Natural gas hydrate freezing sampling device and method

Abstract

The invention provides a natural gas hydrate freezing sampling device which is arranged in a drill pipe with the bottom connected with a drill bit and comprises an inner pipe, a cold source chamber upper connector, a cold source chamber lower connector and a sealing plate are sequentially arranged in the inner pipe from top to bottom at intervals, and a cold source storage chamber is formed between the cold source chamber upper connector and the cold source chamber lower connector. A freezing chamber is arranged between the cold source chamber lower connector and the sealing plate, and a freezing pressure maintaining chamber is formed between the sealing plate and the clamping spring seat. A core barrel is coaxially arranged in the freezing chamber, a first through hole is formed in the lower connector of the cold source chamber, a second through hole is formed in the sealing plate, and the valve rod penetrates through the upper connector of the cold source chamber, the first through hole and the second through hole in a sliding mode. A first piston and a second piston which are respectively embedded with the first through hole and the second through hole are arranged on the valve rod at intervals; the problems that at present, only the side wall of a core barrel is frozen, the lower end of the core barrel is not frozen, and the freezing effect and the pressure maintaining effect are poor are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of freezing sampling, and in particular to a natural gas hydrate freezing sampling device and method. Background Art

[0002] Natural gas hydrate is a solid crystalline substance composed of natural gas and water molecules. It is a combustible substance mainly composed of methane. Natural gas hydrate has the characteristics of high energy density, wide distribution, and huge reserves, so it has become an important successor to conventional energy. In addition, natural gas hydrate does not produce pollutants after combustion, which can effectively protect the environment. Therefore, the large-scale development of natural gas hydrate resources can help promote the transformation of energy consumption structure.

[0003] Natural gas hydrates are mainly distributed in seafloor sediments at the edge of the ocean and in the permafrost layer of the high-altitude permafrost on land. Drilling sampling is the most direct way to identify natural gas hydrates and is also a necessary means to verify the results of other survey methods. By coring, we can intuitively observe and understand the rock type, structure, and structural characteristics of the crust without destroying the overall formation, as well as detect its oil, gas, and water production characteristics. Through laboratory testing and analysis, we can clearly know the distribution, stability, and various physical properties of natural gas hydrates, which provides a basis for formulating reasonable development plans and production increase measures.

[0004] Since natural gas hydrates can only exist stably under certain temperature and pressure, it is necessary to carry out heat preservation and pressure preservation treatment during coring. At present, there are two main methods for fidelity sampling, one is heat preservation and pressure preservation sampling, and the other is bottom hole freezing sampling. Heat preservation and pressure preservation sampling mainly uses ball valves and flap valves to maintain the pressure of the core tube, and uses insulation materials for passive insulation. Due to its complex mechanical structure, the sealing is not guaranteed and the heat conduction during drilling is high, so the failure rate of coring is high. Bottom hole freezing sampling is a method of inhibiting the decomposition of natural gas hydrates by low temperature. After drilling, the cooling catalyst is injected into the freezing chamber through the cold source control device. When the cold source contacts the cooling catalyst, it will absorb a lot of heat and reduce the temperature of the core tube to a low temperature zone, ensuring that the natural gas hydrate will not decompose during the lifting process. This method has a high success rate of coring and ensures that the material will not change. However, at present, most of the freezing coring is to freeze the side wall of the core tube, while the lower end of the core tube is not frozen. There are problems such as poor freezing effect and pressure preservation effect, which leads to inaccurate subsequent test results. Summary of the invention

[0005] The purpose of the present invention is to provide a natural gas hydrate freezing sampling device and method, which solves the problem that the current freezing coring mostly only freezes the side wall of the core tube, while the lower end of the core tube is not frozen, resulting in poor freezing effect and pressure holding effect, leading to inaccurate subsequent detection results.

