Air compression energy storage method and system based on liquid pressure control

Abstract

The invention relates to an air compression energy storage method and system based on liquid pressure control, which can improve the energy storage capacity of compressed air energy storage under the condition that the volume of an underground cavity is not increased by means of the action of liquid for pressure control in the underground cavity. The technical problems that in the prior art, the energy storage capacity can only be improved by increasing the size of the underground gas storage cavity, and site selection is difficult and cost is high when the size of the underground gas storage cavity is increased are solved. Moreover, the liquid is injected into the underground cavity, so that the pressure of the underground cavity is kept stable in the energy storage and release processes, on one hand, the energy storage capacity is improved, and on the other hand, the influence of pressure circulation fluctuation on the integrity of the underground cavity is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground energy storage, and particularly relates to a method and system for compressed air energy storage based on liquid pressure control. Background Art

[0002] Many renewable energy sources such as solar energy and wind energy have daily and seasonal intermittency, and their power outputs are unstable, making them unsuitable for providing base load power supplies. Therefore, it is difficult to directly feed into the power grid. Solving the energy storage problem is the key to successfully expanding the scale of renewable energy production. Therefore, how to store excess clean electricity on a large scale and stably transmit electricity when both sunlight and wind power supplies are insufficient remains a technical problem that countries are working hard to solve.

[0003] As a mature energy storage technology, compressed air energy storage has the advantages of large energy storage capacity, long service life, and strong stability. However, due to the low energy density of compressed air, the underground cavity for storing compressed air requires a relatively large capacity, usually between tens of thousands and hundreds of thousands of cubic meters. Without changing the rated output power, to increase the energy storage / discharge time of a compressed air energy storage power station, only by increasing the volume of the underground gas storage cavity can the energy storage capacity be improved. For example, finding larger salt caverns or building larger underground chambers, but this limits the site selection range of compressed air energy storage or significantly increases the construction cost of artificial chambers.

[0004] Therefore, there is an urgent need for a method with low investment and construction costs that can increase the energy storage capacity of compressed air energy storage without increasing the volume of the underground cavity. Summary of the Invention

[0005] In view of this, the present invention provides a method and system for compressed air energy storage based on liquid pressure control, which can increase the energy storage capacity of compressed air energy storage without increasing the volume of the underground cavity, thereby solving the technical problems in the prior art that only by increasing the volume of the underground gas storage cavity can the energy storage capacity be improved, and increasing the volume of the underground gas storage cavity faces difficulties in site selection and high costs.

[0006] The first aspect of the present invention discloses a method for compressed air energy storage based on liquid pressure control, including the following steps:

[0007] S1, respectively construct an independent gas delivery wellbore and a liquid delivery wellbore, and construct an underground cavity that is respectively connected to the gas delivery wellbore and the liquid delivery wellbore; where the so-called independence means that the gas delivery wellbore and the liquid delivery wellbore are not directly connected, but are respectively connected to the underground cavity.

[0008] S2, inject liquid for pressure control into the underground cavity through the liquid delivery wellbore, so that the underground cavity is filled with liquid for pressure control, and the liquid level of the liquid for pressure control in the underground cavity is higher than the connection port between the liquid delivery wellbore and the underground cavity.

[0009] S3. Inject compressed air into the gas transmission wellbore and allow the compressed air to enter the underground cavity for energy storage, where the compressed air can drive the pressure-control liquid in the underground cavity to enter the liquid transmission wellbore from the underground cavity and be discharged back through the liquid transmission wellbore.

[0010] S4. Monitor whether there is a power generation demand. If not, block the gas transmission wellbore to maintain the pressure of the compressed air in the underground cavity. If there is a demand, discharge the compressed air from the gas transmission wellbore for energy release and power generation. At this time, the pressure-control liquid returns from the liquid transmission wellbore to the underground cavity.

[0011] Among them, the gas transmission wellbore and the liquid transmission wellbore can be newly created wellbores or existing wellbores. The gas transmission wellbore is only used for transporting and discharging compressed air, while the liquid transmission wellbore is only used for transporting and discharging the pressure-control liquid. Specifically, in step S2, when the pressure-control liquid is injected into the underground cavity, there is pressure-control liquid in both the underground cavity and the liquid transmission wellbore. That is, at this time, the pressure-control liquid in the underground cavity and the liquid transmission wellbore (which can be the liquid transmission wellbore itself or the back-discharge pipeline set in the liquid transmission wellbore) is used as a whole for pressure control during compressed air energy storage and energy release, and can achieve automatic pressure control when storing and releasing energy based on compressed air.

[0012] Specifically, when injecting compressed air in step S3, the pressure formed by the compressed air in the underground cavity can force the pressure-control liquid to flow from the underground cavity into the liquid transmission wellbore and be discharged outward from the liquid transmission wellbore. That is, the pressure of the compressed air in the underground cavity should be greater than the hydrostatic pressure corresponding to the depth of the pressure-control liquid in the underground cavity. By means of the action of the pressure-control liquid in the underground cavity and the liquid transmission wellbore, it is possible to increase the energy storage capacity of compressed air energy storage without increasing the volume of the underground cavity, solving the technical problems in the prior art that only by increasing the volume of the underground gas storage cavity can the energy storage capacity be improved, and increasing the volume of the underground gas storage cavity is faced with difficulties in site selection and high costs.

[0013] When there is no power generation demand, the gas transmission wellbore is blocked to maintain the pressure of the compressed air in the gas transmission wellbore and the underground cavity, that is, to maintain the energy storage state. At this time, the energy storage achieved based on compressed air at least includes the compression potential energy accumulated by the compressed air due to the increase in pressure in the overall space of the gas transmission wellbore and / or the underground cavity itself. In addition to this compression potential energy, the stored energy can also include: the geothermal energy obtained by the heat exchange between the compressed air and the formation rock.

[0014] When there is a power generation demand, the compressed air with energy can be discharged in the opposite direction through the gas delivery wellbore to do work on the external power generation device for power generation. During the process of discharging the compressed air in the opposite direction, based on automatic pressure control, since the pressure of the compressed air in the underground cavity becomes smaller, the pressure-control liquid in the liquid delivery wellbore can automatically return to the underground cavity, thus causing the liquid level of the pressure-control liquid in the underground cavity to rise.

[0015] That is to say, in the present invention, based on the interaction between the pressure-control liquid and the compressed air in the underground cavity, automatic pressure control can be achieved, enabling the pressure in the underground cavity to remain stable during the energy storage and energy release processes. On the one hand, the energy storage capacity is increased in the underground cavity with a limited volume, and on the other hand, the impact of pressure cyclic fluctuations on the integrity of the underground cavity is reduced.

[0016] Furthermore, the gas delivery wellbore and the liquid delivery wellbore can be set in a one-to-one, one-to-many, or many-to-many relationship. That is, in the present invention, the gas delivery wellbore can be set to one, and the liquid delivery wellbore can be set to one, forming a one-to-one relationship between the two, and both are respectively in communication with the underground cavity; or, the gas delivery wellbore is set to one, while the liquid delivery wellbore is set to multiple (more than two), then the one gas delivery wellbore corresponds to multiple liquid delivery wellbores, and the one gas delivery wellbore and the multiple liquid delivery wellbores are both respectively in communication with the underground cavity. Of course, vice versa, that is, the gas delivery wellbore is set to multiple (more than two), and the liquid delivery wellbore is set to one; or, the gas delivery wellbore is set to multiple (more than two), and the liquid delivery wellbore is also set to multiple (more than two), and the multiple gas delivery wellbores and the multiple liquid delivery wellbores are both respectively in communication with the underground cavity. In the above multiple cases, the underground cavity is set to one. Additionally, preferably, in the present invention, both the gas delivery wellbore and the liquid delivery wellbore are set to vertical wells or inclined wells, so that the gas or liquid located therein has its own gravitational potential energy.

