A method for efficient construction of a salt cavern energy storage based on in-situ modification

Abstract

The present application belongs to the field of underground energy storage engineering, and discloses a high-efficiency construction method of salt cavern energy storage based on in-situ modification, comprising the following steps: determining the cavity construction position, establishing the initial communication path between the wellbore and the surrounding salt layer; performing in-situ modification treatment on the surrounding of the wellbore to form micro-cracks around the wellbore; injecting fracturing fluid into the modified target salt layer, controlling the water injection pressure and flow rate, so that the hydraulic fracture initiates and expands along the preset direction to form one or more permeability and solubility enhancement fracture network zones; in the early stage of cavity construction, a positive circulation mode is adopted, water is injected into the target rock formation through the central water injection pipe, and brine is discharged outward through the annular brine discharge pipe; in the middle stage of cavity construction, the reverse circulation mode is switched; in the late stage of cavity construction, the water injection and discharge capacity is reduced, and the positive and reverse circulation modes are repeatedly switched to finely process the local protrusions and recesses until the pump is stopped after the designed cavity volume and shape are achieved. The present application can greatly improve the cavity construction rate and stability.

Description

Technical Field

[0001] This invention belongs to the field of underground energy storage engineering, specifically relating to a method for constructing a salt cavern storage facility, and more specifically, to an efficient method for constructing a salt cavern energy storage facility based on in-situ modification. Background Technology

[0002] Utilizing the cavities of underground salt rock deposits to store energy media such as natural gas and hydrogen is a key means of strategic energy reserves. Currently, the mainstream single-well convection vertical reservoir construction technology worldwide relies on the gradual dissolution of the salt rock surface, resulting in a small exposed salt rock area and a low dissolution rate. The construction cycle of a commercially viable conventional salt cavern is typically measured in years, leading to high time and operating costs. While extensive research has been conducted in this field to optimize tubing combinations, circulation patterns, and water injection parameters, these methods are essentially passive optimizations of the surface dissolution process, failing to overcome the core bottleneck of dissolution area and thus offering limited efficiency improvements. To date, ideal application results have not been achieved. Therefore, there is an urgent need to develop a transformative construction technology that fundamentally overcomes the limitations of salt rock dissolution area, significantly shortening the construction cycle and reducing construction costs. Summary of the Invention

[0003] This invention aims to solve the technical problems of long construction cycle and high construction cost in the existing single-well convection cavity construction process due to the small dissolution area and low dissolution rate of salt rock. It provides an efficient construction method for salt cavern energy storage based on in-situ modification, so as to significantly shorten the cavity construction cycle and reduce the construction cost.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an efficient construction method for salt cavern energy storage based on in-situ modification, comprising the following steps: Step 1: Determine the cavity location and complete the production casing well operation; Step 2: Perforate in the target salt layer section to establish the initial connection path between the wellbore and the surrounding salt layer; Step 3: Perform in-situ modification treatment around the wellbore through the tubing string to form microcracks around the wellbore; the in-situ modification treatment is to inject high / low temperature modification fluid or apply a physical energy field; Step 4: After in-situ modification is completed, fracturing fluid is injected into the modified target salt layer through the fracturing working string. The injection pressure and flow rate are controlled to cause hydraulic fractures to initiate and expand along a preset direction, forming one or more permeability-enhancing and solubility-enhancing fracture network zones. The fracture extension length is monitored in real time using a microseismic monitoring instrument. Pumping is stopped when the total extension length of the fracture network zone around the wellbore reaches a preset value. The preset value is determined based on the designed cavity radius. Step 5: After fracturing is completed, a concentric double-pipe cavity-building tubing assembly consisting of a central water injection pipe and an annular brine drain pipe is lowered into the wellbore. Step 6: In the early stage of cavity construction, a positive circulation mode is adopted, injecting water into the target rock layer through the central water injection pipe and discharging brine outward through the annular brine discharge pipe; in the middle stage of cavity construction, switch to a reverse circulation mode, discharging brine outward through the central water injection pipe and injecting water into the target rock layer through the annular brine discharge pipe; in the later stage of cavity construction, reduce the water injection and discharge rate, and perform fine treatment on local protrusions and depressions by repeatedly switching between positive and reverse circulation until the designed cavity volume and shape are achieved, and then stop pumping.

[0005] In step 3, the applied physical energy field is at least one of electric pulse, microwave, and laser, and the injected high-temperature modified fluid is one of high-temperature steam, high-temperature gas, or high-temperature water.

