A method for controlling the dissolution of a gas-solid mixed dissolving layer

Abstract

The application belongs to the technical field of salt cavern cavity forming, and particularly relates to a method for controlling upper dissolution of a gas-solid mixed dissolution-resistant layer. The method comprises a nitrogen gas dissolution-resistant layer, a solid particle cushion layer and a cavity forming string. The solid particle cushion layer is suspended and covered at the bottom of the nitrogen gas dissolution-resistant layer, and the solid particle cushion layer comprises a plurality of solid particle floating balls. The bottom end of the cavity forming string penetrates the gas-solid mixed dissolution-resistant layer and extends into a dissolution cavity. The application is used to solve the problem of unstable gas dissolution-resistant layer and influence on the upper dissolution control effect.

Description

Technical Field

[0001] This invention belongs to the field of salt cavern technology, specifically relating to a method for controlling the dissolution of a gas-solid mixed anti-solution layer. Background Technology

[0002] In the water-soluble mining of underground salt mines, the dissolution of the soluble substances is faster at the top than at the sides or bottom. Excessive upward dissolution is detrimental to the planned control of the shape and volume of the solution cavity during the mining of the bottom salt mines and the construction of gas storage facilities in salt caverns. Therefore, both domestically and internationally, oil-cushion or gas-cushion methods are commonly used. This involves injecting oil or gas, which is lighter than water, to form an inhibitory layer at the top of the brine, preventing the brine from reacting with the upper salt layer. This achieves the goal of controlling upward dissolution during salt mine mining and salt cavern construction.

[0003] The oil-cushion method has been used for a long time, and its process is simple and mature. Diesel fuel exhibits stable solubility barrier properties and good continuity, making it the mainstream method for cavity construction in salt cavern gas storage facilities both domestically and internationally. In recent years, due to the value of brine, environmental requirements, and the difficulty of oil-water separation, coupled with the fact that gas costs significantly less than diesel fuel, the air-cushion method has shown a trend of replacing the oil-cushion method. However, compared to the oil-cushion method, the gas barrier layer in the air-cushion method is more susceptible to pressure fluctuations, exhibiting an inherent disadvantage of an unstable gas-water interface, which severely affects the solubility control effect; while excessive gas injection increases operating costs. Therefore, the instability of the gas barrier layer affecting the solubility control effect is a technical pain point in air-cushion cavity construction, severely restricting the large-scale application of the air-cushion process in salt cavern gas storage facility cavity construction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a gas-solid mixed anti-solution layer and a method for controlling the dissolution on the surface, so as to solve the problem that the gas anti-solution layer is unstable and affects the dissolution control effect.

[0005] On the one hand, the technical solution of the present invention to solve the above-mentioned technical problems is as follows: a gas-solid mixed solution-inhibiting layer, comprising: a nitrogen solution-inhibiting layer;

[0006] A solid particle pad layer is suspended and covers the bottom of the nitrogen gas barrier layer, and the solid particle pad layer includes a number of solid particle floats.

[0007] The cavity-forming column extends into the cavity through the gas-solid mixed solvent-resistant layer at its bottom end.

[0008] Furthermore, the nitrogen concentration in the nitrogen barrier layer is not less than 95%, which is used to inhibit the upward dissolution of the brine below.

[0009] Furthermore, the thickness of the nitrogen gas barrier layer is 10~20cm.

[0010] Furthermore, the solid particle float has a specific gravity of 0.2~0.8, a particle size of 2~25mm, and a pressure resistance range of 10~30MPa.

[0011] Furthermore, the thickness of the solid particle pad layer is not less than 2 cm.

[0012] Furthermore, the thickness of the gas-solid hybrid solvent-resistant layer is 12~20cm.

[0013] Furthermore, the brine outlet at the bottom of the outer tube of the cavity is 5-10m away from the lower surface of the gas-solid mixture barrier layer above, in order to prevent the solid particle float and the nitrogen barrier layer from overflowing from the annular space channel between the outer tube and the inner tube of the cavity.

[0014] On the other hand, embodiments of the present invention also disclose a method for controlling the dissolution of a gas-solid mixed solvent-resistant layer, which includes the following steps:

[0015] The tank is constructed using the positive circulation method. Clean water is injected into the inner tube of the cavity, and the brine produced is extracted from the annulus between the inner and outer tubes of the cavity.

[0016] Once the volume and top area of ​​the cavity reach a certain value, nitrogen is injected into the annulus between the production sleeve and the outer cavity tube, according to the design requirements of the cavity-making stage, to form a nitrogen anti-solution layer.

[0017] Once the top of the cavity reaches a certain radius, a certain amount of solid particle floats are injected into the annulus between the inner and outer cavity tubes to form a solid particle pad layer below the nitrogen gas barrier layer. The solid particle pad layer and the nitrogen gas barrier layer form a gas-solid mixed barrier layer.

