Oil-swellable self-healing agent as well as preparation and application thereof

Abstract

The invention discloses an oil-swellable self-healing agent, the oil-swellable self-healing agent is a high-molecular organic-inorganic hybrid compound, the high-molecular organic compound is a styrene-acrylate polymer, and the inorganic material is a silicon dioxide and / or graphite powder material. The invention also discloses a preparation method and application of the composition. According to the self-healing agent capable of expanding when encountering oil, the oleophylic inorganic particles are added into the monomer, so that the temperature resistance and the self strength of the self-healing agent can be enhanced, and the reuse times and the temperature application range of the self-healing agent are improved. The self-healing agent provided by the invention has good dispersity when being applied to a cement paste system; and for set cement generating submillimeter-level cracks, when the set cement is in contact with oil, the permeability of the set cement can be greatly reduced, the permeability in 7 days is reduced by 40% or above, and the permeability in 28 days is reduced by 56% or above.

Description

Technical Field

[0001] The present invention relates to an oil-swelling self-healing agent and its preparation and application. Background Art

[0002] In the field of oil drilling, well cementing is a very crucial oil well engineering technology used to seal the wellbore and isolate underground fluids during oil well drilling and production. However, with the increasing proportion of unconventional oil and gas wells being developed, the geological environment where the oil wells are located becomes more and more complex, including factors such as high temperature, high pressure, geological stress, and differences in media inside and outside the well. The cured cement sheath may encounter various damages or cracks during use. These damages may lead to the loss of well cementing integrity, thereby triggering serious accidents such as oil and gas leakage or wellbore collapse, posing a threat to the environment and personnel safety, and also causing economic losses.

[0003] To solve the problem of damage to well cementing materials, self-healing agents have been introduced into the field of well cementing. A self-healing agent is a special material that has the ability to automatically repair or fill cracks when encountering damage. These self-healing properties can help maintain the integrity of well cementing materials and improve the reliability and durability of the well cementing system. Summary of the Invention

[0004] In order to further improve the performance of the oil-swelling self-healing agent and further enrich the selection space of the oil-swelling self-healing agent, the present invention is made.

[0005] As one aspect of the present invention, it relates to an oil-swelling self-healing agent, which is a polymer organic-inorganic hybrid compound. Among them, the polymer organic compound is a styrene-acrylate polymer, and the inorganic material is silica and / or graphite powder material.

[0006] As another aspect of the present invention, it relates to a method for preparing the above-mentioned oil-swelling self-healing agent, which adopts the suspension polymerization method and uses hydrophilic nano-silica as the suspending agent, including:

[0007] Adding an oil-soluble monomer and an initiator to the aqueous suspension of the suspending agent, and carrying out a polymerization reaction at a temperature above 80°C. In a specific embodiment, an oil-loving particle is further added to the aqueous suspension of the suspending agent, and the oil-loving particle is pre-mixed with the oil-soluble monomer and the initiator and then added to the aqueous suspension of the suspending agent.

[0008] In a specific embodiment, in the aqueous suspension of the suspending agent, the addition amount of the suspending agent is 1.5 - 6 wt% of the mass of water.

[0009] In a specific embodiment, the oil-soluble monomer includes:

[0010] (1) Acrylate olefin monomers containing long alkane chains: butyl methacrylate, octyl acrylate, lauryl methacrylate.

[0011] (2) Styrene-based olefin monomers containing rigid groups: styrene, p-methylstyrene, 4-tert-butylstyrene.

[0012] (3) Diacrylate crosslinking agent monomers containing multiple olefin groups: 1,4-butanediol diacrylate, ethylene glycol diacrylate, trimethylolpropane triacrylate.

[0013] (4) To increase the dispersibility of the self-healing agent in the cement slurry, hydroxyl-containing olefin monomers (hydroxyethyl methacrylate, hydroxypropyl methacrylate) are added, and their dosage accounts for 10 wt% of the total mass of the olefin monomers with long alkane chains and the rigid olefin monomers.

