A method for creating a cavity for a salt cavern gas storage without blocking solvent

Abstract

The application discloses a salt cavern gas storage cavity forming method without blocking solvent, which comprises the following steps: firstly, drilling four communicating horizontal wells, then drilling a vertical well in the center of the horizontal well and connecting the vertical well with the horizontal well; lowering a vertical well outer pipe and two cavity forming inner pipes with different depths and capable of spraying nozzles in all directions into the vertical well, then taking the vertical well outer pipe as a gas injection pipe, lowering a cavity forming outer pipe and a water filtering pipe with a filter screen into the horizontal well; then, starting to build a groove and dissolve a cavity; injecting fresh water and filtered brine into the two cavity forming inner pipes through the vertical well, then sucking the brine out through the water filtering pipe and filtering, repeatedly injecting into the cavity forming inner pipes, controlling the cavity shape by controlling the water injection type of the cavity forming inner pipes, and repeating the process for multiple times until the final cavity forming is completed; finally, injecting natural gas into the vertical well outer pipe to maintain the cavity pressure. The application can solve the problems of cavity pollution and difficulty in monitoring and controlling caused by blocking solvent.

Description

Technical Field

[0001] This invention relates to the field of salt cavern gas storage cavity construction technology, specifically to a method for salt cavern gas storage cavity construction without the need for solvent inhibitors. Background Technology

[0002] With the increasing demand for energy such as natural gas and hydrogen in my country, as well as the need for national strategic reserves, the construction of gas storage facilities is accelerating. Salt cavern gas storage facilities possess advantages such as high safety (the salt rock does not react with waste or the storage medium, resulting in good stability), high injection and production efficiency, and large working gas volume, offering significant advantages in peak-shaving gas supply and flexible storage. Therefore, existing salt cavern gas storage facilities have great development potential.

[0003] However, during the salt cavern construction process, the high-concentration brine concentrates in the lower part and the low-concentration brine concentrates in the upper part. This easily leads to rapid dissolution of the upper salt rock, causing uncontrollable development of the cavity. Therefore, solvent inhibitors are added during the cavity construction process. Commonly used solvent inhibitors are oil and gas, such as diesel and nitrogen. Oil as a solvent can easily contaminate the salt cavern, posing a potential hazard for later normal use; while gaseous solvent inhibitors cause less contamination, they are compressible and difficult to control and monitor. Therefore, providing a salt cavern construction method that does not require solvent inhibitors has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a method for creating a salt cavern gas storage chamber without the need for solvent inhibitors, which can solve problems such as contamination of the chamber and difficulty in monitoring and control caused by solvent inhibitors.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a method for creating a salt cavern gas storage tank without the need for solvent inhibitors, comprising the following steps:

[0007] S1. Drill four horizontal wells of equal depth arranged in a square array, and the horizontal wells must reach the same layer. They are labeled as horizontal well number one to horizontal well number four in a clockwise direction.

[0008] S2. Drill vertical wells of equal depth at the center of the square array. The bottoms of horizontal well No. 1, horizontal well No. 3, and vertical wells are connected; the bottoms of horizontal well No. 2, horizontal well No. 4, and vertical wells are connected.

[0009] S3. A vertical well outer pipe is installed in the vertical well. Pipe No. 1 and pipe No. 2 with different bottom heights are installed inside the vertical well outer pipe. Pipe No. 1 and pipe No. 2 together form the cavity inner pipe. An air injection hole is provided at the upper end of the vertical well outer pipe. The cavity inner pipe is connected to an external water injection device.

[0010] S4. Adjust the water injection pressure of the water injection equipment. The water injection pressure should not be less than the formation pressure, and the water injection pressure should be adjusted in a timely manner according to the cavity diameter.

[0011] S5. A cavity-making outer tube is lowered into the horizontal well, and several evenly distributed water intake ports are opened on the cavity-making outer tube in the horizontal section.

[0012] S6. A filter pipe is inserted into the outer tube of the cavity, and the horizontal section of the filter pipe has a honeycomb-shaped filter port.

[0013] S7. Inject fresh water into both pipe 1 and pipe 2 of the vertical well. The water pressure should be higher than the formation pressure and adjusted according to the required range. Then construct the trench.

[0014] S8. After the initial tank is completed, stop water injection and promptly suck out the brine in the cavity through the water inlet and filter pipe of the outer pipe of the horizontal section cavity. At this time, two small cavities arranged vertically are formed at the lower end of the vertical well.

[0015] S9. After the brine is filtered out, fresh water is still injected into pipes 1 and 2 to start cavity building; and the brine is discharged in time through the horizontal well at the bottom, and the discharged insoluble matter is filtered off on the surface. Fresh water is always injected into pipes 1 and 2, so the cavity building speed of the lower cavity will be faster than that of the upper cavity.

