Natural gas hydrate freezing sampling device

Abstract

The utility model provides a natural gas hydrate freezing sampling device, which relates to the technical field of freezing coring drilling tools and is arranged in a drill pipe, a drill bit is arranged at the bottom of the drill pipe, and the natural gas hydrate freezing sampling device comprises a salvage spearhead, an elastic clamping mechanism, a single-acting joint and a freezing pressure-maintaining sampling assembly which are sequentially connected from top to bottom; the freezing and pressure-maintaining sampling assembly comprises a pressure-maintaining bin, a cold source storage chamber, a core barrel, a freezing catalyst storage box and a connecting cover pipe, and drilling fluid in the core barrel and the pressure-maintaining bin is frozen at the same time, so that a core sample is in a low-temperature and pressure-maintaining environment, and the core sample can be kept in an original state; after freezing is finished, the whole freezing and pressure-maintaining sampling assembly is lifted up, and after the core barrel is taken out, the core sample is independently stored in a heat-preservation and pressure-maintaining manner. The problem that a traditional freezing sampling drilling tool is not ideal in sampling effect in a high-temperature hole bottom environment is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of freezing coring drill tools, in particular to a natural gas hydrate freezing sampling device. Background Art

[0002] Natural gas hydrates are solid, crystalline substances composed of natural gas and water molecules. They are primarily combustible, containing methane. Their high energy density, wide distribution, and vast reserves make them an important alternative to conventional energy sources. By coring natural gas hydrate cores, we can visually observe and understand the rock types, structure, and tectonic characteristics of the Earth's crust, as well as the oil, gas, and water content, without disrupting the formation. Analysis provides a clear understanding of the distribution, stability, and various physical properties of natural gas hydrates, providing a basis for developing rational development plans and production enhancement measures.

[0003] Since natural gas hydrates can only exist stably under certain temperatures and pressures, thermal insulation and pressure maintenance are required during coring. Currently, there are two main methods for faithful sampling: thermal insulation and pressure maintenance sampling, and the other is bottom hole freezing sampling. Bottom hole freezing sampling is more effective than thermal insulation and pressure maintenance sampling and is widely used. It usually requires the core sample to be frozen for a period of time before being pulled out. However, the bottom hole environment temperature is complex, and the freezing effect and time are difficult to control. Some samples may melt prematurely, and thus traditional freezing sampling drills may not produce ideal sampling results in the higher temperature bottom hole environment. Utility Model Content

[0004] The purpose of the utility model is to provide a natural gas hydrate freezing sampling device, which solves the problem that the traditional freezing sampling drill has unsatisfactory sampling effect in a hole bottom environment with a relatively high temperature.

[0005] The utility model is realized by the following technical solutions: a natural gas hydrate freezing sampling device is arranged in a drill pipe, a drill bit is arranged at the bottom of the drill pipe, and comprises a spear head, a spring-lock mechanism, a single-action joint and a freezing pressure-maintaining sampling assembly connected in sequence from top to bottom;

[0006] The cryopressure sampling assembly includes a pressure-maintaining chamber, a cold source storage chamber, a core tube, a cryocatalyst storage box, and a connecting cover tube. The upper end of the connecting cover tube is connected to the spring-clamp mechanism via the single-action joint, and the lower end of the connecting cover tube is coaxially connected to the cold source storage chamber. Both the single-action joint and the connecting cover tube can vertically enter and exit the pressure-maintaining chamber.

[0007] A mounting tube is coaxially arranged in the cold source storage chamber, the lower end of the mounting tube is sealedly connected to the lower end of the cold source storage chamber, and the upper end of the mounting tube and the upper end of the inner cavity of the cold source storage chamber form an annular overflow port, through which the inner cavity of the mounting tube is communicated with the inner cavity of the cold source storage chamber;

[0008] The freezing catalyst storage box and the core tube are arranged in sequence from top to bottom in the installation tube. The bottom of the freezing catalyst storage box is provided with an insulating piston plate. The insulating piston plate is connected to the freezing catalyst storage box through a plurality of connecting rods. The bottom of the freezing catalyst storage box is provided with a discharge port.