[0006] The embodiment of the present invention is realized by the following technical scheme: a natural gas hydrate freezing sampling device is arranged in a drill pipe with a drill bit connected at the bottom, comprising an inner pipe, a retaining spring seat is arranged at the lower end of the inner pipe, an upper cold source chamber handle, a lower cold source chamber handle and a sealing plate are arranged in sequence from top to bottom in the inner pipe, a cold source storage chamber is formed between the upper cold source chamber handle and the lower cold source chamber handle, a freezing chamber is arranged between the lower cold source chamber handle and the sealing plate, and a freezing pressure holding chamber is formed between the sealing plate and the retaining spring seat;

[0007] A core tube is coaxially arranged in the freezing chamber, and the lower end of the core tube passes through the sealing plate and is slidably connected to a clamping spring, and the clamping spring seat is sleeved on the clamping spring and slidably abuts against the clamping spring;

[0008] It also includes a valve stem arranged parallel to the axis of the inner tube, a first through hole is arranged on the lower handle of the cold source chamber, a second through hole is arranged on the sealing plate, the valve stem is slidably passed through the upper handle of the cold source chamber, the first through hole and the second through hole, a first piston and a second piston are arranged on the valve stem at intervals, the first piston is embedded in the first through hole, and the second piston is embedded in the second through hole.

[0009] Furthermore, the valve stem is a metal tube, a guide hole communicating with an inner cavity of the valve stem is provided on the valve stem, a sealing plug is provided at the lower end of the inner cavity of the valve stem, and the guide hole is located in the cold source storage chamber.

[0010] Furthermore, a limit block is arranged on the upper end of the valve stem, a return spring is sleeved on the valve stem, and upper and lower ends of the return spring are respectively in contact with the limit block and the upper handle of the cold source chamber.

[0011] Furthermore, a hinge seat is provided at the top of the upper handle of the cold source chamber, a beating plate is hinged on the hinge seat, and the limit block is located on the rotation path of the beating plate;

[0012] The beating plate is also provided with a magnet block, and the top of the upper handle of the cold source chamber is also provided with an electromagnet, and the electromagnet is located on the rotation path of the magnet block.

[0013] Further, the electromagnet is located between the hinge seat and the valve stem, and the electromagnet and the magnet block attract each other;

[0014] It also includes a limit spring, which is arranged on a side of the hinge seat away from the magnet block, and two ends of the limit spring are respectively connected to the hitting plate and the upper handle of the cold source chamber.

[0015] Furthermore, the electromagnet is located on a side of the hinge seat away from the valve stem, and the electromagnet and the magnet block repel each other.

[0016] Furthermore, an axial flow tube is coaxially arranged at the upper end of the inner tube, a partition is sealed at the lower end of the axial flow tube, and a plurality of branch flow channels are circumferentially arranged on the axial flow tube, and the plurality of branch flow channels are communicated with the inner cavity of the axial flow tube;

[0017] The inner tube cavity is provided with a generator, the partition is provided with a rotating shaft, the upper end of the rotating shaft extends to the inner cavity of the axial flow tube and is coaxially sleeved with a turbine, the lower end of the rotating shaft is transmission-connected to the input end of the generator; the generator is electrically connected to the electromagnet.

[0018] Furthermore, a first channel is provided between the cold source storage chamber and the outer wall of the inner tube, and a first one-way pressure relief valve is provided on the first channel, and the first one-way pressure relief valve is used for one-way flow from the cold source storage chamber to the outside of the inner tube;

[0019] A second channel is provided between the freezing chamber and the outer wall of the inner tube, and a second one-way pressure relief valve is provided on the second channel. The second one-way pressure relief valve is used for one-way flow from the freezing chamber to the outside of the inner tube.

[0020] Furthermore, a third channel is radially arranged on the upper edge of the lower connecting piece of the cold source chamber, an overflow hole is arranged on the top of the core tube, the overflow hole is connected with the third channel, a third one-way pressure relief valve is arranged on the third channel, and the third one-way pressure relief valve is used for one-way flow from the inside of the core tube to the outside of the inner tube.

