High-toughness and high-adhesion organic-inorganic composite material for treating CO2 crack leakage as well as preparation method and application of high-toughness and high-adhesion organic-inorganic composite material

Abstract

The invention discloses a high-toughness high-adhesion organic-inorganic composite material for treating CO2 crack leakage and a preparation method and application thereof, and belongs to the technical field of CO2 leakage treatment materials. The composite material comprises an organic phase, an inorganic phase, an initiator and a cross-linking agent, and the preparation method comprises the following steps: adding a calcium carbonate oligomer gel dispersion liquid into a polyvinyl alcohol-polydopamine solution, and stirring and mixing to obtain a PVA-PDA / CCO solution; then slowly dropwise adding an acrylic monomer into the solution to obtain a PVA-AA-PDA / CCO solution; then sequentially adding a covalent cross-linking agent and a sodium tetraborate solution drop by drop; adding an initiator under the condition of N2 protection ice bath to prepare a PVA-PAA-PDA / CCO precursor solution; during application, the precursor solution is injected into a stratum, ionic bonding solidification is carried out on the top of a cap slip fault in situ, and leaked CO2 is forced to transversally migrate. The composite material has high compression strength, high tensile strength, high tensile strain and high adhesion strength, and can realize underwater long-acting sealing with a shale interface through multiple synergistic bonding to form a high-toughness and high-adhesion blocking barrier.

Description

Technical Field

[0001] This invention belongs to the field of materials technology for controlling CO2 leakage, specifically relating to a high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage, its preparation method, and its application. Background Technology

[0002] In long-term CO2 geological sequestration in deep saline aquifers, the integrity of the caprock is a crucial barrier to prevent large-scale vertical upward CO2 migration and leakage. For leaks caused by caprock fault slippage, traditional organic remediation materials, due to limitations in mechanical properties and long-term stability, struggle to meet the stringent requirements for long-term caprock sealing. Organic-inorganic composite materials, through their "organic-inorganic soft-hard bonding" and the "inherent strong stability of the inorganic phase," exhibit unique advantages in preventing / controlling caprock CO2 leakage. However, they also face two major challenges: "how to eliminate the organic-inorganic phase interface" and "how to achieve sustained high adhesion underwater."

[0003] Organic-inorganic composite materials are typically prepared through physical blending, incorporating inorganic fillers into an organic matrix. For example, Chinese patent application CN116217975A discloses a method for preparing an organic-inorganic hybrid dual-conductive network polyvinyl alcohol composite hydrogel, which involves in-situ polymerization of polyvinyl alcohol, pyrrole monomers, and carbon nanotubes to obtain an organic-inorganic hybrid dual-conductive network gel. Another example is Chinese patent application CN114004202A, which discloses a nano-titanium dioxide polymer plugging agent and its preparation method, which disperses nano-titanium dioxide in an acrylamide solution to form a temperature- and salt-resistant temporary plugging agent. These traditional physical blending methods have significant drawbacks: poor dispersion of the inorganic phase in the organic phase, a distinct organic-inorganic phase interface leading to phase interface defects and internal structural discontinuities, and CO2 escape along the organic-inorganic phase interface. "How to eliminate the organic-inorganic phase interface and construct a continuous and uniform structure" is a major technical problem that urgently needs to be solved in the design of organic-inorganic composite materials.

[0004] Meanwhile, the deep saline aquifer environment of CO2 geological sequestration places extremely high demands on the underwater adhesion performance of remediation materials. In organic-inorganic composites, the inorganic phase has a rigid structure, lacking the flexible chain segments of organic materials. Its surface energy is relatively high, and most functional groups are inert sites, making it unable to form a strong interaction and adhesion with the rock substrate surface. Furthermore, traditional organic-inorganic composites are physical blends, and in underwater environments, water molecules easily penetrate into the material-substrate interface and the organic-inorganic phase interface, leading to separation of the organic-inorganic phase and debonding at the material-substrate interface. "How to impart adhesive properties to the inorganic phase to achieve continuous underwater adhesion of organic-inorganic composites" is another technical problem that urgently needs to be solved in the design of organic-inorganic composite materials.

