System and method for geological storage of carbon dioxide in limestone stratum using ph control

Abstract

The present invention provides a system for underground storage of carbon dioxide and an operation method thereof. The system comprises: an injection well for alternately injecting a pH adjustment solution and carbon dioxide to induce a carbonate mineralization reaction in a stratum; a production well for recovering a residual fluid that remains after the carbonate mineralization reaction in the stratum; a production fluid treatment device for separating at least one among carbonate particles, dissolved carbonate ions, and dissolved bicarbonate ions from the fluid recovered from the production well; and a control device for controlling operations of the injection well, the production well, and the production fluid treatment device.

Description

System and method for geological storage of carbon dioxide in limestone strata using pH control

[0001] The present invention relates to a carbon dioxide underground storage system and method. More specifically, the present invention relates to a system and method for efficiently storing carbon dioxide by utilizing limestone strata, which were not previously considered as targets for carbon dioxide underground storage.

[0002] Among the various technologies aimed at reducing greenhouse gases, the primary cause of global warming, Carbon Capture and Storage (CCS) technology is receiving significant attention. In particular, underground carbon storage technology has been recognized as a method capable of stably storing carbon dioxide on a large scale for extended periods.

[0003] Existing underground carbon dioxide storage technologies have primarily targeted depleted oil or gas reservoirs, deep saline aquifers, and coal seams, for the following reasons.

[0004] Depleted oil or gas reservoirs are geological layers that have already produced hydrocarbons; they are primarily composed of sedimentary rock and are considered favorable for carbon dioxide storage due to their high porosity and permeability. Deep saline aquifers are geological layers composed of porous rock located at depths of 800 meters or more; filled with brine within their pores, they provide a large capacity for carbon dioxide storage. In the case of coal seams, carbon dioxide is injected and stored into unmined coal seams, where it can be stored by adsorbing onto the coal.

[0005] However, existing storage target strata have limitations such as i) the actual amount of carbon dioxide that can be stored relative to the total pore volume is limited because a significant portion of the injected carbon dioxide is stored by replacing the fluid within the pores, ii) it is difficult to predict the long-term behavior of carbon dioxide within the strata when carbon dioxide is stored in a supercritical state and there is a possibility of carbon dioxide leakage, and iii) it is applicable only to regions with suitable geological structures, so economic feasibility decreases as the distance between the carbon dioxide source (capture source) and the storage area increases.

[0006] Meanwhile, limestone strata were generally not considered as targets for underground carbon dioxide storage for reasons such as i) having a generally dense structure which was considered disadvantageous for carbon dioxide injection and storage, ii) the fact that limestone itself is composed of calcium carbonate (CaCO3) which was thought to limit additional carbon dioxide storage capacity, and iii) the fact that the stability of the strata could be reduced as the limestone dissolves due to acidification that may occur during carbon dioxide injection.

[0007] Therefore, from the perspective of increasing the usability and scope of application of carbon dioxide underground storage technology, there is a need for a carbon dioxide underground storage system and method capable of efficiently and stably storing carbon dioxide using limestone strata.

[0008] According to one embodiment of the present invention, a carbon dioxide underground storage system capable of stably storing carbon dioxide by utilizing the characteristics of a limestone stratum can be provided.

[0009] According to another embodiment of the present invention, a method of operating the carbon dioxide underground storage system may be provided.

[0010] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0011] According to one embodiment of the present invention, a carbon dioxide underground storage system is provided, comprising: an injection well that induces a carbonate mineralization reaction in a geological layer by alternately injecting a pH adjustment solution and carbon dioxide; a production well that recovers a fluid remaining after the carbonate mineralization reaction in the geological layer; a production fluid treatment device that separates at least one of carbonate particles, dissolved carbonate ions, and bicarbonate ions from the fluid recovered from the production well; and a control device that controls the operation of the injection well, the production well, and the production fluid treatment device.

