Method for improving sealing quality of CCUS well cementation interface

Abstract

The invention belongs to the technical field of oil and gas well cementation engineering, and relates to a method for improving the sealing quality of a CCUS well cementation interface. The spacer fluid contains a CO2 response type self-repairing polymer and a latent active cementing material, the corrosion-resistant cementing fluid contains a slow-release activator, the spacer fluid and the corrosion-resistant cementing fluid are matched for use, the spacer fluid can effectively disperse and destroy a cementation structure of a mud cake while washing off the drilling fluid, particles of the latent active cementing material can be adhered to the surface of rock and permeate into rock pores, and thus the drilling fluid can be effectively repaired. The corrosion-resistant well cementation fluid can effectively activate latent active gel particles remaining on the well wall to generate a three-dimensional network structure, so that a sealing structure with good cementation is formed between a cement sheath and the well wall, and the sealing quality of a well cementation interface is effectively improved. The CO2 response type self-repairing polymer can swell to repair a channeling channel when encountering CO2 gas, the effect of enhancing the interface sealing quality is achieved, and the CO2 response type self-repairing polymer has important significance on development of the carbon dioxide geological utilization and storage technology.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well cementing engineering technology, and specifically relates to a method for improving the sealing quality of CCUS cementing interface. Background Technology

[0002] Deep saline aquifers are one of the primary sites for carbon dioxide sequestration. However, the cementing interface is a weak point in the cementing system and a key factor affecting the success of carbon dioxide geological utilization and sequestration technologies. The two-interface cementing system consists of four parts: cement slurry, dead mud, filter cake, and formation. Filter cake or dead mud easily forms channeling pathways, making interface cementation quality a significant cause of annular channeling. Filter cake hinders effective contact between the cementing fluid and the wellbore, making it difficult to form a well-cemented overall structure. Filter cake formed by water-based drilling fluids is typically removed mechanically or chemically. However, blindly using mechanical or chemical methods to remove filter cake can affect wellbore stability, and wells without filter cake are prone to leakage. Cake solidification technology can improve interface cementation strength. Cake solidification technologies include slag MTC cementing technology, cake formation technology, and MSC cake solidification technology. However, because complete removal of cake is very difficult, and the solidified cake is easily damaged by external environmental factors, these methods do not fundamentally solve the annular channeling problem.

[0003] Furthermore, the core difference between the sealing interface of CO2 storage and utilization wells and conventional wells lies in the extreme environment they face, which is subject to long-term corrosion by carbon dioxide. Temperature and pressure fluctuations during CO2 injection can easily induce micro-annular gaps, thus forming channeling pathways. Therefore, the sealing interface of CO2 storage wells needs to possess long-term chemical stability and mechanical integrity. Currently, interface sealing technologies that can effectively cope with the corrosive environment of carbon dioxide and achieve self-healing of interface micro-gap are still relatively lacking. Summary of the Invention

[0004] To address the problems in the existing technology, this invention provides a method for improving the sealing quality of the CCUS cementing interface. By using this invention, the sealing quality of the cementing interface is significantly improved.

[0005] This invention discloses a method for improving the cementing quality of CCUS (Corrosion Controlled U-Shaped Joint) interfaces, characterized by the synergistic effect of a separator fluid and a corrosion-resistant cementing fluid. First, the separator fluid is used to flush away the interface mud cake and sludge deposits. Then, the corrosion-resistant cementing fluid replaces the separator fluid, achieving cementation on the interface cleaned and wetted by the separator fluid. The separator fluid contains CO2-responsive self-healing polymers and latently active cementing materials, while the corrosion-resistant cementing fluid contains a slow-release activator.

[0006] The CO2-responsive self-healing polymer is prepared by composite synergistic gel polymerization using dimethylaminoethyl methacrylate and natural latex as raw materials.

[0007] The latently active cementitious materials are submerged beads and metakaolin, with particle sizes ranging from 200 to 1000 mesh.

[0008] The slow-release activator is a mixture of sodium hydroxide, sodium phosphate, and calcium hydroxide.