[0009] Furthermore, a plurality of fan-shaped baffles are provided in an annular array at the bottom of the pressure-maintaining chamber, and the baffles are hinged to the pressure-maintaining chamber;

[0010] A connecting seat is rotatably provided on the cold source storage chamber, and the connecting seat is connected to the baffle through a driving spring.

[0011] Furthermore, the lower end of the core tube extends out of the mounting tube and is connected to a retaining ring through a retaining ring, and a retaining ring seat is provided in the drill tube.

[0012] Furthermore, the connecting cover pipe is provided with a catalyst filling port, the catalyst filling port is provided with a first sealing plug, and the catalyst filling port is connected to the frozen catalyst storage tank through a telescopic spiral tube;

[0013] The cold source storage chamber is provided with a cold source filling port, and the cold source filling port is provided with a second sealing plug.

[0014] Furthermore, it includes a movable seat, wherein a movable cavity is radially provided in the movable seat, a push plate is provided in the movable cavity, an upper end of the push plate is connected to the spearhead via a movable tube, and the movable tube is coaxially passed through the spring-clamp mechanism and is threadedly connected to the spring-clamp mechanism;

[0015] A connecting column is provided at the lower end of the push plate, and the connecting column is coaxially connected to the connecting cover pipe through a single-action joint.

[0016] Furthermore, a liquid inlet is provided on the spearhead, the liquid inlet is communicated with the movable tube, a liquid outlet is provided at the lower end of the movable tube, and the liquid outlet is located in the movable cavity.

[0017] Furthermore, a plurality of suspension blocks are provided in a circular array on the movable seat, and a support is provided in the drill pipe, and the support is used to receive the suspension blocks.

[0018] Furthermore, it also includes a centralizer, which is arranged in the drill pipe and is in sliding contact with the pressure-maintaining chamber.

[0019] Furthermore, the spring mechanism includes a lock body and a return spring, a plurality of lock pins are provided in an annular array on the lock body, a plurality of pin seats are provided in an annular array inside the drill pipe, a slot is provided at the bottom of the pin seat, and a movable slot for the lock pin to move up and down is provided between adjacent pin seats; a bevel is provided on the top of the lock pin, and one lock pin is engaged with one of the slots;

[0020] The return spring is sleeved on the movable tube, and the upper and lower ends of the return spring are respectively in contact with the lock body and the movable seat;

[0021] The movable tube is provided with a section of external thread, and the external thread is matched with the thread of the lock body.

[0022] Furthermore, the single-action joint includes a connecting shaft and a thrust bearing, the upper end of the connecting shaft is connected to the connecting column, and the lower end of the connecting shaft passes through the connecting cover tube and is connected to a limiting nut;

[0023] The connecting cover tube is rotatably connected to the connecting shaft, the thrust bearing is sleeved on the connecting shaft, and the upper and lower ends of the thrust bearing are respectively in contact with the connecting column and the connecting cover tube.

[0024] The technical solution of the utility model has at least the following advantages and beneficial effects:

[0025] 1. By freezing the drilling fluid in the core tube and the pressure chamber at the same time, the core sample is kept in a low temperature and pressure environment, which is beneficial for keeping the core sample in its original state. After the freezing is completed, the entire freezing and pressure-maintaining sampling assembly is lifted up, and after removing the core tube, the core sample is stored separately under heat and pressure.

[0026] 2. In the process of lifting the connecting cover tube, the cold source storage chamber is simultaneously driven to move upward. The cold source storage chamber drives several baffles in a vertical state to flip and gather toward the middle through the connecting seat and the driving spring. After flipping to the horizontal state, several fan-shaped baffles seal the lower end of the pressure holding chamber, so that the entire cold source storage chamber, the core tube and the retaining spring are all sealed in the pressure holding chamber, and then the subsequent freezing causes the entire pressure holding chamber to cool down or even freeze and maintain pressure, so that the core sample is kept in its original state to the greatest extent, thereby improving the overall sampling effect. Even if the bottom hole temperature is high, the temperature of the pressure holding chamber needs to be lowered before it affects the core tube. Therefore, it has strong adaptability and can be used in complex bottom layers, with better original preservation effect.

