Halogen cycle salt rock stress relaxation experimental device and method

Abstract

The invention discloses a halogen cycle salt rock stress relaxation experiment device and method, the halogen cycle salt rock stress relaxation experiment device comprises a container body and a container cover connected with the container body, a sealing ring is arranged between the container body and the container cover, and the halogen cycle salt rock stress relaxation experiment device further comprises a force application device, a hydrogen injection and discharge device and a brine injection and discharge device; according to the device and the method, the influence of the hydrogen and brine alternate action on the rock core stress relaxation characteristic can be researched, the accuracy of a rock core stress relaxation experiment result can be improved, and then researchers can more accurately grasp the rheological characteristic of the salt cavern hydrogen storage reservoir surrounding rock under the long-term hydrogen and brine alternate injection and production condition.

Description

Technical Field

[0001] The invention relates to the technical fields of salt cavern hydrogen storage and rock damage mechanics, and in particular to a salt rock stress relaxation test method and device. Background Art

[0002] Hydrogen storage is the most critical part of the current energy strategy development. Compared with other storage methods, geological hydrogen storage has the highest energy storage capacity. Geological hydrogen storage sites include salt caverns, depleted oil and gas reservoirs, aquifers, etc. Due to the active nature of hydrogen, it is very easy to react with minerals and microorganisms in the formation. In addition, due to the small molecular volume and high activity of hydrogen, it is very easy to penetrate into the rock formation to produce high pore pressure. These processes seriously affect the physical and mechanical properties of the rock. In addition, the repeated erosion of brine during the injection and production of the reservoir reduces the fracture toughness of the cracks in the rock and some pores are dissolved and penetrated, making it easier for hydrogen to enter. Therefore, the alternating action of hydrogen and brine significantly affects the rheological properties of the surrounding rock.

[0003] The rheological properties of rock formations are the key factors that determine the long-term stability of the reservoir. Stress relaxation is a method to study the rheological properties of rocks, especially for "soft rocks" such as salt rock and mudstone. The rheological properties are very significant. During the long operation of the hydrogen storage reservoir, the surrounding rock will frequently experience the alternating effects of high-pressure hydrogen and brine. Studying the relaxation characteristics of rocks under the alternating effects of brine and hydrogen is crucial to accurately control the rheological characteristics of rocks and construct constitutive equations.

[0004] However, when conducting stress relaxation experiments on hydrogen storage salt cavern cores, the experimental equipment used cannot simulate the impact of the alternating effects of hydrogen and brine on the core, and therefore cannot accurately control the impact of the alternating effects of hydrogen and brine on the damage and rheological characteristics of the salt cavern surrounding rock. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a hydrogen-halogen cycle salt rock stress relaxation experimental device and method to solve the technical problem that the existing core stress relaxation experimental device cannot simulate the influence of the alternating effects of hydrogen and brine on the stress relaxation characteristics of the core, resulting in insufficient accuracy of the stress relaxation experimental results.

[0006] The hydrogen-halogen cycle salt rock stress relaxation experimental device of the present invention comprises a container, wherein the container comprises a container body and a container cover connected to the container body, a sealing ring is arranged between the container body and the container cover, and the hydrogen-halogen cycle salt rock stress relaxation experimental device of the present invention also comprises a force applying device, a hydrogen injection and discharge device and a brine injection and discharge device.