[0009] Specifically, by weight, the raw material composition of the isolation fluid is as follows: 60-80 parts deionized water, 70-90 parts precipitated beads, 10-30 parts metakaolin, 0.3-0.4 parts suspension stabilizer, 0.5-1 part surfactant, 5-10 parts sodium chloride, 0.5-1 part dispersant, 0.1-0.5 parts defoamer, and 1-3 parts CO2-responsive self-healing polymer.

[0010] In this invention, the surfactant is lauramidopropyl hydroxysulfonate betaine, which has excellent solubility, compatibility and salt resistance. With its extremely low interfacial tension, it can quickly penetrate into the microcracks and particles of the mud cake, and can wash away residual drilling fluid and destroy the mud cake structure. Submerged beads and metakaolin, as latently active cementing materials with particle sizes ranging from 200 to 1000 mesh, adhere to the core surface and penetrate into the core pores. Under the action of alkaline components in subsequent corrosion-resistant cementing fluids, the latently active particles are activated, improving the interfacial cementing quality. Sodium carboxymethyl cellulose is used as a suspension stabilizer to ensure good suspension stability of the isolation fluid. In addition, sodium carboxymethyl cellulose can control the water loss of the isolation fluid. Polycarboxylic acid dispersant improves the rheological properties of the isolation fluid. During the preparation of the isolation fluid, strong mechanical stirring can introduce air and generate foam, which can affect the pumping efficiency of the isolation fluid. Defoamer can eliminate foam and ensure the performance of the isolation fluid. G603 defoamer produced by China National Petroleum Corporation Offshore Engineering Co., Ltd. can be selected. Due to the high salinity of the saline aquifer, the addition of sodium chloride can ensure wellbore stability. During the flushing process, CO2-responsive self-healing polymers in the isolation fluid will remain on the core surface. CO2-responsive self-healing polymers will swell and have a certain viscosity in the CO2 environment, improving the interfacial sealing effect.

[0011] When preparing the isolation fluid, sodium chloride is dissolved in deionized water, and then precipitated beads, metakaolin, suspension stabilizer, dispersant, CO2-responsive self-healing polymer, surfactant and defoamer are added in sequence, and the mixture is stirred evenly with a stirrer.

[0012] The CO2-responsive self-healing polymer of this invention is prepared in the laboratory by a composite synergistic gel polymerization method using dimethylaminoethyl methacrylate and latex as raw materials, and then subjected to liquid nitrogen cryogenic pulverization, with an average particle size D50 of 22.7 μm. The specific process is as follows: 40g of deionized water, 5g of dimethylaminoethyl methacrylate, 0.03g of N,N'-methylenebisacrylamide, 0.1g of potassium persulfate, 20g of natural latex, and 2g of dodecylphenol polyoxyethylene ether are used for synthesis. The synthesized product is heated into a solid block in a 100℃ drying oven, and then 20% by weight of precipitated silica is added. Finally, the mixture is pulverized and sieved using a liquid nitrogen pulverizer at -100℃ to obtain the final product.

[0013] The corrosion-resistant cementing fluid of this invention, by weight, comprises the following raw materials: 40-50 parts deionized water, 60-80 parts fly ash, 20-40 parts metakaolin, 0.5-1 parts polycarboxylate dispersant, 0.1-0.5 parts defoamer, 0.5-1.5 parts sodium gluconate, 0.2-0.4 parts sodium carboxymethyl cellulose, 12 parts sodium hydroxide, 8 parts sodium phosphate, and 5.5 parts calcium hydroxide.

[0014] The corrosion-resistant cementing fluid of this invention uses a slow-release activator to regulate its thickening properties. Calcium hydroxide is used as the alkali source precursor, and sodium phosphate is used as the sodium hydroxide generating agent. Calcium hydroxide is slightly soluble in water, and sodium phosphate and calcium hydroxide can slowly generate sodium hydroxide, appropriately extending the thickening and setting time. Simultaneously, it is necessary to ensure that the solidified body formed by the cement beads and metakaolin under alkali activation has relatively high compressive strength. Using only sodium hydroxide would cause the corrosion-resistant cementing fluid to solidify quickly, affecting pumping; using only the slow-release activator would result in excessively long setting and thickening times and low strength.