[0027] 3. During drilling and sampling, as the core sample enters the core tube, the upper end of the core sample always contacts the insulating piston plate and pushes the insulating piston plate upward. The insulating piston plate pushes the frozen catalyst storage box upward through several connecting rods until the upper end of the insulating piston plate is aligned with the upper end of the core tube, and drilling is stopped. At this time, the frozen catalyst storage box is placed in the connecting cover pipe, and the space between the discharge port at the bottom of the frozen catalyst storage box and the insulating piston plate is aligned with the overflow port. The frozen catalyst, usually alcohol, enters the annular cold source storage chamber through the overflow port to catalyze the cold source, which is usually dry ice, to achieve freezing of the core sample. Then the drill tube is lifted, and the lower end of the core sample is separated from the solid phase natural gas hydrate in the formation by the cooperation of the retaining spring seat and the retaining spring. Then the connecting cover pipe is lifted to allow the cold source storage chamber to enter the pressure holding chamber, while freezing the drilling fluid in the core tube and the pressure holding chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a schematic diagram of the internal structure of a natural gas hydrate freezing sampling device provided by the utility model;

[0030] Figure 2 This is a schematic structural diagram of a pin seat on a drill pipe in a natural gas hydrate freezing sampling device provided by the present invention;

[0031] Figure 3 This is a schematic diagram of the internal structure of a freezing and pressure-maintaining sampling assembly in a natural gas hydrate freezing sampling device provided by the present invention;

[0032] Figure 4 This is a schematic diagram of the structure of a natural gas hydrate freezing sampling device provided by the utility model after a plurality of baffles seal the lower end of the pressure holding chamber;

[0033] Icons: 1. Drill pipe, 11. Drill bit, 12. Circlip seat, 13. Support, 14. Stabilizer, 2. Spearhead, 21. Liquid inlet, 3. Spring mechanism, 31. Lock body, 32. Return spring, 33. Lock pin, 331. Inclined surface, 34. Pin seat, 341. Slot, 35. Movable slot, 4. Single-action joint, 41. Connecting shaft, 42. Thrust bearing, 43. Limit nut, 5. Pressure chamber, 51. Baffle, 52. Connecting seat, 53. Drive spring, 6. Cold source storage chamber, 61. Connecting Connecting cover pipe, 62, mounting pipe, 63, overflow port, 64, catalyst filling port, 65, first sealing plug, 66, telescopic spiral tube, 67, cold source filling port, 68, second sealing plug, 7, core tube, 71, retaining ring, 72, retaining spring, 8, frozen catalyst storage box, 81, heat-insulating piston plate, 82, connecting rod, 83, discharge port, 9, movable seat, 91, movable cavity, 92, push plate, 93, movable pipe, 931, external thread, 94, connecting column, 95, liquid outlet, 96, hanging block. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0036] Reference Figures 1 to 3 As shown, this embodiment provides a natural gas hydrate freezing sampling device, which is arranged in a drill pipe 1. A drill bit 11 is provided at the bottom of the drill pipe 1, and includes a fishing head 2, a spring-lock mechanism 3, a single-action joint 4 and a freezing pressure-maintaining sampling assembly connected in sequence from top to bottom; after drilling to the target depth, the entire freezing sampling device is lifted or lowered by connecting a fishing device to the fishing head 2.

[0037] The cryopressure sampling assembly includes a pressure-maintaining chamber 5, a cold source storage chamber 6, a core tube 7, a cryocatalyst storage box 8, and a connecting cover tube 61. The upper end of the connecting cover tube 61 is connected to the spring-clamp mechanism 3 via a single-action joint 4, and the lower end of the connecting cover tube 61 is coaxially connected to the cold source storage chamber 6. The single-action joint 4 and the connecting cover tube 61 can vertically enter and exit the pressure-maintaining chamber 5.

