Method for enhancing CO2 sequestration of exhausted shale oil and gas reservoir

Abstract

The invention belongs to the technical field of CO2 geological sequestration of unconventional reservoirs, and particularly relates to a method for enhancing CO2 sequestration of an exhausted shale oil and gas reservoir. The positive electrode and the negative electrode are placed in the injection well and the production well respectively, in the electrifying process, the positive electrode generates a strong oxidation effect under the action of a catalyst, no catalyst exists on the surface of the negative electrode, and a strong electrocatalytic reduction reaction cannot occur; meanwhile, a mode of intermittently supplying power and exchanging a power supply and an electrode is adopted to promote the left area and the right area of the whole reservoir to generate strong electrocatalytic oxidation, and CO2 in the whole area is promoted to be firmly adsorbed in the reservoir and cannot escape, so that the carbon sequestration effect is realized; according to the method, the storage efficiency of CO2 can be improved, the recovery efficiency of the oil reservoir is improved, energy safety is guaranteed, and emission of greenhouse gas is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of unconventional reservoir CO2 geological storage, and in particular relates to a method for enhancing CO2 storage in depleted shale oil and gas reservoirs. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] CO2 geological storage refers to the capture of CO2 emitted from industrial sources and its injection into deep saline aquifers, unexploitable coal seams, and depleted oil and gas reservoirs. Currently, CO2 geological storage has attracted much attention in the oil and gas industry. This is because, on the one hand, there is abundant reservoir space underground after the oil and gas in depleted oil and gas reservoirs are mined, and on the other hand, abandoned oil and gas wells can be reused, and CO2 can be injected and sealed in depleted oil and gas reservoirs, achieving the dual benefits of depleted oil and gas reservoir utilization and CO2 burial. Among them, shale oil and gas reservoirs in unconventional reservoirs have rich reserves, widely developed micro-nano pores, and strong CO2 adsorption performance. At the same time, depleted shale oil and gas reservoirs have lower physical properties, which can effectively prevent CO2 from escaping, making CO2 storage safer and more effective. Therefore, how to store CO2 in depleted shale reservoirs is a key issue of current CO2 storage projects.

[0004] The key to storing CO2 in depleted shale reservoirs is to maximize the adsorption of CO2 in rocks. The problem and difficulty lies in how to maximize the adsorption of injected CO2 in rocks. Currently, the low adsorption of injected CO2 on the rock surface seriously affects the carbon sequestration effect of the reservoir. Therefore, strengthening the adsorption of CO2 on the rock surface is conducive to improving the geological storage capacity of CO2.

[0005] To address this issue, relevant scholars have proposed using chemical agents such as CO2 adsorbents to enhance the adsorption of CO2 on the surface of objects. However, the large number of nanopores in shale reservoirs will cause extremely high capillary pressure, which limits the injection of other adsorbents that can attract CO2 molecules. This method cannot enhance the adsorption of CO2 on the rock surface, and thus cannot achieve the purpose of enhancing CO2 geological storage.

[0006] Patent CN 113187450 B proposes to convert CO2 into methanol and other substances to enhance oil recovery and thus improve storage. However, for depleted shale reservoirs, the efficiency of electrocatalytic CO2 reduction and conversion of carbon-containing substances is low, and a large amount of CO2 still cannot be enhanced and adsorbed in the reservoir. At present, there is an urgent need for a method that can enhance the adsorption of CO2 in shale rocks and thus enhance the storage of CO2 in the reservoir. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a method for enhancing CO2 storage in depleted shale oil and gas reservoirs. The present invention utilizes the electrocatalytic oxidation effect, intermittent power supply, and switching of power supply and electrodes to promote strong electrocatalytic oxidation in both the left and right areas of the entire reservoir, thereby greatly enhancing the adsorption of CO2 on the shale surface, achieving the effect of improving CO2 geological storage, and providing a new technical idea for CO2 geological storage in unconventional reservoirs.

