In-situ leaching uranium mining device and method for improving leaching reaction rate

Abstract

The invention discloses an in-situ leaching uranium mining device and method for increasing the leaching reaction rate, and belongs to the technical field of uranium mining. The device adopts an inner-layer, middle-layer and outer-layer concentric shaft structure. A leaching agent is injected from a shaft annulus and flows through an annular heater installed on the outer side of an inner shaft to be heated for the first time; and a pressure control device is arranged at the top of the inner shaft. The leaching agent is driven to be pressed into the inner shaft from the bottom of the inner shaft through cyclic operation of intermittent high-pressure injection of the middle shaft and pressure reduction and pressurization of the inner shaft, flows through the heater area again to achieve secondary heating and is finally injected into the ore bed through the filter. And an annular space between the outer shaft and the middle shaft is filled with a foaming heat-insulating material. Through the synergistic effect of underground in-situ dual heating, a three-layer heat preservation structure and dynamic pulse pressure injection, heat loss is remarkably reduced, the problems of corrosion and scaling of metal elements are solved, and the leaching reaction rate and the coverage range of a leaching agent on uranium ore are greatly increased.

Description

Technical Field

[0001] This invention relates to the field of mineral leaching mining technology, and in particular to an in-situ leaching uranium mining apparatus and method for improving the leaching reaction rate. Background Technology

[0002] In-situ leaching is currently the mainstream technology for uranium mining. Its principle is to inject a prepared leaching agent (such as an acid or alkali solution) into the underground ore-bearing layer through an injection well. The leaching agent migrates in the ore layer and reacts chemically with the uranium minerals. The resulting uranium-bearing leachate is then pumped to the surface through a pumping well.

[0003] At room temperature, the leaching reaction rate of uranium minerals is slow, resulting in long mining cycles and low resource recovery rates. To improve efficiency, existing technologies typically employ "surface heating," where the leaching agent is heated to the target temperature at a surface station before being injected into the wellbore. However, during the transport of the leaching agent from the surface through the wellbore hundreds of meters deep, a significant amount of heat is lost to the surrounding low-temperature rock layers (non-target layers), resulting in the actual fluid temperature reaching the ore layer being far lower than the design temperature, leading to extremely low energy efficiency. Furthermore, the increased chemical activity of the heated leaching agent significantly accelerates corrosion of the wellbore wall over long distances, shortening its lifespan. Simultaneously, temperature changes and pressure fluctuations can cause minerals in the fluid to precipitate and form scale on the inner wall of the wellbore, clogging filters and severely impacting injection capacity.

[0004] In addition, for thick mineral formations, the temperature difference when the surface heating fluid reaches different depths at the bottom of the well is large, resulting in uneven leaching reactions within the mineral formation.

[0005] Although there have been attempts at downhole heating in existing technologies (such as microwave heating and induction heating), the equipment is often complex and expensive, and there is a lack of precise control over the injection flow field, making it difficult to solve the problems of blockage and poor permeability while heating. Summary of the Invention

[0006] In view of this, this application provides an in-situ leaching uranium mining apparatus and method to improve the leaching reaction rate. The main objective is to solve the technical problems of high heat loss from surface heating, severe corrosion of metal components, and easy clogging during liquid injection in the prior art.

[0007] According to a first aspect of the present invention, an in-situ leaching uranium mining apparatus for improving the leaching reaction rate is provided, comprising an inner wellbore, a middle wellbore, and an outer wellbore concentrically arranged. The outer wellbore serves as the outermost protective structure, forming an outer annular cavity with the middle wellbore. This cavity is filled with a high-efficiency thermal insulation material (such as polyurethane foam) to block the radial conduction of heat to non-target formations.

