Composite buffering and targeted synergistic basalt stratum efficient carbon mineralization method
By combining acidic and alkaline buffer solutions with supercritical CO2 fluid and controlling the pH value in stages, the problems of low reaction efficiency and heterogeneity in CO2 mineralization of basalt formations were solved, achieving efficient and controllable CO2 sequestration.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-04-10
AI Technical Summary
In existing CO2 mineralization technologies for basalt formations, pH balance is difficult to control, resulting in low reaction efficiency. Furthermore, there is a lack of feasible pH control methods, making it difficult to adapt to heterogeneous reservoirs and solve the spatiotemporal matching problem between cation enrichment during the dissolution stage and carbonate supply during the precipitation stage.
An acidic targeted buffer solution was mixed with supercritical CO2 fluid to acidify and dissolve silicate minerals. Subsequently, an alkaline catalytic buffer solution was injected to generate carbonate minerals. The pH value was controlled in stages by combining a targeted complexing agent and a biomimetic catalyst, and the reaction process was optimized through real-time monitoring and an intelligent injection system.
It significantly improves the carbon mineralization rate, shortens the storage cycle, and increases storage efficiency by more than 30%. It solves the problem of mineralization differences in heterogeneous reservoirs, avoids pore blockage, and achieves efficient and controllable CO2 storage.
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Figure CN121823583A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of CO2 geological storage technology, specifically a method for efficient carbon mineralization of basalt formations with composite buffering and targeted enhancement. Background Technology
[0002] Geological CO2 sequestration is currently recognized internationally as one of the important pathways to carbon neutrality. In-situ carbon mineralization in basalt formations can rapidly convert CO2 into stable carbonate minerals, offering advantages such as high safety, good stability, and large sequestration capacity. It is a carbon sequestration technology with great application potential. Its core principle is the reaction of CO2 with active minerals in basalt containing calcium, magnesium, and iron to form carbonate precipitates. Currently, the mainstream basalt CO2 mineralization technology involves directly injecting supercritical CO2 into aquifers or dry basalt reservoirs, or injecting a mixture of CO2 and water into the reservoir. This relies on the reservoir's own mineral composition and pore water, allowing CO2 to dissolve, diffuse, and react with active minerals in basalt containing calcium, magnesium, and iron (such as olivine, pyroxene, and plagioclase) in a water-rock reaction. The reaction process is typically described as follows: CO2 dissolves in water to form carbonic acid, acidifying the environment (pH 3-5) and dissolving cation-containing silicate minerals; as the reaction proceeds, the pH may slowly rise, and the dissolved cations combine with carbonate / bicarbonate ions to form carbonate precipitates (calcite, dolomite, siderite). The entire process involves no active intervention from external chemical reagents and relies on the natural geochemical processes of the strata.
[0003] However, this method currently faces a technical bottleneck: the pH balance in the reaction system is difficult to control. Low pH can promote mineral dissolution but inhibit precipitation, while high pH is conducive to precipitation but limits early dissolution. Naturally, the pH cannot accurately match the kinetic requirements of the two stages in the reaction, resulting in low mineralization efficiency.
[0004] To address this deficiency, existing research has proposed a two-step artificial pH control approach. For example, Li Wanlun et al. (2022) mentioned that pH is the most important reaction parameter in the CO2 sequestration process. If pH could be controlled, the dissolution of silicate minerals and the precipitation of carbonate minerals should be achieved in two steps, respectively. If this approach could be implemented, it would be more efficient and controllable than relying on natural processes. However, to date, there is still no concrete method for implementing this approach. The main reasons for this are as follows: 1) Supercritical CO2 systems are typically operated under high temperature and high pressure (e.g., 90-120℃, 20-30MPa). Their unique physicochemical properties make conventional pH control methods difficult to apply and maintain the target pH window stably over long periods. For example, in the supercritical state, CO2 is both the reaction medium and a pH influencing factor. Simply adjusting its partial pressure will simultaneously alter the system's solubility and phase behavior, making independent and precise pH control difficult. Furthermore, in high-temperature and high-pressure supercritical CO2 environments, the solubility and reactivity of many solid buffers are significantly reduced, making dispersion and dissolution difficult, resulting in weak buffering effects and slow responses. The high-pressure and high-temperature environment poses a challenge to the stability and lifespan of pH electrodes, and frequent injection of liquid reagents can easily cause drastic fluctuations in system composition and phase state, affecting process continuity and stability. 2) Lack of coordinated design of "pH regulation-reaction kinetics-formation characteristics" and the difference in active mineral content in different regions of the formation make it difficult to adapt to the heterogeneity of basalt reservoirs by simply controlling pH in two steps. 3) The problem of temporal and spatial matching between "cation enrichment in the dissolution stage" and "carbonate supply in the precipitation stage" has not been solved, and conventional solutions are prone to insufficient ion supply or pore blockage.
