Method and system for predicting wellhead pressure of salt cavern hydrogen / helium storage reservoir

Abstract

The invention discloses a salt cavern hydrogen / helium reservoir wellhead pressure prediction method and system. The method comprises the following steps: S1, acquiring basic data of a salt cavern hydrogen / helium reservoir; s2, monitoring and recording historical gas injection and production data of the salt cavern hydrogen / helium storage reservoir and the current state of the hydrogen / helium storage reservoir; s3, performing prediction and quantitative simulation on the leakage amount of hydrogen / helium in the reservoir during operation, the amount of hydrogen / helium dissolved and lost hydrogen / helium, the contraction amount of the cavity of the hydrogen / helium storage reservoir and the distribution of a hydrogen / helium temperature field by using the basic data and the state monitoring data of the salt cavern hydrogen / helium storage reservoir; s4, the wellhead pressure is calculated according to the parameters obtained in the S3, and the change trend of the wellhead pressure is predicted; according to the method, the change trend of the wellhead pressure is accurately predicted by accurately predicting the contribution degrees of the four factors of hydrogen / helium leakage, hydrogen / helium dissolution, gas heat effect and cavity shrinkage to the wellhead pressure change, and the important requirement for predicting the change trend of the wellhead pressure during the operation period of the salt cavern hydrogen / helium storage reservoir is met.

Description

Technical Field

[0001] The present application relates to the technical field of underground storage of rare gases such as hydrogen and helium, and in particular to a method and system for predicting the wellhead pressure of a salt cavern hydrogen and helium storage reservoir. Background Art

[0002] Hydrogen / helium, as a strategic scarce substance, is widely used as a pressurizing agent and booster for rocket liquid fuel, a coolant for the nuclear industry, and a leak detector for pipelines and electronic and electrical devices. Salt rock formations are excellent geological bodies for deep energy storage, with low permeability (less than 10-20m 2 ) and small porosity (less than 1%), existing research has demonstrated the technical feasibility of hydrogen / helium storage in salt rock formations.

[0003] For salt caverns buried thousands of meters underground, wellhead pressure is an important parameter reflecting the operating status of salt cavern hydrogen / helium storage, and is a key parameter of great concern to the construction party and the owner. Although the wellhead pressure can be monitored in real time by a pressure gauge, accurately predicting the changing trend of the wellhead pressure is of great significance for the design of injection / gas production process flow and equipment selection. Through literature research, the currently disclosed technologies mainly focus on the construction method, sealing and injection and production parameter optimization of salt cavern gas storage, and there is no technology related to salt cavern helium storage and wellhead pressure prediction. Therefore, a method for predicting the wellhead pressure of salt cavern hydrogen / helium storage is urgently needed. Summary of the invention

[0004] In order to solve the above problems, the present application provides a salt cavern hydrogen / helium storage wellhead pressure prediction method and system, which meets the significant demand for prediction of wellhead pressure change trend during the operation of the salt cavern hydrogen / helium storage. The technical solution is as follows:

[0005] The present application provides a method for predicting the wellhead pressure of a salt cavern hydrogen / helium storage, comprising the following steps:

[0006] S1 obtains basic data of salt cavern hydrogen / helium storage;

[0007] S2 monitors and records the historical gas injection and production data of the salt cavern hydrogen / helium storage and the current status of the hydrogen / helium storage;

[0008] S3 uses the basic data and status monitoring data of salt cavern hydrogen / helium storage to predict and quantitatively simulate the amount of hydrogen / helium leakage in the storage during operation, the amount of hydrogen / helium lost due to hydrogen / helium dissolution, the shrinkage of the hydrogen / helium storage cavity, and the distribution of hydrogen / helium temperature field;

[0009] S4 calculates the wellhead pressure according to the parameters obtained in S3 and predicts the changing trend of the wellhead pressure.

