Cavity building method for thin salt layer salt cavern gas storage and salt cavern gas storage
By adopting a multi-well cavity building method in the salt layer area, including the design of vertical shafts and inclined shafts, the cavity expansion process is solved, and the problem of small capacity of salt hole gas storage in the thin salt layer is achieved, and a large amount of space is achieved The construction of salt hole gas storage with capacity and low cost has improved the stability and safety of the storage.
Patent Information
- Application Number
- CN202411204585.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2024-12-20
AI Technical Summary
In areas with high content of insoluble matter in the salt layer, deep burial and thin salt layer, when building a salt hole gas storage in a single well and single cavity, the storage capacity is usually not high and the cavity expansion is difficult, making it difficult to meet the large capacity needs.
The multi-well cavity building method is adopted, including drilling vertical shafts and inclined shafts above the salt layer. The inclined shaft has vertical sections and inclined sections. The inclined sections are connected to the main cavity. Through the process of expanding the cavity step by step, the transverse expansion chamber of the main cavity is added. Depth and capacity to avoid penetration and dissolution of the cavity roof, ensure that insoluble matter is deposited at the bottom and form slopes for improved stability.
The construction of large-capacity salt hole gas storage in the thin salt layer area has been achieved, which reduces the cost of cavity formation, improves the capacity and stability of the gas storage, and ensures the safety and stability of the gas storage.
Smart Images
Figure CN119163475A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of salt cavern gas storage construction, and in particular relates to a cavity making method for a thin salt layer salt cavern gas storage and a salt cavern gas storage. Background Art
[0002] Salt cavern gas storage is one of the important means of natural gas scheduling due to its large storage capacity, the fact that it does not occupy ground space, and its high safety. In particular, it is used to peak the consumption of natural gas. For example, in the summer and autumn when natural gas consumption is off-season, the surplus natural gas is stored in underground salt cavern gas storage, and in the spring and winter when gas consumption is at its peak, the natural gas stored in the salt cavern gas storage is used to supplement the consumption.
[0003] During the construction of salt cavern gas storage, different cavity creation methods need to be adopted due to the different local salt cavern geological conditions. For areas with high insoluble content in salt layers, deep burial depth, and thin salt layers, salt cavern gas storage is mostly constructed using a single-well single-cavity cavity creation method. However, it also has a defect that the storage capacity of a single reservoir is usually not high, and the difficulty of expanding the cavity is also high. Summary of the invention
[0004] In order to solve the above technical problems, one of the objectives of the present invention is to provide a method for building a cavern for a thin salt layer salt cavern gas storage which is easy to operate and can be used to build a large-capacity salt cavern gas storage in a thin salt layer area.
[0005] In order to achieve the above object, the technical solution of the present invention is as follows: A method for creating a cavern in a thin salt layer salt cavern gas storage comprises the following steps:
[0006] Step 1: Drill a vertical shaft above the salt layer for reservoir construction, with the lower end reaching the salt layer for reservoir construction, and construct a main cavity in the salt layer for reservoir construction with the lower end of the vertical shaft;
[0007] Step 2: Drilling an inclined well above the salt layer for building a library and beside the vertical well, wherein the inclined well has a vertical section and an inclined section, and the lower end of the vertical section is close to the top plate of the salt layer for building a library, and the lower end of the inclined section is connected to the lower part of the main cavity;
[0008] Step 3: Expand the main cavity step by step from bottom to top along the inclined section until the expansion of the main cavity is completed.
[0009] The beneficial effect of the above technical solution is that the cavity can be expanded transversely at the side wall of the main cavity, so that the storage capacity of the entire salt cavern gas storage is increased, but it is still within the salt layer where the storage is built.
[0010] The distance between the lower end of the vertical shaft in the above technical solution and the bottom plate of the salt layer for reservoir construction is at least 3m.
[0011] The beneficial effect of the above technical solution is that it can prevent the lower end of the main cavity from penetrating the lower end of the salt layer for the reservoir.
[0012] The horizontal distance from the vertical section to the vertical shaft in the above technical solution is at least 50m.
[0013] The beneficial effect of the above technical solution is that the inclined sections can have sufficient spacing to reduce their inclination angles, which can improve the cavity expansion effect and cavity expansion capacity.
[0014] The inclination angle of the inclined section relative to the horizontal plane in the above technical solution is not greater than 25°.