[0015] The isolation fluid of this invention utilizes a large number of spherical droplets with low density, resulting in a low reading on a rotational viscometer at 600 r / min, ensuring good rheological properties and good compatibility with corrosion-resistant cementing fluids and water-based drilling fluids. The isolation fluid has a slightly higher density than water-based drilling fluids, possessing a certain viscosity, thus creating a planar displacement effect and preventing contact contamination between cementing and drilling fluids. The isolation fluid washes away residual drilling fluid from the wellbore and disrupts the mud cake structure. The droplets and metakaolin adhering to the wellbore form a three-dimensional network structure under the action of the alkaline components in the cementing fluid, significantly improving the cementing quality. Furthermore, the CO2-responsive self-healing polymer adhering at the interface swells upon encountering CO2 gas, repairing the cross-flow channels and enhancing the interface sealing quality. This invention creates a low-permeability, corrosion-resistant, and self-healing reinforced transition zone, achieving a leap from physical isolation to chemical-mechanical synergistic protection, thereby ensuring the safety and successful implementation of CO2 geological utilization and storage projects.

[0016] Compared with the prior art, the advantages of the present invention are: (1) The isolation fluid used in this invention has good rheological properties, which can flush away residual drilling fluid and destroy the mud cake structure, form a planar propulsion displacement effect, avoid contact and contamination between cementing fluid and drilling fluid, and have good compatibility after being mixed with cementing fluid.

[0017] (2) The present invention adds a synthetic material with self-healing function to the isolation fluid. When the isolation fluid washes away the residual drilling fluid, CO2-responsive self-healing polymer particles will adhere to the well wall. The CO2-responsive self-healing polymer can swell in the carbon dioxide gas phase corrosion environment and has a certain viscosity, thereby repairing the interfacial micro-annulus.

[0018] (3) In this invention, while the isolation fluid is used to flush the mud cake and mud deposits, CO2-responsive self-healing polymer and latently active cementing material are attached to the core surface or core pores. The alkaline component in the cementing fluid used in this invention can effectively activate the latently active cementing particles remaining on the well wall. In the CO2 corrosive environment, the CO2-responsive self-healing polymer particles will swell and have a certain viscosity when they encounter CO2 gas, thereby realizing the functional design of "interface strengthening and defect self-healing". The wedge effect of the latently active particles and the swelling effect of the synthetic material are combined to achieve the effect of strengthening the interface cementing quality. Attached Figure Description

[0019] Figure 1 The results of rheological tests on the isolation fluid and corrosion-resistant cementing fluid system; Figure 2 Scanning electron microscope (SEM) images of sandstone surfaces after rinsing with mud cake and separator fluid I, and of sandstone surfaces after rinsing with separator fluid I and then solidifying with corrosion-resistant cementing fluid I. Detailed Implementation

[0020] The specific embodiments are provided to make the objectives of this invention and the existing technical solutions more thorough and complete. The embodiments are only for explaining this invention, and the cementing materials, additives, etc. used are all commercially available raw materials.

[0021] Example 1 A method for improving the sealing quality of CCUS cementing interface employs the synergistic effect of a separator fluid and a corrosion-resistant cementing fluid. First, the separator fluid is used to flush away the mud cake on the surface of the sandstone and casing. Then, the corrosion-resistant cementing fluid is used to replace the separator fluid. Cementing is achieved by curing the interface cleaned and wetted by the separator fluid at 70°C.

[0022] The raw material composition of the isolation liquid by weight is as follows: 80 parts deionized water, 80 parts sediment beads, 20 parts metakaolin, 0.3 parts sodium carboxymethyl cellulose, 1 part lauramide propyl hydroxysulfonyl betaine, 10 parts sodium chloride, 1 part polycarboxylic acid dispersant, 0.5 parts defoamer, and 1.5 parts CO2-responsive self-healing polymer, denoted as isolation liquid I.