[0038] A mounting tube 62 is coaxially provided in the cold source storage chamber 6. The lower end of the mounting tube 62 is sealedly connected to the lower end of the cold source storage chamber 6. An annular overflow port 63 is formed between the upper end of the mounting tube 62 and the inner cavity of the cold source storage chamber 6. The inner cavity of the mounting tube 62 is connected to the inner cavity of the cold source storage chamber 6 through the overflow port 63.

[0039] A freezing catalyst storage box 8 and a core tube 7 are arranged in sequence from top to bottom in the installation tube 62. The lower end of the core tube 7 extends out of the installation tube 62 and is connected to a retaining ring 72 through a retaining ring 71. A retaining ring seat 12 is provided in the drill pipe 1. An insulating piston plate 81 is arranged at intervals at the bottom of the freezing catalyst storage box 8. The insulating piston plate 81 is connected to the freezing catalyst storage box 8 through a number of connecting rods 82. A discharge port 83 is provided at the bottom of the freezing catalyst storage box 8.

[0040] During specific implementation, the drill pipe 1 provides a downward force to the entire cryogenic pressure-maintaining sampling assembly through the spring-clamp mechanism 3 during the downward drilling process. When the core sample enters the core tube 7, it pushes the thermal insulation piston plate 81. The thermal insulation piston plate 81 is initially flush with the lower end of the core tube 7. Therefore, at the initial sampling of the target depth, there is no or almost no gap between the thermal insulation piston plate 81 and the core sample, and no mud exists. At the same time, a plurality of rubber sealing rings are provided between the thermal insulation piston plate 81 and the core tube 7 to prevent the drilling fluid from entering the core tube 7. Then, during drilling sampling, the upper end of the core sample always abuts against the thermal insulation piston plate 81 during the process of the core sample entering the core tube 7, and pushes the thermal insulation piston plate 81 to move upward. The thermal insulation piston plate 81 pushes the cryogenic catalyst storage box 8 upward through a plurality of connecting rods 82 until the upper end of the thermal insulation piston plate 81 is aligned with the upper end of the core tube 7. After that, drilling is stopped. At this time, the frozen catalyst storage box is placed in the connecting cover pipe 61. At the same time, the space between the discharge port 83 at the bottom of the frozen catalyst storage box and the insulating piston plate 81 is aligned with the overflow port 63. The frozen catalyst, usually alcohol, enters the annular cold source storage chamber 6 through the overflow port 63 to catalyze the cold source, which is usually dry ice, to achieve freezing of the core sample. Then, the drill pipe 1 is lifted, and the lower end of the core sample is separated from the solid phase natural gas hydrate in the formation by the cooperation of the retaining spring seat 12 and the retaining spring 72. Then, the connecting cover pipe 61 is lifted, and the cold source storage chamber 6 enters the pressure holding chamber 5. By simultaneously freezing the core tube 7 and the drilling fluid in the pressure holding chamber 5, the core sample is placed in a low temperature and pressure holding environment, which is conducive to keeping the core sample in its original state. After the freezing is completed, the entire freezing and pressure holding sampling assembly is lifted, and after taking out the core tube 7, the core sample is stored separately for heat preservation and pressure holding.

[0041] The bottom annular array of the pressure-maintaining chamber 5 is provided with a plurality of fan-shaped baffles 51, and the baffles 51 are hinged to the pressure-maintaining chamber 5; a connecting seat 52 is rotatably provided on the cold source storage chamber 6, and the connecting seat 52 is connected to the baffle 51 through a driving spring 53. In the specific implementation, in the process of lifting the connecting cover tube 61, the cold source storage chamber 6 is synchronously driven to move upward, and the cold source storage chamber 6 drives the plurality of baffles 51 in a vertical state to flip and gather toward the middle through the connecting seat 52 and the driving spring 53. When the plurality of fan-shaped baffles 51 are flipped to the horizontal After the state is reached, the lower end of the pressure-holding chamber 5 is sealed, so that the entire cold source storage chamber 6, the core tube 7 and the retaining spring 72 are all sealed in the pressure-holding chamber 5. Subsequently, the subsequent freezing causes the entire pressure-holding chamber 5 to cool down or even freeze and maintain pressure, so that the core sample is kept in its original state to the greatest extent, thereby achieving a better overall sampling effect. Even if the bottom hole temperature is high, the temperature of the pressure-holding chamber needs to be lowered before it affects the core tube 7. Therefore, the system has strong adaptability and can be used in complex bottom layers, with a better original preservation effect.

