Gravel throwing device and gravel throwing method

Abstract

The invention relates to the technical field of in-situ leaching uranium mining, in particular to a gravel throwing device and a gravel throwing method. The gravel throwing device comprises a connector piece; the outer cylinder assembly is connected with the connector piece, the connector piece and the outer cylinder assembly form a communicated cavity, and a first gravel throwing opening is formed in the outer cylinder; the plugging body is connected with the outer cylinder in a sliding manner; the insertion tube assembly is located in the cavity, the insertion tube assembly can move in the axial direction of the outer cylinder assembly, the insertion tube assembly comprises an insertion tube body and a pawl spring mechanism, a second gravel throwing opening is formed in the insertion tube body, the pawl spring mechanism is matched with the plugging body, and the insertion tube assembly is located in the cavity and can move in the axial direction of the outer cylinder assembly. The pawl spring mechanism is arranged on the blocking body so that the first gravel throwing opening and the second gravel throwing opening can be communicated or closed, and the elastic modulus of the pawl spring mechanism is larger than that of the blocking body. The gravel throwing device solves the problem that closing is not tight due to sand clamping or failure of an elastic body.

Description

Technical Field

[0001] This application relates to the field of in-situ leaching uranium mining technology, and in particular to a gravel-feeding device and a gravel-feeding method. Background Technology

[0002] In in-situ leaching uranium mining, constructing high-quality, stable production wells is a crucial step. Production wells are vital working channels connecting the surface with the ore-bearing aquifer, typically consisting of casing, filters, and settling pipes from top to bottom. To improve the precision and efficiency of in-situ leaching uranium mining, secondary well-forming drilling technology has been widely researched and applied in the field. One core aspect of secondary well-forming technology is that after casing windowing in the target ore layer, an internal filter assembly (usually including a packer, filter, gravel-feeding valve, and settling pipe) is installed. Then, reverse gravel-feeding is performed, filling the annulus between the filter and the borehole wall with gravel to form a stable artificial filter layer. The core equipment for gravel-feeding is the gravel-feeding valve device. Current gravel-feeding devices mostly employ a piston and spring structure; the opening of the gravel-feeding channel is achieved by external pressure, while the closing is achieved by the rebound force of an elastic element. However, in practical applications, when encountering loose strata containing gravelly sandstone or medium-coarse sandstone, the sand grains and gravels in the strata can easily jam the piston, causing the elastic element to be unable to drive the piston to reset, thus preventing the gravel feeding channel from being completely closed.

[0003] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of protection of this application. Summary of the Invention

[0004] This application provides a gravel-throwing device and a gravel-throwing method to solve or alleviate one or more of the technical problems mentioned above.

[0005] A first aspect of this application provides a gravel-throwing device, comprising: a connector; an outer cylinder assembly connected to the connector, the connector and the outer cylinder assembly forming a communicating cavity, the outer cylinder having a first gravel-throwing port; a sealing body slidably connected to the outer cylinder; and a cannula assembly located within the cavity, the cannula assembly being movable along the axial direction of the outer cylinder assembly, the cannula assembly including a cannula body and a claw spring mechanism, the cannula body having a second gravel-throwing port, the claw spring mechanism cooperating with the sealing body to connect or close the first gravel-throwing port and the second gravel-throwing port, wherein the elastic modulus of the claw spring mechanism is greater than the elastic modulus of the sealing body.

[0006] The gravel-feeding device of this application embodiment, through the mechanical linkage between the claw spring mechanism and the sealing body, can forcibly drive the sealing body to close or open the gravel-feeding channel formed by the connection of the first and second gravel-feeding ports during the gravel-feeding process, fundamentally solving the problem of incomplete closure caused by sand jamming or failure of the elastomer. The elastic modulus of the claw spring mechanism is greater than that of the sealing body, so the rigid claw spring mechanism can engage with the soft sealing body, reducing the occurrence of phenomena such as disengagement.

[0007] According to an embodiment of this application, the claw spring mechanism includes a plurality of elastic claws distributed circumferentially, wherein the elastic claws retract toward their axis in their natural state and open when subjected to a radially outward force.

[0008] According to an embodiment of this application, the sealing body is provided with a first mating part and a second mating part. When the insertion tube assembly moves in the axial movement of the cylinder from the direction of the connector to the cylinder, the insertion tube body abuts against the first mating part to make the first gravel inlet and the second gravel inlet connected; or, when the insertion tube assembly moves in the axial movement of the cylinder from the direction of the cylinder to the connector, the claw spring mechanism abuts against the second mating part to drive the sealing body to slide and block the first gravel inlet.

