CN117538213B - Method for testing hydrogen diffusion coefficient of rock salt core - Google Patents

Abstract

The present application discloses a salt rock core hydrogen diffusion coefficient testing device and method, comprising a test gas chamber, a gas source and a pressure difference sensor, wherein the test gas chamber comprises a reference chamber and a sample chamber, wherein the reference chamber and the sample chamber are connected through a pipeline; the gas source comprises a helium gas source and a hydrogen gas source, so as to transport helium or hydrogen to the test gas chamber, wherein the helium gas source is used for container volume calibration, and the hydrogen gas source is used for hydrogen diffusion coefficient measurement; the high-pressure end of the pressure difference sensor is connected to the reference chamber, and the low-pressure end of the pressure difference sensor is connected to the sample chamber, so as to measure the pressure difference change between the reference chamber and the sample chamber during the test; the present application overcomes the problems of low accuracy in the diffusion coefficient test of highly penetrating small molecules and low-diffusivity rock salt, and has positive guiding significance for the measurement of hydrogen diffusion coefficient in salt rock and the evaluation of the sealing performance of salt cavern reservoirs.

Description

A method for testing hydrogen diffusion coefficient of salt rock core

Technical Field

The present application relates to the technical field of underground salt cavern gas storage, and in particular to a salt rock core hydrogen diffusion coefficient testing device and method.

Background Art

In recent years, my country's clean energy industry has grown stronger and stronger, and hydrogen has become one of the most promising clean energy sources due to its low pollution, high calorific value and zero pollution. As a secondary energy source, hydrogen is not only a power fuel and industrial raw material, but also an effective carrier of energy such as electricity. In the hydrogen energy industry, long-term and large-scale storage is a vital link. Salt caverns, as a high-quality underground storage space, have now been widely used for the storage of oil, natural gas, compressed air and hydrogen.

The sealing and safety of the reservoir are the premise and key to its construction and operation. Most of my country's salt rocks are layered structures, with different contents of impurities and non-salt interlayers, and the porosity and permeability characteristics fluctuate in a relatively large range. At the same time, hydrogen has a small mass and low viscosity, and has stronger penetrability. Therefore, the diffusion effect of hydrogen in the salt cavern wall cannot be ignored. Current research and methods mainly use the concentration changes at both ends of the rock sample to reflect the diffusion capacity of the gas in the core, but it is mainly for the core with extremely poor diffusion, the gas concentration changes are small, and the gradient concentration detection error during the experiment is large. In addition, the existing pressure change diffusion coefficient test equipment and methods, but it is mainly for large molecular gases and rocks with good pore connectivity. It is difficult to ensure good pressure change detection accuracy under high test pressure or diffusion pressure. At the same time, it is impossible to rule out the leakage error of small molecular gases such as hydrogen in the equipment.

Summary of the invention

In order to solve the above problems, the embodiment of the present application provides a salt rock core hydrogen diffusion coefficient test device and method, which overcomes the problems of low test accuracy of diffusion coefficient of highly penetrating small molecules and low-diffusivity rock salt. The technical solution is as follows:

