Carbon dioxide geological storage well cementing anticorrosion additive and application thereof

Abstract

The application discloses a kind of carbon dioxide geological storage well cementing anticorrosion additive and application.The anticorrosion additive includes the following weight parts of each component: 40~50 parts of rice hull ash, 30~50 parts of alkali-soluble acrylic resin powder, 10~30 parts of silica ash and 5~15 parts of fiber.The anticorrosion additive can significantly reduce the chemical corrosion effect of carbon dioxide on the cement stone and the stress corrosion effect under the coupling condition of stress by densification, alkali reduction, toughening and other comprehensive effects, can effectively improve the anticorrosion ability of carbon dioxide geological storage well cementing cement sheath, ensure the integrity of wellbore sealing.

Description

Technical Field

[0001] This invention belongs to the field of cement admixture materials, specifically relating to an anti-corrosion admixture used for cementing carbon dioxide geological storage wells. Background Technology

[0002] Carbon dioxide geological storage technology is the core technology of CCUS (Carbon Dioxide Sequestration System), with long-term safe storage of carbon dioxide being the most crucial aspect. This is because a large-scale carbon dioxide leak due to wellbore seal failure would lead to incalculable catastrophic consequences. Among the many factors affecting the integrity of the wellbore seal in CCUS wells, the corrosion of the cement sheath by carbon dioxide is considered the most critical. This is because cement stone itself possesses characteristics of high alkalinity (Ca(OH)₂ content greater than 15% in cement hydration products), high porosity (porosity typically greater than 25%), and high brittleness (micro-fractures developed in the cement stone), providing a thermodynamic and kinetic basis for corrosion and degradation reactions with the high temperature and pressure of downhole carbon dioxide. Severe corrosion of the cement stone manifests as increased permeability and decreased strength, causing the cement stone to lose its sealing performance, resulting in the failure of the sealing system and ultimately leading to serious consequences such as carbon dioxide burial failure.

[0003] Therefore, both domestic and international researchers attach great importance to the development of anti-corrosion admixtures for cementing carbon dioxide geological storage wells. For example, Chinese patent CN202110901764.8 discloses an anti-corrosion cement slurry system for cementing high-CO2 gas wells and its preparation method, involving anti-corrosion admixtures and anti-corrosion reinforcing agents. The anti-corrosion admixtures consist of 35 parts barite, 15 parts magnetite, 18 parts microsilica, and 32 parts fly ash; the anti-corrosion reinforcing agent consists of 50 parts modified soap-free styrene-acrylic emulsion, 35 parts modified urea-formaldehyde resin emulsion, and 15 parts silica powder. However, inert materials such as barite and magnetite have a significant impact on the strength of the cement paste, while the emulsion is highly sensitive and can only be premixed in the slurry mixing water, making on-site construction complex. Chinese patent CN202111500327.1 discloses an anti-carbon dioxide corrosion material for oil well cement. This material is produced by ball milling a mixture of magnesium olivine, manganese olivine, and calcium magnesium olivine. The milled material is then dried and pressed into test pieces. These test pieces are pre-sintered, cooled, and then pulverized to obtain powder. The powder is then calcined at high temperature and quenched with liquid nitrogen to obtain the corrosion-resistant material. However, the preparation process of this corrosion-resistant material is complex, requires sophisticated equipment, and consumes a lot of energy. Chinese patent CN202011433855.5 describes a novel CO2-EGS model high-temperature corrosion-resistant cementing system for dry hot rock, involving CO2 corrosion-resistant materials. This CO2 corrosion-resistant material is one or more of mica powder and polyetheretherketone resin ultrafine powder. However, this material has a single composition and poor performance.

[0004] Furthermore, existing technologies rarely consider the situation where cement stone is simultaneously subjected to carbon dioxide corrosion and applied stress. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0006] The technical solution of the present invention is as follows: an anti-corrosion admixture for cementing carbon dioxide geological storage wells comprises the following components in parts by weight: 40-50 parts rice husk ash, 30-50 parts alkali-soluble acrylic resin powder, 10-30 parts silica fume and 5-15 parts fiber.

