A device and method for carbon dioxide sequestration in a depleted natural gas hydrate reservoir

Abstract

This invention discloses a carbon dioxide sequestration device and method in a waste natural gas hydrate reservoir. The device comprises a sequestration main pipe, a dissolution branch pipe, and a discharge pipe. A horizontal pipe assembly is installed at the bottom of the sequestration main pipe, extending to below the hydrate layer. The horizontal pipe assembly has several dispersion holes circumferentially formed. The dissolution branch pipe forms several ventilation chambers. The discharge pipe is installed through the ventilation chambers, and a horizontal discharge pipe is vertically arranged at the bottom of the discharge pipe. In this invention, carbon dioxide is injected into the hydrate layer at different angles and in a diffusion manner, expanding the contact range between carbon dioxide and the hydrate layer. The carbon dioxide partially dissolves in the water inside the ventilation chamber. The discharge channel is opened by the opening and closing valve shaft, and the water containing dissolved carbon dioxide gas is injected into different heights within the hydrate layer through the discharge channel and the horizontal discharge pipe. Under the diffusion effect of the water, the carbon dioxide within the hydrate layer is more easily diffused to a farther location to undergo a displacement reaction with the methane hydrate, further expanding the diffusion range.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide sequestration technology, specifically to a device and method for carbon dioxide sequestration in waste natural gas hydrate reservoirs. Background Technology

[0002] Collecting and storing emitted carbon dioxide, isolating it from the atmosphere for a long period, can achieve the goal of mitigating carbon dioxide emissions. Long-term storage schemes for emitted carbon dioxide include: 1) storing it in geological structures (such as oil and gas fields, coal seams, and underground brine aquifers); 2) injecting carbon dioxide into the deep sea; and 3) converting carbon dioxide into other thermodynamically stable minerals. Among these, marine carbon dioxide sequestration refers to storing captured carbon dioxide in the deep sea or on the seabed and under seafloor sediments, isolating it from the atmosphere. In marine sequestration, natural gas hydrate reservoirs are considered ideal sites for carbon dioxide sequestration. Carbon dioxide sequestration is carried out in abandoned natural gas hydrate reservoirs to achieve both carbon dioxide sequestration and the treatment of abandoned natural gas hydrate reservoirs.

[0003] Injecting gases such as carbon dioxide, which are more likely to form hydrates than methane, to replace the methane in the hydrates allows for the extraction of methane by converting carbon dioxide into hydrates. During the replacement process, a large amount of heat is released, providing the necessary heat for the decomposition of methane hydrates. The methane hydrates decompose to form methane, while the carbon dioxide forms hydrates and is sealed within the hydrate layer, thus burying the carbon dioxide in the form of hydrates on the seabed and reducing the greenhouse effect.

[0004] However, the input locations of carbon dioxide in the ocean are fixed and limited, resulting in a small contact range between carbon dioxide and hydrates, a small area for carbon dioxide replacement, and thus low carbon dioxide replacement efficiency. Summary of the Invention

[0005] To address this issue, the present invention provides a device and method for carbon dioxide sequestration in waste natural gas hydrate reservoirs, which effectively solves the problems of small contact range between carbon dioxide and methane hydrate and low carbon dioxide replacement rate in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution: a carbon dioxide sequestration device for waste natural gas hydrate reservoirs, comprising:

[0007] A sealing main pipe has a horizontal pipe assembly installed at its bottom. The horizontal pipe assembly is vertically installed on the sealing main pipe and communicates with the horizontal pipe assembly. The bottom end of the sealing main pipe extends below the hydrate layer. The horizontal pipe assembly is disposed within the hydrate layer and has a plurality of dispersion holes formed circumferentially. The dispersion holes are used to inject carbon dioxide into the hydrate layer. An output channel for carbon dioxide injection is formed within the dispersion holes, and the extension line of the straight line containing the output channel is aligned with the central axis inside the horizontal pipe assembly.

[0008] Dissolving branch pipes are installed at equal intervals on the main sealing pipe. The dissolving branch pipes form several ventilation chambers. The interior of the ventilation chambers is connected to the interior of the main sealing pipe. A water injection hole is provided at the top of the ventilation chamber. Seawater is injected into the ventilation chamber through the water injection hole. A floating component is provided in the ventilation chamber. A sealing block is installed on the floating component. The sealing block is connected to the water injection hole.

[0009] A discharge pipe is installed through the ventilation chamber and away from the main sealing pipe. A discharge groove is formed at the penetration point of the discharge pipe on the bottom wall of the ventilation chamber. An opening and closing valve shaft is installed inside the discharge pipe. The opening and closing valve shaft moves up and down to block the discharge groove.

[0010] A horizontal drain pipe is vertically located at the bottom of the drain fitting, and the drain fitting is connected to the center of the horizontal drain pipe. Several drainage grooves are arranged around the horizontal drain pipe, and the height of the horizontal drain pipe is higher than the height of the horizontal pipe assembly.