[0021] Furthermore, a natural gas hydrate freezing sampling method, using a natural gas hydrate freezing sampling device, is characterized in that it includes the following steps:

[0022] S1, selecting a target sampling area and lowering the drill pipe;

[0023] S2, injecting a cold source into the cold source storage chamber on the surface, placing a cooling catalyst into the freezing chamber, and then lowering the inner tube into the drill pipe as a whole using a salvage device, retrieving the salvage device after reaching the bottom of the hole and continuing drilling and sampling;

[0024] S3, after the sampling is completed, the circulation of the drilling fluid is stopped, and the inner tube is lifted up by a fishing device for a certain distance, and then the core sample is separated and moved upward by the cooperation of the retaining spring and the retaining spring seat;

[0025] S4, increasing the supply of drilling fluid, the drilling fluid drives the turbine to rotate and then drives the generator to rotate at a high speed, the generator generates current to drive the electromagnet to drive the plate to rotate, the plate drives the valve stem to move downward, so that the first piston and the second piston are separated from the first through hole and the second through hole at the same time, the cold source first enters the freezing chamber and then enters the freezing pressure holding chamber, so as to achieve freezing of the core sample;

[0026] S5. After freezing for 10-20 minutes, remove the inner tube and store the core sample in a liquid nitrogen storage tube or a high-pressure container.

[0027] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0028] 1. When the core tube sampling is completed, the valve stem is driven to move downward, thereby driving the first piston and the second piston to move downward to open the first through hole and the second through hole. At this time, the cold source storage chamber, the freezing chamber and the freezing pressure holding chamber are all connected, and the cold source in the cold source storage chamber first enters the freezing chamber and then enters the freezing pressure holding chamber. The cold source and the cooling catalyst are mixed in the freezing chamber to cool and freeze the core tube, and then enter the freezing pressure holding chamber to form an ice-sealing effect at the sample where the retaining spring is broken, and then a layer of ice is formed at the place where the end of the core tube contacts the core, so that the core is in a sealed environment, thereby achieving the effect of pressure holding, improving the success rate of freezing sampling and keeping the sample as it is, which is helpful to improve the accuracy of subsequent test results.

[0029] 2. The valve stem is a metal tube. A guide hole connected to its inner cavity is provided on the valve stem. A plug is provided at the lower end of the inner cavity of the valve stem. The plug is used to prevent the cold source from flowing out from the lower end. The guide hole is located in the cold source storage chamber. During implementation, the liquid cold source in the cold source storage chamber enters the metal tube through the guide hole. The metal tube is made of a metal with high thermal conductivity, so it is easy to conduct heat, and can pre-cool the cooling catalyst in the freezing chamber to prevent the freezing room temperature from being too high during drilling, causing the hydrate in the core tube to decompose, resulting in subsequent sampling failure. Furthermore, multiple groups of metal tubes can be provided to improve the pre-cooling effect of the cooling catalyst in the freezing chamber.

[0030] 3. When the drill bit is drilling downward and sampling, the drilling fluid is pumped normally. At this time, the drilling fluid is not enough to drive or drive the turbine at a low speed. The turbine drives the rotor of the generator to rotate through the rotating shaft. The rotor rotates in the stator. The magnetic force generated by the current generated by the electromagnet is not enough to overcome the elastic force of the reset spring and the limit spring, that is, the magnetic force generated by the electromagnet is not enough to drive the valve stem to move downward through the plate. When it is necessary to drive the valve stem downward, high-pressure drilling fluid can be pumped to drive the turbine to rotate at a high speed, and then the current generated by the generator increases to generate sufficient magnetic force, which continues to drive the plate to rotate after overcoming the elastic force of the reset spring and the limit spring, and finally drives the valve stem downward. The freezing operation is simple and convenient.

[0031] 4. When it is expected that all the cold sources enter the freezing chamber and the freezing pressure holding chamber for freezing, you can choose to stop pumping the drilling fluid, which will help to freeze the lower end of the core tube, thereby achieving better freezing and pressure holding effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A schematic diagram of the internal structure of a natural gas hydrate freezing sampling device provided by the present invention;

[0034] Figure 2 for Figure 1 A magnified schematic diagram of the structure at center A;

[0035] Figure 3 for Figure 1 A magnified schematic diagram of the structure at B in the middle;

