Injection well system for sealing and storing carbon dioxide in seabed sedimentary layer and sealing and storing method

Abstract

The invention provides an injection well system for sealing and storing carbon dioxide on a seabed sedimentary layer and a sealing and storing method. The injection well system comprises an underwater blowout preventer and an injection main well which is arranged below the underwater blowout preventer and provided with a seabed monitoring unit. The injection main well penetrates through a deposition layer and then sequentially extends out of a first horizontal branch well from a hydrate stabilizing layer, extends out of a second horizontal branch well from a salt water layer and extends out of a third horizontal branch well from an oil and gas layer. And a CO2 conveying unit is arranged at an inlet of the injection main well. According to the injection well system and the sealing method, carbon dioxide injection of a hydrate stable layer, a salt water layer and an oil and gas layer is achieved at the same time through one injection well, the problems that at present, the offshore carbon dioxide sealing capacity is limited, and cost is high are solved, well drilling and operation cost is effectively reduced, and economic benefits are increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide storage, and in particular relates to an injection well system and a storage method for storing carbon dioxide in a seabed sediment layer. Background Art

[0003] In order to reduce carbon dioxide emissions, carbon capture and storage (CCUS) technology must be implemented, so CCUS technology has become an essential way to save energy and reduce emissions. This technology is being applied in various ways around the world and has achieved significant reductions in carbon dioxide emissions. This technology has three main processes: (1) capturing carbon dioxide from large emission point sources; (2) compressing and transporting the captured carbon dioxide; and (3) injecting and storing the captured carbon dioxide at a storage site. The storage process of CCUS technology involves a variety of storage technologies, among which marine storage has become a research hotspot in recent years due to its many advantages.

[0004] However, current research mainly focuses on the storage of carbon dioxide gas in single vertical wells. This storage method generally uses saline layers as the main storage site, but ignores the huge potential of hydrate layers and oil and gas layers to store carbon dioxide. When carbon dioxide is injected into shallow hydrate layers, the high-density hydrates generated can act as a cap layer to prevent the carbon dioxide below from further floating up and leaking into the seawater. At the same time, exploration practices in existing areas have shown the existence of vertically coexisting hydrate layers, saline layers, and oil and gas layers. These three reservoirs have good carbon dioxide storage potential and are therefore worthy of in-depth study. However, there is currently too little research on the above problems, which limits the further development of marine storage technology.

[0005] In summary, it is necessary to provide a well system and method for jointly storing carbon dioxide in hydrate layers, saline layers and oil and gas layers to solve the problem of limited offshore carbon dioxide storage capacity and high cost, and to achieve low-cost storage of offshore carbon dioxide. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an injection well system and a storage method for storing carbon dioxide in a submarine sediment layer. The injection well system and the storage method provided by the present invention can simultaneously inject carbon dioxide into the hydrate stable layer, the saline layer and the oil and gas layer through one injection well, solving the current problem of limited offshore carbon dioxide storage capacity and high cost, effectively reducing drilling and operation costs, and increasing economic benefits.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides an injection well system for storing carbon dioxide in a submarine sediment layer, the injection well system comprising an underwater blowout preventer, and an injection main well with a submarine monitoring unit disposed below the underwater blowout preventer;

[0009] After the injection main well passes through the sedimentary layer, a first horizontal branch well is extended in the hydrate stable layer, a second horizontal branch well is extended in the saline layer, and a third horizontal branch well is extended in the oil and gas layer.

[0010] The inlet of the main injection well is provided with a CO2 delivery unit.

[0011] In the present invention, the injection well system has a simple structure. Through one main injection well, carbon dioxide can be quickly injected into the hydrate stable layer, the saline layer and the deep oil and gas layer at the same time, thereby increasing the gas injection volume and injection rate, and realizing the rapid storage of carbon dioxide. At the same time, during the storage process, various parameters are monitored in real time through the seabed monitoring system, and the gas injection process is intelligently controlled to maintain the stability of the formation pressure, avoid the leakage of carbon dioxide, and realize safe storage.

[0012] In addition, the injection well system provided by the present invention can effectively reduce drilling and operation costs and increase economic benefits.

