Salt cavern compressed air energy storage alternating load cement sheath evaluation experiment device and method

Abstract

The invention relates to a salt cavern compressed air energy storage alternating load cement sheath evaluation experiment device and method, and belongs to the technical field of salt cavern compressed air energy storage. Comprising a data acquisition and display system, a confining pressure system arranged on the side wall of the cement sheath and used for pressurizing the side wall of the cement sheath, and axial pressurizing systems arranged at the two ends of the cement sheath and used for pressurizing the end parts of the cement sheath, the casing pipe penetrates through the axial pressurizing system and the cement sheath, the bottom of the casing pipe is closed, the pressurizing system is used for pressurizing the interior of the casing pipe, and the cement sheath is provided with a stress-strain sensor, a sonic sensor and a temperature sensor. The data acquisition and display system is used for recording and analyzing readings of the stress-strain sensor, the sonic sensor and the temperature sensor; according to the invention, axial pressure, confining pressure and alternating pressure in the casing pipe can be applied at the same time, and stress, strain, vibration, temperature response and the like of the cement sheath under the action of multiple alternating loads can be monitored in real time, so that accurate evaluation on the long-term sealing integrity of the cement sheath is realized.

Description

Technical Field

[0001] This invention belongs to the field of salt cavern compressed air energy storage technology, and specifically relates to an experimental device and method for evaluating cement rings under alternating loads in salt cavern compressed air energy storage. Background Technology

[0002] Compressed air energy storage (CAES) in salt caverns is a key supporting technology for building new power systems. Its operation is characterized by periodic (daily or every few days) gas injection (storage) and gas extraction (release), resulting in significant and frequent pressure fluctuations within the wellbore. As a crucial barrier ensuring wellbore integrity, the cement sheath is highly susceptible to damage such as micro-annular gaps and micro-cracks under this complex "breathing" load. These damages accumulate gradually, eventually leading to seal failure, gas leakage, and significant economic losses and safety risks.

[0003] Currently, conventional methods for evaluating the performance of cement rings in the laboratory (such as triaxial compressive strength testing) have significant shortcomings: Static loading: It can only test the ultimate strength of cement sheath under constant load, and cannot simulate the actual periodic pressure fluctuations downhole.

[0004] The working conditions are singular: it is difficult to simultaneously reproduce the complex stress state of the downhole cement sheath, which is coupled with the axial stress, radial confining pressure and alternating pressure from inside the casing.

[0005] The evaluation indicators are incomplete: they mainly focus on the final failure strength, but lack real-time monitoring and evaluation methods for the performance evolution of cement rings under alternating loads (such as plastic deformation accumulation, stiffness degradation, damage initiation and propagation).

[0006] Therefore, developing an experimental device that can accurately simulate the actual working conditions of salt cavern CAES wells and evaluate the long-term performance of cement sheaths under alternating loads in real time and online is of vital importance for the selection of cementing materials, optimization of well structure, and safety assessment of energy storage reservoirs. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides an experimental apparatus and method for evaluating cement rings under alternating loads and compressed air energy storage in salt caverns, thereby improving the accuracy of the evaluation.

[0008] To achieve the above objectives, the present invention provides the following solution: An experimental apparatus for evaluating alternating load cement rings in salt cavern compressed air energy storage includes a data acquisition and display system, a confining pressure system installed on the sidewalls of the cement ring and pressurizing the sidewalls, an axial pressurizing system installed at both ends of the cement ring and pressurizing the ends, a sleeve passing through the axial pressurizing system and sealing the bottom of the cement ring, and a pressurizing system for pressurizing the inside of the sleeve. The cement ring is equipped with stress-strain sensors, acoustic sensors, and temperature sensors. The data acquisition and display system records and analyzes the readings of the stress-strain sensors, acoustic sensors, and temperature sensors.

[0009] Preferably, it also includes a central sample chamber, and the confining pressure system includes a confining pressure chamber disposed inside the central sample chamber and surrounding the side wall of the cement ring, the confining pressure chamber being provided with a pressurizing pipe for connecting a pressurizing device, the pressurizing pipe passing through the central sample chamber and having a confining pressure control valve disposed at its upper part.

[0010] Preferably, the axial pressurization system includes hollow pressurization blocks disposed at both ends of the cement ring, with a portion of the hollow pressurization blocks disposed in the central sample chamber and abutting against the cement ring.

[0011] Preferably, the sleeve is an N80 laser cladding sleeve and penetrates the hollow pressure block.

[0012] Preferably, the pressurization system includes a pneumatic pressurization device connected to the sleeve, a pressure sensor and an electronic pressure relief valve installed on the pipe connecting the pneumatic pressurization device and the sleeve, and the pneumatic pressurization device is used to inject high-pressure gas into the sleeve.