[0017] Furthermore, the position of the communication port between the gas delivery wellbore and the underground cavity is higher than the position of the communication port between the liquid delivery wellbore and the underground cavity, or the bottom position of the gas delivery wellbore is higher than the bottom position of the liquid delivery wellbore. This can effectively ensure that after injecting the pressure-control liquid, the liquid level of the pressure-control liquid is lower than the communication port between the gas delivery wellbore and the underground cavity and higher than the communication port between the liquid delivery wellbore and the underground cavity.

[0018] Furthermore, before step S2, there is also a step of performing a sealing test on the underground cavity. Based on the sealing test, the sealing condition of the underground cavity can be well judged. When the sealing of the underground cavity does not meet the requirements, leakage prevention construction on the underground cavity can be carried out in a timely manner.

[0019] Furthermore, the hydrostatic pressure of the pressure-control liquid in the underground cavity is configured to be less than the fracture pressure of the formation rock where the underground cavity is located; and / or, an additional material for maintaining sealing is provided on the inner wall of the underground cavity, and the hydrostatic pressure of the pressure-control liquid in the underground cavity is less than the fracture pressure of the additional material on the inner wall of the underground cavity. This can effectively ensure that the formation rock of the underground cavity and / or the additional material on the inner wall of the underground cavity will not be damaged due to the pressure of the pressure-control liquid, thereby further ensuring the sealing performance of the underground cavity.

[0020] Furthermore, a water storage tank or a pressure vessel is provided corresponding to the liquid delivery wellbore, and a weight for maintaining pressure is provided in the pressure vessel. With the help of the weight, the pressure of the pressure-control liquid can be further increased, and then the compressed air can have a higher pressure to force the pressure-control liquid to flow back, thereby further increasing the energy storage capacity of the underground cavity.

[0021] In step S2, when the initial filling is completed, the liquid level of the pressure-control liquid filled in the liquid delivery wellbore is in the water storage tank or the pressure vessel, and its liquid level is higher than the liquid level position of the pressure-control liquid in the underground cavity; in step S3, the pressure-control liquid can flow back to the surface water storage tank or the pressure vessel through the liquid delivery wellbore; and, in step S3, it is monitored whether the liquid level in the water storage tank or the height of the pressurizing object in the pressure vessel reaches the liquid level threshold. If the preset liquid level threshold is reached, the injection of compressed air into the underground cavity is stopped.

[0022] Furthermore, in step S4, the pressure-control liquid returns to the underground cavity through the liquid delivery wellbore by virtue of the energy given by its own gravitational potential energy or the combination of its own gravitational potential energy and the gravitational potential energy of the pressurizing object. That is, in the process of releasing energy from the compressed air in step S4, there is no need to set up an additional pressure-providing device. The pressure-control liquid can be transported from the liquid delivery wellbore to the underground cavity by virtue of its own gravitational potential energy (corresponding to the case of the water storage tank) or the combination of its own gravitational potential energy and the gravitational potential energy of the pressurizing object (corresponding to the case of the pressure vessel with a pressurizing object). This can not only achieve automatic pressure control, but also greatly save energy consumption and reduce costs.

[0023] Furthermore, in step S3, the pressure at the wellhead of the gas delivery wellbore and / or inside the gas delivery wellbore and / or in the underground cavity is monitored to determine whether the pressure in the underground cavity reaches the preset pressure threshold; when it is determined that the preset pressure threshold is reached, the injection of compressed air into the underground cavity is stopped.

[0024] Furthermore, before step S2, there is also a step of configuring the density of the pressure-control liquid to be injected based on the depth of the underground cavity, which includes:

[0025] Obtain the depth of the underground cavity constructed in step S1;

[0026] Determine whether the depth of the underground cavity is less than a preset depth threshold; when the depth of the underground cavity is less than the preset depth threshold, configure the density of the pressure control liquid to be greater than the density of water.

[0027] For an underground cavity with a depth less than the preset depth threshold, through the configuration of the density of the pressure control liquid, it can have a relatively high hydrostatic pressure even with a shallow depth. That is, it is possible to increase the hydrostatic pressure without digging deeper into the underground cavity, thereby increasing the working pressure of the underground cavity and further increasing the energy storage capacity.

[0028] Further, add a weighting agent with a particle size less than 200 microns and a density greater than that of water to the pressure control liquid to configure the density of the pressure control liquid to be greater than the density of water; wherein the weighting agent includes: at least one ceramsite, and / or at least one resin, and / or at least one quartz sand, and / or at least one barite, and / or at least one hematite, and / or at least one ilmenite, and / or at least one manganese ore, and / or at least one calcium carbonate, and / or at least one magnesium-aluminum-iron spinel, and / or at least one metal oxide, and / or at least one silicate, and / or at least one lead ore, and / or at least one fusible alloy.

[0029] That is, in the present invention, the density of the pressure control liquid is increased by adding a weighting agent thereto, and the weighting agent is a particulate matter with a particle size structure of 200 microns or less. Preferably, in the present invention, the density of the pressure control liquid can be configured only by using particulate matter with a particle size structure of 200 microns or less as the weighting agent. Of course, those skilled in the art can also understand that the particulate matter with a particle size structure of 200 microns or less as the weighting agent in the present invention can also be used in combination with a small amount of large particle proppants to achieve the purpose of the present invention, which is also within the protection scope of the present invention, and the present invention does not exclude this.

[0030] Further, in addition to adding a weighting agent with a particle size less than 200 microns and a density greater than that of water to the pressure control liquid, add a dispersant to the pressure control liquid, wherein the dispersant includes: at least one clay, and / or at least one silicate, and / or at least one lignosulfonate, and / or at least one polycarboxylate, and / or at least one humate, and / or at least one sulfonated polymer, and / or at least one phosphate, and / or at least one cellulose, and / or at least one polymer, and / or at least one oxide. By adding the dispersant, the attraction between the weighting agent particles can be reduced, preventing the weighting agent particles from aggregating to form large particles (flocculation), thereby maintaining the uniform dispersion of the particles.

[0031] Furthermore, in addition to adding weighting agents with a particle size less than 200 microns and a density greater than that of water to the pressure control liquid, a suspending agent is added to the pressure control liquid, where the suspending agent includes: at least one natural polymer and its derivatives, and / or at least one cellulose and its derivatives, and / or at least one synthetic polymer, and / or at least one surfactant-type thickener, and / or at least one gel-type thickener, and / or at least one clay, and / or at least one silicate. By adding the suspending agent, the static viscosity of the liquid can be increased, thereby preventing the settling of the weighting agent particles and increasing the suspension time of the weighting agent in the liquid.

[0032] Furthermore, based on the combined configuration of the weighting agent, dispersant and suspending agent, the density of the pressure control liquid is more than twice that of water, and within the set maximum energy storage time, the weighting agent particles in the liquid will not all settle to the bottom of the underground cavity or the reservoir or pressure vessel provided in the corresponding liquid delivery wellbore.