[0011] Furthermore, the ventilation chamber is provided with a first ventilation channel, a water injection chamber, and a second ventilation channel, which are connected in sequence.

[0012] The first ventilation channel is connected at one end to the interior of the main sealing pipe, and at the other end to the side of the water injection chamber. The second ventilation channel is connected at one end to the side of the water injection chamber, and at the other end to the interior of the main sealing pipe.

[0013] Furthermore, a first connecting cylinder is installed on one side wall of the water injection chamber, and a second connecting cylinder is installed on the other side wall. The first connecting cylinder is connected to the first venting channel, and the second connecting cylinder is connected to the second venting channel.

[0014] Both the first connecting cylinder and the second connecting cylinder are vertically installed on the inner wall of the water injection chamber, with the first connecting cylinder near the bottom of the water injection chamber and the second connecting cylinder near the top of the water injection chamber.

[0015] Furthermore, the floating component includes a floating disc disposed within the ventilated chamber and a through groove disposed at the center of the floating disc;

[0016] The sealing block is connected to the upper end of the floating plate, and the opening and closing valve shaft is installed through the through groove, passing through the water injection hole and the sealing block;

[0017] The outer diameter of the opening / closing valve shaft is the same as the inner diameter of the through groove, and the outer diameter of the opening / closing valve shaft is smaller than the inner diameter of the water injection hole.

[0018] Furthermore, both the sealing block and the water injection hole are configured as frustum shapes;

[0019] A mesh plate is provided on the opening and closing valve shaft, and the mesh plate abuts against the floating plate;

[0020] The thickness of the floating plate is greater than the inner diameter of the second connecting cylinder.

[0021] Furthermore, the drainage channel is composed of a first connecting channel, a second connecting channel, and a second connecting channel connected in sequence;

[0022] The inner diameter of the first connecting groove is larger than the inner diameter of the third connecting groove, and the bottom inner diameter of the second connecting groove is smaller than the top inner diameter of the second connecting groove.

[0023] Furthermore, a connecting valve block is installed on the opening and closing valve shaft, a valve column is connected to the bottom of the connecting valve block, the valve column fits into the third connecting groove, and the connecting valve block fits into the inner wall of the second connecting groove near the inner wall of the third connecting groove.

[0024] An installation platform is provided at the upper end of the opening and closing valve shaft, the sealing main pipe is installed on the installation platform, and a drive cylinder is also provided on the installation platform. The opening and closing valve shaft is connected to the output end of the drive cylinder.

[0025] Furthermore, the horizontal pipe assembly includes a connecting outer pipe and a connecting inner pipe;

[0026] The inner connecting tube is connected to the bottom of the main sealing tube, the main sealing tube passes through the outer connecting tube, and the inner connecting tube has several vent holes on its side wall. The line where the vent holes are located is offset from the line where the output channel is located.

[0027] Furthermore, the discharge pipe includes a connecting branch pipe connected to the ventilated chamber and a water inlet provided on the connecting branch pipe;

[0028] The opening and closing valve shaft passes through the connecting branch pipe, the connecting branch pipe is connected to the third connecting groove, the horizontal pipe is connected to the end of the connecting branch pipe, and a sliding valve block is connected to the part of the opening and closing valve shaft corresponding to the part inside the connecting branch pipe, and the sliding valve block abuts against the water inlet.

[0029] To solve the above-mentioned technical problems, the present invention further provides the following technical solution: a method for storing carbon dioxide in a waste natural gas hydrate reservoir, comprising the following steps:

[0030] Step 100: The horizontal pipe assembly and the main storage pipe are vertically lowered into the ocean, with the horizontal pipe assembly extending to the hydrate layer;

[0031] Step 200: Inject seawater of the corresponding height into the ventilation chamber through the water injection hole, and block the passage for seawater to enter the ventilation chamber by opening and closing the valve shaft.

[0032] Step 300: Carbon dioxide gas is introduced into the main sealing pipe. Part of the carbon dioxide gas dissolves in water through the ventilation chamber, and the remaining carbon dioxide gas is discharged to the hydrate layer through the ventilation chamber and the horizontal pipe assembly.

[0033] Step 400: Open the drain trough and water injection hole through the opening and closing valve shaft, and water containing dissolved carbon dioxide gas is injected into the hydrate layer through the drain trough and horizontal pipe.

[0034] Step 500: Close the drain trough by opening and closing the valve shaft, and open the channel for seawater to enter the ventilation chamber. Repeat steps 200, 300, 400 and 500.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] In this invention, a horizontal tube assembly is provided at the bottom of the main sealing tube. The horizontal tube assembly has several dispersion holes formed around its circumference. The dispersion holes are used to inject carbon dioxide into the hydrate layer. An output channel for carbon dioxide injection is formed in the dispersion holes. The extension line of the straight line of the output channel is directly opposite the central axis inside the horizontal tube assembly, so that carbon dioxide is injected into the hydrate layer at different angles and in different diffusion forms, thereby expanding the contact range between carbon dioxide and the hydrate layer.