[0013] As a preferred technical solution of the present invention, according to the CO2 delivery direction, the CO2 delivery unit includes a CO2 delivery pipeline, a gas compression device and a wellhead multi-way valve which are connected in sequence.

[0014] Furthermore, the wellhead multi-way valve in the present invention is arranged in series with the underwater blowout preventer, and CO2 is transported by the underwater blowout preventer to the injection main well after passing through the wellhead multi-way valve.

[0015] In the present invention, the liquefaction of carbon dioxide is achieved through the gas compressor in the CO2 delivery unit, thereby further reducing the volume of carbon dioxide and improving the injection efficiency of carbon dioxide.

[0016] As a preferred technical solution of the present invention, the seabed monitoring unit is used to monitor the leakage of CO2 within a range of 1000m around the wellhead of the main injection well.

[0017] It is worth noting that the seabed monitoring unit described in the present invention can realize real-time monitoring of injection parameters in the injection well system, intelligently control the gas injection process to maintain stable formation pressure, avoid leakage of carbon dioxide, and further realize safe and efficient injection of carbon dioxide.

[0018] As a preferred technical solution of the present invention, a hydrate layer monitoring unit is provided on the side wall of the first horizontal branch well.

[0019] Preferably, the hydrate layer monitoring unit is used to monitor the pressure of the hydrate stable layer.

[0020] As a preferred technical solution of the present invention, the injection well system is arranged on the seabed.

[0021] In a second aspect, the present invention provides a method for storing carbon dioxide, which is performed using the injection well system for storing carbon dioxide in a seafloor sediment layer provided in the first aspect.

[0022] As a preferred technical solution of the present invention, the sealing method comprises the following steps:

[0023] (1) transporting liquid carbon dioxide and a carbon dioxide hydrate promoter to the first horizontal branch well through a CO2 transport unit to form a carbon dioxide hydrate cap layer in the hydrate stabilization layer;

[0024] (2) transporting liquid carbon dioxide to the second horizontal branch well and / or the third horizontal branch well through the CO2 transport unit;

[0025] (3) Perform cementing operations, and then repeat step (2) to achieve the storage of carbon dioxide.

[0026] In the present invention, in step (1), liquid carbon dioxide and a carbon dioxide hydrate promoter are transported into the first horizontal branch well, so that high-saturation carbon dioxide hydrate is generated around the first horizontal branch well, and the high-saturation carbon dioxide hydrate forms a cap layer to prevent the carbon dioxide below from floating up and leaking into the seawater, thereby realizing the storage of carbon dioxide; then, the relationship between the real-time pressure of the hydrate stable layer and the fracture pressure of the hydrate stable layer is analyzed according to the data of the hydrate layer monitoring unit, and the stop of carbon dioxide injection or the stop timing is determined;

[0027] Then, through step (2), liquid carbon dioxide is transported to the second horizontal branch well and / or the third horizontal branch well to achieve effective storage of carbon dioxide.

[0028] As a preferred technical solution of the present invention, the addition amount of the carbon dioxide hydrate promoter in step (1) is 10 to 1000 mg / L, for example, it can be 10 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 700 mg / L, 800 mg / L, 900 mg / L or 1000 mg / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the carbon dioxide hydrate promoter in step (1) comprises any one of tetrahydropyran, cyclopentane, tetrabutylammonium bromide, tetrabutylammonium fluoride or tetrabutylammonium chloride, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of tetrahydropyran and cyclopentane, a combination of tetrabutylammonium bromide, tetrabutylammonium fluoride and tetrabutylammonium chloride, or a combination of tetrahydropyran, cyclopentane, tetrabutylammonium bromide, tetrabutylammonium fluoride and tetrabutylammonium chloride.

[0030] As a preferred technical solution of the present invention, the endpoint of conveying liquid carbon dioxide in step (1) is: the hydrate stability layer pressure is 93-97% of the hydrate stability layer rupture pressure, for example, it can be 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5% or 97%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, the end point of the delivery of liquid carbon dioxide in step (2) is: leakage of carbon dioxide is monitored by the seabed monitoring unit.

