Anti-clogging method and device for brine discharging well in low-position brine discharging process in salt cavern sediment

Abstract

The invention provides an anti-clogging method and device for a brine discharging well in the low-position brine discharging process in salt cavern sediment. A method for preventing clogging of a brine discharging well in the low-position brine discharging process in salt cavern sediment comprises the steps that S1, gas injection wells and brine discharging wells are drilled on the ground, and the gas injection wells and the brine discharging wells communicate with the top of a salt cavern and the bottom of the salt cavern sediment in a one-to-one correspondence mode; s2, gas injection is conducted on the top of the salt cavity through a gas injection well, so that brine in the salt cavity is discharged through a brine discharging well under the action of gas pressure; s3, fresh water is injected into the open hole section through a central pipe of the brine discharging well, so that salt rocks around the open hole section are corroded by the fresh water; and S4, fresh water injection through the central pipe of the brine discharging well is stopped, and brine discharging is conducted through the central pipe of the brine discharging well and the annulus.

Description

Technical Field

[0001] The invention relates to the technical field of low-position brine drainage in salt cavern sediments, and in particular to a method and device for preventing clogging of a brine drainage well during low-position brine drainage in salt cavern sediments. Background Art

[0002] Salt cavern gas storage is built in lacustrine layered salt rock, which has the characteristics of small salt rock thickness, many interlayers, and high insoluble impurity content. The cavity formed after water dissolution is buried by a large amount of insoluble sediment, resulting in a small effective volume of the storage. For example, the salt cavern cavity space formed by a high-impurity salt mine is completely buried by sediment, and the effective volume is lost.

[0003] Storing gas in sediment gaps can solve the problems of small effective gas storage volume and poor economic efficiency of building a reservoir in high-impurity salt mines, and can significantly increase the effective storage capacity of salt cavern gas storage. The existing technologies for utilizing sediment gaps at the bottom of salt caverns mainly include low-level brine drainage technology and "drilling and drainage integrated gas injection and brine drainage" technology. The low-level brine drainage method can effectively discharge brine from the sediment gaps, but during the low-level brine drainage process, sediment particles often clog the open hole section at the bottom of the brine drainage well, resulting in a decrease in brine drainage flow, affecting the efficiency and progress of brine drainage; the "drilling and drainage integrated" pipe string can be used to penetrate into the sediment, and the brine above the sediment surface is discharged to the ground through the multi-stage repeatable switch sleeve set at the upper part of the pipe string, and then the brine in the sediment and some small-size sediment are discharged to the ground through the soluble patch sand-proof screen set at the lower part of the pipe string, expanding the effective gas storage space of the cavity, but the process has not yet completed field testing. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and device for preventing clogging of a brine discharge well in a process of low-level brine discharge in salt cavern sediment in view of the deficiencies in the prior art.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a method for preventing clogging of a brine discharge well during low-level brine discharge in salt cavern sediment, comprising: S1, drilling a gas injection well and a brine discharge well on the ground, and connecting the gas injection well and the brine discharge well to the top of the salt cavity and the bottom of the salt cavity sediment in a one-to-one correspondence; S2, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S3, injecting fresh water into the open hole section through the central pipe of the brine discharge well, so that the fresh water dissolves the salt rock around the open hole section; S4, stopping the injection of fresh water through the central pipe of the brine discharge well, and discharging brine through the central pipe and annulus of the brine discharge well.

[0006] The beneficial effects of the technical solution of the present invention are as follows: a gas injection well is drilled on the ground to communicate with the top of the salt cavity, a brine drainage well is drilled on the ground to reach the bottom of the salt cavity sediment and communicate, and the brine in the salt cavity is discharged by injecting gas through the gas injection well and draining brine through the brine drainage well. The brine in the salt cavity is displaced by the gas injection pressure of the gas injection well, and the brine passes through the sediment gap and is discharged from the brine drainage well. Fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. The effective brine cross-sectional area of ​​the open hole section is expanded by dissolution, the blockage of sediment particles is reduced, and the brine drainage flow rate is expanded. Stop injecting fresh water into the central pipe of the brine drainage well, and continue to use the central pipe and annulus in the brine drainage well to drain brine at the same time, increase the brine drainage flow rate, and shorten the brine drainage time. During the brine drainage process, fresh water is injected through the central pipe to dissolve the salt rock around the open hole section of the brine drainage well at the junction with the low part of the salt cavity, expand the size of the dissolved cavity of the open hole section, thereby increasing the brine flow area at the bottom of the brine drainage well, and effectively preventing and solving the sediment clogging problem.