[0005] Therefore, it is necessary to construct a high-strength, high-toughness, high-adhesion organic-inorganic homogeneous composite material to meet the stringent requirements of the caprock in the far-well zone of the CO2 geological storage system, which requires "easy injection, long-distance travel, durability, and long-term sealing," and to provide key material support for ensuring the long-term safety of CO2 geological storage. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a high-strength, high-toughness, and high-adhesion organic-inorganic composite material for controlling CO2 leakage through cracks, along with its preparation method and applications. Upon contact with the CO2 plume at the top of the caprock, the composite material of this invention undergoes in-situ ion-bonding and solidification, forming a phase-separation-free, high-strength, high-toughness, and high-adhesion sealing barrier. Through multiple synergistic bonds with the shale interface, it achieves long-term underwater sealing, preventing CO2 from rising and migrating upwards and forcing CO2 to move laterally.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] A high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage, comprising, by mass percentage:

[0009] Polyvinyl alcohol (PVA) and acrylic acid (AA) monomers in a mass ratio of 1:(1-4), 20 wt%;

[0010] Polydopamine (PDA), 0.1-1.0 wt%;

[0011] Calcium carbonate oligomer gel (CCO), 1.2-9.6 wt% (effective solids content);

[0012] Covalent crosslinking agent, 0.1-0.2 wt%;

[0013] Sodium tetraborate (Borax), 0.05-0.1 wt%;

[0014] The remainder consists of deionized water and initiator, wherein the amount of initiator added is 0.78-1.56 wt% of the total mass of acrylic acid and polydopamine.

[0015] In this invention, polyvinyl alcohol, acrylic acid monomer and polydopamine are organic phase materials, calcium carbonate oligomer gel is inorganic phase material, and sodium tetraborate is borate ester crosslinking agent.

[0016] In one specific embodiment of the present invention, the covalent crosslinking agent is one of N,N-methylenebisacrylamide (MBA), polyethylene glycol-400 (PEG-400), glutaraldehyde (GA), chromium acetate (Cr(Ac)3), polyethyleneimine (PEI), and phenolic crosslinking agent (FQ).

[0017] In one specific embodiment of the present invention, the initiator is one or a combination of ammonium persulfate (APS), potassium persulfate (KPS), sodium bisulfite (NaHSO3), azobisisobutyronitrile (AIBN), and azobisisobutyramidine hydrochloride (V-50).

[0018] In one specific embodiment of the present invention, the calcium carbonate oligomer gel is prepared by a method comprising the following steps:

[0019] A1. Dissolve calcium chloride dihydrate (CaCl2·2H2O) in anhydrous ethanol to form a clear calcium chloride dihydrate-ethanol solution;

[0020] A2. Add triethylamine (TEA) to the solution obtained in step A1 and stir magnetically at room temperature to form a mixed solution of calcium chloride dihydrate, triethylamine, and ethanol.

[0021] A3. Continuously bubble CO2 into the mixed solution obtained in step A2 until the system stabilizes, then stop bubbling. In this step, continuously bubble CO2 at a low rate and observe the color change of the solution: the mixed solution first gradually turns into a translucent state, then produces a white turbidity (CaCO3). n When the white turbidity no longer occurs (clusters), the system enters a stable state, and aeration is stopped;

[0022] A4. Let the system after the reaction in step A3 stand at room temperature until a light blue transparent calcium carbonate oligomer sol is observed to form, then stop the standing process.

[0023] A5. Centrifuge the sol obtained in step A4, pour off the supernatant to obtain unpurified calcium carbonate oligomer gel, and wash it several times with anhydrous ethanol to fully remove residual TEA.

[0024] A6. Disperse the unpurified calcium carbonate oligomer gel washed in step A5 again in anhydrous ethanol to form a calcium carbonate oligomer ethanol dispersion. Centrifuge the dispersion again, pour off the supernatant, and obtain the purified calcium carbonate oligomer gel.

[0025] Among them, 1 mmol CaCl2·2H2O corresponds to an ethanol volume of 24.5-392.2 mL and a TEA volume of 1.35-43.1 mL.

[0026] As a specific embodiment of the present invention, the polydopamine is prepared by a method comprising the following steps: adding dopamine hydrochloride to a pre-cooled alkaline buffer solution, and sonicating in an ice bath until completely dissolved to obtain a dopamine solution; subjecting the dopamine solution to a self-polymerization reaction in an ice bath environment to obtain a dark brown polydopamine solution; subsequently performing centrifugation, washing, and rotary evaporation drying to obtain polydopamine powder.