[0036] Icons: 1. Drill bit, 2. Drill pipe, 3. Inner pipe, 31. Upper handle of cold source chamber, 32. Lower handle of cold source chamber, 321. First through hole, 322. Third channel, 323. Third one-way pressure relief valve, 33. Sealing plate, 331. Second through hole, 34. Cold source storage chamber, 341. First channel, 342. First one-way pressure relief valve, 35. Freezer, 351. Second channel, 352. Second one-way pressure relief valve, 36. Freezer Pressure chamber, 4, core tube, 41, retaining ring, 42, retaining ring seat, 43, overflow hole, 5, valve stem, 51, first piston, 52, second piston, 53, guide hole, 54, plug, 55, limit block, 56, return spring, 6, hinge seat, 61, hitting plate, 62, magnet block, 63, limit spring, 7, electromagnet, 71, rotating shaft, 72, turbine, 73, generator, 8, axial flow tube, 81, partition, 82, diversion channel. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0038] 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 invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Reference Figures 1 to 3 As shown, this embodiment provides a natural gas hydrate freezing sampling device, which is arranged in a drill pipe 2 with a drill bit 1 connected to the bottom, including an inner tube 3, a rope corer is arranged above the inner tube 3, a spring seat 42 is arranged at the lower end of the inner tube 3, and a cold source chamber upper hand 31, a cold source chamber lower hand 32 and a sealing plate 33 are arranged in the inner tube 3 from top to bottom in sequence, a cold source storage chamber 34 is formed between the cold source chamber upper hand 31 and the cold source chamber lower hand 32, a freezing chamber 35 is arranged between the cold source chamber lower hand 32 and the sealing plate 33, and a freezing pressure holding chamber 36 is formed between the sealing plate 33 and the spring seat 42.

[0040] More specifically, the cold source in the cold source storage chamber 34 is liquid carbon dioxide, and the cooling catalyst in the freezing chamber 35 is alcohol. The mixture of liquid carbon dioxide and alcohol helps them to vaporize and absorb heat, thereby having a better freezing effect; or alcohol is stored in the cold source storage chamber 34, and dry ice is stored in the freezing chamber 35; or liquid nitrogen is stored in the cold source storage chamber 34, and alcohol is stored in the freezing chamber 35. The combination of liquid nitrogen and alcohol can also achieve better cooling; dry ice can also be placed in the freezing chamber 35, and liquid nitrogen is injected into the cold source storage chamber 34. The combination of the two also has a better refrigeration effect.

[0041] like Figure 1 As shown, a core tube 4 is coaxially arranged in the freezing chamber 35. The lower end of the core tube 4 passes through the sealing plate 33 and is slidably connected to a retaining spring 41. The retaining spring seat 42 is sleeved on the retaining spring 41 and slidably abuts against the retaining spring 41. The core tube 4 is mainly used to store core samples. When the core tube 4 is filled with the mixed sample, the core tube 4 is frozen by injecting a cold source into the freezing chamber 35, so that the core sample remains in a solid state, which is helpful for subsequent sample detection.

[0042] More specifically, it also includes a valve stem 5 arranged parallel to the axis of the inner tube 3, a first through hole 321 is arranged on the lower handle 32 of the cold source chamber, a second through hole 331 coaxial with the first through hole 321 is arranged on the sealing plate 33, the valve stem 5 is slidably penetrated through the upper handle 31 of the cold source chamber, the first through hole 321 and the second through hole 331, a first piston 51 and a second piston 52 are arranged on the valve stem 5 at intervals, the first piston 51 is engaged with the first through hole 321, and the second piston 52 is engaged with the second through hole 331.

[0043] When implementing it, Figure 1As shown, when the sampling of the core tube 4 is completed, the valve stem 5 is driven to move downward, thereby driving the first piston 51 and the second piston 52 to move downward to open the first through hole 321 and the second through hole 331. At this time, the cold source storage chamber 34, the freezing chamber 35 and the freezing pressure holding chamber 36 are all connected, and the cold source in the cold source storage chamber 34 first enters the freezing chamber 35 and then enters the freezing pressure holding chamber 36. The cold source and the cooling catalyst are mixed in the freezing chamber 35 to cool and freeze the core tube 4, and then enter the freezing pressure holding chamber 36, forming an ice-sealing effect at the sample where the retaining spring 41 is broken, and then forming a layer of ice at the place where the end of the core tube 4 contacts the core, so that the core is in a sealed environment, thereby achieving the effect of pressure holding, improving the success rate of freezing sampling and maximally keeping the sample in its original state, which helps to improve the accuracy of subsequent test results.