[0007] Further, step S2 includes: S21, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S22, obtaining the gas injection pressure; S23, judging whether the gas injection pressure increases; S24, when the gas injection pressure increases, executing step S3.

[0008] The beneficial effect of adopting the above-mentioned further technical solution is: if there is a trend of increasing gas injection pressure, fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water reaches the open hole section directly. Since the buoyancy of fresh water is smaller than that of brine, the fresh water dissolves faster and gradually dissolves the salt rock around the open hole section.

[0009] Further, step S2 includes: S25, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S26, obtaining the brine discharge flow rate; S27, judging whether the brine discharge flow rate is reduced; S28, when the brine discharge flow rate is reduced, executing step S3.

[0010] The beneficial effect of adopting the above-mentioned further technical solution is: if there is a trend of decreasing brine discharge flow, fresh water is injected through the central pipe of the brine discharge well on the ground, so that the fresh water reaches the open hole section directly. Since the buoyancy of fresh water is smaller than that of brine, the fresh water dissolves faster and gradually dissolves the salt rock around the open hole section.

[0011] Furthermore, in step S3, while fresh water is injected into the open hole section through the central pipe of the brine drainage well, gas is continuously injected into the top of the salt cavity through the gas injection well to achieve uninterrupted brine drainage in the annulus of the brine drainage well.

[0012] The beneficial effect of adopting the above further technical solution is: fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. At the same time, the brine drainage well annulus continues to drain brine without stopping the brine drainage process. The downtime of the brine drainage process is reduced, the brine drainage efficiency is increased, and the brine drainage time is shortened.

[0013] Further, step S4 includes: S41, judging whether the brine discharge flow rate is no longer increasing; S42, when the brine discharge flow rate is no longer increasing, stopping injecting fresh water through the central pipe of the brine discharge well, and discharging brine through the central pipe and annulus of the brine discharge well.

[0014] The beneficial effect of adopting the above-mentioned further technical scheme is: when the brine discharge flow rate increases to an appropriate range, the brine discharge flow rate no longer increases, and the sediment particles no longer cause blockage, stop injecting fresh water into the central pipe of the brine discharge well, and continue to use the central pipe and annulus of the brine discharge well to discharge brine at the same time, thereby increasing the brine discharge flow rate and shortening the brine discharge time.

[0015] In addition, the present invention also provides a device for preventing clogging of a brine discharge well during low-position brine discharge in salt cavern sediment, which is used to implement any of the above-mentioned methods for preventing clogging of a brine discharge well during low-position brine discharge in salt cavern sediment. The device for preventing clogging of a brine discharge well during low-position brine discharge in salt cavern sediment comprises: an injection well, a brine discharge well, a salt cavity, and a central pipe. The gas injection well is connected to the top of the salt cavity, the brine discharge well is connected to the bottom of the sediment in the salt cavity, the central pipe is arranged in the brine discharge well, and an annulus is provided between the central pipe and the brine discharge well.

[0016] The beneficial effects of the technical solution of the present invention are as follows: a gas injection well is drilled on the ground to communicate with the top of the salt cavity, a brine drainage well is drilled on the ground to reach the bottom of the salt cavity sediment and communicate, and the brine in the salt cavity is discharged by injecting gas through the gas injection well and draining brine through the brine drainage well. The brine in the salt cavity is displaced by the gas injection pressure of the gas injection well, and the brine passes through the sediment gap and is discharged from the brine drainage well. Fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. The effective brine cross-sectional area of ​​the open hole section is expanded by dissolution, the blockage of sediment particles is reduced, and the brine drainage flow rate is expanded. Stop injecting fresh water into the central pipe of the brine drainage well, and continue to use the central pipe and annulus in the brine drainage well to drain brine at the same time, increase the brine drainage flow rate, and shorten the brine drainage time. During the brine drainage process, fresh water is injected through the central pipe to dissolve the salt rock around the open hole section of the brine drainage well at the junction with the low part of the salt cavity, expand the size of the dissolved cavity of the open hole section, thereby increasing the brine flow area at the bottom of the brine drainage well, and effectively preventing and solving the sediment clogging problem.

[0017] Furthermore, the salt chamber is provided with sediment, brine and gas.