[0005] In summary, there is an urgent need for a low-cost, efficient, controllable, and artificially intervened method for carbon mineralization of basalt formations, which can overcome the inherent limitations of natural mineralization by using a precise, stable, and formation-adaptive pH control system. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite buffering and targeted enhancement method for efficient carbon mineralization of basalt formations, so as to achieve at least the effects of low cost, precision and stability, and high efficiency and controllability.
[0007] The objective of this invention is achieved through the following technical solution: A method for carbon mineralization of basalt strata includes the following steps: S1: Mix acidic target buffer and supercritical CO2 fluid and inject into the target basalt reservoir to acidify and dissolve silicate minerals; S2: Inject alkaline catalytic buffer solution into the target basalt reservoir to generate and precipitate carbonate minerals; The acidic targeting buffer solution includes an acidic buffer solution and a targeting complexing agent; The alkaline catalytic buffer solution includes an alkaline buffer solution and a CO2 biomimetic catalyst.
[0008] In some embodiments, the acidic buffer solution comprises a sodium citrate-citric acid buffer solution; the targeting complexing agent comprises gluconate.
[0009] In some instances, the weight ratio of the sodium citrate-citric acid buffer solution to the gluconate is 1:10~20; the pH of the acidic targeting buffer solution is controlled by adjusting the ratio of sodium citrate to citric acid.
[0010] In some embodiments, the alkaline buffer solution comprises a sodium bicarbonate-sodium carbonate buffer solution; the CO2 biomimetic catalyst comprises a carbonic anhydrase biomimetic catalyst.
[0011] In some instances, the weight ratio of the sodium bicarbonate-sodium carbonate buffer solution to the carbonic anhydrase biomimetic catalyst is 90-95:5-10; the pH of the alkaline catalytic buffer solution is controlled by adjusting the ratio of sodium bicarbonate to sodium carbonate.
[0012] It is worth noting that in this invention, gluconate can protect the stability and effectiveness of the citrate buffer pair, and can also efficiently release the target metal cation Ca² from basalt minerals through selective complexation reactions. + Mg² + This greatly improves the efficiency and selectivity of the dissolution stage; while the role of the micro-carbonic anhydrase biomimetic catalyst is to accelerate the conversion of bicarbonate to carbonate during the carbonate precipitation stage, thereby significantly improving the nucleation and growth of carbonate minerals and solving the kinetic bottleneck of the precipitation stage.
[0013] In some embodiments, the duration of acidification and dissolution of the silicate minerals is controlled to be T1, where T1 is 5 to 20 days, and the duration of formation and precipitation of the carbonate minerals is controlled to be T2, where T2 is 5 to 40 days. T1:T2 = 1:1~2.
[0014] In some embodiments, prior to step S1, the following steps are also included: S0: Samples are taken from the target basalt reservoir, and the content of active minerals is determined by XRD. The target basalt is then divided into zones based on the determined relative mineral content. The pH values of the acidic targeting buffer and the alkaline catalytic buffer are adjusted according to the partition, and T1 and T2 are adjusted according to the content of active minerals.
[0015] In some instances, the active minerals include pyroxene and anorthite; the partitioning includes high-calcium zones, high-magnesium zones, and low-activity zones; The high-calcium zone is defined as the region in which the whole-rock mineral composition contains an anorthite content of 8% or more. The high-magnesium zone is defined as the area in which the whole-rock mineral composition contains pyroxene content greater than or equal to 3% and anorthite content less than 8%. The low-activity zone is defined as the area where the content of anorthite is less than 8% and the content of pyroxene is less than 3%.
[0016] In some examples, when the partition is the high-calcium zone, the pH of the acidic targeting buffer is controlled to 3.8-4.5, T1 is controlled to 5 days, the pH of the alkaline catalytic buffer is controlled to 7.5-8.2, and T2 is controlled to 5 days; When the partition is the high magnesium region, the pH of the acidic targeting buffer is controlled at 4.5~5.2, T1 is controlled at 6 days, the pH of the alkaline catalytic buffer is controlled at 7.5~8.2, and T2 is controlled at 6 days; when the partition is the low activity region, it is not used as a carbon mineralization target layer.