[0023] The raw material composition of the corrosion-resistant cementing fluid by weight is as follows: 50 parts deionized water, 60 parts fly ash, 40 parts metakaolin, 1 part polycarboxylate dispersant, 0.5 parts defoamer, 1.5 parts sodium gluconate, 0.25 parts sodium carboxymethyl cellulose, 12 parts sodium hydroxide, 8 parts sodium phosphate, and 5.5 parts calcium hydroxide. This is designated as corrosion-resistant cementing fluid I.

[0024] Example 2 A method for improving the sealing quality of CCUS cementing interface employs the synergistic effect of a separator fluid and a corrosion-resistant cementing fluid. First, the separator fluid is used to flush away the mud cake on the surface of the sandstone and casing. Then, the corrosion-resistant cementing fluid is used to replace the separator fluid. Cementing is achieved by curing the interface cleaned and wetted by the separator fluid at 70°C.

[0025] The raw material composition of the isolation fluid by weight is as follows: 70 parts deionized water, 70 parts sediment beads, 30 parts metakaolin, 0.4 parts sodium carboxymethyl cellulose, 0.5 parts lauramide propyl hydroxysulfonate betaine, 5 parts sodium chloride, 0.5 parts polycarboxylic acid dispersant, 0.3 parts defoamer, and 3 parts CO2-responsive self-healing polymer, which is designated as isolation fluid II.

[0026] By weight, the raw material composition of the corrosion-resistant cementing fluid is as follows: 40 parts deionized water, 70 parts fly ash, 30 parts metakaolin, 0.7 parts polycarboxylate dispersant, 0.3 parts defoamer, 1 part sodium gluconate, 0.4 parts sodium carboxymethyl cellulose, 12 parts sodium hydroxide, 8 parts sodium phosphate, and 5.5 parts calcium hydroxide. This is designated as corrosion-resistant cementing fluid II.

[0027] Example 3 A method for improving the sealing quality of CCUS cementing interface employs the synergistic effect of a separator fluid and a corrosion-resistant cementing fluid. First, the separator fluid is used to flush away the mud cake on the surface of the sandstone and casing. Then, the corrosion-resistant cementing fluid is used to replace the separator fluid. Cementing is achieved by curing the interface cleaned and wetted by the separator fluid at 70°C.

[0028] The raw material composition of the isolation fluid by weight is as follows: 60 parts deionized water, 90 parts sediment beads, 10 parts metakaolin, 0.3 parts sodium carboxymethyl cellulose, 0.8 parts lauramide propyl hydroxysulfonate betaine, 7 parts sodium chloride, 0.7 parts polycarboxylic acid dispersant, 0.1 parts defoamer, and 1 part CO2-responsive self-healing polymer, which is designated as isolation fluid III.

[0029] By weight, the raw material composition of the corrosion-resistant cementing fluid is as follows: 45 parts deionized water, 80 parts fly ash, 20 parts metakaolin, 0.5 parts polycarboxylate dispersant, 0.1 parts defoamer, 0.5 parts sodium gluconate, 0.2 parts sodium carboxymethyl cellulose, 12 parts sodium hydroxide, 8 parts sodium phosphate, and 5.5 parts calcium hydroxide. This is designated as corrosion-resistant cementing fluid III.

[0030] Comparative Example 1 A method for improving the sealing quality of CCUS cementing interface involves the synergistic effect of a separator fluid and a corrosion-resistant cementing fluid. First, the separator fluid is used to flush away the mud cake on the surface of the sandstone and casing. Then, the corrosion-resistant cementing fluid is used to replace the separator fluid. Cementing is achieved by curing the interface cleaned and wetted by the separator fluid at 70°C.

[0031] The raw material composition of the isolation liquid by weight is as follows: 80 parts deionized water, 80 parts sediment beads, 20 parts metakaolin, 0.3 parts sodium carboxymethyl cellulose, 1 part lauramide propyl hydroxysulfonate betaine, 10 parts sodium chloride, 1 part polycarboxylic acid dispersant, and 0.5 parts defoamer, which is designated as isolation liquid IV.