[0018] The beneficial effect of adopting the above further technical solution is that using the sediment gap to store gas can solve the problem of small effective gas storage volume and poor construction economy in high-impurity salt mines, and can significantly increase the effective storage capacity of salt cavern gas storage. When constructing salt cavern gas storage in high-impurity salt mines, the sediment low-level brine drainage technology can effectively discharge the brine in the sediment gap and increase the effective gas storage volume of the salt cavity.

[0019] Furthermore, the connection between the brine drainage well and the salt cavity is an open hole section, and the central pipe is connected to the open hole section.

[0020] The beneficial effect of adopting the above-mentioned further technical scheme is: during the brine drainage process, fresh water is injected through the central pipe to dissolve the salt rock around the open hole section of the brine drainage well at the junction with the low part of the salt cavity, expand the size of the dissolution cavity in the open hole section, thereby increasing the brine flow area at the bottom of the brine drainage well, and effectively preventing and solving the sediment blockage problem.

[0021] Furthermore, the tops of the gas injection well and the brine drainage well are both located above the ground.

[0022] The beneficial effects of adopting the above further technical solution are: facilitating gas injection through the gas injection well, facilitating brine discharge through the brine discharge well, and facilitating injection of fresh water into the open hole section through the central pipe of the brine discharge well.

[0023] Furthermore, a production casing is provided in the brine drainage well, the central pipe is arranged in the production casing, and an annulus is provided between the central pipe and the production casing.

[0024] The beneficial effect of adopting the above further technical solution is: fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. At the same time, the annulus of the brine drainage well continues to drain brine without stopping the brine drainage process. The downtime of the brine drainage process is reduced, the brine drainage efficiency is increased, and the brine drainage time is shortened.

[0025] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a low-level brine removal process in salt cavern sediment provided in an embodiment of the present invention.

[0027] Figure 2 A schematic diagram of fresh water injection in a low-level brine removal process in salt cavern sediment provided in an embodiment of the present invention.

[0028] Figure 3 A schematic diagram of the freshwater dissolution open hole section of the low-level brine drainage process in the salt cavern sediment provided in an embodiment of the present invention.

[0029] Figure 4A schematic diagram of the dissolution and expansion of the open hole section during the low-level brine drainage process in the salt cavern sediment provided in an embodiment of the present invention.

[0030] Figure 5 A schematic block diagram of the steps for implementing the unblocking of the open hole section in the low-level brine drainage process provided by an embodiment of the present invention.

[0031] Figure 6 A schematic block diagram of a method for preventing clogging of a brine discharge well during low-level brine discharge in salt cavern sediment provided in an embodiment of the present invention.

[0032] Explanation of the accompanying figures: 1. Gas injection well; 2. Brine drainage well; 3. Salt cavity; 4. Central pipe; 5. Sediment; 6. Annulus; 7. Brine; 8. Gas; 9. Open hole section; 10. Ground; 11. Production casing; 12. Gas-liquid interface. DETAILED DESCRIPTION

[0033] 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 but not to limit the scope of the present invention.

[0034] like Figure 6 As shown, an embodiment of the present invention provides a method for preventing clogging of a brine drainage well during low-level brine drainage in salt cavern sediment, comprising: S1, drilling a gas injection well and a brine drainage well on the ground, and connecting the gas injection well and the brine drainage well with the top of the salt cavity and the bottom of the salt cavity sediment one by one; S2, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine drainage well under the action of gas pressure; S3, injecting fresh water into the open hole section through the central pipe of the brine drainage well, so that the fresh water dissolves the salt rock around the open hole section; S4, stopping the injection of fresh water through the central pipe of the brine drainage well, and discharging brine through the central pipe and annulus of the brine drainage well.

[0035] The beneficial effects of the technical solution of the present invention are as follows: a gas injection well is drilled on the ground to communicate with the top of the salt cavity, a brine drainage well is drilled on the ground to reach the bottom of the salt cavity sediment and communicate, and the brine in the salt cavity is discharged by injecting gas through the gas injection well and draining brine through the brine drainage well. The brine in the salt cavity is displaced by the gas injection pressure of the gas injection well, and the brine passes through the sediment gap and is discharged from the brine drainage well. Fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. The effective brine cross-sectional area of ​​the open hole section is expanded by dissolution, the blockage of sediment particles is reduced, and the brine drainage flow rate is expanded. Stop injecting fresh water into the central pipe of the brine drainage well, and continue to use the central pipe and annulus in the brine drainage well to drain brine at the same time, increase the brine drainage flow rate, and shorten the brine drainage time. During the brine drainage process, fresh water is injected through the central pipe to dissolve the salt rock around the open hole section of the brine drainage well at the junction with the low part of the salt cavity, expand the size of the dissolved cavity of the open hole section, thereby increasing the brine flow area at the bottom of the brine drainage well, and effectively preventing and solving the sediment clogging problem.

