阅读说明：本技术 一种用于水泥石自修复的微胶囊及其制备方法 (Microcapsule for cement stone self-repairing and preparation method thereof ) 是由 王海娟 杨军虎 孟卫东 李飞鹏 马海 秦世群 冯名正 孙武 李铁恒 赵阳 于 2021-09-27 设计创作，主要内容包括：本发明涉及一种用于水泥石自修复的微胶囊及其制备方法。本发明提供的制备方法,以丙烯酰胺为原料制备吸水膨胀自修复芯材,以碳酸钙和环氧树脂的胶结物作为壁材,原材料便宜、无污染,有效提高生产安全性并降低成本,制作工艺简单,可进行批量生产。聚丙烯酰胺芯材的吸水膨胀体积与力学强度可依据引发剂与交联剂的添加量决定,能够制备适用于不同工作环境的吸水膨胀自修复微胶囊。碳酸钙和环氧树脂的胶结物壁材具有一定的力学强度,在水泥浆制备过程中不易破碎。利用该方法制备的微胶囊,能够显著降低水泥石孔隙度,提高水泥石抗压、抗折强度,提高水泥石自愈合后抗压、抗折强度,增强水泥石自愈合能力,应用前景良好。(The invention relates to a microcapsule for self-repairing of set cement and a preparation method thereof. The preparation method provided by the invention has the advantages that the water-absorbing expansion self-repairing core material is prepared by taking acrylamide as a raw material, the cementing material of calcium carbonate and epoxy resin is taken as a wall material, the raw material is cheap and pollution-free, the production safety is effectively improved, the cost is reduced, the preparation process is simple, and the mass production can be carried out. The water-absorbing expansion volume and the mechanical strength of the polyacrylamide core material can be determined according to the addition amount of the initiator and the cross-linking agent, and the water-absorbing expansion self-repairing microcapsule suitable for different working environments can be prepared. The cementing material wall material of calcium carbonate and epoxy resin has certain mechanical strength and is not easy to break in the cement slurry preparation process. The microcapsule prepared by the method can obviously reduce the porosity of the set cement, improve the compressive strength and the flexural strength of the set cement after self-healing, enhance the self-healing capability of the set cement, and has good application prospect.)

1. The preparation method of the microcapsule for self-repairing the set cement is characterized by comprising the following steps of:

1) carrying out polymerization reaction on acrylamide, an initiator, a cross-linking agent and a surfactant in water to obtain an emulsified polymerization solution;

2) stirring and mixing the emulsified polymer solution and calcium salt to obtain calcium complex emulsion;

3) stirring and mixing the calcium complex emulsion, carbonate and epoxy resin, and then adding an epoxy resin curing agent for curing reaction to obtain microcapsule emulsion;

4) and (4) carrying out solid-liquid separation on the microcapsule emulsion, and drying the obtained solid.

2. The method according to claim 1, wherein the temperature in step 1) is controlled to be 60 ℃, and the stirring speed is 400-600 r/min; in the step 2), the temperature is controlled to be 60 ℃, and the stirring speed is 300-500 r/min; in the step 3), the stirring speed is controlled to be 100-250 r/min.

3. The method of claim 1, wherein the initiator in step 1) is potassium persulfate, the crosslinking agent is N, N-methylenebisacrylamide, and the surfactant is sodium dodecylbenzenesulfonate.

4. The method according to claim 3, wherein in step 1) the ratio of acrylamide: potassium persulfate: n, N-methylenebisacrylamide: the mass ratio of the sodium dodecyl benzene sulfonate is 1: (0.05-0.25): (0.05-1.2): (0.02-0.04).

5. The method according to claim 1, wherein the calcium salt in step 2) is calcium chloride, and the ratio of the mass of calcium chloride added to the mass of acrylamide in step 1) is (0.5-1.5): 1.