[0012] The above pH adjustment solution may be a mixture of an aqueous solution of PIPES (1,4-Piperazine diethanesulfonic acid) and water of ammonia (NH4OH) mixed in a volume ratio of 3:1 to 1:1.

[0013] The concentration of PIPES in the above PIPES aqueous solution may be 0.1M to 0.5M.

[0014] The concentration of ammonia in the above ammonia solution may be 0.1M to 0.3M.

[0015] The above-mentioned production fluid treatment device may include one or more selected from the group consisting of nanofiltration membranes, ion exchange resins, and electrodialysis devices.

[0016] The above-described production fluid processing device may further include a dryer for drying carbonates and a grinder for grinding carbonates.

[0017] The above control device may include one or more selected from the group consisting of a pH sensor, a pressure sensor, and a carbon dioxide concentration sensor.

[0018] The injection well is installed in a geological layer with a depth of 1,000 to 2,000 m, and the production well is installed at a depth of 50 to 100 m relative to the location where the injection well is installed, and the horizontal distance between the location where the injection well and the production well are installed may be 500 to 1,000 m.

[0019] According to another embodiment of the present invention, a method for operating a carbon dioxide underground storage system according to one embodiment of the present invention is provided, comprising: a step S1 of injecting a pH control solution into a geological layer; a step S2 of injecting carbon dioxide into the geological layer to induce a carbonate mineralization reaction within the geological layer; a step S3 of recovering a fluid remaining after the carbonate mineralization reaction; a step S4 of separating at least one of carbonate particles, dissolved carbonate ions, and bicarbonate ions from the recovered fluid; and a step S5 of controlling at least one condition selected from the group consisting of pH, pressure, and carbon dioxide concentration of the fluid within the geological layer.

[0020] The above S5 step includes a step of controlling the pH of the fluid within the stratum, and the step of controlling the pH is:

[0021] (i) a step of measuring the pH of the fluid within the strata;

[0022] (ii) includes a step of adjusting the pH when the measured pH falls outside a predetermined pH range, and

[0023] The above (ii) step is:

[0024] (ii-a) a step of reducing the proportion of ammonia water in the pH adjustment solution when the measured pH exceeds a predetermined upper threshold; and

[0025] (ii-b) If the measured pH is below a predetermined lower threshold, the step of increasing the proportion of ammonia water in the pH adjustment solution may be included.

[0026] According to one embodiment of the present invention, the underground carbon dioxide storage system and the method of operation thereof can stably store carbon dioxide by making maximum use of the characteristics of limestone strata, which were previously considered unsuitable for carbon dioxide storage.

[0027] In addition, since carbonate particles recovered during the carbon dioxide storage process can be utilized in construction materials, the paper industry, and other sectors, a portion of the carbon dioxide storage costs can be offset.

[0028] FIG. 1 is a schematic diagram showing a carbon dioxide underground storage system according to one embodiment of the present invention.

[0029] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0030] In addition, embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0031] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0032] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0033] FIG. 1 is a schematic diagram showing a carbon dioxide underground storage system according to one embodiment of the present invention.

[0034] Referring to FIG. 1, a carbon dioxide underground storage system according to one embodiment of the present invention comprises: an injection well that induces a carbonate mineralization reaction in a geological layer by alternately injecting a pH-regulating solution and carbon dioxide; a production well that recovers a fluid remaining after the carbonate mineralization reaction in the geological layer; a production fluid treatment device that separates at least one of carbonate particles, dissolved carbonate ions, and bicarbonate ions from the fluid recovered from the production well; and a control device that controls the operation of the injection well, the production well, and the production fluid treatment device.

[0035] In one embodiment, the injection well may inject a pH adjustment solution, and the pH adjustment solution may be a mixture of an aqueous solution of PIPES (1,4-Piperazinediethanesulfonic acid) and water of ammonia (NH4OH). The pH adjustment solution may be prepared in a production fluid treatment device as described below.