[0036] Storing gas in sediment gaps can solve the problems of small effective gas storage volume and poor construction economy in high-impurity salt mines, and can significantly increase the effective storage capacity of salt cavern gas storage. When constructing salt cavern gas storage in high-impurity salt mines, the sediment low-level brine drainage technology can effectively discharge the brine in the sediment gaps and increase the effective gas storage volume of the salt cavity. However, during the low-level brine drainage process, sediment particles often clog the open-hole section at the bottom of the brine drainage well, resulting in a reduction in the brine drainage flow rate, affecting the brine drainage efficiency and progress. The present invention proposes a method for preventing clogging of brine drainage wells during low-level brine drainage in salt cavern sediments (a method for preventing clogging of brine drainage wells during low-level brine drainage in salt cavern sediments). During the brine drainage process, fresh water is injected through a central pipe to dissolve the salt rock around the open-hole section of the brine drainage well at the junction with the low part of the salt cavity, expand the size of the dissolution cavity of the open-hole section, thereby increasing the brine flow area at the bottom of the brine drainage well, and effectively preventing and solving the sediment clogging problem.

[0037] like Figure 1 As shown, this is a schematic diagram of water injection and expansion of the open hole section of the brine drainage well during the low-level brine drainage process at the bottom of the sediment. Figure 1 The arrow in the figure indicates the direction of brine discharge. A large amount of insoluble sediment particles are accumulated at the bottom of the high-impurity salt cavity. During the gas injection and brine discharge process, the brine reaches the open hole section at the bottom of the brine discharge well through the sediment gap and is discharged through the brine discharge well.

[0038] Drill a gas injection well on the ground to connect with the top of the salt cavity, drill a brine drainage well on the ground to reach the bottom of the salt cavity sediment and drain the brine in the salt cavity by injecting gas through the gas injection well and draining brine through the brine drainage well. The brine in the salt cavity is displaced by the gas injection pressure of the gas injection well, and the brine passes through the gaps in the sediment and is discharged from the brine drainage well.

[0039] like Figure 2 As shown, fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. At the same time, the brine is continuously discharged from the annulus of the brine drainage well without stopping the brine drainage process. Figure 2 One of the arrows is the direction of brine discharge, and the other is the direction of fresh water injection.

[0040] like Figure 3 As shown, the effective brine cross-sectional area of ​​the open hole section is expanded by dissolution, the clogging of sediment particles is reduced, and the brine discharge flow rate is increased. Figure 3 One of the arrows is the direction of brine discharge, and the other is the direction of fresh water injection.

[0041] like Figure 4 As shown, stop injecting fresh water into the central pipe of the brine drainage well, continue to use the central pipe and annulus to drain brine simultaneously in the brine drainage well, increase the brine drainage flow rate, and shorten the brine drainage time. Figure 4 The arrow in the figure indicates the direction of brine discharge.

[0042] like Figure 5 As shown, the on-site implementation steps for the expansion and dissolution of the open hole section during the low-level brine drainage process.

[0043] 1. Drill a gas injection well on the ground to connect it to the top of the salt cavity, drill a brine drainage well to the bottom of the salt cavity sediment, and use the gas injection well to inject gas and the brine drainage well to drain brine. 2. The brine in the salt cavity is displaced by the gas injection pressure of the gas injection well, and the brine passes through the sediment gap and is discharged from the brine drainage well. 3. Inject fresh water through the central pipe of the brine drainage well on the ground to the open hole section, and the fresh water dissolves the salt rock around the open hole section. 4. Dissolution expands the effective brine cross-sectional area of ​​the open hole section, relieves the blockage of sediment particles, and increases the brine drainage flow rate. 5. Continue to use the central pipe and annulus in the brine drainage well to drain brine at the same time, increase the brine drainage flow rate, and shorten the brine drainage time.