[0016] S10. When the lower cavity is half completed, that is, when the cavity diameter reaches half of the designed cavity, fresh water is injected into pipe No. 1 and filtered brine is injected into pipe No. 2.

[0017] S11. When the upper and lower cavities are consistent, repeat steps seven, eight, nine, and ten until the salt cavern cavity meets the design requirements.

[0018] S12. Natural gas is injected through the external pipe of the vertical well to maintain the pressure balance inside the cavity, and at the same time, the brine inside the cavity is drained.

[0019] Preferably, the distance between horizontal well No. 1 and horizontal well No. 3, and between horizontal well No. 2 and horizontal well No. 4, shall not exceed 20m.

[0020] Preferably, the bottom of pipe No. 1 and pipe No. 2 are no more than 15m apart in vertical height.

[0021] Preferably, in step S10, fresh water and brine are repeatedly injected into pipes one and two to control the shape of the upper and lower cavities; the brine comes from the previously filtered fresh water in the cavity, and the steps include:

[0022] a. The brine after melting in the cavity is collected at the bottom of the cavity and undergoes preliminary filtration through the cavity-forming tube and the water filter tube. Then, the preliminarily filtered brine is sucked out.

[0023] b. Set up a filtration station on the surface for further filtration to ensure that the solution can be injected into the No. 1 and No. 2 pipes of the vertical well.

[0024] Preferably, a suction port with a diameter of not less than 60 mm is opened every 2 m of the external tube of the cavity in the horizontal section, and the diameter of the external tube of the cavity is greater than or equal to 100 mm.

[0025] The beneficial effects of this invention are as follows: This method effectively dissolves the cavity by injecting water into a vertical well and drawing brine from a horizontal well. On the one hand, it solves the problems of traditional cavity-making methods, such as the need for solvents and the resulting pollution, difficulty in control and monitoring. On the other hand, it solves the problem of difficulty in controlling the cavity morphology caused by traditional cavity-making methods. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a location distribution diagram of horizontal and vertical wells provided in an embodiment of the present invention;

[0028] Figure 2 This is a sectional view of the location of a horizontal well and a vertical well provided in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of the straight well outer pipe, pipe No. 1, and pipe No. 2 provided in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the upper opening of a horizontal well provided in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the upper opening of a vertical well provided in an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the downhole structure provided in an embodiment of the present invention;

[0033] Figure 7 This is a schematic diagram of the cavity-forming tube structure provided in an embodiment of the present invention;

[0034] Figure 8 This is a schematic diagram of the water filter pipe structure provided in an embodiment of the present invention;

[0035] Figure 9 This is a schematic diagram of the nozzle structure provided in an embodiment of the present invention;

[0036] Figure 10This is a schematic diagram of the downhole structure during the trenching phase provided in an embodiment of the present invention;

[0037] Figure 11 This is a schematic diagram of the intermediate stage of the solution cavity provided in an embodiment of the present invention;

[0038] Figure 12 This is a schematic diagram of the intermediate stage of the solution cavity provided in an embodiment of the present invention;

[0039] Figure 13 This is a schematic diagram illustrating the completion of the melting cavity in an embodiment of the present invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. Horizontal Well No. 1, 2. Horizontal Well No. 2, 3. Horizontal Well No. 3, 4. Horizontal Well No. 4, 5. Vertical Well, 6. Salt Rock Overlying Formation, 7. Salt Rock, 8. Pipe No. 1, 9. Pipe No. 2, 10. Water Inlet of Pipe No. 1, 11. Water Inlet of Pipe No. 2, 13. External Pipe of Vertical Well, 12. Gas Inlet, 14. External Pipe of Cavity, 15. Water Inlet of External Pipe, 16. Filter Pipe, 25. Nozzle, 26. Nozzle, 27. Spray Mouth. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] like Figures 1 to 13 As shown, this embodiment of the invention provides a method for creating a salt cavern gas storage tank without the need for solvent inhibitors, comprising the following steps:

[0044] The first step is to drill four horizontal wells arranged in a square array, with each well reaching the same stratum. These wells are designated as Horizontal Well 1, Horizontal Well 2, Horizontal Well 3, and Horizontal Well 4. The wells will pass through the overlying salt rock strata 6 and 7. Each well will be 800m deep and there will be no interlayers within the salt rock strata. The distance between Horizontal Well 1 and Horizontal Well 3, and between Horizontal Well 2 and Horizontal Well 4, will be 30m.