A first aspect of the present application provides a salt rock core hydrogen diffusion coefficient testing device, comprising a test gas chamber, a gas source and a differential pressure sensor, wherein the test gas chamber comprises a reference chamber and a sample chamber, and the reference chamber and the sample chamber are connected through a pipeline; the gas source comprises a helium gas source and a hydrogen gas source to transport helium or hydrogen to the test gas chamber, wherein the helium gas source is used for container volume calibration, and the hydrogen gas source is used for hydrogen diffusion coefficient measurement; the high-pressure end of the differential pressure sensor is connected to the reference chamber, and the low-pressure end of the differential pressure sensor is connected to the sample chamber, so as to measure the pressure difference change between the reference chamber and the sample chamber during the test.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, a constant temperature box is also included, and the reference chamber and the sample chamber are located in the constant temperature box.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, the reference chamber and the sample chamber are respectively connected to a pressure gauge and a pressure sensor to monitor the pressure changes in the reference chamber and the sample chamber, and a temperature sensor is provided in the constant temperature box to monitor the temperature changes in the constant temperature box.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, it also includes a data collector, which is connected to the pressure sensor, the temperature sensor and the differential pressure sensor, and is used to collect and record data changes of the pressure sensor, the temperature sensor and the differential pressure sensor.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, one side of the reference chamber is connected to a venting pipeline, one side of the sample chamber is connected to a vacuum pump, and a vacuum pressure gauge is connected to the vacuum pump to monitor the vacuum pressure.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, the helium gas source and the hydrogen gas source are merged through a three-way valve and connected to a pressure regulating valve to adjust the pressure of the gas source, and then connected to the reference chamber.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, the helium gas source and the hydrogen gas source are contained in a hydraulic container, the bottom interface of the hydraulic container is connected to a hand pump, liquid is injected into the hydraulic container through the hand pump to pressurize the gas, and a three-way valve is provided at the bottom outlet of the hydraulic container.

A second aspect of the present application provides a method for testing the hydrogen diffusion coefficient of a salt rock core, comprising the following steps:

S1 core sample preparation and upper and lower end surface sealing and drying;

S2 connects the pipeline of the test device and sets the temperature of the thermostat for preheating;

S3: calculating the empty volume V _r of the reference chamber and the process pipeline connected thereto and the empty volume V _s of the sample chamber and the process pipeline connected thereto;

S4: measuring and calculating the core sample volume V _ss2 and the remaining volume V _sv of the sample chamber after the core sample is loaded;

S5 Core sample hydrogen diffusion coefficient D test: measure the pressure and pressure difference changes between the reference chamber and the sample chamber, calculate the core hydrogen diffusion amount _Mt at time t and the final diffusion amount _M∞ ; fit the columnar core diffusion analytical equation to calculate the core sample hydrogen diffusion coefficient D.

For example, in the salt rock core hydrogen diffusion coefficient test method provided in one embodiment, the calculation of the empty volume _Vr of the reference chamber and its connected process pipeline and the empty volume _Vs of the sample chamber and its connected process pipeline in S3 includes the following steps:

S3.1 Close the valve connecting the reference chamber to the vent line and the valve connecting to the gas source, evacuate the test device, and after evacuating, close the valve connecting the sample chamber to the vacuum pump, and record the initial pressure p _r1 of the reference chamber and the initial pressure p _s1 of the sample chamber;

S3.2 close the communication channel between the reference chamber and the sample chamber, inject helium into the reference chamber, record the pressure p _r2 of the reference chamber when the pressure is stable, stop injecting helium, connect the sample chamber and the reference chamber, wait for the reference chamber and the sample chamber to reach equilibrium, and record the pressures p _r3 and p _s3 of the reference chamber and the sample chamber respectively;

S3.3 Open the valve connecting the reference chamber to the vent line, release the helium in the test device, load the same number of standard cylindrical stainless steel samples with a known volume of _Vss1 into the sample chamber, close the valve connecting the reference chamber to the vent line, repeat S3.1, and record the initial pressure p _r4 of the reference chamber and the initial pressure p _s4 of the sample chamber in S3.1; repeat S3.2, record the pressure p _r5 of the reference chamber, and the pressures p _r6 and p _s6 of the reference chamber and the sample chamber after equilibrium;

S3.4 Calculate the empty volume V _r of the reference chamber and its connected process pipeline and the empty volume V _s of the sample chamber and its connected process pipeline according to the following formula:

Where Z(p,T) is the gas deviation factor under the conditions of pressure p and temperature T; R is the gas constant, 8.314 J/(mol·K); and T is the test environment temperature.

