A method of arranging a coal seam hydrogen reservoir

Abstract

The application discloses a coal seam hydrogen storage arrangement method, and belongs to the technical field of geological hydrogen storage. Firstly, a hydrogen storage construction target area is selected in a low-permeability and dense coal seam of a roof and floor, and a plurality of horizontal wells in three layers are built from outside to inside in the area; aiming at the multi-scale characteristics of the coal seam pore and fissure, annular anti-permeation reinforcement zones for plugging macroscopic fissure structures and reinforcing the coal seam are formed by drilling and injecting superfine high-permeability cement slurry in the outermost layer of the horizontal wells; then, annular saturated water sealing zones for sealing microcosmic pore structures are formed by injecting water in the middle layer of the horizontal wells, and the sealing of hydrogen is guaranteed under a certain pressure by adjusting the pressure of the saturated water; finally, hydrogen injection and extraction are implemented in the hydrogen storage area, so that hydrogen is stored in the coal seam pore and fissure network in the form of adsorption and free states on a large scale; and the application solves the problems of great difficulty in the excavation construction of underground hydrogen storage space and the monitoring and maintenance of surrounding rock stability.

Description

Technical Field

[0001] The invention belongs to the technical field of geological hydrogen storage and relates to a coal seam hydrogen storage arrangement method. Background Art

[0002] Hydrogen storage technology is crucial for the widespread use of hydrogen energy. It can address the storage and transportation issues of hydrogen energy, promote the widespread use of clean energy, and thus reduce dependence on fossil fuels, helping to address climate change and improve the sustainability of energy systems. Currently, most publicly available hydrogen storage technologies use ground-based tank storage or storage in confined underground structures. Ground-based tank storage has technical disadvantages such as limited hydrogen storage capacity, high safety risks, low energy efficiency, and high hydrogen storage costs. Using underground structures such as abandoned coal mine tunnels (CN116201599A) or hydrogen storage caverns (CN219139138U) to store hydrogen reduces the risk of ground hydrogen leaks and explosions, but still faces high costs for excavation and construction of underground structures, monitoring and maintaining surrounding rock stability, and the difficulty of developing long-term pressure-resistant sealing technology for the lining, making large-scale, long-term hydrogen storage difficult. Summary of the Invention

[0003] The present invention overcomes the shortcomings of the existing technology and proposes a coal seam hydrogen storage arrangement method to solve the problems of difficulty in excavation and construction of underground hydrogen storage space and monitoring and maintenance of surrounding rock stability.

[0004] In order to achieve the above object, the present invention is implemented through the following technical solutions.

[0005] A method for arranging a coal seam hydrogen storage reservoir comprises the following steps:

[0006] 1) Select the coal seam area as the coal seam hydrogen storage construction area;

[0007] 2) Arrange multiple horizontal wells adjacent to each other as grouting wells inside the boundary of the coal seam hydrogen storage construction area, arrange multiple horizontal wells adjacent to each other as water injection wells inside the multiple grouting wells, arrange multiple horizontal wells adjacent to each other as hydrogen extraction wells inside the multiple water injection wells, and set up hydrogen injection wells in the area surrounded by the multiple hydrogen extraction wells;

[0008] 3) Inject cement slurry into the grouting well. After the cement slurry solidifies, a closed annular grouting anti-seepage reinforcement belt with a radial short axis equal to the coal seam thickness and a long axis ≥ 2 times the coal seam thickness is formed around the horizontal grouting borehole to seal the macro-fracture structure and reinforce the coal seam.

[0009] 4) Inject water into the injection well to saturate the coal body around the horizontal water injection borehole, forming a closed annular water-saturated sealing zone with a radial minor axis equal to the coal seam thickness and a major axis ≥ 3 times the coal seam thickness to seal the microscopic pore structure. The area surrounded by the closed annular water-saturated sealing zone is the hydrogen storage area;

[0010] 5) Inject hydrogen from the hydrogen injection well so that hydrogen is stored in the coal seam in both adsorbed and free states. At the same time, extract hydrogen from the hydrogen extraction well and monitor the extracted hydrogen concentration until the hydrogen concentration reaches the target value. The coal seam hydrogen storage is then arranged.

[0011] Preferably, the roof and floor of the coal seam region selected as the coal seam hydrogen storage construction area are dense low-permeability structures with a permeability lower than 0.1 mD, and the horizontal inclination angle of the coal seam region is less than 8°.

[0012] Preferably, the coal seam hydrogen storage construction area is a triangular area.