[0007] A pressure sensor is provided at the inner bottom of the container body, and a support plate for carrying the core is connected to the pressure sensor; an air pressure sensor for measuring the air pressure in the container and a liquid level sensor for measuring the height of the brine liquid level are provided on the container cover;

[0008] The force-applying device comprises a support frame, a servo electric cylinder arranged on the support frame and a force-applying column arranged on the container cover, the container cover is provided with an axial hole in the middle portion thereof for slidingly cooperating with the force-applying column up and down, the force-applying column is provided with a sealing ring or a sealing sleeve for slidingly cooperating with the axial hole, and the force-applying column is used to transmit pressure and displacement between the telescopic rod of the servo electric cylinder and the rock core;

[0009] The hydrogen injection and discharge device comprises a high-pressure hydrogen cylinder, a hydrogen recovery cylinder, a gas pipe joint arranged on the upper part of the container body, a gas injection pipeline connecting the high-pressure hydrogen cylinder and the gas pipe joint, and a gas return pipeline connecting the hydrogen recovery cylinder and the gas pipe joint; a gas injection flow control valve is arranged on the gas injection pipeline, and a gas return flow control valve is arranged on the gas return pipeline;

[0010] The brine injection and discharge device includes a brine container, a high-pressure water pump, a water pipe joint arranged at the lower part of the container body, an injection pipeline connecting the high-pressure water pump and the water pipe joint, and a return pipeline connecting the water pipe joint and the brine container, the injection pipeline is provided with an injection flow control valve, and the return pipeline is provided with a return water flow control valve.

[0011] Furthermore, the hydrogen-halogen cycle salt rock stress relaxation experimental device also includes an acoustic emission probe arranged at the lower end of the force-applying column and the top of the support plate.

[0012] The present invention also discloses an experimental method according to the above-mentioned hydrogen-halogen cycle salt rock stress relaxation experimental device, which comprises the following steps:

[0013] 1) Remove the container cover, apply vaseline on the upper and lower ends of the core, then place the core on the support plate and cover the container cover;

[0014] 2) Apply pre-pressure to the core through the servo electric cylinder, so that the upper and lower ends of the core are in contact with the force-applying column and the support plate respectively, and then the ultrasonic wave is excited by the acoustic emission probe to measure the speed of the sound wave in the initial core;

[0015] 3) Apply relaxation strain to the core through the servo electric cylinder, and start recording the stress value of the pressure sensor at the same time;

[0016] 4) Perform hydrogen-brine cycle injection and drainage operation during core stress relaxation:

[0017] a) Close the return air flow control valve, water injection flow control valve and return water flow control valve, open the gas injection flow control valve to inject hydrogen into the container, monitor the air pressure in the container through the air pressure sensor, and close the gas injection flow control valve when the air pressure reaches the set value;

[0018] b) Brine injection and exhaust: open the return air flow control valve, water injection flow control valve and high-pressure water pump to allow brine to enter the container and hydrogen to enter the hydrogen recovery bottle; monitor the air pressure in the container through the air pressure sensor, and adjust the opening of the return air flow control valve and the water injection flow control valve according to the pressure value monitored by the air pressure sensor, so that the air pressure in the container is stable within the set range or fluctuates according to the set rule; monitor the liquid level position of the brine in the container through the liquid level sensor, and when the liquid level reaches the set value, close the return air flow control valve, water injection flow control valve and high-pressure water pump; before injecting brine into the container and exhausting the air, turn on the acoustic emission probe to excite ultrasonic waves and measure the acoustic wave velocity in the core once; after injecting brine into the container and exhausting the air, turn on the acoustic emission probe to excite ultrasonic waves and measure the acoustic wave velocity in the core once;

[0019] c) Injecting gas to remove brine: Open the gas injection flow control valve and the water return flow control valve to allow the hydrogen in the high-pressure hydrogen bottle to enter the container and the brine in the container to flow back into the brine container; monitor the air pressure in the container through the air pressure sensor, and adjust the opening of the air return flow control valve and the water injection flow control valve according to the pressure value monitored by the air pressure sensor, so that the air pressure in the container is stable within the set range or fluctuates according to the set rule; monitor the liquid level position of the brine in the container through the liquid level sensor, and close the gas injection flow control valve and the water return flow control valve when the liquid level drops to the set value; before injecting gas into the container to remove brine, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once; after injecting gas into the container to remove brine, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once;

[0020] d) Repeat steps b) and c) until the experiment is completed.