6. the method according to claim 1, wherein the carbonate and the epoxy resin are dissolved in the solvent in step 3), and the obtained solution is mixed with the calcium complex emulsion under stirring.

7. The process of claim 1, wherein the carbonate in step 3) is sodium carbonate, the epoxy resin is E-51 epoxy resin, and the curing agent is KH-792.

8. The process according to claim 7, characterized in that the ratio of the mass of sodium carbonate added in step 3) to the mass of acrylamide in step 1) is (0.5-1.5): 1; the mass ratio of the added E-51 epoxy resin to the mass of the acrylamide in the step 1) is (0.5-1): 1.

9. the method as claimed in claim 1, wherein the temperature for stirring and mixing the calcium complex emulsion, the carbonate and the epoxy resin in the step 3) is 60 ℃, the temperature is reduced from 60 ℃ to 10 ℃, and then an epoxy resin curing agent is added for curing reaction.

10. The microcapsule for cement stone self-repair is characterized by being of a core-shell structure and consisting of a core material and a wall material wrapped outside the core material, wherein the core material is polyacrylamide, and the wall material is an epoxy resin cured substance containing calcium carbonate.

Technical Field

The invention belongs to the technical field of cement stone self-repairing, and particularly relates to a microcapsule for cement stone self-repairing and a preparation method thereof.

Background

In recent years, the research and development of deepwater oil drilling and completion technology are receiving more and more attention. The current deepwater cementing technology for hydrate layers has a plurality of problems to be solved urgently.

Because the hydrate only exists stably under the conditions of high pressure and low temperature, in the process of cementing on the surface layer of the ocean deep water, the ambient temperature of the borehole rises under the influence of hydration and heat release of cementing slurry, the temperature condition of the ambient hydrate layer is changed, and the hydrate is easy to decompose. The problems of micro-annuli and other well cementation quality reduction between the well cemented cement sheath and the well wall can be caused, and the gas is continuously sprayed upwards to finally cause serious accidents; on the other hand, the decomposition of the hydrate causes the instability of the stratum in the area, if the phenomenon of collapse occurs, the whole layer can be damaged, a vicious circle is formed, the surrounding hydrate is completely decomposed, and finally, a series of problems such as failure of well cementation and the like are caused. In a deepwater stratum, stratum stress, alternating temperature stress and stress generated in the production operation process can continuously impact well cementation cement stones, so that the cement stones are damaged, microcracks and pores are generated inside a cement sheath, the integrity of the well cementation cement sheath is damaged, and gas channeling is caused. Currently, the research and application of self-repairing microcapsules in the field are relatively few.

Disclosure of Invention

The invention aims to provide a preparation method of a microcapsule for self-repairing of set cement.

The second purpose of the invention is to provide a microcapsule for self-repairing of cement stones.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of microcapsules for self-repairing of cement stones comprises the following steps:

1) carrying out polymerization reaction on acrylamide, an initiator, a cross-linking agent and a surfactant in water to obtain an emulsified polymerization solution;

2) stirring and mixing the emulsified polymer solution and calcium salt to obtain calcium complex emulsion;

3) stirring and mixing the calcium complex emulsion, carbonate and epoxy resin, and then adding an epoxy resin curing agent for curing reaction to obtain microcapsule emulsion;

4) and (4) carrying out solid-liquid separation on the microcapsule emulsion, and drying the obtained solid.

According to the preparation method of the microcapsule for cement stone self-repairing, provided by the invention, the water-absorbing swelling self-repairing core material is prepared by taking acrylamide as a raw material, the cementing material of calcium carbonate and epoxy resin is taken as a wall material, the raw materials are cheap and pollution-free, the production safety can be effectively improved, the cost is reduced, the preparation process is simple, the industrial batch production can be realized, and the cleanness and environmental friendliness in the production process are strong. The water-absorbing expansion volume and the mechanical strength of the polyacrylamide core material can be determined according to the addition amount of the initiator and the cross-linking agent, and the water-absorbing expansion self-repairing microcapsule suitable for different working environments can be prepared. The cementing material wall material of calcium carbonate and epoxy resin has certain mechanical strength and is not easy to break in the cement slurry preparation process. The microcapsule prepared by the method can effectively slow down the crack growth rate under the action of external alternate disturbance, remarkably improve the mechanical strength of the set cement, and effectively fill micro cracks generated in the set cement.

