Brine discharging well structure for efficient gas injection and brine discharging of compressed air energy storage underground salt cavern

Abstract

The utility model provides a brine discharging well structure for efficient gas injection and brine discharging of a compressed air energy storage underground salt cavern, which is of a three-opening well body structure, and the sizes of a first-opening well hole, a second-opening well hole and a third-opening well hole are gradually reduced in sequence; the first well-opening type is a vertical well, the second well-opening type comprises a vertical well section and an inclined well section, the third well-opening type comprises a first inclined shaft way, a second inclined shaft way and a third inclined shaft way, and the first inclined shaft way, the second inclined shaft way and the third inclined shaft way are communicated with a salt cavern; in the third well type, a first inclined shaft communicated with a first cavity inlet of the salt cavern is located above the sediment surface, a second inclined shaft communicated with a second cavity inlet of the salt cavern is located in the middle of sediment, and a third inclined shaft communicated with a third cavity inlet of the salt cavern is located at the bottom of the sediment; the second inclined shaft is smaller than the first inclined shaft and the third inclined shaft; and a brine discharging inner pipe for injection and discharging is arranged in the brine discharging well and reaches the salt cavern through the first inclined shaft way, the second inclined shaft way and the third inclined shaft way. According to the utility model, the multi-channel brine discharging operation is optimized, so that the brine discharging flow can be effectively increased, and the gas injection brine discharging efficiency is improved. Meanwhile, the underground engineering construction period of the compressed air energy storage power station can be shortened, and investment cost is saved.

Description

Technical Field

[0001] The utility model relates to the field of brine drainage wells in compressed air energy storage reservoirs, and particularly relates to a brine drainage well structure for efficient gas injection and brine drainage in an underground salt cavern for compressed air energy storage. Background Technique

[0002] The salt cavern type compressed air energy storage reservoir uses the salt cavern formed after the solution mining of underground salt mines as the gas storage space. Based on the unique damage self-healing, low permeability and good creep properties of salt rock, the salt cavern type compressed air energy storage reservoir has been well applied. The displacement of brine is a key link in the utilization of underground salt caverns. The technology of injecting high-pressure air to discharge the brine in the salt cavern is called the gas injection and brine drainage technology. The existing gas injection and brine drainage technologies are mainly divided into the single-well convection gas injection and brine drainage technology and the horizontal docking well gas injection and brine drainage technology. In the single-well convection gas injection and brine drainage technology, high-pressure gas is injected into the annulus between the central pipe and the casing, and the brine is discharged from the central pipe. This method can quickly displace the brine in the salt cavern, but there is a problem that the sediment space is difficult to utilize; the horizontal docking well gas injection and brine drainage technology is to drill a new brine drainage well, inject gas through the injection-production well, and under the action of pressure, the brine is discharged through the wellhead of a single brine drainage well. This method can make full use of the sediment void space and increase the gas storage capacity, but this method has three disadvantages: one is that the single brine drainage port is easy to be blocked during the process of gas injection and brine drainage; the second is that the brine drainage efficiency is low, which affects the project progress; the third is that there is no standby brine drainage channel after the brine drainage channel is blocked.

[0003] In view of the problems such as the long gas injection and brine drainage period and the easy blockage of the brine drainage channel, improving the brine drainage well structure can further improve the gas injection and brine drainage efficiency. Therefore, it is necessary to develop a brine drainage well structure for efficient gas injection and brine drainage in an underground salt cavern for compressed air energy storage. Content of the Utility Model

[0004] The utility model aims at the deficiencies of the prior art and provides a brine drainage well structure for efficient gas injection and brine drainage in an underground salt cavern for compressed air energy storage, which can effectively increase the brine drainage flow rate, improve the gas injection and brine drainage efficiency and shorten the construction period.

[0005] The utility model adopts the following technical scheme:

[0006] A brine drainage well structure for efficient gas injection and brine drainage in an underground salt cavern for compressed air energy storage includes a salt cavern and a brine drainage well;

[0007] The brine drainage well has a three-opening wellbore structure, and the sizes of the first-opening wellbore, the second-opening wellbore and the third-opening wellbore decrease in turn; the first-opening well type is a vertical well; the second-opening well type includes a vertical well section and an inclined well section; the third-opening well type includes a first inclined well channel, a second inclined well channel and a third inclined well channel; the first inclined well channel, the second inclined well channel and the third inclined well channel are communicated with the salt cavern;

[0008] Taking into comprehensive consideration the influences of sediment in the salt cavern being prone to blockage, formation pressure, and block accumulation, the first inclined wellbore communicates with the first inlet opening of the salt cavern, and the first inlet opening is located above the sediment surface of the salt cavern; the second inclined wellbore communicates with the second inlet opening of the salt cavern, and the second inlet opening is located in the middle of the sediment in the salt cavern; the third inclined wellbore communicates with the third inlet opening of the salt cavern, and the third inlet opening is located at the bottom of the sediment in the salt cavern.