[0027] As a specific embodiment of the present invention, the alkaline buffer solution is preferably a solution with a pH value of 8.0-9.5, such as one of Tris-HCl solution, concentrated ammonia, sodium hydroxide solution, sodium bicarbonate, and phosphate buffer solution.

[0028] A method for preparing a high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage, comprising the following steps:

[0029] B1. Dissolve polyvinyl alcohol in deionized water and stir at high temperature to form a polyvinyl alcohol solution. Disperse dry polydopamine powder in deionized water and sonicate to form a polydopamine solution. Mix the polyvinyl alcohol solution and the polydopamine solution to form a polyvinyl alcohol-polydopamine solution.

[0030] B2. Disperse calcium carbonate oligomers in deionized water and sonicate to obtain a stable colloid; under continuous stirring, slowly add the calcium carbonate oligomer dispersion dropwise to a polyvinyl alcohol-polydopamine solution to form a homogeneous polyvinyl alcohol-polydopamine / calcium carbonate oligomer solution:

[0031] B3. Slowly add acrylic monomer to the solution obtained in step B2 and stir thoroughly until the mixture is homogeneous to obtain an organic-inorganic blend solution of polyvinyl alcohol-acrylic acid-polydopamine / calcium carbonate oligomer.

[0032] B4. Under stirring conditions, slowly add the covalent crosslinking agent solution and sodium tetraborate solution dropwise to the solution obtained in step B3, and stir thoroughly until the system is mixed evenly.

[0033] B5. Purge the reaction mixture obtained in step B4 with N2 to remove oxygen. Under the protective atmosphere of continuous N2 purging, place the reaction mixture in an ice bath environment. Then, add the initiator solution dropwise to the solution. In order to achieve slow chain growth at low temperature, the reaction mixture is continuously stirred in the ice bath environment for 2 hours. Then, the temperature is raised to room temperature to obtain a polyvinyl alcohol-polyacrylic acid-polydopamine / calcium carbonate oligomer precursor solution.

[0034] A method for applying a high-strength, high-toughness, high-adhesion organic-inorganic composite material to control CO2 crack leakage includes the following steps:

[0035] C1. Inject the precursor solution of the high-strength, high-toughness, high-adhesion organic-inorganic composite material for treating CO2 fracture leakage into the formation through an injection well;

[0036] C2. After well shut-in, the precursor solution migrates deep to the slip fault in the caprock and comes into contact with the CO2 plume at the top of the caprock, where it undergoes in-situ ion bonding and solidification, forming a high-strength, tough, and highly adhesive sealing barrier without phase separation.

[0037] C3. The solidified sealing barrier continues to grow into a continuous block and strengthens along the extensional growth. It achieves long-term underwater sealing with the shale interface through multiple synergistic bonds, preventing CO2 from floating and migrating upwards and forcing CO2 to move laterally.

[0038] The synthesis mechanism of the high-strength, high-toughness, and high-adhesion organic-inorganic homogeneous material of this invention is as follows: Figure 1 As shown, within the polyvinyl alcohol-polyacrylic acid-polydopamine / calcium carbonate oligomer (PVA-PAA-PDA / CCO) gel, the carboxyl groups (-COOH) in PAA dissociate into carboxyl anions (-COO-), which react with the Ca exposed on the CCO surface. 2+ Formation of Ca 2+ -COO - Ionic bond; Borate ions (B(OH)4) produced by the hydrolysis of Borax - It undergoes a complexation reaction with the -OH group in PVA to form a BO coordination bond; the Ca in CCO... 2+ Ca-N and Ca-O coordinate bonds are formed with the amino (-NH2) or phenolic hydroxyl (-OH) groups in PDA; hydrogen bonds are formed between the hydroxyl (-OH) groups in PVA and the carboxyl (-COOH) groups in PAA; hydrogen bonds are formed between the phenolic hydroxyl (-OH) and amino (-NH2) groups in PDA and the carboxyl (-COOH) groups in PAA, the hydroxyl (-OH) groups in PVA, and the hydroxyl (-OH) groups in CCO; at the interface between PVA-PAA-PDA / CCO gel and shale core, the Ca exposed on the CCO surface... 2+ The phenolic hydroxyl groups (-OH) and amino groups (-NH2) in PDA can form coordination bonds with metal cations on the shale surface or hydrogen bonds with hydroxyl groups on the shale surface, and the hydroxyl groups (-OH) in PVA and the carboxyl groups (-COOH) in PAA can form hydrogen bonds with hydroxyl groups on the shale surface.

