An in-situ leaching method for uranium

Abstract

The application discloses a kind of in-situ leaching uranium methods, the method can include: after well drilling construction to the ore bed bottom of uranium ore bed, open hole logging is carried out to determine the position of uranium ore bed, thickness and the reservoir physical property parameter of uranium ore bed;After downhole casing is lowered into drill hole, cement slurry is used to cement well;After washing well operation is implemented, shoot through casing and cement layer, so that casing is communicated with uranium ore bed;According to the thickness of uranium ore bed, the reservoir physical property parameter of uranium ore bed and well spacing, determine the target injection volume and target gas injection volume of injection agent rod string into uranium ore bed;CO2, water, O2 and water are sequentially injected into uranium ore bed by injection agent rod string in slug injection mode, and after reaching the target injection volume and target gas injection volume, the wellhead is closed for a predetermined time.The application improves the completion process and the sequence of injecting gas and water, increases the liquid injection volume and gas injection volume in the uranium ore bed by high-pressure injection, and ultimately improves the uranium recovery rate.

Description

Technical Field

[0001] This invention relates to the field of in-situ leaching uranium extraction technology, and particularly to a method for in-situ leaching uranium extraction. Background Technology

[0002] In-situ leaching is the most important mining method for sandstone-type uranium deposits, and CO2 and O2 in-situ leaching has become the preferred method for mining sandstone-type uranium deposits. This uranium mining process injects appropriate amounts of CO2 and O2 into the uranium-bearing sandstone-type uranium ore layer to ensure that tetravalent uranium minerals are oxidized into soluble hexavalent uranium. Specifically, O2 is used as an oxidant, oxidizing tetravalent uranium into soluble hexavalent uranium, while CO2 is used to form bicarbonate ions to complex the dissolved hexavalent uranium. Summary of the Invention

[0003] The inventors discovered that in existing technologies, CO2 and O2 are dissolved in water and injected into uranium ore formations through injection-production well casing. However, in low-porosity, low-permeability sandstone uranium ore formations, the seepage resistance is high, making it difficult for CO2 and O2 to be injected into the formation under normal pressure. Furthermore, existing mining methods use gravel-filled cementing and PVC casing for corrosion protection, which cannot support high-pressure injection. In view of the above problems, this invention is proposed to provide an in-situ leaching method for uranium mining that overcomes or at least partially solves the above problems. This method may include:

[0004] After drilling to the bottom of the uranium ore layer, open-hole logging is performed to determine the location, thickness, and reservoir properties of the uranium ore layer.

[0005] After the pressure-bearing anti-corrosion casing is inserted into the borehole after drilling, cement slurry is used for cementing.

[0006] After the well washing operation is carried out, a perforating gun is lowered into the borehole to the uranium ore layer. After penetrating the casing and cement layer, the gun is driven into the uranium ore layer at a predetermined distance so that the casing is connected to the uranium ore layer.

[0007] The injection rod string is lowered into the uranium ore layer to complete the preparation work for injection well construction;

[0008] The target water injection volume and target gas injection volume are determined based on the thickness of the uranium ore layer, the reservoir physical properties of the uranium ore layer, and the well spacing.

[0009] CO2, water, O2 and water are sequentially injected into the uranium ore layer under high pressure through the injection rod in a slug injection manner to reach the target water injection volume and the target gas injection volume, and then the wellhead is closed for a preset time.

[0010] Optionally, the method may further include: based on the geological interpretation results of the study area where the uranium ore layer is located, deploying a number of injection wells and production wells for the same ore body where the uranium ore layer is located, and performing the above-mentioned casing installation, cementing, perforation, injection rod injection, and high-pressure injection operations on all injection wells respectively;

[0011] After a preset time has elapsed since the wellhead was closed, the wellhead of the production well is opened, and uranium-containing leachate is pumped out through the production well.

[0012] Optionally, after pumping the uranium-containing leachate through the production well, the process may further include:

[0013] Repeat the high-pressure injection operation described above for the injection well until the target gas and water injection volumes are reached, then close the wellhead for a preset time.

[0014] The water injection volume is balanced with the liquid output volume of the production wells within the surrounding area of ​​the injection well.

[0015] Optionally, cementing with cement slurry may include: filling the space around the casing with cement using a forward grouting method until the cement slurry returns to the surface.