[0021] Beneficial effects of the present invention:

[0022] 1. The hydrogen-halogen cycle salt rock stress relaxation experimental device and method of the present invention can realize the study of the influence of the alternating effects of hydrogen and brine on the stress relaxation characteristics of the core, can improve the accuracy of the core stress relaxation experimental results, and further ensure that researchers can more accurately grasp the rheological characteristics of the surrounding rock of the salt cavern hydrogen storage reservoir under the conditions of long-term alternating injection and production of hydrogen and brine.

[0023] 2. The present invention monitors the acoustic wave velocity in the rock core during the stress relaxation experiment, thereby providing data support for subsequent analysis of damage and fracture changes inside the rock core during the stress relaxation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the hydrogen-halogen cycle salt rock stress relaxation experimental device. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] As shown in the figure, the salt rock stress relaxation experimental device for hydrogen-halogen cycle in this embodiment includes a container, which includes a container body 1 and a container cover 2 connected to the container body, and a sealing ring 3 is provided between the container body and the container cover. The salt rock stress relaxation experimental device for hydrogen-halogen cycle in this embodiment also includes a force application device, a hydrogen injection and discharge device, and a brine injection and discharge device.

[0027] The inner bottom of the container body is provided with a pressure sensor 4, to which a support plate 6 for carrying a core 5 is connected; the container cover is provided with an air pressure sensor 7 for measuring the air pressure in the container and a liquid level sensor 8 for measuring the height of the brine liquid level. There are many types of liquid level sensors, which can be selected according to needs in specific implementation.

[0028] The force-applying device includes a support frame 9, a servo electric cylinder 10 arranged on the support frame and a force-applying column 11 arranged on the container cover. The middle part of the container cover is provided with an axial hole that slides up and down with the force-applying column. The force-applying column is provided with a sealing sleeve 11 that slides and seals with the axial hole. Of course, in different embodiments, the sealing sleeve 11 can also be replaced by a sealing ring; the force-applying column is used to transmit pressure and displacement between the telescopic rod of the servo electric cylinder and the rock core.

[0029] The hydrogen injection and discharge device includes a high-pressure hydrogen cylinder 12, a hydrogen recovery bottle 13, a gas pipe joint 14 arranged on the upper part of the container body, a gas injection pipeline connecting the high-pressure hydrogen cylinder and the gas pipe joint, and a gas return pipeline connecting the hydrogen recovery bottle and the gas pipe joint; a gas injection flow control valve 15 is arranged on the gas injection pipeline, and a gas return flow control valve 16 is arranged on the gas return pipeline.

[0030] The brine injection and discharge device includes a brine container 17, a high-pressure water pump 18, a water pipe joint 19 arranged at the lower part of the container body, an injection pipeline connecting the high-pressure water pump and the water pipe joint, and a return pipeline connecting the water pipe joint and the brine container, the injection pipeline is provided with an injection flow control valve 20, and the return pipeline is provided with a return water flow control valve 21.

[0031] As an improvement to the above embodiment, the hydrogen-halogen cycle salt rock stress relaxation experimental device also includes an acoustic emission probe 22 arranged at the lower end of the force-applying column and the top of the support plate. The acoustic emission probe 22 is an excitable acoustic emission probe that can excite ultrasonic waves by itself.

[0032] The stress relaxation test method using the hydrogen-halogen cycle salt rock stress relaxation test device in the above embodiment includes the following steps:

[0033] 1) Remove the container cover, apply vaseline on the upper and lower ends of the core sampled from the salt rock, then place the core on the support plate and cover the container cover. The purpose of applying vaseline is: first, to reduce the end effect of the core specimen, and second, to avoid the air between the end face of the core and the support plate and the force column affecting the wave velocity measurement.