[0039] Beneficial effects:

[0040] (1) The composite material provided by the present invention constructs an organic-inorganic continuous bulk structure through molecular-level chemical bonding. It is an interface-free continuous phase structure, which eliminates the separation of organic-inorganic phases and the accumulation of inorganic particles, avoids the occurrence of pores and cracks, and endows the organic-inorganic composite gel with mechanical strength similar to that of a single piece of calcite.

[0041] (2) In the composite material provided by the present invention, with the removal of triethylamine, the small-sized (CaCO3) n Polyionic clusters gradually grow and aggregate to form nuclei. CCO can grow into centimeter-scale continuous blocky materials, and directionally crystallize into monolithic calcite crystals.

[0042] (3) In the composite material provided by the present invention, the alkaline TEA on the CCO surface and the large amount of exposed Ca 2+ The active site promotes the dissociation of the carboxyl group (-COOH) in the organic PAA molecule into a carboxyl anion (-COO). - ), with Ca exposed on the surface of inorganic CCO molecules 2+ The active site forms Ca through an acid-base reaction. 2+ -COO - Ionic bonds; organic PVA-PAA-PDA forms a flexible network through C-C covalent bonds, while inorganic Ca... 2+ -COO - Ionic crosslinking forms rigid nodes, and the organic-inorganic network structure uniformly disperses stress, avoiding stress concentration, thus enabling the prepared organic-inorganic composite gel to have both high rigidity and high flexibility.

[0043] (4) In the composite material of the present invention, PVA-PAA-PDA / CCO exhibits multiple synergistic adhesion: the hydroxyl groups (-OH) of the PVA segments and the incompletely dissociated carboxyl groups (-COOH) of the PAA segments can combine with the hydroxyl groups on the shale surface to form hydrogen bonds; the phenolic hydroxyl groups of the PDA segments can form coordination bonds with the cations on the shale surface; and the exposed Ca on the CCO surface... 2+ It can form ionic bonds with negatively charged sites on the shale surface; the coordination bonds of PDA, the ionic bonds of PAA, and Ca 2+ The ion bridging consists of water-resistant and stable chemical bonds, enabling continuous high adhesion of the shale-gel interface underwater.

[0044] (5) In the composite material of the present invention, CCO grows epitaxially along the calcite crystal plane on the shale surface to form a continuous single-crystal calcite layer consistent with the shale lattice, and the phenolic hydroxyl groups of PDA react with the Ca on the CCO surface. 2+ Enriched at the interface, it further induces the directional nucleation and growth of calcite crystals. Attached Figure Description

[0045] Figure 1 This is a diagram illustrating the synthesis mechanism of the organic-inorganic composite material of the present invention;

[0046] Figure 2 The initial viscosity diagrams are for the precursor solutions of each embodiment and comparative example;

[0047] Figure 3 Physical images of the gels used in each embodiment and comparative example;

[0048] Figure 4 This is a schematic diagram of the initial adhesion of PVA-PAA-PDA / CCO gel to different substrates;

[0049] Figure 5This is a schematic diagram showing the adhesion of PVA-PAA-PDA / CCO gel to different substrates after immersion in salt water.

[0050] Figure 6 Stress-strain curves of the gels in each embodiment and comparative example;

[0051] Figure 7 Comparison chart of compressive strength between PVA-PAA-PDA / CCO gel and existing inorganic-organic composite materials;

[0052] Figure 8 A comparison diagram showing the adhesion strength of the gels in each embodiment and comparative example on different substrates;

[0053] Figure 9 The pressure difference curves of the gels in the CO2 breakthrough pressure test for each embodiment and comparative example;

[0054] Figure 10 The images show the gel adhering to the crack wall after the CO2 breakthrough pressure test for Examples 1, 2, and 3. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0056] The calcium carbonate oligomer (CCO) gels in the following examples were prepared using the following method:

[0057] 1.2 g of calcium chloride dihydrate (CaCl2·2H2O) was dissolved in 400 mL of anhydrous ethanol to form a clear CaCl2·2H2O-ethanol solution; 44 mL of triethylamine (TEA) was added to the CaCl2·2H2O-ethanol solution and the mixture was magnetically stirred at 25 °C for 30 min to form a mixed solution of CaCl2·2H2O-triethylamine-ethanol.