[0015] The beneficial effect of the above technical solution is that its inclination angle is gentle, so that the lateral expansion depth of the main cavity can be appropriately increased, which is beneficial to improving the expansion capacity.
[0016] The thickness of the salt layer for reservoir construction described in the above technical solution is at least 50m.
[0017] The beneficial effect of the above technical solution is to avoid the roof of the salt layer for the reservoir being corroded by the cavity top due to the salt layer for the reservoir being too thin.
[0018] The specific operation of forming a cavity at the lower end of the vertical shaft in step 1 of the above technical solution is: sequentially lowering a first cavity-forming outer tube and a cavity-forming inner tube into the vertical shaft to inject fresh water into the vertical shaft to form a cavity, stopping cavity forming after the height of the main cavity reaches a set height, and injecting a dissolving agent into the main cavity.
[0019] The beneficial effect of the above technical solution is that injecting the dissolving agent into the main cavity can prevent the cavity top of the main cavity from being further dissolved during the subsequent cavity expansion process.
[0020] The distance between the lower end of the inclined section in step 2 of the above technical solution and the connection point with the main cavity and the bottom wall of the main cavity is H, wherein H=1.5·h·α, h is the height of the main cavity, and α is the average insoluble content of the salt layer for storage.
[0021] The beneficial effect of the above technical solution is that the insoluble matter deposited in the later stage of the entire salt cavern gas storage reservoir is deposited to the bottom of the main cavity, especially the insoluble matter in the expansion cavity area is also deposited to the bottom of the main cavity.
[0022] The specific operation of expanding the cavity in step 3 of the above technical solution is:
[0023] Step 3.1: multiple water injection points are selected at equal intervals along the length of the inclined section; Step 3.2: a second cavity-making outer tube is lowered into the inclined well, and the end of the second cavity-making outer tube is first lowered to the lowest water injection point, and then fresh water is injected into the inclined section to expand the end of the inclined section until the expansion of the cavity at the lowest water injection point is completed;
[0024] Step 3.3: Lift up the second cavity-making outer tube until the end of the second cavity-making outer tube is located at the second water injection point at the bottom, and inject fresh water into the second water injection point at the bottom to expand the cavity until the expansion of the second water injection point at the bottom is completed, and so on, gradually extract the second cavity-making outer tube upward until the expansion is completed at all water injection points, that is, the cavity expansion operation of the main cavity is completed.
[0025] The beneficial effect of the above technical solution is that the cavity expansion area is expanded step by step from bottom to top along the inclined section for multiple times, so that the cavity expansion safety is improved, and at the same time a slope can be formed at the bottom of the cavity expansion area, which can improve the stability of the entire salt cavern gas storage.
[0026] In the above technical solution, the vertical distance from the top of the expanded cavity at the uppermost water injection point to the roof of the salt layer for reservoir construction is greater than 15m.
[0027] The beneficial effect of the above technical solution is that the expanded cavity area has good safety and stability.
[0028] A second object of the present invention is to provide a salt cavern gas storage which has a simple structure and is located in a thin salt layer area but has a large cavity capacity.
[0029] In order to achieve the above-mentioned purpose, another technical solution of the invention is as follows: a salt cavern gas storage is made by the above-mentioned thin salt layer salt cavern gas storage cavity making method.
[0030] The beneficial effects of the above technical solution are: low cavity making cost and large gas storage capacity. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 This is a schematic diagram of the structure of the inclined well relative to the main cavity in Example 1 of the present invention;
[0032] Figure 2 It is a schematic diagram of multiple water injection points and multiple cavity expansion sections in the inclined section in Example 1 of the present invention;
[0033] Figure 3 Schematic diagram of the cavity expansion of the N1 cavity expansion section in Example 1 of the present invention;
[0034] Figure 4 It is a topological schematic diagram of the cavity expansion process of multiple cavity expansion sections in Example 1 of the present invention;
[0035] Figure 5 This is a schematic diagram of the structure after the inclined section cavity expansion is completed in Example 1 of the present invention.
[0036] In the figure: 1, vertical shaft; 2, main cavity; 3, inclined shaft; 31, vertical section; 32, inclined section; 321, water injection point; 4, first cavity outer pipe; 5, cavity inner pipe; 6 sediment layer; 7, second cavity outer pipe; 8 cavity expansion area. DETAILED DESCRIPTION
[0037] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the accompanying drawings in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.
