A salt cave brine circulation crack repair system and repair method

Abstract

The present application discloses a salt cavern brine circulation fissure repair system and repair method, comprising a brine injection pipe, a brine outlet channel, a surface brine circulation device and a surface brine pump system. The brine injection pipe and the brine outlet channel are located in the salt cavern wellbore, and the brine injection pipe is located on the center line of the salt cavern wellbore space. The brine outlet channel is an annular space surrounded by the salt cavern wellbore and the brine injection pipe. The brine injection pipe is connected to the surface brine pump system, the brine outlet channel is connected to the surface brine circulation device, and the surface brine circulation device is connected to the surface brine pump system. Brine is injected into the salt cavern through the brine injection pipe, and the brine flows back to the surface brine circulation device through the brine outlet channel, and then circulated into the salt cavern through the surface brine pump system. The present application uses a brine positive circulation system in the wellbore, combined with a salt crystallization effect driven by temperature difference, to achieve efficient repair of the damage and leakage problem at the second interface position of the salt cavern injection and production pipe, thereby eliminating the hidden danger of gas leakage.

Description

Technical Field

[0001] The present application relates to the field of salt cavern energy storage technology, and in particular to a salt cavern brine circulation fissure repair system and repair method. Background Art

[0002] Currently, underground salt caverns are widely used to store gaseous media such as natural gas, compressed air, and hydrogen. Due to the high sealing properties of the surrounding salt rock, salt caverns are ideal gas storage spaces. However, during actual energy storage in salt caverns, numerous cracks can develop at the interface between the injection and production tubing and the salt rock (i.e., the second interface) and in the surrounding salt rock due to factors such as inadequate consolidation and mechanical disturbances, potentially threatening the reservoir's sealing properties.

[0003] Most existing repair technologies rely on static self-healing mechanisms, which involve injecting saturated brine to soak the cracks and using the self-healing ability of salt rock in a saturated brine environment for repair. The specific operation is to soak the damaged salt cavern in saturated brine in order to repair the cracks through the self-healing effect of salt rock. This method mainly relies on capillary action, with brine penetrating into the cracks, providing the liquid brine environment required for recrystallization and diffusion mass transfer, the two self-healing mechanisms of salt rock, thereby achieving the effect of crack repair. This process does not require complex equipment and is mainly composed of a conventional injection and production system. Although the saturated brine immersion repair method can restore the sealing of salt caverns to a certain extent, its effect is limited and there are many defects:

[0004] 1. Long repair time: Existing technologies rely on the natural diffusion and self-healing process of salt, which is slow and often requires months to significantly improve the sealing of damaged areas or even the entire salt cavern. This is too time-consuming and inefficient for projects that require rapid restoration of reservoir sealing performance.

[0005] 2. Limited repair capacity: When cracks are large or complex, the natural infiltration and crystallization of saturated brine alone is difficult to effectively repair. In this case, the self-healing capacity is obviously insufficient, and brine cannot completely fill and repair the cracks, especially in areas with deep cracks or complex structures.

[0006] From the above analysis, it can be seen that the current technology has many shortcomings in terms of repair speed and repair capacity. This application provides a salt cavern brine circulation fissure repair system and repair method, aiming to solve the above-mentioned defects of the existing technology. Summary of the Invention

[0007] To address the above-mentioned issues, the present application provides a salt cavern brine circulation fissure repair system and repair method, which can quickly and specifically address the hidden danger of gas leakage caused by rock damage at the interface between the salt cavern injection and production wellbore and the salt rock (i.e., the second interface). The technical solution is as follows:

[0008] The first aspect of the present application provides a salt cavern brine circulation fissure repair system, comprising a brine injection pipe, a brine outlet channel, a surface brine circulation device and a surface brine pump system, wherein the brine injection pipe and the brine outlet channel are located in the salt cavern wellbore, and the brine injection pipe is located on the center line of the salt cavern wellbore space, the brine outlet channel is an annular space surrounded by the salt cavern wellbore and the brine injection pipe, the brine injection pipe is connected to the surface brine pump system, the brine outlet channel is connected to the surface brine circulation device, the surface brine circulation device is connected to the surface brine pump system, brine is injected into the salt cavern through the brine injection pipe, the brine flows back to the surface brine circulation device through the brine outlet channel, and then circulated into the salt cavern through the surface brine pump system.