[0044] More specifically, Figure 1-3 As shown, the valve stem 5 is a metal tube, and a guide hole 53 connected to its inner cavity is provided on the valve stem 5. A plug 54 is provided at the lower end of the inner cavity of the valve stem 5. The plug 54 is used to prevent the cold source from flowing out from the lower end. The guide hole 53 is located in the cold source storage chamber 34. During implementation, the liquid cold source in the cold source storage chamber 34 enters the metal tube through the guide hole 53. The metal tube is made of a metal with a high thermal conductivity, and thus it is easy to conduct heat, and can pre-cool the cooling catalyst in the freezing chamber 35 to prevent the freezing chamber 35 from being overheated during drilling, causing the hydrate in the core tube 4 to decompose, resulting in subsequent sampling failure. Furthermore, multiple groups of metal tubes can be provided to improve the pre-cooling effect of the cooling catalyst in the freezing chamber 35.

[0045] like Figure 1 As shown, a limit block 55 is provided at the upper end of the valve stem 5, and the limit block 55 blocks the upper end of the inner cavity of the valve stem 5. A return spring 56 is sleeved on the valve stem 5, and the upper and lower ends of the return spring 56 are respectively in contact with the limit block 55 and the upper handle 31 of the cold source chamber, and then the valve stem 5 is driven to move upward by the return spring 56, so that the first piston 51 and the second piston 52 respectively block the first through hole 321 and the second through hole 331, preventing the cold source from entering the freezing chamber 35 and the freezing pressure holding chamber 36 too early, and also ensuring that the cooling catalyst will not enter the freezing pressure holding chamber 36 too early.

[0046] A hinge seat 6 is provided at the top of the cold source chamber upper handle 31, a plate 61 is hinged on the hinge seat 6, and a limit block 55 is located on the rotation path of the plate 61; a magnet block 62 is also provided on the plate 61, and an electromagnet 7 is also provided at the top of the cold source chamber upper handle 31, and the electromagnet 7 is located on the rotation path of the magnet block 62. Then, the magnet block 62 is driven by the electromagnet 7 to generate magnetism, and then the plate 61 is driven to rotate, and when the plate 61 rotates, it acts on the limit block 55, and then the valve stem 5 is driven to move downward, so that the cold source enters the freezing chamber 35 and the freezing pressure chamber 36, and the freezing operation is performed.

[0047] As one example, Figure 1-3 As shown, the electromagnet 7 is located between the hinge seat 6 and the valve stem 5, and the electromagnet 7 and the magnet block 62 attract each other; it also includes a limit spring 63, which is arranged on the side of the hinge seat 6 away from the magnet block 62, and the two ends of the limit spring 63 are respectively connected to the hitting plate 61 and the upper handle 31 of the cold source chamber, which is used to limit the hitting plate 61 to prevent the magnet block 62 from being too far away from the electromagnet 7, but the limit spring 63 can also be omitted when the hitting plate 61 does not deviate. Then, the electromagnet 7 absorbs the magnet block 62, and then drives the hitting plate 61 to press the valve stem 5 downward.

[0048] As another embodiment, the electromagnet 7 is located on the side of the hinge seat 6 away from the valve stem 5, and the electromagnet 7 and the magnet block 62 repel each other. Then, the electromagnet 7 generates magnetism and the magnet block 62 repel each other, so as to drive the striking plate 61 to press the valve stem 5 downward.

[0049] More specifically, Figure 1 and 2 As shown, an axial flow tube 8 is coaxially arranged between the upper end of the inner tube 3 and the rope corer, a partition 81 is sealed at the lower end of the axial flow tube 8, a plurality of branch channels 82 are circumferentially arranged on the axial flow tube 8, the plurality of branch channels 82 are connected with the inner cavity of the axial flow tube 8, drilling fluid flows through the inner cavity of the axial flow tube 8, and the drilling fluid flows from the plurality of branch channels 82 to between the inner tube 3 and the drill pipe 2 after passing through the turbine 72;

[0050] A generator 73 is provided in the inner cavity of the inner tube 3, a rotating shaft 71 is provided on the partition 81, the upper end of the rotating shaft 71 extends to the inner cavity of the axial flow tube 8 and is coaxially sleeved with a turbine 72, and the lower end of the rotating shaft 71 is transmission-connected to the input end of the generator 73; the generator 73 is electrically connected to the electromagnet 7.