[0032] The raw material composition of the corrosion-resistant cementing fluid by weight is as follows: 50 parts deionized water, 60 parts fly ash, 40 parts metakaolin, 1 part polycarboxylate dispersant, 0.5 parts defoamer, 1.5 parts sodium gluconate, 0.25 parts sodium carboxymethyl cellulose, 12 parts sodium hydroxide, 8 parts sodium phosphate, and 5.5 parts calcium hydroxide. This is designated as corrosion-resistant cementing fluid I.

[0033] Comparative Example 2 A method for improving the sealing quality of CCUS cementing interface involves first flushing the mud cake on the surface of sandstone and casing with clean water, then replacing the clean water with a corrosion-resistant cementing fluid, and finally curing the cemented interface at 70°C after it has been cleaned and moistened with clean water.

[0034] The raw material composition of the corrosion-resistant cementing fluid by weight is as follows: 50 parts deionized water, 60 parts fly ash, 40 parts metakaolin, 1 part polycarboxylate dispersant, 0.5 parts defoamer, 1.5 parts sodium gluconate, 0.25 parts sodium carboxymethyl cellulose, 12 parts sodium hydroxide, 8 parts sodium phosphate, and 5.5 parts calcium hydroxide. This is designated as corrosion-resistant cementing fluid I.

[0035] Comparative Example 3 A method for improving the sealing quality of CCUS cementing interface involves first flushing the mud cake on the sandstone and casing surfaces with a separator fluid, then replacing the separator fluid with a corrosion-resistant cementing fluid, and finally curing the interface at 70°C after it has been cleaned and moistened by the separator fluid to achieve cementation.

[0036] The raw material composition of the isolation liquid by weight is as follows: 80 parts deionized water, 80 parts sediment beads, 20 parts metakaolin, 0.3 parts sodium carboxymethyl cellulose, 1 part lauramide propyl hydroxysulfonyl betaine, 10 parts sodium chloride, 1 part polycarboxylic acid dispersant, 0.5 parts defoamer, and 1.5 parts CO2-responsive self-healing polymer, denoted as isolation liquid I.

[0037] The raw material composition of the corrosion-resistant cement slurry by weight is as follows: 55 parts deionized water, 100 parts G-grade oil well cement, 27 parts Y6000 hollow glass microspheres, 10 parts microsilica, 57 parts sedimentary beads, 2 parts 6 mm polypropylene fiber, 0.5 parts PC-X60L defoamer, 3 parts aldehyde-ketone dispersant, 4 parts BXF-200L water loss reducing agent, and 0.2 parts PC-H21L retarder.

[0038] Comparative Example 4 A method for improving the sealing quality of the CCUS cementing interface involves first flushing the mud cake on the sandstone and casing surfaces with a separator fluid, then replacing the separator fluid with a corrosion-resistant cement slurry, and finally curing the interface at 70°C after it has been cleaned and moistened with the separator fluid to achieve cementation.

[0039] The raw material composition of the isolation fluid by weight is as follows: 70 parts deionized water, 70 parts sediment beads, 30 parts metakaolin, 0.4 parts sodium carboxymethyl cellulose, 0.5 parts lauramide propyl hydroxysulfonate betaine, 5 parts sodium chloride, 0.5 parts polycarboxylic acid dispersant, 0.3 parts defoamer, and 3 parts CO2-responsive self-healing polymer, which is designated as isolation fluid II.

[0040] By weight, the raw material composition of the corrosion-resistant cement slurry is as follows: 55 parts deionized water, 100 parts G-grade oil well cement, 27 parts Y6000 hollow glass microspheres, 10 parts microsilica, 57 parts sedimentary beads, 2 parts 6mm polypropylene fiber, 0.5 parts PC-X60L defoamer, 3 parts aldehyde-ketone dispersant, 4 parts BXF-200L water loss reducing agent, and 0.2 parts PC-H21L retarder.