[0037] In addition, the dissolving branch pipe forms a ventilation chamber. Carbon dioxide partially dissolves in the water inside the ventilation chamber. The drain channel is opened by the opening and closing valve shaft, and the water containing dissolved carbon dioxide gas is injected into different height positions in the hydrate layer through the drain channel and horizontal drain pipe. Under the diffusion effect of water, the carbon dioxide in it is more likely to diffuse to a farther position and undergo a replacement reaction with the methane hydrate, which further expands the diffusion range and improves the replacement efficiency. Attached Figure Description

[0038] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a carbon dioxide sequestration device for waste natural gas hydrate reservoirs provided in an embodiment of the present invention;

[0040] Figure 2 A side view of a carbon dioxide sequestration device in a waste natural gas hydrate reservoir, provided in an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the structure in an embodiment of the present invention where the water inlet is closed, the water inlet is closed, and the drain trough is closed;

[0042] Figure 4 This is a schematic diagram of the structure in an embodiment of the present invention, in which the water inlet is closed, the water inlet is open, and the drain trough is open.

[0043] Figure 5 This is a schematic diagram of the structure in an embodiment of the present invention, in which the water inlet is closed, the water inlet is open, and the drain trough is closed;

[0044] Figure 6 This is a schematic diagram of the structure in an embodiment of the present invention, in which the water supply hole is open, the water injection hole is open, and the drain trough is closed.

[0045] Figure 7 This is a side view of the ventilation chamber in an embodiment of the present invention.

[0046] Figure 8 This is a schematic diagram of the sealing block in an embodiment of the present invention.

[0047] The labels in the diagram represent the following:

[0048] 1-Sealing main pipe; 2-Dissolving branch pipe; 3-Discharge fitting; 4-Horizontal pipe assembly; 5-Dispersion hole; 6-Output channel; 7-Opening / closing valve shaft; 8-Horizontal pipe; 9-Drainage trough; 10-Connecting valve block; 11-Mounting platform; 12-Drive cylinder; 13-Sliding valve block; 14-Valve column;

[0049] 21-Ventilation chamber; 22-Water injection hole; 23-Floater; 24-Blocking block; 25-First ventilation channel; 26-Water injection chamber; 27-Second ventilation channel; 28-First connecting tube; 29-Second connecting tube;

[0050] 31-Drainage channel; 32-Connecting branch pipe; 33-Water delivery hole;

[0051] 41 - Connect to outer pipe; 42 - Connect to inner pipe; 43 - Exhaust port;

[0052] 231-Floating disc; 232-Through groove; 233-Grid plate;

[0053] 311 - First connecting groove; 312 - Second connecting groove; 313 - Third connecting groove. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] like Figure 1 and Figure 2 As shown, the present invention provides a carbon dioxide sequestration device for waste natural gas hydrate reservoirs, comprising a sequestration main pipe 1, a dissolution branch pipe 2, and a discharge pipe 3.

[0056] The main sealing pipe 1 has a horizontal pipe assembly 4 installed at its bottom. The horizontal pipe assembly 4 is vertically installed on the main sealing pipe 1 and is connected to the horizontal pipe assembly 4. The bottom end of the main sealing pipe 1 extends to the bottom of the hydrate layer. The horizontal pipe assembly 4 is located inside the hydrate layer. Several dispersion holes 5 are formed around the horizontal pipe assembly 4. The dispersion holes 5 are used to inject carbon dioxide into the hydrate layer. An output channel 6 for carbon dioxide injection is formed inside the dispersion holes 5. The extension line of the straight line of the output channel 6 is directly opposite the central axis inside the horizontal pipe assembly 4.

[0057] Dissolving branch pipes 2 are installed at equal intervals on the main sealing pipe 1. The dissolving branch pipes 2 form several ventilation chambers 21. The interior of the ventilation chambers 21 is connected to the interior of the main sealing pipe 1. A water injection hole 22 is provided at the top of the ventilation chamber 21. Seawater is injected into the ventilation chamber 21 through the water injection hole 22. A floating component 23 is provided inside the ventilation chamber 21. A sealing block 24 is installed on the floating component 23. The sealing block 24 is connected to the water injection hole 22.

[0058] The discharge pipe 3 is installed through the ventilation chamber 21 and away from the main sealing pipe 1. The discharge pipe 3 forms a discharge groove 31 at the penetration point of the bottom wall of the ventilation chamber 21. An opening and closing valve shaft 7 is installed inside the discharge pipe 3. The opening and closing valve shaft 7 moves up and down to block the discharge groove 31.