[0006] In step 3, the in-situ modification treatment is to inject high-temperature steam. The temperature of the injected high-temperature steam is 300-600℃. The high-temperature steam is injected into the target salt layer through a heat-insulated oil pipe. During the injection process, the wellhead temperature and pressure, bottom hole temperature and annulus pressure are monitored in real time to ensure that the wellbore string operates within safe conditions and to prevent the formation from being forced open. After stopping steam injection, shut in the well for 12-36 hours to allow the modification effect to fully penetrate or stabilize.

[0007] In step 4, slickwater with added drag reducer and clay stabilizer is selected as the fracturing fluid. When injecting the fracturing fluid, a step-by-step injection procedure is adopted, and the water injection rate is gradually increased from 1~3 m³ / min to 5~8 m³ / min. In step 4, while injecting the fracturing fluid, the pressure is monitored simultaneously. Once formation fracturing is indicated, the fracturing fluid is continuously pumped at the maximum displacement. The preset value is 40% to 60% of the designed cavity radius.

[0008] In step 6, during the initial and middle stages of cavity construction, the water injection rate is 150 m³ / h to 300 m³ / h; at the same time, the concentration and temperature of the discharged brine are monitored to assess the progress of volumetric erosion.

[0009] In step 6, when sonar monitoring shows that the cavity volume has reached 50% of the design, the cavity construction phase begins and the reverse circulation mode is switched. When the top shape of the cavity approaches the design boundary, the cavity construction phase begins.

[0010] The efficient construction method for salt cavern energy storage based on in-situ modification further includes the following steps: Step 7: After stopping the pump, assess the stability and sealing of the cavity. Once the requirements are met, the construction of the salt cavern gas storage facility is complete.

[0011] During the cavity construction process in step 6, the concentration, temperature, and internal pressure of the discharged brine are continuously monitored, and sonar cavity measurement and other methods are used to assess the cavity development status in real time and guide the adjustment of circulation parameters.

[0012] In step 1, the cavity is constructed in an abandoned horizontal solution cavity or a salt rock layer; When the cavity is located in an abandoned horizontal karst cavity, based on historical production data, downhole sonar detection, and mechanical analysis, the cavity is selected where the top plate is stable, the wellbore can withstand pressure after repair, and there is a thick layer of high-grade salt around it for further dissolution and expansion of the old salt rock cavity. The operation of completing the production casing well includes: well workover, inserting a new casing of slightly smaller size into the original casing and cementing it, and rebuilding the mechanical integrity and sealing of the wellbore. When the cavity construction location is a salt rock layer, the target salt layer should be selected based on its burial depth, thickness, and grade to meet the engineering implementation requirements of subsequent in-situ modification, controlled fracturing, and convection cavity construction, and the target salt layer should be free of penetrating fault defects for cavity construction. The operation of the production casing well includes: drilling, cementing, and completion of the production casing well, followed by well workover to ensure that the inner wall of the casing is smooth, free of burrs and deformation, to meet the requirements for smooth running and sealing of subsequent fracturing tubing and cavity construction tubing.

[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention, through in-situ modification and controlled fracturing as pre-treatment, increases the effective dissolution area of ​​salt rock by orders of magnitude, transforming the dissolution mode from planar corrosion to networked volumetric corrosion, thereby significantly improving the cavity construction rate. The shortened cavity construction cycle directly leads to a substantial reduction in the overall operating costs, including equipment occupancy, personnel, energy consumption, and water treatment.

[0014] 2. By switching between positive and negative circulation brine discharge methods, this invention can actively control the expansion direction of the fracturing fractures. The initial development morphology of the cavity can be preset at the beginning of cavity construction, and fine adjustments can be made in subsequent cavity construction through optimized circulation parameters. This achieves active intervention in the cavity morphology, which is conducive to forming a more regular and mechanically stable reservoir cavity.

[0015] 3. The process of this invention is not only applicable to newly built salt cavern storage facilities, but also, as an extended application, to the renovation and secondary construction of old or abandoned salt caverns that were halted due to technical and economic reasons or whose cavities did not meet design requirements, thus fully tapping the economic value of existing well shafts and underground space resources. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating an efficient construction method for salt cavern energy storage based on in-situ modification, provided in an embodiment of the present invention. In this diagram, 1 represents the thermal damage zone, 2 represents the fracture network zone, 3 represents the cavity, and 4 represents the production casing well. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but 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.