Preferably, the temperature in the step 1) is controlled to be 60 ℃, and the stirring speed is 400-600 r/min; in the step 2), the temperature is controlled to be 60 ℃, and the stirring speed is 300-500 r/min; in the step 3), the stirring speed is controlled to be 100-250 r/min.

Preferably, the initiator in the step 1) is potassium persulfate, the crosslinking agent is N, N-methylene bisacrylamide, and the surfactant is sodium dodecyl benzene sulfonate. Further preferably, the ratio of acrylamide in step 1): potassium persulfate: n, N-methylenebisacrylamide: the mass ratio of the sodium dodecyl benzene sulfonate is 1: (0.05-0.25): (0.05-1.2): (0.02-0.04).

Preferably, the calcium salt in step 2) is calcium chloride, and the mass ratio of the added calcium chloride to the mass of acrylamide in step 1) is (0.5-1.5): 1.

preferably, in the step 3), the carbonate and the epoxy resin are dissolved in the solvent, and then the obtained solution and the calcium complex emulsion are stirred and mixed.

Preferably, the carbonate in the step 3) is sodium carbonate, the epoxy resin is E-51 epoxy resin, and the curing agent is KH-792. Further preferably, the ratio of the mass of sodium carbonate added in step 3) to the mass of acrylamide added in step 1) is (0.5-1.5): 1; the mass ratio of the added E-51 epoxy resin to the mass of the acrylamide in the step 1) is (0.5-1): 1.

preferably, in the step 3), the temperature for stirring and mixing the calcium complex emulsion, the carbonate and the epoxy resin is 60 ℃, the temperature is reduced from 60 ℃ to 10 ℃, and then the epoxy resin curing agent is added for curing reaction.

The microcapsule for the cement stone self-repairing is of a core-shell structure and comprises a core material and a wall material wrapped outside the core material, wherein the core material is polyacrylamide, and the wall material is an epoxy resin cured material containing calcium carbonate.

In the hydration process of cement paste, part of wall materials are broken, the internal self-repairing core material is exposed in the cement paste, the three-dimensional cross-linked network absorbs water and expands to fill the pores near the microcapsules, and the porosity of a set cement is reduced. Meanwhile, due to the reduction of the internal porosity of the set cement, solid-phase substances bearing external loads are increased, and the compressive strength and the flexural strength of the set cement are obviously improved. When cracks are generated in the set cement, the wall materials are damaged by the microcapsules under the action of tensile stress, the internal self-repairing core materials are exposed in the set cement, the three-dimensional cross-linked network absorbs free water in the set cement, self-expansion is realized, the cracks are filled and blocked, the further development of the cracks is inhibited, and the set cement is repaired. The compression strength and the bending strength of the self-healing cement stone are obviously improved, the cement stone self-healing cement stone can be applied to the self-healing of the cement stone, the self-healing capability of the cement stone is enhanced, and the application prospect is good.

Drawings

FIG. 1 is a schematic structural diagram of a microcapsule for self-repairing of set cement provided by the present invention;

in the figure, 1-wall material; 2-core material.

Detailed Description

The invention will be further described with reference to specific embodiments, but the scope of the invention is not limited thereto.