[0032] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The injection well system and storage method for storing carbon dioxide in a submarine sediment layer provided by the present invention solve the current problem of limited offshore carbon dioxide storage capacity and high cost, and realize low-cost storage of offshore carbon dioxide;

[0035] (2) The injection well system for storing carbon dioxide in the seabed sediment layer provided by the present invention can simultaneously and rapidly inject carbon dioxide into the hydrate layer, the saline layer and the deep oil and gas layer, increase the gas injection volume and injection rate, and realize the rapid storage of carbon dioxide; at the same time, during the storage process, various parameters are monitored in real time by the seabed monitoring unit, and the gas injection process is intelligently controlled to maintain the stability of the formation pressure, avoid the leakage of carbon dioxide, and realize safe storage;

[0036] (3) The injection well system for storing carbon dioxide in seabed sediments provided by the present invention can realize the injection of carbon dioxide into hydrate layers, saline layers and oil and gas layers simultaneously by using one injection well, effectively reducing drilling and operation costs and increasing economic benefits;

[0037] (4) The injection well system for storing carbon dioxide in seabed sediments provided by the present invention has a simple structure and can be widely used in the field of offshore carbon dioxide storage technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of the structure of an injection well system for storing carbon dioxide in a seabed sediment provided by the present invention;

[0039] Among them, 1 is the seabed, 2 is the hydrate stability layer, 3 is the saline layer, 4 is the oil and gas layer, 5 is the underwater blowout preventer, 6 is the wellhead multi-way valve, 7 is the gas compression device, 8 is the CO2 transmission pipeline, 9 is the seabed detection unit, 10 is the first horizontal branch well, 11 is the second horizontal branch well, 12 is the third horizontal branch well, and 13 is the hydrate layer monitoring unit. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0041] In one embodiment, the present invention provides an injection well system for storing carbon dioxide in a seafloor sediment layer, such as Figure 1 As shown, the injection well system includes an underwater blowout preventer 5, and an injection main well with a seabed monitoring unit 9 disposed below the underwater blowout preventer 5;

[0042] After the injection main well passes through the sedimentary layer, a first horizontal branch well 10 is extended in the hydrate stabilization layer 2, a second horizontal branch well 11 is extended in the saline layer 3, and a third horizontal branch well 12 is extended in the oil and gas layer 4.

[0043] The inlet of the main injection well is provided with a CO2 delivery unit.

[0044] According to the CO2 delivery direction, the CO2 delivery unit includes a CO2 delivery pipeline 8, a gas compression device 7 and a wellhead multi-way valve 6 which are connected in sequence;

[0045] The seabed monitoring unit 9 is used to monitor the leakage of CO2 within 1000m around the wellhead of the injection main well; the side wall of the first horizontal branch well 10 is provided with a hydrate layer monitoring unit 13; the hydrate layer monitoring unit 13 is used to monitor the pressure of the hydrate stable layer 2;

[0046] The injection well system is arranged on the seabed 1 .

[0047] In another specific embodiment, the present invention provides a method for storing carbon dioxide using the above injection well system, the method comprising the following steps:

[0048] (1) delivering liquid carbon dioxide and a carbon dioxide hydrate promoter to the first horizontal branch well by a CO2 delivery unit until the pressure of the hydrate stability layer is 93-97% of the fracture pressure of the hydrate stability layer, thereby forming a carbon dioxide hydrate cap layer in the hydrate stability layer;

[0049] Wherein, the addition amount of the carbon dioxide hydrate promoter is 10 to 1000 mg / L;

[0050] (2) delivering liquid carbon dioxide to the second horizontal branch well and / or the third horizontal branch well through the CO2 delivery unit until the seabed monitoring unit detects leakage of carbon dioxide;

[0051] (3) Perform cementing operations, and then repeat step (2) to achieve the storage of carbon dioxide.

[0052] Example 1

[0053] This embodiment provides an injection well system for storing carbon dioxide in a seafloor sediment layer, such as Figure 1 As shown, the injection well system includes an underwater blowout preventer 5, and an injection main well with a seabed monitoring unit 9 disposed below the underwater blowout preventer 5;

[0054] After the injection main well passes through the sedimentary layer, a first horizontal branch well 10 is extended in the hydrate stabilization layer 2, a second horizontal branch well 11 is extended in the saline layer 3, and a third horizontal branch well 12 is extended in the oil and gas layer 4.