[0018] Example 1 like Figure 1 As shown, Embodiment 1 of the present invention provides an efficient construction method for salt cavern energy storage based on in-situ modification, used to construct a natural gas storage facility, specifically including the following steps: Step 1: Determine the cavity location and complete the production casing well operation.

[0019] In step 1, the cavity is constructed in a salt rock layer. The target salt layer is selected based on its burial depth, thickness, and grade to meet the engineering requirements for subsequent in-situ modification, controlled fracturing, and convection cavity construction. The target salt layer is selected for cavity construction without penetrating fault defects.

[0020] Specifically, in this embodiment, the selected target salt layer has a burial depth range of 600m-2400m, a thickness greater than 60m, a salt rock grade greater than 65%, and no penetrating fault defects.

[0021] Specifically, in step 1, completing the production casing well operation includes: after drilling, cementing, and completion of the production casing well, performing well workover to ensure the inner wall of the casing is smooth, free of burrs and deformation, meeting the requirements for smooth running and sealing of subsequent fracturing and cavity-building tubing strings. The structure after completing the production casing well operation is as follows: Figure 1 As shown in (a).

[0022] Step 2: Perforate in the target salt layer section to establish the initial connection path between the wellbore and the surrounding salt layer.

[0023] Step 3: Perform in-situ modification treatment around the wellbore through the tubing string to form microcracks around the thermal damage zone 1 of the wellbore; the in-situ modification treatment is to inject high / low temperature modification fluid or apply a physical energy field.

[0024] In step 3, the applied physical energy field is at least one of electric pulse, microwave, and laser, and the injected high-temperature modified fluid is one of high-temperature steam, high-temperature gas, or high-temperature water.

[0025] Specifically, in step 3 of this embodiment, the in-situ modification treatment involves injecting high-temperature steam at a temperature of 300-600°C. This high-temperature steam is injected into the target salt layer through an insulated tubing. During injection, the wellhead temperature and pressure, bottom hole temperature, and annular pressure are monitored in real time to ensure the wellbore string operates within safe conditions and to prevent formation breakage. After steam injection is stopped, the well is shut in for 12-36 hours to allow for slow cooling using natural formation heat dissipation. This allows thermal stress to fully exert its effect, promoting the propagation and stabilization of microcracks, and ensuring the modification effect is fully penetrated or stabilized. The structure after in-situ modification and the formation of microcracks is as follows: Figure 1 As shown in (b).

[0026] Step 4: After in-situ modification, fracturing fluid is injected into the modified target salt layer through the fracturing working string. The injection pressure and flow rate are controlled to cause the hydraulic fractures to initiate and propagate along a preset direction, forming one or more permeability-enhancing and solubility-enhancing fracture network zones 2, such as... Figure 1 As shown in (c); the length of the crack extension is detected in real time using a microseismic monitoring instrument, and pumping is stopped when the total extension length of the crack network zone around the well reaches a preset value; the preset value is determined based on the designed cavity radius.

[0027] Specifically, in this embodiment, the optimal fracture propagation direction can be determined based on the differences in mechanical properties of the modified salt layer and the distribution of geostress, and the fracturing pumping program and key control parameters can be designed.

[0028] Specifically, in step 4, slickwater with added drag reducer and clay stabilizer is selected as the fracturing fluid. When injecting the fracturing fluid, a step-by-step injection procedure is adopted, gradually increasing the water injection rate from 1~3 m³ / min to 5~8 m³ / min. Furthermore, in step 4, while injecting the fracturing fluid, the pressure is monitored simultaneously. Once formation fracturing is indicated, the fracturing fluid is continuously pumped at the maximum displacement. Specifically, the preset value is preferably 40% to 60% of the designed cavity radius.

[0029] In this embodiment, the pump is stopped when the total expansion length of the crack mesh zone around the well reaches half of the designed cavity radius, which is displayed in real time by a microseismic monitoring instrument.

[0030] Step 5: After fracturing is completed, a concentric double-pipe cavity-building tubing assembly consisting of a central water injection pipe and an annular brine drain pipe is lowered into the wellbore.

[0031] After fracturing is completed, the fracturing working tubing is removed and replaced with a concentric double-tube cavity-building tubing assembly. A central water injection pipe is installed in the center, and an annular brine discharge pipe is installed around the central water injection pipe to form a circulation structure.