[0013] Preferably, the stress-strain sensor, acoustic sensor, and temperature sensor are arranged in an array on the surface of the cement ring, and are respectively located in the region near the sleeve, the middle region of the cement ring, and the region near the confining pressure system.

[0014] The evaluation method for cement rings subjected to alternating loads in salt cavern compressed air energy storage includes the following steps: Preparation and curing of cement rings; After curing, the experiment was started. A constant confining pressure was applied to the cement ring through the confining pressure system, and a constant axial pressure was applied through the axial pressure system. The casing is periodically pressurized and depressurized according to a preset program to simulate the gas injection and production process of a CAES well. The stress-strain sensor, acoustic sensor, and temperature sensor embedded in the cement ring monitor the stress redistribution, strain development, acoustic signal, and temperature changes inside in real time. By analyzing the evolution of these data with the number of cycles, the fatigue life, damage accumulation, and sealing integrity of the cement ring are evaluated.

[0015] Preferably, the preparation and curing process of the cement ring is as follows: The N80 laser cladding sleeve is precisely fixed at the center of the central sample chamber; The stress-strain sensor, acoustic sensor, and temperature sensor, which have been pre-connected with wires, are arranged in the designed positions around the outer wall of the sleeve according to the preset scheme. The well-mixed cement slurry is poured into the annular space of the central sample chamber to avoid generating air bubbles and to ensure that the sensor position does not move.

[0016] Move the entire device to a constant temperature curing environment and perform curing according to API standards or a custom plan.

[0017] Preferably, the simulated gas injection and production process of a CAES well is as follows: set the upper and lower limits of the pressurization system, the pressurization rate, the depressurization rate, the holding time, and the total number of cycles; simulate daily cycles, setting a cycle from 12MPa to 18MPa and back to 12MPa to be completed every 12 hours, with a pressurization time of 8 hours and a depressurization time of 4 hours to simulate the daily charging and discharging of compressed air in the salt cavern compressed air energy storage tank, which is carried out hundreds of times.

[0018] Preferably, data analysis and evaluation: Stress-strain hysteresis loop: Analyze the stress-strain curve of the cement ring in each pressure cycle, observe the shape, area and movement of the hysteresis loop, and judge the energy dissipation and damage accumulation. Plastic strain accumulation: Record the unrecoverable plastic strain after each cycle, plot its growth curve with the number of cycles, and evaluate the material degradation rate; Stiffness degradation: Calculate the secant modulus for each cycle and observe its decreasing trend with the number of cycles; Critical failure determination: When a sudden change in stress, strain, and acoustic waves is detected, or the plastic strain exceeds the threshold, or macroscopic cracks appear, the cement ring is determined to have failed, and the number of cycles at this time is recorded as its fatigue life.

[0019] The present invention achieves the following technical effects compared to the prior art: This invention can simultaneously apply axial pressure, confining pressure, and alternating pressure inside the casing, and can monitor the stress, strain, vibration, and temperature response of the cement ring under multiple alternating loads in real time, thereby achieving an accurate evaluation of the long-term sealing integrity of the cement ring. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the present invention; The components include: 1. Central sample chamber; 2. Confining pressure chamber; 3. Hollow pressure block; 4. Cement ring; 5. N80 laser cladding sleeve; 6. Pneumatic pressurization device; 7. Electronic pressure relief valve; 8. Pressure sensor; 9. Confining pressure control valve; 10. Sensor; and 11. Data acquisition and display system. Detailed Implementation

[0022] 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.

[0023] This invention provides an experimental apparatus and method for evaluating cement rings under alternating loads and compressed air energy storage in salt caverns, thereby improving the accuracy of the evaluation.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] refer to Figure 1 An experimental device for evaluating the alternating load of a cement ring 4 in a salt cavern compressed air energy storage system includes a data acquisition and display system 11, a confining pressure system installed on the sidewall of the cement ring 4 to pressurize the sidewall, an axial pressure system installed at both ends of the cement ring 4 to pressurize the ends, a sleeve that passes through the axial pressure system and seals the bottom of the cement ring 4, and a pressure system for pressurizing the inside of the sleeve. The cement ring 4 is equipped with stress-strain sensors, acoustic sensors, and temperature sensors. The data acquisition and display system 11 records and analyzes the readings of the stress-strain sensors, acoustic sensors, and temperature sensors. This invention can simultaneously apply axial pressure, confining pressure, and alternating pressure inside the sleeve, and can monitor the stress, strain, vibration, and temperature response of the cement ring 4 under multiple alternating loads in real time, thereby achieving an accurate evaluation of the long-term sealing integrity of the cement ring 4.