[0055] The inlet of the main injection well is provided with a CO2 delivery unit.

[0056] According to the CO2 delivery direction, the CO2 delivery unit includes a CO2 delivery pipeline 8, a gas compression device 7 and a wellhead multi-way valve 6 which are connected in sequence;

[0057] The seabed monitoring unit 9 is used to monitor the leakage of CO2 within 1000m around the wellhead of the injection main well; the side wall of the first horizontal branch well 10 is provided with a hydrate layer monitoring unit 13; the hydrate layer monitoring unit 13 is used to monitor the pressure of the hydrate stable layer 2;

[0058] The injection well system is arranged on the seabed 1 .

[0059] This embodiment also provides a method for storing carbon dioxide using the above injection well system, the method comprising the following steps:

[0060] (1) delivering liquid carbon dioxide and a carbon dioxide hydrate promoter to the first horizontal branch well by means of a CO2 delivery unit until the pressure of the hydrate stability layer reaches 95% of the fracture pressure of the hydrate stability layer, thereby forming a carbon dioxide hydrate cap layer in the hydrate stability layer;

[0061] Wherein, the addition amount of the carbon dioxide hydrate promoter is 500 mg / L; the carbon dioxide hydrate promoter is a mixture of tetrabutylammonium bromide, tetrabutylammonium fluoride and tetrabutylammonium chloride;

[0062] (2) delivering liquid carbon dioxide to the second horizontal branch well and / or the third horizontal branch well through the CO2 delivery unit until the seabed monitoring unit detects leakage of carbon dioxide;

[0063] (3) Perform cementing operations, and then repeat step (2) to achieve the storage of carbon dioxide.

[0064] Example 2

[0065] This embodiment provides an injection well system for storing carbon dioxide in a seafloor sediment layer, such as Figure 1 As shown, the injection well system includes an underwater blowout preventer 5, and an injection main well with a seabed monitoring unit 9 disposed below the underwater blowout preventer 5;

[0066] After the injection main well passes through the sedimentary layer, a first horizontal branch well 10 is extended in the hydrate stabilization layer 2, a second horizontal branch well 11 is extended in the saline layer 3, and a third horizontal branch well 12 is extended in the oil and gas layer 4.

[0067] The inlet of the main injection well is provided with a CO2 delivery unit.

[0068] According to the CO2 delivery direction, the CO2 delivery unit includes a CO2 delivery pipeline 8, a gas compression device 7 and a wellhead multi-way valve 6 which are connected in sequence;

[0069] The seabed monitoring unit 9 is used to monitor the leakage of CO2 within 1000m around the wellhead of the injection main well; the side wall of the first horizontal branch well 10 is provided with a hydrate layer monitoring unit 13; the hydrate layer monitoring unit 13 is used to monitor the pressure of the hydrate stable layer 2;

[0070] The injection well system is arranged on the seabed 1 .

[0071] This embodiment also provides a method for storing carbon dioxide using the above injection well system, the method comprising the following steps:

[0072] (1) delivering liquid carbon dioxide and a carbon dioxide hydrate promoter to the first horizontal branch well by means of a CO2 delivery unit until the pressure of the hydrate stability layer reaches 93% of the fracture pressure of the hydrate stability layer, thereby forming a carbon dioxide hydrate cap layer in the hydrate stability layer;

[0073] Wherein, the addition amount of the carbon dioxide hydrate promoter is 1000 mg / L; the carbon dioxide hydrate promoter is a mixture of tetrabutylammonium bromide, tetrabutylammonium fluoride and tetrabutylammonium chloride;

[0074] (2) delivering liquid carbon dioxide to the second horizontal branch well and / or the third horizontal branch well through the CO2 delivery unit until the seabed monitoring unit detects leakage of carbon dioxide;

[0075] (3) Perform cementing operations, and then repeat step (2) to achieve the storage of carbon dioxide.

