Well cementation cement stone micro-crack self-repairing material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oil and gas well cementation engineering, in particular to a well cementation cement stone micro-crack self-repairing material and a preparation method and application thereof. The well cementation cement stone micro-crack self-repairing material is prepared from the following raw materials in parts by weight: 30 parts of deionized water, 3 to 12 parts of monomer, 0.03 to 0.09 part of cross-linking agent, 0.06 to 0.3 part of initiator, 3 to 20 parts of natural latex, 1.5 to 3 parts of surfactant and 0.03 to 1.5 parts of filler, and is prepared by adopting an emulsion copolymerization method. The obtained self-repairing material is high in liquid absorption rate in a weak acid solution, high in expansion rate when meeting carbon dioxide and excellent in mechanical property, can be doped into a well cementation fluid system, is used for two corrosive medium environments of supercritical CO2 and CO2 formation water in a water wet environment, seals a shaft leakage channel, and improves the sealing integrity of a shaft.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well cementing engineering, and in particular to a cementing cement stone micro-crack self-repairing material and a preparation method and application thereof. Background Art

[0002] The integrity of the cement ring, the integrity of the interface seal and the integrity of the cement ring corrosion are one of the key technologies to ensure the successful geological utilization and storage of carbon dioxide. During the carbon dioxide storage process, the carbon dioxide dissolved in the formation water will generate carbonic acid and decompose into carbonate, bicarbonate and hydrogen ions, making the formation water weakly acidic, which will seriously affect the performance of the oil well cement. In addition, the injection of supercritical carbon dioxide and the interface mud cake can easily cause micro-annular gaps between the cement ring and the casing or well wall, which may cause carbon dioxide formation water crossflow and carbon dioxide leakage problems.

[0003] How to prevent carbon dioxide from escaping from the wellbore after sealing is one of the key technologies that need to be studied. If self-healing materials with lower particle size are added to the cementing fluid system, when microcracks or interface micro-annuli exist in the cement stone, the self-healing materials can swell when encountering carbon dioxide formation water and carbon dioxide gas, thereby sealing the leakage channel, which is undoubtedly of great significance for the long-term sealing of carbon dioxide. However, no self-healing materials that can be used in cementing fluids to swell when encountering carbon dioxide formation water and carbon dioxide gas have been found so far. Summary of the invention

[0004] The purpose of the present invention is to develop a self-repairing material for micro-cracks in cementing cement stone, and its preparation method and application. The material has the function of expanding when encountering water and carbon dioxide gas under weak acid conditions. The self-repairing material is applied to the cementing fluid system, and has both expansion and self-repairing functions.

[0005] The well cementing cement stone micro-crack self-repairing material of the present invention comprises, by weight, 30 parts of deionized water, 3-12 parts of monomers, 0.03-0.09 parts of cross-linking agents, 0.06-0.3 parts of initiators, 3-20 parts of natural latex, 1.5-3 parts of surfactants, and 0.03-1.5 parts of fillers.

[0006] The monomer is acrylamide or diethylaminoethyl methacrylate or dimethylaminoethyl methacrylate, preferably dimethylaminoethyl methacrylate.

[0007] The cross-linking agent is N, N-methylenebisacrylamide.

[0008] The initiator is ammonium persulfate or potassium persulfate.

[0009] Natural latex comes from Taihua Rubber (Public) Co., Ltd. This latex is a viscous milky white liquid that flows out of rubber trees. At 25°C, the pH is 10.50, the ammonia content is 0.69%, and it also includes a small amount of volatile fatty acids, magnesium, etc. The solid content is 60%. Natural latex not only expands when it encounters carbon dioxide, but also improves its tensile strength.

[0010] The surfactant is a non-ionic surfactant; the non-ionic surfactant is alkylphenol polyoxyethylene ether or coconut amide polyoxyethylene ether.

[0011] The filler is hydrophilic nano silicon dioxide produced by a sol-gel method.