[0038] Example 1
[0039] like Figure 1-Figure 5 As shown, this embodiment provides a method for creating a cavern in a thin salt layer salt cavern gas storage, comprising the following steps:
[0040] Step 1: Drill a vertical shaft 1 above the salt layer for reservoir construction, with the lower end thereof extending into the salt layer for reservoir construction, and construct a main cavity 2 in the salt layer for reservoir construction with the lower end of the vertical shaft 1;
[0041] Step 2: Drilling an inclined well 3 above the salt layer for building a library and beside the vertical well 1, wherein the inclined well 3 has a vertical section 31 and an inclined section 32, and the lower end of the vertical section 31 is close to the top plate of the salt layer for building a library, and the lower end of the inclined section 32 is communicated with the lower part of the main cavity 2;
[0042] Step 3: The main cavity 2 is expanded step by step from bottom to top along the inclined section 32 until the expansion of the main cavity 2 is completed, so that the side wall of the main cavity can be expanded horizontally, thereby increasing the storage capacity of the entire salt cavern gas storage reservoir while still being within the salt layer for reservoir construction.
[0043] The distance between the lower end of the vertical shaft 1 in the above technical solution and the bottom plate of the salt layer for reservoir construction is at least 3m (preferably any value among 3m, 4m, 5m, 6m, 7m, 8m, 9m and 10m or the corresponding range between any two values), so as to avoid the lower end of the main cavity penetrating the lower end of the salt layer for reservoir construction.
[0044] In the above technical solution, the horizontal distance between the vertical section 31 and the shaft 1 is at least 50m, so that the inclined section can have sufficient distance to reduce its inclination angle, which can improve its cavity expansion effect and cavity expansion capacity.
[0045] The inclination angle of the inclined section 32 relative to the horizontal plane in the above technical solution is not greater than 25° (it can be any value among 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24° and 25°, and the range corresponding to any two values), and its inclination angle is gentle, so that the lateral expansion depth of the main cavity can be appropriately increased, which is beneficial to increasing the expansion capacity.
[0046] Among them, the lower end of the vertical section is lowered to below the top plate of the salt layer for reservoir construction, and the vertical spacing from the lower end of the vertical section to the top plate of the salt layer for reservoir construction can be 5-20m (preferably any value among 5m, 6m, 7m, 8m, 9m, 10m, 11m, 12m, 13m, 14m, 15m, 16m, 17m, 18m, 19m and 20m, or the corresponding range between any two values).
[0047] The thickness of the salt layer for reservoir construction described in the above technical solution is at least 50m, so as to avoid the roof of the reservoir salt layer being corroded by the cavity top due to the salt layer for reservoir construction being too thin.
[0048] like Figure 1 As shown, the specific operation of making a cavity at the lower end of the vertical shaft 1 in step 1 of the above technical solution is: sequentially lowering a first cavity-making outer tube 4 and a cavity-making inner tube 5 into the vertical shaft 1 to inject fresh water into the vertical shaft 1 to make a cavity (the created cavity is the main cavity 2), stopping the cavity making after the height of the main cavity 2 reaches the set height, and injecting a dissolving agent into the main cavity 2. The injection of the dissolving agent into the main cavity can prevent the cavity top of the main cavity from being further dissolved during the subsequent cavity expansion process.
[0049] Among them, the lower end of the inner cavity tube 5 protrudes from the lower end of the first outer cavity tube 4. The first outer cavity tube is used to inject fresh water into the lower end of the shaft, while the inner cavity tube discharges the brine in the shaft upward. In this process, the salt layer corresponding to the salt layer around the lower end of the shaft is continuously dissolved, so that the main cavity is continuously expanded (mainly toward the periphery). When the main cavity is expanded to its height reaching the designed height h, an anti-solvent (diesel can be used) can be injected into the main cavity. The anti-solvent mainly forms an oil film floating on the upper end of the brine to prevent the top of the salt cave from continuing to dissolve.
[0050] The distance between the lower end of the inclined section 32 in step 2 of the technical solution and the connection point between the main cavity 2 and the bottom wall of the main cavity 2 is H, wherein H=1.5·h·α, h is the height of the main cavity 2, and α is the average insoluble content of the salt layer for storage construction, so that the insolubles deposited in the later stage of the entire salt cavern gas storage reservoir are deposited to the bottom of the main cavity, especially the insolubles in the expansion cavity area are also deposited to the bottom of the main cavity.