[0033] Furthermore, the weighting agent at least includes ilmenite powder, the dispersant at least includes sodium polycarboxylate and / or polycarboxylic acid ether, and the suspending agent at least includes bentonite or a combination of bentonite and xanthan gum to configure a high-density liquid. Sodium polycarboxylate adsorbs on the surface of ilmenite particles, generating a steric hindrance effect and electrostatic repulsion to prevent particle aggregation due to van der Waals forces. The long side chains of polycarboxylic acid ether can form an adsorption layer on the surface of the ore powder particles. When the ore powder particles approach each other, these adsorption layers will overlap, generating a steric hindrance effect and improving the dispersibility of the ore powder. When bentonite encounters water, water molecules are adsorbed between the layers, and the volume expands by 10 - 15 times, forming a three-dimensional network gel structure, significantly increasing the viscosity of the system. A high-viscosity gel is formed during static settling to prevent particle settlement; fluidity is restored during stirring, reducing the flow resistance. Xanthan gum provides high viscosity during static settling; the viscosity decreases during stirring, facilitating pumping and can be compounded with bentonite to compensate for the performance loss of bentonite in a high-salt environment.

[0034] In a specific embodiment, based on a total liquid mass of 1000 grams per unit, the specific configuration components are as follows: ilmenite powder is 600 - 750 grams, the water matrix is 200 - 400 grams, sodium polycarboxylate and / or polycarboxylic acid ether is 1 - 20 grams, and bentonite or a combination of bentonite and xanthan gum is 10 - 60 grams. A small amount of sodium hydroxide is added externally to adjust the pH value to neutral. Specifically, the ilmenite powder is any value within the range of 600 - 750 including the endpoints, the water matrix is any value within the range of 200 - 400 including the endpoints, sodium polycarboxylate and / or polycarboxylic acid ether is any value within the range of 1 - 20 including the endpoints, and bentonite or a combination of bentonite and xanthan gum is any value within the range of 10 - 50 including the endpoints, as long as the total mass of the liquid after adding these components is 1000 grams.

[0035] In another embodiment, the weighting agent at least includes barite powder, the dispersant at least includes sodium polycarboxylate and / or polycarboxylic acid ether, and the suspending agent at least includes bentonite or a combination of bentonite and xanthan gum to prepare a high-density liquid. Sodium polycarboxylate adsorbs on the surface of barite particles, generating a steric hindrance effect and electrostatic repulsion to prevent particle aggregation due to van der Waals forces. The long side chains of polycarboxylic acid ether can form an adsorption layer on the surface of ore powder particles. When the ore powder particles approach each other, these adsorption layers will overlap, generating a steric hindrance effect and improving the dispersibility of the ore powder. When bentonite encounters water, water molecules are adsorbed between its layers, and its volume expands by 10 - 15 times, forming a three-dimensional network gel structure, significantly increasing the viscosity of the system. When standing, a high-viscosity gel is formed to prevent particle sedimentation; when stirred, the fluidity is restored, reducing the flow resistance. Xanthan gum provides high viscosity when standing; its viscosity decreases when stirred, facilitating pumping, and its combination with bentonite can compensate for the performance loss of bentonite in a high-salt environment.

[0036] In a specific embodiment, based on 1000 grams of the total mass of the liquid, the specific composition is as follows: 600 - 800 grams of barite powder, 150 - 300 grams of water matrix, 1 - 20 grams of sodium polycarboxylate and / or polycarboxylic acid ether, and 10 - 60 grams of bentonite or a combination of bentonite and xanthan gum. A small amount of sodium hydroxide is added to adjust the pH value to 8 - 10, enhancing the negative charges on the surfaces of bentonite and barite powder, and synergistically improving the dispersion stability with sodium polycarboxylate.

[0037] Further, in the step of preparing the pressure-control liquid, it further includes: adding a pH regulator to the water matrix. The pH regulator includes: at least one inorganic acid, and / or at least one organic acid, and / or at least one inorganic base, and / or at least one organic base, and / or at least one buffer.

[0038] The present invention also discloses a system for implementing the air compression energy storage method based on liquid pressure control according to the first aspect of the present invention, which includes:

[0039] A gas delivery wellbore;

[0040] A liquid delivery wellbore, which is independent of the gas delivery wellbore;

[0041] An underground cavity, which is respectively connected to the gas delivery wellbore and the liquid delivery wellbore, and is capable of injecting the pressure-control liquid into the underground cavity through the liquid delivery wellbore, such that both the liquid delivery wellbore and the underground cavity are filled with the pressure-control liquid, wherein the liquid level of the pressure-control liquid in the underground cavity is higher than the connection port between the liquid delivery wellbore and the underground cavity;

[0042] A compressed air injection device, which injects compressed air into the gas delivery wellbore and enables the compressed air to enter the underground cavity, driving the pressure-control liquid in the underground cavity to enter the liquid delivery wellbore and be discharged through the liquid delivery wellbore for energy storage;

[0043] A plugging device for plugging a gas transmission wellbore.

[0044] A monitoring device for monitoring whether there is a power generation demand.

[0045] A power generation device for generating electricity by means of the energy released from the compressed air discharged from the gas transmission wellbore in reverse.

[0046] When no power generation demand is monitored, the wellhead of the gas transmission wellbore is plugged by means of the plugging device to maintain the compressed air pressure in the underground cavity; when a power generation demand is monitored, the power generation device generates electricity by means of the energy released from the compressed air discharged from the gas transmission wellbore in reverse, and at the same time, the pressure control liquid returns to the underground cavity through the liquid transmission wellbore.

[0047] Advantageous effects: In the air compression energy storage method and system based on liquid pressure control of the present invention, by means of the action of the pressure control liquid in the underground cavity, it is possible to increase the energy storage capacity of compressed air energy storage without increasing the volume of the underground cavity, solving the technical problems in the prior art that the energy storage capacity can only be increased by increasing the volume of the underground gas storage cavity, and increasing the volume of the underground gas storage cavity faces difficulties in site selection and high costs. Moreover, in the present invention, by injecting liquid into the underground cavity, the pressure in the underground cavity remains stable during the energy storage and energy release processes. On the one hand, the energy storage capacity is increased, and on the other hand, the influence of pressure cyclic fluctuations on the integrity of the underground cavity is reduced.

[0048] Moreover, in the preferred embodiment of the present invention, by configuring the density of the liquid injected into the underground cavity, it is possible to further increase the energy storage capacity of the underground cavity without increasing the volume of the underground cavity. In another preferred embodiment, by configuring a pressure-increasing substance in the pressure vessel, the energy storage capacity of the underground cavity can also be further increased.

[0049] The air compression energy storage method and system based on liquid pressure control of the present invention will be described in detail below in combination with the embodiments shown in the drawings and the reference numerals. Description of the Drawings

[0050] Figure 1 The flowchart of the steps of the air compression energy storage method based on liquid pressure control disclosed in the first aspect of the present invention is shown.

[0051] Figure 2 The structural schematic diagram of the air compression energy storage system based on liquid pressure control disclosed in the second aspect of the present invention is shown.

[0052] Figure 3 The comparison effect diagram between traditional compressed air energy storage and the air compression energy storage method based on liquid pressure control of the present invention is shown. Detailed Embodiments

[0053] It should be specifically noted that the "liquid" in this text can be, but is not limited to, liquid fluids, emulsions, slurries, and solid particle flows with flow characteristics similar to those of liquids.

[0054] The "wellbore" in this text refers to a hole formed by drilling or inserting a conduit into a formation. Generally, the wellbore is cylindrical, so the cross-section of the wellbore may be circular. Additionally, the wellbore may have any other cross-section. The wellbore can be an open hole, i.e., an open-hole wellbore, or a cased wellbore with a cemented casing on the inner wall of the wellbore. The wellbore can be a vertical well, a horizontal well, or an inclined well.

[0055] The "formation fracture pressure" in this text is the minimum pressure that causes fractures in the formation. The formation fracture pressures at different depths can be obtained by various methods, such as through on-site measurements (overflow tests, formation integrity tests, mini-frac tests, step-rate tests, etc.), empirical formulas, rock mechanics model equations, logging data, numerical modeling, and other methods.