[0012] The present invention further provides a method for preparing a cementing cement microcrack self-repairing material, which is prepared by an emulsion copolymerization method and comprises the following steps: (1) Mix deionized water, natural rubber latex and surfactant, and stir evenly to obtain solution I; (2) Mix deionized water and filler and stir evenly to obtain solution II; (3) Mix deionized water, initiator, monomer, and crosslinking agent, and stir to dissolve to obtain solution III; (4) Add solution I and solution II to solution III and stir evenly. Under anaerobic conditions, heat to 50-80°C for static reaction. After the reaction is complete, process the product into powder, i.e., the self-healing material.

[0013] In the present invention, the product after material synthesis is in a colloidal state, and it is difficult to crush it into micron-sized particles by vacuum drying. Therefore, the present invention further studies the method of processing the product into powder according to the properties of the product. The product can be processed into powder by the following two methods: Method 1: The product is processed into powder using a centrifugal spray dryer, where the feed rate is 10% and the inlet temperature is 110°C. This method requires adding deionized water to mix into a liquid before spray drying, and the amount of powder produced in a single test is small.

[0014] Method 2: Dry and heat the product into a solid block, cut it into small pieces, add 20% of the solid mass of white carbon black for isolation, and use a liquid nitrogen pulverizer to crush it into powder at a temperature of -80~-120℃. It is preferred to use a liquid nitrogen pulverizer to crush the material twice, and the particle size after crushing twice is less than 70 mesh. In this process, the product cannot be directly crushed by a liquid nitrogen pulverizer after being heated into a solid block and cut into large particles, otherwise the large particles are easy to stick and clog the equipment. A certain amount of white carbon black must be added for isolation, and then crushed by a liquid nitrogen pulverizer.

[0015] The present invention further applies the self-repairing material to cementing fluid, and can be directly added to the cementing fluid as a component with both expansion and self-repairing functions. The self-repairing material obtained by the processing method of the present invention has a small particle size and is more evenly distributed in the cementing fluid, which not only avoids the problem that the diameter of some areas is relatively large after water absorption and expansion due to excessive particle size, affecting the performance of cement stone, but also avoids the problem that the pore structure of cement stone is affected due to excessive particle size, thereby affecting the strength.

[0016] In the present invention, the initiator decomposes into free radicals in deionized water and diffuses into micelles or initiates polymerization in latex particles. In the graft copolymerization process, the rubber molecules and monomers undergo copolymerization reaction. The core of the latex particles obtained at the end of the polymerization reaction is mainly composed of rubber molecules, and the outer layer is composed of products formed by the polymerization of graft polymers and monomers. The dimethylaminoethyl methacrylate in the material determines the expansion ratio of the self-healing material in the presence of weak acid, and the natural latex determines the expansion ratio of the self-healing material in the presence of carbon dioxide. The working principle is: the dimethylaminoethyl methacrylate in the self-healing material undergoes a tertiary amine protonation reaction in a low pH solution to produce expansion; in addition, the self-healing material contains natural latex, and when carbon dioxide gas penetrates into the self-healing material, the cross-linking network will change, thereby producing expansion.

[0017] During the material synthesis process, it was found that if the monomers used were directly mixed with latex, demulsification would occur and large colloids would be quickly generated. This is because the latex particles are negatively charged, and dimethylaminoethyl methacrylate has zwitterionic properties, which easily makes the emulsified system unstable and causes gelation. The use of surfactants can improve the stability of latex and ensure the normal progress of the synthesis reaction. Fillers can change the physical properties of the synthetic product, improve the mechanical properties of the synthetic product, and reduce costs.

[0018] The self-repairing material obtained by the present invention has a high liquid absorption rate in a weakly acidic solution, a high expansion rate when encountering carbon dioxide, and excellent mechanical properties.