[0008] Specifically, the present invention provides the following technical solutions:

[0009] In a first aspect of the present invention, a method for enhancing CO2 storage in a depleted shale oil and gas reservoir is provided, comprising the following steps:

[0010] S1. Lowering the negative electrode and the positive electrode coated with the catalyst slurry into the reservoir, wherein the positive electrode is in the injection well and the negative electrode is in the production well;

[0011] S2, injecting CO2 gas into the reservoir, turning on the power supply, so that electrocatalytic oxidation occurs at the positive electrode, which is the first power-on process;

[0012] S3, turn off the power supply, swap the positions of the positive and negative electrodes, and swap the position of the power supply; start the power-on process again to allow electrocatalytic oxidation to occur at the positive electrode, which is the second power-on process;

[0013] S4. Continue to intermittently turn the power on and off to achieve full-area enhancement of CO2 adsorption by the depleted shale oil and gas reservoir.

[0014] Preferably, in step S1, the positive electrode and the negative electrode are both inert electrodes; the inert positive electrode is a C electrode or a Pt electrode.

[0015] Preferably, in step S1, the catalyst slurry is prepared by combining a hydroxylated metal organic framework material (OH-MOF) with a perfluorinated resin solution (Nafion solution).

[0016] Preferably, the hydroxylated metal organic framework material (OH-MOF) is prepared by mixing VCl3, terephthalic acid and deionized water for hydrothermal reaction, and the product is activated and then used;

[0017] Among them, the molar ratio of VCl3, terephthalic acid and deionized water is 1:0.25:100; the temperature of the hydrothermal reaction is 150-200°C, and the time is 3d-5d; the activation process is high-temperature activation at 100-180°C and 230-280°C in sequence.

[0018] Preferably, the hydroxylated metal organic framework material is first dissolved in an ethanol solution, and after being evenly dispersed, it is mixed with a perfluorinated resin solution to obtain a catalyst slurry; wherein the volume ratio of the ethanol solution of the hydroxylated metal organic framework material to the perfluorinated resin solution is 3:1.

[0019] Preferably, in step S3, the time for shutting down the power supply is related to the specific actual situation of the depleted shale reservoir; further preferably, the time for shutting down the power supply is 24 hours to 30 days.

[0020] Preferably, in step S4, the operation of intermittently turning on and off the power supply is based on swapping the power supply and electrode position during the power on and off process. There is a catalyst on the surface of the positive electrode, and a strong oxidation reaction occurs under the action of the electric field. The ability to adsorb CO2 is enhanced, thereby achieving the purpose of storing CO2 in the entire regional reservoir.

[0021] Preferably, turning on the power supply includes: energizing the positive electrode and the negative electrode to a voltage gradient of 500 to 1200 V / m.

[0022] A second aspect of the present invention provides an application of the above-mentioned method for enhancing CO2 storage in depleted shale oil and gas reservoirs in the field of CO2 geological storage.

[0023] One or more embodiments of the present invention have at least the following beneficial effects:

[0024] (1) The present invention utilizes electrocatalysis to strengthen the oxidation reaction at the anode. Under oxidation, CO2 is a quadrupole molecule and is easily adsorbed in an oxidizing environment, thereby strengthening the adsorption of CO2 in the reservoir. Specifically, by coating the surface of the positive electrode with a catalyst slurry, the electrocatalytic oxidation effect is further enhanced, thereby improving the adsorption capacity of CO2. However, since there is no catalyst on the surface of the negative electrode, a strong electrochemical reduction reaction will not occur, thereby reducing the possibility of reducing CO2 to carbon-containing products.

[0025] (2) Taking into account that the electro-oxidation reaction is more intense in the anode area, the present invention adopts intermittent power supply and switching of power supply and electrodes to promote strong electro-catalytic oxidation in the left and right areas of the entire reservoir, so that the CO2 in the entire area is firmly adsorbed in the reservoir and cannot escape, thereby enhancing the adsorption of CO2 and enhancing the adsorption of CO2 by the reservoir in the entire area of ​​the shale mine, thereby achieving the effect of carbon sequestration. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 Schematic diagram of the experimental process of enhancing the CO2 process of depleted shale oil and gas reservoirs according to the present invention, wherein (a) is the first power-on process, and (b) is the second power-on process;

[0028] Among them, 1: reservoir; 2: injection well; 3: production well; 4: positive electrode; 5: negative electrode; 6: hydroxyl modified catalyst slurry; 7: CO2 gas;