[0010] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, in S4, the wellhead pressure is calculated according to the following formula:

[0011]

[0012] In formula (1), p wh is the wellhead pressure; n 0 V is the gas volume in the salt cavern hydrogen / helium storage chamber at the initial moment; 0 is the cavity volume of the salt cavern hydrogen / helium storage; n l is the hydrogen / helium leakage; n s V is the amount of hydrogen / helium lost due to hydrogen / helium dissolution; s is the volume loss of the hydrogen / helium storage cavity caused by cavity contraction; Z is the gas compression factor; T is the hydrogen / helium temperature field distribution.

[0013] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, the hydrogen / helium gas leakage amount n l The calculation method is as follows: the high-pressure hydrogen / helium stored in the salt caverns leaks into the pores of the surrounding rock, and the amount of gas leakage into the surrounding rock is expressed by the following seepage equation:

[0014]

[0015] In formula (2), ρ represents the density of hydrogen / helium, kg / m 3 ; φ represents the porosity of salt rock; t represents the simulation time, s; k represents the combined permeability of hydrogen / helium, m 2 ; μ is the viscosity of hydrogen / helium, Pa·s; p is the gas pressure, Pa;

[0016] The pressure field distribution in the surrounding rock pores can be obtained by equation (2), and then the seepage velocity of hydrogen / helium along the cavity wall into the surrounding rock can be obtained. According to the principle of mass conservation, the hydrogen / helium leakage amount n can be obtained by the following equation: l :

[0017]

[0018] In formula (3), M is the molar mass of hydrogen / helium.

[0019] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, the hydrogen / helium amount lost by dissolution n s The calculation method is: According to the diffusion law, the diffusion and dissolution of hydrogen / helium in brine satisfies the following formula:

[0020]

[0021] In formula (4), c is the concentration of hydrogen / helium in brine; D is the diffusion coefficient of hydrogen / helium in brine;

[0022] Based on formula (4), the concentration distribution of hydrogen / helium in brine at different times can be simulated, and the amount of hydrogen / helium lost by hydrogen / helium dissolution can be calculated by volume integration of the following formula: r :

[0023]

[0024] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, the volume loss V of the hydrogen / helium storage cavity caused by the cavity contraction is s Satisfy the following calculation formula:

[0025]

[0026] In formula (6), V is the volume of the salt cavern cavity; x is the creep rate attenuation index, which can be obtained through the core creep test of the target layer of the hydrogen / helium storage reservoir; a is the empirical coefficient, which can be obtained by inverting the measured cavity volume shrinkage data.

[0027] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, the calculation method of the hydrogen / helium temperature field distribution T is:

[0028]

[0029] In formula (7), A is the cross-sectional area of ​​the wellbore or salt cavern; ρ is the density of hydrogen / helium; C v,g is the specific heat capacity of hydrogen / helium; T f is the temperature of hydrogen / helium; t is the time; μ jT is the Joule-Thomson coefficient of hydrogen / helium; p is the pressure of hydrogen / helium; Q e is the convective heat transfer rate between hydrogen / helium and surrounding rock, Q e The calculation method is:

[0030] Q e =2πr 0 U we (T e -T f ) Formula (8);

[0031] In formula (8), r 0 is the radius of the wellbore or salt cavern; U we is the comprehensive heat transfer coefficient between the gas and the surrounding environment; T e is the formation temperature, T e The calculation method is:

[0032]

[0033] In formula (9), r is the distance from the center of the gas storage; ρ e is the density of the formation rock; C e is the specific heat capacity of the formation rock; k e is the thermal conductivity of the formation rock;

[0034] By combining equations (7) to (9), the change of hydrogen / helium temperature in the chamber with time during the gas injection and reservoir construction period can be calculated.

[0035] The second aspect of the present application provides a salt cavern hydrogen / helium storage wellhead pressure prediction system, comprising:

[0036] Basic data collection unit, used to collect basic data of salt cavern hydrogen / helium storage;

[0037] A state monitoring unit, including a state monitor, for recording historical gas injection and production data of the salt cavern hydrogen / helium storage and the current state of the hydrogen / helium storage;

[0038] The leakage rate quantitative evaluation unit uses the basic data and status monitoring data of the salt cavern hydrogen / helium storage to quantitatively simulate the hydrogen / helium leakage, hydrogen / helium dissolution, gas thermal effect and hydrogen / helium storage cavity shrinkage in the storage;

[0039] The wellhead pressure prediction unit predicts the change trend of the wellhead pressure according to the influence of the four effects on the wellhead pressure change obtained by the leakage rate quantitative evaluation unit.

