A salt cavern gas storage cavity formation partial dissolution experimental device and experimental method

Abstract

The present invention discloses a salt cavern gas storage cavity formation partial dissolution experimental device and experimental method, comprising a container, a sealing plug is provided at the opening of the container, a water injection pipe string, an oil injection pipe string and a brine drainage pipe string are inserted into the sealing plug, one end of the water injection pipe string, the oil injection pipe string and the brine drainage pipe string extends into the container, and the other end extends out of the top of the sealing plug and is connected to the water injection system, the oil injection system and the brine drainage system respectively, the water injection system comprises a water injection pump and a water injection pipeline, the water injection pipeline is provided with a flow meter and a water injection valve, the oil injection system comprises an oil injection pump and an oil injection pipeline, the oil injection pipeline is provided with an oil injection valve, the brine drainage system comprises a brine drainage pipeline and a graduated cylinder, and the brine drainage pipeline is provided with a brine drainage valve and a salt concentration meter. The present invention can simulate the water-soluble cavity formation process, study the influence of different factors on the partial dissolution of the cavity, calculate the partial dissolution coefficient, obtain the partial dissolution law, adjust the on-site cavity formation construction plan, and provide experimental support for obtaining a gas storage cavity with regular morphology and stability.

Description

Technical Field

[0001] The invention relates to a partial dissolution experimental device and an experimental method, and in particular to a partial dissolution experimental device and an experimental method for a salt cavern gas storage cavity. Background Art

[0002] Underground gas storage (UGS) is gaining increasing attention in many countries due to its irreplaceable role and significant advantages in peak load regulation and ensuring gas supply security. Data indicates that approximately 10% of global natural gas consumption is supplied by UGS. Salt cavern gas storage, one of the four major types of UGS, is gaining increasing popularity due to its flexible injection and production capabilities, high throughput, and excellent economic benefits.

[0003] Salt cavern gas storage utilizes a cavity created by injecting water into underground salt formations to dissolve salt, creating a storage space for natural gas. These caverns are typically located at depths of 800 to 1500 meters, with diameters ranging from 70 to 80 meters, up to 110 meters, and heights of around 100 meters. They are hollow and can be used to store natural gas, crude oil, helium, hydrogen, nuclear waste, and other materials. Due to their large size, a stable cavity structure is crucial for the safe operation of salt cavern gas storage. Severe partial dissolution can lead to collapse, potentially causing natural gas leaks or pipe string breakage. Therefore, preventing partial dissolution during the water injection process is a key concern for salt cavern gas storage designers and researchers. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a salt cavern gas storage cavity partial dissolution experimental device and experimental method, which can simulate the water dissolution cavity creation process, study the influence of different factors on the partial dissolution of the salt cavern gas storage cavity, and thus adjust the on-site cavity creation construction plan.

[0005] Technical solution: The present invention includes a container, a sealing plug is provided at the opening of the container, a water injection pipe column, an oil injection pipe column and a brine drainage pipe column are inserted into the sealing plug, one end of the water injection pipe column, the oil injection pipe column and the brine drainage pipe column extends into the container, and the other end extends out of the top of the sealing plug and is connected to the water injection system, the oil injection system and the brine drainage system respectively.

[0006] The water injection system comprises a water injection pump and a water injection pipeline, one end of the water injection pipeline is connected to the water injection pump, and the other end is connected to the water injection pipe column.

[0007] The water injection pipeline is provided with a flow meter and a water injection valve for controlling the opening and closing of the water injection pipeline.

[0008] The oil injection system comprises an oil injection pump and an oil injection pipeline, one end of the oil injection pipeline is connected to the oil injection pump, and the other end is connected to the oil injection pipe column.

[0009] The oil filling pipeline is provided with an oil filling valve for controlling the opening and closing of the oil filling system.

[0010] The brine discharge system includes a brine discharge pipeline and a measuring cylinder. One end of the brine discharge pipeline is connected to the brine discharge column, and the other end is placed above the measuring cylinder, and the measuring cylinder is used to collect brine.