[0009] According to an embodiment of this application, the first mating part is a step disposed on the sealing body; the second mating part is a hook platform disposed on the sealing body, and the hook platform cooperates with the claw spring mechanism.

[0010] According to an embodiment of this application, the gravel-feeding device further includes an elastomer located within the cavity. The elastomer is used to provide a restoring force to the sealing body, so that the sealing body seals the first gravel-feeding port.

[0011] According to an embodiment of this application, the gravel-feeding device further includes a first sealing ring, which is located between the outer cylinder and the sealing body.

[0012] According to an embodiment of this application, a second sealing ring is provided between the cannula body and the connector.

[0013] According to an embodiment of this application, the occlusion body includes a piston; the insertion assembly is made of a metallic material.

[0014] A second aspect of this application provides a gravel-throwing method, performed using the gravel-throwing device described in the first aspect, the gravel-throwing method comprising the following steps: S1: Insert the built-in filter assembly with the outer cylinder assembly into the designed position inside the drill casing; S2: Lower the cannula assembly into the sleeve and insert it into the outer cylinder assembly; S3: Move the cannula assembly to slide the blocking body and open the first gravel inlet to form a gravel inlet channel formed by the first gravel inlet and the second gravel inlet; S4: Gravel is fed into the well, and the gravel enters the target annulus through the gravel feeding channel; S5: After the gravel is thrown, move the insertion tube assembly upward so that the claw spring mechanism hooks the sealing body and drives the sealing body to slide until the sealing body blocks the first gravel throwing port; S6: Continue to move the cannula assembly upwards to disengage the claw spring mechanism from the sealing body and remove the cannula assembly.

[0015] The method described in this application embodiment can achieve reliable forced closure and visualized control of the operation process. Specifically, the first gravel inlet is closed by forcibly pulling the sealing body back to the first gravel inlet through a claw spring mechanism; the process of opening the first gravel inlet to form a gravel inlet channel is achieved by the insertion tube body pushing the piston to slide, which is reliable; the push-open type opening, external discharge type gravel inlet, and scraping type closing design work together to form a complete sand prevention and anti-attachment system, ensuring the reliable operation of the gravel inlet device in sandy strata; the reliable closure of the first gravel inlet effectively prevents gravel backflow and filter layer damage, avoids the risk of borehole collapse, and ensures the long-term stable operation and production efficiency of the borehole.

[0016] According to an embodiment of this application, in step S5, the reading of the ground tension gauge is used to determine whether the piston blocks the gravel-throwing channel; In step S6, the reading of the ground tension gauge is used to determine whether the claw spring mechanism has disengaged from the piston. Attached Figure Description

[0017] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0018] Figure 1 These are schematic diagrams of the gravel-feeding device in some embodiments; Figure 2 These are partial structural schematic diagrams of the gravel-feeding device in some embodiments.

[0019] Explanation of reference numerals in the attached figures: 1: Insertion tube assembly; 11: Insertion tube body; 12: Claw spring mechanism; 120: Elastic claw; 13: Second gravel inlet; 2: Connector; 3: Outer cylinder assembly; 31: First gravel inlet; 4: Elastomer; 5: Sealing body; 51: First mating part; 52: Second mating part; 6: First sealing ring; 7: Second sealing ring. Detailed Implementation

[0020] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, and elements, as well as their relative dimensions, may be exaggerated. Throughout, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0021] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this application, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this application.

[0022] In this application, unless otherwise expressly specified and limited, the terms "connected," "linked," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] In practical applications, when encountering loose formations containing gravelly sandstone or medium-coarse sandstone, the sand and gravel in the formation can easily clog the piston, preventing the elastic element from driving the piston to reset and thus preventing the gravel-feeding channel from closing completely. This failure can lead to serious consequences: firstly, the unclosed gravel-feeding channel can cause gravel and formation mud to backflow into the casing, causing blockage and damage to the downhole tool string; secondly, it can damage the pre-formed gravel filter layer, potentially leading to borehole collapse, affecting well completion quality, and ultimately causing the entire borehole to be scrapped, resulting in huge economic losses. Therefore, there is an urgent need for a new gravel-feeding device structure and method that can fundamentally solve the sand-clogging problem and ensure that the gravel-feeding channel can be reliably closed under any operating conditions.