[0076] Example 3

[0077] This embodiment provides an injection well system for storing carbon dioxide in a seafloor sediment layer, such as Figure 1 As shown, the injection well system includes an underwater blowout preventer 5, and an injection main well with a seabed monitoring unit 9 disposed below the underwater blowout preventer 5;

[0078] After the injection main well passes through the sedimentary layer, a first horizontal branch well 10 is extended in the hydrate stabilization layer 2, a second horizontal branch well 11 is extended in the saline layer 3, and a third horizontal branch well 12 is extended in the oil and gas layer 4.

[0079] The inlet of the main injection well is provided with a CO2 delivery unit.

[0080] According to the CO2 delivery direction, the CO2 delivery unit includes a CO2 delivery pipeline 8, a gas compression device 7 and a wellhead multi-way valve 6 which are connected in sequence;

[0081] The seabed monitoring unit 9 is used to monitor the leakage of CO2 within 1000m around the wellhead of the injection main well; the side wall of the first horizontal branch well 10 is provided with a hydrate layer monitoring unit 13; the hydrate layer monitoring unit 13 is used to monitor the pressure of the hydrate stable layer 2;

[0082] The injection well system is arranged on the seabed 1 .

[0083] This embodiment also provides a method for storing carbon dioxide using the above injection well system, the method comprising the following steps:

[0084] (1) delivering liquid carbon dioxide and a carbon dioxide hydrate promoter to the first horizontal branch well by means of a CO2 delivery unit until the pressure of the hydrate stability layer reaches 97% of the fracture pressure of the hydrate stability layer, thereby forming a carbon dioxide hydrate cap layer in the hydrate stability layer;

[0085] Wherein, the addition amount of the carbon dioxide hydrate promoter is 10 mg / L; the carbon dioxide hydrate promoter is a mixture of tetrahydropyran and cyclopentane;

[0086] (2) delivering liquid carbon dioxide to the second horizontal branch well and / or the third horizontal branch well through the CO2 delivery unit until the seabed monitoring unit detects leakage of carbon dioxide;

[0087] (3) Perform cementing operations, and then repeat step (2) to achieve the storage of carbon dioxide.

[0088] A comprehensive analysis of Examples 1-3 shows that the injection well system provided by the present invention can simultaneously and rapidly inject carbon dioxide into the hydrate stable layer, the saline layer and the deep oil and gas layer, increase the gas injection volume and injection rate, and achieve rapid storage of carbon dioxide; at the same time, during the storage process, various parameters are monitored in real time by the seabed monitoring system, and the gas injection process is intelligently controlled to maintain the stability of the formation pressure, avoid the leakage of carbon dioxide, and achieve safe storage.

[0089] Example 4

[0090] This embodiment provides an injection well system for storing carbon dioxide in a seafloor sediment layer. The injection well system is the same as that in Embodiment 1.

[0091] This embodiment also provides a method for storing carbon dioxide using the above injection well system. The difference between the method and the embodiment 1 is that:

[0092] In this embodiment, the end point of delivering liquid carbon dioxide in step (1) is adjusted to: the hydrate stability layer pressure is 85% of the hydrate stability layer fracture pressure.

[0093] Compared with Example 1, this embodiment reduces the pressure of the hydrate stabilization layer when the liquid carbon dioxide transportation is terminated in step (1). Although this will keep the formation pressure within a safe range and effectively avoid the appearance of formation cracks and the leakage of carbon dioxide, it will weaken the heat release covering capacity of the carbon dioxide hydrate cap layer and may reduce the storage capacity of carbon dioxide.

[0094] Example 5

[0095] This embodiment provides an injection well system for storing carbon dioxide in a seafloor sediment layer. The injection well system is the same as that in Embodiment 1.

[0096] This embodiment also provides a method for storing carbon dioxide using the above injection well system. The difference between the method and the embodiment 1 is that:

[0097] In this embodiment, the injection of the carbon dioxide hydrate promoter in step (1) is omitted.

[0098] Compared with Example 1, the injection of the carbon dioxide hydrate promoter is omitted in this example, which will lead to a decrease in the carbon dioxide hydrate generation rate, thereby causing a decrease in the carbon dioxide storage capacity.