[0044] Further, step S2 includes: S21, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S22, obtaining the gas injection pressure; S23, judging whether the gas injection pressure increases; S24, when the gas injection pressure increases, executing step S3.

[0045] The beneficial effect of adopting the above-mentioned further technical solution is: if there is a trend of increasing gas injection pressure, fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water reaches the open hole section directly. Since the buoyancy of fresh water is smaller than that of brine, the fresh water dissolves faster and gradually dissolves the salt rock around the open hole section.

[0046] Further, step S2 includes: S25, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S26, obtaining the brine discharge flow rate; S27, judging whether the brine discharge flow rate is reduced; S28, when the brine discharge flow rate is reduced, executing step S3.

[0047] The beneficial effect of adopting the above-mentioned further technical solution is: if there is a trend of decreasing brine discharge flow, fresh water is injected through the central pipe of the brine discharge well on the ground, so that the fresh water reaches the open hole section directly. Since the buoyancy of fresh water is smaller than that of brine, the fresh water dissolves faster and gradually dissolves the salt rock around the open hole section.

[0048] Furthermore, in step S3, while fresh water is injected into the open hole section through the central pipe of the brine drainage well, gas is continuously injected into the top of the salt cavity through the gas injection well to achieve uninterrupted brine drainage in the annulus of the brine drainage well.

[0049] The beneficial effect of adopting the above further technical solution is: fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. At the same time, the brine drainage well annulus continues to drain brine without stopping the brine drainage process. The downtime of the brine drainage process is reduced, the brine drainage efficiency is increased, and the brine drainage time is shortened.

[0050] Further, step S4 includes: S41, judging whether the brine discharge flow rate is no longer increasing; S42, when the brine discharge flow rate is no longer increasing, stopping injecting fresh water through the central pipe of the brine discharge well, and discharging brine through the central pipe and annulus of the brine discharge well.

[0051] The beneficial effect of adopting the above-mentioned further technical scheme is: when the brine discharge flow rate increases to an appropriate range, the brine discharge flow rate no longer increases, and the sediment particles no longer cause blockage, stop injecting fresh water into the central pipe of the brine discharge well, and continue to use the central pipe and annulus of the brine discharge well to discharge brine at the same time, thereby increasing the brine discharge flow rate and shortening the brine discharge time.

[0052] ① Figure 1 As shown, ground drilling is carried out, the gas injection well is connected to the top of the salt cavity, and the brine drainage well is connected to the bottom of the salt cavity sediment. The gas injection well is used to inject gas at the top of the salt cavity, and the gas gradually fills the top of the salt cavity. Under the action of gas pressure, brine passes through the gaps in the sediment and is gradually discharged from the brine drainage well.

[0053] ② Figure 2 As shown in the figure, if there is a trend of increasing gas injection pressure and decreasing brine discharge flow, fresh water is injected through the central pipe of the brine discharge well on the ground to allow the fresh water to reach the open hole section directly. Since the buoyancy of fresh water is smaller than that of brine, the fresh water dissolves faster and gradually dissolves the salt rock around the open hole section. At the same time, continue to use the method of injecting gas in the gas injection well and discharging brine from the annulus of the brine discharge well to discharge brine uninterruptedly, and continuously dissolve and expand the effective brine-passing area of ​​the open hole section.

[0054] ③ Figure 3 As shown, by continuously injecting fresh water and continuously dissolving the cross-sectional area of ​​the cavity of the open hole section, the effective brine cross-sectional area of ​​the open hole section is significantly expanded, the blockage of sediment particles at the bottom of the brine drainage well and the open hole section is cleared, and the brine drainage flow rate is expanded.

[0055] ④ Figure 4 As shown, when the brine discharge flow rate increases to an appropriate range, the brine discharge flow rate no longer increases, and the sediment particles no longer cause blockage, stop injecting fresh water into the central pipe of the brine discharge well, and continue to use the central pipe and annulus of the brine discharge well to discharge brine simultaneously, thereby increasing the brine discharge flow rate and shortening the brine discharge time.

[0056] The embodiments of the present invention increase the brine flow area at the bottom of the brine drainage well, and effectively prevent and solve the sediment blockage problem, by designing a method for injecting gas at the top of the salt cavity and a low-position brine drainage well, a method for expanding and dissolving the open hole section by injecting fresh water into the central pipe of the brine drainage well, and an uninterrupted brine drainage method by injecting fresh water into the central pipe of the brine drainage well and draining brine from the annulus.