[0042] A catalyst filling port 64 is provided on the connecting cover pipe 61, and a first plug 65 is provided on the catalyst filling port 64. The catalyst filling port 64 is connected to the frozen catalyst storage tank 8 through a telescopic spiral tube 66; the catalyst is added to the frozen catalyst storage tank 8 through the catalyst filling port 64, and since the frozen catalyst storage tank 8 is located in the core tube 7 in the initial state, it needs to be connected through the telescopic spiral tube 66. The telescopic spiral tube 66 can ensure that the frozen catalyst storage tank 8 is always connected to the catalyst filling port 64 during the process of the frozen catalyst storage tank 8 moving up and down, thereby ensuring that the catalyst can be easily added in subsequent practical use. When the catalyst filling port 64 is not in use, it can be sealed by the first plug 65, and the first plug 65 is threadedly matched with the catalyst filling port 64.

[0043] The cold source storage chamber 6 is provided with a cold source filling port 67 , and the cold source filling port 67 is provided with a second sealing plug 68 threadedly matched therewith. The cold source storage chamber 6 can be filled with cold source by opening the second sealing plug 68 .

[0044] The movable seat 9 further includes a movable cavity 91 radially provided in the movable seat 9, a push plate 92 provided in the movable cavity 91, the upper end of the push plate 92 being connected to the spearhead 2 via a movable tube 93, the movable tube 93 coaxially passing through the ejection mechanism 3 and being threadedly connected to the ejection mechanism 3;

[0045] A connecting post 94 is provided at the lower end of the push plate 92, and the connecting post 94 is coaxially connected to the connecting cover tube 61 via the single-action joint 4. The push plate 92 is placed in the movable chamber 91 and can abut against the inner top or inner bottom of the movable chamber 91. When abutting against the inner bottom of the movable chamber 91, it is mainly used to prevent the connecting post 94 below, the single-action joint 4, and the cryopressure sampling assembly from being separated from the pressure chamber 5. At the same time, when the inner tube assembly is finally lifted, that is, after sampling and freezing the core sample, the fixed abutment with the movable chamber 91 drives the entire pressure chamber 5 upward during the lifting process.

[0046] The upper end of the movable tube 93 is penetrated by an ejection and locking mechanism 3. The spearhead 2 is provided with a liquid inlet 21, which is connected to the movable tube 93. The lower end of the movable tube 93 is provided with a liquid outlet 95, which is located in the movable chamber 91. Drilling fluid enters through the liquid inlet 21, then passes through the movable tube 93 and is discharged from the lower liquid outlet 95. From the movable chamber 91, it enters between the drill pipe 1 and the pressure-maintaining chamber 5, and is ultimately transported downward to the drill bit 11 and out, then passes through the ejection and locking mechanism 3 through the movable tube 93.

[0047] A plurality of suspension blocks 96 are arranged in a circular array on the movable seat 9, and a support 13 is provided within the drill pipe 1 to receive the suspension blocks 96. In practice, the suspension blocks 96 are placed on the support 13 to support the spring-loaded mechanism 3 and the entire cryopressure sampling assembly located below, maintaining a fixed distance from the drill bit 11 at the lower end of the drill pipe 1.

[0048] More specifically, it also includes a stabilizer 14, which is arranged in the drill pipe 1. The stabilizer 14 is in sliding contact with the pressure holding chamber 5. The stabilizer 14 makes the pressure holding chamber 5 coaxial with the drill pipe 1, and then makes the core tube 7 coaxial with the drill pipe 1, thereby ensuring that the core sample enters the core tube 7 smoothly.

[0049] The spring mechanism 3 includes a lock body 31 and a return spring 32. A plurality of lock pins 33 are arranged in a circular array on the lock body 31. A plurality of pin seats 34 are arranged in a circular array inside the drill pipe 1. Slots 341 are provided at the bottom of the pin seats 34. A movable slot 35 for the lock pins 33 to move up and down is provided between adjacent pin seats 34. The top of the lock pins 33 is provided with an inclined surface 331, and each lock pin 33 engages with a slot 341.