[0058] CO2 was continuously bubbled into a CaCl2·2H2O-triethylamine-ethanol mixed solution at a low rate (100 mL / min) until a translucent solution was formed. CO2 was then continued to bubble until a white turbidity (CaCO3) was produced. n Once the clusters stabilize and no longer produce white turbidity, stop introducing CO2.

[0059] A light blue transparent CCO sol was obtained by standing at 25℃ for 30 minutes.

[0060] The CCO sol was centrifuged at 5000 rpm for 30 min, and the supernatant was poured off to obtain unpurified CCO gel. The gel was washed several times with ethanol to remove residual TEA.

[0061] The unpurified CCO gel was redispersed in ethanol and centrifuged again at 5000 rpm for 30 min. The supernatant was then discarded to obtain the purified CCO gel.

[0062] Example 1 (PVA-PAA-PDA / CCO gel)

[0063] S1. Dissolve dopamine hydrochloride (DA, 0.05 g) in pre-cooled Tris-HCl (1.5 mM, pH 8.8, 2.5 mL) alkaline buffer solution, cool and sonicate in an ice bath at 0 °C for 10 min to obtain DA solution; allow DA solution to stand in an ice bath at 0 °C for self-polymerization for 12 h to obtain dark brown polydopamine (PDA) solution; collect PDA precipitate by centrifugation at 5000 rpm for 15 min, wash three times with deionized water, dry the obtained PDA solid by rotary evaporation (40 °C, vacuum 0.1 MPa) for 24 h, grind to obtain PDA powder;

[0064] S2. Add polyvinyl alcohol 1799 (PVA, 2.5g) to deionized water (20.0mL), and stir magnetically at 95℃ (600rpm) for 2h until completely dissolved to obtain a PVA solution; disperse the above dried PDA powder in deionized water (2.5mL), and sonicate for 10min to obtain a PDA solution; mix the PVA solution and PDA solution, and mechanically stir (800rpm) for 1h to form a homogeneous PVA-PDA solution;

[0065] S3. Disperse calcium carbonate oligomer (CCO, effective solid content 0.6g) gel in deionized water (5.0mL) and sonicate for 10min to obtain a stable colloid; slowly add the CCO dispersion dropwise to the solution (PVA-PDA solution) obtained in step S2 and mechanically stir (500rpm) for 1h to form a PVA-PDA / CCO solution.

[0066] S4. Slowly add 2.5 mL of acrylic acid (AA) monomer to the solution (PVA-PDA / CCO solution) obtained in step S3, and mechanically stir (500 rpm) for 1 h to obtain PVA-AA-PDA / CCO solution;

[0067] S5. Add N,N-methylenebisacrylamide (MBA, 0.1 g dissolved in 2.5 mL deionized water) solution and sodium tetraborate solution (Borax, 0.1 g dissolved in 2.5 mL deionized water) dropwise to the solution obtained in step S4 (PVA-AA-PDA / CCO solution), and mechanically stir (500 rpm) for 1 hour until fully mixed. Purge the reaction solution with high-purity N2 (99.999%, 50 mL / min) for 30 minutes to remove oxygen. Under a continuous N2 protective atmosphere and a 0°C ice bath environment, slowly add (0.1 mL / min) pre-cooled composite initiator (0.04 g APS + 0.04 g APS). 0.02 g AIBN was dissolved in 2.5 mL of deionized water. The reaction mixture was continuously mechanically stirred (200 rpm) at 0 °C in an ice bath for 2 h. The temperature was gradually increased to 25 °C at 0.5 °C / min (to activate AIBN) to obtain a PVA-PAA-PDA / CCO precursor solution. The precursor solution was placed at 40 °C and reacted for 96 h to generate an organic-inorganic homogeneous calcium carbonate oligomer PVA-PAA-PDA / CCO gel.

[0068] Comparative Example 1 (PVA-PAA-PDA Gel)

[0069] The difference between this comparative example and Example 1 is that step S3 (i.e., calcium carbonate oligomer gel is not added) is omitted, and in step S4, 2.0 mL of acrylic acid is directly added to the solution obtained in step S2 to obtain a PVA-AA-PDA solution; in step S5, the reaction time for the precursor solution (PVA-PAA-PDA solution) to form a gel (PVA-PAA-PDA gel) is 48 h.