[0029] Figure 2 The experimental equipment test flow chart for verifying the CO2 gas sealing of the electric field enhanced reservoir of the present invention; wherein, 1: autoclave; 2: constant temperature box; 3: DC power supply instrument; 4: pressure gauge; 5: intermediate container; 6: displacement pump; 7: booster pump; 8: two-way valve; 9: carbon dioxide cylinder; 10: saturated water rock sample;

[0030] Figure 3 This is a comparison chart of the pressure gauge numerical test under the methods involved in Example 1 of the present invention and Comparative Examples 1 to 4;

[0031] Figure 4 This is a test chart of the CO2 storage efficiency of Example 1 of the present invention and Comparative Examples 1 to 4. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] As mentioned above, for depleted shale reservoirs, the efficiency of electrocatalytic CO2 reduction and conversion of carbonaceous substances is low, and a large amount of CO2 still cannot be enhanced and adsorbed in the reservoir. Therefore, there is an urgent need for a method that can enhance the adsorption of CO2 in shale rocks and thus enhance the storage of CO2 in the reservoir.

[0034] A first typical embodiment of the present invention provides a method for enhancing CO2 storage in depleted shale oil and gas reservoirs, comprising the following steps:

[0035] S1. Lowering the negative electrode and the positive electrode coated with the catalyst slurry into the reservoir, wherein the positive electrode is in the injection well and the negative electrode is in the production well;

[0036] S2, injecting CO2 gas into the reservoir, turning on the power supply, so that electrocatalytic oxidation occurs at the positive electrode, which is the first power-on process;

[0037] S3, turn off the power supply, swap the positions of the positive and negative electrodes, and swap the position of the power supply; start the power-on process again to allow electrocatalytic oxidation to occur at the positive electrode, which is the second power-on process;

[0038] S4. Continue to intermittently turn the power on and off to achieve full-area enhancement of CO2 adsorption by the depleted shale oil and gas reservoir.

[0039] In one or more examples of this implementation mode, in step S1, the positive electrode and the negative electrode are both inert electrodes; the inert positive electrode is a C electrode or a Pt electrode.

[0040] In one or more examples of this embodiment, in step S1, the catalyst slurry is prepared by combining a hydroxylated metal organic framework material with a perfluorinated resin solution (Nafion solution).

[0041] In one or more examples of this embodiment, the hydroxylated metal organic framework material (OH-MOF) is prepared by mixing VCl3, terephthalic acid and deionized water for hydrothermal reaction, and the product is activated and then used;

[0042] Among them, the molar ratio of VCl3, terephthalic acid and deionized water is 1:0.25:100; the temperature of the hydrothermal reaction is 150-200°C, and the time is 3d-5d; the activation process is high-temperature activation at 100-180°C and 230-280°C in sequence.

[0043] In one or more examples of this implementation, the hydroxylated metal-organic framework material is first dissolved in an ethanol solution, and after being evenly dispersed, it is mixed with a perfluorinated resin solution to obtain a catalyst slurry; wherein the volume ratio of the ethanol solution of the hydroxylated metal-organic framework material to the perfluorinated resin solution is 3:1.

[0044] In one or more examples of this implementation mode, in step S3, the time for shutting down the power supply is related to the specific actual situation of the depleted shale reservoir; further preferably, the time for shutting down the power supply is 24 hours to 30 days.

[0045] In one or more embodiments of this implementation mode, in step S4, the operation of intermittently turning on and off the power supply is based on the swapping of the power supply and the electrode position during the power on and off process. There is a catalyst on the surface of the positive electrode, and a strong oxidation reaction occurs under the action of the electric field. The ability to adsorb CO2 is enhanced, thereby achieving the purpose of storing CO2 in the entire regional reservoir.

[0046] In one or more embodiments of this implementation mode, turning on the power supply includes: energizing the positive electrode and the negative electrode to a voltage gradient of 500 to 1200 V / m.

[0047] A second typical implementation of the present invention provides an application of the above-mentioned method for enhancing CO2 storage in depleted shale oil and gas reservoirs in the field of CO2 geological storage.