[0041] Basic performance tests: The rheological properties and water loss of the isolation fluid were tested according to the "Test Methods for Oil Well Cement" (GB / T 19139-2012). The suspension stability of the isolation fluid was tested by density difference. The prepared isolation fluid was poured into a cylinder equipped with a diverter valve and left to stand in a 70℃ water bath for 5 hours. A test sample was then obtained from the diverter valve, and the density difference between the upper and lower parts was measured using a hydrometer. The uniaxial compressive strength, thickening time, rheological properties, and water loss of the corrosion-resistant cementing fluid system after 1 day of curing were tested according to the "Test Methods for Oil Well Cement" (GB / T 19139-2012). The test results are shown in Table 1. The rheological test results of the isolation fluid and cementing fluid are as follows: Figure 1 As shown.

[0042] Interface bonding performance test: During the cementing interface bonding performance test, a ring-shaped casing was placed in a self-made device, and then water-based drilling fluid was poured in. Gas was introduced into the device at a pressure of 0.69 MPa, and the temperature was maintained at 70°C. After 24 hours, the drilling fluid in the self-made device was poured out, and a mud cake formed on the inner surface of the casing. During the cementing interface bonding performance test, a simulated core was prepared using a ring-shaped core preparation device, which included a core mold and a press. Epoxy resin and curing agent were mixed evenly and poured into reference sand. After grinding and sieving, the mixture was filled in six batches, pressurized, and left to stand for 24 hours before demolding. Then, the ring-shaped core and bottom sealing gasket were assembled, drilling fluid was poured into the core, and the top cover was placed on top. A pressure of 0.2 MPa was applied using a horizontal flow pump and maintained for 2 hours. After depressurization, the drilling fluid was poured out. The virgin mud cake was removed, resulting in the interface mud cake.

[0043] The interface bonding performance was tested using the shear bonding strength method. The sandstone core and casing with mud cake were rinsed with constantly stirred clean water or a prepared isolation fluid for 30 seconds, then left to stand for 5 minutes. Subsequently, corrosion-resistant cementing fluid was poured in. After curing at 70℃ for 1 day, they were removed, and the force F at interface failure was obtained using a pressure testing machine. The interface bonding strength was calculated using formula (1): ; In the formula, S The interfacial bonding strength is expressed in MPa. F The pressure at which the interface breaks, in N; D The diameter of the solidified body is in cm; H The height of the solidified body is in cm.

[0044] Interface self-healing performance evaluation: The sandstone core and casing with mud cake adhering to their surfaces were rinsed with clean water or prepared isolation fluid at a constant stirring rate for 30 seconds, and then allowed to stand for 5 minutes. Corrosion-resistant cementing fluid was then poured into the mold. The samples were cured at 70℃ for 1 day. After cutting and polishing the samples, they were placed in the testing instrument. A mechanical confining pressure of 10 MPa was applied, with the fluid pressure increasing by 0.1 MPa every 5 minutes until bubbles appeared in the measuring cylinder (filled with water) connected to the outlet pipeline. The test was then stopped. The sample with gas breakthrough at the sealing interface was then placed in an intermediate container for 3 days, and CO2 gas was introduced at a pressure of 5 MPa. The gas breakthrough pressure was then retested, with the confining pressure set to 10 MPa and the fluid pressure increasing by 0.1 MPa every 5 minutes until bubbles appeared in the measuring cylinder (filled with water) connected to the outlet pipeline. The test was then stopped, and the pressure value was recorded as the breakthrough pressure. The test results are shown in Table 2.

[0045] Table 1. Test results of the performance of the isolation fluid and corrosion-resistant cementing fluid ; According to the "Cementing Design Specification" (SY / T 5480-2016) for the oil and gas industry, the density of the separator fluid should be between 1.08 and 2.60 g / cm³. 3 Under 70℃ conditions, the water loss should be less than 250 mL / 30 min. According to the "Performance Requirements for Cement Slurry in Oil Wells" (SY / T 6544-2017), the cement slurry filtration loss for cementing in gas formation casing (tailpipe) should be less than 50 mL / 30 min, the 24-hour compressive strength should be greater than 14 MPa, and the maximum allowable density difference of the cementing fluid should be less than 0.03 g / cm³. The isolation fluid, corrosion-resistant cement slurry, and corrosion-resistant cementing fluid system designed in this invention meet the relevant technical requirements.