[0025] Accordingly, a first aspect of the embodiments of this application provides a gravel-feeding device. (See reference...) Figure 1 The gravel-throwing device includes a connector 2; an outer cylinder assembly 3 connected to the connector 2, forming a communicating cavity with the connector 2 and the outer cylinder assembly 3, with a first gravel-throwing port 31 on the outer cylinder; a sealing body 5 slidably connected to the outer cylinder assembly 3; and an insertion tube assembly 1 located within the cavity, movable along the axial direction of the outer cylinder assembly. The insertion tube assembly includes an insertion tube body 11 and a claw spring mechanism 12, with a second gravel-throwing port 13 on the insertion tube body 11. The claw spring mechanism 12 cooperates with the sealing body 5 to allow communication or closure between the first gravel-throwing port 31 and the second gravel-throwing port 13, wherein the elastic modulus of the claw spring mechanism 12 is greater than the elastic modulus of the sealing body 5.

[0026] The gravel-feeding device of this application embodiment, through the mechanical linkage between the claw spring mechanism and the sealing body, can forcibly drive the sealing body to close or open the gravel-feeding channel formed by the connection of the first and second gravel-feeding ports during the gravel-feeding process, fundamentally solving the problem of incomplete closure caused by sand jamming or failure of the elastomer. The elastic modulus of the claw spring mechanism is greater than that of the sealing body, so the rigid claw spring mechanism can engage with the soft sealing body, reducing the occurrence of phenomena such as disengagement.

[0027] Understandably, reference Figure 2 You can see the gravel feeding channel formed by the connection of the first and second gravel feeding ports.

[0028] Furthermore, there are two first gravel inlets, and these two first gravel inlets are symmetrically arranged so that gravel enters from the first gravel inlet, passes through the second gravel inlet, and then exits through the first gravel inlet to complete the gravel feeding.

[0029] Accordingly, there are at least two sealing bodies to block the two first gravel inlets respectively.

[0030] In some other specific embodiments, the sealing body is a single entity, and the sealing body is cylindrical in shape, with a first gravel inlet and a second gravel inlet provided on opposite sides of the cylindrical sealing body.

[0031] In some embodiments, the claw spring mechanism 12 includes a plurality of elastic claws 120 distributed circumferentially. The elastic claws retract towards their axis in their natural state and open when subjected to a radially outward force. The retracted elastic claws facilitate lowering and passage; when compressed, they open, causing the sealing body to slide and close the first gravel inlet; simultaneously, based on the difference in elastic modulus between the sealing body and the claw spring mechanism, the sealing body can be separated simply by overloading the claw spring mechanism.

[0032] Furthermore, the number of claw spring mechanisms is equal to the number of first gravel feeding ports. Optionally, there are two first gravel feeding ports, and two elastic claws, which are symmetrically arranged. Each elastic claw corresponds to a sealing body on each first gravel feeding port. When it is necessary to close the first gravel feeding port with the sealing body, the claw springs are used to hook the sealing body and seal the first gravel feeding port under overload, and then the connection is released.

[0033] Furthermore, the claw spring mechanism consists of one claw spring mechanism with two elastic claws symmetrically distributed along its axial direction. These two elastic claws are used to block the first and second gravel feeding ports, respectively.

[0034] In some embodiments, reference Figure 2The sealing body 5 is provided with a first mating part 51 and a second mating part 52. When the insertion tube assembly moves from the joint member toward the cylinder in the axial movement of the cylinder, the insertion tube body abuts against the first mating part to make the first gravel inlet and the second gravel inlet connected; or, when the insertion tube assembly moves from the cylinder to the joint member in the axial movement of the cylinder, the claw spring mechanism is in low contact with the second mating part to drive the sealing body to slide and read the first gravel inlet.

[0035] Furthermore, the first mating part is a step provided on the sealing body. This step can serve as an abutment surface. Under the action of overload, the insertion tube body will drive the sealing body away from the first gravel inlet through this abutment surface, so that the first gravel inlet and the second gravel inlet are connected to form a gravel inlet channel.

[0036] Furthermore, the second mating part is a hook platform disposed on the sealing body, which engages with the claw spring mechanism. In this way, the claw spring mechanism can securely hook the hook platform, and under overload conditions, it can reset the piston to block the first gravel inlet.

[0037] In some embodiments, the gravel-feeding device further includes an elastomer 4 located within the cavity, the elastomer being used to provide a restoring force for the sealing, so that the sealing body seals the first gravel-feeding port.

[0038] Furthermore, the elastomer is made of a soluble material. This facilitates the sedimentation process after the cannula is removed.

[0039] In some embodiments, the gravel-feeding device further includes a first sealing ring 6, which is located between the outer cylinder and the sealing body. This ensures a tight seal between the outer cylinder and the sealing body when the sealing body closes the first gravel-feeding port. Even if the soluble elastic element fails, the piston can still be stably maintained in the closed position thanks to the mechanical structure, guaranteeing long-term reliability.