For example, in the method for testing the hydrogen diffusion coefficient of a salt rock core provided in one embodiment, the measuring and calculating of the core sample volume V _ss2 and the remaining volume B _sv of the sample chamber after the core sample is loaded in S4 includes the following steps:

S4.1 Open the valve connecting the reference chamber to the venting pipeline, release the helium in the test device, put the core sample into the sample chamber, repeat S3.1, and record the initial pressure p _r7 of the reference chamber and the initial pressure p _s7 of the sample chamber in S3.1;

S4.2 Repeat S3.2, record the pressure p _r8 of the reference chamber, the pressure p _r9 and p _s9 of the reference chamber after equilibrium with the sample chamber; calculate the core sample volume V _ss2 and the remaining volume V _sv of the sample chamber after the core sample is loaded according to the following formula:

_Vsv = _Vs - _Vss2 .

For example, in the method for testing hydrogen diffusion coefficient of salt rock core provided in one embodiment, the testing of hydrogen diffusion coefficient of core sample in S5 includes the following steps:

S5.1 Open the valve connecting the reference chamber to the vent line to release the helium in the test device, put a standard cylindrical stainless steel sample with a volume similar to that of the core sample into the reference chamber, record its volume as _Vss3 , close the valve connecting the reference chamber to the vent line and the valve connecting to the gas source, and evacuate the test device;

S5.2 Close the communication channel between the reference chamber and the sample chamber, inject hydrogen into the reference chamber until the gas pressure in the reference chamber is twice the target pressure, stop injecting hydrogen, wait until the temperature and pressure in the reference chamber are stable, and then record the pressure p _rd0 of the reference chamber;

S5.3 connect the sample chamber and the reference chamber, add hydrogen from the reference chamber to the sample chamber, close the communication channel between the reference chamber and the sample chamber when the pressure is balanced, and record the initial pressure p _rd1 of the reference chamber and the initial pressure p _sd1 of the sample chamber;

S5.4 The pressure change p _rd of the reference chamber and the pressure change p _sd of the sample chamber are monitored by the pressure sensor, and the pressure difference change p _dd between the sample chamber and the reference chamber is monitored by the pressure difference sensor. After equilibrium, the pressures of the reference chamber and the sample chamber are p _rde and p _sde respectively, and the pressure difference between the sample chamber and the reference chamber is p _dde . The pressure of the sample chamber is corrected according to the following formula:

_psd ＝ _prd - _pdd

_psde ＝ _prde − _pdde ;

S5.5 Calculate the core hydrogen diffusion amount _Mt and the final diffusion amount _M∞ at time t according to the following formula:

Where M is the molar mass of the gas;

S5.6 Fit the experimentally measured M _t /M _∞ with the columnar core diffusion analytical equation, and obtain the core sample hydrogen diffusion coefficient D according to the following formula:

Where t is the diffusion time and r is the radius of the core sample.

The beneficial effects of a salt rock core hydrogen diffusion coefficient testing device and method provided in some embodiments of the present application are as follows: the present application accurately calculates the diffusion coefficient of hydrogen in rock salt by monitoring the pressure change caused by the diffusion of gas into the core, and combines the design of pressure difference monitoring and equal volume diffusion to overcome the problems of low test accuracy of diffusion coefficient of highly penetrating small molecules and low diffusion rock salt. The present application has positive guiding significance for the determination of hydrogen diffusion coefficient in salt rock and the evaluation of sealing performance of salt cavern reservoirs.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic structural diagram of a salt rock core hydrogen diffusion coefficient testing device of the present application;

FIG2 is a flow chart of the method for testing the hydrogen diffusion coefficient of salt rock cores of the present application;

Figure 3 shows the test and fitting results of hydrogen diffusion coefficient of salt rock core.

DETAILED DESCRIPTION

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

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

In a first aspect, the present application provides a salt rock core hydrogen diffusion coefficient testing device, as shown in FIG1 , comprising a test gas chamber, a gas source and a differential pressure sensor 24, wherein the test gas chamber comprises a reference chamber 19 and a sample chamber 20, wherein the reference chamber 19 and the sample chamber 20 are connected via a pipeline; the gas source comprises a helium gas source 1 and a hydrogen gas source 2 to deliver helium or hydrogen to the test gas chamber, wherein the helium gas source 1 is used for container volume calibration, and the hydrogen gas source 2 is used for hydrogen diffusion coefficient measurement; the high-pressure end of the differential pressure sensor 24 is connected to the reference chamber 19, and the low-pressure end of the differential pressure sensor 24 is connected to the sample chamber 20 to measure the pressure difference change between the reference chamber 19 and the sample chamber 20 during the test.