[0017] In some embodiments, the carbon mineralization method further includes the following steps: The pH, pressure, temperature, and ion concentration of the target basalt reservoir are monitored in real time; the injection concentration and injection rate of the acidic targeting buffer and the alkaline catalytic buffer are dynamically adjusted based on the monitoring results.
[0018] The beneficial effects of this invention are: 1. This invention provides a feasible two-step pH-controlled basalt CO2 mineralization technology, overcoming the bottleneck of pH-dependent carbon mineralization reactions in supercritical CO2 systems under natural conditions. Specifically, the enhanced buffer system combining a buffer solution and a targeted synergist solves the problem of pH control failure under supercritical conditions, increasing the overall carbon mineralization rate by more than four times compared to natural reaction conditions, and significantly shortening the storage period.
[0019] 2. This invention avoids the mineralization differences in heterogeneous reservoirs through formation pretreatment and zonal regulation. The strategy of "acid dissolution to expand pores first, followed by alkali precipitation" achieves a spatiotemporal match between ion supply and precipitation demand. This avoids pore blockage caused by premature precipitation, allowing more CO2 to enter the deep reservoir and be converted into carbonates. Simulation verification shows that the sequestration efficiency (the amount of CO2 sequestered per unit volume of rock) can be improved by more than 30%.
[0020] 3. This invention integrates active regulation, real-time monitoring, and intelligent injection systems to form a predictable, optimizable, and controllable intelligent sealing process, providing a reliable technical path for large-scale engineering applications. Attached Figure Description
[0021] Figure 1 This refers to the detection results of fluid ion concentration in the experimental examples of this invention; Figure 2 This is a comparison result of mineralization amount in the experimental examples of this invention. Detailed Implementation
[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.
[0023] Example 1 This embodiment provides a carbon mineralization method for basalt formations (highly active basalt reservoirs, with anorthite + pyroxene content ≥40%), the specific steps of which are as follows: 1) Formation pretreatment: Collect core samples from the target basalt reservoir, and determine the high-calcium zone (8% anorthite content) and high-magnesium zone (3% pyroxene content) by XRD analysis, and pre-set the pH of the buffer solution for the dissolution and precipitation stages; In the high-calcium zone, the pH is preset to be 4.2±0.2 during the dissolution stage and 7.8±0.2 during the precipitation stage; in the high-magnesium zone, the pH is preset to be 4.8±0.2 during the dissolution stage and 7.2±0.2 during the precipitation stage.
[0024] 2) Enhanced acidification and dissolution stage: Supercritical CO2 and an aqueous solution containing a 0.1 mol / L sodium citrate-citric acid buffer pair (pH≈4.5) are co-injected through the injection well, while 0.005 mol / L gluconate (concentration ratio to the buffer system 1:20) is added simultaneously. The high-calcium zone lasts for 5 days, and the high-magnesium zone lasts for 6 days. The pH is monitored using a downhole pH sensor to ensure it remains stable within the preset range. During this stage, Ca... 2+ The concentration was increased to 120-150 mg / L, Mg 2+ The concentration was increased to 80-100 mg / L.
[0025] 3) Buffer-catalyzed synergistic precipitation stage: The injection solution is switched to an alkaline composite system (sodium bicarbonate-sodium carbonate 0.45mol / L + carbonic anhydrase biomimetic catalyst 0.2g / L). The high-calcium zone lasts for 5 days (T2:T1=1:1), and the high-magnesium zone lasts for 6 days (T2:T1=1:1). The cation concentration rapidly decreases to below 10mg / L, and calcite (high-calcium zone) and dolomite (high-magnesium zone) precipitates are generated.
[0026] 4) Intelligent Circulation and Optimization Feedback Phase: Sensors deployed in the monitoring well transmit pH and pressure data in real time. If the pH in a certain area deviates from the preset window, the proportion of the injected fluid is adjusted (e.g., if the pH is below 7.0 during the sedimentation stage, the proportion of Na2CO3 in that injection slug is automatically increased to maintain the optimal sedimentation environment). After completing one cycle, the effect and reservoir capacity are evaluated based on the monitoring data to determine whether to start a new cycle in another area of the reservoir or after adjusting the parameters.