[0034] 2) Pre-pressure is applied to the core through the servo electric cylinder. The pre-pressure can be set by yourself. It is generally more appropriate to set it at 0.5kN. By applying pre-pressure, the upper and lower ends of the core are respectively in contact with the force column and the support plate. Then, ultrasonic waves are excited by the acoustic emission probe to measure the speed of the sound waves in the initial core.

[0035] 3) Apply relaxation strain to the core through the servo electric cylinder, and start recording the stress value of the pressure sensor at the same time. The relaxation pre-strain should be less than the elastic strain limit of the core, and the elastic strain limit of the core can be measured experimentally before the relaxation strain experiment. In the specific implementation, the relaxation strain amount can be set to different gradient levels, or multi-step relaxation can be performed.

[0036] 4) Perform hydrogen-brine cycle injection and drainage operation during core stress relaxation:

[0037] a) Close the return air flow control valve, water injection flow control valve and return water flow control valve, open the gas injection flow control valve to inject hydrogen into the container, monitor the air pressure in the container through the air pressure sensor, and close the gas injection flow control valve when the air pressure reaches the set value.

[0038] b) Brine injection and exhaust: open the return air flow control valve, water injection flow control valve and high-pressure water pump to allow brine to enter the container and hydrogen to enter the hydrogen recovery bottle; monitor the air pressure in the container through the air pressure sensor, and adjust the opening of the return air flow control valve and the water injection flow control valve according to the pressure value monitored by the air pressure sensor, so that the air pressure in the container is stable within the set range or fluctuates according to the set rule; monitor the liquid level position of the brine in the container through the liquid level sensor, and when the liquid level reaches the set value, close the return air flow control valve, water injection flow control valve and high-pressure water pump; before injecting brine into the container and exhausting the air, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once; after injecting brine into the container and exhausting the air, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once.

[0039] c) Injection of gas to remove brine: Open the gas injection flow control valve and the return water flow control valve to allow the hydrogen in the high-pressure hydrogen bottle to enter the container and the brine in the container to flow back into the brine container; monitor the air pressure in the container through the air pressure sensor, and adjust the opening of the return air flow control valve and the water injection flow control valve according to the pressure value monitored by the air pressure sensor, so that the air pressure in the container is stabilized within the set range or fluctuates according to the set rule; monitor the liquid level position of the brine in the container through the liquid level sensor, and close the gas injection flow control valve and the return water flow control valve when the liquid level drops to the set value; before injecting gas into the container to remove brine, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once; after injecting gas into the container to remove brine, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once.

[0040] d) Repeat steps b) and c) until the experiment is completed.

[0041] By using the above-mentioned hydrogen-brine cycle salt rock stress relaxation experimental device, stress relaxation tests under the action of hydrogen and brine can also be carried out separately. In this way, the stress relaxation test results under different conditions can be compared and analyzed to more accurately understand the effect of hydrogen-brine cycle alternating injection and discharge on salt rock stress relaxation.

[0042] By monitoring the acoustic wave velocity in the core in the above experiment and analyzing the change in the wave velocity, we can know the changes in the damage and fracture inside the core during the stress relaxation process.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A salt rock stress relaxation experimental device for hydrogen-halogen cycle, comprising a container, wherein the container comprises a container body and a container cover connected to the container body, and a sealing ring is arranged between the container body and the container cover, characterized in that: It also includes a force application device, a hydrogen injection and discharge device, and a brine injection and discharge device; A pressure sensor is provided at the inner bottom of the container body, and a support plate for carrying the core is connected to the pressure sensor; an air pressure sensor for measuring the air pressure in the container and a liquid level sensor for measuring the height of the brine liquid level are provided on the container cover; The force-applying device comprises a support frame, a servo electric cylinder arranged on the support frame and a force-applying column arranged on the container cover, the container cover is provided with an axial hole in the middle portion thereof for slidingly cooperating with the force-applying column up and down, the force-applying column is provided with a sealing ring or a sealing sleeve for slidingly cooperating with the axial hole, and the force-applying column is used to transmit pressure and displacement between the telescopic rod of the servo electric cylinder and the rock core; The hydrogen injection and discharge device comprises a high-pressure hydrogen cylinder, a hydrogen recovery cylinder, a gas pipe joint arranged on the upper part of the container body, a gas injection pipeline connecting the high-pressure hydrogen cylinder and the gas pipe joint, and a gas return pipeline connecting the hydrogen recovery cylinder and the gas pipe joint; a gas injection flow control valve is arranged on the gas injection pipeline, and a gas return flow control valve is arranged on the gas return pipeline; The brine injection and discharge device includes a brine container, a high-pressure water pump, a water pipe joint arranged at the lower part of the container body, an injection pipeline connecting the high-pressure water pump and the water pipe joint, and a return pipeline connecting the water pipe joint and the brine container, the injection pipeline is provided with an injection flow control valve, and the return pipeline is provided with a return water flow control valve.