[0051] The specific operation of expanding the cavity in step 3 of the above technical solution is:
[0052] Step 3.1: select multiple water injection points 321 at equal intervals along the length direction of the inclined section 32;
[0053] Step 3.2: lower the second cavity-making outer pipe 7 into the inclined well 3, and the end of the second cavity-making outer pipe 7 is first lowered to the lowest water injection point 321, and then fresh water is injected into the inclined section 32 to expand the end of the inclined section 32 (while still using the cavity-making inner pipe to discharge brine to the outside), until the cavity expansion is completed at the lowest water injection point 321;
[0054] Step 3.3: lift the second cavity-making outer tube 7 until the end of the second cavity-making outer tube 7 is located at the second water injection point 321 at the bottom, and inject fresh water into the second water injection point 321 at the bottom to expand the cavity until the expansion of the second water injection point 321 at the bottom is completed, and so on, the second cavity-making outer tube 7 is gradually extracted upward until the cavity expansion is completed at all water injection points 321, that is, the cavity expansion operation of the main cavity 2 is completed, and the cavity expansion area is gradually expanded from bottom to top along the inclined section for multiple times, so that the cavity expansion safety is improved, and at the same time, a slope can be formed at the bottom of the cavity expansion area, which can improve the stability of the entire salt cavern gas storage reservoir.
[0055] In the above technical solution, the vertical distance between the expanded cavity top at the top water injection point 321 and the salt layer roof of the reservoir construction is greater than 15m, which makes the expanded cavity area safer and more stable.
[0056] Specifically, Figure 2 As shown, n water injection points 321 are set on the inclined section 32, and the area between two adjacent water injection points on the inclined section is an expansion section, and an expansion section is also formed between the lowest water injection point and the end of the inclined section. At this time, the inclined section is divided into n expansion sections (respectively N1 section, N2 section, N3 section, ..., Nn section, wherein the inclined section is expanded in the order of N1 section, N2 section, N3 section, ..., Nn section), each water injection point corresponds to the expansion section immediately below it (when the end of the second cavity-making outer tube is at any water injection point, it is the expansion section corresponding to the water injection point that is expanded). Preferably, the distance between the lowest water injection point and the end of the inclined section is about 30m.
[0057] The pressure of fresh water injected during cavity creation or expansion should be higher than the formation pressure and should be adjusted according to the required range.
[0058] For each expansion cavity section, the pre-designed expansion cavity volume is V Nx (x is 1, 2, 3, ..., n), specifically, VN1 V represents the designed expansion volume of the N1 expansion section; N2 represents the designed expansion volume of the N2 expansion section; and so on, V Nn It represents the designed expansion volume of the Nn expansion section.
[0059] The mass of dissolved salt in brine M s Determine the current expansion volume V of the inclined segment Nx c Whether the design value V of the cavity volume of segment Nx is reached Nx , the calculation formula is as follows:
[0060] M s =M1+M2
[0061]
[0062]
[0063]
[0064] Among them, M s is the total mass of dissolved salt in the brine; M1 is the mass of dissolved salt in the discharged brine; M2 is the mass of dissolved salt in the brine in the cavity; C o is the concentration of brine discharged; C i is the brine concentration in the cavity; V1 is the volume of brine discharged; V2 is the volume of brine in the cavity; V3 is the total volume of fresh water injected from the beginning of the expansion of the Nx section; V s is the total volume of dissolved salt in brine; ρ s V is the density of salt rock in the cavity-forming salt layer; c is the current expansion volume of the inclined section Nx; α is the average insoluble content of the salt layer in the reservoir. c Corresponding to V Nx When they are close or consistent, it can be assumed that the Nx-stage cavity expansion is completed, and the next cavity expansion operation can be started or the cavity expansion is completed.
[0065] The judgment process is as follows Figure 4 As shown, when the volume of the inclined well section cavity reaches the design value of the N1 section cavity volume, the cavity making outer pipe 6 stops injecting water and withdraws the cavity making outer pipe 6 to the water injection point N2, and so on. The above process is repeated in each stage until the cavity making of the Nn section is completed.
[0066] The final cavity shape is as follows Figure 5 shown.
[0067] In the attached figure, mark A indicates the position of the top plate of the salt layer where the reservoir is built; mark B indicates the position of the bottom plate of the salt layer where the reservoir is built; and mark C indicates the ground.