[0019] Compared with the prior art, the advantages of the present invention are: The present invention adopts specific raw materials and proportions, assisted by corresponding preparation methods, to achieve the graft copolymerization of monomers and rubber molecules, and obtain a self-healing material with high liquid absorption rate in weak acidic solution, high expansion rate when encountering carbon dioxide, and excellent mechanical properties, and the preparation process is safe and reliable.

[0020] (2) The self-healing material described in the present invention can be directly applied to the cementing fluid system and used in two corrosive media environments, namely, supercritical CO2 and CO2 formation water in a wet environment, so as to seal the wellbore leakage channel and improve the sealing integrity of the wellbore. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1The expansion ratios of the self-healing materials obtained in the examples and comparative examples in solutions with different pH values; Figure 2 The expansion ratio of the self-healing material obtained in the embodiment and the comparative example when exposed to carbon dioxide; Figure 3 It is the tensile strength of the self-healing material obtained in the examples and comparative examples. DETAILED DESCRIPTION

[0022] These embodiments are provided to make the purpose and technical solution of the present invention more thorough and complete. The examples are only for explaining the present invention, and the raw materials used are all commercially available raw materials.

[0023] Example 1 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 30 g of deionized water, 5 g of acrylamide, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of natural latex, 2 g of alkylphenol polyoxyethylene ether, and 0.1 g of nano-silicon dioxide.

[0024] Its preparation method is: (1) Add 10 g of deionized water and 5 g of natural rubber latex into a beaker, add 2 g of alkylphenol polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.1 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain solution II; (3) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 5 g of acrylamide and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III. (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 6 hours. After the reaction is completed, heat the resulting product in a 100°C drying oven to form a solid block, cut it into small pieces, add 20% of the weight of the solid material of white carbon black for isolation, and then crush it into particles using a liquid nitrogen pulverizer at -100°C.

[0025] Example 2 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 30 g of deionized water, 5 g of diethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of natural latex, 2 g of cocamide polyoxyethylene ether, and 0.1 g of nano silicon dioxide.

[0026] Its preparation method is: (1) Add 10 g of deionized water and 5 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.1 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain solution II; (3) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 5 g of diethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III. (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 6 hours. After the reaction is completed, heat the resulting product in a 100°C drying oven to form a solid block, cut it into small pieces, add 20% of the weight of the solid material of white carbon black for isolation, and then crush it into particles using a liquid nitrogen pulverizer at -100°C.

[0027] Example 3 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 30 g of deionized water, 5 g of dimethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of natural latex, 2 g of cocamide polyoxyethylene ether, and 0.1 g of nano silicon dioxide.

[0028] Its preparation method is: (1) Add 10 g of deionized water and 5 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.1 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain solution II; (3) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 5 g of dimethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III. (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 6 hours. After the reaction is completed, heat the resulting product in a 100°C drying oven to form a solid block, cut it into small pieces, add 20% of the weight of the solid material of white carbon black for isolation, and then crush it into particles using a liquid nitrogen pulverizer at -100°C.

[0029] Example 4 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 30 g of deionized water, 10 g of dimethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.2 g of ammonium persulfate, 5 g of natural latex, 2 g of cocamide polyoxyethylene ether, and 0.3 g of nano silicon dioxide.

[0030] Its preparation method is: (1) Add 10 g of deionized water and 5 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.3 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain Solution II.

[0031] (3) Add 10 g of deionized water and 0.2 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 10 g of dimethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III.

[0032] (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 6 hours. After the reaction is completed, the obtained product is heated in a 100°C drying oven into a solid block and then cut into small pieces. White carbon black accounting for 20% of the mass of the solid material is added for isolation, and then crushed into particles using a liquid nitrogen pulverizer at -100°C.

[0033] Example 5 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 30 g of deionized water, 10 g of dimethylaminoethyl methacrylate, 0.09 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of natural latex, 2 g of cocamide polyoxyethylene ether, and 0.3 g of nano silicon dioxide.