[0011] The brine discharge pipeline is provided with a brine discharge valve and a salt concentration meter, and the brine concentration is measured and recorded regularly by the salt concentration meter.

[0012] The experimental method using the above-mentioned salt cavern gas storage cavity formation partial dissolution experimental device includes the following steps:

[0013] Step 1: Prepare a salt rock sample, drill a hole in the salt rock sample, and place the sample in a container;

[0014] Step 2: Calculate the amount of fresh water V required to fill the cavity to the required height.

[0015] Step 3: Insert the water injection string and the oil injection string into the set position, and insert the brine drainage string into the sealing plug so that the bottom of the brine drainage string is flush with the bottom of the sealing plug;

[0016] Step 4: Open the water injection system and the brine drainage system, inject a volume of V of fresh water into the borehole, and then close the water injection system;

[0017] Step 5: Open the oil injection system and inject oil into the borehole. At the same time, exhaust the air in the borehole from the brine exhaust pipe. After the borehole is filled with oil, close the oil injection system.

[0018] Step 6: Insert the brine drainage pipe column to the set position so that the end of the brine drainage pipe column is below the oil-water interface between the oil and fresh water;

[0019] Step 7: Open the water injection system to inject water and create a cavity, and discharge the generated brine from the brine drainage pipe column, observe and record the salt rock dissolution. When the dissolution reaches the boundary between the salt rock and the container, close the water injection system and the brine drainage system;

[0020] Step 8. After the experiment is completed, take out the salt rock sample, cut it along the cross section where the salt rock is dissolved to the boundary between the salt rock and the container, and calculate the partial solubility coefficient.

[0021] The amount of fresh water V = h × πR 2 , where R is the radius of the borehole on the salt rock sample used to insert the water injection string, oil injection string and brine drainage string; h is the height of the cavity section.

[0022] The partial solubility coefficient a=R max / R min , where R max is the maximum dissolution radius in the cross section, R min is the minimum dissolution radius.

[0023] Beneficial effects: The present invention can simulate the water-soluble cavity-making process, study the influence of different factors on the partial dissolution of the salt cavern gas storage cavity, calculate the partial dissolution coefficient according to the experimental results, obtain the partial dissolution law in the cavity-making process, adjust the on-site cavity-making construction plan, and provide experimental support for obtaining a regular and stable gas storage cavity, thereby facilitating the safe and efficient construction and operation of my country's salt cavern gas storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the overall structural diagram of the present invention;

[0025] Figure 2 It is a schematic diagram of an implementation of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] like Figure 1 and Figure 2 As shown, the present invention includes a glass container with graduated markings. To maintain consistency with an actual cavity, the glass container adopts a quasi-spherical structure, as long as its cross-section is circular. In this embodiment, the glass container is a spherical glass container. The spherical glass container is divided into upper and lower parts. A sealing ring 5 is provided between the upper and lower hemispheres. The sealing ring 5 provides a seal to prevent leakage after the injection of fresh water or oil. Handles are provided at the maximum diameter of the spherical glass container. The handles are respectively located on the outer sides of the upper and lower hemispheres. The handles have bolt holes, which can be used to secure the handles of the upper and lower hemispheres to form a complete spherical glass container.

[0028] The bottom of the glass container is flat and can be placed stably on the test bench. The glass container is connected to the water injection system, oil injection system and brine discharge system. A sealing plug is provided at the opening of the spherical glass container. A water injection pipe column 12, an oil injection pipe column 10 and a brine discharge pipe column 11 are inserted into the sealing plug. One end of the water injection pipe column 12, the oil injection pipe column 10 and the brine discharge pipe column 11 extends into the glass container, and the other end extends out of the top of the sealing plug and is connected to the water injection system, the oil injection system and the brine discharge system respectively.