[0007] Preferably, the SiO2 content in the rice husk ash is not less than 80%, and the average particle size is not greater than 25 μm.

[0008] Preferably, the alkali-soluble acrylic resin powder has an average molecular weight of 7000~15000, an acid value of not less than 180mgKOH / g, and a glass transition temperature of not less than 80℃.

[0009] Preferably, the SiO2 content in the silica fume is not less than 90%, and the average particle size is not greater than 0.3 μm.

[0010] Preferably, the fiber is one or more of basalt fiber, wood fiber, bamboo fiber, sisal fiber, nylon fiber, polypropylene fiber, and carbon fiber, and its length is not greater than 8 mm.

[0011] Preferably, the rice husk ash is obtained by heat preservation combustion and grinding.

[0012] Application of a corrosion-resistant admixture for cementing carbon dioxide geological storage wells in cementing slurry.

[0013] Preferably, when a carbon dioxide geological storage well cementing anti-corrosion admixture is used to prepare cementing slurry, the optimal dosage is 5-15% of the oil well cement mass.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) Rice husk ash and silica fume used in this invention. Since the particle size of rice husk ash is slightly smaller than that of cement particles, while the particle size of silica fume is much smaller than that of cement particles, the combination of the two when added to cement slurry can optimize the particle size distribution of the cement slurry system and form a good filling effect. In addition, both rice husk ash and silica fume have high SiO2 content and good pozzolanic effect. During the hardening process of cement slurry, the pozzolanic reaction consumes Ca(OH)2 produced by the hydration of oil well cement, forming CSH gel with cementing properties. Therefore, the filling effect and pozzolanic effect of rice husk ash and silica fume can improve the density and strength of cement stone on the one hand, and consume some of the easily corroded component Ca(OH)2 on the other hand, forming a synergistic effect of physical and chemical corrosion protection.

[0016] (2) The alkali-soluble acrylic resin used in this invention. The alkali-soluble acrylic resin contains a large proportion of carboxyl monomers. In an alkaline environment, the carboxyl groups are neutralized into carboxylate ions, which greatly enhances the hydrophilicity of the polymer molecular chain. The carboxyl-rich molecular chain segments then pull the entire molecular chain towards the aqueous phase and eventually dissolve. Well cement slurry itself is an alkaline system containing a large amount of Ca(OH)2 produced during cement hydration. The alkali-soluble acrylic resin can gradually dissolve as the well cement slurry hydration reaction proceeds. The molecular chains can fill the nanopores in the cement stone and cover the surface of cement particles, greatly improving the impermeability and corrosion resistance of the well cement stone.

[0017] (3) The fibers used in this invention. After the short chopped fibers are uniformly dispersed in the cement stone, they can form a reinforcing, crack-resistant and toughening effect. In particular, when the cement stone is subjected to stress corrosion, it can effectively reduce the stress level and prevent crack propagation, reduce the coupling effect of mechanical load and chemical corrosion, and greatly improve the corrosion resistance of the cement stone.

[0018] The corrosion-resistant admixture for cementing carbon dioxide geological storage wells provided by this invention is reliable, has a wide range of raw material sources, low overall cost, and a simple preparation process, making it suitable for large-scale industrial production and application. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] A corrosion-resistant additive for cementing carbon dioxide geological storage wells comprises the following components in parts by weight: 40-50 parts rice husk ash, 30-50 parts alkali-soluble acrylic resin powder, 10-30 parts silica fume, and 5-15 parts fiber.

[0021] In the preparation of this invention, the above materials are weighed according to the weight parts and mixed evenly.

[0022] The anti-corrosion additive in this invention can significantly reduce the chemical corrosion caused by carbon dioxide and the stress corrosion under stress coupling conditions through the comprehensive effects of densification, alkali reduction and toughening, thus effectively improving the anti-corrosion capability of cement sheath in carbon dioxide geological sealing wells and ensuring the integrity of wellbore sealing.