[0034] Its preparation method is: (1) Add 10 g of deionized water and 5 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.5 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain Solution II.

[0035] (3) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 10 g of dimethylaminoethyl methacrylate and 0.09 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III.

[0036] (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 8 hours. After the reaction is completed, the obtained product is heated in a 100°C drying oven into a solid block and then cut into small pieces. White carbon black accounting for 20% of the weight of the solid material is added for isolation, and then crushed into particles using a liquid nitrogen pulverizer at -100°C.

[0037] Example 6 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 30 g of deionized water, 10 g of dimethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 10 g of natural latex, 2 g of cocamide polyoxyethylene ether, and 0.1 g of nano silicon dioxide.

[0038] Its preparation method is: (1) Add 10 g of deionized water and 10 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.1 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain Solution II.

[0039] (3) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 10 g of dimethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III.

[0040] (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 8 hours. After the reaction is completed, the obtained product is heated in a 100°C drying oven into a solid block and then cut into small pieces. White carbon black accounting for 20% of the weight of the solid material is added for isolation, and then crushed into particles using a liquid nitrogen pulverizer at -100°C.

[0041] Example 7 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 30 g of deionized water, 10 g of dimethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 20 g of natural latex, 2 g of cocamide polyoxyethylene ether, and 0.1 g of nano silicon dioxide.

[0042] Its preparation method is: (1) Add 10 g of deionized water and 20 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.1 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain Solution II.

[0043] (3) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 10 g of dimethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III.

[0044] (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 6 hours. After the reaction is completed, the obtained product is heated in a 100°C drying oven into a solid block and then cut into small pieces. White carbon black accounting for 20% of the mass of the solid material is added for isolation, and then crushed into particles using a liquid nitrogen pulverizer at -100°C.

[0045] Comparative Example 1 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials, in parts by weight: 30 g of deionized water, 5 g of N-(3-dimethylaminopropyl)methacrylamide, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of natural latex, 2 g of cocamide polyoxyethylene ether, and 0.1 g of nano silicon dioxide.

[0046] Its preparation method is: (1) Add 10 g of deionized water and 5 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.1 g of nano-silicon dioxide into another beaker and stir evenly with a magnetic stirrer to obtain solution II; (3) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 5 g of N-(3-dimethylaminopropyl)methacrylamide and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain solution III. (4) Add solution I and solution II to solution III and stir evenly. After deoxygenation with nitrogen, place the mixture in a 65°C water bath for 6 hours. After the reaction is completed, heat the resulting product in a 100°C drying oven to form a solid block, cut it into small pieces, add 20% of the weight of the solid material of white carbon black for isolation, and then crush it into particles using a liquid nitrogen pulverizer at -100°C.

[0047] Comparative Example 2 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 20 g of deionized water, 10 g of dimethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of natural latex, and 2 g of cocamide polyoxyethylene ether.

[0048] Its preparation method is: (1) Add 10 g of deionized water and 5 g of natural rubber latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I.

[0049] (2) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 10 g of dimethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain Solution II.

[0050] (3) Solution I was added to solution II and stirred evenly. After deoxygenation with nitrogen, the mixture was allowed to react in a 65°C water bath for 6 hours. After the reaction was completed, the obtained product was heated in a 100°C drying oven into a solid block and then cut into small pieces. White carbon black accounting for 20% of the weight of the solid material was added for isolation, and then crushed into particles using a liquid nitrogen pulverizer at -100°C.

[0051] Comparative Example 3 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 20 g of deionized water, 10 g of dimethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of styrene-butadiene latex, and 2 g of cocamide polyoxyethylene ether.

[0052] Its preparation method is: (1) Add 10 g of deionized water and 5 g of styrene-butadiene latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I.

[0053] (2) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 10 g of dimethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain Solution II.