[0029] The water injection system includes a water injection pump 2 and a water injection pipeline 3. One end of the water injection pipeline 3 is connected to the water injection pump 2 and the other end is connected to the water injection column 12. A flow meter 4 and a water injection valve are installed on the water injection pipeline 3. The oil injection system includes an oil injection pump 1 and an oil injection pipeline 6. One end of the oil injection pipeline 6 is connected to the oil injection pump 1 and the other end is connected to the oil injection column 10. An oil injection valve is installed on the oil injection pipeline 6. The brine drainage system includes a brine drainage pipeline 7 and a measuring cylinder 9. One end of the brine drainage pipeline 7 is connected to the brine drainage column 11 and the other end is placed above the measuring cylinder 9. The brine drainage pipeline 7 is equipped with a brine drainage valve and a salt concentration meter 8.

[0030] Salt rock was dissolved in a glass container to simulate the underground cavity creation environment. The effects of different insoluble matter contents, insoluble matter components, formation inclination, pipe position, water injection rate and other factors on the partial dissolution of the salt cavern gas storage cavity were studied. The partial dissolution coefficient was calculated based on the experimental results, and the partial dissolution law in the cavity creation process was obtained based on the experimental structure. The on-site cavity creation construction plan was then adjusted to provide support for obtaining a gas storage cavity with regular morphology and stability.

[0031] The experimental method of the present invention comprises the following steps:

[0032] Step 1: Prepare the rock salt sample according to the experimental objective. For example, when studying the effect of insoluble content on partial solubility in cavities, the following steps are performed: ① Take rock salt with varying insoluble content and cut it into a spherical shape according to the dimensions of a glass container. Drill three circular holes with a radius R in the center, sized to accommodate three pipes (water injection, oil injection, and brine drainage). Place the sample into the spherical glass container. ② Take salt powder and insoluble material (mudstone or anhydrite, etc.), according to the designed insoluble content and layered structure (the layered structure simulates strata), place them in a specialized mold the same size as the glass container, compact them (pressurize them to formation pressure), drill three circular holes in the center, and place them into the spherical glass container. Connect the upper and lower parts of the glass container with bolts and tighten them securely.

[0033] Step 2: Based on the cavity height h in the experimental plan (recommended to be between 1 / 6 and 5 / 6 of the total height of the glass container), calculate the amount of fresh water required to inject water to the salt rock cavity height h: V = h × πR 2 .

[0034] Step 3: Insert the water injection pipe and oil injection pipe into the set position through the sealing plug. Generally, the water injection pipe can be inserted to the bottom of the borehole, and the oil injection pipe can be inserted to the upper part of the borehole; insert the brine drainage pipe into the sealing plug, and the bottom of the brine drainage pipe is flush with the bottom of the sealing plug.

[0035] Step 4: Open the water injection pump, water injection valve and brine discharge valve, inject a volume of V of fresh water into the borehole, and then close the water injection pump and water injection valve.

[0036] Step 5: Open the oil injection pump and valve to inject a liquid that does not dissolve the salt rock. In this example, diesel is used as a dissolution inhibitor. This displaces the air in the borehole through the brine extraction column. Once the borehole is filled with diesel, close the oil injection pump and valve.

[0037] Step 6. Refer to the scale on the glass container and insert the brine drainage column to the set position. The end of the brine drainage column should be below the oil-water interface between diesel and fresh water.

[0038] Step 7: Turn on the injection pump and valve to begin injecting water to create a cavity. Fresh water dissolves the salt rock, turning it into brine, which is then discharged from the brine drainage column to the outside of the device. Collect the brine with a graduated cylinder and regularly measure and record the brine concentration using a salt concentration meter. Record the flow rate on the flow meter, the experimental time, and other parameters. Observe and record the salt rock dissolution, noting the location and time when dissolution reaches the boundary between the salt rock and the glass container. You can take photos to document this for experimental analysis. When dissolution reaches the boundary between the salt rock and the glass container, turn off the injection pump, injection valve, and brine drainage valve.