[0059] A horizontal pipe 8 is vertically located at the bottom of the discharge pipe 3. The discharge pipe 3 is connected to the center of the horizontal pipe 8. Several drainage grooves 9 are arranged around the horizontal pipe 8. The height of the horizontal pipe 8 is higher than the height of the horizontal pipe assembly 4.

[0060] Among them, the horizontal pipe assembly 4 is used to discharge carbon dioxide, and the horizontal drain pipe 8 is used to discharge seawater containing dissolved carbon dioxide.

[0061] In this invention, a horizontal tube assembly 4 is provided at the bottom of the sealing main tube 1. The horizontal tube assembly 4 has a plurality of dispersion holes 5 formed around its circumference. The dispersion holes 5 are used to inject carbon dioxide into the hydrate layer. An output channel 6 for carbon dioxide injection is formed in the dispersion holes 5. The extension line of the straight line where the output channel 6 is located is directly opposite the central axis inside the horizontal tube assembly 4, so that carbon dioxide is injected into the hydrate layer at different angles and in different diffusion forms, thereby expanding the contact range between carbon dioxide and the hydrate layer.

[0062] In addition, the dissolving branch pipe 2 forms a ventilation chamber 21. Carbon dioxide dissolves in water inside the ventilation chamber 21. The discharge channel 31 is opened by the opening and closing valve shaft 7. Water containing dissolved carbon dioxide gas is injected into different height positions in the hydrate layer through the discharge channel 31 and the horizontal discharge pipe 8. Under the diffusion effect of water, the carbon dioxide in it is more likely to diffuse to a farther position and undergo a replacement reaction with the methane hydrate, which further expands the diffusion range and improves the replacement efficiency.

[0063] To facilitate the input and output of carbon dioxide, this invention is designed as follows: Figure 2 and Figure 7 As shown, the ventilation chamber 21 is provided with a first ventilation channel 25, a water injection chamber 26, and a second ventilation channel 27. The first ventilation channel 25, the water injection chamber 26, and the second ventilation channel 27 are connected in sequence. The end of the first ventilation channel 25 is connected to the inside of the sealing main pipe 1, and the other end is connected to the side of the water injection chamber 26. The end of the second ventilation channel 27 is connected to the side of the water injection chamber 26, and the other end is connected to the inside of the sealing main pipe 1.

[0064] Carbon dioxide enters the water injection chamber 26 through the first ventilation channel 25. Seawater is injected into the water injection chamber 26. The seawater inside the chamber is discharged through the second ventilation channel 27. In this invention, there are several ventilation chambers 21, which can be equally spaced on the main sealing pipe 1. The number of the first ventilation channel 25, the water injection chamber 26 and the second ventilation channel 27 are the same. After the carbon dioxide dissolves in the multiple ventilation chambers 21, the remaining carbon dioxide enters the marine compound layer from the bottom of the main sealing pipe 1 and the horizontal pipe assembly 4.

[0065] To maximize the dissolution of carbon dioxide within the water injection chamber 26, the present invention further incorporates the following design: a first connecting cylinder 28 is installed on one side wall of the water injection chamber 26, and a second connecting cylinder 29 is installed on the other side wall. The first connecting cylinder 28 communicates with the first ventilation channel 25, and the second connecting cylinder 29 communicates with the second ventilation channel 27. Both the first connecting cylinder 28 and the second connecting cylinder 29 are vertically installed on the inner wall of the water injection chamber 26, with the first connecting cylinder 28 located near the bottom of the water injection chamber 26 and the second connecting cylinder 29 located near the top of the water injection chamber 26.

[0066] The first connecting tube 28 is directly opposite the bottom of the water injection chamber 26, and the second connecting tube 29 is directly opposite the top of the water injection chamber 26. Carbon dioxide enters the bottom of the water injection chamber 26 through the first connecting tube 28, which is the bottom of the seawater in the water injection chamber 26. After rising from the bottom of the seawater to the top of the water injection chamber 26, it is discharged from the second connecting tube 29. During this process, some carbon dioxide dissolves in the water injection chamber 26.

[0067] In order to drive the sealing block 24 to seal the water injection hole 22, the present invention provides a floating element 23, which adopts the following preferred embodiment, such as... Figure 8 As shown, the floating component 23 includes a floating disc 231 disposed in the ventilation chamber 21, a through groove 232 disposed in the center of the floating disc 231, a sealing block 24 connected to the upper end of the floating disc 231, and an opening and closing valve shaft 7 disposed through the through groove 232, the opening and closing valve shaft 7 passing through the water injection hole 22 and the sealing block 24.

[0068] In the above embodiment, after a certain amount of seawater is injected into the water injection chamber 26, the floating plate 231 floats on the seawater. At this time, the sealing block 24 on it seals the water injection hole 22. The opening and closing valve shaft 7 passes through the floating plate 231, and the floating plate 231 follows the path of the seawater as it floats or sinks along the opening and closing valve shaft 7.