[0036] The above-mentioned PIPES forms very little complex with metal ions, resulting in a low possibility of adverse effects in limestone strata, and has low reactivity with limestone, minimizing the possibility of structural changes in the strata. Therefore, when using a pH-adjusting solution containing the above-mentioned PIPES, carbon dioxide can be stored efficiently and stably in limestone strata.

[0037] In detail, the pH adjusting solution may be a mixture of an aqueous PIPES solution and water ammonia in a volume ratio of 3:1 to 1:1, more specifically, an aqueous PIPES solution and water ammonia in a volume ratio of 2:1.

[0038] At this time, the concentration of PIPES in the PIPES aqueous solution may be 0.1M to 0.5M, and more specifically, 0.2M. In addition, the concentration of ammonia in the ammonia water may be 0.1M to 0.3M, and more specifically, 0.2M.

[0039] When the concentration of PIPES, the concentration of ammonia, and the mixing ratio of the PIPES aqueous solution and the ammonia water fall within the ranges described above, the buffering capacity of the pH adjustment solution can be optimized, and the solubility of carbon dioxide can be increased to promote carbonate formation.

[0040] The pH of the above pH adjusting solution may be 6 to 9, and more specifically, 7 to 8. When the pH of the above pH adjusting solution falls within the range described above, the solubility of carbon dioxide increases, and carbonate formation may be promoted.

[0041] In addition, the injection well can inject carbon dioxide into the geological layer into which the pH adjustment solution has been injected, and the carbon dioxide may be supercritical carbon dioxide at a temperature of 30 to 35°C and a pressure of 70 to 75 bar.

[0042] Regarding the injection rate and injection time of the above pH adjustment solution and carbon dioxide, the operation method of the carbon dioxide underground storage system will be described later.

[0043] The injection well can alternately inject a pH adjustment solution and carbon dioxide. Specifically, the injection well can be designed to have a double-tube structure in which two tubes share a central axis and are spaced apart from each other. Accordingly, the injection well can inject the pH adjustment solution and carbon dioxide separately.

[0044] The injection well may be installed within a geological layer where limestone is present. For example, the injection well may be installed within a geological layer at a depth of 1,000 to 2,000 m, more specifically, within a geological layer at a depth of 1,500 to 2,000 m. When the injection well is installed within the above depth range, the temperature within the geological layer at the depth is approximately 40 to 70°C and the pressure is approximately 100 to 200 bar, so carbon dioxide can exist in a supercritical state, and since carbon dioxide in a supercritical state has a high density, a large amount of carbon dioxide can be stored per unit volume. In addition, under the high-pressure conditions at the above depth, the storage efficiency in the form of dissolved carbon dioxide is higher, so the mineralization reaction can be promoted.

[0045] As a pH adjustment solution and carbon dioxide are injected through the injection well, a carbonate mineralization reaction according to the following reaction formulas 1 to 3 may occur within the stratum where the limestone is present.

[0046] [Reaction Equation 1]

[0047] H2CO3 → H + + HCO3 -

[0048] [Reaction Equation 2]

[0049] HCO3 - → H + + CO3 2-

[0050] [Reaction Equation 3]

[0051] CaCO 3(s) ↔ Ca 2+ + CO3 2-

[0052] In one embodiment, the production well may be installed at a deeper depth than the injection well to utilize the gravity effect. For example, the production well may be installed at a depth of 50 to 100 m relative to the location where the injection well is installed, more specifically at a depth of 80 to 100 m. When the production well is installed within the depth range, the injected pH-regulating solution and carbon dioxide diffuse evenly from the shallow to the deep side, thereby allowing the carbonate mineralization reaction to be induced by utilizing the limestone layer extensively.

[0053] Meanwhile, the horizontal distance between the locations where the injection well and the production well are installed may be 500 to 1000 m, and more specifically, 700 to 800 m. When the horizontal distance between the locations where the injection well and the production well are installed is within the above range, sufficient time can be secured for the pH adjustment solution and carbon dioxide injected by the injection well to perform pH adjustment and carbonation reactions. In addition, an appropriate pressure gradient can be formed between the injection well and the production well, allowing for efficient injection of carbon dioxide and recovery of fluid, and since excessive injection pressure is not required, the risk of stratum fracture can be minimized.