[0056] The "constant" or "unchanged" in this text does not mean that the absolute change of the specified item is zero, but rather that the change of the specified item is very small and can be considered constant in engineering practice. For example, the term "constant / unchanged" in this disclosure can also have the meaning of "approximately constant / unchanged". It should also be recognized that the term "equal / to be equal to" used in this disclosure does not mean that the specified items are exactly the same, but rather that two items with negligible differences in engineering practice are specified. For example, the term "equal / to be equal to" in this disclosure can also have the meaning of "approximately equal / to be approximately equal to".

[0057] The "hydrostatic pressure" in this text refers to the pressure generated at a certain point inside a liquid at rest due to the action of gravity. Its basic formula is:

[0058] P = P0 + ρgh

[0059] where P is the hydrostatic pressure at a certain place, P0 is the atmospheric pressure on the liquid surface of the liquid used for pressure control or the pressure applied on the liquid surface, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the vertical depth from this place to the liquid surface.

[0060] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0061] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0062] Figure 1 The step flow chart of the air compression energy storage method based on liquid pressure control of the present invention is shown. Combining Figure 1 As shown, a first aspect of the present invention discloses an air compression energy storage method based on liquid pressure control, including the following steps:

[0063] S1, respectively construct an independent gas delivery wellbore and a liquid delivery wellbore, and construct an underground cavity communicating with the gas delivery wellbore and the liquid delivery wellbore respectively; where the so-called independence means that the gas delivery wellbore and the liquid delivery wellbore are not directly connected, but are respectively connected to the underground cavity;

[0064] S2, inject pressure control liquid into the underground cavity through the liquid delivery wellbore, so that the underground cavity is filled with pressure control liquid, where the liquid level of the pressure control liquid in the underground cavity is higher than the communication port between the liquid delivery wellbore and the underground cavity;

[0065] S3, inject compressed air into the gas delivery wellbore, and make the compressed air enter the underground cavity for energy storage; where the compressed air can drive the pressure control liquid in the underground cavity to enter the liquid delivery wellbore from the underground cavity and be discharged back through the liquid delivery wellbore;

[0066] S4, monitor whether there is a power generation demand. If not, block the gas delivery wellbore and maintain the pressure of the compressed air in the underground cavity. If so, discharge the compressed air from the gas delivery wellbore for energy release and power generation. At this time, the pressure control liquid returns to the underground cavity through the liquid delivery wellbore.

[0067] Among them, in step S1, the gas delivery wellbore is only responsible for injecting and discharging gas into and from the underground cavity, and the liquid delivery wellbore is only responsible for injecting and discharging liquid into and from the underground cavity. In a specific embodiment, the gas delivery wellbore and the liquid delivery wellbore are first drilled, and then the underground cavity is excavated.

[0068] In some embodiments, the gas delivery wellbore and the liquid delivery wellbore can be arranged in a one-to-one, one-to-many, or many-to-many relationship. Specifically, one gas delivery wellbore can be provided, and one liquid delivery wellbore can be provided, forming a one-to-one relationship, and both are respectively in communication with the underground cavity; or, one gas delivery wellbore is provided, while multiple (more than two) liquid delivery wellbores are provided, then the one gas delivery wellbore corresponds to multiple liquid delivery wellbores, and both the one gas delivery wellbore and the multiple liquid delivery wellbores are respectively in communication with the underground cavity. Of course, vice versa, that is, multiple (more than two) gas delivery wellbores are provided, while one liquid delivery wellbore is provided; or, multiple (more than two) gas delivery wellbores are provided, and multiple (more than two) liquid delivery wellbores are also provided, and both the multiple gas delivery wellbores and the multiple liquid delivery wellbores are respectively in communication with the underground cavity. In the above multiple cases, only one underground cavity is provided. Additionally, preferably, in the present invention, both the gas delivery wellbore and the liquid delivery wellbore are provided as vertical shafts, so that the gas or liquid located therein has its own gravitational potential energy.

[0069] In a specific embodiment, the position of the communication port between the gas delivery wellbore and the underground cavity is higher than the position of the communication port between the liquid delivery wellbore and the underground cavity, or the bottom position of the gas delivery wellbore is higher than the bottom position of the liquid delivery wellbore. This can effectively ensure that after injecting the pressure control liquid, the liquid level of the pressure control liquid is lower than the communication port between the gas delivery wellbore and the underground cavity and higher than the communication port between the liquid delivery wellbore and the underground cavity.

[0070] In step S2, liquid is injected into the underground cavity to increase the pressure of the underground cavity.

[0071] In a specific embodiment, before step S2, there is also a step of performing a sealing test on the underground cavity. Based on the sealing test, the sealing condition of the underground cavity can be well judged. When the sealing of the underground cavity does not meet the requirements, leakage prevention construction on the underground cavity can be carried out in a timely manner.

[0072] The step of performing a sealing test on the underground cavity can include: plugging the wellhead of the liquid delivery wellbore; injecting compressed air into the underground cavity from the gas delivery wellbore; plugging the wellhead of the gas delivery wellbore and monitoring the pressure at the wellhead or inside the wellbore; judging the sealing condition of the underground cavity through the pressure change.

[0073] For example, if the wellhead pressure remains stable or the pressure drop per unit time is less than a threshold value (for example, the pressure drop does not exceed 0.1 MPa per hour), it proves that the underground cavity has good sealing performance. Through the pressure drop data, the leakage rate of compressed air within a certain time period can be calculated. A threshold value for the daily leakage rate can also be given to determine the threshold value of the pressure drop per unit time. If the wellhead pressure drops rapidly or is greater than the set threshold value, it proves that the underground cavity has poor sealing performance. If the sealing performance of the underground cavity does not meet the requirements, anti-leakage construction needs to be carried out on the underground cavity again until the sealing performance of the underground cavity meets the design requirements.

[0074] It should be emphasized that the sealing test of the underground cavity must be completed before step S2. If the sealing test of the underground cavity must be carried out after step S2 and before step S3, it will be difficult to judge the sealing performance of the underground cavity and the wellbore through pressure monitoring because the pressure-control liquid will keep the pressure of the underground cavity relatively stable.

[0075] In a specific embodiment, the hydrostatic pressure of the pressure-control liquid in the underground cavity is configured to be less than the fracture pressure of the formation rock where the underground cavity is located; and / or, additional materials for maintaining sealing are provided on the inner wall of the underground cavity, and the additional materials can maintain the sealing performance and stability of the underground cavity, and the hydrostatic pressure of the pressure-control liquid in the underground cavity is less than the fracture pressure (the minimum pressure at which cracks occur in the additional materials) of the additional materials on the inner wall of the underground cavity. This can effectively ensure that the formation rock of the underground cavity and / or the additional materials on the inner wall of the underground cavity will not be damaged due to the pressure of the pressure-control liquid, thereby further ensuring the sealing performance of the underground cavity.

[0076] In a specific embodiment, a reservoir or a pressure vessel is provided corresponding to the liquid delivery wellbore. Among them, the reservoir and / or the pressure vessel can be provided corresponding to the wellhead of the liquid delivery wellbore. At this time, the reservoir can be a ground reservoir; optionally, the reservoir and / or the pressure vessel are correspondingly arranged inside the well of the liquid delivery wellbore.

[0077] Weights for maintaining pressure are provided in the pressure vessel. With the help of the weights, the pressure of the pressure-control liquid can be further increased, and then the compressed air can have a higher pressure to force the pressure-control liquid to flow back, thereby further increasing the energy storage capacity of the underground cavity.