[0069] In this invention, the opening and closing state of the water injection hole 22 can be adjusted by the sealing block 24. In order to prevent the opening and closing valve shaft 7 from blocking the water injection hole 22, the present invention is designed as follows: the outer diameter of the opening and closing valve shaft 7 is the same as the inner diameter of the through groove 232, and the outer diameter of the opening and closing valve shaft 7 is smaller than the inner diameter of the water injection hole 22.

[0070] During the seawater discharge process, the liquid level in the water injection chamber 26 drops, and the sealing block 24 will descend along with the floating plate 231, opening the water injection hole 22. In order to prevent the floating plate 231 from falling to the bottom of the water injection chamber 26 before the water inside is completely discharged during the seawater discharge process, the present invention makes the following design: the sealing block 24 and the water injection hole 22 are both set as frustum shapes, and a grid plate 233 is provided on the opening and closing valve shaft 7, which abuts against the floating plate 231.

[0071] During the seawater discharge process, the opening and closing valve shaft 7 moves upward, causing the grid plate 233 to move upward, supporting the floating plate 231, so that the sealing block 24 is away from the upper water injection hole 22 and the lower drainage channel 31.

[0072] In this embodiment, the amount of seawater injected each time is usually fixed. It is only necessary to control the opening and closing time of the water injection hole 22 each time. The sealing block 24 on the float plate 231 is just sealed on the water injection hole 22. The float plate 231 has gravity and part of the float plate 231 is below the liquid surface. In order to prevent seawater from being discharged from the second connecting cylinder 29, the liquid level is usually lower than the second connecting cylinder 29. Therefore, the thickness of the float plate 231 is greater than the inner diameter of the second connecting cylinder 29. In the case of fixed amount of seawater, the upper surface of the float plate 231 abuts against the water injection cavity 26 under the action of buoyancy, and the sealing block 24 is engaged in the water injection hole 22.

[0073] In order to enable the upward movement of the opening and closing valve shaft 7 to drive the opening of the drain groove 31, the present invention also includes the following design, such as... Figure 3 As shown, the groove 31 is connected in sequence by a first connecting groove 311, a second connecting groove 312, and a second connecting groove 313. The inner diameter of the first connecting groove 311 is larger than the inner diameter of the third connecting groove 313, and the bottom inner diameter of the second connecting groove 312 is smaller than the top inner diameter of the second connecting groove 312.

[0074] A connecting valve block 10 is installed on the opening and closing valve shaft 7. A valve column 14 is connected to the bottom of the connecting valve block. The valve column fits into the third connecting groove 313. The connecting valve block 10 fits into the inner wall of the second connecting groove 312 near the inner wall of the third connecting groove 313. An installation platform 11 is provided at the upper end of the opening and closing valve shaft 7. The sealing main pipe 1 is installed on the installation platform 11. A drive cylinder 12 is also provided on the installation platform 11. The opening and closing valve shaft 7 is connected to the output end of the drive cylinder 12.

[0075] like Figure 4 As shown, the drive cylinder 12 drives the opening and closing valve shaft 7 to move upward, which in turn drives the connecting valve block 10 to move upward, so that the connecting valve block 10 and the valve column 14 move upward together to be close to the first connecting groove 311. After moving upward a certain distance, the valve column 14 disengages from the third connecting groove 313. At this time, the inside of the drain trough 31 is in a connected state, and seawater can enter the drain trough 31 from the water injection chamber 26. At the same time, the grid plate 233 supports the floating plate 231, and the sealing block 24 moves away from the water injection hole 22.

[0076] The horizontal tube assembly 4 is used to inject carbon dioxide into the compound layer. The horizontal tube assembly 4 adopts the following preferred embodiment: the horizontal tube assembly 4 includes a connecting outer tube 41 and a connecting inner tube 42; the connecting inner tube 42 is connected to the bottom of the sealing main tube 1, the sealing main tube 1 passes through the connecting outer tube 41, and the side wall of the connecting inner tube 42 is provided with a plurality of vent holes 43, the straight line where the vent holes 43 are located is offset from the straight line where the output channel 6 is located.

[0077] In this invention, carbon dioxide enters the inner connecting pipe 42 and is discharged into the outer connecting pipe 41 through the vent 43. The outer connecting pipe 41 is filled with seawater, and some of the carbon dioxide dissolves inside the outer connecting pipe 41. After dissolving in the water, the carbon dioxide is discharged from the output channel 6 with the water flow and flows outward in a diffused state.