[0054] The above production well can recover the fluid remaining after the carbonate mineralization reaction within the geological layer and supply it to a production fluid treatment device. The above production well may further include a filter at the bottom to prevent the inflow of unnecessary mineral particles, etc., during the fluid recovery process. Meanwhile, regarding the fluid recovery speed and time of the above production well, it will be described later in relation to the operation method of the carbon dioxide underground storage system.

[0055] In one embodiment, the production fluid treatment device may include one or more of a centrifuge and a sedimentation tank. Accordingly, the production fluid treatment device can separate carbonate particles from the fluid recovered by the production well, i.e., the 'production fluid'. The carbonate may be one or more selected from the group consisting of potassium carbonate (K2CO3), calcium carbonate (CaCO3), and sodium carbonate (Na2CO3).

[0056] In addition, the production fluid treatment device may include one or more selected from the group consisting of nanofiltration membranes, ion exchange resins, and electrodialysis devices. Accordingly, the production fluid treatment device removes dissolved carbonate ions (CO3) from the production fluid 2- ) and bicarbonate ions (HCO3 - ) can be separated.

[0057] In one embodiment, the production fluid treatment device is dissolved carbonate ions (CO3 2- ) and bicarbonate ions (HCO3 - A pH adjustment solution can be prepared by readjusting the concentration of PIPES, the concentration of ammonia, and the pH of the fluid from which ) has been removed. The prepared pH adjustment solution can be injected back into the geological layer through the injection well.

[0058] Meanwhile, the above-mentioned production fluid processing device may additionally include a dryer and a grinder. Accordingly, the above-mentioned production fluid processing device can dry and grind the separated carbonate particles to process them into a form usable in other industries, such as construction materials and the paper industry.

[0059] The above control device may include one or more selected from the group consisting of a pH sensor, a pressure sensor, and a carbon dioxide concentration sensor. Accordingly, a carbon dioxide underground storage system according to one embodiment of the present invention can measure one or more selected from the group consisting of pH, pressure, and carbon dioxide concentration of a fluid in a geological layer in real time.

[0060] The above control device can control the pH, pressure, and carbon dioxide concentration of the fluid within the geological layer to within a predetermined range.

[0061] For example, if the pH of the fluid in the layer measured by the pH sensor exceeds a predetermined upper threshold, the control device can transmit a control signal (CS1) to the production fluid processing device to reduce the proportion of ammonia water in the pH adjustment solution. Additionally, if the pH of the fluid in the layer measured by the pH sensor is below a predetermined lower threshold, the control device can transmit a control signal (CS2) to the production fluid processing device to increase the proportion of ammonia water in the pH adjustment solution.

[0062] The pH range of the fluid in the above-mentioned layer can be set within the range of 6 to 9, and more specifically, within the range of 7 to 8. When the pH of the fluid in the above-mentioned layer falls within the aforementioned range, the solubility of carbon dioxide increases, which can promote the formation of carbonates.

[0063] When the pressure of the fluid in the layer measured by the pressure sensor exceeds a predetermined upper threshold, the control device can 1) transmit a control signal (CS3) to the injection well to reduce the injection rate of the pH control solution and carbon dioxide, and 2) also transmit a control signal (CS4) to the production well to increase the recovery rate of the fluid.

[0064] In addition, if the pressure of the fluid in the layer measured by the pressure sensor is below a predetermined lower threshold value, the control device can 1) transmit a control signal (CS5) to the injection well to increase the injection amount of pH control solution and carbon dioxide, and 2) also transmit a control signal (CS6) to the production well to decrease the fluid recovery rate.

[0065] The pressure range of the fluid within the above-mentioned stratum can be determined within a range of 50 to 80% of the fracture pressure of the stratum, and more specifically, within a range of 70 to 80% of the fracture pressure of the stratum.