[0054] (3) Solution I was added to solution II and stirred evenly. After nitrogen deoxygenation, the mixture was allowed to react in a 65°C water bath for 6 hours. Some white emulsion remained in the beaker. After the reaction was completed, the product was heated in a 100°C drying oven into a solid block and then cut into small pieces. White carbon black accounting for 20% of the mass of the solid material was added for isolation. The product was then crushed into granules using a liquid nitrogen pulverizer at -100°C.

[0055] Comparative Example 4 A self-repairing material for micro-cracks in cementing cement stone, comprising the following raw materials in parts by weight: 20 g of deionized water, 10 g of dimethylaminoethyl methacrylate, 0.03 g of N, N'-methylenebisacrylamide, 0.1 g of ammonium persulfate, 5 g of styrene-acrylic latex, and 2 g of cocamide polyoxyethylene ether.

[0056] Its preparation method is: (1) Add 10 g of deionized water and 5 g of styrene-acrylic latex into a beaker, add 2 g of cocamide polyoxyethylene ether and stir evenly with a magnetic stirrer to obtain solution I; (2) Add 10 g of deionized water and 0.1 g of ammonium persulfate to a reaction container and stir with a magnetic stirrer to dissolve. Then add 10 g of dimethylaminoethyl methacrylate and 0.03 g of N, N'-methylenebisacrylamide and stir evenly to obtain Solution II.

[0057] (3) Solution I was added to solution II and stirred evenly. After nitrogen deoxygenation, the mixture was allowed to react in a 65°C water bath for 6 hours. Some white emulsion remained in the beaker. After the reaction was completed, the product was heated in a 100°C drying oven into a solid block and then cut into small pieces. White carbon black accounting for 20% of the mass of the solid material was added for isolation. The product was then crushed into granules using a liquid nitrogen pulverizer at -100°C.

[0058] Experimental example The method for determining the liquid absorption rate of self-healing materials is as follows: Taking into account the application environment of self-healing materials, the test temperature of the material absorption multiple is set to 70°C. The test steps are: adjust the pH of the liquid to be tested with glacial acetic acid and sodium hydroxide respectively; moisten a 500-mesh nylon bag with the liquid to be tested; weigh a certain mass (m0) of sample particles and put them into the nylon bag, and weigh the total mass of the nylon bag and the sample (m1); pour the liquid to be tested into the container, and put the nylon bag and the sample in; take out the nylon bag after soaking for 3 days, absorb the moisture of the nylon bag with a napkin, and weigh the total mass of the nylon bag and the sample (m2). The liquid absorption expansion ratio of the self-healing material is Q=(m2-m1) / m0. The test results are as follows Figure 1 shown.

[0059] The evaluation method of the expansion ratio of self-healing materials when exposed to carbon dioxide gas is as follows: After the self-healing material is dried, it is neatly cut into small pieces, and the sample mass M1 is weighed. The length, width and height of the sample are measured with a vernier caliper and the volume V1 is calculated. Then, the sample is fixed in an intermediate container and evacuated. The intermediate container is equipped with a pressure gauge, and 5MPa CO2 gas is passed into the intermediate container. The sample is taken out after 1 day, and the sample mass M2 is weighed again. The sample mass expansion multiple P=(M2-M1) / M1. However, it was found that the mass of the samples in the embodiments and comparative examples did not change substantially after the introduction of carbon dioxide. In addition, the sample that has expanded after the introduction of carbon dioxide is placed below the liquid level of a measuring cylinder filled with a certain amount of deionized water, and the change in liquid level is observed, thereby calculating the volume expansion multiple of the self-healing material when encountering carbon dioxide gas. The test results are as follows Figure 2 shown.

[0060] The test method for the mechanical properties of self-healing materials is as follows: After drying, the self-healing material was cut into 30mm×3mm×5mm rectangular strips. The mechanical properties of the self-healing material samples were tested using a ZQ990 tensile testing machine. The maximum range of the testing machine was 2kN, the tensile rate was set to 50mm / min, the experimental environment temperature was room temperature, and 3 samples were tested in each group. The test results were averaged. The stress (σ) was calculated by dividing the test tensile force (F) by the initial cross-sectional area (S0), σ=F / S0. The test results are shown in Figure 3 shown.