[0040] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction system provided in one embodiment, basic data for quantitative evaluation of salt cavern hydrogen / helium storage leakage rate are input into the basic data collection unit, including sonar cavity measurement data of the salt cavern cavity, wellbore trajectory, wellbore structure and gas injection string size.

[0041] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction system provided in one embodiment, the status monitoring unit also includes a gas flow meter, a manifold valve and a wellhead temperature and pressure gauge arranged on the surface injection and production manifold, which are used to record the historical injection and production gas data of the salt cavern hydrogen / helium storage, and then obtain the inventory gas volume in the salt cavern hydrogen / helium storage cavity and the current hydrogen / helium storage state, including the switch state of the manifold valve, wellhead pressure and temperature parameters.

[0042] A salt cavern hydrogen / helium storage wellhead pressure prediction method and system provided in some embodiments of the present application have the following beneficial effects: the present application accurately predicts the contribution of four factors, namely, hydrogen / helium leakage, hydrogen / helium dissolution, gas thermal effect and cavity shrinkage, to the change in wellhead pressure, and thus accurately predicts the change trend of wellhead pressure. Compared with traditional technical means, the salt cavern hydrogen / helium storage wellhead pressure prediction method of the present application is supported by a perfect theoretical model and complements the real-time data of field monitoring. The calculation is simple, scientific and reasonable, and can provide technical support for the optimal design of surface injection and production technology of salt cavern hydrogen / helium storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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.

[0044] Figure 1 This is a schematic diagram of the structure of the salt cavern hydrogen / helium storage wellhead pressure prediction system of the present application;

[0045] Figure 2 This is a flow chart of the method for predicting wellhead pressure of a salt cavern hydrogen / helium storage reservoir of the present application. DETAILED DESCRIPTION

[0046] 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.

[0047] 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.

[0048] like Figure 1 As shown, hydrogen / helium is injected from the surface injection and production manifold 1, flows through the wellbore 5 to the underground salt cavern 7 for long-term storage; during the operation of the salt cavern hydrogen / helium storage, the change in wellhead pressure is mainly affected by four factors: hydrogen / helium leakage, hydrogen / helium dissolution, gas thermal effect and cavity contraction. Specifically, ① hydrogen / helium leakage: the salt cavern surrounding rock includes two types: salt rock 9 and interlayer 10. In particular, the porosity and permeability of the interlayer 10 are larger. Therefore, the high-pressure hydrogen / helium stored in the salt cavern will leak into the pores of the surrounding rock, affecting the total amount of hydrogen / helium in the reservoir; ② hydrogen / helium dissolution: hydrogen / helium will dissolve in the bottom brine 8. Although only 1 liter of water can produce 1 liter of hydrogen / helium under standard conditions, the hydrogen / helium will not dissolve in the bottom brine 8. 8.61 ml of hydrogen / helium are dissolved, but the solubility of hydrogen / helium increases significantly with the increase of temperature and pressure. The dissolution of hydrogen / helium will also affect the total amount of hydrogen / helium in the reservoir; ③ Gas thermal effect: The temperature of the surrounding rock is higher than the temperature of the injected hydrogen / helium, so heat exchange will occur between hydrogen / helium and the surrounding rock, which will change the temperature of hydrogen / helium. The temperature change of hydrogen / helium in the relatively closed space of the hydrogen / helium storage will also be reflected in the wellhead pressure; ④ Cavity contraction: Since the reservoir gas pressure is less than the in-situ stress of the surrounding rock, and salt rock is a rock with good rheology, the cavity will continue to shrink under this deviatoric stress, so the helium storage space will continue to decrease.