[0057] Advantages of this method: The present invention adopts the method of draining brine from the bottom of the brine drainage well sediment to discharge the brine in the sediment gap, effectively expanding the effective gas storage volume of the salt cavern gas storage. After adopting this method, the salt cavity space utilization rate reaches 80%-90%. The central pipe of the brine drainage well is used to inject fresh water to dissolve the open hole section of the brine drainage well, effectively expanding the brine drainage cross-sectional area of ​​the open hole section, preventing the clogging of sediment particles caused by the narrowness of the open hole section, and effectively alleviating the clogging of sediment particles by dissolving the surrounding salt rock at the open hole section with fresh water. At the same time, during the unblocking process using this method, the brine drainage of the brine drainage well is not stopped, and the annulus of the brine drainage well continues to discharge brine, reducing the downtime of the brine drainage process, increasing the brine drainage efficiency, and shortening the brine drainage time.

[0058] like Figures 1 to 4 As shown, in addition, the present invention also provides a device for preventing clogging of a brine discharge well during low-position brine discharge in salt cavern sediment, which is used to implement any one of the above-mentioned methods for preventing clogging of a brine discharge well during low-position brine discharge in salt cavern sediment, and the device for preventing clogging of a brine discharge well during low-position brine discharge in salt cavern sediment comprises: an injection well 1, a brine discharge well 2, a salt cavity 3, and a central pipe 4, the gas injection well 1 is connected to the top of the salt cavity 3, the brine discharge well 2 is connected to the bottom of the sediment 5 in the salt cavity 3, the central pipe 4 is arranged in the brine discharge well 2, and an annulus 6 is provided between the central pipe 4 and the brine discharge well 2.

[0059] The beneficial effects of the technical solution of the present invention are as follows: a gas injection well is drilled on the ground to communicate with the top of the salt cavity, a brine drainage well is drilled on the ground to reach the bottom of the salt cavity sediment and communicate, and the brine in the salt cavity is discharged by injecting gas through the gas injection well and draining brine through the brine drainage well. The brine in the salt cavity is displaced by the gas injection pressure of the gas injection well, and the brine passes through the sediment gap and is discharged from the brine drainage well. Fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. The effective brine cross-sectional area of ​​the open hole section is expanded by dissolution, the blockage of sediment particles is reduced, and the brine drainage flow rate is expanded. Stop injecting fresh water into the central pipe of the brine drainage well, and continue to use the central pipe and annulus in the brine drainage well to drain brine at the same time, increase the brine drainage flow rate, and shorten the brine drainage time. During the brine drainage process, fresh water is injected through the central pipe to dissolve the salt rock around the open hole section of the brine drainage well at the junction with the low part of the salt cavity, expand the size of the dissolved cavity of the open hole section, thereby increasing the brine flow area at the bottom of the brine drainage well, and effectively preventing and solving the sediment clogging problem.

[0060] like Figures 1 to 4 As shown, further, the salt chamber 3 is provided with sediment 5, brine 7 and gas 8.

[0061] The beneficial effect of adopting the above further technical solution is that using the sediment gap to store gas can solve the problem of small effective gas storage volume and poor construction economy in high-impurity salt mines, and can significantly increase the effective storage capacity of salt cavern gas storage. When constructing salt cavern gas storage in high-impurity salt mines, the sediment low-level brine drainage technology can effectively discharge the brine in the sediment gap and increase the effective gas storage volume of the salt cavity.

[0062] Among them, above the brine 7 is the gas-liquid interface 12 .

[0063] like Figures 1 to 4 As shown, further, the connection between the brine drainage well 2 and the salt cavity 3 is an open hole section 9, and the central pipe 4 is connected to the open hole section 9.

[0064] The beneficial effect of adopting the above-mentioned further technical scheme is: during the brine drainage process, fresh water is injected through the central pipe to dissolve the salt rock around the open hole section of the brine drainage well at the junction with the low part of the salt cavity, expand the size of the dissolution cavity in the open hole section, thereby increasing the brine flow area at the bottom of the brine drainage well, and effectively preventing and solving the sediment blockage problem.

[0065] like Figures 1 to 4 As shown, further, the tops of the gas injection well 1 and the brine drainage well 2 are both located above the ground 10 .