[0016] Optionally, after the injection rod is lowered into the uranium ore layer, the process may further include: installing a ground-based high-pressure liquid injection device and a high-pressure gas injection device;

[0017] The high-pressure gas injection equipment includes: a high-pressure oxygen injection equipment and a high-pressure carbon dioxide injection equipment.

[0018] Optionally, determining the target water injection volume and target gas injection volume for the uranium ore layer based on the thickness of the uranium ore layer, the reservoir properties of the uranium ore layer, and the well spacing may include:

[0019] The target water injection volume and target gas injection volume are determined based on the thickness of the uranium ore layer, the porosity included in the reservoir properties of the uranium ore layer, and the well spacing.

[0020] Optionally, the step of sequentially injecting CO2, water, O2, and water under high pressure into the uranium ore layer via the injection rod in a slug-type injection manner to reach the target water injection volume and the target gas injection volume, and then closing the wellhead for a preset time, may include:

[0021] CO2 is injected under high pressure into the uranium ore layer through the injection rod column;

[0022] Water is injected under high pressure into the uranium ore layer through the injection rod column;

[0023] O2 is injected under high pressure into the uranium ore layer through the injection rod column;

[0024] Water is injected under high pressure into the uranium ore layer through the injection rod column;

[0025] Repeat the above steps of high-pressure injection of CO2, water, O2 and water until the target water injection volume and the target gas injection volume are reached, then close the wellhead for a preset time.

[0026] Among them, the injection pressure during slug-type high-pressure water or gas injection is not greater than the critical fracture pressure of the uranium ore layer.

[0027] Optionally, the preset time is 7 to 10 days.

[0028] Optionally, the preset distance is 1 to 2 meters.

[0029] Optionally, the reservoir physical properties include: porosity, permeability, and / or pore distribution.

[0030] The beneficial effects of the above-mentioned technical solutions provided in the embodiments of the present invention include at least the following:

[0031] This invention provides a method for in-situ leaching uranium production, which may include: after drilling to the bottom plate of the uranium ore layer, performing open-hole logging to determine the location, thickness, and reservoir properties of the uranium ore layer; after inserting a pressure-bearing, corrosion-resistant casing into the borehole, cementing it with cement slurry; after well washing, inserting a perforating gun into the borehole to the uranium ore layer, penetrating the casing and cement layer, and then injecting it into the uranium ore layer a predetermined distance to ensure communication between the casing and the uranium ore layer; inserting an injection rod string into the uranium ore layer to complete the preparation work for injection well construction; determining the target water injection volume and target gas injection volume of the uranium ore layer based on the thickness, reservoir properties, and well spacing; and sequentially injecting CO2, water, O2, and water into the uranium ore layer under high pressure using the injection rod string in a slug injection manner until the target water injection volume and target gas injection volume are reached, and then closing the wellhead for a predetermined time. This invention improves the well completion process and the sequence of gas and water injection to achieve cyclic mining of uranium ore layers. High-pressure injection increases the amount of liquid and gas injected into the uranium ore layer, thereby ultimately improving the uranium recovery rate.

[0032] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0035] Figure 1 This is a flowchart of the in-situ leaching uranium extraction method provided in the embodiments of the present invention;

[0036] Figure 2 Here is a flowchart showing the specific execution process of step S16;

[0037] Figure 3 This is a schematic diagram of in-situ leaching uranium extraction provided in an embodiment of the present invention. Detailed Implementation

[0038] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0039] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "far," "near," "front," and "rear," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and 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, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] This invention provides a method for in-situ leaching uranium extraction, referring to... Figures 1-3 As shown, the method may include the following steps:

[0042] Step S10: After drilling to the bottom plate of the uranium ore layer, open-hole logging is performed to determine the location, thickness, and reservoir properties of the uranium ore layer.

[0043] In this step, drilling equipment is used to drill a well. After the drill bit reaches the bottom of the uranium ore layer in the study area, the drill is pulled out to create an open-hole geophysical exploration well. This geophysical exploration well can then determine the location, thickness, and reservoir physical properties of the uranium ore layer. These reservoir physical properties may include, but are not limited to, the following parameters: porosity, permeability, and / or pore distribution.