[0051] In specific implementation, when the drill bit 1 is drilling downward and sampling, the drilling fluid is pumped normally. At this time, the drilling fluid is not enough to drive or drive the turbine 72 at a low speed. The turbine 72 drives the rotor of the generator to rotate through the rotating shaft 71. The rotor rotates in the stator. The magnetic force generated by the current generated by the electromagnet 7 is not enough to overcome the elastic force of the reset spring 56 and the limit spring 63, that is, the magnetic force generated by the electromagnet is not enough to drive the valve stem 5 to move downward through the plate 61. When it is necessary to drive the valve stem 5 to move downward, high-pressure drilling fluid can be pumped to drive the turbine 72 to rotate at a high speed, and then the current generated by the generator 73 increases to generate sufficient magnetic force, which continues to drive the plate 61 to rotate after overcoming the elastic force of the reset spring 56 and the limit spring 63, and finally drives the valve stem 5 to move downward.

[0052] The relationship between the current, the number of coil turns and the magnetic field strength can be expressed by the formula H = N*I / Le, where H is the magnetic field strength, in A / m; N is the number of turns of the excitation coil; I is the measured value of the excitation current, in A; Le is the effective magnetic path length of the test sample, in m. Therefore, when the number of coil turns N and the effective magnetic path length Le are constant, the greater the current I, the greater the magnetic field strength H. Therefore, we increase the drilling fluid pump volume so that the current provided by the turbine 72 driving the generator 73 reaches a certain value, and the magnetic field strength of the electromagnet 7 increases to the point where the magnet stone can be sucked down, thereby driving the plate 61 to move downward, and driving the valve stem 5 to move downward at the same time.

[0053] like Figure 1 and 2 As shown, a first channel 341 is provided between the cold source storage chamber 34 and the outer wall of the inner tube 3, and a first one-way pressure relief valve 342 is provided on the first channel 341. The first one-way pressure relief valve 342 is used for one-way flow from the cold source storage chamber 34 to the outside of the inner tube 3. In specific implementation, a cold source is stored in the cold source storage chamber 34. If the pressure in the cold source storage chamber 34 increases during filling or subsequent vaporization of the cold source, the pressure can be relieved through the first one-way pressure relief valve 342.

[0054] like Figure 1 As shown, a second channel 351 is provided between the freezing chamber 35 and the outer wall of the inner tube 3, and a second one-way pressure relief valve 352 is provided on the second channel 351. The second one-way pressure relief valve 352 is used for one-way flow from the freezing chamber 35 to the outside of the inner tube 3. Similarly, after the cold source enters the freezing chamber 35, if the pressure in the freezing chamber 35 increases, the pressure can be relieved through the second one-way pressure relief valve 352.

[0055] like Figure 1 and 3 As shown, a third channel 322 is radially arranged on the lower handle 32 of the cold source chamber, an overflow hole 43 is arranged on the top of the core tube 4, the overflow hole 43 is connected to the third channel 322, and a third one-way pressure relief valve 323 is arranged on the third channel 322. The third one-way pressure relief valve 323 is used for one-way flow from the inside of the core tube 4 to the outside of the inner tube 3; and then when the core sample enters the core tube 4, the air or liquid inside the core tube 4 can be discharged through the third one-way pressure relief valve 323.

[0056] More specifically, the inner walls of the cold source storage room 34, the freezing room 35 and the freezing pressure holding room 36 are paved with thermal insulation materials, usually rock wool boards, glass wool boards, polyurethane foam boards and other materials with relatively low thermal conductivity, to ensure that the heat generated during the drilling process will hardly be conducted in and to ensure that the "coldness" of the cold source during the freezing process will not be wasted.

[0057] At the same time, a plurality of sealing rings are arranged between the valve stem 5 and the upper handle 31 of the cold source chamber to maintain the pressure of the cold source storage chamber 34 under the premise of ensuring the normal sliding of the valve stem 5. Similarly, when the first piston 51 and the second piston 52 cooperate with the first through hole 321 and the second through hole 331 respectively, they also have the pressure maintaining effect.