[0066] When the pressure of the fluid within the stratum falls within the above range, the maximum amount of carbon dioxide can be injected without compromising the stability of the stratum.

[0067] If the carbon dioxide concentration of the fluid in the layer measured by the carbon dioxide concentration sensor exceeds a predetermined upper threshold, the control device can reduce the amount of carbon dioxide injected by transmitting a control signal (CS7) to the injection well. Additionally, if the carbon dioxide concentration of the fluid in the layer measured by the carbon dioxide concentration sensor is below a predetermined lower threshold, the control device can increase the amount of carbon dioxide injected by transmitting a control signal (CS8) to the injection well.

[0068] A method for operating a carbon dioxide underground storage system according to another embodiment of the present invention comprises the steps of: injecting a pH control solution into a geological layer (S1); injecting carbon dioxide into the geological layer to induce a carbonate mineralization reaction within the geological layer (S2); recovering a fluid remaining after the carbonate mineralization reaction (S3); separating at least one of carbonate particles, dissolved carbonate ions, and bicarbonate ions from the recovered fluid (S4); and controlling at least one condition selected from the group consisting of pH, pressure, and carbon dioxide concentration of the fluid within the geological layer (S5).

[0069] In the above S1 step, a pH adjustment solution may be injected into the geological layer, and the pH adjustment solution may be a mixture of an aqueous solution of PIPES (1,4-Piperazinediethanesulfonic acid) and water of ammonia (NH4OH). Since the pH adjustment solution has already been described above in relation to a carbon dioxide underground storage system according to one embodiment of the present invention, a description thereof will be omitted below.

[0070] Meanwhile, the injection of the pH adjustment solution may be performed in stages. Specifically, step S1 may include the following steps i) and ii):

[0071] i) A step of increasing the porosity of the limestone layer by dissolving a portion of the limestone through the injection of a weak acid with a pH of 5 to 6.

[0072] ii) Step of injecting a pH adjusting solution of pH 7 to 8

[0073] According to step i) above, the porosity of the limestone layer before carbon dioxide injection can be increased, and according to step ii) above, the fluid within the layer becomes slightly alkaline, which increases the solubility of carbon dioxide, thus allowing carbon dioxide to be stored more efficiently.

[0074] In the above S1 step, the injection pressure of the pH adjustment solution may be maintained at 80% or less of the fracture pressure of the stratum. For example, the injection pressure of the pH adjustment solution may be 50 to 80% of the fracture pressure of the stratum, and more specifically, 70 to 80% of the fracture pressure of the stratum.

[0075] When the injection pressure of the above pH adjustment solution falls within the above range, the maximum amount of carbon dioxide can be injected without compromising the stability of the geological layer.

[0076] In the above S1 step, the injection rate and injection time of the pH adjustment solution are not specifically limited. For example, the injection rate of the pH adjustment solution may be 100 to 500 m³ / h, and the injection time may be 12 to 24 hours.

[0077] In the above S2 step, the carbon dioxide may be supercritical carbon dioxide at a temperature of 30 to 35°C and a pressure of 70 to 75 bar.

[0078] The injection rate of the carbon dioxide above may be 1,000 to 5,000 ton / day, but is not limited thereto, and can be adjusted according to the amount of limestone in the stratum.

[0079] In the above S2 step, the injection rate and injection time of the carbon dioxide are not specifically limited. For example, the injection rate of the carbon dioxide may be 1,000 to 5,000 ton / day, and the injection time may be 12 to 24 hours.

[0080] After injecting carbon dioxide according to the above S2 step and allowing sufficient time for the carbonate mineralization reaction to occur, for example, 24 to 72 hours after the step of injecting carbon dioxide into the strata, the S3 step of recovering the remaining fluid can be performed.

[0081] In the above S3 step, the recovery rate and recovery time of the residual fluid are not specifically limited. For example, the recovery rate of the residual fluid may be 50 to 200 m³ / h, and the injection time may be 12 to 24 hours.