[0048] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0049] Example 1 :This embodiment provides a method for enhancing CO2 storage in depleted shale oil and gas reservoirs, which specifically includes the following steps:

[0050] (1) Preparation of hydroxylated metal organic framework materials (OH-MOF)

[0051] Hydroxylated metal organic framework (OH-MOF) was prepared by hydrothermal method, specifically, a mixture of metal salt VCl3, terephthalic acid and deionized water (molar ratio 1:0.25:100) was placed in a hydrothermal reactor and reacted at 180°C for 4 days to obtain a light yellow product. Subsequently, it was activated at 150°C and 250°C for 4 to 5 hours respectively and set aside.

[0052] (2) Preparation of inert positive and negative electrodes

[0053] Prepare inert positive and negative electrodes that can smoothly pass through the wellhead, with the inert positive electrode being the C electrode.

[0054] (3) Take 5 mg of the hydroxylated metal organic framework material prepared in step (1), and evenly disperse it in 1 mL of ethanol solution by ultrasonic dispersion. Then, take 750 μL of the dispersed hydroxylated metal organic framework material and continue ultrasonic mixing with 250 μL of Nafion solution to prepare a catalyst slurry. Use a pipette to evenly drip the catalyst slurry on the electrode surface, dry it naturally and set it aside; the negative electrode does not need to be treated to ensure that the positive electrode coated with the catalyst slurry undergoes strong oxidation under the action of the electric field, and near the negative electrode area, due to the absence of a catalyst, no strong electrocatalytic reduction reaction will occur.

[0055] (4) Applying an electric field to enhance CO2 adsorption in the left side of the mine reservoir (injection well)

[0056] Inert positive and negative electrodes are placed in the mine reservoir, with the positive electrode in the injection well and the negative electrode in the production well. During the power-on process, the positive electrode undergoes strong oxidation under the action of the catalyst, and the injected CO2 is greatly adsorbed in the positive electrode area of ​​the reservoir, further improving the CO2 storage efficiency. There is no catalyst on the surface of the negative electrode, and no strong electrocatalytic reduction reaction will occur, reducing the possibility of reducing CO2 to carbon-containing products. Then, an electric field is applied to promote enhanced CO2 adsorption in the entire left area of ​​the mine reservoir.

[0057] (5) Apply intermittent power to enhance the CO2 adsorption content in the mine reservoir area

[0058] The left area of ​​the mine strengthens the adsorption of a large amount of CO2. After the adsorption is saturated (the adsorption is saturated by default when the formation pressure on the mine is stable), the power is turned off. The concentration of CO2 in the positive area is higher than that in the negative area. Under the effect of the CO2 concentration difference, the CO2 in the positive area slowly flows to the negative area (right side). Therefore, under the condition of intermittent power supply, the adsorption of CO2 by the entire reservoir increases, thereby improving the CO2 storage efficiency.

[0059] (6) Replace the power supply and electrode position to further enhance the CO2 adsorption content in the reservoir area

[0060] On the basis of improving the CO2 storage efficiency by intermittent power supply, the negative electrode area (right side) of the reservoir still has the characteristic of poor CO2 adsorption. At this time, by switching the power supply and electrode position, the CO2 in the positive electrode area can be greatly adsorbed in the reservoir under the action of electrocatalytic oxidation. By continuously switching the power supply and electrode position, the CO2 adsorption content in the entire area of ​​the reservoir is greatly increased and maintained in balance, and the CO2 storage efficiency is enhanced.

[0061] Comparative Example 1 :This comparative example provides a method for enhancing CO2 storage in depleted shale oil and gas reservoirs, which specifically includes the following steps:

[0062] (1) Preparation of hydroxylated metal organic framework materials (OH-MOF)

[0063] Hydroxylated metal organic framework (OH-MOF) was prepared by hydrothermal method, specifically, a mixture of metal salt VCl3, terephthalic acid and deionized water (molar ratio 1:0.25:100) was placed in a hydrothermal reactor and reacted at 180°C for 4 days to obtain a light yellow product. Subsequently, it was activated at 150°C and 250°C for 4 to 5 hours respectively and set aside.

[0064] (2) Preparation of inert positive and negative electrodes

[0065] Prepare inert positive and negative electrodes that can smoothly pass through the wellhead, with the inert positive electrode being the C electrode.