[0008] The intermediate wellbore serves as the main injection channel, with an open upper end for connecting to the surface injection pipeline and a closed lower end. A mid-annular cavity is formed between the intermediate and inner wellbores. The inner wellbore is located inside the intermediate wellbore, with an open lower end, allowing fluid from the mid-annular cavity to enter the inner wellbore from the bottom. The inner wellbore is also located inside the intermediate wellbore, with an open lower end, allowing communication between the mid-annular cavity and the inner wellbore's internal space at the bottom. A pressure control device is installed at the upper end of the inner wellbore to regulate the air pressure within it. A heater is installed on the outer wall of the inner wellbore, located at the corresponding depth of the ore layer. Filter assemblies are installed at the corresponding ore layer positions in the inner, intermediate, and outer wellbores, configured to allow heated leaching agent to flow out from the inner wellbore and inject into the ore layer.

[0009] Furthermore, the heater is an annular electric heater, which is fixedly connected to the outer wall of the inner well casing; The central annular cavity serves as the first-stage heating channel for the leaching agent. As the leaching agent flows down along the central annular cavity, it passes over the surface of the heater for initial heating.

[0010] Furthermore, the filter assembly includes through-hole structures and transverse connecting pipes disposed on the inner wellbore, middle wellbore, and outer wellbore; the filter assembly is located above the heater, so that when the leaching agent flows back upward from the bottom of the inner wellbore and is discharged, it flows again through the area where the heater is located for secondary heating.

[0011] Furthermore, the inner wellbore, the middle wellbore, and the outer wellbore are all segmented structures; the inner wellbore and the middle wellbore are connected and fixed by several sections of second fixing plates; the middle wellbore and the outer wellbore are connected and fixed by several sections of first fixing plates. The lower inner well section where the heater is located is detachably connected to the upper inner well section where the heater is not located, so as to facilitate the maintenance and replacement of the heater.

[0012] Furthermore, the diameter of the outer well casing is larger than the diameter of the middle well casing, and the diameter of the middle well casing is larger than the diameter of the inner well casing; preferably, the diameter of the inner well casing is 20cm-30cm, the diameter of the middle well casing is 30cm-40cm, and the diameter of the outer well casing is 40cm-50cm.

[0013] Furthermore, the insulation material filling the outer annular cavity is a foamed insulation material, which is used to reduce radial heat loss of the solvent during the wellbore transmission process.

[0014] Furthermore, the pressure control device includes an openable and closable sealing cover disposed at the top of the inner wellbore and a pressure regulating valve that cooperates with the sealing cover, used to control the inner wellbore to be in a closed pressurized state or an open depressurized state during the injection process.

[0015] Furthermore, according to a second aspect of the present invention, a method for in-situ leaching uranium extraction using the apparatus described in any of the foregoing inventions is provided, comprising the following steps: S1. Environment setup: Lower the device into the injection hole and align the heater and filter assembly with the target mineralized aquifer; S2. Start heating: Turn on the heater to bring the local area downhole to the preset reaction temperature; S3. Intermittent pulse injection: Execute the cyclic injection process.

[0016] Furthermore, the injection process includes the following steps: S31, depressurization and fluid suction: open the pressure control device at the top of the inner wellbore to depressurize, and at the same time stop injecting solvent into the middle wellbore. Use the formation pressure difference to make the fluid in the aquifer flow in the opposite direction or stand still. S32, Pressurization preparation: Close the pressure control device at the top of the inner wellbore to create a closed space in the inner wellbore; S33, High-pressure injection: High-pressure injection of leaching agent into the middle wellbore. The leaching agent descends along the middle annular cavity, is heated for the first time on the surface of the heater, and then enters the interior of the inner wellbore from the bottom of the inner wellbore. S34. Secondary heating and penetration: As the injection pressure in the middle wellbore is maintained, the solvent entering the inner wellbore rises and is driven by compressed gas or water, and is squeezed outward through the filter assembly. During this process, the solvent is heated a second time in the heating zone where the heater is located, and is finally injected into the ore layer in a high temperature and high pressure state.

[0017] Furthermore, in step S33, the injection of the solvent adopts a gradual decompression strategy, that is, first injecting at the maximum set pressure, and then gradually reducing the injection flow rate and pressure until the injection stops, and proceeding to the next round of step S31.