[0026] refer to Figure 1It also includes a central sample chamber 1. The confining pressure system includes a confining pressure chamber 2 located inside the central sample chamber 1 and surrounding the side wall of the cement ring 4. The confining pressure chamber 2 is provided with a pressurizing pipe for connecting the pressurizing device. The pressurizing pipe passes through the central sample chamber 1 and is provided with a confining pressure control valve 9 at its upper part. The horizontal ground stress on the cement ring 4 is simulated by injecting pressurized silicone oil and other hydraulic media into it.

[0027] refer to Figure 1 The axial pressurization system includes hollow pressurization blocks 3 set at both ends of the cement ring 4. Part of the hollow pressurization blocks 3 is set in the central sample chamber 1 and abuts against the cement ring 4.

[0028] refer to Figure 1 The sleeve is an N80 laser clad sleeve 5, which penetrates the hollow pressure block 3.

[0029] refer to Figure 1 The pressurization system includes a pneumatic pressurization device 6 connected to the casing, a pressure sensor 8 and an electronic pressure relief valve 7 installed on the pipeline connecting the pneumatic pressurization device 6 and the casing. The pneumatic pressurization device 6 is used to inject high-pressure gas into the casing. The electronic pressure relief valve 7 is used to precisely control the pressure relief process, realize the periodic increase and decrease of the pressure in the casing, and simulate the alternating load of the injected and produced gas.

[0030] refer to Figure 1 Stress-strain sensors, acoustic sensors, and temperature sensors are arranged in an array on the surface of the cement ring 4, and are respectively located in the area near the sleeve, the middle area of ​​the cement ring 4, and the area near the confining pressure system. The sensor wires are arranged along the outside of the cement ring 4 and led out to the outside of the central sample chamber 1.

[0031] The evaluation method for salt cavern compressed air energy storage alternating load cement ring 4 of the present invention includes the following steps: Preparation and curing of cement ring 4; After curing, the experiment was started. A constant confining pressure was applied to cement ring 4 through the confining pressure system, and a constant axial pressure was applied through the axial pressure system. The casing is periodically pressurized and depressurized according to a preset program to simulate the gas injection and production process of a CAES well. The stress-strain sensor, acoustic sensor, and temperature sensor embedded in the cement ring 4 monitor the stress redistribution, strain development, acoustic signal, and temperature changes inside in real time. By analyzing the evolution of these data with the number of cycles, the fatigue life, damage accumulation degree, and sealing integrity of the cement ring 4 are evaluated.

[0032] Furthermore, the preparation and curing process of cement ring 4 is as follows: The N80 laser cladding sleeve 5 is precisely fixed at the center of the central sample chamber 1; The stress-strain sensor, acoustic sensor, and temperature sensor, which have been pre-connected with wires, are arranged in the designed positions around the outer wall of the sleeve according to the preset scheme. The well-mixed cement slurry was poured into the annular space of the central sample chamber 1 to avoid generating air bubbles and to ensure that the sensor position did not move.

[0033] Move the entire device to a constant temperature curing environment and perform curing according to API standards or a custom plan.

[0034] Furthermore, the gas injection and production process of the CAES well is simulated as follows: the upper and lower limits of the pressurization system, the pressurization rate, the depressurization rate, the holding time, and the total number of cycles are set; the daily cycle is simulated, and a cycle from 12MPa to 18MPa and back to 12MPa is completed every 12 hours, with a pressurization time of 8 hours and a depressurization time of 4 hours to simulate the daily charging and discharging of compressed air in the salt cavern compressed air energy storage tank, which is carried out hundreds of times.

[0035] Further data analysis and evaluation: Stress-strain hysteresis loop: Analyze the stress-strain curve of cement ring 4 in each pressure cycle, observe the shape, area and movement of the hysteresis loop, and judge the energy dissipation and damage accumulation. Plastic strain accumulation: Record the unrecoverable plastic strain after each cycle, plot its growth curve with the number of cycles, and evaluate the material degradation rate; Stiffness degradation: Calculate the secant modulus for each cycle and observe its decreasing trend with the number of cycles; Critical failure determination: When a sudden change in stress, strain and acoustic waves is detected, or the plastic strain exceeds the threshold, or macroscopic cracks appear, the cement ring 4 is determined to have failed, and the number of cycles at this time is recorded as its fatigue life.

[0036] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0037] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. An experimental apparatus for evaluating cement rings under alternating loads and compressed air energy storage in salt caverns, characterized in that, The system includes a data acquisition and display system, a confining pressure system installed on the sidewall of the cement ring to pressurize the sidewall, an axial pressure system installed at both ends of the cement ring to pressurize the ends, a sleeve passing through the axial pressure system and sealing the bottom of the cement ring, and a pressure system for pressurizing the inside of the sleeve. The cement ring is equipped with stress-strain sensors, acoustic sensors, and temperature sensors. The data acquisition and display system is used to record and analyze the readings of the stress-strain sensors, acoustic sensors, and temperature sensors.