[0045] The second step is to drill a vertical well 5 with a depth of 800m in the center of the four horizontal wells. The bottom of the first horizontal well 1 and the third horizontal well 3 are connected to the bottom of the vertical well 5. The bottom of the second horizontal well 2 and the fourth horizontal well 4 are connected to the bottom of the vertical well 5. Then, the outer pipe 13 of the vertical well is lowered to a depth of 750m.

[0046] Both the horizontal well and the vertical well 5 are designed with three sections. The diameter of the first section of the horizontal well is 580mm, the diameter of the second section is 360mm, and the diameter of the third section is 180mm. The diameter of the first section of the vertical well is 1400mm, the diameter of the second section is 1100mm, and the diameter of the third section is 800mm.

[0047] The third step involves lowering pipe 8 and pipe 9 into the outer pipe 13 of the vertical well. Pipe 8 is lowered to a depth of 780m, and pipe 9 is lowered to a depth of 790m. The bottom outlets of pipe 8 and pipe 9 are equipped with nozzles that can spray in all directions. The height difference between the two nozzles is 10m. The nozzle diameter is 100mm, the water outlet diameter is 5mm, and the nozzle 26 of the nozzle 25 is circular. The nozzle is equipped with several nozzles 27 arranged in a ring.

[0048] The vertical well outer pipe 13 is then used as the gas injection pipe, with a gas injection port 12 on it. It is connected to the natural gas pool via a pipeline, but the pipeline valve is closed. Pipes 8 and 9 are both 200mm in diameter, with water injection ports on pipes 8 and 9 having a diameter of 30mm, and gas injection port 12 having a diameter of 40mm. Both pipes 8 and 9 are connected to external water injection equipment.

[0049] The fourth step is to adjust the water injection pressure. The salt rock mine is located 800m underground, and the water injection pressure cannot be less than the formation pressure or formation pore pressure, that is, the water pressure at the same depth. The density of water is taken as 1000kg / m3. Therefore, the formation pressure at point 8 of pipe No. 1 is not less than 7.8MPa, and the formation pressure at point 9 of pipe No. 2 is not less than 7.9MPa.

[0050] Therefore, for pipe 8 (No. 1), the combined weight of the water column and the surface injection pressure must be greater than 7.8 MPa, while for pipe 9 (No. 2), it must be greater than 7.9 MPa. Simultaneously, the water pressure is adjusted according to the cavity diameter. To minimize the impact of gravity and ensure that the height of the plane containing the maximum cavity diameter is no more than 0.5 m above the nozzle (meaning the water must contact the cavity wall and dissolve within 0.5 m of descent), the water pressure increases by 0.2 MPa for every meter increase in cavity diameter to ensure successful cavity dissolution.

[0051] The fifth step is to run the cavity-making outer tube 14 into the horizontal well, and to open a 60mm diameter water inlet 15 every 2m of the cavity-making outer tube 14 in the horizontal section. The diameter of the cavity-making outer tube is 100mm.

[0052] Step 6: Insert a filter pipe 16 into the outer tube 14 of the horizontal well. The filter pipe 16 has a diameter of 60mm and a filter hole with a diameter of 10mm on the horizontal section.

[0053] Step 7: Inject fresh water into both pipe 8 and pipe 9 of vertical well 5 and begin trenching. Pipe 8 is equipped with pipe 1 water inlet 10 and pipe 9 is equipped with pipe 2 water inlet 11.

[0054] Step 8: After the initial tank is completed, stop water injection and promptly extract and discharge the brine in the cavity through the water intake port 15 of the inner and outer pipes of the lower horizontal well and the filter hole of the filter pipe 16. The upper end of the filter pipe 16 is equipped with a water intake port; at this time, two small cavities distributed vertically are formed at the bottom of the vertical well 5.

[0055] In the ninth step, the pump body is connected to the filter pipe 16 to pump water, filter and suck out the brine, and fresh water is still injected into the No. 1 pipe 8 and No. 2 pipe 9 of the vertical well to start cavity building; and the brine is discharged in time through the cavity building outer pipe 14 and filter pipe 16 of the bottom horizontal well, and the insoluble matter extracted at the surface is injected into the No. 1 pipe 8; fresh water is always injected into the No. 2 pipe 9; in this way, the cavity building speed of the lower cavity will be faster than that of the upper cavity.

[0056] Step 10: When the lower cavity is half completed, i.e., the cavity diameter reaches 15m, fresh water is injected into pipe 8 and filtered brine is injected into pipe 9.

[0057] Step 11: Once the upper and lower cavities are aligned, repeat steps 7, 8, 9, and 10 until the diameter of the salt cavern reaches 30m and the diameters of the upper and lower cavities are basically the same, thus completing the cavity construction.