[0009] For example, in the salt cavern brine circulation fracture repair system provided in one embodiment, the brine injection pipe extends deep into the cavity area at the bottom of the salt cavern.

[0010] For example, in the salt cavern brine circulation fissure repair system provided in one embodiment, a filtering and salt replenishing device is provided in the surface brine circulation device to ensure that the brine flowing back into the surface brine circulation device through the brine outlet channel is in a saturated state.

[0011] For example, in the salt cavern brine circulation fracture repair system provided in one embodiment, the surface brine pump system includes a flow control device to control the brine injection flow rate, thereby controlling the brine circulation rate in the salt cavern.

[0012] For example, in the salt cavern brine circulation fissure repair system provided in one embodiment, a heating device is further included. The heating device is arranged at the water inlet of the brine injection pipe, or the heating device is arranged on the periphery of the surface brine circulation device to heat the brine, thereby maintaining the brine temperature difference between the bottom and top of the cavity during the brine circulation process.

[0013] A second aspect of the present application provides a method for repairing brine circulation cracks in a salt cavern, which is repaired using the above-mentioned brine circulation crack repair system, comprising the following steps:

[0014] S1 closes the wellbore and fills the salt cavern with saturated brine;

[0015] S2 inserts the brine injection pipe into the wellbore and deep into the cavity area at the bottom of the salt cavern. Through the surface brine pump system, saturated brine is slowly and continuously injected into the wellbore, pushing the brine at the bottom to the top of the cavity, so that heat exchange occurs between the brine at the bottom and the top of the cavity;

[0016] S3 continuously circulates brine through the surface brine circulation device and the surface brine pump system. The high-temperature saturated brine at the bottom is cooled and converted into a supersaturated state at the top of the cavity near the connection between the wellbore and the salt cavern, which is also the necking position of the salt cavern. Driven by the interfacial potential energy, the supersaturated brine undergoes salt crystallization at the second interface position where the surrounding rock cracks and damage are detached, gradually filling the cracks at the interface and repairing the damage.

[0017] For example, in the salt cavern brine circulation fissure repair method provided in one embodiment, in S1, saturated brine is filled into the salt cavern, and the salt cavern is left to stand for a period of time to ensure that the liquid inside the salt cavern reaches a fully saturated state and a thermally stable state. After the state stabilizes, saturated brine is injected through the brine injection pipe.

[0018] For example, in the salt cavern brine circulation fissure repair method provided in one embodiment, in S2, the flow rate of the brine is controlled to ensure sufficient heat exchange between the brine and the formation, thereby maintaining the brine temperature difference between the top and bottom of the cavity between 1-3°C.

[0019] For example, in the salt cavern brine circulation fissure repair method provided in one embodiment, in S3, the brine in the salt cavern flows in a positive circulation so that the brine circulates to the connection between the wellbore and the salt cavern, which is also the necking position of the salt cavern, to form turbulence.

[0020] The beneficial effects of a salt cavern brine circulation fissure repair system and method provided in some embodiments of the present application are as follows: the present application can improve the repair speed, enhance the repair capacity, and introduce active repair power to effectively address the risk of leakage caused by severe damage to the second interface position and large fissures in the salt cavern injection and production wellbore. Compared with the existing technology, the present application has the following significant advantages:

[0021] 1. Improved repair efficiency: Traditional methods use static immersion to achieve self-healing of salt rock, which takes a long time and has limited effectiveness in repairing complex fracture networks with severe damage. This application significantly accelerates the healing of salt rock fractures through a continuous saturated brine positive circulation system, leveraging temperature differences, the temperature-dependent solubility of soluble salts, and flow field conditions. This is particularly effective for repairing large fractures.