[0032] Step 6: In the initial stage of cavity construction, a forward circulation mode is adopted. Water is injected into the target rock layer through the central water injection pipe, and brine is discharged outward through the annular brine discharge pipe. The concentration and temperature of the discharged brine are monitored simultaneously to assess the progress of volumetric dissolution. In the middle stage of cavity construction, the reverse circulation mode is switched. Brine is discharged outward through the central water injection pipe, and water is injected into the target rock layer through the annular brine discharge pipe to control the upward development speed and shape of the cavity. In the later stage of cavity construction, the water injection and discharge rate is reduced. By repeatedly switching between forward and reverse circulation, local protrusions and depressions are finely treated until the designed cavity volume and shape are achieved, and then the pump is stopped. The final cavity 3 is shown in Figure 3. Figure 1 As shown in (d).

[0033] Specifically, in step 6, during the initial and middle stages of cavity construction, fresh water is injected from the central water injection pipe at a much higher rate than the conventional discharge rate during the initial stage of traditional convection cavity construction. The fresh water flows at high speed along the formed fracture network to dissolve the salt rock, and the brine is discharged from the annulus, achieving volumetric dissolution and rapidly forming the main cavity channel. Specifically, during the initial and middle stages of cavity construction, the water injection rate is 150 m³ / h to 300 m³ / h. The criterion for determining whether the target salt layer has achieved volumetric dissolution is that the concentration of the discharged brine rapidly increases and remains above 70% of the saturation concentration.

[0034] Furthermore, in step 6, when sonar monitoring shows that the cavity volume has reached 50% of the design, the process enters the mid-stage of cavity construction. The system switches to reverse circulation mode, draining brine outwards through the central water injection pipe and injecting water into the target rock strata through the annular brine discharge pipe. This controls the upward development speed and shape of the cavity and promotes the sedimentation of insoluble matter at the bottom, forming a healthy cavity bottom shape. When the top shape of the cavity approaches the design boundary, the process enters the late stage of cavity construction. At this time, the water injection rate needs to be reduced, and the forward and reverse circulation modes are alternately switched to finely adjust the cavity shape, such as finely carving out protruding or recessed areas, until the designed cavity volume and shape are achieved.

[0035] Specifically, during the entire cavity construction process in step 6, the concentration, temperature, and internal pressure of the discharged brine are continuously monitored, and sonar cavity measurement and other means are used to assess the cavity development status in real time and guide the adjustment of circulation parameters, including circulation mode, water injection flow rate, and gate spacing.

[0036] Furthermore, the efficient construction method for salt cavern energy storage based on in-situ modification also includes the following steps: Step 7: After stopping the pump, assess the stability and sealing of the cavity. Once the requirements are met, the construction of the salt cavern gas storage facility is complete.

[0037] Example 2 like Figure 1 As shown, Embodiment 2 of the present invention provides an efficient construction method for salt cavern energy storage based on in-situ modification, used to construct a natural gas storage facility, specifically including the following steps: Step 1: Determine the cavity location and complete the production casing well operation.

[0038] Unlike Example 1, in step 1 of this example, the cavity construction location is an abandoned horizontal solution cavity. When determining the cavity construction location, the abandoned horizontal solution cavity is evaluated and considered from aspects such as geological stability, wellbore integrity, and usability. Through historical production data, downhole sonar detection, and mechanical analysis, an old salt rock cavity with a stable cavity top plate, a wellbore that can withstand pressure after repair, and a thick high-grade salt layer around it that can be further dissolved and expanded is selected as the foundation for reservoir construction. The operation of the production casing well includes the following steps: wellbore repair, inserting a new casing of slightly smaller size into the original casing and cementing it, and rebuilding the mechanical integrity and sealing of the wellbore.

[0039] Step 2: Perforate in the target salt layer section to establish the initial connection path between the wellbore and the surrounding salt layer.

[0040] In this embodiment, deep-penetrating perforation technology is used to reconstruct the perforation in the target salt layer section and re-establish the connection path between the wellbore and the surrounding salt layer.

[0041] Step 3: Perform in-situ modification treatment around the wellbore through the tubing string to form microcracks around the wellbore; the in-situ modification treatment is to inject high / low temperature modification fluid or apply a physical energy field.

[0042] In step 3, the applied physical energy field is at least one of electric pulse, microwave, and laser, and the injected high-temperature modified fluid is one of high-temperature steam, high-temperature gas, or high-temperature water.