This application uses a high-precision, small-range differential pressure sensor to effectively monitor the slight changes in pressure caused by gas diffusion during the experiment. Special sealing materials are used to reduce gas leakage, and reference chambers and sample chambers of the same structure and volume are used. During the experiment, a columnar stainless steel sample of the same volume as the core sample is installed in the reference chamber to reduce the impact of gas leakage on the experimental results, effectively solving the problem of accurate rock salt hydrogen diffusion coefficient, and has positive guiding significance for the determination of hydrogen diffusion coefficient in salt rock and the evaluation of the sealing of salt cavern reservoirs.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, as shown in Figure 1, it also includes a constant temperature box 5, the reference chamber 19 and the sample chamber 20 are located in the constant temperature box 5 to keep their temperature stable, and the constant temperature box 5 is equipped with a heating component and a compression refrigeration component, which can provide a controllable temperature of -5 to 100°C, and is also equipped with a circulation system for maintaining a uniform temperature in the constant temperature box 5; a temperature sensor 18 is provided in the constant temperature box 5 to monitor the temperature changes in the constant temperature box 18.

As shown in FIG1 , six-way valves are respectively provided on the reference chamber 19 and the sample chamber 20, and the six-way valve interfaces of the reference chamber 19 are respectively recorded as V1, V2, V3, V4, V5, and V6; the six-way valve interfaces on the sample chamber 20 are respectively recorded as V7, V8, V9, V10, V11, and V12, the six-way valve interface V4 of the reference chamber 19 is connected to the reference chamber 19, and the six-way valve interface V10 of the sample chamber 20 is connected to the sample chamber 20; the six-way valve interface V2 of the reference chamber 19 is connected to the six-way valve interface V12 of the sample chamber 20, so as to realize the communication between the reference chamber 19 and the sample chamber 20.

The helium gas source 1 and the hydrogen gas source 2 are combined through the first three-way valve 10 and connected to the pressure regulating valve 11 , and then connected to the six-way valve interface V5 of the reference chamber 19 to deliver hydrogen or helium to the reference chamber 19 and the sample chamber 20 .

The six-way valve interface V1 of the reference chamber 19 is connected to the first pressure gauge 12 and the first pressure sensor 13 to monitor the pressure changes of the reference chamber 19; the six-way valve interface V8 of the sample chamber 20 is connected to the second pressure gauge 15 and the second pressure sensor 14 to monitor the pressure changes of the sample chamber 20, wherein the pressure gauge can provide data calibration for the pressure sensor.

The high-pressure end of the differential pressure sensor 24 is connected to the six-way valve interface V6 of the reference chamber 19, and the low-pressure end of the differential pressure sensor 24 is connected to the six-way valve interface V7 of the sample chamber 20 to measure the pressure difference change between the reference chamber 19 and the sample chamber 20 during the test.

The six-way valve interface V3 of the reference chamber 19 is connected to a venting pipeline, and the six-way valve interface V11 of the sample chamber 20 is connected to a vacuum pump 22 , and a vacuum pressure gauge 23 is connected to the vacuum pump 22 to monitor the vacuum pressure.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, as shown in Figure 1, it also includes a data collector 25, which is connected to the first pressure sensor 13, the second pressure sensor 15, the temperature sensor 18 and the differential pressure sensor 24, and is used to collect and record the data changes of the first pressure sensor 13, the second pressure sensor 15, the temperature sensor 18 and the differential pressure sensor 24.