[0023] The rice husk ash contains no less than 80% SiO2 and has an average particle size of no more than 25 μm. The rice husk ash is obtained through heat-insulated combustion and grinding.

[0024] The alkali-soluble acrylic resin powder has an average molecular weight of 7000~15000, an acid value of not less than 180 mgKOH / g, and a glass transition temperature of not less than 80℃.

[0025] The silica fume contains no less than 90% SiO2 and has an average particle size of no more than 0.3 μm.

[0026] The fiber is one or more of basalt fiber, wood fiber, bamboo fiber, sisal fiber, nylon fiber, polypropylene fiber, and carbon fiber, and its length is no more than 8 mm.

[0027] In addition to exerting the volcanic ash effect, the rice husk ash used in this invention, as an alkaline material, can further promote the dissolution of alkali-soluble acrylic resin. At the same time, rice husk ash is rich in cellulose and lignin, which can work with fibers to reinforce cement stone.

[0028] The alkali-soluble acrylic resin in this invention can react with calcium hydroxide in cement components, consuming a large amount of the calcium hydroxide reactant that causes corrosion, thus significantly improving the corrosion resistance of cement-based materials.

[0029] Application of a corrosion-resistant admixture for cementing carbon dioxide geological storage wells in cementing slurry.

[0030] Preferably, when a carbon dioxide geological storage well cementing anti-corrosion admixture is used to prepare cementing slurry, the optimal dosage is 5-15% of the oil well cement mass.

[0031] The silica fume, rice husk ash, and alkali-soluble acrylic resin in this invention have a synergistic effect in consuming calcium hydroxide. The acid-base neutralization reaction between the alkali-soluble acrylic resin and calcium hydroxide consumes a large amount of OH-. - This causes free Ca in the cement matrix 2+ As concentration increases, free Ca 2+This further accelerates the pozzolanic reaction of silica fume and rice husk ash, and promotes the early hydration reaction of cement. The combined effect of these three factors significantly increases both the consumption rate and the amount of calcium hydroxide in the cement matrix.

[0032] The alkali-soluble acrylic resin in this invention has a composite toughening effect with the fiber. The molecular chains generated by the dissolution of the alkali-soluble acrylic resin can coat the fiber surface, further improving the strength and deformation capacity of the fiber, thereby compositely enhancing the toughness of the cement stone.

[0033] Example 1

[0034] A corrosion-resistant admixture for cementing carbon dioxide geological storage wells comprises the following components in parts by weight: 50 parts rice husk ash, 30 parts alkali-soluble acrylic resin powder, 15 parts silica fume, and 5 parts fiber. The rice husk ash contains 85.5% SiO2 with an average particle size of 15.3 μm; the alkali-soluble acrylic resin powder has an average molecular weight of 7000, an acid value of 218 mgKOH / g, and a glass transition temperature of 115℃; the silica fume contains 92.2% SiO2 with an average particle size of 0.2 μm; and the fiber is 5 mm long chopped basalt fiber.

[0035] Example 2

[0036] A corrosion-resistant admixture for cementing carbon dioxide geological storage wells comprises the following components in parts by weight: 40 parts rice husk ash, 50 parts alkali-soluble acrylic resin powder, 15 parts silica fume, and 5 parts fiber. The rice husk ash contains 89.3% SiO2 with an average particle size of 11.8 μm; the alkali-soluble acrylic resin powder has an average molecular weight of 9500, an acid value of 218 mgKOH / g, and a glass transition temperature of 117℃; the silica fume contains 92.2% SiO2 with an average particle size of 0.2 μm; and the fiber is 6 mm long chopped polypropylene fiber.

[0037] Example 3

[0038] A corrosion-resistant admixture for cementing carbon dioxide geological storage wells comprises the following components in parts by weight: 45 parts rice husk ash, 30 parts alkali-soluble acrylic resin powder, 15 parts silica fume, and 10 parts fiber. The rice husk ash contains 89.3% SiO2 with an average particle size of 11.8 μm; the alkali-soluble acrylic resin powder has an average molecular weight of 10,000, an acid value of 205 mgKOH / g, and a glass transition temperature of 115℃; the silica fume contains 94.3% SiO2 with an average particle size of 0.1 μm; and the fiber is 4 mm long bamboo fiber.