[0061] From Examples 1-3, Example 7, and Comparative Examples 1-4, it can be found that the type and amount of monomer and latex have a great influence on the liquid absorption rate of the self-healing material in a weakly acidic solution. Figure 2 and Figure 3 It can be seen that the amount of natural latex added is the main factor affecting the expansion ratio and tensile strength of the self-repairing material when exposed to carbon dioxide. From Examples 3-5 and Comparative Example 2, it can be found that the amount of crosslinking agent, initiator and filler added has a certain influence on the expansion ratio and tensile strength of the self-repairing material when exposed to carbon dioxide. In Example 7, 20g of natural latex, 10g of dimethylaminoethyl methacrylate and 0.1g of nano-silica were added. The resulting self-repairing material has a high liquid absorption ratio in a weakly acidic solution, and the expansion ratio when exposed to carbon dioxide can reach more than 35 times, and the tensile strength can reach 0.7MPa.

[0062] The embodiments of the present invention are exemplary descriptions and are not limited to the disclosed contents. Without departing from the technical solution of the present invention, modifications and changes made by ordinary technicians in the technical field are still within the protection scope of the present invention.

Claims

1. A self-repairing material for micro-cracks in cementing stone, characterized in that: The raw material composition is as follows, in parts by weight: 30 parts of deionized water, 3-12 parts of monomers, 0.03-0.09 parts of crosslinking agents, 0.06-0.3 parts of initiators, 3-20 parts of natural latex, 1.5-3 parts of surfactants, and 0.03-1.5 parts of fillers.

2. The self-repairing material for micro-cracks in cementing stone according to claim 1, characterized in that: The monomer is acrylamide or diethylaminoethyl methacrylate or dimethylaminoethyl methacrylate.

3. The self-repairing material for micro-cracks in cementing stone according to claim 1, characterized in that: The cross-linking agent is N, N'-methylenebisacrylamide.

4. The self-repairing material for micro-cracks in cementing stone according to claim 1, characterized in that: The initiator is ammonium persulfate or potassium persulfate.

5. The self-repairing material for micro-cracks in cementing stone according to claim 1, characterized in that: The surfactant is a nonionic surfactant.

6. The self-repairing material for micro-cracks in cementing stone according to claim 1, characterized in that: The filler is hydrophilic nano-silicon dioxide.

7. The method for preparing a self-repairing material for micro-cracks in cementing stone according to any one of claims 1 to 6, characterized in that: The preparation is carried out by emulsion copolymerization, which comprises the following steps: (1) Mix deionized water, natural rubber latex and surfactant, and stir evenly to obtain solution I; (2) Mix deionized water and filler and stir evenly to obtain solution II; (3) Mix deionized water, initiator, monomer, and crosslinking agent, and stir to dissolve to obtain solution III; (4) Add solution I and solution II to solution III and stir evenly. Under anaerobic conditions, heat to 50-80°C for static reaction. After the reaction is complete, process the product into powder, i.e., the self-healing material.

8. The method for preparing a cementing cement microcrack self-repairing material according to claim 7, characterized in that: The product was processed into powder using a centrifugal spray dryer with a feed rate of 10% and an inlet temperature of 110°C.

9. The method for preparing a self-repairing material for micro-cracks in cementing stone according to claim 7, characterized in that: The process of processing the product into powder is as follows: drying and heating the product into a solid block, cutting it into small pieces, adding 20% ​​of the solid mass of white carbon black for isolation, and crushing it into powder using a liquid nitrogen pulverizer at a temperature of -80~-120°C.

10. Use of the cementing cement microcrack self-repairing material according to any one of claims 1 to 6 in cementing fluid.

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