Example 1

The embodiment provides a preparation method of a microcapsule for self-repairing of cement paste, which comprises the following steps:

(1) dissolving 5g of acrylamide, 0.25g of potassium persulfate and 0.25g of NMBA (N, N-methylene bisacrylamide) in water, heating the mixture to 60 ℃ in a water bath, stirring the mixture at a low speed for 10min by using a magnetic stirrer until the mixture is dissolved into a transparent state, adding 0.2g of surfactant sodium dodecyl benzene sulfonate, and stirring and emulsifying the mixture at the temperature of 60 ℃ for 30min by using the magnetic stirrer at the rotating speed of 500 r/min.

(2) 5g of calcium chloride is dissolved in deionized water to prepare a calcium chloride solution with 20 mass percent of solute. Slowly dropwise adding a calcium chloride solution into the solution obtained in the step 1), and stirring for 1h at the rotation speed of 350r/min by using a magnetic stirrer at the temperature of 60 ℃.

(3) Stirring 5g of sodium carbonate and 2.5g of E-51 epoxy resin in a mixed solution (volume ratio is 2: 1; the same below) of deionized water and ethanol for dissolving; slowly dripping the prepared mixed solution of the sodium carbonate and the E-51 epoxy resin into the solution obtained in the step 2), stirring by a magnetic stirrer at the rotating speed of 200r/min, controlling the temperature condition to start from 60 ℃, reducing the temperature by 5 ℃ every 10min until the temperature is reduced to 10 ℃, adding 2.5g of a curing agent KH-792, keeping the temperature at 10 ℃ and stirring at the same rotating speed for 2h to form a microcapsule emulsion.

(4) And filtering the liquid by using filter paper, washing the liquid twice by using deionized water, and drying the solid precipitate for 24 hours in an oven at the constant temperature of 30 ℃ to form dry powder, thus obtaining the microcapsule for self-repairing of the set cement.

Example 2

The embodiment provides a preparation method of a microcapsule for self-repairing of cement paste, which comprises the following steps:

(1) dissolving 5g of acrylamide, 0.5g of potassium persulfate and 0.5g of NMBA in water, heating the mixture to 60 ℃ in a water bath, stirring the mixture at a low speed for 10min by using a magnetic stirrer until the mixture is dissolved into a transparent state, adding 0.2g of surfactant sodium dodecyl benzene sulfonate, and stirring and emulsifying the mixture for 30min at the temperature of 60 ℃ by using the magnetic stirrer at the rotating speed of 500 r/min.

(2) 5g of calcium chloride is dissolved in deionized water to prepare a calcium chloride solution with 20 mass percent of solute. Slowly dropwise adding a calcium chloride solution into the solution obtained in the step 1), and stirring for 1h at the rotation speed of 350r/min by using a magnetic stirrer at the temperature of 60 ℃.

(3) Stirring and dissolving 5g of sodium carbonate and 2.5g of E-51 epoxy resin in a mixed solution of deionized water and ethanol; slowly dripping the prepared mixed solution of the sodium carbonate and the E-51 epoxy resin into the solution obtained in the step 2), stirring by a magnetic stirrer at the rotating speed of 200r/min, controlling the temperature condition to start from 60 ℃, reducing the temperature by 5 ℃ every 10min until the temperature is reduced to 10 ℃, adding 2.5g of a curing agent KH-792, keeping the temperature at 10 ℃ and stirring at the same rotating speed for 2h to form a microcapsule emulsion.

(4) And filtering the liquid by using filter paper, washing the liquid twice by using deionized water, and drying the solid precipitate for 24 hours in an oven at the constant temperature of 30 ℃ to form dry powder, thus obtaining the microcapsule for self-repairing of the set cement.

Example 3

The embodiment provides a preparation method of a microcapsule for self-repairing of cement paste, which comprises the following steps:

(1) dissolving 5g of acrylamide, 1.2g of potassium persulfate and 6g of NMBA in water, heating the mixture to 60 ℃ in a water bath, stirring the mixture at a low speed for 10min by using a magnetic stirrer until the mixture is dissolved to be transparent, adding 0.2g of surfactant sodium dodecyl benzene sulfonate, and stirring and emulsifying the mixture for 30min at the temperature of 60 ℃ by using the magnetic stirrer at the rotating speed of 500 r/min.