[0078] The discharge pipe 3 is used to discharge seawater containing dissolved carbon dioxide. The discharge pipe 3 adopts the following preferred embodiment: the discharge pipe 3 includes a connecting branch pipe 32 connected to the ventilation chamber 21, a water inlet 33 provided on the connecting branch pipe 32, an opening and closing valve shaft 7 passing through the connecting branch pipe 32, the connecting branch pipe 32 communicating with the third connecting groove 313, and a horizontal discharge pipe 8 connected to the end of the connecting branch pipe 32.

[0079] Seawater containing dissolved carbon dioxide enters the connecting branch pipe 32 from the discharge channel 31 and then enters the next water injection chamber 26 through the water injection hole 22. After that, it enters the connecting branch pipe 32 through the discharge channel 31 and flows down to the horizontal discharge pipe 8. The seawater containing dissolved carbon dioxide is discharged to the hydrate layer from the drainage channel 9.

[0080] In order to prevent water from being injected into the water injection chamber 26 during the drainage process, the present invention also makes the following design: the part of the opening and closing valve shaft 7 connected to the branch pipe 32 is connected to a sliding valve block 13, and the sliding valve block 13 abuts against the water inlet 33.

[0081] like Figure 3 As shown, in the initial state, the sliding valve block 13 abuts against the water inlet 33. During the process of seawater being discharged from the water injection chamber 26, as... Figure 4 As shown, the opening / closing valve shaft 7 moves upward, the drain trough 31 opens, and the water injection hole 22 opens. At this time, seawater in the previous ventilation chamber 21 can enter the current ventilation chamber 21 through the connecting branch pipe 32. However, during the upward movement, the sliding valve block 13 always blocks the water delivery hole 33. After the seawater is discharged, as shown... Figure 5 and Figure 6 As shown, the valve shaft 7 moves downward, and after moving a certain distance, the connecting valve block 10 and the valve column 14 are completely engaged in the second connecting groove 312 and the third connecting groove 313. At this time, the sliding valve block 13 does not block the water inlet 33, and the blocking block 24 does not block the water inlet 22. Seawater enters the water inlet 22 from the water inlet 33 and thus enters the water inlet chamber 26.

[0082] In order to ensure that the connecting valve block 10 and valve column 14 block the drain groove 31 and the sliding valve block 13 blocks the water inlet 33 in the initial state, and that the sliding valve block 13 can continue to move downwards during the subsequent downward movement, in the initial state, the connecting valve block 10 is away from the second connecting groove 312, but the valve column 14 is in the third connecting groove 313, such as... Figure 5As shown, at this time, the valve column 14 blocks the drain groove 31, and the sliding valve block 13 blocks the water inlet 33. During the subsequent downward movement, the connecting valve block 10 completely fits the second connecting groove 312, as shown. Figure 6 As shown, the sliding valve block 13 moves down away from the conveying hole 33, so that the conveying hole 33 is in the open state.

[0083] In summary, the main implementation process of this invention is as follows:

[0084] Carbon dioxide is injected into the main sealing pipe 1. The carbon dioxide enters the bottom of the water injection chamber 26 through the first ventilation channel 25 and the first connecting cylinder 28. It then rises from the bottom of the seawater to the top of the water injection chamber 26 and is discharged through the second connecting cylinder 29 and the second ventilation channel 27. Some carbon dioxide dissolves in the water injection chamber 26. The remaining carbon dioxide passes through several water injection chambers 26 in sequence and enters the horizontal pipe assembly 4 from the bottom of the main sealing pipe 1.

[0085] After carbon dioxide enters the inner connecting pipe 42, it is discharged into the outer connecting pipe 41 through the vent 43. Some of the carbon dioxide dissolves in the outer connecting pipe 41. The dissolved carbon dioxide and the undissolved carbon dioxide are discharged from the outlet channel 6 with the water flow and flow outward to the hydrate layer in a diffused state.

[0086] The drive cylinder 12 drives the opening and closing valve shaft 7 to move upward, which in turn drives the connecting valve block 10 to move upward, so that the connecting valve block 10 and the valve column 14 move upward together to be close to the first connecting groove 311. After moving upward a certain distance, the valve column 14 disengages from the third connecting groove 313. At this time, the inside of the drain trough 31 is in a connected state, and the mesh plate 233 moves upward along with it to support the floating plate 231, so that the sealing block 24 is away from the upper water injection hole 22 and the lower drain trough 31, and the water injection hole 22 is in an open state.

[0087] Seawater in the water injection chamber 26 can enter the discharge trough 31 from the water injection chamber 26. After the seawater containing dissolved carbon dioxide enters the connecting branch pipe 32 from the discharge trough 31, it enters the next water injection chamber 26 through the water injection hole 22. Then it enters the connecting branch pipe 32 through the discharge trough 31 and flows down to the horizontal discharge pipe 8 after passing through the above-mentioned water injection chambers 26. The seawater containing dissolved carbon dioxide is discharged to the hydrate layer from the drainage trough 9.