For example, in the salt rock core hydrogen diffusion coefficient testing device provided in one embodiment, as shown in Figure 1, the helium gas source 1 and the hydrogen gas source 2 are contained in a hydraulic container, the bottom interface of the hydraulic container is connected to a hand pump 4, and liquid is injected into the hydraulic container through the hand pump 4 to pressurize the gas, a second three-way valve 3 is provided at the bottom outlet of the hydraulic container, a third three-way valve 7 and a third pressure gauge 6 are provided at the outlet of the helium gas source 1, and a fourth three-way valve 9 and a fourth pressure gauge 8 are provided at the outlet of the hydrogen gas source 2.

Among them, there is a piston in the hydraulic container, the upper part of the piston is gas, and the lower part can be filled with liquid. The bottom interface of the hydraulic container is connected to the hand pump 4. When the pressure in the hydraulic container is insufficient, liquid can be injected into the hydraulic container through the hand pump 4 to push the piston to pressurize the gas in the hydraulic container.

The second aspect of the present application provides a method for testing the hydrogen diffusion coefficient of a salt rock core, as shown in FIG2 , comprising the following steps:

S1 core sample preparation, sealing and drying; specifically, the upper and lower end surfaces of the columnar rock salt standard sample are sealed with aluminum foil and epoxy resin, and then dried at low temperature;

S2 connects the pipeline of the test device and sets the temperature of the thermostat 5 for preheating; specifically, the test device is connected, according to the experimental temperature, the fluid medium is added to the thermostat 5, the thermostat 5 is started, the target temperature is set, and the temperature reaches the preset temperature;

S3: calculating the empty volume V _r of the reference chamber and the process pipeline connected thereto and the empty volume V _s of the sample chamber and the process pipeline connected thereto;

The specific steps include:

S3.1 Close the valve V3 of the reference chamber 19 connected to the vent line and the valve V5 connected to the gas source, close the six-way valve V9 of the sample chamber 20, open the other valves of the six-way valves of the reference chamber 19 and the sample chamber 20, and evacuate the test device for 10 minutes. After evacuation, close the valve V11 of the sample chamber 20 connected to the vacuum pump 22, and record the initial pressure p _r1 of the reference chamber 19 and the initial pressure p _s1 of the sample chamber 20;

S3.2 Close the communication channel between the reference chamber 19 and the sample chamber 20, that is, the six-way valve V2 of the reference chamber 19, inject helium into the reference chamber 19, and record the pressure p _r2 of the reference chamber 19 when the pressure is stable. The pressure does not exceed 1MPa. Close the six-way valve V5 of the reference chamber 19, stop injecting helium, open the six-way valve V2 of the reference chamber 19, connect the sample chamber 20 with the reference chamber 19, and wait until the reference chamber 19 and the sample chamber 20 reach equilibrium. Record the pressures p _r3 and p _s3 of the reference chamber 19 and the sample chamber 20 respectively. The pressures are all absolute pressures.

S3.3 Open the valve V3 connecting the reference chamber 19 to the venting line, release the helium in the entire test device, load the same number of standard cylindrical stainless steel samples with a known volume of _Vss1 into the sample chamber 20, close the valve V3 connecting the reference chamber 19 to the venting line, repeat S3.1, record the initial pressure p _r4 of the reference chamber 19 and the initial pressure p _s4 of the sample chamber 20 in S3.1; repeat S3.2, record the pressure p _r5 of the reference chamber 19, and the pressures p _r6 and p _s6 of the reference chamber 19 and the sample chamber 20 after equilibrium;

S3.4 Calculate the empty volume V _r of the reference chamber 19 and the process pipeline connected thereto and the empty volume V _s of the sample chamber 20 and the process pipeline connected thereto according to the following formula:

Where Z(p,T) is the gas deviation factor under the conditions of pressure p and temperature T; R is the gas constant, 8.314 J/(mol·K); and T is the test environment temperature.