[0040] In some embodiments, a second sealing ring 7 is provided between the cannula body and the connector. This ensures a tight seal between the cannula body and the connector.

[0041] In some embodiments, the occlusion body includes a piston, and the cannulation assembly is made of a non-metallic material. Optionally, the cannulation assembly is made of a metallic material that is corrosion-resistant and has a certain weight. Optionally, the metallic material is stainless steel.

[0042] A second aspect of this application provides a gravel-throwing method. The method employs the gravel-throwing device described in the first aspect, and includes the following steps: S1: Insert the built-in filter assembly with the outer cylinder assembly into the designed position inside the drill casing; S2: Lower the cannula assembly into the sleeve and insert it into the outer cylinder assembly; S3: Move the cannula assembly to slide the blocking body and open the first gravel inlet to form a gravel inlet channel formed by the first gravel inlet and the second gravel inlet; S4: Gravel is fed into the well, and the gravel enters the target annulus through the gravel feeding channel; S5: After the gravel is thrown, move the insertion tube assembly upward so that the claw spring mechanism hooks the sealing body and drives the sealing body to slide until the sealing body blocks the first gravel throwing port; S6: Continue to move the cannula assembly upwards to disengage the claw spring mechanism from the sealing body and remove the cannula assembly.

[0043] The method described in this application embodiment can achieve reliable forced closure and visualized control of the operation process. Specifically, the first gravel inlet is closed by forcibly pulling the sealing body back to the first gravel inlet through a claw spring mechanism; the process of opening the first gravel inlet to form a gravel inlet channel is achieved by the insertion tube body pushing the piston to slide, which is reliable; the push-open type opening, external discharge type gravel inlet, and scraping type closing design work together to form a complete sand prevention and anti-attachment system, ensuring the reliable operation of the gravel inlet device in sandy strata; the reliable closure of the first gravel inlet effectively prevents gravel backflow and filter layer damage, avoids the risk of borehole collapse, and ensures the long-term stable operation and production efficiency of the borehole.

[0044] Furthermore, in step S5, the reading of the surface tension gauge is used to determine whether the piston is blocking the gravel-feeding channel. When the claw spring hooks the sealing body and forces it to slide, the surface tension gauge reading will increase significantly. This clearly indicates that the first gravel-feeding port is closing and the sealing body is resetting. This feedback from the surface tension gauge reading eliminates the uncertainty of the downhole status.

[0045] Furthermore, in step S6, the reading of the ground tension gauge is used to determine whether the claw spring mechanism has disengaged from the sealing body. When the sealing body completely closes the first gravel inlet and the claw spring disengages from the sealing body, the reading of the ground tension gauge will suddenly drop, accompanied by vibration of the outer cylinder. This clearly indicates that the claw spring has successfully disengaged from the piston, and the insertion assembly can be safely pulled out. This dual physical feedback mechanism significantly reduces the risk of misoperation and avoids downhole accidents caused by premature or delayed pipe pulling.

[0046] As a specific example, the gravel-throwing method includes the following steps: S10: Connect the sedimentation pipe, the gravel feeding device, the built-in filter and the packer from bottom to top to form a built-in filter assembly, and then lower the built-in filter assembly to the design position through the drill rod; S20: After the packer is pressurized and set, the drill pipe and setting tool are removed; S30: Connect the claw spring type insertion tube to the gravel-throwing drill pipe, and then lower it into the casing. When the insertion tube is about 50cm above the gravel-throwing device, connect the gravel-throwing drill pipe to the surface mud pump, turn on the mud pump and circulate clean water for 15 minutes to clean the bottom of the well.

[0047] S40: In pumping mode, slowly lower the gravel-feeding drill rod, applying a downward pressure of no less than 500 kg to the claw-spring type insert. The insert body abuts against the first mating part of the piston, pushing the piston and opening the first gravel-feeding port to form a gravel-feeding channel. When the tension gauge reading decreases, it indicates that the piston has been pushed open and the gravel-feeding channel has been opened. Gravel enters the target annulus through the inside of the insert, through the gravel-feeding groove at its lower end, and through the opened gravel-feeding channel.