[0070] Comparative Example 2 (PVA-PAA-PDA / PCC Gel)

[0071] The difference between this comparative example and Example 1 is that the calcium carbonate oligomer gel in step S3 is replaced with calcium carbonate nanoparticles (PCC, 0.6g), resulting in a PVA-PDA / PCC solution. The reaction time for the precursor solution (PVA-PAA-PDA / PCC solution) to form the gel (PVA-PAA-PDA / PCC gel) in step S5 is 72h.

[0072] Comparative Example 3 (PVA-PAA-PDA / ACC gel)

[0073] The difference between this comparative example and Example 1 is as follows:

[0074] Step S3 of this comparative example is as follows: Anhydrous calcium chloride (CaCl2, 0.6 g dispersed in 2.5 mL deionized water) solution and sodium carbonate (Na2CO3, 0.6 g dissolved in 2.5 mL deionized water) solution are placed in a 0°C refrigerated environment for 4 hours. Under continuous mechanical stirring (1000 rpm), the pre-cooled CaCl2 solution is poured into the PVA-PDA solution and stirred for 5 minutes to obtain a PVA-PDA / CaCl2 solution. Subsequently, the pre-cooled Na2CO3 solution is rapidly added to the PVA-PDA / CaCl2 solution in one go, and the mixture is vigorously stirred (1200 rpm) for 30 seconds to form a white, turbid PVA-PDA / ACC (amorphous calcium carbonate) solution.

[0075] In this comparative example, the reaction time for the precursor solution (PVA-PAA-PDA / ACC solution) to form a gel (PVA-PAA-PDA / ACC gel) in step S5 was 72 hours.

[0076] Test Example 1

[0077] The initial viscosity (shear rate 7.34 s⁻¹) of the precursor solutions of Example 1 and Comparative Examples 1-3 at 60°C was determined using a Brookfield DV-Ⅲ+Pro rotational viscometer (Brookfield Laboratories, USA). -1 The experimental results are shown in […]. Figure 2 The initial viscosities of the PVA-PAA-PDA, PVA-PAA-PDA / PCC, PVA-PAA-PDA / ACC, and PVA-PAA-PDA / CCO precursor solutions at 40℃ were 204, 252, 264, and 239 mPa·s, respectively, indicating that these composite materials are easy to inject on the ground and have good flow properties under formation conditions.

[0078] Test Example 2

[0079] Figure 3 Images of the gels from Example 1 and Comparative Examples 1-3 are shown below. Figure 3 In the figure, a1-a4 represent PVA-PAA-PDA, PVA-PAA-PDA / PCC, PVA-PAA-PDA / ACC, and PVA-PAA-PDA / CCO gels, respectively. As shown in the figure, the single organic PVA-PAA-PDA gel is light brown, highly transparent, homogeneous in texture, and has a smooth surface. The organic-inorganic composite PVA-PAA-PDA / PCC gel is light yellow with obvious particle precipitation; the PVA-PAA-PDA / ACC gel is darker in color, showing clear organic-inorganic phase separation; and the PVA-PAA-PDA / CCO gel is nearly black in color, with a smooth surface, exhibiting a continuous and homogeneous structure with eliminated organic-inorganic phases. Figure 3Image a5 shows the actual growth of CCO crystals in PVA-PAA-PDA / CCO gel. Over time (after 30 days), the volatilization of TEA induced the growth of CCO into a continuous blocky material at the centimeter scale. The directional crystallization resulted in a single calcite crystal. The gel surface appeared black and showed obvious traces of crystal growth.

[0080] Test Example 3

[0081] The PVA-PAA-PDA / CCO precursor solution was evenly applied to two substrates (wood, shale sheet, iron sheet, and steel sheet, respectively). The two substrates were then bonded together using the precursor solution. After the precursor solution air-dried naturally, its adhesion performance was tested using a lifting weight. The results are as follows: Figure 4 As shown, this indicates that it has good initial adhesion. Then, each substrate was continuously immersed in 1wt% NaCl saline solution for one day and weights were lifted. The results are as follows. Figure 5 As shown in the figure, the wooden boards, shale sheets, iron sheets, and steel sheets with PVA-PAA-PDA / CCO gel adhered to them can all successfully lift a 1kg weight. This indicates that PVA-PAA-PDA / CCO gel exhibits good underwater continuous adhesion performance. In the underwater environment, PVA-PAA-PDA / CCO gel can firmly adhere to the substrate surface.