(2) 7.5g of calcium chloride is dissolved in deionized water to prepare a calcium chloride solution with 20 mass percent of solute. Slowly dropwise adding a calcium chloride solution into the solution obtained in the step 1), and stirring for 1h at the rotation speed of 350r/min by using a magnetic stirrer at the temperature of 60 ℃.

(3) Stirring 7.5g of sodium carbonate and 5g of E-51 epoxy resin in a mixed solution of deionized water and ethanol for dissolving; slowly dripping the prepared mixed solution of the sodium carbonate and the E-51 epoxy resin into the solution obtained in the step 2), stirring by a magnetic stirrer at the rotating speed of 200r/min, controlling the temperature condition to start from 60 ℃, reducing the temperature by 5 ℃ every 10min until the temperature is reduced to 10 ℃, adding 5g of a curing agent KH-792, and stirring at the same rotating speed for 2h while keeping the temperature at 10 ℃ to form a microcapsule emulsion.

(4) And filtering the liquid by using filter paper, washing the liquid twice by using deionized water, and drying the solid precipitate for 24 hours in an oven at the constant temperature of 30 ℃ to form dry powder, thus obtaining the microcapsule for self-repairing of the set cement.

Example 4

The embodiment provides a microcapsule for cement stone self-repair, as shown in fig. 1, the microcapsule is of a core-shell structure and is composed of a core material 2 and a wall material 1 wrapping the core material 2, the core material is polyacrylamide, and the wall material is an epoxy resin cured product containing calcium carbonate.

Test example 1

This experimental example tests the microcapsules obtained according to the process of examples 1-3, essentially comprising the following steps:

(1) the apparent morphology was observed with an optical microscope: the agglomeration of the microcapsules, the average particle size and the apparent morphology of the microcapsules in each example were observed by an optical microscope.

(2) With X-ray three-dimensional scanning system (industrial CT): under the same conditions, the microcapsules of different examples are uniformly mixed with cement ash, the mass fraction of the microcapsules is 5 percent, and the microcapsules are respectively prepared into the specification of 20mm by 20mm³Set cement, the set cement porosity of which is measured. Wherein, the voltage during CT scanning is 150kV, and the current is 65 muA.

(3) And (3) testing the influence of the mechanical property tester on the self-healing property of the set cement: mixing the microcapsules of different embodiments with cement ash uniformly to prepare standard test blocks with the specification of 40X 40mm³Fracturing to make micro cracks appear on the surface, then placing the sample in a constant temperature and humidity box for curing for 3 days (temperature: 20 ℃ and humidity: 90%), taking out the sample, and measuring the mechanical strength corresponding to each test block by using a mechanical property tester (Qingdao ZCYA-W300C). The experimental testing procedure was carried out according to the national standard for cement bond strength GBT 17671-1999. The test results were as follows:

TABLE 1 comparison of the Performance indexes of different cements

Index (I)	Blank group	Example 1	Example 2	Example 3
					Agglomeration of particles	-	Is not agglomerated	Is not agglomerated	Is not agglomerated
Particle size range (μm)	-	300～1400	250～1100	320～1300
					Cement mortar porosity (%)	47.2	42.1	43.4	42.9
Cement stone compressive strength (MPa)	17.2	17.9	17.6	19.3
					Flexural strength of cement stone (MPa)	2.5	2.6	2.4	2.8
Compressive strength after self-healing of cement stone (MPa)	13.8	17.2	17.9	15.7
					Flexural strength after self-healing of cement stone (MPa)	1.5	2.1	1.9	1.7

The microcapsule provided by the invention can obviously reduce the porosity of the set cement, obviously improve the compressive strength and the flexural strength of the set cement after self-healing, can be applied to the self-healing of the set cement, enhances the self-healing capability of the set cement, and has a good application prospect.