[0078] In a specific embodiment, the mass of the pressurizing object for maintaining the pressure of the pressure vessel needs to be determined through data such as liquid density, underground cavity depth, and target working pressure. In another embodiment, the pressurizing object can maintain the pressure of the pressure vessel through other hydraulic systems.

[0079] In other embodiments, the pressurizing object for maintaining the pressure of the pressure vessel and the liquid are separated by other materials.

[0080] In a specific embodiment, the pressurizing medium is a liquid.

[0081] In another embodiment, the pressure maintenance of the pressurizing container comes from other hydraulic systems or liquid boosting systems, including but not limited to the following pressurizing devices: booster pumps, piston pumps, centrifugal pumps, gear pumps, hydraulic cylinders.

[0082] In step S2, when the initial filling is completed, the liquid level of the pressure control liquid filled in the liquid delivery wellbore is in the reservoir or the pressure vessel, and its liquid level is higher than the liquid level position of the pressure control liquid in the underground cavity.

[0083] In step S3, compressed air is injected into the underground cavity from the gas delivery wellbore for energy storage, while displacing the liquid in the underground cavity into the liquid delivery wellbore and discharging it from the underground cavity. In step S3, the pressure control liquid can be discharged back to the ground reservoir or the pressure vessel through the liquid delivery wellbore; specifically, in step S3, during the continuous injection of compressed air into the underground cavity, the pressure of the compressed air in the underground cavity increases until it is higher than the hydrostatic pressure of the liquid contact surface, and then starts to displace the pressure control liquid in the underground cavity into the liquid delivery wellbore, raising the liquid level of the ground reservoir or the height of the pressurizing medium in the pressure vessel. The degree of increase in the pressure of the compressed air in the underground cavity depends on the height of the liquid level drop in the underground cavity and the height of the liquid level rise in the ground reservoir. Usually, the sum of the height of the liquid level drop in the underground cavity and the height of the liquid level rise in the ground reservoir (tens of meters) is much smaller than the depth of the underground cavity (hundreds of meters to several kilometers), so it can be approximately considered that the hydrostatic pressure of the underground cavity remains unchanged and the pressure of the compressed air in the underground cavity remains unchanged.

[0084] And, in step S3, monitor whether the liquid level in the reservoir or the height of the pressurizing medium in the pressure vessel reaches the liquid level threshold. If the preset liquid level threshold is reached, stop injecting compressed air into the underground cavity.

[0085] In another embodiment, in step S3, monitor the pressure at the wellhead of the gas delivery wellbore and / or inside the gas delivery wellbore and / or in the underground cavity, and determine whether the pressure in the underground cavity reaches the preset pressure threshold; when it is determined that the preset pressure threshold is reached, stop injecting compressed air into the underground cavity.

[0086] In step S4, monitor whether there is a power generation demand. If not, block the wellhead of the gas delivery wellbore and maintain the pressure of the compressed air in the underground cavity. If there is, discharge the compressed air from the gas delivery wellbore for power generation, and at the same time inject liquid into the underground cavity through the liquid delivery wellbore.

[0087] In a specific embodiment, in step S4, the pressure-control liquid returns to the underground cavity through the liquid delivery wellbore by virtue of the energy given by its own gravitational potential energy or the combination of its own gravitational potential energy and the gravitational potential energy of the pressurizing object. That is, in the process of releasing energy from the compressed air in step S4, there is no need to set up an additional pressure-providing device. The pressure-control liquid can be transported from the liquid delivery wellbore to the underground cavity by virtue of its own gravitational potential energy (corresponding to the case of the reservoir) or the combination of its own gravitational potential energy and the gravitational potential energy of the pressurizing object (corresponding to the case of the pressure vessel with a pressurizing object). This can not only achieve automatic pressure control, but also greatly save energy consumption and reduce costs.

[0088] In a specific embodiment, the reverse flow of compressed air in the gas delivery wellbore generates electricity through a ground expander. In another embodiment, in step S3, the heat generated by the compressed air is stored by a ground heat storage device and used for other purposes, such as preheating the air entering the expander or providing heat energy for other processes.

[0089] In addition, in a preferred embodiment, before step S2, there is also a step of configuring the density of the pressure-control liquid to be injected based on the depth of the underground cavity, which includes:

[0090] Obtaining the depth of the underground cavity constructed in step S1;

[0091] Judging whether the depth of the underground cavity is less than a preset depth threshold; when the depth of the underground cavity is less than the preset depth threshold, the density of the pressure-control liquid is configured to be greater than the density of water.

[0092] For an underground cavity with a depth less than the preset depth threshold, through the density configuration of the pressure-control liquid, even if it has a relatively shallow depth, it can have a relatively high hydrostatic pressure. That is, without deepening the underground cavity, the hydrostatic pressure can be increased, thereby increasing the working pressure of the underground cavity and further increasing the energy storage capacity.

[0093] That is, increasing the density of the injected pressure-control liquid can increase the hydrostatic pressure of the liquid in the underground cavity, thereby increasing the pressure for the compressed air in the underground cavity to displace the pressure-control liquid. In other words, increasing the density of the injected liquid increases the working pressure of the underground cavity and increases the energy storage capacity. Generally, the greater the density of the injected pressure-control liquid, the greater the compressed air capacity of the underground cavity. However, if the density of the liquid is too large, the hydrostatic pressure of the liquid in the underground cavity will exceed the safe working pressure of the underground cavity. To avoid the risk of formation rock damage, the density of the injected liquid can be configured so that the hydrostatic pressure of the liquid in the underground cavity does not exceed the formation fracture pressure of the formation where the underground cavity is located.

[0094] Specifically, whether the density of the liquid for pressure control is configured to be greater than the density of water depends on the depth of the underground cavity. When the depth of the underground cavity is lower than the preset depth threshold, the density of the liquid needs to be configured to be greater than the density of water. The preset depth threshold can be calculated by evaluating the influence of the liquid density on the energy storage capacity and economy through theoretical formulas or numerical simulation methods. For example, if 10 MPa is taken as the target working pressure of the underground cavity energy storage, then the preset depth threshold can be set to 1000 meters. That is, when the depth of the underground cavity is lower than 1000 meters, the density of the liquid needs to be configured to be greater than the density of water. Currently, during the operation of the underground cavity for compressed air energy storage, the pressure is 10 MPa or above, which is equivalent to a water head of 1000 m or above (the hydrostatic pressure with the water surface at atmospheric pressure). Therefore, when the depth of the underground cavity is lower than 1000 meters, to make the working pressure of the underground cavity reach 10 MPa or above, the density of the liquid injected into the underground cavity needs to be configured to be greater than the density of water. For example, when the underground cavity is only 300 meters underground, if water is used as the liquid injected into the underground cavity, then the hydrostatic pressure of the underground cavity (with the water surface at atmospheric pressure) is only 2.94 MPa, which is much lower than the working pressure of 10 MPa for traditional air compression energy storage. In this case, the energy storage capacity obtained by the air compression energy storage method based on liquid pressure control will be lower than that obtained by the traditional air compression energy storage method. If the working pressure of the 300-meter underground cavity needs to be increased to 10 MPa, then the density of the liquid injected into the underground cavity needs to be 3.4 times higher than the density of water. It should be noted that factors such as different target working pressures, different underground cavity sizes, or different economic indicators will all affect the calculation of the preset depth threshold.