[0018] Furthermore, the method utilizes the depressurization and pressurization circulation of the inner wellbore to generate pulsed hydraulic waves in the ore layer, thereby breaking up scale or gas blockages in the ore layer pores and improving the effective permeability of the leaching agent.

[0019] Beneficial effects: This invention places the heating source directly at the bottom of the well, in conjunction with an outer insulation structure, virtually eliminating heat loss along the process and ensuring that the leaching agent contacts the ore at the optimal reaction temperature. The leaching agent passes through the heater twice during the "downward" and "outward" processes, resulting in thorough heat exchange and more precise temperature control.

[0020] The leaching agent in this application is only kept at a high temperature in the bottom heating section, while the fluid temperature in the upper wellbore is lower, significantly reducing the risk of corrosion over long wellbore distances. Furthermore, the unique intermittent injection and internal well breathing-type pressure-changing operation of this application can generate hydraulic turbulence, effectively preventing filter scaling and clogging, and can extend the reach of the leaching agent in low-permeability formations through pressure pulses.

[0021] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0022] The accompanying drawings, as part of this invention, are provided to further illustrate the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation thereof. Clearly, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0023] In the attached diagram: Figure 1 This is a schematic diagram of the complete well structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the wellbore provided in an embodiment of the present invention; Figure 3 This is a partially enlarged schematic diagram of the bottom of the wellbore provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the inner wellbore structure provided in an embodiment of the present invention; Figure 5 This is a partially enlarged schematic diagram of the bottom of the inner wellbore provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the complete well profile structure of the device provided in the embodiment of the present invention; Figure 7 This is a flowchart of the in-situ leaching uranium mining method for improving the leaching reaction rate provided in the embodiments of the present invention; Figure 8 This is a further detailed flowchart of the in-situ leaching uranium mining method for improving the leaching reaction rate provided in the embodiments of the present invention.

[0024] Icon labels: 1. Middle wellbore, 2. Inner wellbore, 3. Outer wellbore, 34. Heater, 35. Outer annular cavity, 36. Middle annular cavity.

[0025] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0027] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "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 limiting this invention.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] Example 1 The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0030] like Figure 1 and Figure 6As shown, this embodiment provides an in-situ leaching uranium mining device to improve the leaching reaction rate. It adopts a three-layer concentric tubular structure design, including an inner wellbore 2, a middle wellbore 1, and an outer wellbore 3, all concentrically arranged. An outer annular cavity 35 is formed between the outer wellbore 3 and the middle wellbore 1; a middle annular cavity 36 is formed between the middle wellbore 1 and the inner wellbore 2. The middle annular cavity 36 serves as the first-stage heating channel for the leaching agent, which flows down the middle annular cavity 36 and is initially heated by passing over the surface of the heater 34. The upper end of the middle wellbore 1 is used for injecting the leaching agent, while the lower end is closed. The inner wellbore 2 is located inside the middle wellbore 1, and its lower end is an open structure, allowing the internal space of the middle annular cavity 36 to communicate with the internal space of the inner wellbore 2 at the bottom. The upper end of the inner shaft 2 is provided with a pressure control device for adjusting the air pressure inside the inner shaft 2; a heater 34 is provided on the outer wall of the inner shaft 2, and the heater 34 is located at the corresponding depth of the ore layer; the inner shaft 2, the middle shaft 1 and the outer shaft 3 are all provided with filter assemblies at the corresponding ore layer positions, and the filter assemblies are configured to allow the heated solvent to flow out from the inside of the inner shaft 2 and be injected into the ore layer.

[0031] In one feasible embodiment, the diameter of the outer well casing 3 is larger than the diameter of the middle well casing 1, and the diameter of the middle well casing 1 is larger than the diameter of the inner well casing 2. Specifically, the dimensions and materials of the inner well casing 2, middle well casing 1, and outer well casing 3 in this device are as follows: to balance mechanical strength and heating space, the preferred design dimensions are: the inner well casing 2 has a diameter of approximately 25 cm, the middle well casing 1 has a diameter of approximately 35 cm, and the outer well casing 3 has a diameter of approximately 45 cm. The gap between the outer well casing 3 and the middle well casing 1 (i.e., the outer annular cavity 35) is approximately 5 cm, and this space is filled with foamed insulation material to form a heat insulation barrier. The materials of the inner well casing 2, middle well casing 1, and outer well casing 3 are preferably fiberglass or special stainless steel resistant to acid and alkali corrosion.