[0022] 2. Simple and economical process: This application does not require complex wellbore modifications or the introduction of new equipment. The repair work can be completed solely by relying on the existing wellbore brine, tubing, and surface brine circulation system. The positive circulation of brine enables flow-driven fracture repair, avoiding high costs and achieving excellent economic efficiency.

[0023] 3. Efficient self-healing mechanism: This application utilizes the temperature difference between the top and bottom of the salt cavern to cause the brine to transition from a saturated state to a supersaturated state as it flows through the junction of the wellbore and the salt cavern, which also forms the constriction of the salt cavern. This crystallization process effectively promotes the self-healing mechanism of the salt rock in the damaged area, improving repair efficiency.

[0024] 4. Environmental friendliness: Since this application only uses the brine already in the salt cave, there is no need to discharge a large amount of brine, and no external chemical reagents or complex mechanical equipment are introduced, it has little impact on the environment and meets the requirements of green and sustainable development.

[0025] In general, this application not only improves the speed and effect of salt cavern repair, but also achieves rapid repair of damaged cracks at the second interface position of the salt cavern wellbore through a simple and economical technical path, while being highly environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a structural diagram of the salt cavern brine circulation fissure repair system of this application. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0029] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by persons of ordinary skill in the field to which this disclosure belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0030] The main problems existing in the repair technology of the interface between the existing salt cavern injection and production string and the salt rock (i.e., the second interface) are as follows:

[0031] 1. Slow repair. Existing technology uses saturated brine to naturally soak cracks and repair salt cavern interfaces. However, due to a lack of driving force, the repair process typically takes months, making it difficult to quickly restore the salt cavern's sealing properties. This technology lags behind actual industrial application needs and cannot promptly prevent potential gas leaks.

[0032] 2. Limited repair capabilities. When the second interface of the salt cavern injection and production wellbore is severely damaged, especially when the fractures are wide open, the repair effectiveness of existing methods is significantly reduced, and they are unable to effectively seal the fractures in a short period of time. This is especially true when faced with complex rock damage and wide-open fracture structures. This repair method exhibits significant limitations and is difficult to ensure the long-term sealing of the salt cavern.

[0033] The present application provides a salt cavern brine circulation fissure repair system and repair method to quickly and specifically resolve the hidden danger of gas leakage caused by rock damage at the interface between the salt cavern injection and production string and the salt rock (i.e., the second interface).

[0034] The first aspect of the present application provides a salt cavern brine circulation fissure repair system, such as Figure 1As shown, it includes a brine injection pipe 2, a brine outlet channel 1, a surface brine circulation device 3 and a surface brine pump system 9. The brine injection pipe 2 and the brine outlet channel 1 are located in the salt cavern wellbore 4, and the brine injection pipe 2 is located on the center line of the salt cavern wellbore 4 space. The brine outlet channel 1 is an annular space surrounded by the salt cavern wellbore 4 and the brine injection pipe. The brine injection pipe 2 is connected to the surface brine pump system 9, the brine outlet channel 1 is connected to the surface brine circulation device 3, and the surface brine circulation device 3 is connected to the surface brine pump system 9. Brine is injected into the salt cavern 7 through the brine injection pipe 2, and the brine flows back to the surface brine circulation device 3 through the brine outlet channel 1, and then circulated into the salt cavern 7 through the surface brine pump system 9.

[0035] Among them, the surface brine circulation device 3 and the surface brine pump system 9 are installed on the ground, the salt cavern 7 is located in the underground salt rock formation 5, the wellbore 4 is connected to the cavity, and its internal space is the key channel for the positive circulation of brine. The connection between the bottom of the wellbore 4 and the salt cavern 7 is the casing shoe 6. The area near the wellbore 4 and the casing shoe 6 is the geometric distortion area of ​​the salt cavern, and it is also a weak sealing area, which is prone to cracks.