[0095] In a preferred embodiment, a weighting agent with a particle size less than 200 microns and a density greater than that of water is added to the liquid for pressure control to configure the density of the liquid for pressure control to be greater than that of water; wherein, the weighting agent includes but is not limited to: at least one ceramsite, and / or at least one resin, and / or at least one quartz sand, and / or at least one barite, and / or at least one hematite, and / or at least one ilmenite, and / or at least one manganese ore, and / or at least one calcium carbonate, and / or at least one magnesium-aluminum-iron spinel, and / or at least one metal oxide, and / or at least one silicate, and / or at least one lead ore, and / or at least one fusible alloy.

[0096] That is, in the present invention, the density of the pressure-control liquid is increased by adding a weighting agent thereto, where the weighting agent is a particulate matter with a particle size structure of 200 microns or less. Preferably, in the present invention, the density of the pressure-control liquid can be configured by only using particulate matter with a particle size structure of 200 microns or less as the weighting agent. Of course, those skilled in the art can also understand that the particulate matter with a particle size structure of 200 microns or less as the weighting agent in the present invention can also be used in combination with a small amount of large particle proppants to achieve the purpose of the present invention, which is also within the protection scope of the present invention, and the present invention does not exclude this.

[0097] In a preferred embodiment, the step of configuring the pressure-control liquid further includes adding a dispersant to the pressure-control liquid, which can reduce the attraction between the weighting agent particles, prevent the weighting agent particles from aggregating to form large particles (flocculation), and thus maintain the uniform dispersion of the particles. The dispersant includes, but is not limited to: at least one clay (such as bentonite), and / or at least one silicate, and / or at least one lignosulfonate, and / or at least one polycarboxylate (such as sodium polycarboxylate and / or polycarboxylic acid ether), and / or at least one humate (such as sodium humate, potassium humate), and / or at least one sulfonated polymer (such as sulfonated styrene-maleic anhydride copolymer, sulfonated phenolic resin, sulfonated lignite resin), and / or at least one phosphate (such as sodium hexametaphosphate, sodium tripolyphosphate), and / or at least one cellulose (such as sodium carboxymethyl cellulose, polyanionic cellulose), and / or at least one polymer (such as hydrolyzed polyacrylonitrile, hydrolyzed polyacrylonitrile ammonium salt), and / or at least one oxide (such as silicon dioxide).

[0098] In a preferred embodiment, the step of configuring the pressure-control liquid further includes adding a suspending agent to the pressure-control liquid, which can increase the static viscosity of the liquid, thereby preventing the weighting agent particles from settling and increasing the suspension time of the weighting agent in the liquid. The suspending agent includes: at least one natural polymer and its derivatives (such as guar gum, carboxymethyl guar gum, hydroxypropyl guar gum, xanthan gum, artemisia sphaerocephala gum, etc.), and / or at least one cellulose and its derivatives (such as hydroxymethyl cellulose, carboxymethyl cellulose, carboxymethyl hydroxyethyl cellulose, hydroxyethyl cellulose, etc.), and / or at least one synthetic polymer (such as polyacrylamide, polyethylene oxide, acrylic polymer, polyvinyl alcohol, etc.), and / or at least one surfactant-type thickener, and / or at least one gel-type thickener (such as a gel formed by combining guar gum and a crosslinking agent), and / or at least one clay (such as montmorillonite, attapulgite, etc.), and / or at least one silicate.

[0099] By selecting a combination of matching weighting agents, dispersants, and suspending agents, the density of the liquid is made higher than the density of water, preferably more than twice the density of water. At the same time, within the designed maximum energy storage time, the weighting agent particles in the liquid do not completely settle to the bottom of the underground cavity, ground reservoir, or pressure vessel.

[0100] In some embodiments, the effects of the dispersant and the suspending agent are affected by the pH value of the liquid. It is necessary to add a pH regulator in the step of configuring the high-density liquid to adjust the pH value of the pressure-control liquid to the optimum. Common pH regulators include, but are not limited to: inorganic acids (such as hydrochloric acid, phosphoric acid, etc.), organic acids (such as citric acid, acetic acid, etc.), inorganic bases (such as sodium hydroxide, potassium hydroxide, sodium carbonate, etc.), organic bases (such as triethanolamine, sodium bicarbonate, etc.), and buffers (such as phosphates, acetates, carbonates, citrates, etc.).

[0101] In a specific embodiment, the weighting agent at least includes ilmenite powder, the dispersant at least includes sodium polycarboxylate and / or polycarboxylic acid ether, and the suspending agent at least includes bentonite or a combination of bentonite and xanthan gum to configure the high-density liquid. Herein, "at least includes" means that at least ilmenite powder is used as the weighting agent, at least sodium polycarboxylate and / or polycarboxylic acid ether is used as the dispersant, and at least bentonite or a combination of bentonite and xanthan gum is used as the suspending agent. That is, it can be only the aforementioned substance components, or it can also include other similar components on the premise of having the aforementioned substance components to form a further adjusted formula.

[0102] Among them, sodium polycarboxylate as the dispersant adsorbs on the surface of ilmenite particles to produce a steric hindrance effect and electrostatic repulsion, thereby preventing the aggregation of weighting agent particles due to van der Waals forces. In addition, the long side chains of polycarboxylic acid ether can form an adsorption layer on the surface of ore powder particles. When the ore powder particles approach each other, these adsorption layers will overlap, producing a steric hindrance effect and improving the dispersibility of the ore powder. And bentonite as the suspending agent adsorbs water molecules between layers when it meets water, and its volume can expand 10 - 15 times to form a three-dimensional network gel structure, thereby significantly increasing the viscosity of the system. When standing, a high-viscosity gel is formed to prevent particle settlement; when stirred, the fluidity is restored and the flow resistance is reduced. Xanthan gum provides high viscosity when standing; the viscosity decreases when stirred, facilitating pumping and can be compounded with bentonite to make up for the performance loss of bentonite in a high-salt environment.

[0103] As described above, by means of the synergistic effect of the dispersant and the suspending agent, while reducing the attraction between weighting agent particles and preventing the aggregation of weighting agent particles, the static viscosity of the liquid is increased and the settlement of weighting agent particles is prevented, thus forming a complementarity.

[0104] In a preferred embodiment, based on 1000 grams of the total liquid mass, the specific components are configured as follows: 600 - 750 grams of ilmenite powder, 200 - 400 grams of water matrix, 1 - 20 grams of sodium polycarboxylate and / or polycarboxylate ether, and 10 - 60 grams of bentonite or bentonite and xanthan gum. A small amount of sodium hydroxide is added externally to adjust the pH value to neutral. Specifically, the ilmenite powder is any value within the range of 600 - 750 including the endpoints, the water matrix is any value within the range of 200 - 400 including the endpoints, the sodium polycarboxylate and / or polycarboxylate ether is any value within the range of 1 - 20 including the endpoints, and the bentonite or bentonite and xanthan gum is any value within the range of 10 - 50 including the endpoints, as long as the total mass of the liquid after adding these components is 1000 grams.

[0105] In another preferred embodiment, the weighting agent at least includes barite powder, the dispersant at least includes sodium polycarboxylate and / or polycarboxylate ether, and the suspending agent at least includes bentonite or bentonite and xanthan gum to configure a high-density liquid. Among them, "at least includes" means that at least barite powder is used as the weighting agent, at least sodium polycarboxylate and / or polycarboxylate ether is used as the dispersant, and at least bentonite or bentonite and xanthan gum is used as the suspending agent, that is, it can be only the aforementioned substance components, or it can also include other similar components on the premise of having the aforementioned substance components to form a further adjusted formula.

