layer (117) is sleeved on the circumference of the insulating layer (116), and the isolation layer (117) is a magnetic isolation material.

4. The downhole steam generator according to claim 3, wherein, It further includes an outer protection tube (118), the outer protection tube (118) is sleeved on the circumference of the isolation layer (117).

5. The downhole steam generator according to claim 1, characterized in that, It further includes an insulating sleeve (115), the insulating sleeve (115) wraps the outer wall of the induction coil (114).

6. The downhole steam generator according to claim 1, characterized in that, The inner walls of the metal heating element (113) at the liquid inlet (1131) and the steam outlet (1132) are set to have variable diameters. The inner diameter at the end of the liquid inlet (1131) is smaller than the inner diameter of the fluid channel (1133), and the inner diameter at the end of the steam outlet (1132) is smaller than the inner diameter of the fluid channel (1133).

7. The downhole steam generator according to any one of claims 1-6, characterized in that, It further includes an upper end cover (111) and a lower end cover (112). The upper end cover (111) is arranged at one end of the liquid inlet (1131) of the metal heating element (113), and the lower end cover (112) is arranged at one end of the steam outlet (1132) of the metal heating element (113).

8. The downhole steam generator according to claim 7, wherein It further includes an electrical connector (119), the electrical connector (119) is arranged on the upper end cover (111), the electrical connector (119) is connected to the induction coil (114), and the electrical connector (119) is used to electrically connect the induction coil (114).

9. A thermal recovery system, characterized in that, It includes an underground part (100) and a ground part (200). The underground part (100) includes the underground steam generator (110) according to any one of claims 1-8, and an infusion pipeline (120), a wiring (130) and a test pipeline (150). The infusion pipeline (120) communicates with the liquid inlet (1131), the wiring (130) is connected to the induction coil (114), the other ends of the infusion pipeline (120) and the wiring (130) extend and are connected to the ground part (200), and the test pipeline (150) extends from the ground part (200) into the fluid channel (1133).

10. The thermal recovery system according to claim 9, wherein The ground part (200) includes a water purification treatment device (210), a ground power device (220), and a wellhead sealing device (230). The ground power device (220) is connected to the wiring (130) through the wellhead sealing device (230), and the water purification treatment device (210) is connected to the infusion pipeline (120) through the wellhead sealing device (230).

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