[0009] A brine discharge main pipe is arranged in the brine discharge well. Three brine discharge branch pipes are arranged at the first inclined wellbore, the second inclined wellbore, and the third inclined wellbore of the brine discharge main pipe. The three brine discharge branch pipes respectively reach the salt cavern through the first inclined wellbore, the second inclined wellbore, and the third inclined wellbore; the three brine discharge branch pipes converge into the brine discharge main pipe.

[0010] In any of the possible implementation manners described above, a further implementation manner is provided. The first-stage casing is lowered 20 m below the bedrock, the second-stage casing is lowered 30 m below the salt layer, and the third-stage well does not have a casing and reaches the salt cavern with an open hole.

[0011] In any of the possible implementation manners described above, a further implementation manner is provided. The first inlet opening is arranged 2 m above the sediment surface of the salt cavern, the second inlet opening is arranged at the 1 / 2 depth of the sediment in the salt cavern, and the third inlet opening is arranged at a position 2 m away from the bottom of the sediment in the salt cavern.

[0012] In any of the possible implementation manners described above, a further implementation manner is provided. The sizes of the first inclined wellbore and the third inclined wellbore are both larger than the size of the second inclined wellbore.

[0013] In any of the possible implementation manners described above, a further implementation manner is provided. The horizontal distance from the brine discharge well to the salt cavern is not less than 100 m.

[0014] In any of the possible implementation manners described above, a further implementation manner is provided. The wellbore diameters of the first inclined wellbore and the second inclined wellbore are 177.8 mm, and the wellbore diameter of the second inclined wellbore is 139.7 mm.

[0015] In any of the possible implementation manners described above, a further implementation manner is provided. A deviation point is set on the second-stage wellbore. The section above the deviation point is a vertical well section, and the section below the deviation point is an inclined well section.

[0016] In any of the possible implementation manners described above, a further implementation manner is provided. The diameter of the brine discharge main pipe is 88.9 mm, and the brine discharge branch pipes are screen pipe washing pipes with a diameter of 73 mm.

[0017] The beneficial effects of the present utility model are as follows:

[0018] 1. The brine drainage well structure provided by the present utility model can significantly improve the efficiency of gas injection and brine drainage, and shorten the construction period. It is estimated that adopting this brine drainage well structure can shorten the construction period by 1 / 4 - 1 / 3 from the perspective of the entire gas injection and brine drainage operation cycle.

[0019] 2. The brine drainage well structure provided by the present utility model will increase certain costs during the initial well drilling stage. However, considering that the main cost in the gas injection and brine drainage funds is mainly the daily electricity cost, for the entire gas injection and brine drainage cycle, shortening the construction period can save certain economic costs.

[0020] 3. The brine drainage well structure provided by the present utility model can reduce the number of times of flushing sediment during the entire gas injection and brine drainage period when the gas injection pressure of the gas injection well is stable. At the same time, by using two channels, namely the annulus between the production casing and the inner brine drainage pipe and the inner brine drainage pipe, to drain brine, the brine drainage volume is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure shows a schematic structural diagram of the brine drainage well structure for efficient gas injection and brine drainage in an underground salt cavern for compressed air energy storage according to an embodiment of the present utility model.

[0022] Figure 2 The figure shows a schematic diagram of two-channel brine drainage of the brine drainage well structure in the embodiment.

[0023] In the figure: 1 - salt cavern; 2 - surface casing; 3 - intermediate casing; 4 - kick-off point; 5 - first sidetrack point; 6 - second sidetrack point; 7 - sediment; 100 - first inclined wellbore; 101 - first cavity inlet; 200 - second inclined wellbore; 201 - second cavity inlet; 300 - third inclined wellbore; 301 - third cavity inlet; 400 - main inner brine drainage pipe; 401, 402, 403 - inner brine drainage branch pipes. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will describe the specific embodiments of the present utility model in detail with reference to the specific drawings. It should be noted that the technical features described in the following embodiments or the combinations of technical features should not be considered as isolated, and they can be combined with each other to achieve better technical effects.