[0049] Theoretical analysis shows that the change of wellhead pressure during the operation of salt cavern hydrogen / helium storage is mainly affected by four factors: hydrogen / helium leakage, hydrogen / helium dissolution, gas thermal effect and cavity shrinkage. In view of this, the present application provides a salt cavern hydrogen / helium storage wellhead pressure prediction method. By accurately predicting the contribution of the above four factors to the change of wellhead pressure, the change trend of wellhead pressure can be accurately predicted. Figure 2 As shown, the following steps are included:

[0050] S1 obtains basic data of salt cavern hydrogen / helium storage;

[0051] Specifically, it includes collecting basic data on salt cavern hydrogen / helium storage, such as sonar cavity morphology, wellbore structure, wellbore trajectory, and injection and production string dimensions;

[0052] S2 monitors and records the historical gas injection and production data of the salt cavern hydrogen / helium storage and the current status of the hydrogen / helium storage;

[0053] Specifically, a status monitor is used to record the historical gas injection and production data of the salt cavern hydrogen / helium storage and the current status of the hydrogen / helium storage, including valve switch status, wellhead pressure, temperature and other parameters;

[0054] S3 uses the basic data and status monitoring data of salt cavern hydrogen / helium storage to predict and quantitatively simulate the amount of hydrogen / helium leakage in the storage during operation, the amount of hydrogen / helium lost due to hydrogen / helium dissolution, the shrinkage of the hydrogen / helium storage cavity, and the distribution of hydrogen / helium temperature field;

[0055] S4 calculates the wellhead pressure according to the parameters obtained in S3 and predicts the changing trend of the wellhead pressure.

[0056] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, in S4, the wellhead pressure is calculated according to the following formula:

[0057]

[0058] In formula (1), p wh is the wellhead pressure; n 0 V is the gas volume in the salt cavern hydrogen / helium storage chamber at the initial moment; 0 is the cavity volume of the salt cavern hydrogen / helium storage, which can be calculated using the sonar cavity measurement data in the basic data; n l is the hydrogen / helium leakage; n s V is the amount of hydrogen / helium lost due to hydrogen / helium dissolution; s is the volume loss of the hydrogen / helium storage cavity caused by cavity contraction; Z is the gas compression factor, which can be obtained through the PR gas state equation; T is the hydrogen / helium temperature field distribution.

[0059] Salt cavern surrounding rocks include salt rock and interlayers. In particular, interlayers have greater porosity and permeability. Therefore, the high-pressure hydrogen / helium stored in the salt cavern will leak into the pores of the surrounding rocks. For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in an embodiment, the hydrogen / helium leakage amount n l The calculation method is as follows: the high-pressure hydrogen / helium stored in the salt caverns leaks into the pores of the surrounding rock, and the amount of gas leakage into the surrounding rock is expressed by the following seepage equation:

[0060]

[0061] In formula (2), ρ represents the density of hydrogen / helium, kg / m 3 ; φ represents the porosity of salt rock; t represents the simulation time, s; k represents the combined permeability of hydrogen / helium, m 2 ; μ is the viscosity of hydrogen / helium, Pa·s; p is the gas pressure, Pa;

[0062] The pressure field distribution in the surrounding rock pores can be obtained by equation (2), and then the seepage velocity of hydrogen / helium along the cavity wall into the surrounding rock can be obtained. According to the principle of mass conservation, the hydrogen / helium leakage amount n can be obtained by the following equation: l :

[0063]

[0064] In formula (3), M is the molar mass of hydrogen / helium.

[0065] The dissolution of hydrogen / helium in brine is a diffusion dissolution process, and the hydrogen / helium concentration at the gas-brine interface 6 tends to be saturated. For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in an embodiment, the amount of hydrogen / helium lost by the dissolution of hydrogen / helium n s The calculation method is: According to the diffusion law, the diffusion and dissolution of hydrogen / helium in brine satisfies the following formula:

[0066]

[0067] In formula (4), c is the concentration of hydrogen / helium in brine; D is the diffusion coefficient of hydrogen / helium in brine;

[0068] Based on formula (4), the concentration distribution of hydrogen / helium in brine at different times can be simulated, and the amount of hydrogen / helium lost by hydrogen / helium dissolution can be calculated by volume integration of the following formula: r :

[0069]