[0013] More preferably, three grouting wells are set inside the boundary of the triangular area, three water injection wells are set inside the three grouting wells, three hydrogen extraction wells are set inside the three water injection wells, and a hydrogen injection well is set in the center of the triangular area.

[0014] Preferably, the horizontal well is an L-shaped horizontal well; and the vertical wellbore of the L-shaped horizontal well is sealed.

[0015] Preferably, the hydrogen injection well is a vertical well, and the wellbore of the hydrogen injection well is sealed.

[0016] Preferably, the target value in step 5) refers to the value at which the hydrogen concentration reaches the required value for utilization after the injected hydrogen gradually displaces the original gas in the coal seam during hydrogen storage.

[0017] Preferably, during the operation of the reservoir, the water pressure of the closed annular saturated sealing zone is dynamically adjusted in real time by injecting and discharging water from the water injection well according to the hydrogen pressure distribution in the hydrogen storage area and the water vapor permeability of the coal seam, to ensure that during the operation of the reservoir, hydrogen will not be driven out of the reservoir due to excessively low water pressure, causing water leakage, and that water will not be discharged from the hydrogen extraction well due to excessive water pressure.

[0018] Preferably, during the operation of the reservoir, the pressure of water or hydrogen injection into the coal seam is lower than the cracking pressure of the coal seam roof and floor plates and the coal body in the grouting anti-seepage reinforcement zone, so as to prevent the coal seam roof and floor plates and the coal body in the grouting anti-seepage reinforcement zone from being fractured or damaged.

[0019] The beneficial effects of the present invention compared to the prior art are:

[0020] The present invention uses grouting and water injection of L-shaped horizontal wells arranged in a triangular plane to form an annular anti-seepage reinforcement belt for sealing macro-fracture structures and reinforcing coal seams, as well as an annular water-saturated sealing belt for sealing micro-pore structures with a minimum number of drilling operations, thereby ensuring the airtightness of the hydrogen storage reservoir. By cleverly utilizing the porous medium characteristics of the coal body and its adsorption capacity for methane, large amounts of hydrogen can be stored in adsorbed and free states in the pore and fracture network of the coal seam. Compared with the hydrogen storage technology in enclosed spaces of underground structures, the present invention avoids the difficulties of space excavation and construction, surrounding rock stability monitoring and maintenance, and long-term pressure-resistant sealing monitoring and maintenance of the inner lining, greatly reducing the maintenance cost during the operation of the reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of coal seam hydrogen storage area selection and grouting well construction; (1a) is a three-dimensional schematic diagram, and (1b) is a cross-sectional view of aa' in Figure (1a);

[0022] Figure 2 is a schematic diagram of water injection well construction; wherein, (2a) is a three-dimensional schematic diagram, and (2b) is a cross-sectional view of aa' in Figure (2a);

[0023] Figure 3 Schematic diagram of hydrogen injection and extraction well construction; wherein, (3a) is a three-dimensional schematic diagram, and (3b) is a cross-sectional view of aa' in Figure (3a);

[0024] Figure 4 Schematic diagram of grouting to form a closed ring grouting anti-seepage reinforcement belt; wherein, (4a) is a three-dimensional schematic diagram, and (4b) is a cross-sectional view of aa' in Figure (4a);

[0025] Figure 5 It is a schematic diagram of a closed annular water-saturated sealing zone formed by water injection; wherein, (5a) is a three-dimensional schematic diagram, and (5b) is a cross-sectional view of aa' in Figure (5a);

[0026] Figure 6 Schematic diagram of hydrogen injection and extraction in coal seams; wherein (6a) is a three-dimensional schematic diagram, and (6b) is a cross-sectional view of aa' in Figure (6a);

[0027] Among them: 1-coal seam hydrogen storage construction area, 2-first grouting well, 3-second grouting well, 4-third grouting well, 5-first water injection well, 6-second water injection well, 7-third water injection well, 8-first hydrogen extraction well, 9-second hydrogen extraction well, 10-third hydrogen extraction well, 11-hydrogen injection well, 12-closed annular grouting anti-seepage reinforcement belt, 13-closed annular saturated water sealing belt, 14-hydrogen storage area. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. The technical solutions of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0029] A nearly horizontal coal seam has a burial depth of 400m and a thickness of 4m, and its top and bottom plates are both low-permeability and dense mudstone layers. A hydrogen storage reservoir is arranged in the coal seam using the method of the present invention.