[0032] In one feasible embodiment, the connection structure of the device of this application is as follows: for ease of installation and maintenance, the inner well casing 2, the middle well casing 1, and the outer well casing 3 all adopt a segmented structure. The inner well casing 2 and the middle well casing 1 are connected by two sections of second fixing plates ( Figure 6 As shown, radial support connections are made to ensure uniform annulus. The middle wellbore 1 and the outer wellbore 3 are connected by four sections of the first fixing plate. Crucially, the heater 34 is a ring-shaped electric heater, welded and fixed to the outer wall of the inner wellbore 2. The wellbore section containing the heater 34 is connected to the upper wellbore by flanges or threads in sections. If the heater 34 malfunctions, this section can be removed and replaced separately.

[0033] In one feasible implementation, the device flow channel and heating design of this application are as follows: Middle shaft 1: as shown... Figure 2 and Figure 3As shown, the upper end of the middle wellbore 1 is open for fluid injection, while the lower end is closed. This means that the injected fluid cannot leak directly from the bottom of the middle wellbore 1, but can only enter the annulus between it and the inner wellbore 2. Inner wellbore 2: As shown... Figure 4 and Figure 5 As shown, the inner wellbore 2 is located at the very center. Its most notable feature is its open bottom. This constitutes a fluid reversal point. A pressure control device (not shown in the figure, but could be an electrically controlled valve) is located at the top of the inner wellbore 2 to control whether the inner wellbore is open to the atmosphere (pressure reduction) or closed (pressure increase). Heater 34: Arranged in an annular groove or dedicated location on the outer wall of the inner wellbore 2 (e.g., Figure 4 Located at the depth of the ore layer. Filter assembly: Positioned above heater 34, it allows the leaching agent to flow back upwards from the bottom of the inner wellbore 2, undergoing secondary heating as it passes through the area where heater 34 is located. Corresponding through holes are formed on the walls of the inner wellbore 2, middle wellbore 1, and outer wellbore 3, which are connected by a transverse short pipe, forming the sole outlet for injecting fluid into the formation. Thermal insulation material, specifically foamed insulation, is filled between the filter locations in the middle wellbore 2 and outer wellbore 3 to reduce radial heat loss of the leaching agent during wellbore transport.

[0034] Example 2 like Figure 8 As shown, this embodiment discloses a method for in-situ leaching uranium extraction using the apparatus described in Embodiment 1 above, comprising the following steps: S1. Environment setup: Lower the device into the injection hole and align the heater 34 and filter assembly with the target mineralized aquifer; S2. Start heating: Turn on the heater 34 to bring the local area downhole to the preset reaction temperature; S3. Intermittent pulse injection: Execute the cyclic injection process.

[0035] In one feasible implementation, the injection process includes the following steps: S31, depressurization and fluid aspiration: open the pressure control device at the top of the inner wellbore 2 to depressurize, and at the same time stop injecting the solvent into the middle wellbore 1, using the formation pressure difference to make the fluid in the aquifer flow back or stand still; S32, pressurization preparation: close the pressure control device at the top of the inner wellbore 2 to make the inner wellbore 2 form a closed space. S33, High-pressure injection: High-pressure injection of leaching agent into the middle wellbore 1. The leaching agent descends along the middle annular cavity 36, is heated for the first time on the surface of the heater 34, and then enters the interior of the inner wellbore 2 from the bottom of the inner wellbore 2. S34. Secondary heating and penetration: As the injection pressure of the middle wellbore 1 is maintained, the solvent entering the inner wellbore 2 rises and is driven by compressed gas or water, and is squeezed outward through the filter assembly. During this process, the solvent is heated a second time in the heating area where the heater 34 is located, and is finally injected into the ore layer in a high temperature and high pressure state.