[0070] Since the operating pressure of the salt cavern hydrogen / helium storage is less than the in-situ geostress of the formation, the surrounding rock of the hydrogen / helium storage will inevitably shrink, resulting in a reduction in the cavity volume. The reduction in cavity volume will squeeze the hydrogen / helium gas and cause an increase in wellhead pressure. Although there are individual differences between salt caverns, the volume shrinkage rate of salt cavern storage in the same area is basically the same. Therefore, the historical volume shrinkage data of other salt cavern gas storages that have been put into production can be used to predict the volume shrinkage rate of the hydrogen / helium storage. For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, the hydrogen / helium storage cavity volume loss V caused by the cavity shrinkage is s Satisfy the following calculation formula:

[0071]

[0072] In formula (6), V is the volume of the salt cavern; x is the creep rate attenuation index, which can be obtained through the core creep test of the target layer of the hydrogen / helium storage reservoir; a is the empirical coefficient, which can be obtained by inverting the measured cavity volume shrinkage data. After determining the creep rate attenuation index x and the empirical coefficient a, the volume shrinkage V of the cavity at any time can be predicted. s .

[0073] In the closed storage space, the heat transfer mode between hydrogen / helium and the salt cavern surrounding rock and the wellbore is heat conduction. For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction method provided in one embodiment, the calculation method of the hydrogen / helium temperature field distribution T is:

[0074]

[0075] In formula (7), A is the cross-sectional area of ​​the wellbore or salt cavern; ρ is the density of hydrogen / helium; C v,g is the specific heat capacity of hydrogen / helium; T f is the temperature of hydrogen / helium; t is the time; μ jT is the Joule-Thomson coefficient of hydrogen / helium; p is the pressure of hydrogen / helium; Q e is the convective heat transfer rate between hydrogen / helium and surrounding rock, which is the fundamental reason for the increase in hydrogen / helium temperature. e The calculation method is:

[0076] Q e =2πr 0 U we (T e -T f ) Formula (8);

[0077] In formula (8), r 0 is the radius of the wellbore or salt cavern; U we is the comprehensive heat transfer coefficient between the gas and the surrounding environment; T e is the formation temperature, T e The calculation method is:

[0078]

[0079] In formula (9), r is the distance from the center of the gas storage; ρ e is the density of the formation rock; C e is the specific heat capacity of the formation rock; k e is the thermal conductivity of the formation rock;

[0080] By combining equations (7) to (9), the change of hydrogen / helium temperature in the chamber with time during the gas injection and reservoir construction period can be calculated.

[0081] In summary, the hydrogen / helium leakage n l 、The amount of hydrogen / helium lost by hydrogen / helium dissolution n s , the volume loss of hydrogen / helium storage cavity caused by cavity shrinkage V s By substituting the prediction results of the four parameters of the temperature field distribution T of hydrogen / helium into equation (1), the wellhead pressure can be predicted.

[0082] The salt cavern hydrogen / helium storage wellhead pressure prediction method of the present application utilizes the basic data and status monitoring data of the salt cavern hydrogen / helium storage to numerically simulate the hydrogen / helium leakage, hydrogen / helium dissolution, gas thermal effect and cavity shrinkage in the storage, and quantitatively characterizes the influence of the above four effects on the wellhead pressure change, thereby accurately predicting the change trend of the wellhead pressure.

[0083] The second aspect of the present application provides a salt cavern hydrogen / helium storage wellhead pressure prediction system, such as Figure 1 As shown, including:

[0084] Basic data collection unit, used to collect basic data of salt cavern hydrogen / helium storage;

[0085] A state monitoring unit, including a state monitor 11, for recording historical gas injection and production data of the salt cavern hydrogen / helium storage reservoir and the current state of the hydrogen / helium storage reservoir;

[0086] The leakage rate quantitative evaluation unit uses the basic data and status monitoring data of the salt cavern hydrogen / helium storage to quantitatively simulate the hydrogen / helium leakage, hydrogen / helium dissolution, gas thermal effect and hydrogen / helium storage cavity shrinkage in the storage;

[0087] The wellhead pressure prediction unit 12 predicts the change trend of the wellhead pressure according to the influence of the four effects on the wellhead pressure change obtained by the leakage rate quantitative evaluation unit.