[0082] The above S4 step can separate at least one of carbonate particles, dissolved carbonate ions, and bicarbonate ions from the recovered fluid.

[0083] In step S4 above, carbonate particles may be separated from the recovered fluid through one or more methods of centrifugation and sedimentation. The carbonate may be one or more selected from the group consisting of potassium carbonate (K2CO3), calcium carbonate (CaCO3), and sodium carbonate (Na2CO3).

[0084] In the above S4 step, dissolved carbonate ions (CO3) from the recovered fluid are obtained through one or more methods selected from the group consisting of nanofiltration, ion exchange, and electrodialysis. 2- ) and bicarbonate ions (HCO3 - ) can be separated. The above nanofiltration, ion exchange, and electrodialysis may use known methods.

[0085] For example, the nanofiltration described above may be performed using a nanofiltration membrane under conditions of a pressure of 10 to 15 bar and a temperature of 25 to 30°C, but is not limited thereto.

[0086] The above ion exchange can be performed by using a strong basic anion exchange resin to adsorb carbonate ions and bicarbonate ions, and then regenerating with a sodium chloride solution to recover them in a concentrated form.

[0087] This can be done by alternately arranging cation exchange membranes and anion exchange membranes and applying an electric field to separate and concentrate the ions.

[0088] In the above S5 step, one or more conditions selected from the group consisting of pH, pressure, and carbon dioxide concentration can be controlled.

[0089] In detail, the above S5 step may include a step of controlling the pH of the fluid within the stratum.

[0090] The step of controlling the above pH is:

[0091] (i) a step of measuring the pH of the fluid within the strata;

[0092] (ii) includes a step of adjusting the pH when the measured pH falls outside a predetermined pH range, and

[0093] The above (ii) step is:

[0094] (ii-a) a step of reducing the proportion of ammonia water in the pH control solution in step S1 when the measured pH exceeds a predetermined upper threshold; and

[0095] (ii-b) If the measured pH is below a predetermined lower threshold, step S1 may include a step of increasing the proportion of ammonia water in the pH adjustment solution.

[0096] The above S5 step may include a step of controlling the pressure of the fluid within the stratum.

[0097] The step of controlling the above pressure is:

[0098] (i) A step of measuring the pressure of the fluid within the strata;

[0099] (ii) includes a step of adjusting the pressure when the measured pressure falls outside a predetermined pressure range,

[0100] The above (ii) step is:

[0101] (ii-a) a step of reducing the injection amount of pH adjustment solution and carbon dioxide in steps S1 and S2 when the measured pressure exceeds a predetermined upper threshold; and

[0102] (ii-b) If the measured pressure is below a predetermined lower threshold, steps S1 and S2 may include increasing the amount of pH adjustment solution and carbon dioxide injected.

[0103] The above S5 step may include a step of controlling the carbon dioxide concentration of the fluid within the stratum.

[0104] The step of controlling the carbon dioxide concentration above is:

[0105] (i) a step of measuring the carbon dioxide concentration of the fluid within the geological layer;

[0106] (ii) includes a step of adjusting the carbon dioxide concentration when the measured carbon dioxide concentration falls outside a predetermined range of carbon dioxide concentrations, and

[0107] The above (ii) step is:

[0108] (ii-a) a step of reducing the amount of carbon dioxide injected in step S2 when the measured carbon dioxide concentration exceeds a predetermined upper threshold; and

[0109] (ii-b) If the measured carbon dioxide concentration is below a predetermined lower threshold, step S2 may include increasing the amount of carbon dioxide injected.

[0110] One or more of the above pH, pressure, and carbon dioxide concentration measurements may be performed in real time, for example, at intervals of 5 to 15 minutes. However, the measurement intervals for the above pH, pressure, or carbon dioxide concentration are not limited thereto.

[0111] As described above, according to one embodiment of the present invention, a carbon dioxide underground storage system and method capable of efficiently and stably storing carbon dioxide using a limestone layer can be provided.