[0058] The twelfth step involves real-time monitoring of the cavity pressure using a pressure gauge. Natural gas is injected into the cavity through the vertical well outer pipe 13 as needed to maintain pressure balance, while simultaneously draining the brine. Unlike traditional bottom-up cavity construction methods, this method involves simultaneous top and bottom formation. The horizontal well is only used to drain the brine, while fresh water is injected into the cavity through the vertical well. The brine produced throughout the process is promptly drained, eliminating the need for an inhibitor.

[0059] The salt cavern cavity-forming method proposed in this embodiment solves the problem of solvent inhibition by injecting water into the cavity through a vertical well and draining water through a horizontal well to limit the cavity formation. Furthermore, it forms cavities simultaneously from both the top and bottom, shortening the construction time for cavity formation.

[0060] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for creating a cavity in a salt cavern gas storage tank without the need for an inhibitor, characterized in that, Includes the following steps: S1. Drill four horizontal wells of equal depth arranged in a square array, and the horizontal wells must reach the same layer. They are labeled as horizontal well number one to horizontal well number four in a clockwise direction. S2. Drill vertical wells of equal depth at the center of the square array. The bottoms of horizontal well No. 1, horizontal well No. 3, and vertical wells are connected; the bottoms of horizontal well No. 2, horizontal well No. 4, and vertical wells are connected. S3. A vertical well outer pipe is installed in the vertical well. Pipe No. 1 and pipe No. 2 with different bottom heights are installed inside the vertical well outer pipe. Pipe No. 1 and pipe No. 2 together form the cavity inner pipe. An air injection hole is provided at the upper end of the vertical well outer pipe. The cavity inner pipe is connected to an external water injection device. S4. Adjust the water injection pressure of the water injection equipment. The water injection pressure should not be less than the formation pressure, and the water injection pressure should be adjusted in a timely manner according to the cavity diameter. S5. A cavity-making outer tube is lowered into the horizontal well, and several evenly distributed water intake ports are opened on the cavity-making outer tube in the horizontal section. S6. A filter pipe is inserted into the outer tube of the cavity, and the horizontal section of the filter pipe has a honeycomb-shaped filter port. S7. Inject fresh water into both pipe 1 and pipe 2 of the vertical well. The water pressure should be higher than the formation pressure and adjusted according to the required range. Then construct the trench. S8. After the initial tank is completed, stop water injection and promptly suck out the brine in the cavity through the water inlet and filter pipe of the outer pipe of the horizontal section cavity. At this time, two small cavities arranged vertically are formed at the lower end of the vertical well. S9. After the brine is filtered out, fresh water is still injected into pipes 1 and 2 to start cavity building; and the brine is discharged in time through the horizontal well at the bottom, and the discharged insoluble matter is filtered off on the surface. Fresh water is always injected into pipes 1 and 2, so the cavity building speed of the lower cavity will be faster than that of the upper cavity. S10. When the lower cavity is half completed, that is, when the cavity diameter reaches half of the designed cavity, fresh water is injected into pipe No. 1 and filtered brine is injected into pipe No.

2. S11. When the upper and lower cavities are consistent, repeat steps seven, eight, nine, and ten until the salt cavern cavity meets the design requirements. S12. Natural gas is injected through the external pipe of the vertical well to maintain the pressure balance inside the cavity, and at the same time, the brine inside the cavity is drained.

2. The method for creating a salt cavern gas storage tank without solvent inhibition as described in claim 1, characterized in that, The distance between horizontal well No. 1 and horizontal well No. 3, and between horizontal well No. 2 and horizontal well No. 4, shall not exceed 20m.

3. The method for creating a salt cavern gas storage tank without solvent inhibition as described in claim 1, characterized in that, The vertical height difference between the bottom of pipe No. 1 and pipe No. 2 does not exceed 15m.

4. The method for creating a salt cavern gas storage tank without solvent inhibition as described in claim 1, characterized in that, In step S10, fresh water and brine are injected back and forth through pipes one and two to control the shape of the upper and lower cavities. Its brine comes from previously filtered fresh water from the melting chamber, and the steps include: a. The brine after melting in the cavity is collected at the bottom of the cavity and undergoes preliminary filtration through the cavity-forming tube and the water filter tube. Then, the preliminarily filtered brine is sucked out. b. Set up a filtration station on the surface for further filtration to ensure that the solution can be injected into the No. 1 and No. 2 pipes of the vertical well.

5. The method for creating a salt cavern gas storage tank without solvent inhibition as described in claim 1, characterized in that, Every 2m along the horizontal section of the ostomy tube, a suction port with a diameter of not less than 60mm is opened, and the diameter of the ostomy tube is greater than or equal to 100mm.

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