[0066] The beneficial effects of adopting the above further technical solution are: facilitating gas injection through the gas injection well, facilitating brine discharge through the brine discharge well, and facilitating injection of fresh water into the open hole section through the central pipe of the brine discharge well.

[0067] like Figures 1 to 4 As shown, further, a production casing 11 is provided in the brine drainage well 2 , the central pipe 4 is arranged in the production casing 11 , and an annulus 6 is provided between the central pipe 4 and the production casing 11 .

[0068] The beneficial effect of adopting the above further technical solution is: fresh water is injected through the central pipe of the brine drainage well on the ground, so that the fresh water directly reaches the open hole section and dissolves the salt rock around the open hole section. At the same time, the annulus of the brine drainage well continues to drain brine without stopping the brine drainage process. The downtime of the brine drainage process is reduced, the brine drainage efficiency is increased, and the brine drainage time is shortened.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preventing clogging of brine discharge wells during low-level brine discharge in salt cave sediments. It is characterized in that include: S1. Drill gas injection wells and brine drainage wells on the ground, and connect the gas injection wells and brine drainage wells to the top of the salt cavity and the bottom of the salt cavity sediment one by one; S2, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S3, injecting fresh water into the open hole section through the central pipe of the brine drainage well, so that the fresh water dissolves the salt rock around the open hole section; S4. Stop injecting fresh water through the central pipe of the brine discharge well, and discharge brine through the central pipe and annulus of the brine discharge well.

2. The method for preventing clogging of brine discharge wells during low-level brine discharge in salt cave sediment according to claim 1, It is characterized in that Step S2 includes: S21, injecting gas into the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S22, obtaining gas injection pressure; S23, determining whether the gas injection pressure increases; S24. When the gas injection pressure increases, execute step S3.

3. The method for preventing clogging of brine discharge wells during low-level brine discharge in salt cave sediment according to claim 1, It is characterized in that Step S2 includes: S25, injecting gas at the top of the salt cavity through the gas injection well, so that the brine in the salt cavity is discharged from the brine discharge well under the action of gas pressure; S26, obtaining the brine discharge flow rate; S27, judging whether the brine discharge flow rate is reduced; S28. When the brine discharge flow rate decreases, execute step S3.

4. The method for preventing clogging of brine discharge wells during low-level brine discharge in salt cave sediment according to claim 1, It is characterized in that In step S3, while fresh water is injected into the open hole section through the central pipe of the brine drainage well, gas is continuously injected into the top of the salt cavity through the gas injection well to achieve uninterrupted brine drainage in the annulus of the brine drainage well.

5. The method for preventing clogging of brine discharge wells during low-level brine discharge in salt cave sediment according to claim 1, It is characterized in that Step S4 includes: S41, judging whether the brine discharge flow rate is no longer increasing; S42. When the brine discharge flow rate no longer increases, stop injecting fresh water through the central pipe of the brine discharge well, and discharge the brine through the central pipe and annulus of the brine discharge well.

6. A device for preventing clogging of brine wells during low-level brine discharge in salt cave sediments. It is characterized in that Used to implement a method for preventing clogging of a brine discharge well during low-level brine discharge in salt cavern sediment as described in any one of claims 1 to 5, the device for preventing clogging of a brine discharge well during low-level brine discharge in salt cavern sediment comprises: an injection well, a brine discharge well, a salt cavity, and a central pipe, the injection well being connected to the top of the salt cavity, the brine discharge well being connected to the bottom of the sediment in the salt cavity, the central pipe being disposed in the brine discharge well, and an annulus being provided between the central pipe and the brine discharge well.

7. The device for preventing clogging of brine discharge wells in the process of low-level brine discharge in salt cave sediment according to claim 6, It is characterized in that The salt cavity is provided with sediment, brine and gas.

8. The device for preventing clogging of brine discharge wells in the process of low-level brine discharge in salt cave sediment according to claim 6, It is characterized in that The connection between the brine drainage well and the salt cavity is an open hole section, and the central pipe is connected to the open hole section.

9. The device for preventing clogging of brine discharge wells in the process of low-level brine discharge in salt cave sediment according to claim 6, It is characterized in that The tops of the gas injection well and the brine drainage well are both located above the ground.

10. The device for preventing clogging of brine discharge wells in the process of low-level brine discharge in salt cave sediment according to claim 6, It is characterized in that A production casing is provided in the brine drainage well, the central pipe is arranged in the production casing, and an annulus is provided between the central pipe and the production casing.

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