[0036] For example, in the salt cave brine circulation fissure repair system provided in one embodiment, Figure 1 As shown, the bottom end 8 of the brine injection pipe 2 extends into the cavity area at the bottom of the salt cavern 7.

[0037] According to the above embodiment, the brine injection pipe 2 is inserted into the wellbore 4, and the bottom end 8 is as deep as possible into the bottom of the salt cavern. Its main function is to provide a channel for injecting saturated brine during the positive circulation of brine.

[0038] For example, in the salt cavern brine circulation fissure repair system provided in one embodiment, a filtering and salt replenishing device is provided in the surface brine circulation device 3 to ensure that the brine flowing back into the surface brine circulation device 3 through the brine outlet channel 1 is in a saturated state.

[0039] According to the above embodiment, the surface brine circulation device 3 is used to recollect the brine returned from the wellbore 4 and recycle it through filtration, salt replenishment and re-injection processes to ensure that the brine is always saturated during the circulation process.

[0040] For example, in the salt cavern brine circulation fracture repair system provided in one embodiment, the surface brine pump system 9 includes a flow control device to control the brine injection flow rate, thereby controlling the brine circulation rate in the salt cavern.

[0041] According to the above embodiment, the surface brine pump system 9 is installed on the surface and is responsible for re-injecting the collected brine into the salt cavity and performing positive circulation through the brine injection pipe 2. The surface brine pump system 9 needs to maintain a constant and slow flow rate to ensure the stability of the repair process.

[0042] Under special conditions, such as larger cavities or more complex formation environments, the flow rate and temperature difference of the brine positive circulation may not achieve ideal results. For example, in the salt cavern brine circulation fissure repair system provided in one embodiment, a heating device is also included. The heating device is arranged at the water inlet of the brine injection pipe, or the heating device is arranged on the periphery of the surface brine circulation device to heat the brine and increase the temperature difference of the brine at the bottom and top of the cavity during the brine circulation process, thereby accelerating the formation of an oversaturated state and further promoting repair.

[0043] Focusing on the self-healing repair of the second interface position of the salt cavern injection and production wellbore / tubing string, the second aspect of the present application provides a salt cavern brine circulation crack repair method, which accelerates crack healing through a brine positive circulation system. The core technology is to use temperature difference and flow field effect to drive the salt in the brine to recrystallize at the damaged interface, thereby achieving rapid repair of the damaged crack position. When the salt cavern brine circulation crack repair system of the present application is used for repair, the specific repair method is as follows:

[0044] S1: Close the wellbore and fill the salt cavern with saturated brine. Leave it for a while to ensure that the liquid inside the salt cavern reaches full saturation and thermal stability.

[0045] After the state stabilizes, the brine injection pipe is inserted into the wellbore and penetrated into the cavity area at the bottom of the salt cavern. Saturated brine is slowly and continuously injected into the wellbore through the surface brine pump system, pushing the higher temperature brine at the bottom to the top of the cavity. When the brine flows through the damaged area, it exchanges heat with the lower temperature formation, reducing the temperature.

[0046] S3 continuously circulates brine through the surface brine circulation device and the surface brine pump system. The high-temperature saturated brine at the bottom is cooled and converted into a supersaturated state at the top of the cavity near the connection between the wellbore and the salt cavern, which is also the necking position of the salt cavern. Driven by the interfacial potential energy, the supersaturated brine undergoes salt crystallization at the second interface position where the surrounding rock cracks and damage are detached, gradually filling the cracks at the interface and repairing the damage.

[0047] The salt cave brine circulation fissure repair method of the present application has a geothermal gradient difference of 1-3°C between the bottom and top of the salt cave, and the solubility of the solute with sodium chloride as the main component in the salt cave brine increases monotonically with temperature. Therefore, the saturated brine with a higher temperature at the bottom will be cooled and converted to a supersaturated state at the connection between the wellbore at the top of the cavity and the salt cave, which is also the necking position of the salt cave. Driven by the interfacial potential energy, the supersaturated brine undergoes salt crystallization at the second interface position where the rock cracks and damage are detached, repairing the damage. The crystallization process is driven by the following two mechanisms:

[0048] 1. Turbulence effect: Due to the necking at the wellbore 4, the brine will form turbulence when circulating here, which increases the free energy of salt ions and promotes the formation of salt crystals.