[0066] (3) Take 5 mg of the hydroxylated metal organic framework material prepared in step (1), and evenly disperse it in 1 mL of ethanol solution by ultrasonic dispersion. Then, take 750 μL of the dispersed hydroxylated metal organic framework material and continue ultrasonic mixing with 250 μL of Nafion solution to prepare a catalyst slurry. Use a pipette to evenly drip the catalyst slurry on the electrode surface, dry it naturally and set it aside; the negative electrode does not need to be treated to ensure that the positive electrode coated with the catalyst slurry undergoes strong oxidation under the action of the electric field, and near the negative electrode area, due to the absence of a catalyst, no strong electrocatalytic reduction reaction will occur.

[0067] (4) Applying an electric field to observe the CO2 adsorption content in the left side of the mine reservoir (injection well)

[0068] Inert positive and negative electrodes are placed in the mine reservoir, with the positive electrode in the injection well and the negative electrode in the production well. During the power-on process, the positive electrode undergoes strong oxidation under the action of the catalyst, and the injected CO2 is greatly adsorbed in the positive electrode area of ​​the reservoir, further improving the CO2 storage efficiency. There is no catalyst on the surface of the negative electrode, and no strong electrocatalytic reduction reaction will occur, reducing the possibility of reducing CO2 to carbon-containing products. Then, an electric field is applied to promote enhanced CO2 adsorption in the entire left area of ​​the mine reservoir.

[0069] (5) Apply intermittent power to enhance the CO2 adsorption content in the mine reservoir area

[0070] After one day of power on, a large amount of CO2 is adsorbed in the positive electrode area under the action of electrocatalytic oxidation. After the adsorption is saturated, the power is turned off. The concentration of CO2 in the positive electrode area is higher than that in the negative electrode area. Under the action of the CO2 concentration difference, the CO2 in the positive electrode area slowly flows to the negative electrode area. Therefore, when the power is intermittently turned on, the adsorption of CO2 in the entire reservoir increases, which improves the CO2 storage efficiency.

[0071] Comparative Example 2 :This comparative example provides a method for enhancing CO2 storage in depleted shale oil and gas reservoirs, which specifically includes the following steps:

[0072] (1) Preparation of hydroxylated metal organic framework materials (OH-MOF)

[0073] Hydroxylated metal organic framework (OH-MOF) was prepared by hydrothermal method, specifically, a mixture of metal salt VCl3, terephthalic acid and deionized water (molar ratio 1:0.25:100) was placed in a hydrothermal reactor and reacted at 180°C for 4 days to obtain a light yellow product. Subsequently, it was activated at 150°C and 250°C for 4 to 5 hours respectively and set aside.

[0074] (2) Preparation of inert positive and negative electrodes

[0075] Prepare inert positive and negative electrodes that can smoothly pass through the wellhead, with the inert positive electrode being the C electrode.

[0076] (3) Take 5 mg of the hydroxylated metal organic framework material prepared in step (1), and evenly disperse it in 1 mL of ethanol solution by ultrasonic dispersion. Then, take 750 μL of the dispersed hydroxylated metal organic framework material and continue ultrasonic mixing with 250 μL of Nafion solution to prepare a catalyst slurry. Use a pipette to evenly drip the catalyst slurry on the electrode surface, dry it naturally and set it aside; the negative electrode does not need to be treated to ensure that the positive electrode coated with the catalyst slurry undergoes strong oxidation under the action of the electric field, and near the negative electrode area, due to the absence of a catalyst, no strong electrocatalytic reduction reaction will occur.

[0077] (4) Applying an electric field to observe the CO2 adsorption content in the reservoir area of ​​the mine

[0078] Inert positive and negative electrodes are lowered into the mine reservoir, with the positive electrode in the injection well and the negative electrode in the production well. When the power is turned on, the positive electrode undergoes electrocatalytic oxidation under the action of the catalyst, which greatly adsorbs the injected CO2 in the positive electrode area of ​​the reservoir, further improving the CO2 storage efficiency.

[0079] Comparative Example 3 :This comparative example provides a method for enhancing CO2 storage in depleted shale oil and gas reservoirs, which specifically includes the following steps:

[0080] (1) Preparation of hydroxylated metal organic framework materials (OH-MOF)

[0081] Hydroxylated metal organic framework (OH-MOF) was prepared by hydrothermal method, specifically, a mixture of metal salt VCl3, terephthalic acid and deionized water (molar ratio 1:0.25:100) was placed in a hydrothermal reactor and reacted at 180°C for 4 days to obtain a light yellow product. Subsequently, it was activated at 150°C and 250°C for 4 to 5 hours respectively and set aside.