[0044] Step S11: After inserting the pressure-bearing anti-corrosion casing into the borehole after drilling, cement slurry is used for well cementing.

[0045] In this step, casing is lowered into the borehole after drilling is completed. The inventors selected a pressure-bearing, corrosion-resistant casing, which, compared to ordinary casing used in existing technologies, not only enables water and gas injection under high pressure but also prevents corrosion from water containing dissolved CO2 and O2. Simultaneously, cement slurry is used for cementing, which, compared to the gravel cementing process used in existing in-situ leaching uranium mining technologies, provides a sealing condition for high-pressure water and gas injection in the following steps. Compared to in-situ leaching methods that inject leaching agents (a general term for water containing dissolved CO2 and O2), the concentration of CO2 and O2 injected into the uranium ore layer increases, thereby improving the uranium recovery rate in in-situ leaching mining.

[0046] In practice, the above-mentioned cementing operation uses a forward grouting method to fill the space around the casing with cement until the cement slurry returns to the surface, thus completing the cementing operation. Of course, after the cementing operation is completed, the cementing quality needs to be inspected to conduct multiple inspections of the entire in-situ leaching uranium mining process, thereby improving the safety production factor and production efficiency.

[0047] Step S12: After performing well washing operations, lower the perforating gun into the borehole to the uranium ore layer, penetrate the casing and cement layer, and then penetrate the uranium ore layer at a predetermined distance to make the casing connected to the uranium ore layer.

[0048] This step involves perforation after cementing is completed. Before perforation, the wellbore and its casing are cleaned. Then, a perforating gun is lowered into the borehole to the uranium ore layer. The perforating gun penetrates the casing and cement layer, and then penetrates 1-2 meters into the uranium ore layer, thus connecting the casing and the uranium ore layer.

[0049] Step S13: Lower the injection rod into the uranium ore layer to complete the preparation work for injection well construction.

[0050] This step involves inserting a injection rod into the perforation formed after step S12, and injecting water and gas into the uranium ore layer through the injection rod.

[0051] Step S14: Install ground high-pressure liquid injection equipment and high-pressure gas injection equipment; wherein, the high-pressure gas injection equipment includes: high-pressure oxygen injection equipment and high-pressure carbon dioxide injection equipment.

[0052] This step involves installing the surface equipment after the underground device assembly is completed. The surface equipment in this embodiment of the invention differs significantly from existing leaching agent injection equipment. Existing injection equipment injects uranium ore into the ore layer via seepage, while in this embodiment, the injection and gas injection equipment are separate, and both are performed using high-pressure injection. The gas injection equipment in this embodiment can be divided into a high-pressure oxygen injection device and a high-pressure carbon dioxide injection device. Alternatively, the gas injection device can have two pipelines, connected to an oxygen storage tank and a carbon dioxide storage tank respectively, and connected to a pressurization device via a three-way valve to switch the injection sequence during oxygen and carbon dioxide injection.

[0053] Step S15: Determine the target water injection volume and target gas injection volume for the uranium ore layer based on the thickness of the uranium ore layer, the reservoir physical properties of the uranium ore layer, and the well spacing.

[0054] In practice, this step involves determining the target water injection volume and target gas injection volume of the uranium ore layer based on its thickness, porosity (including reservoir properties), and well spacing. This step is a calculation; before injection, the amounts of water, CO2, and O2 injected into the well need to be determined to extract uranium from the ore layer near the well. It should be noted that this step only needs to be performed before step S16, but can be performed after step S14 or after step S10. That is, the calculation of the target water injection volume and target gas injection volume can be performed after obtaining data such as the location, thickness, and reservoir properties of the uranium ore layer from geophysical exploration wells. This embodiment of the invention does not specifically limit the timing of step S15.

[0055] Step S16: CO2, water, O2 and water are sequentially injected into the uranium ore layer under high pressure through the injection rod in a slug injection manner to reach the target water injection volume and target gas injection volume, and then the wellhead is closed for a preset time.