[0049] 2. Reduced interfacial energy: The rough geometric characteristics of cracks and interfacial damage provide an ideal crystallization bed for salt ions, where the energy barrier required for crystallization is reduced, promoting rapid crystallization.

[0050] Through the surface brine circulation device 3 and the surface brine pump system 9, the brine continues to circulate positively, and the repair process gradually advances. As the brine continues to crystallize during the circulation process, the cracks at the interface are gradually filled, and the crack opening gradually decreases, thereby restoring the sealing performance at the second interface of the injection and production wellbore.

[0051] To ensure the mechanical stability of the crystallized healing structure, for example, in the salt cavern brine circulation fissure repair method provided in one embodiment, in S3, the brine in the salt cavern flows in a positive circulation so that the brine circulates to the connection between the wellbore and the salt cavern, which is also the necking position of the salt cavern, to form turbulence.

[0052] Among them, the circulation rate should be controlled at a low level to avoid the damage of the recrystallized structure to the excessive turbulent field. The circulation flow control needs to control the flow rate of the brine according to the specific damage situation in the wellbore. First, it is necessary to fully carry out the crystallization reaction during the repair process and maintain the mechanical stability of the recrystallized structure. Second, it is necessary to ensure that the brine in the cavity has sufficient heat exchange with the formation at the depth, and ensure that the temperature difference of the brine at the bottom and top of the cavity is maintained within the ideal range of 1-3°C to ensure the repair efficiency.

[0053] The brine is primarily composed of sodium chloride, with small amounts of other soluble salts such as sodium sulfate and sodium carbonate. All crystallized materials are naturally derived from salt solutions, eliminating the need for the addition of any external chemical reagents. Furthermore, the positive circulation system can be adapted to the specific conditions of the salt caverns using more suitable pumps or piping materials, thus preventing corrosion.

[0054] The salt cavern brine circulation fracture repair method proposed in this application utilizes a self-healing mechanism driven by a positively circulating brine system. By designing a positively circulating saturated brine flow system and utilizing temperature gradient differences and the solubility characteristics of the salt solution, the spontaneous crystallization of salt at the damaged interface is promoted. This method significantly improves the healing speed at the junction between the wellbore and the salt cavern, as well as at the surrounding rock and the second interface at the salt cavern necking location. In particular, recrystallization enhances the sealing performance at this location, solving the problem of the traditional static immersion method with long repair times and limited repair effects.

[0055] The supersaturated state is triggered by formation temperature differences, promoting crystallization. The supersaturated brine solution formed by the temperature difference within the salt cavity causes the brine to crystallize due to cooling when it circulates to the cavity top near the interface. This temperature-driven supersaturation effect effectively promotes the crystallization of salt ions, particularly at the geometric necking of the salt cavity and at interface damage, forming a stable recrystallized structure, improving the efficiency of repairing severe damage.

[0056] Crystallization is enhanced by utilizing turbulent flow and damage morphology at geometrically distorted locations. In the target repair area—the junction between the wellbore and the salt cavern, which also serves as the cavern's neck—the localized turbulence caused by geometric distortion increases the kinetic energy of the salt ions, further promoting salt crystallization. Furthermore, the reduced free energy at the interface damage creates an ideal bed for crystallization, promoting the localized healing process.

[0057] In summary, this application realizes the efficient repair of damage and leakage problems at the second interface of the salt cavern injection and production wellbore / tubing string through a brine positive circulation system in the wellbore, combined with the salt crystallization effect driven by temperature difference. It has the advantages of simple technology, economic feasibility, and rapid repair.