[0058] A natural gas hydrate freezing sampling method, using a natural gas hydrate freezing sampling device, comprises the following steps:

[0059] S1, select the target sampling area, set up the drilling platform, and lower the drill pipe 2 and its assembly, that is, drill down to the target depth;

[0060] S2, injecting cold source into the cold source storage chamber 34 on the ground surface, placing a cooling catalyst into the freezing chamber 35, and then using a salvage device to lower the inner tube 3 into the drill pipe 2 as a whole, and continue drilling and sampling after reaching the bottom of the hole;

[0061] S3. After sampling is completed, stop the circulation of drilling fluid, use the fishing device to lift the inner tube 3 for a certain distance, and then separate the core sample and move it upward through the circlip 41 and the circlip seat 42. It does not need to be moved up too much. When the inner tube 3 moves upward, the circlip 41 will be stuck to the core due to its own gravity and the limit of the circlip seat 42. The circlip seat 42 sits on the step inside the drill bit 1 to drive the circlip 41 to further break the core, ensuring the recovery of the core. After the core is broken, you can stop lifting the inner tube 3 assembly. ;

[0062] S4, then increase the drilling fluid supply, the drilling fluid drives the turbine 72 to rotate and then drives the generator 73 to rotate at a high speed, generates current to drive the electromagnet 7 to drive the plate 61 to rotate, and then drives the valve stem 5 to move downward, so that the first piston 51 and the second piston 52 are separated from the first through hole 321 and the second through hole 331 at the same time, and the cold source first enters the freezing chamber 35 and then enters the freezing pressure chamber 36 to achieve pressure-maintained freezing of the core sample. When it is expected that all the cold sources enter the freezing chamber 35 and the freezing pressure chamber 36 for freezing, it is possible to stop pumping the drilling fluid, which is helpful to freeze the lower end of the core tube;

[0063] S5. After freezing for 10-20 minutes, take out the inner tube 3 and store the core sample in a liquid nitrogen storage tube or a high-pressure container.

[0064] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A natural gas hydrate freezing sampling device, arranged in a drill pipe (2) with a drill bit (1) connected to the bottom, characterized in that: The invention comprises an inner tube (3), a spring retaining seat (42) is arranged at the lower end of the inner tube (3), an upper cold source chamber handle (31), a lower cold source chamber handle (32) and a sealing plate (33) are arranged in sequence from top to bottom in the inner tube (3), a cold source storage chamber (34) is formed between the upper cold source chamber handle (31) and the lower cold source chamber handle (32), a freezing chamber (35) is arranged between the lower cold source chamber handle (32) and the sealing plate (33), and a freezing pressure holding chamber (36) is formed between the sealing plate (33) and the spring retaining seat (42); A core tube (4) is coaxially arranged in the freezing chamber (35); the lower end of the core tube (4) passes through the sealing plate (33) and is slidably connected to a retaining spring (41); the retaining spring seat (42) is sleeved on the retaining spring (41) and is in slidable contact with the retaining spring (41); It also includes a valve stem (5) arranged parallel to the axis of the inner tube (3), a first through hole (321) is arranged on the lower handle (32) of the cold source chamber, a second through hole (331) is arranged on the sealing plate (33), the valve stem (5) is slidably inserted into the upper handle (31) of the cold source chamber, the first through hole (321) and the second through hole (331), a first piston (51) and a second piston (52) are arranged on the valve stem (5) at intervals, the first piston (51) is engaged with the first through hole (321), and the second piston (52) is engaged with the second through hole (331).

2. A natural gas hydrate freezing sampling device according to claim 1, characterized in that: The valve stem (5) is a metal tube. The valve stem (5) is provided with a guide hole (53) communicating with its inner cavity. A sealing plug (54) is provided at the lower end of the inner cavity of the valve stem (5). The guide hole (53) is located in the cold source storage chamber (34).

3. A natural gas hydrate freezing sampling device according to claim 2, characterized in that: A limit block (55) is arranged at the upper end of the valve stem (5), and a return spring (56) is sleeved on the valve stem (5), and the upper and lower ends of the return spring (56) are respectively in contact with the limit block (55) and the upper handle (31) of the cold source chamber.

4. A natural gas hydrate freezing sampling device according to claim 3, characterized in that: A hinge seat (6) is provided at the top of the cold source chamber upper handle (31), a beating plate (61) is hingedly connected to the hinge seat (6), and the limit block (55) is located on the rotation path of the beating plate (61); The hitting plate (61) is also provided with a magnet block (62), and the top of the cold source chamber upper handle (31) is also provided with an electromagnet (7), and the electromagnet (7) is located on the rotation path of the magnet block (62).