[0088] After the seawater containing dissolved carbon dioxide is discharged, it drives the opening and closing valve shaft 7 to move downward. After moving downward a certain distance, the connecting valve block 10 and the valve column 14 are completely fitted into the second connecting groove 312 and the third connecting groove 313. At this time, the sliding valve block 13 does not block the water inlet 33, and the sealing block 24 does not block the water inlet 22. The seawater enters the water inlet 22 from the water inlet 33 and then enters the water inlet chamber 26. After injecting a certain amount of seawater, the opening and closing valve shaft 7 moves upward so that the valve column 14 can just block the third connecting groove 313. The float plate 231 floats on the liquid surface, and the sealing block 24 blocks the water inlet 22.

[0089] The present invention also provides a method for storing carbon dioxide in a waste natural gas hydrate reservoir, comprising the following steps:

[0090] Step 100: The horizontal pipe assembly 4 and the main sealing pipe 1 are vertically lowered into the ocean, with the horizontal pipe assembly 4 extending to the hydrate layer.

[0091] Step 200: Inject seawater of the corresponding height into the ventilation chamber 21 through the water injection hole 22, and block the passage for seawater to enter the ventilation chamber 21 through the opening and closing valve shaft 7.

[0092] Step 300: Carbon dioxide gas is introduced into the sealing main pipe 1. Part of the carbon dioxide gas dissolves in water through the ventilation chamber 21, and the remaining carbon dioxide gas is discharged to the hydrate layer through the ventilation chamber 21 and the horizontal pipe assembly 4.

[0093] Step 400: Open the drain trough 31 and water injection hole 22 through the opening and closing valve shaft 7, and water containing dissolved carbon dioxide gas is injected into the hydrate layer through the drain trough 31 and horizontal drain pipe 8.

[0094] Step 500: Close the drain trough 31 by opening and closing valve shaft 7, and open the channel for seawater to enter the ventilation chamber 21. Repeat steps 200, 300, 400 and 500.

[0095] In practical applications, extraction wells can be set up at appropriate locations to extract methane that has been replaced by carbon dioxide and methane hydrate.

[0096] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. An apparatus for sequestration of carbon dioxide in a depleted natural gas hydrate reservoir, comprising: have: A sealing main pipe (1) is installed at its bottom with a horizontal pipe assembly (4). The horizontal pipe assembly (4) is vertically installed on the sealing main pipe (1). The sealing main pipe (1) is connected to the horizontal pipe assembly (4). The bottom end of the sealing main pipe (1) extends to below the hydrate layer. The horizontal pipe assembly (4) is disposed in the hydrate layer. The horizontal pipe assembly (4) has a plurality of dispersion holes (5) formed around its circumference. The dispersion holes (5) are used to inject carbon dioxide into the hydrate layer. An output channel (6) for carbon dioxide injection is formed in the dispersion holes (5). The extension line of the straight line where the output channel (6) is located is directly opposite the central axis inside the horizontal pipe assembly (4). Dissolving branch pipes (2) are installed at equal intervals on the sealing main pipe (1). The dissolving branch pipes (2) form a plurality of ventilation chambers (21). The interior of the ventilation chambers (21) is connected to the interior of the sealing main pipe (1). A water injection hole (22) is provided at the top of the ventilation chamber (21). The water injection hole (22) injects seawater into the ventilation chamber (21). A floating component (23) is provided in the ventilation chamber (21). A sealing block (24) is installed on the floating component (23). The sealing block (24) is connected to the water injection hole (22). A discharge pipe (3) is installed through the ventilation chamber (21) and away from the main sealing pipe (1). The discharge pipe (3) has a discharge groove (31) formed at the penetration point of the bottom wall of the ventilation chamber (21). An opening and closing valve shaft (7) is installed inside the discharge pipe (3). The opening and closing valve shaft (7) moves up and down to block the discharge groove (31). A horizontal drain pipe (8) is vertically located at the bottom of the drain pipe fitting (3). The drain pipe fitting (3) is connected to the center of the horizontal drain pipe (8). The horizontal drain pipe (8) is provided with several drainage grooves (9) around its circumference. The height of the horizontal drain pipe (8) is higher than the height of the horizontal pipe assembly (4). The ventilation chamber (21) is provided with a first ventilation channel (25), a water injection chamber (26), and a second ventilation channel (27), which are connected in sequence. The first ventilation channel (25) is connected to the inside of the sealing main pipe (1) at one end and connected to the side of the water injection chamber (26) at the other end. The second ventilation channel (27) is connected to the side of the water injection chamber (26) at one end and connected to the inside of the sealing main pipe (1) at the other end.