[0082] Test Example 3

[0083] The mechanical properties of the composite materials from Example 1 and Comparative Examples 1-3 were tested using an electronic universal testing machine, and the results are as follows: Figure 6 As shown in the figure, a represents the compressive strength of each gel, and b represents the tensile strength of each gel. The figure shows that the compressive stress of the PVA-PAA-PDA / CCO gel at 85% compressive strain is 7.22 MPa, which is 2.6, 3.0, and 2.43 times that of the PVA-PAA-PDA, PVA-PAA-PDA / PCC, and PVA-PAA-PDA / ACC gels, respectively. The tensile stress and tensile strain at break of the PVA-PAA-PDA / CCO gel can reach 4.02 MPa and 348%, respectively. This indicates that the organic-inorganic continuous and uniform structure of CCO endows the PVA-PAA-PDA / CCO gel with high strength and toughness. Figure 7 The compressive strength of the PVA-PAA-PDA / CCO gel of the present invention is 1.5-166.2 times that of existing organic-inorganic composites, as demonstrated in the literature.

[0084] Test Example 4

[0085] The adhesion strength of the composite materials from Example 1 and Comparative Examples 1-3 was tested, and the test results are as follows: Figure 8As shown in the figure, the adhesion strength of PVA-PAA-PDA / CCO gel on wood, shale, iron, and steel substrates is 1.08, 0.45, 0.29, and 0.26 MPa, respectively. The adhesion strength of PVA-PAA-PDA / CCO gel is up to 21.6 times that of the carboxymethyl chitosan / calcium phosphate mineralization gel (50 kPa) disclosed in Chinese patent application CN113943430A, and 154.3 times that of the polyacrylamide-polydopamine / mesoporous silica gel (7 kPa) proposed in the article "Adhesive Hydrogel Patch with Enhanced Strength and Adhesiveness to Skin for Transdermal Drug Delivery" in the journal *Advanced Functional Materials*.

[0086] Test Example 6

[0087] Breakthrough pressure tests of the composite materials in Examples 1 and 1-3: Shale cores with fractures of 1.0 mm were sealed with the composite material, and the breakthrough pressure of CO2 in the 1.0 mm fracture cores was tested using a method of gradually increasing CO2 injection pressure. The test results are as follows: Figure 9 As shown. By Figure 9 It can be seen that the CO2 breakthrough pressure of PVA-PAA-PDA / CCO gel in a crack with an aperture of 1.0 mm is 5.63 MPa, which is 1.50, 1.33, and 1.34 times that of PVA-PAA-PDA, PVA-PAA-PDA / PCC, and PVA-PAA-PDA / ACC gels, respectively; the steady-state CO2 pressure of PVA-PAA-PDA / CCO gel in a crack with an aperture of 1.0 mm is 5.59 MPa, and it only decreases by 0.04 MPa after CO2 breakthrough. Figure 10 As shown, PVA-PAA-PDA / PCC gel and PVA-PAA-PDA / ACC gel exhibited obvious breakage, shrinkage, and debonding after CO2 breakthrough, while PVA-PAA-PDA / CCO gel maintained the integrity of the gel interior and gel-interface after CO2 breakthrough.

[0088] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall fall within the scope of the present invention.

Claims

1. A high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage, characterized in that, By mass percentage, including: 20 wt% of polyvinyl alcohol and acrylic acid monomers in a mass ratio of 1:(1-4); Polydopamine, 0.1-1.0 wt%; Calcium carbonate oligomer gel, 1.2-9.6 wt% based on effective solids content; Covalent crosslinking agent, 0.1-0.2 wt%; Sodium tetraborate, 0.05-0.1 wt%; The remainder consists of deionized water and an initiator, wherein the amount of the initiator added is 0.78-1.56 wt% of the total mass of the acrylic acid and the polydopamine.

2. The high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage as described in claim 1, characterized in that, The covalent crosslinking agent is one of N,N-methylenebisacrylamide, polyethylene glycol-400, glutaraldehyde, chromium acetate, polyethyleneimine, and phenolic crosslinking agent.

3. The high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage as described in claim 1, characterized in that, The initiator is one or a combination of ammonium persulfate, potassium persulfate, sodium bisulfite, azobisisobutyronitrile, and azobisisobutyramidine hydrochloride.