[0048] S50: Pump the gravel and water into the gravel-feeding drill pipe to begin continuous gravel feeding, avoiding prolonged pump stoppages. The gravel enters the feeding space (target annulus) through the gravel-feeding channel, and the water is returned to the wellhead via the built-in filter; S60: After gravel loading is complete, slowly lift the gravel-loading drill pipe. Initially, the claw spring mechanism hooks onto the piston and forcibly moves it, closing the first gravel loading port. The tension gauge reading will initially increase significantly (approximately 5000N). This design ensures that even if sand particles become stuck, the piston can be mechanically pulled back to the closed position. Continuing to lift, the claw spring mechanism disengages from the piston, the tension gauge reading drops sharply, and the gravel-loading drill pipe vibrates. At this point, the claw spring mechanism is completely disengaged from the piston, allowing the claw spring-loaded tubing to be pulled out of the wellhead independently, while the piston remains reliably in the closed position.

[0049] It should be noted that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., are used only for the convenience of describing this application 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 on this application. The directional terms "inner" and "outer" refer to the inside or outside relative to the outline of the component itself. For example, if a device in the drawings is inverted, a device described as "above" or "on top of" other devices or structures will subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0050] It should also be noted that the terms "some embodiments," "other embodiments," and "embodiments" used in this application refer to specific features, structures, or characteristics described in connection with those embodiments, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0051] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0052] It should also be noted that the above are merely preferred embodiments of this application and do not limit the scope of protection of this application. Any equivalent structural or procedural transformations made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of protection of this application.

Claims

1. A gravel-feeding device, characterized in that, include: Connector; An outer cylinder assembly is connected to the connector, and the connector and the outer cylinder assembly form a communicating cavity. A first gravel inlet is provided on the outer cylinder. A sealing body, wherein the sealing body is slidably connected to the outer cylinder; An insertion assembly is located within the cavity and is axially movable along the outer cylinder assembly. The insertion assembly includes an insertion body and a claw spring mechanism. The insertion body is provided with a second gravel inlet. The claw spring mechanism cooperates with the sealing body to connect or close the first gravel inlet and the second gravel inlet. The elastic modulus of the claw spring mechanism is greater than that of the sealing body.

2. The gravel-feeding device according to claim 1, characterized in that, The claw spring mechanism includes multiple elastic claws distributed circumferentially. The elastic claw retracts towards its axis in its natural state. And it opens when subjected to a radially outward force.

3. The gravel-feeding device according to claim 1 or 2, characterized in that, The sealing body is provided with a first mating part and a second mating part. When the insertion assembly moves from the connector in the direction of the cylinder during the axial movement of the cylinder, the insertion body abuts against the first mating part to make the first gravel inlet and the second gravel inlet connected. Alternatively, when the insertion assembly moves from the cylinder towards the connector during the axial movement of the cylinder, the claw spring mechanism abuts against the second mating part to drive the sealing body to slide and block the first gravel inlet.

4. The gravel-feeding device according to claim 3, characterized in that, The first mating part is a step provided on the sealing body; The second mating part is a hook platform disposed on the sealing body, and the hook platform mates with the claw spring mechanism.

5. The gravel-feeding device according to claim 1, characterized in that, It also includes an elastomer, which is located within the cavity. The elastomer is used to provide a restoring force to the sealing body so that the sealing body seals the first gravel inlet.

6. The gravel-feeding device according to claim 1, characterized in that, Also includes: First sealing ring, The first sealing ring is located between the outer cylinder and the sealing body.

7. The gravel-feeding device according to claim 1, characterized in that, A second sealing ring is provided between the cannula body and the connector.

8. The gravel-feeding device according to claim 1, characterized in that, The sealing body includes a piston; The cannulation assembly is made of metal.

9. A method for gravel feeding, characterized in that, The gravel-throwing method, performed using the gravel-throwing device according to any one of claims 1-8, comprises the following steps: S1: Insert the built-in filter assembly with the outer cylinder assembly into the designed position inside the drill casing; S2: Lower the cannula assembly into the sleeve and insert it into the outer cylinder assembly; S3: Move the cannula assembly to slide the blocking body and open the first gravel inlet to form a gravel inlet channel formed by the first gravel inlet and the second gravel inlet; S4: Gravel is fed into the well, and the gravel enters the target annulus through the gravel feeding channel; S5: After the gravel is thrown, move the insertion tube assembly upward so that the claw spring mechanism hooks the sealing body and drives the sealing body to slide until the sealing body blocks the first gravel throwing port; S6: Continue to move the cannula assembly upwards to disengage the claw spring mechanism from the sealing body and remove the cannula assembly.

10. The gravel-throwing method according to claim 9, characterized in that, In step S5, the reading of the ground tension gauge is used to determine whether the piston blocks the gravel-throwing channel; In step S6, the reading of the ground tension gauge is used to determine whether the claw spring mechanism has disengaged from the piston.

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