[0046] Table 2 Test results of cementing interface air tightness and self-healing performance ; Examples 1, 2, and Comparative Example 1 show that adding a CO2-responsive self-healing polymer to the sealing fluid improves the interfacial sealing performance. The higher the amount of CO2-responsive self-healing polymer added, the greater the gas pressure required for the interface to re-break through. The amount of CO2-responsive self-healing polymer added to the sealing fluid has little effect on the interfacial bonding strength, but it does affect the rheological properties.

[0047] As can be seen from Example 1 and Comparative Example 2, compared with water flushing, the bonding strength of the interface is improved to a certain extent after the cementing interface is flushed with the isolation fluid.

[0048] Examples 1, 2, 3, and 4 show that corrosion-resistant cementing fluid can significantly improve interfacial bonding strength compared to corrosion-resistant cement slurry.

[0049] The isolation fluid in Example 1 exhibits good rheological and suspension stability properties. When used in conjunction with a corrosion-resistant cementing fluid, the cementing interface strength reaches 4.1 MPa at the first cementing interface and 2.6 MPa at the second cementing interface, demonstrating a certain degree of self-healing function at the cementing interface.

[0050] The embodiments of the present invention are described illustratively and are not limited to the disclosed contents. Modifications and alterations made by those skilled in the art without departing from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for improving the cementing quality of CCUS cementing interfaces, characterized in that, The method employs the synergistic effect of a separator fluid and a corrosion-resistant cementing fluid. First, the separator fluid is used to flush away the interface mud cake and sludge deposits. Then, the corrosion-resistant cementing fluid replaces the separator fluid, achieving cementation on the interface cleaned and wetted by the separator fluid. The separator fluid contains CO2-responsive self-healing polymers and latently active cementing materials, while the corrosion-resistant cementing fluid contains a slow-release activator.

2. The method for improving the cementing quality of CCUS cementing interface according to claim 1, characterized in that, The CO2-responsive self-healing polymer is prepared by composite synergistic gel polymerization using dimethylaminoethyl methacrylate and natural latex as raw materials.

3. The method for improving the cementing quality of CCUS cementing interface according to claim 1, characterized in that, The latently active cementitious materials are submerged beads and metakaolin, with particle sizes ranging from 200 to 1000 mesh.

4. The method for improving the cementing quality of CCUS cementing interface according to claim 1, characterized in that, The slow-release activator is a mixture of sodium hydroxide, sodium phosphate, and calcium hydroxide.

5. A method for improving the cementing quality of CCUS cementing interface according to claim 1, characterized in that, The raw material composition of the isolation fluid by weight is as follows: 60-80 parts deionized water, 70-90 parts precipitated beads, 10-30 parts metakaolin, 0.3-0.4 parts suspension stabilizer, 0.5-1 part surfactant, 5-10 parts sodium chloride, 0.5-1 part dispersant, 0.1-0.5 parts defoamer, and 1-3 parts CO2-responsive self-healing polymer.

6. A method for improving the cementing quality of CCUS cementing interface according to claim 5, characterized in that, The surfactant is lauramidopropyl hydroxysulfonate.

7. A method for improving the cementing quality of CCUS cementing interface according to claim 1, characterized in that, The raw material composition of the corrosion-resistant cementing fluid by weight is as follows: 40-50 parts deionized water, 60-80 parts fly ash, 20-40 parts metakaolin, 0.5-1 parts polycarboxylate dispersant, 0.1-0.5 parts defoamer, 0.5-1.5 parts sodium gluconate, 0.2-0.4 parts sodium carboxymethyl cellulose, 12 parts sodium hydroxide, 8 parts sodium phosphate, and 5.5 parts calcium hydroxide.

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