[0088] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction system provided in one embodiment, basic data for quantitative evaluation of salt cavern hydrogen / helium storage leakage rate are input into the basic data collection unit, including sonar cavity measurement data of the salt cavern cavity, wellbore trajectory, wellbore structure and gas injection string size.

[0089] For example, in the salt cavern hydrogen / helium storage wellhead pressure prediction system provided in one embodiment, Figure 1 As shown, the status monitoring unit also includes a gas flow meter 2, a manifold valve 3 and a wellhead temperature and pressure gauge 4 arranged on the surface injection and production manifold 1, which are used to record the historical injection and production gas data of the salt cavern hydrogen / helium storage, and then obtain the inventory gas volume in the salt cavern hydrogen / helium storage cavity and the current hydrogen / helium storage state, including the switch state of the manifold valve 3, wellhead pressure and temperature parameters.

[0090] The salt cavern hydrogen / helium storage wellhead pressure prediction system of the present application records the historical gas injection and production data of the salt cavern hydrogen / helium storage and the current status of the hydrogen / helium storage through the status monitor 11, and quantitatively simulates the above four effects through the wellhead pressure prediction unit 12, and finally obtains the changing trend of the wellhead pressure.

[0091] Compared with traditional technical means, the present application provides a salt cavern hydrogen / helium storage wellhead pressure prediction method and system. This method is supported by a complete theoretical model and complements the real-time data of on-site monitoring. The calculation is simple, scientific and reasonable, and can provide technical support for the optimized design of the surface injection and production process of salt cavern hydrogen / helium storage.

[0092] 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

1. A method for predicting the wellhead pressure of a salt cavern hydrogen / helium storage, characterized in that: The following steps are involved: S1 obtains basic data of salt cavern hydrogen / helium storage; S2 monitors and records the historical gas injection and production data of the salt cavern hydrogen / helium storage and the current status of the hydrogen / helium storage; S3 uses the basic data and status monitoring data of salt cavern hydrogen / helium storage to predict and quantitatively simulate the amount of hydrogen / helium leakage in the storage during operation, the amount of hydrogen / helium lost due to hydrogen / helium dissolution, the shrinkage of the hydrogen / helium storage cavity, and the distribution of hydrogen / helium temperature field; S4 calculates the wellhead pressure according to the parameters obtained in S3 and predicts the changing trend of the wellhead pressure.

2. The method for predicting wellhead pressure of a salt cavern hydrogen / helium storage according to claim 1, characterized in that: In S4, the wellhead pressure is calculated according to the following formula: In formula (1), p wh is the wellhead pressure; n0 is the amount of gas stored in the salt cavern hydrogen / helium storage chamber at the initial moment; V0 is the chamber volume of the salt cavern hydrogen / helium storage chamber; n l is the hydrogen / helium leakage; n s V is the amount of hydrogen / helium lost due to hydrogen / helium dissolution; s is the volume loss of the hydrogen / helium storage cavity caused by cavity contraction; Z is the gas compression factor; T is the temperature field distribution of hydrogen / helium.

3. The method for predicting wellhead pressure of a salt cavern hydrogen / helium storage according to claim 2, characterized in that: The hydrogen / helium leakage n l The calculation method is as follows: the high-pressure hydrogen / helium stored in the salt caverns leaks into the pores of the surrounding rock, and the amount of gas leakage into the surrounding rock is expressed by the following seepage equation: In formula (2), ρ represents the density of hydrogen / helium, kg / m 3 ; φ represents the porosity of salt rock; t represents the simulation time, s; k represents the combined permeability of hydrogen / helium, m 2 ; μ is the viscosity of hydrogen / helium, Pa·s; p is the gas pressure, Pa; The pressure field distribution in the surrounding rock pores can be obtained by equation (2), and then the seepage velocity of hydrogen / helium along the cavity wall into the surrounding rock can be obtained. According to the principle of mass conservation, the hydrogen / helium leakage amount n can be obtained by the following equation: l : In formula (3), M is the molar mass of hydrogen / helium.