[0030] The specific steps are as follows:

[0031] 1. If Figure 1 As shown, a triangular area with a side length of 400m and good integrity of the top and bottom of the coal seam is selected as the coal seam hydrogen storage construction area 1.

[0032] 2. 5 meters inside the three boundaries of the coal seam hydrogen storage construction area 1, three L-shaped horizontal wells with a length of 390 meters are constructed in sequence in the middle of the coal seam parallel to the boundaries of the area, and the vertical wellbore is sealed. These are the first grouting well 2, the second grouting well 3, and the third grouting well 4;

[0033] 3. If Figure 2 As shown, 12 meters inside the triangular area enclosed by the first grouting well 2, the second grouting well 3, and the third grouting well 4, three L-shaped horizontal wells with a length of 370 meters are successively constructed in the middle of the coal seam in parallel with the first grouting well 2, the second grouting well 3, and the third grouting well 4, and the vertical wellbore is sealed to serve as the first water injection well 5, the second water injection well 6, and the third water injection well 7;

[0034] 4. If Figure 3 As shown, 7 meters inside the triangular area enclosed by the already constructed first water injection well 5, second water injection well 6, and third water injection well 7, three L-shaped horizontal wells with a length of 355 meters are sequentially constructed in the middle of the coal seam, parallel to the L-shaped first water injection well 5, second water injection well 6, and third water injection well 7, and the vertical wellbores are sealed to serve as the first hydrogen extraction well 8, the second hydrogen extraction well 9, and the third hydrogen extraction well 10; a vertical well is constructed in the center of the coal seam hydrogen storage construction area 1, and the wellbores are sealed to serve as the hydrogen injection well 11;

[0035] 5. If Figure 4 As shown, high-permeability ultrafine cement slurry is injected into the first grouting well 2, the second grouting well 3, and the third grouting well 4 under high pressure. After the cement slurry solidifies, a closed annular grouting anti-seepage reinforcement belt 12 with a radial short axis of 4 meters and a long axis of about 10 meters is formed around the horizontal grouting borehole.

[0036] 6. If Figure 5As shown, water is injected into the first water injection well 5, the second water injection well 6, and the third water injection well 7. The coal body around the horizontal water injection borehole reaches a water-saturated state under a certain pressure, forming a closed annular water-saturated sealing belt 13 with a height of 4 meters and a width of about 14 meters. The area surrounded by the closed annular water-saturated sealing belt 13 is the hydrogen storage area 14.

[0037] 7. If Figure 6 As shown, hydrogen is injected from hydrogen injection well 11, while hydrogen is extracted from first hydrogen extraction well 8, second hydrogen extraction well 9, and third hydrogen extraction well 10. The extracted hydrogen concentration is monitored until it reaches the target value, completing the coal seam hydrogen storage arrangement. The target value is the concentration required for hydrogen utilization, and different utilization methods require different concentrations. During hydrogen storage, the injected hydrogen gradually displaces the original gas in the coal seam. Only after the displacement is substantially complete does the hydrogen concentration reach the value required for utilization, at which point a large amount of hydrogen has been stored in the coal seam.

[0038] During the operation of the reservoir, the water pressure of the closed annular saturated sealing belt 13 is dynamically adjusted in real time through the injection and discharge of water from the first water injection well 5, the second water injection well 6, and the third water injection well 7 according to the hydrogen pressure distribution in the hydrogen storage area 14 and the water vapor permeability of the coal seam, to ensure that during the operation of the reservoir, hydrogen will not be driven out of the reservoir due to excessively low water pressure, causing water leakage, and at the same time, water will not be discharged from the first hydrogen extraction well 8, the second hydrogen extraction well 9, and the third hydrogen extraction well 10 due to excessive water pressure.

[0039] Specifically, the water pressure in the saturated sealing zone is adjusted by injecting and discharging water from the first water injection well 5, the second water injection well 6, and the third water injection well 7. The appropriate water pressure should satisfy formula (1), and the pressure of the coal seam water injection or hydrogen injection should be lower than the fracture pressure of the coal seam roof and floor plates and the coal body of the grouting anti-permeability reinforcement zone. This ensures that during the operation of the reservoir, hydrogen will not leak out of the reservoir due to excessive water pressure, and that water will not be discharged from the first hydrogen extraction well 8, the second hydrogen extraction well 9, and the third hydrogen extraction well 10 due to excessive water pressure.

[0040]

[0041] In formula (1), P w is the water pressure at the boundary between the saturated sealing zone and the hydrogen storage area, P H is the hydrogen pressure at the boundary between the saturated sealing zone and the hydrogen storage area, P m is the capillary pressure of the pore water-gas interface at the boundary between the saturated sealing zone and the hydrogen storage area.