[0027] Example 2 This embodiment provides a simplified and low-cost method for carbon mineralization of basalt formations, the specific steps of which are as follows: 1) Formation pretreatment: Collect core samples from the target basalt reservoir and determine the pH window of the buffer solution for the dissolution and precipitation stages through chemical analysis; The pH value during the dissolution stage is 4.5-5.0, and the pH value during the precipitation stage is 7.0-7.5.
[0028] 2) Enhanced acidification and dissolution stage: Supercritical CO2 and an aqueous solution containing a 0.1 mol / L sodium citrate-citric acid buffer pair (pH≈4.5) are co-injected through the injection well. Simultaneously, 0.005 mol / L gluconate (at a concentration ratio of 1:20 to the buffer system) is added. This process is continued for 5 days, with pH monitored using a downhole pH sensor to ensure the pH remains stable within the preset range. During this stage, Ca... 2+ The concentration was increased to 120-150 mg / L, Mg 2+ The concentration was increased to 80-100 mg / L.
[0029] 3) Buffer-catalyzed synergistic precipitation stage: The injection solution was switched to an alkaline composite system (sodium bicarbonate-sodium carbonate 0.45mol / L + carbonic anhydrase biomimetic catalyst 0.2g / L) for 5 days. The cation concentration rapidly decreased to below 10mg / L, and calcite and dolomite precipitates were generated.
[0030] Experimental Example This experimental example establishes a model simulating the basalt subsurface environment to verify the effectiveness of the method of the present invention. The specific steps are as follows: Model establishment: Three fresh basalt samples from the same area that are uncontaminated and have similar morphology and composition were selected. They were placed in a Hastelloy reactor that is resistant to high temperature and high pressure and acid and alkali, and the temperature and pressure conditions were set to simulate the supercritical CO2 environment (temperature: 90℃; pressure: 20MPa, simulating the basalt formation environment).
[0031] The experimental group using the method of this invention (with phased pH changes from 3.5 to 7.5) and the control group 1 using the traditional method (without pH adjustment) were compared. The water-to-rock ratio was 10:1, and the rotation speed was 300 rpm.
[0032] Experimental group: First, supercritical CO2 and enhanced buffer system (sodium citrate-citric acid 0.01mol / L + gluconate 0.005mol / L) were injected (simulating the first stage, lasting up to 120 h), then switched to injecting alkaline composite system (sodium bicarbonate-sodium carbonate 0.45mol / L + acid carbon anhydrase biomimetic catalyst 0.2g / L) (simulating the second stage, lasting up to 240 h).
[0033] Control group 1: A mixture of CO2 and deionized water was injected, and no pH adjustment was performed (simulating a natural reaction). The reaction lasted for 240 h.
[0034] Control group 2: During the experiment, fluid samples were collected periodically, filtered through a 0.45 μm filter membrane, and immediately analyzed as follows: 1) Cation analysis: Take a portion of the filtrate, acidify it with high-purity nitric acid, and then determine the Ca content using an inductively coupled plasma optical emission spectrometer (ICP-OES, such as the Thermo Scientific iCAP 7000 series). 2+ Mg 2+ Fe 2+ Plasma concentration.
[0035] 2) pH monitoring: The pH of the samples was measured offline using a pH meter (MettlerToledo SevenExcellence) calibrated with standard buffer solutions of pH 4.01, 7.00, and 10.01; in the smart cycling experiment, continuous real-time monitoring was performed using an online pH sensor (MettlerToledo InPro 4800i) installed in the loop.
[0036] After the experiment, the core samples were removed, dried, and pulverized to pass through a 150-mesh sieve. The carbonate content in the sample was calculated using the hydrochloric acid dissolution-back titration method, based on the amount of hydrochloric acid consumed, and expressed as the mass of CO2 fixed per gram of rock (mg CO2 / grock), thus quantifying the degree of carbon mineralization. The specific steps are as follows: ① Weigh 1.000 g (accurate to 0.001 g) of the dried sample into a beaker and add 50.00 mL of 0.500 mol / L hydrochloric acid standard solution.
[0037] ② Cover with a watch glass and heat on a hot plate until it boils gently for 30 minutes to allow the carbonates to react completely.
[0038] ③ After cooling, transfer the entire reaction solution to a 250 mL volumetric flask and dilute to volume with deionized water.
[0039] ④ Transfer 25.00 mL of the above solution into an Erlenmeyer flask and add 2 drops of methyl orange indicator.
[0040] ⑤ Titrate with a 0.250 mol / L sodium hydroxide standard solution until the solution changes from red to yellow as the endpoint, and record the volume of sodium hydroxide consumed.