[0018] The cavity is usually constructed using a reverse circulation method, where clean water is injected into the annulus of the inner and outer cavity tubes, and the resulting brine is extracted from the inner cavity tube to the ground.

[0019] After the cavity is created, nitrogen and solid particle floats are gradually recovered from the annulus of the production casing and the outer tube of the cavity.

[0020] Furthermore, during the cavity creation process, a corresponding amount of nitrogen is added based on the gas-water interface monitoring to maintain the nitrogen anti-solution layer at a certain thickness.

[0021] Furthermore, during the cavity creation process, when performing maintenance, lifting the cavity creation tubing, and measuring the cavity, the volume of nitrogen gas replenishment is adjusted, while the amount of solid particle cushioning remains unchanged.

[0022] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0023] 1. In the context of using the air cushion method for cavity construction in salt cavern gas storage, this method overcomes the problem of difficulty in controlling the gas-water interface caused by pressure fluctuations during the cavity construction process of salt cavern gas storage, enhances the stability and dissolution control effect of the gas barrier layer, strengthens the protection of the top plate, and reduces the difficulty of cavity construction using the air cushion method.

[0024] 2. Simplifying on-site processes, while providing clean brine, effectively reduces the number of nitrogen injections, which helps to significantly reduce the operating costs of the air cushion cavity-making process. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0027] Figure 2 This is a schematic diagram of the positive circulation method for cavity creation in this invention.

[0028] Figure 3 This is a schematic diagram of the reverse circulation method for cavity creation in this invention.

[0029] Figure label:

[0030] 1. Melting cavity;

[0031] 2. Inner tube of the cavity; 3. Outer tube of the cavity; 4. Production sleeve;

[0032] 5. Gas-solid mixed solution-blocking layer; 51. Nitrogen solution-blocking layer; 52. Solid particle pad layer;

[0033] 6. The annular space between the inner and outer tubes of the ostomy cavity;

[0034] 7. Annular space channel between the production sleeve and the cavity outer tube. Detailed Implementation

[0035] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0036] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0038] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0039] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] like Figure 1-3 As shown, the present invention provides a gas-solid mixed solution-blocking layer, which is applied in a solution cavity; the gas-solid mixed solution-blocking layer includes: a nitrogen solution-blocking layer and a solid particle pad layer, the solid particle pad layer is suspended and covers the bottom of the nitrogen solution-blocking layer, and the solid particle pad layer includes a plurality of solid particle floats.

[0041] A cavity-forming tube is also inserted into the cavity. The bottom end of the cavity-forming tube extends into the cavity through the gas-solid mixed anti-solution layer, and the bottom end of the cavity-forming tube is located below the gas-solid mixed anti-solution layer.

[0042] In the early stages of cavity construction, the positive circulation method is used to build the tank. Clean water is injected into the inner tube of the cavity, and the clean water dissolves the rock salt in the salt layer. The resulting brine is extracted from the annulus between the inner tube and the outer tube of the cavity.

[0043] To prevent excessively rapid dissolution and ensure sufficient bottom sand-holding space, once the volume and top area of ​​the dissolution cavity reach a certain value (500-2000 cubic meters), according to the design requirements of the cavity-building stage, nitrogen gas with a concentration of not less than 95% is first injected into the annular space channel between the production casing and the cavity-building outer pipe. The specific amount of nitrogen injected is adjusted according to the current cavity radius, cavity-building stage design, and gas-water interface control requirements. The thickness is usually in the range of 10-20 cm, forming an effective nitrogen dissolution barrier layer to inhibit the dissolution reaction of the brine below on the upper salt layer.

[0044] Once the top of the cavity reaches a certain radius, the cavity volume is 10,000-15,000 cubic meters, and the top radius is 10-15 meters. A solid particle pad, formed by slightly denser solid particle floats, is injected through the annular space between the inner and outer cavity tubes. These solid particle floats are lightweight solid particles such as glass microspheres or foam ceramic balls with a specific gravity of 0.2-0.8, a particle size of 2-25 mm, and a pressure resistance range of 10-30 MPa. The solid particle pad and the nitrogen-based anti-solution layer form a gas-solid mixed anti-solution layer, configured according to different particle size distributions and weight ratios based on the pressure at the cavity location. The solid particle floats are injected in a single injection, with a total volume of 150-200 cubic meters, to ensure that the minimum thickness of the solid particle pad at the maximum cavity radius is not less than 2 cm. The principle is to utilize the density differences among brine, solids, and gases to create flow lag under pressure fluctuations, thereby reducing or offsetting the impact of pressure fluctuations and achieving the purpose of enhancing the stability of the nitrogen barrier layer and the effect of solubility control.