[0043] In step 3, the in-situ modification treatment involves injecting high-temperature steam at a temperature of 300-600°C. The high-temperature steam is injected into the target salt layer through an insulated tubing. During the injection process, the wellhead temperature and pressure, bottom hole temperature, and annular pressure are monitored in real time to ensure that the wellbore string operates within safe conditions and to prevent the formation from being forced open. After the steam injection is stopped, the well is shut in for 12-36 hours to allow the modification effect to fully penetrate or stabilize.

[0044] Step 4: After in-situ modification is completed, fracturing fluid is injected into the modified target salt layer through the fracturing working string. The injection pressure and flow rate are controlled to cause the hydraulic fractures to initiate and expand along the preset direction, forming one or more permeability-enhancing and solubility-enhancing fracture network zones. The fracture extension length is monitored in real time using a microseismic monitoring instrument. Pumping is stopped when the total extension length of the fracture network zone around the wellbore reaches the preset value. The preset value is determined based on the designed cavity radius.

[0045] In step 4, slickwater with added drag reducer and clay stabilizer is selected as the fracturing fluid. When injecting the fracturing fluid, a step-by-step injection procedure is adopted, and the water injection rate is gradually increased from 1~3 m³ / min to 5~8 m³ / min. In step 4, while injecting the fracturing fluid, the pressure is monitored simultaneously. Once formation fracturing is indicated, the fracturing fluid is continuously pumped at the maximum displacement. The preset value is 40% to 60% of the designed cavity radius.

[0046] Step 5: After fracturing is completed, a concentric double-pipe cavity-building tubing assembly consisting of a central water injection pipe and an annular brine drain pipe is lowered into the wellbore.

[0047] Step 6: In the initial stage of cavity construction, a forward circulation mode is adopted, injecting water into the target rock layer through the central water injection pipe and discharging brine outward through the annular brine discharge pipe. The concentration and temperature of the discharged brine are monitored simultaneously to assess the progress of volumetric dissolution. In the middle stage of cavity construction, switch to a reverse circulation mode, discharging brine outward through the central water injection pipe and injecting water into the target rock layer through the annular brine discharge pipe. In the later stage of cavity construction, reduce the water injection and discharge rate, and repeatedly switch between forward and reverse circulation to finely treat local protrusions and depressions until the designed cavity volume and shape are achieved, and then stop pumping.

[0048] Specifically, in step 6, during the initial and middle stages of cavity construction, the water injection rate is 150 m³ / h to 300 m³ / h; during the cavity construction period, the concentration and temperature of the discharged brine are monitored simultaneously to assess the progress of volumetric dissolution; if the concentration of the discharged brine rises rapidly and remains above 70% of the saturation concentration, it proves that the target rock layer has achieved volumetric dissolution.

[0049] Specifically, in step 6, when sonar monitoring shows that the cavity volume has reached 50% of the design, the cavity construction enters the mid-stage and switches to the reverse circulation mode; when the top shape of the cavity approaches the design boundary, the cavity construction enters the late stage.

[0050] Furthermore, during the cavity construction process in step 6, the concentration, temperature, and internal pressure of the discharged brine are continuously monitored, and sonar cavity measurement and other methods are used to assess the cavity development status in real time and guide the adjustment of circulation parameters.

[0051] Furthermore, the efficient construction method for salt cavern energy storage based on in-situ modification also includes the following steps: Step 7: After stopping the pump, assess the stability and sealing of the cavity. Once the requirements are met, the construction of the salt cavern gas storage facility is complete.

[0052] In this embodiment, during the fracturing and dissolution process, monitoring methods such as microseismic monitoring are required to strictly control the scale of fracturing and the direction of dissolution, so as to avoid damaging the stability and sealing of the old cavity top plate and ensure that a storage cavity that meets the design requirements can be safely and efficiently expanded on the basis of the original old cavity.