[0036] In this embodiment, in step S33, the injection of the leaching agent adopts a gradual decompression strategy, that is, first injecting at the maximum set pressure, and then gradually reducing the injection flow rate and pressure until the injection stops, and proceeding to the next round of step S31.

[0037] Example 3 As a further refinement of Example 2, the injection and heating method of this application is as follows: The process flow for in-situ leaching uranium extraction using the above-mentioned device is as follows, the core of which is "intermittent cyclic injection": Step 1: Initial setup and environment construction. Lower the device into the wellbore and cement the outer wall (if necessary). The insulation material inside the outer annular cavity 35 ensures thermal isolation between the wellbore and the formation.

[0038] Step 2: First Stage – Reduced Pressure Aspiration (Cleaning) The specific operation is as follows: Open the pressure control device at the top of the inner wellbore 2 to allow it to be vented to the atmosphere or connected to negative pressure; at the same time, stop injecting fluid into the middle wellbore 1. The working principle is as follows: at this time, the pressure inside the middle wellbore 1 decreases, the formation pressure may be greater than the bottom hole pressure, and a small amount of fluid in the aquifer may flow back into the filter, which helps to flush out the blockages on the outside of the filter.

[0039] Step 3: Second Stage – Pressurization and First-Stage Heating Specific operation: Close the top of the inner wellbore 2 to create a dead space. Inject the leaching agent under high pressure into the annular cavity 36 between the middle wellbore 1 and the inner wellbore 2 using a surface pump. Principle: The leaching agent flows downwards along the annular cavity 36. When it flows past the heater 34 installed on the outer wall of the inner wellbore 2, the first heat exchange occurs, and the fluid temperature rises. Flow direction: Upon reaching the bottom, due to the closed bottom of the middle wellbore 1 and the open bottom of the inner wellbore 2, the fluid reverses and enters the internal space of the inner wellbore 2.

[0040] Step 4: Third Stage – Secondary Heating and Pulse Injection Specific procedure: continuous high-pressure injection.

[0041] The principle is as follows: the liquid level inside the inner wellbore 2 rises, compressing the air at the top (or the pressure rises sharply after the wellbore is filled with liquid). Driven by the pressure, the high-temperature solvent is forced outward from the inside of the inner wellbore 2 and discharged through the filter assembly (located in the area above the heater).

[0042] During this process, as the fluid flows out from inside the inner wellbore 2, it passes again through the pipe wall area (or the area adjacent to the heater) heated by the heater 34, achieving a second heating. Finally, the doubly heated solvent is injected into the ore layer at a higher pressure. The high temperature not only accelerates the chemical reaction, but the high-pressure pulse also helps to fracture micro-fractures and expand the affected volume.

[0043] Step 5: Loop Once the injection pressure of the inner wellbore 1 reaches the design limit or the injection volume meets the single pulse requirement, the injection is stopped, the top of the inner wellbore 2 is reopened to release pressure, and the next cycle begins.

[0044] Through this cycle of "heating-pressurization-injection-depressurization", this invention achieves a perfect combination of efficient in-situ heating and formation permeability enhancement, completely solving the pain points of traditional surface heating processes.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A ground leaching uranium mining apparatus for improving the leaching reaction rate, characterized in that, It includes concentrically set inner shaft (2), middle shaft (1) and outer shaft (3); An outer annular cavity (35) is formed between the outer wellbore (3) and the middle wellbore (1), and the outer annular cavity (35) is filled with heat insulation material; A central annular cavity (36) is formed between the central wellbore (1) and the inner wellbore (2). The upper end of the central wellbore (1) is used to inject the leaching agent, and the lower end is closed. The inner wellbore (2) is located inside the middle wellbore (1), and its lower end is an open structure, so that the middle annular cavity (36) and the internal space of the inner wellbore (2) are connected at the bottom. The upper end of the inner wellbore (2) is provided with a pressure control device for adjusting the air pressure inside the inner wellbore (2); A heater (34) is provided on the outer wall of the inner wellbore (2), and the heater (34) is located at the corresponding depth of the ore layer; The inner shaft (2), middle shaft (1) and outer shaft (3) are each equipped with a filter assembly at the corresponding ore layer position. The filter assembly is configured to allow heated leaching agent to flow out from the inside of the inner shaft (2) and be injected into the ore layer.