5. A natural gas hydrate freezing sampling device according to claim 4, characterized in that: The electromagnet (7) is located between the hinge seat (6) and the valve stem (5), and the electromagnet (7) and the magnet block (62) attract each other; It also includes a limit spring (63), which is arranged on the side of the hinge seat (6) away from the magnet block (62), and the two ends of the limit spring (63) are respectively connected to the hitting plate (61) and the upper handle (31) of the cold source chamber.

6. A natural gas hydrate freezing sampling device according to claim 4, characterized in that: The electromagnet (7) is located on a side of the hinge seat (6) away from the valve stem (5), and the electromagnet (7) and the magnet block (62) repel each other.

7. A natural gas hydrate freezing sampling device according to any one of claims 5 or 6, characterized in that: An axial flow tube (8) is coaxially arranged at the upper end of the inner tube (3); a partition plate (81) is sealed at the lower end of the axial flow tube (8); a plurality of branch flow channels (82) are circumferentially arranged on the axial flow tube (8); and the plurality of branch flow channels (82) are in communication with the inner cavity of the axial flow tube (8); A generator (73) is disposed in the inner cavity of the inner tube (3); a rotating shaft (71) is disposed on the partition (81); the upper end of the rotating shaft (71) extends into the inner cavity of the axial flow tube (8) and is coaxially sleeved with a turbine (72); the lower end of the rotating shaft (71) is transmission-connected to the input end of the generator (73); and the generator (73) is electrically connected to the electromagnet (7).

8. A natural gas hydrate freezing sampling device according to claim 7, characterized in that: A first channel (341) is provided between the cold source storage chamber (34) and the outer wall of the inner tube (3), and a first one-way pressure relief valve (342) is provided on the first channel (341). The first one-way pressure relief valve (342) is used for one-way flow from the cold source storage chamber (34) to the outside of the inner tube (3); A second channel (351) is provided between the freezing chamber (35) and the outer wall of the inner tube (3), and a second one-way pressure relief valve (352) is provided on the second channel (351). The second one-way pressure relief valve (352) is used for one-way flow from the freezing chamber (35) to the outside of the inner tube (3).

9. A natural gas hydrate freezing sampling device according to claim 8, characterized in that: A third channel (322) is radially arranged on the lower handle (32) of the cold source chamber, an overflow hole (43) is arranged on the top of the core tube (4), the overflow hole (43) is communicated with the third channel (322), a third one-way pressure relief valve (323) is arranged on the third channel (322), and the third one-way pressure relief valve (323) is used for one-way flow from the inside of the core tube (4) to the outside of the inner tube (3).

10. A method for freezing and sampling natural gas hydrates, using a natural gas hydrate freezing and sampling device as claimed in claim 9, characterized in that: The following steps are involved: S1, selecting a target sampling area and lowering the drill pipe (2); S2, injecting a cold source into the cold source storage chamber (34) on the ground surface, placing a cooling catalyst into the freezing chamber (35), and then using a salvage device to lower the inner tube (3) as a whole into the drill pipe (2), retrieving the salvage device after reaching the bottom of the hole and continuing drilling and sampling; S3, after the sampling is completed, the circulation of the drilling fluid is stopped, and the inner tube (3) is lifted up by a fishing device for a certain distance, and then the core sample is separated and moved upward by the cooperation of the retaining spring (41) and the retaining spring seat (42); S4, increasing the supply of drilling fluid, the drilling fluid drives the turbine (72) to rotate and then drives the generator (73) to rotate at a high speed, the generator (73) generates current to enable the electromagnet (7) to drive the hitting plate (61) to rotate, the hitting plate (61) drives the valve stem (5) to move downward, so that the first piston (51) and the second piston (52) are separated from the first through hole (321) and the second through hole (331) at the same time, the cold source first enters the freezing chamber (35) and then enters the freezing pressure holding chamber (36), so as to realize the freezing of the core sample; S5. After freezing for 10-20 minutes, take out the inner tube (3) and store the core sample in a liquid nitrogen storage tube or a high-pressure container.

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