2. The carbon dioxide sequestration device for waste natural gas hydrate reservoirs according to claim 1, characterized in that, A first connecting cylinder (28) is installed on one side wall of the water injection chamber (26), and a second connecting cylinder (29) is installed on the other side wall. The first connecting cylinder (28) is connected to the first ventilation channel (25), and the second connecting cylinder (29) is connected to the second ventilation channel (27). The first connecting cylinder (28) and the second connecting cylinder (29) are both vertically installed on the inner wall of the water injection cavity (26). The first connecting cylinder (28) is close to the bottom of the water injection cavity (26), and the second connecting cylinder (29) is close to the top of the water injection cavity (26).

3. The carbon dioxide sequestration device for abandoned natural gas hydrate reservoirs according to claim 2, characterized in that, The floating component (23) includes a floating disk (231) disposed in the ventilation chamber (21) and a through groove (232) disposed at the center of the floating disk (231). The sealing block (24) is connected to the upper end of the floating plate (231), and the opening and closing valve shaft (7) is disposed through the through groove (232). The opening and closing valve shaft (7) passes through the water injection hole (22) and the sealing block (24). The outer diameter of the opening and closing valve shaft (7) is the same as the inner diameter of the through groove (232), and the outer diameter of the opening and closing valve shaft (7) is smaller than the inner diameter of the water injection hole (22).

4. The carbon dioxide sequestration device for abandoned natural gas hydrate reservoirs according to claim 3, characterized in that, Both the sealing block (24) and the water injection hole (22) are configured as frustum shapes; A mesh plate (233) is provided on the opening and closing valve shaft (7), and the mesh plate (233) abuts against the floating plate (231); The thickness of the floating plate (231) is greater than the inner diameter of the second connecting cylinder (29).

5. The carbon dioxide sequestration device for abandoned natural gas hydrate reservoirs according to claim 4, characterized in that, The groove (31) is connected in sequence by a first connecting groove (311), a second connecting groove (312) and a third connecting groove (313); The inner diameter of the first connecting groove (311) is larger than the inner diameter of the third connecting groove (313), and the bottom inner diameter of the second connecting groove (312) is smaller than the top inner diameter of the second connecting groove (312).

6. The carbon dioxide sequestration device for abandoned natural gas hydrate reservoirs according to claim 5, characterized in that, A connecting valve block (10) is installed on the opening and closing valve shaft (7). A valve column (14) is connected to the bottom of the connecting valve block (10). The valve column (14) fits into the third connecting groove (313). The connecting valve block (10) fits into the inner wall of the second connecting groove (312) near the inner wall of the third connecting groove (313). An installation platform (11) is provided on the upper end of the opening and closing valve shaft (7). The sealing main pipe (1) is installed on the installation platform (11). A drive cylinder (12) is also provided on the installation platform (11). The opening and closing valve shaft (7) is connected to the output end of the drive cylinder (12).

7. The carbon dioxide sequestration device for abandoned natural gas hydrate reservoirs according to claim 6, characterized in that, The horizontal pipe assembly (4) includes an outer pipe (41) and an inner pipe (42). The inner connecting tube (42) is connected to the bottom of the main sealing tube (1), the main sealing tube (1) passes through the outer connecting tube (41), and the inner connecting tube (42) has several exhaust holes (43) on its side wall. The straight line of the exhaust holes (43) is offset from the straight line of the output channel (6).

8. The carbon dioxide sequestration device for abandoned natural gas hydrate reservoirs according to claim 7, characterized in that, The discharge pipe (3) includes a connecting branch pipe (32) connected to the ventilation chamber (21) and a water inlet (33) provided on the connecting branch pipe (32). The opening and closing valve shaft (7) passes through the connecting branch pipe (32), the connecting branch pipe (32) is connected to the third connecting groove (313), the horizontal pipe (8) is connected to the end of the connecting branch pipe (32), and the opening and closing valve shaft (7) is connected to a sliding valve block (13) corresponding to the part inside the connecting branch pipe (32), and the sliding valve block (13) abuts against the water inlet (33).

9. A method for storing carbon dioxide in a waste natural gas hydrate reservoir according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step 100: The horizontal pipe assembly and the main storage pipe are vertically lowered into the ocean, with the horizontal pipe assembly extending to the hydrate layer; Step 200: Inject seawater of the corresponding height into the ventilation chamber through the water injection hole, and block the passage for seawater to enter the ventilation chamber by opening and closing the valve shaft. Step 300: Carbon dioxide gas is introduced into the main sealing pipe. Part of the carbon dioxide gas dissolves in water through the ventilation chamber, and the remaining carbon dioxide gas is discharged to the hydrate layer through the ventilation chamber and the horizontal pipe assembly. Step 400: Open the drain trough and water injection hole through the opening and closing valve shaft, and water containing dissolved carbon dioxide gas is injected into the hydrate layer through the drain trough and horizontal pipe. Step 500: Close the drain trough by opening and closing the valve shaft, and open the channel for seawater to enter the ventilation chamber. Repeat steps 200, 300, 400 and 500.

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