[0082] (2) Preparation of inert positive and negative electrodes

[0083] Prepare inert positive and negative electrodes that can smoothly pass through the wellhead, with the inert positive electrode being the C electrode.

[0084] (3) Take 5 mg of the hydroxylated metal organic framework material prepared in step (1), and evenly disperse it in 1 mL of ethanol solution by ultrasonic dispersion. Then, take 750 μL of the dispersed hydroxylated metal organic framework material and continue ultrasonic mixing with 250 μL of Nafion solution to prepare a catalyst slurry. Use a pipette to evenly drip the catalyst slurry on the electrode surface, dry it naturally and set it aside; the negative electrode does not need to be treated to ensure that the positive electrode coated with the catalyst slurry undergoes strong oxidation under the action of the electric field, and near the negative electrode area, due to the absence of a catalyst, no strong electrocatalytic reduction reaction will occur.

[0085] (4) Applying an electric field to observe the CO2 adsorption content in the reservoir area of ​​the mine

[0086] Inert positive and negative electrodes are lowered into the mine reservoir, with the positive electrode in the production well and the negative electrode in the injection well. When the power is turned on, the negative electrode undergoes electrocatalytic reduction under the action of the catalyst, converting the injected CO2 into carbon-containing substances. Although electrocatalytic oxidation occurs on the surface of the positive electrode, the overall CO2 adsorption content in the reservoir is low, and the CO2 storage efficiency is low.

[0087] Comparative Example 4 :This comparative example provides a method for enhancing CO2 storage in depleted shale oil and gas reservoirs, which specifically includes the following steps:

[0088] Adsorption of single injection CO2 in the reservoir area of ​​the mine:

[0089] The CO2 captured from the mine is transported to the wellhead through a pipeline, and then injected from the injection well through a certain booster device at the wellhead. The injected CO2 migrates toward the production well under the drive of the injection pressure difference. In the porous medium of the underground reservoir, part of the CO2 is adsorbed on the surface of the underground porous medium and sealed in the reservoir because the micro-nano pores of the reservoir have a certain adsorption effect on CO2, thus realizing the CO2 storage in the depleted oil and gas reservoir. Since there is no other effect, the effect of CO2 adsorption on the underground porous medium is poor, and the storage efficiency of CO2 in the depleted oil and gas reservoir is low.

[0090] Test Example 1 :This example tests the CO2 storage rate of the methods involved in Example 1 and Comparative Examples 1 to 4

[0091] This test example is a related experiment carried out in the laboratory. The basic physical property parameters of the sandstone core are shown in Table 1, where the core numbers LT1 to LT5 correspond to Example 1 and Comparative Examples 1 to 4, respectively:

[0092] Table 1

[0093] Core number Length, cm Diameter, cm Permeability, md LT1 7.017 2.493 0.021 LT2 7.218 2.512 0.023 LT3 7.329 2.499 0.022 LT4 7.126 2.218 0.019 LT5 7.235 2.389 0.020

[0094] Use Figure 2 The experimental equipment shown is used to verify the electric field enhanced CO2 gas sealing in the reservoir. A fixed pressure is given to the high temperature and high pressure autoclave system, and a pressure gauge is used to detect the real-time dynamic pressure. The pressure at this time is the pressure of CO2 in the system that is not adsorbed by the core. The fixed pressure minus the real-time dynamic pressure (directly measured by the pressure gauge) is the pressure caused by the CO2 adsorbed inside the core, which can indirectly reflect the amount of CO2 adsorbed in the core.

[0095] By testing the pressure gauge values ​​under different methods in Example 1 and Comparative Examples 1 to 4 (as shown in Table 2 and Figure 3As shown), the CO2 adsorption capacity of the core under different modes can be obtained by calculation (the CO2 adsorption capacity is represented by the pressure value, and the adsorption pressure is (initial pressure-final pressure), which is the CO2 adsorption pressure). The CO2 storage rate is calculated as CO2 adsorption pressure / initial pressure*100%, which can reflect the CO2 storage capacity in the reservoir.