[0056] In this step, the inventors use a slug injection method to inject gas and water in multiple injections until the target gas and water injection volumes are reached. After injection, the wellhead is closed for a preset time, such as 7-10 days, before liquid extraction (production) is carried out. This allows O2 to fully oxidize tetravalent uranium in the uranium ore layer, and the bicarbonate ions formed by CO2 to fully complex and dissolve hexavalent uranium in the uranium ore layer. In this embodiment of the invention, the inventors have fully considered the solubility of gas in water and no longer use leaching agents for in-situ leaching. Instead, gas and liquid are injected separately, increasing the gas content in the underground uranium ore layer, thereby increasing the recovery rate of low-porosity and low-permeability uranium ore layers and greatly improving uranium mining efficiency.

[0057] Specifically, in this step, refer to Figure 2 As shown, the following steps may be included:

[0058] Step S161: High-pressure CO2 injection into the uranium ore layer through the injection rod column.

[0059] After numerous experiments, the inventors fully considered that CO2 dissolves in water to form bicarbonate ions, making the water slightly acidic. This reacts with the formation matrix (uranium ore layer), increasing the formation permeability, thereby reducing the gas injection and water injection pressure. This allows for rapid guidance of the gas layer's direction and also improves the liquid supply capacity.

[0060] Step S162: High-pressure injection of water into the uranium ore layer through the injection rod column. This step involves injecting a certain amount of water into the uranium ore layer after a high-pressure CO2 injection, thus forming a water layer to seal off the injected CO2.

[0061] Step S163: High-pressure injection of O2 into the uranium ore layer via a injection rod. This step involves injecting O2 into the uranium ore layer under high pressure after CO2 and water injection, so as to oxidize tetravalent uranium minerals into soluble hexavalent uranium. The inventors inject O2 after the above steps S161 and S162 to avoid the formation of a gas lock layer (barrier layer) near the wellbore, which would hinder the injection of CO2 and water.

[0062] Step S164: High-pressure water is injected into the uranium ore layer through the injection rod column. After completing step S163 above, water is injected again to form a sealing layer, thereby providing a sealing basis for the next cycle of CO2 injection.

[0063] Step S165: Repeat the above steps of high-pressure injection of CO2, water, O2 and water to reach the target injection volume of water and gas, and then close the wellhead for a preset time; wherein, the injection pressure during slug-type high-pressure water or gas injection is not greater than the critical fracture pressure of the uranium ore layer.

[0064] In this embodiment of the invention, during slug-type high-pressure water and gas injection, the pressure value must be controlled within a preset range to avoid fracturing the uranium ore layer or nearby formations. Specifically, the high-pressure injection method in this embodiment overcomes the disadvantages of low porosity and low permeability in low-porosity, low-permeability uranium ore layers, solving the technical problem of injecting leaching agents into these layers via seepage injection. Furthermore, the slug-type high-pressure gas and water injection method provided in this embodiment effectively increases the injection volume, thereby improving overall uranium mining efficiency.

[0065] Step S17: Based on the geological interpretation results of the study area where the uranium ore layer is located, deploy a number of injection wells and production wells for the same ore body where the uranium ore layer is located, and perform the above-mentioned casing installation, cementing, perforation, injection rod installation and high-pressure injection operations on all injection wells respectively.

[0066] This step involves performing the above operations on all ore bodies containing the injection well within the study area to achieve mining of the entire ore body.

[0067] Step S18: After the wellhead is closed for a preset time, the wellhead of the production well is opened, and uranium-containing leaching fluid is pumped out through the production well.

[0068] When the uranium concentration in the leachate extracted in this step exceeds a certain ratio (e.g., 10 mg / L), the leachate is introduced into the refining system for further processing. The embodiments of the present invention will not be described in detail here.

[0069] Step S19: Repeat the above high-pressure injection operation on the injection well to reach the target gas injection volume and water injection volume, and then close the wellhead for a preset time; wherein, the water injection volume is balanced with the liquid output volume of the production wells in the surrounding area of ​​the injection well.

[0070] This step is a cyclic mining step. By repeatedly injecting CO2, water, O2, etc., and extracting uranium-containing leachate through the production well, the production fluid is injected repeatedly to achieve full development of the uranium ore layer. That is, after completing this step S19, the production fluid operation in step S18 above is continued to achieve full mining through multiple cycles.

[0071] The above-mentioned in-situ leaching uranium mining method provided in this embodiment of the invention improves the well completion process and the sequence of gas and water injection, thereby enabling cyclic mining of uranium ore layers. High-pressure injection increases the amount of liquid and gas injected into the uranium ore layer, thereby ultimately improving the uranium recovery rate.