4. The method for predicting wellhead pressure of a salt cavern hydrogen / helium storage according to claim 2, characterized in that: The amount of hydrogen / helium lost by dissolution of hydrogen / helium n s The calculation method is: According to the diffusion law, the diffusion and dissolution of hydrogen / helium in brine satisfies the following formula: In formula (4), c is the concentration of hydrogen / helium in brine; D is the diffusion coefficient of hydrogen / helium in brine; Based on formula (4), the concentration distribution of hydrogen / helium in brine at different times can be simulated, and the amount of hydrogen / helium lost by hydrogen / helium dissolution can be calculated by volume integration of the following formula: r :

5. The method for predicting wellhead pressure of a salt cavern hydrogen / helium storage according to claim 2, characterized in that: The volume loss V of the hydrogen / helium storage cavity caused by the cavity shrinkage s Satisfy the following calculation formula: In formula (6), V is the volume of the salt cavern cavity; x is the creep rate attenuation index, which can be obtained through the core creep test of the target layer of the hydrogen / helium storage reservoir; a is the empirical coefficient, which can be obtained by inverting the measured cavity volume shrinkage data.

6. The method for predicting wellhead pressure of a salt cavern hydrogen / helium storage according to claim 2, characterized in that: The calculation method of the hydrogen / helium temperature field distribution T is: In formula (7), A is the cross-sectional area of ​​the wellbore or salt cavern; ρ is the density of hydrogen / helium; C v,g is the specific heat capacity of hydrogen / helium; T f is the temperature of hydrogen / helium; t is the time; μ jT is the Joule-Thomson coefficient of hydrogen / helium; p is the pressure of hydrogen / helium; Q e is the convective heat transfer rate between hydrogen / helium and surrounding rock, Q e The calculation method is: Q e =2πr0U we (T e -T f ) Formula (8); In formula (8), r0 is the radius of the wellbore or salt cavern; U we is the comprehensive heat transfer coefficient between the gas and the surrounding environment; T e is the formation temperature, T e The calculation method is: In formula (9), r is the distance from the center of the gas storage; ρ e is the density of the formation rock; C e is the specific heat capacity of the formation rock; k e is the thermal conductivity of the formation rock; By combining equations (7) to (9), the change of hydrogen / helium temperature in the chamber with time during the gas injection and reservoir construction can be calculated.

7. A salt cavern hydrogen / helium storage wellhead pressure prediction system, characterized in that: include: Basic data collection unit, used to collect basic data of salt cavern hydrogen / helium storage; A state monitoring unit, including a state monitor, for recording historical gas injection and production data of the salt cavern hydrogen / helium storage and the current state of the hydrogen / helium storage; The leakage rate quantitative evaluation unit uses the basic data and status monitoring data of the salt cavern hydrogen / helium storage to quantitatively simulate the hydrogen / helium leakage, hydrogen / helium dissolution, gas thermal effect and hydrogen / helium storage cavity shrinkage in the storage; The wellhead pressure prediction unit predicts the change trend of the wellhead pressure according to the influence of the four effects on the wellhead pressure change obtained by the leakage rate quantitative evaluation unit.

8. The salt cavern hydrogen / helium storage wellhead pressure prediction system according to claim 7, characterized in that: The basic data for quantitatively evaluating the leakage rate of the salt cavern hydrogen / helium storage is input into the basic data collection unit, including the sonar cavity measurement data of the salt cavern cavity, the wellbore trajectory, the wellbore structure and the size of the gas injection string.

9. The salt cavern hydrogen / helium storage wellhead pressure prediction system according to claim 7, characterized in that: The status monitoring unit also includes a gas flow meter, a manifold valve and a wellhead temperature and pressure gauge arranged on the surface injection and production manifold, which are used to record the historical injection and production data of the salt cavern hydrogen / helium storage, and then obtain the inventory gas volume in the salt cavern hydrogen / helium storage cavity and the current status of the hydrogen / helium storage, including the switch status of the manifold valve, wellhead pressure and temperature parameters.

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