[0053] 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 efficiently constructing salt cavern energy storage facilities based on in-situ modification, characterized in that, Includes the following steps: Step 1: Determine the cavity location and complete the production casing well operation; Step 2: Perforate in the target salt layer section to establish the initial connection path between the wellbore and the surrounding salt layer; Step 3: Perform in-situ modification treatment around the wellbore through the tubing string to form microcracks around the wellbore; the in-situ modification treatment is to inject high / low temperature modification fluid or apply a physical energy field; Step 4: After in-situ modification is completed, fracturing fluid is injected into the modified target salt layer through the fracturing working string. The injection pressure and flow rate are controlled to cause hydraulic fractures to initiate and expand along a preset direction, forming one or more permeability-enhancing and solubility-enhancing fracture network zones. The fracture extension length is monitored in real time using a microseismic monitoring instrument. Pumping is stopped when the total extension length of the fracture network zone around the wellbore reaches a preset value. The preset value is determined based on the designed cavity radius. Step 5: After fracturing is completed, a concentric double-pipe cavity-building tubing assembly consisting of a central water injection pipe and an annular brine drain pipe is lowered into the wellbore. Step 6: In the early stage of cavity construction, a positive circulation mode is adopted, injecting water into the target rock layer through the central water injection pipe and discharging brine outward through the annular brine discharge pipe; in the middle stage of cavity construction, switch to a reverse circulation mode, discharging brine outward through the central water injection pipe and injecting water into the target rock layer through the annular brine discharge pipe; in the later stage of cavity construction, reduce the water injection and discharge rate, and perform fine treatment on local protrusions and depressions by repeatedly switching between positive and reverse circulation until the designed cavity volume and shape are achieved, and then stop pumping.

2. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, In step 3, the applied physical energy field is at least one of electric pulse, microwave, and laser, and the injected high-temperature modified fluid is one of high-temperature steam, high-temperature gas, or high-temperature water.

3. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, In step 3, the in-situ modification treatment is to inject high-temperature steam. The temperature of the injected high-temperature steam is 300-600℃. The high-temperature steam is injected into the target salt layer through a heat-insulated oil pipe. During the injection process, the wellhead temperature and pressure, bottom hole temperature and annulus pressure are monitored in real time to ensure that the wellbore string operates within safe conditions and to prevent the formation from being forced open. After stopping steam injection, shut in the well for 12-36 hours to allow the modification effect to fully penetrate or stabilize.

4. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, In step 4, slickwater with added drag reducer and clay stabilizer is selected as the fracturing fluid. When injecting the fracturing fluid, a step-by-step injection procedure is adopted, gradually increasing the injection rate from 1~3 m³ / min to 5~8 m³ / min.

5. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, In step 4, while injecting the fracturing fluid, the pressure is monitored simultaneously. Once formation fracturing is indicated, the fracturing fluid is continuously pumped at the maximum displacement. The preset value is 40% to 60% of the designed cavity radius.

6. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, In step 6, during the initial and middle stages of cavity construction, the water injection rate is 150 m³ / h to 300 m³ / h; at the same time, the concentration and temperature of the discharged brine are monitored to assess the progress of volumetric erosion.

7. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, In step 6, when sonar monitoring shows that the cavity volume has reached 50% of the design, the cavity construction phase begins and the reverse circulation mode is switched. When the top shape of the cavity approaches the design boundary, the cavity construction phase begins.

8. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, It also includes the following steps: Step 7: After stopping the pump, assess the stability and sealing of the cavity. Once the requirements are met, the construction of the salt cavern gas storage facility is complete.

9. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, During the cavity construction process in step 6, the concentration and temperature of the discharged brine and the internal pressure of the cavity are continuously monitored, and sonar cavity measurement is used to assess the cavity development status in real time and guide the adjustment of circulation parameters.

10. The efficient construction method for salt cavern energy storage based on in-situ modification according to claim 1, characterized in that, In step 1, the cavity is constructed in an abandoned horizontal solution cavity or a salt rock layer; When the cavity is located in an abandoned horizontal karst cavity, based on historical production data, downhole sonar detection and mechanical analysis, the cavity roof is stable, the wellbore can be repaired and can bear pressure, and there is a thick high-grade salt layer around it that can be used for further dissolution and expansion of the old salt rock cavity. The work to complete a production casing well includes: well workover, running a new casing of slightly smaller size into the original casing and cementing it, and restoring the mechanical integrity and sealing of the well. When the cavity construction location is a salt rock layer, the target salt layer should be selected based on its burial depth, thickness, and grade to meet the engineering implementation requirements of subsequent in-situ modification, controlled fracturing, and convection cavity construction, and the target salt layer should be free of penetrating fault defects for cavity construction. The operation of the production casing well includes: drilling, cementing, and completion of the production casing well, followed by well workover to ensure that the inner wall of the casing is smooth, free of burrs and deformation, to meet the requirements for smooth running and sealing of subsequent fracturing tubing and cavity construction tubing.

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