2. The salt cavern compressed air energy storage alternating load cement ring evaluation experimental device according to claim 1, characterized in that, It also includes a central sample chamber. The confining pressure system includes a confining pressure chamber located inside the central sample chamber and surrounding the side wall of the cement ring. The confining pressure chamber is provided with a pressurizing pipe for connecting to a pressurizing device. The pressurizing pipe passes through the central sample chamber and is provided with a confining pressure control valve at its upper part.

3. The salt cavern compressed air energy storage alternating load cement ring evaluation experimental device according to claim 2, characterized in that, The axial pressurization system includes hollow pressurization blocks disposed at both ends of the cement ring, with a portion of the hollow pressurization blocks disposed in the central sample chamber and abutting against the cement ring.

4. The salt cavern compressed air energy storage alternating load cement ring evaluation experimental device according to claim 3, characterized in that, The sleeve is an N80 laser cladding sleeve and penetrates the hollow pressure block.

5. The salt cavern compressed air energy storage alternating load cement ring evaluation experimental device according to claim 4, characterized in that, The pressurization system includes a pneumatic pressurization device connected to the sleeve, a pressure sensor and an electronic pressure relief valve installed on the pipe connecting the pneumatic pressurization device and the sleeve, and the pneumatic pressurization device is used to inject high-pressure gas into the sleeve.

6. The experimental apparatus for evaluating cement rings under alternating loads and salt cavern compressed air energy storage according to claim 1, characterized in that, The stress-strain sensor, acoustic sensor, and temperature sensor are arranged in an array on the surface of the cement ring, and are respectively located in the region near the sleeve, the middle region of the cement ring, and the region near the confining pressure system.

7. A method for evaluating cement rings subjected to alternating loads and compressed air energy storage in salt caverns, characterized in that... The experimental apparatus for evaluating cement rings under alternating loads and salt cavern compressed air energy storage according to any one of claims 1 to 6 includes the following steps: Preparation and curing of cement rings; After curing, the experiment was started. A constant confining pressure was applied to the cement ring through the confining pressure system, and a constant axial pressure was applied through the axial pressure system. The casing is periodically pressurized and depressurized according to a preset program to simulate the gas injection and production process of a CAES well. The stress-strain sensor, acoustic sensor, and temperature sensor embedded in the cement ring monitor the stress redistribution, strain development, acoustic signal, and temperature changes inside in real time. By analyzing the evolution of these data with the number of cycles, the fatigue life, damage accumulation, and sealing integrity of the cement ring are evaluated.

8. The method for evaluating cement rings under alternating loads of salt cavern compressed air energy storage according to claim 7, characterized in that, The preparation and curing process of cement rings is as follows: The N80 laser cladding sleeve is precisely fixed at the center of the central sample chamber; The stress-strain sensor, acoustic sensor, and temperature sensor, which have been pre-connected with wires, are arranged in the designed positions around the outer wall of the sleeve according to the preset scheme. The well-mixed cement slurry is poured into the annular space of the central sample chamber to avoid generating air bubbles and to ensure that the sensor position does not move. Move the entire device to a constant temperature curing environment and perform curing according to API standards or a custom plan.

9. The method for evaluating cement rings under alternating loads of salt cavern compressed air energy storage according to claim 8, characterized in that, The gas injection and production process of a CAES well is simulated as follows: the upper and lower limits of the pressurization system, the pressurization rate, the depressurization rate, the holding time, and the total number of cycles are set; the daily cycle is simulated, and a cycle from 12MPa to 18MPa and back to 12MPa is completed every 12 hours, with a pressurization time of 8 hours and a depressurization time of 4 hours to simulate the daily charging and discharging of compressed air in the salt cavern compressed air energy storage tank, which is carried out hundreds of times.

10. The method for evaluating cement rings under alternating loads of salt cavern compressed air energy storage according to claim 9, characterized in that, Data Analysis and Evaluation: Stress-strain hysteresis loop: Analyze the stress-strain curve of the cement ring in each pressure cycle, observe the shape, area and movement of the hysteresis loop, and judge the energy dissipation and damage accumulation. Plastic strain accumulation: Record the unrecoverable plastic strain after each cycle, plot its growth curve with the number of cycles, and evaluate the material degradation rate; Stiffness degradation: Calculate the secant modulus for each cycle and observe its decreasing trend with the number of cycles; Critical failure determination: When a sudden change in stress, strain, and acoustic waves is detected, or the plastic strain exceeds the threshold, or macroscopic cracks appear, the cement ring is determined to have failed, and the number of cycles at this time is recorded as its fatigue life.

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