[0068] When all the expansion sections have completed the expansion, an expansion area 8 will be formed on the side of the main cavity. Of course, in order to further expand the volume of the salt cavern gas storage, it is also possible to consider setting up multiple expansion areas (which can be 2-4) around the periphery of the main cavity in an annular manner. The construction method of a single expansion area can be carried out according to the method described in this embodiment.
[0069] Example 2
[0070] This embodiment provides a salt cavern gas storage reservoir, which is manufactured by the cavity making method of a thin salt layer salt cavern gas storage reservoir as described in Embodiment 1, and has low cavity making cost and large gas storage capacity.
[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.
Claims
1. A method for creating a cavern in a thin salt layer salt cavern gas storage, characterized in that: The steps include: Step 1: Drill a vertical shaft (1) above the salt layer for reservoir construction, with its lower end reaching the salt layer for reservoir construction, and construct a main cavity (2) in the salt layer for reservoir construction with the lower end of the vertical shaft (1); Step 2: Drilling an inclined well (3) above the salt layer for building a reservoir and beside the vertical well (1), wherein the inclined well (3) comprises a vertical section (31) and an inclined section (32), wherein the lower end of the vertical section (31) is close to the top plate of the salt layer for building a reservoir, and the lower end of the inclined section (32) is in communication with the lower part of the main cavity (2); Step 3: Expand the main cavity (2) step by step from bottom to top along the inclined section (32) until the expansion of the main cavity (2) is completed.
2. The method for creating a cavern for a thin salt layer salt cavern gas storage according to claim 1, characterized in that: The distance between the lower end of the vertical shaft (1) and the bottom plate of the salt layer for building the reservoir is at least 3 m.
3. The method for creating a cavern for a thin salt layer salt cavern gas storage according to claim 1, characterized in that: The horizontal distance between the vertical section (31) and the shaft (1) is at least 50 m.
4. The method for creating a cavern for a thin salt layer salt cavern gas storage according to claim 1, characterized in that: The inclination angle of the inclined section (32) relative to the horizontal plane is not greater than 25°.
5. The method for creating a cavern for a thin salt layer salt cavern gas storage according to claim 1, characterized in that: The thickness of the salt layer for reservoir construction is at least 50m.
6. The method for creating a cavern for a thin salt layer salt cavern gas storage according to claim 1, characterized in that: The specific operation of forming a cavity at the lower end of the vertical shaft (1) in step 1 is: sequentially lowering a first cavity forming outer tube (4) and a cavity forming inner tube (5) into the vertical shaft (1) to inject fresh water into the vertical shaft (1) to form a cavity, stopping the cavity forming after the height of the main cavity (2) reaches a set height, and injecting a dissolving agent into the main cavity (2).
7. The method for creating a cavern in a thin salt layer salt cavern gas storage according to claim 1, characterized in that: The distance between the lower end of the inclined section (32) in step 2 and the connection point with the main cavity (2) and the bottom wall of the main cavity (2) is H, wherein H=1.5·h·α, h is the height of the main cavity (2), and α is the average insoluble matter content of the salt layer in the reservoir.
8. The method for creating a cavern in a thin salt layer salt cavern gas storage according to claim 1, characterized in that: The specific operation of cavity expansion in step 3 is: Step 3.1: selecting a plurality of water injection points (321) at equal intervals along the length direction of the inclined section (32); Step 3.2: lowering a second cavity-making outer tube (7) into the inclined well (3), and first lowering the end of the second cavity-making outer tube (7) to the lowest water injection point (321), and then injecting fresh water into the inclined section (32) to expand the end of the inclined section (32), until the expansion of the cavity at the lowest water injection point (321) is completed; Step 3.3: Lift the second cavity-making outer tube (7) until the end of the second cavity-making outer tube (7) is located at the second lowest water injection point (321), and inject fresh water into the second lowest water injection point (321) to expand the cavity until the cavity expansion of the second lowest water injection point (321) is completed, and so on, the second cavity-making outer tube (7) is gradually pulled upward until the cavity expansion is completed at all water injection points (321), that is, the cavity expansion operation of the main cavity (2) is completed.
9. The method for creating a cavern in a thin salt layer salt cavern gas storage according to claim 8, characterized in that: The vertical distance between the expanded cavity top at the top water injection point (321) and the salt layer roof of the reservoir construction is greater than 15m.
10. A salt cavern gas storage, characterized in that: The gas storage device is prepared by using the method for creating a cavity in a thin salt layer salt cavern as described in any one of claims 1 to 9.