[0072] The comparative embodiments of the above-described embodiments of the present invention are as follows:

[0073] Comparative Example 1

[0074] Step 1: After drilling to the bottom of the uranium ore layer, open-hole logging is performed to determine the location, thickness, and reservoir properties of the uranium ore layer.

[0075] Step 2: After running ordinary casing into the borehole after drilling, cement the well with gravel.

[0076] Step 3: After performing well washing operations, lower the perforating gun into the borehole to the uranium ore layer, penetrate the casing and gravel layer, and then penetrate the uranium ore layer at a predetermined distance to make the casing connected to the uranium ore layer.

[0077] Step 4: Lower the injection rod into the uranium ore layer to complete the preparation work for injection well construction.

[0078] Step 5: Install the ground injection leachate equipment.

[0079] Step 6: Determine the injection volume of leaching fluid based on the thickness of the uranium ore layer, the reservoir properties of the uranium ore layer, and the well spacing.

[0080] Step 7: Inject leaching fluid into the uranium ore layer through the injection rod in a seepage manner, and seal the wellhead for a preset time.

[0081] Step 8: Open the wellhead of the production well and pump out the uranium-containing leachate through the production well.

[0082] Comparative Example 2

[0083] Step 1: After drilling to the bottom of the uranium ore layer, open-hole logging is performed to determine the location, thickness, and reservoir properties of the uranium ore layer.

[0084] Step 2: After inserting the pressure-bearing anti-corrosion casing into the borehole after drilling, cement slurry is used for well cementing.

[0085] Step 3: After the well washing operation, lower the perforating gun into the borehole to the uranium ore layer, penetrate the casing and cement layer, and then penetrate the uranium ore layer at a predetermined distance to make the casing connected to the uranium ore layer.

[0086] Step 4: Lower the injection rod into the uranium ore layer to complete the preparation work for injection well construction.

[0087] Step 5: Install ground high-pressure liquid injection equipment and high-pressure gas injection equipment; the high-pressure gas injection equipment includes: high-pressure oxygen injection equipment and high-pressure carbon dioxide injection equipment.

[0088] Step 6: Determine the target water injection volume and target gas injection volume for the uranium ore layer based on the thickness of the uranium ore layer, the reservoir physical properties of the uranium ore layer, and the well spacing.

[0089] Step 7: Inject O2 into the uranium ore layer under high pressure through the injection rod column.

[0090] Step 8: High-pressure water is injected into the uranium ore layer through the injection rod column.

[0091] Step 9: Inject CO2 into the uranium ore layer under high pressure through the injection rod column.

[0092] Step 10: High-pressure water injection into the uranium ore layer through the injection rod column.

[0093] Step 11: Repeat the above steps of high-pressure injection of O2, water, CO2 and water until the target water injection volume and target gas injection volume are reached, then close the wellhead for the preset time.

[0094] Step 12: Based on the geological interpretation results of the study area where the uranium ore layer is located, deploy a number of injection wells and production wells for the same ore body where the uranium ore layer is located, and perform the above-mentioned casing installation, cementing, perforation, injection rod injection, and high-pressure injection operations on all injection wells respectively.

[0095] Step 13: After the wellhead is closed for a preset time, open the wellhead of the production well and pump out the uranium-containing leachate through the production well.

[0096] Comparative Example 3

[0097] Step 1: After drilling to the bottom of the uranium ore layer, open-hole logging is performed to determine the location, thickness, and reservoir properties of the uranium ore layer.

[0098] Step 2: After inserting the pressure-bearing anti-corrosion casing into the borehole after drilling, cement slurry is used for well cementing.

[0099] Step 3: After the well washing operation, lower the perforating gun into the borehole to the uranium ore layer, penetrate the casing and cement layer, and then penetrate the uranium ore layer at a predetermined distance to make the casing connected to the uranium ore layer.

[0100] Step 4: Lower the injection rod into the uranium ore layer to complete the preparation work for injection well construction.

[0101] Step 5: Install ground high-pressure liquid injection equipment and high-pressure gas injection equipment; the high-pressure gas injection equipment includes: high-pressure oxygen injection equipment and high-pressure carbon dioxide injection equipment.