S4: measuring and calculating the core sample volume V _ss2 and the remaining volume V _sv of the sample chamber after the core sample is loaded;

The specific steps include:

S4.1 Open the valve V3 connecting the reference chamber 19 to the venting pipeline to release the helium in the entire testing device, put the core sample 21 into the sample chamber 20, repeat S3.1, and record the initial pressure p _r7 of the reference chamber 19 and the initial pressure p _s7 of the sample chamber 20 in S3.1;

S4.2 Repeat S3.2, record the pressure p _r8 of the reference chamber 19, the pressure p _r9 and p _s9 of the reference chamber 19 and the sample chamber 20 after equilibrium; calculate the core sample volume V _ss2 and the remaining volume V _sv of the sample chamber 20 after the core sample 21 is loaded according to the following formula:

_Vsv = _Vs - _Vss2 .

S5 core sample hydrogen diffusion coefficient D test;

The specific steps include:

S5.1 Open the valve V3 of the reference chamber 19 connected to the venting pipeline to release the helium in the entire test device, put a standard cylindrical stainless steel sample with a volume similar to that of the core sample 21 into the reference chamber 19, record its volume as _Vss3 , close the six-way valves V3 and V5 of the reference chamber 19 and the six-way valve V9 of the sample chamber 20, open the other valves of the six-way valve of the reference chamber 19 and the six-way valve of the sample chamber 20, and evacuate the entire test device for 2 hours;

S5.2 After evacuation, close the six-way valve V11 of the sample chamber 20, open the six-way valve V5 of the reference chamber 19, inject hydrogen into the reference chamber 19, adjust the pressure regulating valve 11 so that the gas pressure in the reference chamber 19 reaches 2 times the target pressure, close the six-way valve V5 of the reference chamber 19, stop injecting hydrogen, and wait until the temperature and pressure in the reference chamber 19 are stable, then record the pressure p _rd0 of the reference chamber 19;

S5.3 Open the six-way valve V2 of the reference chamber 19 to connect the sample chamber 20 with the reference chamber 19, add hydrogen from the reference chamber 19 to the sample chamber 20, close the six-way valve V2 of the reference chamber 19 when the pressure is balanced, and record the initial pressure p _rd1 of the reference chamber 19 and the initial pressure p _sd1 of the sample chamber 20;

S5.4 The pressure change p _rd of the reference chamber 19 is monitored by the first pressure sensor 13, the pressure change p _sd of the sample chamber 20 is monitored by the second pressure sensor 15, and the pressure difference change p _dd between the sample chamber 20 and the reference chamber 19 is monitored by the pressure difference sensor 24. After equilibrium, the pressures of the reference chamber 19 and the sample chamber 20 are p _rde and p _sde respectively, and the pressure difference between the sample chamber 20 and the reference chamber 19 is p _dde . The pressure of the sample chamber 20 is corrected according to the following formula:

_psd ＝ _prd - _pdd

_psde ＝ _prde − _pdde ;

S5.5 Calculate the core hydrogen diffusion amount _Mt and the final diffusion amount _M∞ at time t according to the following formula:

Where M is the molar mass of the gas.

S5.6 Fit the experimentally measured M _t /M _∞ with the columnar core diffusion analytical equation, and obtain the core sample hydrogen diffusion coefficient D according to the following formula:

Where t is the diffusion time and r is the radius of the core sample.

The experimental results of hydrogen diffusion of a standard salt rock core containing impurities (diameter 24.62 mm, height 49.45 mm) at a diffusion pressure of 2.796 MPa and a temperature of 25°C are shown in FIG3 . The diffusion coefficient D obtained by fitting calculation is 3.9×10 ^-10 m ² /s.

The salt rock core hydrogen diffusion coefficient test method of the present application accurately calculates the diffusion coefficient of hydrogen in rock salt by monitoring the pressure change caused by the diffusion of gas into the core, and combines the design of pressure difference monitoring and equal volume diffusion to overcome the problems of low test accuracy of diffusion coefficient of highly penetrating small molecules and low diffusion rock salt. The present application has positive guiding significance for the determination of hydrogen diffusion coefficient in salt rock and the evaluation of sealing performance of salt cavern reservoirs.