[0050] The return spring 32 is sleeved on the movable tube 93 , and the upper and lower ends of the return spring 32 are respectively in contact with the lock body 31 and the movable seat 9 .

[0051] When the cam 33 is in the closed position, the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, so that the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, so that the cam 33 is in the closed position, and the cam 33 is in the closed position, so that the cam 33 is in the closed position, so that the cam 33 is in the closed position, 3 is placed in the movable groove 35, and then the spearhead 2 is continued to be controlled to rotate. The movable tube 93 is provided with a section of external thread 931, and the external thread 931 is threadedly matched with the lock body 31. By controlling the rotation of the spearhead 2, the external thread 931 is separated from the lock body 31. Then the movable tube 93 and the lock body 31 maintain a sliding connection relationship, the upper body spearhead 2 is lifted, and then the cold source storage chamber 6 is driven to move up into the pressure holding chamber 5 through the movable tube 93, the push plate 92, the connecting column 94, the single-action joint 4 and the connecting cover pipe 61. At the same time, after the cold source storage chamber 6 enters the pressure holding chamber 5, the baffles 51 block the pressure holding chamber 5. After freezing for a period of time, the upper body spearhead 2 is continued to be lifted, and the push plate 92 is abutted against the inner top of the movable seat 9, thereby driving the spring-cage mechanism 3 and the pressure holding chamber 5 located on the upper and lower sides of the movable seat 9 to move up, and then the entire inner tube assembly moves up, completing the sampling of the core sample.

[0052] The single-action joint 4 includes a connecting shaft 41 and a thrust bearing 42. The upper end of the connecting shaft 41 is connected to the connecting column 94, and the lower end of the connecting shaft 41 passes through the inner top of the connecting cover tube 61 and is connected to the limit nut 43. The connecting cover tube 61 is rotatably connected to the connecting shaft 41, and the thrust bearing 42 is sleeved on the connecting shaft 41. The upper and lower ends of the thrust bearing 42 respectively abut against the connecting column 94 and the connecting cover tube 61. The single-action joint 4 is mainly used to prevent the portion below the connecting cover tube 61 below the single-action joint 4 from rotating with the drill pipe 1 during drilling. The core barrel 7 is mainly prevented from rotating with the drill pipe 1, thereby maintaining the original state of the core sample to the greatest extent possible. At the same time, it can also control the rotation of the spearhead 2 without causing the connecting cover tube 61 and the portion below to rotate.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A natural gas hydrate freezing sampling device, arranged in a drill pipe (1), wherein a drill bit (11) is arranged at the bottom of the drill pipe (1), characterized in that: It comprises a spear head (2), a spring-clamp mechanism (3), a single-action joint (4) and a freezing pressure-maintaining sampling assembly which are sequentially connected from top to bottom; The cryopressure sampling assembly comprises a pressure-maintaining chamber (5), a cold source storage chamber (6), a core tube (7), a cryocatalyst storage box (8) and a connecting hood tube (61); the upper end of the connecting hood tube (61) is connected to the spring-clamp mechanism (3) via the single-action joint (4), and the lower end of the connecting hood tube (61) is coaxially connected to the cold source storage chamber (6); the single-action joint (4) and the connecting hood tube (61) can both vertically enter and exit the pressure-maintaining chamber (5); A mounting tube (62) is coaxially arranged in the cold source storage chamber (6), the lower end of the mounting tube (62) is sealedly connected to the lower end of the cold source storage chamber (6), and an annular overflow port (63) is formed between the upper end of the mounting tube (62) and the upper end of the inner cavity of the cold source storage chamber (6), and the inner cavity of the mounting tube (62) is communicated with the inner cavity of the cold source storage chamber (6) through the overflow port (63); The freezing catalyst storage box (8) and the core tube (7) are arranged in sequence from top to bottom in the installation tube (62); an insulating piston plate (81) is arranged at intervals at the bottom of the freezing catalyst storage box (8); the insulating piston plate (81) is connected to the freezing catalyst storage box (8) through a plurality of connecting rods (82); and a discharge port (83) is provided at the bottom of the freezing catalyst storage box (8).