[0099] Example 6

[0100] This embodiment provides an injection well system for storing carbon dioxide in a submarine sediment layer. The injection well system is different from that in Embodiment 1 only in that:

[0101] In this embodiment, the gas compression device 7 is omitted.

[0102] This embodiment also provides a method for storing carbon dioxide using the above injection well system. The method is the same as that in Embodiment 1.

[0103] Compared with Example 1, the present embodiment omits the gas compression device 7, and cannot realize the liquefaction of carbon dioxide gas, resulting in lower carbon dioxide injection efficiency and less carbon dioxide wind storage.

[0104] Comparative Example 1

[0105] This comparative example provides an injection well system for storing carbon dioxide in a submarine sediment layer. The injection well system differs from Example 1 only in that:

[0106] The configuration of the seabed monitoring unit is omitted in this comparative example.

[0107] This embodiment also provides a method for storing carbon dioxide using the above injection well system. The method is the same as that in Embodiment 1.

[0108] Compared with Example 1, the present comparative example omits the setting of the seabed monitoring unit, making it impossible to detect the leakage of carbon dioxide in time, which causes the formation pressure to exceed the fracture pressure of the formation, resulting in a large number of cracks, which in turn causes the leakage of carbon dioxide.

[0109] In summary, the injection well system and storage method provided by the present invention can simultaneously realize the injection of carbon dioxide into the hydrate stable layer, saline layer and oil and gas layer through one injection well, solving the current problems of limited offshore carbon dioxide storage capacity and high cost, effectively reducing drilling and operation costs and increasing economic benefits.

[0110] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. An injection well system for storing carbon dioxide in a submarine sediment layer, characterized in that: The injection well system includes an underwater blowout preventer and an injection main well with a seabed monitoring unit disposed below the underwater blowout preventer; After the injection main well passes through the sedimentary layer, a first horizontal branch well is extended in the hydrate stable layer, a second horizontal branch well is extended in the saline layer, and a third horizontal branch well is extended in the oil and gas layer. The inlet of the main injection well is provided with a CO2 delivery unit.

2. The injection well system according to claim 1, characterized in that: According to the CO2 delivery direction, the CO2 delivery unit includes a CO2 delivery pipeline, a gas compression device and a wellhead multi-way valve which are connected in sequence.

3. The injection well system according to claim 1, characterized in that: The seabed monitoring unit is used to monitor the leakage of CO2 within a range of 1000m around the wellhead of the main injection well.

4. The injection well system according to claim 1, characterized in that: A hydrate layer monitoring unit is provided on the side wall of the first horizontal branch well; Preferably, the hydrate layer monitoring unit is used to monitor the pressure of the hydrate stable layer.

5. The injection well system according to any one of claims 1 to 4, characterized in that: The injection well system is arranged on the seabed.

6. A method for storing carbon dioxide, characterized in that: The sealing method is carried out using the injection well system described in any one of claims 1-5.

7. The sealing method according to claim 6, characterized in that: The method comprises the following steps: (1) transporting liquid carbon dioxide and a carbon dioxide hydrate promoter to the first horizontal branch well through a CO2 transport unit to form a carbon dioxide hydrate cap layer in the hydrate stabilization layer; (2) transporting liquid carbon dioxide to the second horizontal branch well and / or the third horizontal branch well through the CO2 transport unit; (3) Perform cementing operations, and then repeat step (2) to achieve the storage of carbon dioxide.

8. The sealing method according to claim 7, characterized in that: The amount of the carbon dioxide hydrate promoter added in step (1) is 10 to 1000 mg / L; Preferably, the carbon dioxide hydrate promoter in step (1) includes any one of tetrahydropyran, cyclopentane, tetrabutylammonium bromide, tetrabutylammonium fluoride or tetrabutylammonium chloride, or a combination of at least two thereof.

9. The sealing method according to claim 7 or 8, characterized in that: The end point of the liquid carbon dioxide delivery in step (1) is: the hydrate stability layer pressure is 93-97% of the hydrate stability layer rupture pressure.

10. The sealing method according to any one of claims 7 to 9, characterized in that: The end point of the liquid carbon dioxide delivery in step (2) is: leakage of carbon dioxide is detected by the seabed monitoring unit.

Images