[0039] Step 8. Open the glass container, take out the salt rock sample, cut along the cross section where the salt rock is dissolved to the boundary between the salt rock and the glass container, observe and take photos to record the salt rock dissolution, and measure the maximum dissolution radius R in the cross section. max and the minimum dissolution radius R min , calculate the partial solubility coefficient a=R max / R min .

[0040] Step 9: Repeat step 1 to adjust the insoluble matter content, and repeat steps 2 to 8 to study the effect of different insoluble matter contents on the partial solubility of the cavity.

[0041] When studying other factors affecting partial solubility, such as insoluble matter components, formation dip, tubing position, and water injection rate, repeat steps 1 to 9 and change the research factors.

Claims

1. An experimental method for a salt cavern gas storage cavity formation partial dissolution experimental device, characterized in that: The invention comprises a salt cavern gas storage cavity formation partial dissolution experimental device, which comprises a container, the container adopts a spherical structure, and its cross section is circular, a sealing plug is provided at the opening of the container, a water injection pipe string, an oil injection pipe string and a brine drainage pipe string are inserted into the sealing plug, one end of the water injection pipe string, the oil injection pipe string and the brine drainage pipe string extends into the container, and the other end extends out of the top of the sealing plug and is connected to the water injection system, the oil injection system and the brine drainage system respectively; the specific experimental method comprises the following steps: Step 1: Prepare a salt rock sample, drill a hole in the salt rock sample, and place the sample in a container; Step 2: Calculate the amount of fresh water V required to fill the cavity to the required height. Step 3: Insert the water injection string and the oil injection string into the set position, and insert the brine drainage string into the sealing plug so that the bottom of the brine drainage string is flush with the bottom of the sealing plug; Step 4: Open the water injection system and the brine drainage system, inject a volume of water V into the borehole, and then close the water injection system; Step 5: Open the oil injection system and inject oil into the borehole. At the same time, exhaust the air in the borehole from the brine exhaust pipe. After the borehole is filled with oil, close the oil injection system. Step 6: Insert the brine drainage pipe column to the set position so that the end of the brine drainage pipe column is below the oil-water interface; Step 7: Open the water injection system to inject water and create a cavity, and discharge the generated brine from the brine drainage pipe column, observe and record the salt rock dissolution. When the dissolution reaches the boundary between the salt rock and the container, close the water injection system and the brine drainage system; Step 8. After the experiment is completed, take out the salt rock sample, cut it along the cross section where the salt rock is dissolved to the boundary between the salt rock and the container, and calculate the partial solubility coefficient.

2. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 1 is characterized in that: The water injection system comprises a water injection pump and a water injection pipeline, one end of the water injection pipeline is connected to the water injection pump, and the other end is connected to the water injection pipe column.

3. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 2 is characterized in that: The water injection pipeline is provided with a flow meter and a water injection valve.

4. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 1 is characterized in that: The oil injection system comprises an oil injection pump and an oil injection pipeline, one end of the oil injection pipeline is connected to the oil injection pump, and the other end is connected to the oil injection pipe column.

5. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 4 is characterized in that: An oil filling valve is arranged on the oil filling pipeline.

6. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 1 is characterized in that: The brine discharge system comprises a brine discharge pipeline and a measuring cylinder. One end of the brine discharge pipeline is connected to the brine discharge column, and the other end is placed above the measuring cylinder.

7. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 6 is characterized in that: The brine discharge pipeline is provided with a brine discharge valve and a salt concentration meter.

8. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 1 is characterized in that: The amount of fresh water V=h×πR 2 , where R is the radius of the borehole on the salt rock sample used to insert the water injection string, oil injection string and brine drainage string; h is the height of the cavity section.

9. The experimental method of the salt cavern gas storage cavity creation partial dissolution experimental device according to claim 1, characterized in that: The partial solubility coefficient a=R max / R min , where R max is the maximum dissolution radius in the cross section, R min is the minimum dissolution radius.

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