2. A natural gas hydrate freezing sampling device according to claim 1, characterized in that: A plurality of fan-shaped baffles (51) are provided in an annular array at the bottom of the pressure-maintaining chamber (5), and the baffles (51) are hinged to the pressure-maintaining chamber (5); A connecting seat (52) is rotatably provided on the cold source storage chamber (6), and the connecting seat (52) is connected to the baffle (51) via a driving spring (53).

3. A natural gas hydrate freezing sampling device according to any one of claims 1-2, characterized in that: The lower end of the core tube (7) extends out of the mounting tube (62) and is connected to a retaining ring (72) via a retaining ring (71), and a retaining ring seat (12) is provided in the drill tube (1).

4. A natural gas hydrate freezing sampling device according to claim 3, characterized in that: The connecting cover pipe (61) is provided with a catalyst filling port (64), the catalyst filling port (64) is provided with a first sealing plug (65), and the catalyst filling port (64) is connected to the frozen catalyst storage box (8) through a telescopic spiral tube (66); The cold source storage chamber (6) is provided with a cold source filling port (67), and the cold source filling port (67) is provided with a second sealing plug (68).

5. The natural gas hydrate freezing sampling device according to claim 4, characterized in that: It also includes a movable seat (9), wherein a movable cavity (91) is radially provided in the movable seat (9), a push plate (92) is provided in the movable cavity (91), the upper end of the push plate (92) is connected to the spearhead (2) through a movable tube (93), and the movable tube (93) is coaxially provided to pass through the spring-cage mechanism (3) and is threadedly connected to the spring-cage mechanism (3); A connecting column (94) is provided at the lower end of the push plate (92), and the connecting column (94) is coaxially connected to the connecting cover pipe (61) through a single-action joint (4).

6. A natural gas hydrate freezing sampling device according to claim 5, characterized in that: The spearhead (2) is provided with a liquid inlet (21), which is communicated with the movable tube (93). The lower end of the movable tube (93) is provided with a liquid outlet (95), which is located in the movable cavity (91).

7. The natural gas hydrate freezing sampling device according to claim 6, characterized in that: A plurality of suspension blocks (96) are arranged in a circular array on the movable seat (9), and a support (13) is arranged in the drill pipe (1), and the support (13) is used to receive the suspension blocks (96).

8. The natural gas hydrate freezing sampling device according to claim 7, characterized in that: It also includes a centralizer (14), which is arranged in the drill pipe (1) and is in sliding contact with the pressure-maintaining chamber (5).

9. The natural gas hydrate freezing sampling device according to claim 8, characterized in that: The spring-lock mechanism (3) comprises a lock body (31) and a return spring (32); a plurality of lock pins (33) are provided in an annular array on the lock body (31); a plurality of pin seats (34) are provided in an annular array inside the drill pipe (1); a slot (341) is provided at the bottom of the pin seat (34); and a movable slot (35) for the lock pin (33) to move up and down is provided between adjacent pin seats (34); a slope (331) is provided at the top of the lock pin (33); and one lock pin (33) is engaged with one slot (341); The return spring (32) is sleeved on the movable tube (93), and the upper and lower ends of the return spring (32) are respectively in contact with the lock body (31) and the movable seat (9); The movable tube (93) is provided with an external thread (931), and the external thread (931) is threadably matched with the lock body (31).

10. The natural gas hydrate freezing sampling device according to claim 6, characterized in that: The single-action joint (4) comprises a connecting shaft (41) and a thrust bearing (42); the upper end of the connecting shaft (41) is connected to the connecting column (94); the lower end of the connecting shaft (41) passes through the connecting cover tube (61) and is connected to a limiting nut (43); The connecting cover tube (61) is rotatably connected to the connecting shaft (41), the thrust bearing (42) is sleeved on the connecting shaft (41), and the upper and lower ends of the thrust bearing (42) are respectively in contact with the connecting column (94) and the connecting cover tube (61).

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