[0025] As Figure 1 shown, an embodiment of the brine drainage well structure for efficient gas injection and brine drainage in an underground salt cavern for compressed air energy storage according to the present utility model includes a salt cavern 1 and a brine drainage well:

[0026] The brine drainage well has a three-opening wellbore structure, and the sizes of the first-opening wellbore, the second-opening wellbore, and the third-opening wellbore decrease in sequence; the first-opening well type is a vertical well; the second-opening well type includes a vertical well section and an inclined well section respectively; the third-opening well type includes a first inclined well passage 100, a second inclined well passage 200, and a third inclined well passage 300; the first inclined well passage 100, the second inclined well passage 200, and the third inclined well passage 300 are connected to the salt cavern 1;

[0027] The first inclined well passage 100 is connected to the first cavity inlet 101 of the salt cavern 1, and the first cavity inlet 101 is located above the sediment surface of the salt cavern 1; the second inclined well passage 200 is connected to the second cavity inlet 201 of the salt cavern 1, and the second cavity inlet 201 is located in the middle of the sediment of the salt cavern 1; the third inclined well passage 300 is connected to the third cavity inlet 301 of the salt cavern 1, and the third cavity inlet 301 is located at the bottom of the sediment of the salt cavern 1;

[0028] A brine drainage inner main pipe 400 is arranged in the brine drainage well. Three brine drainage inner branch pipes 401, 402, and 403 are arranged at the first inclined well passage 100, the second inclined well passage 200, and the third inclined well passage 300 of the brine drainage inner main pipe 400. The three brine drainage inner branch pipes respectively pass through the first inclined well passage 100, the second inclined well passage 200, and the third inclined well passage 300 to reach the salt cavern 1; the three brine drainage inner branch pipes 401, 402, and 403 converge into the brine drainage inner main pipe 400.

[0029] In a specific embodiment, the first-opening well casing 2 is lowered 20 m below the bedrock, and the purpose is to seal the shallow water; the second-opening well casing 3 is lowered 30 m below the salt layer, and the purpose is to seal the salt layer and the caprock section above the cavity to ensure the integrity of the wellbore.

[0030] In a specific embodiment, the well type of the first-opening well casing 2 is a vertical well. The well type of the second-opening well casing 3 is divided into two parts. One part is above the kick-off point 4, and the well type is a vertical well; the other part is below the kick-off point 4, and the well type is an inclined well. The third opening drills to the salt cavern 1 and is completed with an open hole.

[0031] In a specific embodiment, the drilling sequence of the three openings in the brine drainage well structure: The first step is to drill according to the trajectory of the first inclined well passage 100 to reach the first cavity inlet 101 of the salt cavern 1; the second step is to lift the drill string to the first sidetracking point 5 and drill to the second cavity inlet 201 of the salt cavern 1 according to the trajectory of the second inclined well passage 200; the third step is to lift the drill string to the second sidetracking point 6 and drill to the third cavity inlet 301 according to the trajectory of the third inclined well passage 300.

[0032] In a specific embodiment, the first inlet opening 101 is provided 2 m above the sediment surface 7 of the salt cavern 1, the second inlet opening 201 is provided at the 1 / 2 depth of the sediment 7 of the salt cavern 1, and the third inlet opening 301 is provided at a position 2 m away from the bottom of the sediment 7 of the salt cavern 1. This design of the inlet opening can ensure a significant increase in the discharge rate in the early stage of brine drainage, is not easily blocked at the inlet opening in the middle stage of brine drainage, and meets the requirement of not less than the minimum discharge rate in the later stage of brine drainage.

[0033] In a specific embodiment, the sizes of the first inclined wellbore 100 and the third inclined wellbore 300 are both larger than that of the second inclined wellbore 200. The wellbore diameters of the first inclined wellbore 100 and the third inclined wellbore 300 are preferably 177.8 mm, and the wellbore diameter of the second inclined wellbore 200 is preferably 139.7 mm. This design of the wellbore size can effectively reduce the risk of sediment blockage and ensure the relatively smooth operation of the brine drainage operation in the entire gas injection and brine drainage project. Due to the action of sediment accumulation and formation pressure, the disturbance of the sediment from top to bottom in the salt cavern 1 is gradually decreasing under the influence of gas injection and brine drainage. The second inlet opening 201 located at the 1 / 2 position of the sediment is more likely to be affected by sediment blockage compared with the third inlet opening 301 at the bottom of the sediment, and the first inlet opening 101 is located above the sediment surface 7, with a relatively small risk of sediment blockage. Therefore, the designed wellbore size of the second inclined wellbore 200 trajectory is smaller than that of the third inclined wellbore 300 trajectory and the first inclined wellbore 100 trajectory, which can reduce the risk of the sediment blocking the second inlet opening 201. At the same time, the maximum discharge rate of brine drainage can also be achieved for the first inclined wellbore 100 trajectory and the second inclined wellbore 300 trajectory.