[0042] Furthermore, during the operation of the reservoir, the pressure of water or hydrogen injection into the coal seam should be lower than the cracking pressure of the coal seam roof and floor plates and the coal body in the grouting anti-seepage reinforcement zone, so as to ensure that it does not cause cracking damage to the coal seam roof and floor plates and the coal body in the grouting anti-seepage reinforcement zone.

[0043] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be considered that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the present invention, which should be regarded as belonging to the scope of patent protection determined by the submitted claims of the present invention.

Claims

1. A coal seam hydrogen storage arrangement method, characterized in that: The following steps are involved: 1) Select the coal seam area as the coal seam hydrogen storage area (1); 2) Arrange multiple horizontal wells adjacent to each other as grouting wells inside the boundary of the coal seam hydrogen storage construction area (1), arrange multiple horizontal wells adjacent to each other as water injection wells inside the multiple grouting wells, arrange multiple horizontal wells adjacent to each other as hydrogen extraction wells inside the multiple water injection wells, and set up hydrogen injection wells (11) in the area surrounded by the multiple hydrogen extraction wells; 3) Inject cement slurry into the grouting well, and after the cement slurry solidifies, form a closed annular grouting anti-seepage reinforcement belt (12) around the horizontal grouting borehole, with the radial short axis of the cross section equal to the thickness of the coal seam and the long axis ≥ 2 times the thickness of the coal seam, for sealing the macro-fracture structure and reinforcing the coal seam; 4) Inject water into the water injection well to make the coal body around the horizontal water injection borehole reach a water saturated state, forming a closed annular water-saturated sealing belt (13) with a radial short axis equal to the thickness of the coal seam and a long axis ≥ 3 times the thickness of the coal seam for sealing the microscopic pore structure. The area surrounded by the closed annular water-saturated sealing belt (13) is the hydrogen storage area (14); during the operation of the reservoir, according to the hydrogen pressure distribution in the hydrogen storage area (14) and the water vapor permeability of the coal seam, the water pressure of the closed annular water-saturated sealing belt (13) is dynamically adjusted in real time by water injection and discharge from the water injection well to ensure that hydrogen will not leak out of the reservoir due to too low water pressure during operation, and that water will not be discharged from the hydrogen extraction well due to too high water pressure; 5) Inject hydrogen from the hydrogen injection well (11) so that hydrogen is stored in the coal seam in both adsorbed and free states. At the same time, extract hydrogen from the hydrogen extraction well and monitor the extracted hydrogen concentration until the hydrogen concentration reaches the target value. The coal seam hydrogen storage is then arranged.

2. A coal seam hydrogen storage arrangement method according to claim 1, characterized in that: The top and bottom plates of the coal seam area selected as the coal seam hydrogen storage construction area (1) are dense low-permeability structures with a permeability of less than 0.1 mD, and the horizontal inclination of the coal seam area is less than 8°.

3. The method for arranging a coal seam hydrogen storage according to claim 1, characterized in that: The coal seam hydrogen storage construction area (1) is a triangular area.

4. A coal seam hydrogen storage arrangement method according to claim 3, characterized in that: Three grouting wells are set inside the boundary of the triangular area, three water injection wells are set inside the three grouting wells, three hydrogen extraction wells are set inside the three water injection wells, and a hydrogen injection well is set in the center of the triangular area.

5. The method for arranging a coal seam hydrogen storage according to claim 1, characterized in that: The horizontal well is an L-shaped horizontal well; and the vertical wellbore of the L-shaped horizontal well is sealed.

6. The method for arranging a coal seam hydrogen storage according to claim 1, characterized in that: The hydrogen injection well is a vertical well, and the wellbore of the hydrogen injection well is sealed.

7. The method for arranging a coal seam hydrogen storage according to claim 1, characterized in that: The target value in step 5) refers to the value at which the hydrogen concentration reaches the required value for utilization after the injected hydrogen gradually displaces the original gas in the coal seam during hydrogen storage.

8. The method for arranging a coal seam hydrogen storage facility according to claim 1, wherein: During the operation of the reservoir, the pressure of water or hydrogen injection into the coal seam is lower than the cracking pressure of the coal seam roof and floor plates and the coal body in the grouting anti-seepage reinforcement zone, so that no cracking damage occurs to the coal seam roof and floor plates and the coal body in the grouting anti-seepage reinforcement zone.

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