[0102] Step 6: Determine the target water injection volume and target gas injection volume for the uranium ore layer based on the thickness of the uranium ore layer, the reservoir physical properties of the uranium ore layer, and the well spacing.

[0103] Step 7: High-pressure water injection into the uranium ore layer through the injection rod column.

[0104] Step 8: Inject O2 into the uranium ore layer under high pressure through the injection rod column.

[0105] Step 9: Inject CO2 into the uranium ore layer under high pressure through the injection rod column.

[0106] Step 10: Repeat the above steps of high-pressure injection of water, O2 and CO2 until the target water injection volume and target gas injection volume are reached, then close the wellhead for a preset time.

[0107] Step 11: Based on the geological interpretation results of the study area where the uranium ore layer is located, deploy a number of injection wells and production wells for the same ore body where the uranium ore layer is located, and perform the above-mentioned casing installation, cementing, perforation, injection rod injection, and high-pressure injection operations on all injection wells respectively.

[0108] Step 12: After the wellhead is closed for a preset time, open the wellhead of the production well and pump out the uranium-containing leachate through the production well.

[0109] Comparative Example 4

[0110] Step 1: After drilling to the bottom of the uranium ore layer, open-hole logging is performed to determine the location, thickness, and reservoir properties of the uranium ore layer.

[0111] Step 2: After inserting the pressure-bearing anti-corrosion casing into the borehole after drilling, cement slurry is used for well cementing.

[0112] Step 3: After the well washing operation, lower the perforating gun into the borehole to the uranium ore layer, penetrate the casing and cement layer, and then penetrate the uranium ore layer at a predetermined distance to make the casing connected to the uranium ore layer.

[0113] Step 4: Lower the injection rod into the uranium ore layer to complete the preparation work for injection well construction.

[0114] Step 5: Install ground high-pressure liquid injection equipment and high-pressure gas injection equipment; the high-pressure gas injection equipment includes: high-pressure oxygen injection equipment and high-pressure carbon dioxide injection equipment.

[0115] Step 6: Determine the target water injection volume and target gas injection volume for the uranium ore layer based on the thickness of the uranium ore layer, the reservoir physical properties of the uranium ore layer, and the well spacing.

[0116] Step 7: High-pressure water injection into the uranium ore layer through the injection rod column.

[0117] Step 8: Inject CO2 into the uranium ore layer under high pressure through the injection rod column.

[0118] Step 9: Inject O2 into the uranium ore layer under high pressure through the injection rod column.

[0119] Step 10: Repeat the above steps of high-pressure injection of water, CO2 and O2 until the target water injection volume and target gas injection volume are reached, then close the wellhead for a preset time.

[0120] Step 11: Based on the geological interpretation results of the study area where the uranium ore layer is located, deploy a number of injection wells and production wells for the same ore body where the uranium ore layer is located, and perform the above-mentioned casing installation, cementing, perforation, injection rod injection, and high-pressure injection operations on all injection wells respectively.

[0121] Step 12: After the wellhead is closed for a preset time, open the wellhead of the production well and pump out the uranium-containing leachate through the production well.

[0122] This invention primarily targets uranium deposits in low-porosity and low-permeability reservoirs. Existing in-situ leaching uranium mining techniques cannot inject CO2 and O2 into these reservoirs, preventing the oxidation of tetravalent uranium minerals into soluble hexavalent uranium. Consequently, these low-porosity and low-permeability uranium deposits cannot be mined using in-situ leaching techniques. The proven reserves of uranium deposits in low-porosity and low-permeability reservoirs are greater than those in conventional reservoirs, resulting in these resources remaining idle.