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

Claims (8)

1. A method for testing hydrogen diffusion coefficient of a salt rock core, characterized in that the method is used for a salt rock core hydrogen diffusion coefficient testing device, and the salt rock core hydrogen diffusion coefficient testing device comprises: The test gas chamber comprises a reference chamber and a sample chamber, wherein the reference chamber and the sample chamber are connected via a pipeline, and the reference chamber and the sample chamber are located in a constant temperature box; A gas source, including a helium gas source and a hydrogen gas source, to deliver helium or hydrogen to the test gas chamber, wherein the helium gas source is used for container volume calibration, and the hydrogen gas source is used for hydrogen diffusion coefficient measurement; A differential pressure sensor, wherein the high pressure end of the differential pressure sensor is connected to the reference chamber, and the low pressure end of the differential pressure sensor is connected to the sample chamber, so as to measure the pressure difference change between the reference chamber and the sample chamber during the test: The test method comprises the following steps: S1 core sample preparation and upper and lower end surface sealing and drying; S2 connects the pipeline of the test device and sets the temperature of the thermostat for preheating; S3: calculating the empty volume V _r of the reference chamber and the process pipeline connected thereto and the empty volume V _s of the sample chamber and the process pipeline connected thereto; S4: measuring and calculating the core sample volume V _ss2 and the remaining volume V _sv of the sample chamber after the core sample is loaded; S5 Core sample hydrogen diffusion coefficient D test: measure the pressure and pressure difference changes between the reference chamber and the sample chamber, calculate the core hydrogen diffusion amount _Mt at time t and the final diffusion amount _M∞ ; fit the columnar core diffusion analytical equation to calculate the core sample hydrogen diffusion coefficient D; The hydrogen diffusion coefficient D of the core sample is obtained according to the following formula: Where t is the diffusion time and r is the radius of the core sample. 2. The method for testing the hydrogen diffusion coefficient of salt rock core according to claim 1 is characterized in that the reference chamber and the sample chamber are respectively connected to a pressure gauge and a pressure sensor to monitor the pressure changes of the reference chamber and the sample chamber, and a temperature sensor is provided in the constant temperature box to monitor the temperature changes in the constant temperature box. 3. According to the method for testing the hydrogen diffusion coefficient of salt rock cores in claim 2, it is characterized in that it also includes a data collector, which is connected to the pressure sensor, the temperature sensor and the differential pressure sensor, and is used to collect and record data changes of the pressure sensor, the temperature sensor and the differential pressure sensor. 4. The method for testing the hydrogen diffusion coefficient of salt rock core according to claim 3 is characterized in that one side of the reference chamber is connected to a venting pipeline, one side of the sample chamber is connected to a vacuum pump, and a vacuum pressure gauge is connected to the vacuum pump to monitor the vacuum pressure. 5. According to the method for testing the hydrogen diffusion coefficient of salt rock cores in claim 4, it is characterized in that the helium gas source and the hydrogen gas source are merged through a three-way valve and then connected to a pressure regulating valve to adjust the pressure of the gas source, and then connected to the reference chamber, the helium gas source and the hydrogen gas source are placed in a hydraulic container, the bottom interface of the hydraulic container is connected to a hand pump, liquid is injected into the hydraulic container through the hand pump to pressurize the gas, and a three-way valve is provided at the bottom outlet of the hydraulic container. 