[0106] Similarly, sodium polycarboxylate as a dispersant adsorbs on the surface of barite particles, generating a steric hindrance effect and electrostatic repulsion to prevent particle aggregation due to van der Waals forces. In addition, the long side chains of polycarboxylate ether can form an adsorption layer on the surface of ore powder particles used as the weighting agent. When the ore powder particles approach each other, these adsorption layers will overlap, generating a steric hindrance effect and improving the dispersibility of the ore powder. When bentonite encounters water, water molecules are adsorbed between its layers, and its volume can expand by 10 - 15 times, forming a three-dimensional network gel structure, thereby significantly increasing the viscosity of the system. A high-viscosity gel is formed during static settlement to prevent particle sedimentation; the fluidity is restored during stirring, reducing the flow resistance. Xanthan gum provides high viscosity during static settlement; the viscosity decreases during stirring, facilitating pumping and can be compounded with bentonite to make up for the performance loss of bentonite in a high-salt environment.

[0107] In a preferred embodiment, based on 1000 grams of the total liquid mass as a reference, the specific composition is as follows: barite is 600 - 800 grams, the water matrix is 150 - 300 grams, sodium polycarboxylate and / or polycarboxylate ether is 1 - 20 grams, bentonite or a mixture of bentonite and xanthan gum is 10 - 60 grams. A small amount of sodium hydroxide is added externally to adjust the pH value to 8 - 10, so as to enhance the negative charge on the surfaces of bentonite and barite, and cooperate with sodium polycarboxylate to improve the dispersion stability. Specifically, barite is any value within the range of 600 - 750 including the endpoints, the water matrix is any value within the range of 200 - 400 including the endpoints, sodium polycarboxylate and / or polycarboxylate ether is any value within the range of 1 - 20 including the endpoints, bentonite or a mixture of bentonite and xanthan gum is any value within the range of 10 - 60 including the endpoints, as long as the total liquid mass after adding these components is 1000 grams.

[0108] In some other embodiments, the weighting agent or dispersant can be a compound of multiple components. For example, the weighting agent can include a mixture of silicate and hematite, and the dispersant can include a mixture of clay and cellulose.

[0109] In some other embodiments, it is necessary to verify through experiments the effects of different combinations of weighting agents, dispersants and suspending agents on density increase and preventing the settlement of weighting agent particles, so as to determine the preferred combination.

[0110] Figure 2 The structural schematic diagram of the air compression energy storage system based on liquid pressure control disclosed in the second aspect of the present invention is shown. In combination Figure 2 As shown, the second aspect of the present invention discloses a system for implementing the air compression energy storage method based on liquid pressure control according to the first aspect of the present invention, which includes:

[0111] Gas delivery wellbore 1;

[0112] Liquid delivery wellbore 2, which is independent of the gas delivery wellbore 1;

[0113] Underground cavity 3, which is respectively connected to the gas delivery wellbore 1 and the liquid delivery wellbore 2, and can inject liquid for pressure control into the underground cavity 3 through the liquid delivery wellbore 2, so that both the liquid delivery wellbore 2 and the underground cavity 3 are filled with liquid for pressure control, wherein the liquid level of the liquid for pressure control in the underground cavity 3 is higher than the communication port between the liquid delivery wellbore 2 and the underground cavity 3;

[0114] Compressed air injection device 4, which injects compressed air into the gas delivery wellbore 1 and makes the compressed air enter the underground cavity 3, driving the liquid for pressure control in the underground cavity 3 to enter the liquid delivery wellbore 2 and be discharged through the liquid delivery wellbore 2 for energy storage;

[0115] Sealing device 5, used to seal the gas delivery wellbore 1;

[0116] A monitoring device for monitoring whether there is a power generation demand;

[0117] A power generation device 6 for generating electricity by means of the energy released from the compressed air discharged reversely from the gas transmission wellbore 1;

[0118] When no power generation demand is monitored, the wellhead of the gas transmission wellbore 1 is blocked by means of a blocking device 5 to maintain the compressed air pressure in the underground cavity 3; when a power generation demand is monitored, the power generation device 6 generates electricity by means of the energy released from the compressed air discharged reversely from the gas transmission wellbore 1, and at the same time, the pressure-control liquid returns to the underground cavity 3 through the liquid transmission wellbore 2.

[0119] A pressure vessel 7 is provided corresponding to the liquid transmission wellbore. Among them, the pressure vessel 7 can be provided corresponding to the wellhead of the liquid transmission wellbore. A weight 8 for maintaining pressure is arranged in the pressure vessel 7. By means of the weight 8, the pressure of the pressure-control liquid can be further increased, and further, the compressed air can have a higher pressure to force the pressure-control liquid to be discharged reversely, thereby further increasing the energy storage capacity of the underground cavity.

[0120] Figure 3 A broken line graph showing the change of the air pressure in the underground cavity 3 of traditional compressed air energy storage (non-liquid pressure control) and the air compression energy storage method based on liquid pressure control of the present invention is shown. Among them, broken line a is for air compression energy storage carried out by the method of the present invention, and the density of the pressure-control liquid used is ρ2; broken line b is for air compression energy storage carried out by the method of the present invention, and the density of the pressure-control liquid used is ρ1, where ρ2 > ρ1; broken line c is the broken line graph of the air pressure change in the underground cavity 3 of traditional compressed air energy storage. It can be seen from the figure that for traditional compressed air energy storage, when the volume of the underground cavity 3 remains unchanged, the air pressure in the underground cavity 3 fluctuates greatly during the energy storage and energy release periods. While for the air compression energy storage based on liquid pressure control, the pressure fluctuation is very small during the energy storage and energy release cycles. At the same time, by changing the density of the liquid injected into the underground cavity 3, a greater working pressure can be obtained, the energy storage density of the compressed air is increased, and the energy storage capacity is increased without changing the volume of the underground cavity 3.

[0121] For ease of description, spatial relative terms such as "above", "over", "on the upper surface", "upper", etc. may be used herein to describe the spatial positional relationship of one device or feature to other devices or features as shown in the figures. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, the device described as "above" or "over" other devices or structures will then be positioned "below" or "beneath" the other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations of the spatial relative descriptions used herein will be made.

[0122] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular forms are also intended to include the plural forms. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, they specify the presence of the features, steps, operations, devices, components, and / or combinations thereof.

[0123] It should be noted that the terms "first", "second", etc. in the description and claims of the present application and the above figures are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented, for example, in an order other than those illustrated or described herein. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0124] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. An air compression energy storage method based on liquid pressure control, characterized in that It includes the following steps: S1, respectively construct an independent gas delivery wellbore and a liquid delivery wellbore, and construct an underground cavity that is respectively connected to the gas delivery wellbore and the liquid delivery wellbore; S2, inject pressure-control liquid into the underground cavity through the liquid delivery wellbore, so that the underground cavity is filled with pressure-control liquid, wherein the liquid level of the pressure-control liquid in the underground cavity is higher than the connection port of the liquid delivery wellbore and the underground cavity; S3, inject compressed air into the gas delivery wellbore, and make the compressed air enter the underground cavity for energy storage; wherein the compressed air can drive the pressure-control liquid in the underground cavity to enter the liquid delivery wellbore from the underground cavity and be discharged back through the liquid delivery wellbore; S4, monitor whether there is a power generation demand. If not, block the gas delivery wellbore to maintain the compressed air pressure in the underground cavity; if so, discharge the compressed air from the gas delivery wellbore for energy release and power generation. At this time, the pressure-control liquid returns to the underground cavity through the liquid delivery wellbore.

2. The method according to claim 1, characterized in that Wherein the gas delivery wellbore and the liquid delivery wellbore can be set in a one-to-one, one-to-many, or many-to-many relationship.