[0034] In a specific embodiment, the horizontal distance from the brine drainage well to the salt cavern 1 is not less than 100 m, aiming to reserve enough horizontal section length to ensure that the underground brine drainage wellhead can smoothly enter the salt cavern.

[0035] In a specific embodiment, after the third drilling is completed, the drill string is pulled out, and the inner main brine drainage pipe 400 with a screen pipe is lowered. The screen pipe nozzle can prevent sediment and gravel from blocking the brine drainage pipe string. The depth of the inner main brine drainage pipe 400 is the sidetracking point 6. At the same time, three inner brine drainage branch pipes 401, 402, and 403 are branched out at the sidetracking points 5 and 6 respectively, and are delivered to the inlet openings 101, 201, and 301 along the inclined wellbores 100, 200, and 300.

[0036] In a specific embodiment, before the gas injection and brine drainage start, fresh water is injected through the inner brine drainage pipe with a screen pipe to dissolve the inlet openings 101, 201, and 301, increasing the cross-sectional area of the inlet openings. Among them, the inner main brine drainage pipe 400 preferably has a diameter of 88.9 mm, and the inner brine drainage branch pipes 401, 402, and 403 preferably have a diameter of 73 mm and are screen pipe flushing pipes.

[0037] The inlet opening 101 above the sediment surface is 2 m above the sediment surface, and will not be affected by the sediment or will be affected very little, so a larger-sized brine drainage channel can be adopted; the inlet opening 301 at the bottom of the sediment has the risk of sediment blockage, but due to the effects of pressure and block accumulation, the sediment at the inlet opening 301 is more significantly compacted than that at the inlet opening 201. Therefore, the size of the brine drainage channel at the 1 / 2 position of the sediment is set smaller than the brine drainage channel sizes at the bottom of the sediment and the upper part of the sediment surface.

[0038] In a specific embodiment, to maximize the brine drainage flow rate, during the gas injection and brine drainage operation stage, the wellhead brine drainage valve and the brine drainage pipeline valve are opened, and brine drainage is carried out simultaneously through the annulus between the production casing and the inner brine drainage pipe 400 and the double channels of the inner brine drainage pipe. The double-channel brine drainage is as Figure 2 shown. The gas injection pressure of the injection-production well drives the brine drainage of the brine drainage well. There are respective on-off valves at the wellhead of both the annulus between the inner brine drainage pipe and the casing and the two channels of the inner brine drainage pipe. To achieve simultaneous brine drainage through the two channels, only two valves need to be opened. When flushing and plugging the sediment, the annulus valve is closed, and the inner brine drainage pipe water injection valve is opened to flush and plug the sediment.

[0039] The working principle of the present utility model:

[0040] For the brine drainage well, a three-opening wellbore structure is adopted, and the wellbore sizes of the first opening, the second opening, and the third opening decrease in sequence. The first opening drills 20 m below the bedrock, aiming to seal the shallow water; the second opening drills 30 m into the salt layer, aiming to seal the salt layer and the caprock section above the cavity to ensure the integrity of the wellbore; the third opening drills to the salt cavern and is completed with an open hole. Among them, to ensure that the third opening can smoothly drill to the salt cavern, the distance between the wellhead of the brine drainage well and the side wall of the salt cavern 1 should be greater than 100 m. In the wellbore structure, the third opening adopts a sidetracking method and drills to the inlet opening along three drilling trajectories. Preferably, the distribution positions of the three inlet openings are at the position 2 m above the sediment surface, at the 1 / 2 position of the sediment, and at the position 2 m above the bottom of the sediment. At the same time, to increase the brine drainage flow rate and reduce the risk of sediment blockage at the inlet opening, the size of the brine drainage channel at the 1 / 2 position of the sediment is smaller than the other two channels, and a screen pipe inner pipe is lowered into each brine drainage channel. During the preliminary preparation stage of gas injection and brine drainage, water injection into the inner brine drainage pipe can dissolve the inlet opening to increase the size of the inlet opening. During the stable operation stage of gas injection and brine drainage, the inner brine drainage pipe can be used as a brine drainage channel for brine drainage.