[0041] ⑥ Simultaneously perform a blank experiment (without adding samples, the remaining steps are the same).
[0042] Calculate the carbonate content using the following formula:
[0043] Wherein, CHCl and VHCl are the concentration (mol / L) and volume (L) of hydrochloric acid, respectively; CNaOH and VNaOH are the concentration (mol / L) and titration volume (L) of sodium hydroxide, respectively; MCO2 is the molar mass of O2 (44.01 g / mol); and msample is the sample mass (g).
[0044] The test results are as follows: 1) Fluid ion concentration detection: such as Figure 1 As shown. In the first stage (before 120 hours), the Ca content in the fluid of the experimental group... 2+ The concentration continued to rise, and after switching to the second stage, the concentration of these ions decreased rapidly (e.g., Figure 2 Meanwhile, the pH remained stable within the preset range, which directly demonstrates that the two processes of "dissolution followed by precipitation" were successfully decoupled and sequentially enhanced.
[0045] 2) Comparison of mineralization: such as Figure 2 As shown, after the reaction was completed, the amount of carbonate generated in the experimental group was 4.9 times that in the control group, proving that pH switching has a strong promoting effect on precipitation.
[0046] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.
Claims
1. A method for carbon mineralization of basalt strata, characterized in that, Includes the following steps: S1: Mix acidic target buffer and supercritical CO2 fluid and inject into the target basalt reservoir to acidify and dissolve silicate minerals; S2: Inject alkaline catalytic buffer solution into the target basalt reservoir to generate and precipitate carbonate minerals; The acidic targeting buffer solution includes an acidic buffer solution and a targeting complexing agent; The alkaline catalytic buffer solution includes an alkaline buffer solution and a CO2 biomimetic catalyst.
2. The carbon mineralization method according to claim 1, characterized in that: The acidic buffer solution includes a sodium citrate-citric acid buffer solution; the targeted complexing agent includes gluconate.
3. The carbon mineralization method according to claim 2, characterized in that: The weight ratio of the sodium citrate-citric acid buffer solution to the gluconate is 1:10~20.
4. The carbon mineralization method according to claim 1, characterized in that: The alkaline buffer solution includes a sodium bicarbonate-sodium carbonate buffer solution; the CO2 biomimetic catalyst includes a carbonic anhydrase biomimetic catalyst.
5. The carbon mineralization method according to claim 4, characterized in that: The weight ratio of the sodium bicarbonate-sodium carbonate buffer solution to the carbonic anhydrase biomimetic catalyst is 90~95:5~10.
6. The carbon mineralization method according to claim 1, characterized in that: The duration of acidification and dissolution of the silicate minerals is controlled as T1, and the duration of formation and precipitation of the carbonate minerals is controlled as T2. T1:T2 = 1:1~2.
7. The carbon mineralization method according to any one of claims 1-6, characterized in that, Before step S1, the following steps are also included: S0: Sample the target basalt reservoir, determine the mineral content of the whole rock, and divide the target basalt into zones based on the determined relative mineral content; The pH values of the acidic targeting buffer and the alkaline catalytic buffer are adjusted according to the partition.
8. The carbon mineralization method according to claim 7, characterized in that: The active minerals include pyroxene and anorthite; the zoning includes a high-calcium zone, a high-magnesium zone, and a low-activity zone. The high-calcium zone is defined as the region in which the whole-rock mineral composition contains an amount of anorthite greater than or equal to 8%. The high-magnesium zone is defined as the area in which the whole-rock mineral composition contains pyroxene content greater than or equal to 3% and anorthite content less than 8%. The low-activity zone is defined as the area where the content of anorthite is less than 8% and the content of pyroxene is less than 3%.
9. The carbon mineralization method according to claim 8, characterized in that: When the partition is the high-calcium zone, the pH value of the acidic targeting buffer is controlled at 3.8~4.5, and the pH value of the alkaline catalytic buffer is controlled at 7.5~8.2; When the partition is the high magnesium region, the pH value of the acidic targeting buffer is controlled at 4.5~5.2, and the pH value of the alkaline catalytic buffer is controlled at 7.5~8.2; When the partition is the low-activity region, it is not used as the target layer for carbon mineralization.
10. The carbon mineralization method according to any one of claims 1-6, characterized in that, It also includes the following steps: The pH, pressure, temperature, and ion concentration of the target basalt reservoir are monitored in real time; the injection concentration and injection rate of the acidic targeting buffer and the alkaline catalytic buffer are dynamically adjusted based on the monitoring results.