[0112] Although an embodiment of the present disclosure has been described in detail above, this is merely illustrative, and other configurations may be included without departing from the scope of the present disclosure. Those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present disclosure should be determined by the technical spirit of the appended claims.

[0113] [Explanation of the symbol]

[0114] 10: Carbon Dioxide Underground Storage System

[0115] 100: Injection tablet

[0116] 200: Production well

[0117] 300: Production fluid handling unit

[0118] 400: Control unit

Claims

1. An injection well that induces a carbonate mineralization reaction within the geological layer by alternately injecting a pH-regulating solution and carbon dioxide; A production well for recovering fluid remaining after the carbonate mineralization reaction within the above-mentioned stratum; A production fluid treatment device for separating at least one of carbonate particles, dissolved carbonate ions, and bicarbonate ions from the fluid recovered from the above production well; and A carbon dioxide underground storage system comprising a control device that controls the operation of the injection well, production well, and production fluid processing device.

2. In claim 1, the pH adjusting solution is a mixture of an aqueous solution of PIPES (1,4-Piperazinediethanesulfonic acid) and water of ammonia (NH4OH) mixed in a volume ratio of 3:1 to 1:1, and The concentration of PIPES in the above PIPES aqueous solution is 0.1M to 0.5M, and A carbon dioxide underground storage system in which the concentration of ammonia in the above ammonia solution is 0.1M to 0.3M.

3. A carbon dioxide underground storage system according to claim 1, wherein the production fluid treatment device comprises one or more selected from the group consisting of a nanofiltration membrane, an ion exchange resin, and an electrodialysis device.

4. A carbon dioxide underground storage system according to claim 1, wherein the production fluid processing device further comprises a dryer for drying carbonates and a grinder for grinding carbonates.

5. A carbon dioxide underground storage system according to claim 1, wherein the control device comprises one or more types selected from the group consisting of a pH sensor, a pressure sensor, and a carbon dioxide concentration sensor.

6. In paragraph 1, the injection well is installed in a geological layer with a depth of 1,000 to 2,000 m, and A carbon dioxide underground storage system in which the production well is installed at a depth of 50 to 100 m relative to the location where the injection well is installed, and the horizontal distance between the location where the injection well and the production well are installed is 500 to 1000 m.

7. A method of operating a carbon dioxide underground storage system according to any one of paragraphs 1 to 6, Step S1 of injecting a pH adjustment solution into the stratum; Step S2, in which carbon dioxide is injected into the above stratum to induce a carbonate mineralization reaction within the stratum; Step S3 for recovering the fluid remaining after the above carbonate mineralization reaction; Step S4 of separating at least one of carbonate particles, dissolved carbonate ions, and bicarbonate ions from the recovered fluid; and A method for operating a carbon dioxide underground storage system, comprising step S5 of controlling one or more conditions selected from the group consisting of pH, pressure, and carbon dioxide concentration of a fluid within a geological layer.

8. In claim 7, the pH adjusting solution is a mixture of an aqueous PIPES solution and water ammonia mixed in a volume ratio of 3:1 to 1:1, and The concentration of PIPES in the above PIPES aqueous solution is 0.1M to 0.5M, and A method of operating a carbon dioxide underground storage system, wherein the concentration of ammonia in the above ammonia solution is 0.1M to 0.3M.

9. In claim 8, the above S5 step includes a step of controlling the pH of a fluid within the stratum, and the step of controlling the pH is: (i) a step of measuring the pH of the fluid within the strata; (ii) includes a step of adjusting the pH when the measured pH falls outside a predetermined pH range, and The above (ii) step is: (ii-a) a step of reducing the proportion of ammonia water in the pH adjustment solution when the measured pH exceeds a predetermined upper threshold; and (ii-b) A method of operating a carbon dioxide underground storage system comprising the step of increasing the proportion of ammonia water in the pH control solution when the measured pH is below a predetermined lower threshold value.

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