3. The method according to claim 1, wherein The position of the connection port of the gas delivery wellbore and the underground cavity is higher than the position of the connection port of the liquid delivery wellbore and the underground cavity, or the bottom position of the gas delivery wellbore is higher than the bottom position of the liquid delivery wellbore, so that the liquid level of the pressure-control liquid can be lower than the connection port of the gas delivery wellbore and the underground cavity and higher than the connection port of the liquid delivery wellbore and the underground cavity.

4. The method according to claim 1, wherein Before step S2, it also includes the step of performing a sealing test on the underground cavity.

5. The method according to claim 1, characterized in that, The hydrostatic pressure of the pressure-control liquid in the underground cavity is configured to be less than the fracture pressure of the formation rock where the underground cavity is located; And / or, additional materials for maintaining sealing are provided on the inner wall of the underground cavity, and the hydrostatic pressure of the pressure-control liquid in the underground cavity is less than the fracture pressure of the additional materials on the inner wall of the underground cavity.

6. The method according to claim 1, characterized in that, A reservoir or a pressure vessel is provided corresponding to the liquid delivery wellbore. In step S2, when the initial filling is completed, the liquid level of the pressure-control liquid filled in the liquid delivery wellbore is in the reservoir or the pressure vessel, and its liquid level is higher than the liquid level position of the pressure-control liquid in the underground cavity; In step S3, the pressure-control liquid can be discharged back to the ground reservoir or pressure vessel through the liquid delivery wellbore; And, in step S3, monitor whether the liquid level in the reservoir or the height of the pressurizing substance in the pressure vessel reaches the liquid level threshold. If the preset liquid level threshold is reached, stop injecting compressed air into the underground cavity.

7. The method according to claim 6, wherein In step S4, the pressure-control liquid returns to the underground cavity through the liquid delivery wellbore by virtue of the energy given by its own gravitational potential energy or the combination of its own gravitational potential energy and the gravitational potential energy of the pressurizing substance.

8. The method according to claim 1, characterized in that, In step S3, monitor the pressure at the wellhead of the gas delivery wellbore and / or inside the gas delivery wellbore and / or in the underground cavity, and judge whether the pressure in the underground cavity reaches the preset pressure threshold; when it is judged that the preset pressure threshold is reached, stop injecting compressed air into the underground cavity.

9. The method according to any one of claims 1-8, characterized in that Before step S2, it also includes the step of configuring the density of the pressure-control liquid to be injected based on the depth of the underground cavity, which includes: Obtain the depth of the underground cavity constructed in step S1; Determine whether the depth of the underground cavity is less than a preset depth threshold; when the depth of the underground cavity is less than the preset depth threshold, configure the density of the pressure-control liquid to be greater than the density of water.

10. The method according to claim 9, wherein Add weighting agents with a particle size less than 200 microns and a density greater than that of water to the pressure-control liquid to configure the density of the pressure-control liquid to be greater than the density of water; wherein, the weighting agents include: at least one ceramsite, and / or at least one resin, and / or at least one quartz sand, and / or at least one barite, and / or at least one hematite, and / or at least one ilmenite, and / or at least one manganese ore, and / or at least one calcium carbonate, and / or at least one magnesium-aluminum-ferrite spinel, and / or at least one metal oxide, and / or at least one silicate, and / or at least one lead ore, and / or at least one fusible alloy.

11. The method according to claim 10, wherein In addition to adding weighting agents with a particle size less than 200 microns and a density greater than that of water to the pressure-control liquid, add a dispersant to the pressure-control liquid; the dispersant includes: At least one clay, and / or at least one silicate, and / or at least one lignosulfonate, and / or at least one polycarboxylate, and / or at least one humate, and / or at least one sulfonated polymer, and / or at least one phosphate, and / or at least one cellulose, and / or at least one polymer, and / or at least one oxide.

12. The method according to claim 11, wherein In addition to adding weighting agents with a particle size less than 200 microns and a density greater than that of water to the pressure-control liquid, add a suspending agent to the pressure-control liquid; the suspending agent includes: at least one natural polymer and its derivatives, and / or at least one cellulose and its derivatives, and / or at least one synthetic polymer, and / or at least one surfactant-type thickener, and / or at least one gel-type thickener, and / or at least one clay, and / or at least one silicate.

13. The method according to claim 12, wherein Based on the combined configuration of the weighting agent, dispersant and suspending agent, make the density of the pressure-control liquid more than twice the density of water, and within the set maximum energy storage time, the weighting agent particles in the liquid will not all settle to the bottom of the underground cavity or the reservoir or pressure vessel provided in the corresponding liquid delivery wellbore.

14. The method according to claim 13, wherein Wherein the weighting agent at least includes ilmenite powder, the dispersant at least includes sodium polycarboxylate and / or polycarboxylic acid ether, and the suspending agent at least includes bentonite or a combination of bentonite and xanthan gum to jointly configure the high-density liquid.

15. The method according to claim 14, wherein, Based on a total liquid mass of 1000 grams per unit, 600-750 grams of ilmenite powder is set, 200-400 grams of the water matrix is set, 1-20 grams of sodium polycarboxylate and / or polycarboxylic acid ether is set, and 10-60 grams of bentonite or a combination of bentonite and xanthan gum is set.

16. The method according to claim 13, wherein Wherein the weighting agent at least includes barite powder, the dispersant at least includes sodium polycarboxylate and / or polycarboxylic acid ether, and the suspending agent at least includes bentonite or a combination of bentonite and xanthan gum to jointly configure the high-density liquid.

17. The method according to claim 16, wherein Based on a total liquid mass of 1000 grams per unit, where barite powder is set to 600 - 800 grams, the water matrix is set to 150 - 300 grams, polycarboxylate sodium and / or polycarboxylate ether is set to 1 - 20 grams, and bentonite or bentonite and xanthan gum is 10 - 60 grams.

18. The method according to claim 9, wherein In the step of preparing the pressure - control liquid, it further includes: adding a pH regulator to the water matrix.

19. The method according to claim 18, characterized in that, The pH regulator includes: at least one inorganic acid, and / or at least one organic acid, and / or at least one inorganic base, and / or at least one organic base, and / or at least one buffer.

20. A system for implementing the air compression energy storage method based on liquid pressure control according to any one of claims 1-19, characterized in that, It includes: A gas - conveying wellbore; A liquid - conveying wellbore, which is independent of the gas - conveying wellbore; An underground cavity, which is respectively connected to the gas - conveying wellbore and the liquid - conveying wellbore, and can inject the pressure - control liquid into the underground cavity through the liquid - conveying wellbore, so that both the liquid - conveying wellbore and the underground cavity are filled with the pressure - control liquid, and the liquid level of the pressure - control liquid in the underground cavity is higher than the connection port between the liquid - conveying wellbore and the underground cavity; A compressed - air injection device, which injects compressed air into the gas - conveying wellbore and makes the compressed air enter the underground cavity, driving the pressure - control liquid in the underground cavity to enter the liquid - conveying wellbore and be discharged reversely through the liquid - conveying wellbore for energy storage; A plugging device for plugging the gas - conveying wellbore; A monitoring device for monitoring whether there is a power - generation demand; A power - generation device for generating electricity by means of the energy released from the compressed air discharged reversely from the gas - conveying wellbore; When no power - generation demand is monitored, the wellhead of the gas - conveying wellbore is plugged by the plugging device to maintain the compressed - air pressure in the underground cavity; when a power - generation demand is monitored, the power - generation device generates electricity by means of the energy released from the compressed air discharged reversely from the gas - conveying wellbore, and at the same time, the pressure - control liquid returns to the underground cavity through the liquid - conveying wellbore.

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