[0041] The brine drainage well structure provided by the present utility model can effectively improve the gas injection and brine drainage efficiency, shorten the construction period, and save the construction investment cost.

[0042] Although several embodiments of the present utility model have been given in this article, those skilled in the art should understand that the embodiments in this article can be changed without departing from the spirit of the present utility model. The above embodiments are only exemplary, and the embodiments in this article should not be used as the limitation of the scope of the rights of the present utility model.

Claims

1. A brine discharge well structure for efficient gas injection and brine discharge in an underground salt cavern for compressed air energy storage, characterized in that, The brine drainage well structure includes a salt cavern and a brine drainage well; The brine drainage well has a three - opened wellbore structure, and the sizes of the first - opened wellbore, the second - opened wellbore, and the third - opened wellbore decrease in sequence. The first - opened well type is a vertical well; the second - opened well type includes a vertical well section and an inclined well section; the third - opened well type includes a first inclined wellbore, a second inclined wellbore, and a third inclined wellbore. The first inclined wellbore, the second inclined wellbore, and the third inclined wellbore communicate with the salt cavern; The first inclined wellbore communicates with a first cavity inlet of the salt cavern, and the first cavity inlet is located above the sediment surface of the salt cavern; the second inclined wellbore communicates with a second cavity inlet of the salt cavern, and the second cavity inlet is located in the middle of the sediment of the salt cavern; the third inclined wellbore communicates with a third cavity inlet of the salt cavern, and the third cavity inlet is located at the bottom of the sediment of the salt cavern; A brine drainage inner main pipe is arranged in the brine drainage well. Three brine drainage inner branch pipes are arranged at the first inclined wellbore, the second inclined wellbore, and the third inclined wellbore of the brine drainage inner main pipe. The three brine drainage inner branch pipes respectively pass through the first inclined wellbore, the second inclined wellbore, and the third inclined wellbore to reach the salt cavern; the three brine drainage inner branch pipes converge into the brine drainage inner main pipe.

2. The brine discharge well structure for efficient gas injection and brine discharge in an underground salt cavern for compressed air energy storage according to claim 1, characterized in that, The casing of the first - opened well is run into the bedrock 20 m below, the casing of the second - opened well is run into the salt layer 30 m below, and the third - opened well has no casing and reaches the salt cavern with an open hole.

3. The brine discharge well structure for efficient gas injection and brine discharge in an underground salt cavern for compressed air energy storage according to claim 1, wherein The first cavity inlet is arranged 2 m above the sediment surface of the salt cavern, the second cavity inlet is arranged at the 1 / 2 depth of the sediment of the salt cavern, and the third cavity inlet is arranged 2 m above the bottom of the sediment of the salt cavern.

4. The brine discharge well structure for efficient gas injection and brine discharge in an underground salt cavern for compressed air energy storage according to claim 1, characterized in that, The sizes of the first inclined wellbore and the third inclined wellbore are both larger than the size of the second inclined wellbore.

5. The brine discharge well structure for efficient gas injection and brine drainage in an underground salt cavern for compressed air energy storage according to claim 1, characterized in that, The horizontal distance from the wellhead of the brine drainage well to the side wall of the salt cavern is not less than 100 m.

6. The brine discharge well structure for efficient gas injection and brine discharge in an underground salt cavern for compressed air energy storage according to claim 1, wherein, The wellbore diameters of the first inclined wellbore and the second inclined wellbore are 177.8 mm, and the wellbore diameter of the second inclined wellbore is 139.7 mm.

7. The brine discharge well structure for efficient gas injection and brine discharge in an underground salt cavern for compressed air energy storage according to claim 1, characterized in that, The second - opened wellbore is provided with a build - up point. The section above the build - up point is a vertical well section, and the section below the build - up point is an inclined well section.

8. The brine discharge well structure for efficient gas injection and brine discharge in an underground salt cavern for compressed air energy storage according to claim 1, wherein The brine drainage inner main pipe is a screen - pipe washing pipe with a diameter of 88.9 mm, and the brine drainage inner branch pipes have a diameter of 73 mm.

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