4. The high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage as described in claim 1, characterized in that, The calcium carbonate oligomer gel was prepared by a method comprising the following steps: A1. Dissolve calcium chloride dihydrate in anhydrous ethanol to form a clear calcium chloride dihydrate-ethanol solution; A2. Add triethylamine to the solution obtained in step A1 and stir magnetically at room temperature to form a mixed solution of calcium chloride dihydrate-triethylamine-ethanol. A3. Continuously introduce CO2 into the mixed solution obtained in step A2 until the system is stable, then stop the gas flow; A4. Let the system after the reaction in step A3 stand at room temperature until a light blue transparent calcium carbonate oligomer sol is observed to form, then stop the standing process. A5. Centrifuge the sol obtained in step A4, pour off the supernatant to obtain unpurified calcium carbonate oligomer gel, and wash it several times with anhydrous ethanol to fully remove residual triethylamine. A6. Disperse the unpurified calcium carbonate oligomer gel washed in step A5 again in anhydrous ethanol to form a calcium carbonate oligomer ethanol dispersion. Centrifuge the dispersion again, pour off the supernatant, and obtain the purified calcium carbonate oligomer gel. Among them, 1 mmol CaCl2·2H2O corresponds to an ethanol volume of 24.5-392.2 mL and a TEA volume of 1.35-43.1 mL.

5. The high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage as described in claim 1, characterized in that, The polydopamine is prepared by a method comprising the following steps: adding dopamine hydrochloride to a pre-cooled alkaline buffer solution, and sonicating in an ice bath until completely dissolved to obtain a dopamine solution; subjecting the dopamine solution to a self-polymerization reaction in an ice bath environment to obtain a dark brown polydopamine solution, which is then centrifuged, washed, and rotary evaporated to obtain polydopamine powder.

6. A method for preparing a high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage, used to prepare the high-strength, high-toughness, high-adhesion organic-inorganic composite material for controlling CO2 crack leakage as described in any one of claims 1-4, comprising the following steps: B1. Polyvinyl alcohol is dissolved in deionized water and stirred at high temperature to form a polyvinyl alcohol solution. Dry polydopamine powder is dispersed in deionized water and ultrasonically treated to form a polydopamine solution. The polyvinyl alcohol solution and the polydopamine solution are mixed to form a polyvinyl alcohol-polydopamine solution. B2. Calcium carbonate oligomers are dispersed in deionized water and ultrasonically treated to obtain a stable colloid. Under continuous stirring, the calcium carbonate oligomer dispersion is slowly added dropwise to the polyvinyl alcohol-polydopamine solution to form a homogeneous polyvinyl alcohol-polydopamine / calcium carbonate oligomer solution. B3. Slowly add acrylic monomer to the solution obtained in step B2 and stir thoroughly until the mixture is homogeneous to obtain an organic-inorganic blend solution of polyvinyl alcohol-acrylic acid-polydopamine / calcium carbonate oligomer. B4. Under stirring conditions, slowly add the covalent crosslinking agent solution and sodium tetraborate solution dropwise to the solution obtained in step B3, and stir thoroughly until the system is mixed evenly. B5. Purge the reaction mixture obtained in step B4 with N2 to remove oxygen. Under the protective atmosphere of continuous N2 purging, place the reaction mixture in an ice bath environment. Then, add the initiator solution dropwise to the solution. In order to achieve slow chain growth at low temperature, the reaction mixture is continuously stirred in an ice bath environment and then heated to room temperature to obtain a polyvinyl alcohol-polyacrylic acid-polydopamine / calcium carbonate oligomer precursor solution.

7. A method for applying a high-strength, high-toughness, high-adhesion organic-inorganic composite material to control CO2 crack leakage, comprising the following steps: C1. Inject the precursor solution of the high-strength, high-toughness, high-adhesion organic-inorganic composite material for treating CO2 fracture leakage as described in any one of claims 1-5 into the formation via an injection well; C2. After well shut-in, the precursor solution migrates deep to the slip fault in the caprock and comes into contact with the CO2 plume at the top of the caprock, where it undergoes in-situ ion bonding and solidification, forming a high-strength, tough, and highly adhesive sealing barrier without phase separation. C3. The solidified sealing barrier continues to grow into a continuous block and strengthens along the extensional growth. It achieves long-term underwater sealing with the shale interface through multiple synergistic bonds, preventing CO2 from floating and migrating upwards and forcing CO2 to move laterally.

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