[0039] Test case

[0040] The following cement slurries were prepared: a blank group, a control group, and the example group. The specific components of each cement slurry are as follows:

[0041] Blank group cement slurry formula: 100 parts by weight of Jiahua G-grade oil well cement + 5 parts by weight of filtration loss reducer + 3 parts by weight of retarder + 0.5 parts by weight of dispersant, liquid-to-solid ratio 0.43, density 1.90 g / cm³ 3 .

[0042] The control group cement slurry formulation consisted of 100 parts by weight of Jiahua G-grade oil well cement, 5 parts by weight of filtration loss reducer, 3 parts by weight of retarder, 0.5 parts by weight of dispersant, and 10 parts by weight of SBR latex, with a liquid-to-solid ratio of 0.43 and a density of 1.90 g / cm³. 3 .

[0043] Example cement slurry formulation: 100 parts by weight of Jiahua G-grade oil well cement + 5 parts by weight of filtration loss reducer + 3 parts by weight of retarder + 0.5 parts by weight of dispersant + 8 parts by weight of anti-corrosion additive corresponding to the example, liquid-to-solid ratio 0.43, density 1.90 g / cm³ 3 .

[0044] The blank group, the control group, and the cement stone containing the anti-corrosion admixtures prepared in Examples 1-3 were placed in a high temperature and high pressure curing kettle and corroded in an 80℃ / 10MPa CO2 environment for 28 days. The corrosion depth, compressive strength, and permeability changes were tested, and the results are shown in Table 1.

[0045] Table 1 shows the test results of the effect of anti-corrosion additives on the corrosion resistance of cement stone.

[0046]

[0047] The results in the table show that, compared with the blank group, although the addition of conventional SBR latex can improve the corrosion resistance of cement stone, the corrosion resistance of cement stone is greatly improved after the anti-corrosion additive of the present invention is added to the cement slurry. The corrosion depth is only less than 50% of that of the blank group, and the change rate of strength and permeability is also significantly improved. The corrosion resistance is significantly better than that of the control group.

[0048] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A corrosion-preventing admixture for carbon dioxide geological storage well cementing, characterized by, The components include the following weight parts: 40-50 parts of rice husk ash, 30-50 parts of alkali-soluble acrylic resin powder, 10-30 parts of silica ash and 5-15 parts of fiber.

2. The corrosion-preventing admixture for carbon dioxide geological storage well cementing according to claim 1, characterized in that, The SiO2 content in the rice husk ash is not less than 80%, and the average particle size is not more than 25 um.

3. The anti-corrosion admixture for carbon dioxide geological storage well cementing according to claim 1, characterized in that, The average molecular weight of the alkali-soluble acrylic resin powder is 7000-15000, the acid value is not less than 180 mgKOH / g, and the glass transition temperature is not less than 80℃.

4. The anti-corrosion admixture for carbon dioxide geological storage well cementing according to claim 1, characterized in that, The SiO2 content in the silica ash is not less than 90%, and the average particle size is not more than 0.3 um.

5. The anti-corrosion admixture for carbon dioxide geological storage well cementing according to claim 1, characterized in that, The fiber is one or more of basalt fiber, wood fiber, bamboo fiber, sisal fiber, nylon fiber, polypropylene fiber and carbon fiber, and the length is not more than 8 mm.

6. The application of the anti-corrosion additive for carbon dioxide geological storage well cementing in the cement slurry of claim 1-5.

7. Use of an anti-corrosion admixture for carbon dioxide geological storage well cementing according to claim 6, characterized in that, The cement slurry includes oil well cement, and the mixing amount of the anti-corrosion additive for carbon dioxide geological storage well cementing is 5-15% of the mass of the oil well cement.

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