[0096] Table 2

[0097] Examples Initial pressure(MPa) Final pressure(MPa) Change value (MPa) <![CDATA[CO2 sequestration rate (%)]]> Example 1 16 8.89 7.11 44.43 Comparative Example 1 16 9.81 6.19 38.69 Comparative Example 2 16 11.76 4.24 26.5 Comparative Example 3 16 12.17 3.83 23.94 Comparative Example 4 16 13.47 2.53 15.81

[0098] like Figure 4 As shown, it can be seen from the CO2 storage rate that compared with Comparative Example 1, Example 1 also performs the process of exchanging the power supply and the electrode position, which is more helpful to improve the CO2 storage in the reservoir;

[0099] Comparison between Example 1 and Example 2 shows that intermittent power-on is conducive to the uniform dispersion of CO2 in the reservoir and the adsorption and storage of CO2. At the same time, changing the electrode position during intermittent power-on can make the reservoir have an all-round CO2 adsorption effect, thereby maximizing the CO2 storage effect in the reservoir.

[0100] Comparison between Comparative Example 2 and Comparative Example 3 shows that the electrocatalytic oxidation method produced by the positive electrode in the injection well has a better CO2 storage effect than the electrocatalytic reduction method of the positive electrode in the production well;

[0101] Compared with the single carbon dioxide injection method of Comparative Example 4, the electrocatalytic oxidation method of adsorbing carbon dioxide in Example 1 is more conducive to the storage of carbon dioxide.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for enhancing CO2 storage in depleted shale oil and gas reservoirs, characterized in that: The following steps are involved: S1. Lowering the negative electrode and the positive electrode coated with the catalyst slurry into the reservoir, wherein the positive electrode is in the injection well and the negative electrode is in the production well; S2, injecting CO2 gas into the reservoir, turning on the power supply, so that electrocatalytic oxidation occurs at the positive electrode, which is the first power-on process; S3, turn off the power supply, swap the positions of the positive and negative electrodes, and swap the position of the power supply; start the power-on process again to allow electrocatalytic oxidation to occur at the positive electrode, which is the second power-on process; S4. Continue to intermittently turn the power on and off to achieve full-area enhancement of CO2 adsorption by the depleted shale oil and gas reservoir.

2. The method according to claim 1, characterized in that In step S1, the positive electrode and the negative electrode are both inert electrodes; the inert positive electrode is a C electrode or a Pt electrode.

3. The method according to claim 1, characterized in that In step S1, the catalyst slurry is prepared by compounding a hydroxylated metal organic framework material and a perfluorinated resin solution.

4. The method according to claim 3, characterized in that The hydroxylated metal organic framework material is prepared by mixing VCl3, terephthalic acid and deionized water for hydrothermal reaction, and the product is activated and then used.

5. The method according to claim 4, characterized in that The molar ratio of VCl3, terephthalic acid and deionized water is 1:0.25:100; the temperature of the hydrothermal reaction is 150-200°C and the time is 3d-5d; the activation process is high-temperature activation at 100-180°C and 230-280°C in sequence.

6. The method according to claim 3, characterized in that The hydroxylated metal organic framework material is first dissolved in an ethanol solution, and after being evenly dispersed, it is mixed with a perfluorinated resin solution to obtain a catalyst slurry; wherein the volume ratio of the ethanol solution of the hydroxylated metal organic framework material to the perfluorinated resin solution is 3:

1.

7. The method according to claim 1, characterized in that In step S3, the time for shutting down the power supply is related to the specific actual situation of the depleted shale reservoir; further preferably, the time for shutting down the power supply is 24 hours to 30 days.

8. The method according to claim 1, characterized in that In step S4, the operation of intermittently turning on and off the power supply is based on the swapping of the power supply and the electrode position during the power on and off process. There is a catalyst on the surface of the positive electrode, which undergoes strong oxidation under the action of the electric field, and the ability to adsorb CO2 is enhanced, thereby achieving the purpose of storing CO2 in the entire regional reservoir.

9. The method according to claim 1, characterized in that The power supply is turned on including: electrifying the positive electrode and the negative electrode until the voltage gradient is 500-1200 V / m.

10. Use of the method for enhancing CO2 storage in depleted shale oil and gas reservoirs as claimed in any one of claims 1 to 9 in the field of CO2 geological storage.

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