[0045] Two different functional nitrogen gas barrier layers and a solid particle pad layer constitute a gas-solid mixed barrier layer, typically 12-20 cm thick, with a minimum thickness of 12 cm. This ensures the stability of the enhanced nitrogen gas barrier layer and the improved solubility control during cavity formation. Simultaneously, the gas-solid mixed barrier layer is positioned 5-10 m above the brine outlet (tube shoe) at the bottom of the outer cavity tube to prevent the solid particle float and gas from overflowing from the annular space between the outer and inner cavity tubes.

[0046] During the cavity-building process, the thickness of the solid particle pad automatically adjusts as the top area of ​​the cavity expands, enhancing the stability of the gas barrier layer. Therefore, the gas-water interface position can be stabilized within a small fluctuation range, eliminating the need for frequent gas injection.

[0047] During cavity creation, when performing maintenance, lifting the cavity creation tubing, and measuring the cavity, the volume of nitrogen gas is adjusted and replenished, while the amount of solid particle cushioning remains unchanged.

[0048] In the middle and later stages of cavity construction, a reverse circulation method is used to build the cavity. This involves injecting clean water into the annulus of the inner and outer cavity pipes to dissolve the halite in the salt layer, and then extracting the resulting brine from the inner cavity pipe to the surface. During cavity construction, the mixing and anti-solution layer is set up in the same way as in the forward circulation method. As the top cavity expands, nitrogen is injected in accordance with the interface rise monitored at the gas-water interface, while the amount of solid particle cushion layer remains unchanged.

[0049] In the final stage of cavity construction, nitrogen and solid particle floats are gradually recovered from the annulus of the production casing and the outer tube of the cavity construction. After reprocessing, they can be used for the next cavity construction of a salt cavern gas storage facility.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 controlling the dissolution of a gas-solid mixed anti-solution layer, characterized in that, Includes the following steps: A cavity-forming tubing is used, the bottom end of which penetrates the gas-solid mixed solution-blocking layer and extends into the cavity. The cavity-forming tubing includes an inner cavity-forming tube and an outer cavity-forming tube. The tank is constructed using the positive circulation method. Clean water is injected into the inner tube of the cavity, and the brine produced is extracted from the annulus between the inner and outer tubes of the cavity. Once the volume and top area of ​​the cavity reach a certain value, nitrogen is injected into the annulus between the production sleeve and the outer cavity tube, according to the design requirements of the cavity-making stage, to form a nitrogen anti-solution layer. Once the top of the cavity reaches a certain radius, a certain amount of solid particle floats are injected into the annulus between the inner and outer cavity tubes to form a solid particle pad layer below the nitrogen gas barrier layer. The solid particle pad layer and the nitrogen gas barrier layer form a gas-solid mixed barrier layer. The cavity is constructed using a reverse circulation method, with clean water injected into the annulus of the inner and outer cavity tubes, and the resulting brine is extracted from the inner cavity tube to the ground. After the cavity is created, nitrogen and solid particle floats are gradually recovered from the annulus of the production casing and the outer tube of the cavity.

2. The dissolution control method according to claim 1, characterized in that, During the cavity creation process, nitrogen is added in accordance with the monitoring of the gas-water interface to maintain the nitrogen barrier layer at a certain thickness.

3. The dissolution control method according to claim 2, characterized in that, During cavity creation, when performing maintenance, lifting the cavity creation tubing, and measuring the cavity, adjust the volume of nitrogen to be replenished, while keeping the amount of solid particle padding unchanged.

4. The method for controlling the dissolution of an upper layer according to claim 1, characterized in that, The nitrogen concentration in the nitrogen barrier layer is not less than 95%, which is used to inhibit the dissolution of the brine below.

5. The dissolution control method according to claim 4, characterized in that, The thickness of the nitrogen-resistant layer is 10~20cm.

6. The method for controlling the dissolution of an upper layer according to claim 1, characterized in that, The solid particle float has a specific gravity of 0.2~0.8, a particle size of 2~25mm, and a pressure resistance range of 10~30MPa.

7. The method for controlling the dissolution of an substance according to claim 1, characterized in that, The thickness of the solid particle pad layer is not less than 2 cm.

8. The method for controlling the dissolution of an upper layer according to claim 1, characterized in that, The thickness of the gas-solid hybrid solvent-resistant layer is 12~20cm.

9. The method for controlling the dissolution of an upper layer according to claim 1, characterized in that, The brine outlet at the bottom of the outer tube of the cavity is 5-10m away from the lower surface of the gas-solid mixture barrier layer above, so as to prevent the solid particle float and the nitrogen barrier layer from overflowing from the annular space between the outer tube and the inner tube of the cavity.

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