6. The method for testing the hydrogen diffusion coefficient of a salt rock core according to claim 5, characterized in that the step of calculating the empty volume _Vr of the reference chamber and the process pipeline connected thereto and the empty volume _Vs of the sample chamber and the process pipeline connected thereto in S3 comprises the following steps: S3.1 Close the valve connecting the reference chamber to the vent line and the valve connecting to the gas source, evacuate the test device, and after evacuating, close the valve connecting the sample chamber to the vacuum pump, and record the initial pressure p _r1 of the reference chamber and the initial pressure p _s1 of the sample chamber; S3.2 close the communication channel between the reference chamber and the sample chamber, inject helium into the reference chamber, record the pressure p _r2 of the reference chamber when the pressure is stable, stop injecting helium, connect the sample chamber and the reference chamber, wait for the reference chamber and the sample chamber to reach equilibrium, and record the pressures p _r3 and p _s3 of the reference chamber and the sample chamber respectively; S3.3 Open the valve connecting the reference chamber to the vent line, release the helium in the test device, load the same number of standard cylindrical stainless steel samples with a known volume of _Vss1 into the sample chamber, close the valve connecting the reference chamber to the vent line, repeat S3.1, and record the initial pressure p _r4 of the reference chamber and the initial pressure p _s4 of the sample chamber in S3.1; repeat S3.2, record the pressure p _r5 of the reference chamber, and the pressures p _r6 and p _s6 of the reference chamber and the sample chamber after equilibrium; S3.4 Calculate the empty volume V _r of the reference chamber and its connected process pipeline and the empty volume V _s of the sample chamber and its connected process pipeline according to the following formula: Where Z(p, T) is the gas deviation factor under the conditions of pressure p and temperature T; R is the gas constant, 8.314 J/(mol·K); and T is the test environment temperature. 7. The method for testing hydrogen diffusion coefficient of salt rock core according to claim 6, characterized in that the measuring and calculating of the core sample volume V _ss2 and the remaining volume V _sv of the sample chamber after the core sample is loaded in S4 comprises the following steps: S4.1 Open the valve connecting the reference chamber to the venting pipeline, release the helium in the test device, put the core sample into the sample chamber, repeat S3.1, and record the initial pressure p _r7 of the reference chamber and the initial pressure p _s7 of the sample chamber in S3.1; S4.2 Repeat S3.2, record the pressure p _r8 of the reference chamber, the pressure p _r9 and p _s9 of the reference chamber after equilibrium with the sample chamber; calculate the core sample volume V _ss2 and the remaining volume V _sv of the sample chamber after the core sample is loaded according to the following formula: _Vsv = _Vs - _Vss2 . 8. The method for testing hydrogen diffusion coefficient of salt rock core according to claim 7, characterized in that the test of hydrogen diffusion coefficient of the core sample in S5 comprises the following steps: S5.1 Open the valve connecting the reference chamber to the vent line to release the helium in the test device, put a standard cylindrical stainless steel sample with a volume similar to that of the core sample into the reference chamber, record its volume as _Vss3 , close the valve connecting the reference chamber to the vent line and the valve connecting to the gas source, and evacuate the test device; S5.2 Close the communication channel between the reference chamber and the sample chamber, inject hydrogen into the reference chamber until the gas pressure in the reference chamber is twice the target pressure, stop injecting hydrogen, wait until the temperature and pressure in the reference chamber are stable, and then record the pressure p _rd0 of the reference chamber; S5.3 connect the sample chamber and the reference chamber, add hydrogen from the reference chamber to the sample chamber, close the communication channel between the reference chamber and the sample chamber when the pressure is balanced, and record the initial pressure p _rd1 of the reference chamber and the initial pressure p _sd1 of the sample chamber; S5.4 The pressure change p _rd of the reference chamber and the pressure change p _sd of the sample chamber are monitored by the pressure sensor, and the pressure difference change p _dd between the sample chamber and the reference chamber is monitored by the pressure difference sensor. After equilibrium, the pressures of the reference chamber and the sample chamber are p _rde and p _sde respectively, and the pressure difference between the sample chamber and the reference chamber is p _dde . The pressure of the sample chamber is corrected according to the following formula: _psd ＝ _prd - _{pdd psde} ＝ _prde − _pdde ; S5.5 Calculate the core hydrogen diffusion amount _Mt and the final diffusion amount _M∞ at time t according to the following formula: Where M is the molar mass of the gas; S5.6 Fit the experimentally measured M _t /M _∞ with the columnar core diffusion analytical equation, and obtain the core sample hydrogen diffusion coefficient D according to the following formula: Where t is the diffusion time and r is the radius of the core sample.