2. The apparatus according to claim 1, characterized in that, The heater (34) is an annular electric heater, which is fixedly connected to the outer wall of the inner wellbore (2); The central annular cavity (36) serves as the first-stage heating channel for the solvent. When the solvent flows down along the central annular cavity (36), it passes through the surface of the heater (34) for initial heating.

3. The apparatus according to claim 1, characterized in that, The filter assembly includes through-hole structures and transverse connecting pipes disposed on the inner well cylinder (2), the middle well cylinder (1) and the outer well cylinder (3); The filter assembly is located above the heater (34), so that when the solvent flows back up from the bottom of the inner wellbore (2) and is discharged, it flows again through the area where the heater (34) is located for secondary heating.

4. The apparatus according to claim 1, characterized in that, The inner wellbore (2), the middle wellbore (1) and the outer wellbore (3) are all segmented structures; The inner wellbore (2) and the middle wellbore (1) are connected and fixed by several sections of second fixing plates; The middle well casing (1) and the outer well casing (3) are connected and fixed by several sections of first fixing plates; The lower inner well section where the heater (34) is located is detachably connected to the upper inner well section where the heater (34) is not located.

5. The apparatus according to claim 1, characterized in that, The diameter of the outer wellbore (3) is greater than the diameter of the middle wellbore (1), and the diameter of the middle wellbore (1) is greater than the diameter of the inner wellbore (2).

6. The apparatus according to claim 1, characterized in that, The insulation material filled in the outer annular cavity (35) is a foamed insulation material, which is used to reduce the radial heat loss of the solvent during the wellbore transmission process.

7. The apparatus according to claim 1, characterized in that, The pressure control device includes an openable and closable sealing cover located on the top of the inner wellbore (2) and a pressure regulating valve that cooperates with the sealing cover, used to control the inner wellbore (2) to be in a closed pressurized state or an open depressurized state during the injection process.

8. A method for in-situ leaching uranium extraction using the apparatus according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Environment setup: Insert the device into the injection hole and align the heater (34) and filter assembly with the target mineralized aquifer; S2. Start heating: Turn on the heater (34) to bring the local area downhole to the preset reaction temperature; S3, Intermittent Pulse Injection: Executes the cyclic injection process.

9. The method according to claim 8, characterized in that, The injection process includes the following steps: S31, depressurization and fluid suction: open the pressure control device at the top of the inner wellbore (2) to depressurize, and at the same time stop injecting solvent into the middle wellbore (1). Use the formation pressure difference to make the fluid in the aquifer flow in the opposite direction or stand still. S32, Pressurization preparation: Close the pressure control device at the top of the inner wellbore (2) to make the inner wellbore (2) form a closed space; S33, High-pressure injection: High-pressure injection of leaching agent into the middle wellbore (1). The leaching agent descends along the middle annular cavity (36), and after being heated for the first time on the surface of the heater (34), it enters the interior of the inner wellbore (2) from the bottom. S34, Secondary heating and penetration: As the injection pressure in the middle shaft (1) is maintained, the solvent entering the inner shaft (2) rises and is driven by compressed gas or water, and is squeezed outward through the filter assembly. During this process, the solvent is heated a second time in the heating area where the heater (34) is located, and is finally injected into the ore layer in a high temperature and high pressure state.

10. The method according to claim 9, characterized in that, In step S33, the injection of the leaching agent adopts a gradual decompression strategy, that is, first injecting at the maximum set pressure, and then gradually reducing the injection flow rate and pressure until the injection stops, and proceeding to the next round of step S31.

Images