[0123] Existing in-situ leaching uranium mining technology involves first dissolving CO2 and O2 in water at the surface, and then injecting the CO2- and O2-containing water into the formation. Because the solubility of CO2 and O2 in water is limited, a larger amount of water must be injected to achieve a certain amount of CO2 and O2, resulting in a significant increase in the volume of the injection fluid. Furthermore, since the ore layer already contains a large amount of groundwater, existing in-situ leaching uranium mining technology dilutes the concentration of CO2 and O2 injected into the ore layer, reducing uranium leaching efficiency. This invention employs a high-pressure, direct slug injection method into the uranium ore layer, injecting CO2, water, and O2 directly into the ore layer. This significantly increases the amount of CO2 and O2 injected into the uranium ore layer, thereby increasing the concentration of uranium in the leaching fluid and ultimately improving uranium recovery rate and mining efficiency. Furthermore, changing the order of gas and water injection can easily lead to gas locks in the near-wellbore area. If other gases (CO2) or water are injected under the same pressure, it will also prevent the gas and water from being injected into the low-porosity and low-permeability uranium ore layer, making it impossible to mine the low-porosity and low-permeability uranium ore layer. In such cases, it is often necessary to increase the injection pressure to continue injecting other gases (CO2) or water. Continuing to increase the pressure will exceed the critical fracturing pressure of the uranium ore layer, causing the formation to be fractured and easily inducing safety production accidents.

[0124] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. This disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims. Thus, if these modifications and variations of the invention fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. An in-situ leaching method for uranium mining, characterised in that, include: After drilling to the bottom of the uranium ore layer, open-hole logging is performed to determine the location, thickness, and reservoir properties of the uranium ore layer. After the pressure-bearing anti-corrosion casing is inserted into the borehole after drilling, cement slurry is used for cementing. After the well washing operation is carried out, a perforating gun is lowered into the borehole to the uranium ore layer, and after penetrating the casing and cement layer, it is driven into the uranium ore layer at a predetermined distance so that the casing is connected to the uranium ore layer. The injection rod string is lowered into the uranium ore layer to complete the preparation work for injection well construction; The target water injection volume and target gas injection volume are determined based on the thickness of the uranium ore layer, the reservoir physical properties of the uranium ore layer, and the well spacing. CO2 is injected into the uranium ore layer under high pressure using a slug-type high-pressure injection method via the injection rod; Water is injected into the uranium ore layer under high pressure using a slug-type high-pressure injection method via the injection rod column; O2 is injected into the uranium ore layer under high pressure using a slug-type high-pressure injection method via the injection rod column; Water is injected into the uranium ore layer under high pressure using a slug-type high-pressure injection method via the injection rod column; Repeat the above steps of high-pressure injection of CO2, water, O2 and water to reach the target water injection volume and the target gas injection volume, and then close the wellhead for a preset time. Among them, the injection pressure during slug-type high-pressure water or gas injection is not greater than the critical fracture pressure of the uranium ore layer.

2. The method of claim 1, wherein, Also includes: Based on the geological interpretation results of the study area where the uranium ore layer is located, a number of injection wells and production wells are deployed for the same ore body where the uranium ore layer is located, and the above-mentioned casing installation, cementing, perforation, injection rod injection and high-pressure injection operations are performed on all injection wells respectively. After a preset time has elapsed since the wellhead was closed, the wellhead of the production well is opened, and uranium-containing leachate is pumped out through the production well.

3. The method of claim 2, wherein, After pumping out the uranium-containing leachate through the production well, the process further includes: Repeat the high-pressure injection operation described above for the injection well until the target gas and water injection volumes are reached, then close the wellhead for a preset time. The water injection volume is balanced with the liquid output volume of the production wells within the surrounding area of ​​the injection well.

4. The method of claim 1, wherein, The cementing process using cement slurry includes: filling the space around the casing with cement using a forward grouting method until the cement slurry returns to the surface.

5. The method of claim 1, wherein, After the injection rod column is lowered into the uranium ore layer, the process further includes: Install ground-based high-pressure liquid injection equipment and high-pressure gas injection equipment; The high-pressure gas injection equipment includes: a high-pressure oxygen injection equipment and a high-pressure carbon dioxide injection equipment.

6. The method of claim 1, wherein, The step of determining the target water injection volume and target gas injection volume into the uranium ore layer based on the thickness of the uranium ore layer, the reservoir physical properties of the uranium ore layer, and the well spacing includes: The target water injection volume and target gas injection volume are determined based on the thickness of the uranium ore layer, the porosity included in the reservoir properties of the uranium ore layer, and the well spacing.

7. The method of claim 1, wherein, The preset time is 7 to 10 days.

8. The method of claim 1, wherein, The preset distance is 1 to 2 meters.

9. The method according to any one of claims 1 to 8, characterized in that, The reservoir physical properties include porosity, permeability, and / or pore distribution.

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