2. The hydrogen-halogen cycle salt rock stress relaxation experimental device according to claim 1, characterized in that: The utility model also comprises an acoustic emission probe which is arranged at the lower end of the force applying column and the top of the supporting plate.

3. An experimental method for the hydrogen-halogen cycle salt rock stress relaxation experimental device according to claim 2, characterized in that: The following steps are involved: 1) Remove the container cover, apply vaseline on the upper and lower ends of the core, then place the core on the support plate and cover the container cover; 2) Apply pre-pressure to the core through the servo electric cylinder, so that the upper and lower ends of the core are in contact with the force-applying column and the support plate respectively, and then the ultrasonic wave is excited by the acoustic emission probe to measure the speed of the sound wave in the initial core; 3) Apply relaxation strain to the core through the servo electric cylinder, and start recording the stress value of the pressure sensor at the same time; 4) Perform hydrogen-brine cycle injection and drainage operation during core stress relaxation: a) Close the return air flow control valve, water injection flow control valve and return water flow control valve, open the gas injection flow control valve to inject hydrogen into the container, monitor the air pressure in the container through the air pressure sensor, and close the gas injection flow control valve when the air pressure reaches the set value; b) Brine injection and exhaust: open the return air flow control valve, water injection flow control valve and high-pressure water pump to allow brine to enter the container and hydrogen to enter the hydrogen recovery bottle; monitor the air pressure in the container through the air pressure sensor, and adjust the opening of the return air flow control valve and the water injection flow control valve according to the pressure value monitored by the air pressure sensor, so that the air pressure in the container is stable within the set range or fluctuates according to the set rule; monitor the liquid level position of the brine in the container through the liquid level sensor, and when the liquid level reaches the set value, close the return air flow control valve, water injection flow control valve and high-pressure water pump; before injecting brine into the container and exhausting the air, turn on the acoustic emission probe to excite ultrasonic waves and measure the acoustic wave velocity in the core once; after injecting brine into the container and exhausting the air, turn on the acoustic emission probe to excite ultrasonic waves and measure the acoustic wave velocity in the core once; c) Injecting gas to remove brine: Open the gas injection flow control valve and the water return flow control valve to allow the hydrogen in the high-pressure hydrogen bottle to enter the container and the brine in the container to flow back into the brine container; monitor the air pressure in the container through the air pressure sensor, and adjust the opening of the air return flow control valve and the water injection flow control valve according to the pressure value monitored by the air pressure sensor, so that the air pressure in the container is stable within the set range or fluctuates according to the set rule; monitor the liquid level position of the brine in the container through the liquid level sensor, and close the gas injection flow control valve and the water return flow control valve when the liquid level drops to the set value; before injecting gas into the container to remove brine, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once; after injecting gas into the container to remove brine, turn on the acoustic emission probe to excite ultrasonic waves and measure the sound wave velocity in the core once; d) Repeat steps b) and c) until the experiment is completed.

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