[0058] Although the implementation scheme of the present application has been disclosed as above, it is not limited to the applications listed in the description and implementation mode. It can be fully applied to various fields suitable for the present application. For those familiar with this field, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present application is not limited to the specific details and illustrations shown and described herein.

Claims

1. A salt cavern brine circulation fissure repair method, which uses a salt cavern brine circulation fissure repair system for repair, characterized in that: The salt cavern brine circulation fissure repair system includes a brine injection pipe, a brine outlet channel, a surface brine circulation device and a surface brine pump system. The brine injection pipe and the brine outlet channel are located in the salt cavern wellbore, and the brine injection pipe is located on the center line of the salt cavern wellbore space. The brine outlet channel is an annular space surrounded by the salt cavern wellbore and the brine injection pipe. The brine injection pipe is connected to the surface brine pump system, the brine outlet channel is connected to the surface brine circulation device, and the surface brine circulation device is connected to the surface brine pump system. Brine is injected into the salt cavern through the brine injection pipe, and the brine flows back to the surface brine circulation device through the brine outlet channel, and then circulated into the salt cavern through the surface brine pump system. The salt cave brine circulation fissure repair method comprises the following steps: S1 closes the wellbore and fills the salt cavern with saturated brine; S2 inserts the brine injection pipe into the wellbore and deep into the cavity area at the bottom of the salt cavern. Through the surface brine pump system, saturated brine is slowly and continuously injected into the wellbore, pushing the brine at the bottom to the top of the cavity, so that heat exchange occurs between the brine at the bottom and the top of the cavity; S3 continuously circulates brine through the surface brine circulation device and the surface brine pump system. The high-temperature saturated brine at the bottom is cooled at the top of the cavity near the connection between the wellbore and the salt cavern, and is also converted into an oversaturated state at the necking position of the salt cavern. Driven by the interfacial potential energy, the oversaturated brine crystallizes at the second interface position where the surrounding rock cracks and damage are detached, so as to gradually fill the cracks at the interface and repair the damage, wherein the second interface is the interface between the salt cavern wellbore and the salt rock.

2. The method for repairing brine circulation cracks in salt caverns according to claim 1, characterized in that: The brine injection pipe extends deep into the cavity area at the bottom of the salt cavern.

3. The method for repairing brine circulation cracks in salt caverns according to claim 1, characterized in that: A filtering and salt replenishing device is provided in the surface brine circulation device to ensure that the brine flowing back into the surface brine circulation device through the brine outlet channel is in a saturated state.

4. The method for repairing brine circulation cracks in salt caverns according to claim 1, characterized in that: The surface brine pump system includes a flow control device to control the brine injection flow rate, thereby controlling the brine circulation rate in the salt cavern.

5. The method for repairing brine circulation cracks in salt caverns according to claim 1, characterized in that: The salt cave brine circulation fissure repair system also includes a heating device, which is arranged at the water inlet of the brine injection pipe, or the heating device is arranged on the periphery of the surface brine circulation device to heat the brine, thereby maintaining the brine temperature difference between the bottom and top of the cavity during the brine circulation process.

6. The method for repairing brine circulation cracks in salt caverns according to claim 1, characterized in that: In S1, the salt cavern is filled with saturated brine, and the salt cavern is left to stand for a period of time to ensure that the liquid inside the salt cavern reaches a fully saturated state and a thermally stable state. After the state is stable, saturated brine is injected through the brine injection pipe.

7. The method for repairing brine circulation cracks in salt caverns according to claim 1, characterized in that: In the above-mentioned S2, the flow rate of the brine is controlled to ensure sufficient heat exchange between the brine and the formation, thereby maintaining the temperature difference of the brine between the top and bottom of the cavity between 1-3°C.

8. The method for repairing brine circulation cracks in salt caverns according to claim 1, characterized in that: In S3, the brine in the salt cavern flows in a positive circulation, so that the brine circulates to the connection between the wellbore and the salt cavern, and also forms turbulent flow at the necking position of the salt cavern.

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