[0014] In specific embodiments, the lipophilic particles are lipophilic nano-silica and / or high-mesh graphite powder, and their dosage is 0 - 5 wt% of the total mass of the olefin monomers with long alkane chains and the rigid olefin monomers.

[0015] In specific embodiments, the mass ratio of the olefin monomers with long alkane chains to the rigid olefin monomers is between 1:1 and 3:1, and the addition amount of the crosslinking agent monomer is 0.25 wt% of the total mass of the olefin monomers with long alkane chains and the rigid olefin monomers.

[0016] The above oil-soluble monomers are added to the water body containing a suspending agent, and the mass ratio of the oil-soluble monomers to water is not greater than 1:5.

[0017] In specific embodiments, the initiator is benzoyl peroxide, which is mixed with the oil-soluble monomers during use, and the addition amount is 1 - 2 wt% of the oil-soluble monomers.

[0018] As another aspect of the present invention, it relates to a cement slurry containing the above oil-swelling self-healing agent.

[0019] The oil-swelling self-healing agent of the present invention introduces a variety of long alkane chains, and the oil absorption of the self-healing agent under oil conditions is greater than 4.5 g / g.

[0020] The present invention uses micro-nano particles as a suspending agent, which can improve the hydrophilicity of the self-healing agent and increase the compressive strength with cement during application.

[0021] The oil-swelling self-healing agent of the present invention adds lipophilic inorganic particles to the monomer, which can enhance the heat resistance and self-strength of the self-healing agent, and improve the number of repeated uses and the temperature application range of the self-healing agent. The self-healing agent provided by the present invention has good dispersibility in the cement slurry system; and for the cement stone with sub-millimeter cracks, when it comes into contact with oil, it can greatly reduce the permeability of the cement stone, with the permeability reduced by more than 40% in 7 days and more than 56% in 28 days. Detailed implementation mode

[0022] In the embodiment of the present invention, the product is prepared by suspension polymerization. The prepared oil-swelling self-healing agent is a polymer organic-inorganic hybrid compound. Among them, the polymer organic compound is a styrene-acrylate polymer, and the inorganic material is silica and / or graphite.

[0023] In the embodiment of the present invention, hydrophilic nano-silica is used as the suspending agent.

[0024] The oil-soluble monomers used in the embodiment of the present invention:

[0025] (1) Acrylate olefin monomers containing long alkane chains: butyl methacrylate, octyl acrylate, lauryl methacrylate.

[0026] (2) Styrene olefin monomers containing rigid groups: styrene, p-methylstyrene, 4-tert-butylstyrene.

[0027] (3) Diacrylate crosslinking agent monomers containing multiple olefin groups: 1,4-butanediol diacrylate, ethylene glycol diacrylate, trimethylolpropane triacrylate.

[0028] (4) To increase the dispersibility of the self-healing agent in the cement slurry, hydroxyl-containing olefin monomers (hydroxyethyl methacrylate, hydroxypropyl methacrylate) are added, and their dosage accounts for 10 wt% of the total mass of the olefin monomers with long alkane chains and rigid olefin monomers.

[0029] The lipophilic particles used in the embodiment of the present invention, lipophilic nano-silica and / or high-mesh graphite powder, and their dosage is 0-5 wt% of the total mass of the olefin monomers with long alkane chains and rigid olefin monomers.

[0030] The mass ratio of the olefin monomers with long alkane chains to the rigid olefin monomers is between 1:1 and 3:1, and the addition amount of the crosslinking agent monomer is 0.25 wt% of the total mass of the olefin monomers with long alkane chains and rigid olefin monomers.

[0031] The above-mentioned oil-soluble monomers are added to the water body containing the suspending agent, and the mass ratio of the oil-soluble monomers to water is not greater than 1:5.

[0032] In the embodiments of the present invention, benzoyl peroxide oil-soluble initiator is used. When in use, it is mixed with oil-soluble monomers, and the addition amount is 1-2 wt% of the oil-soluble monomers.

[0033] Example 1

[0034] Take 4 g of commercially available hydrophilic silica (TG100 from Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0035] Weigh 8 g of styrene, 6 g of butyl methacrylate, 6 g of lauryl methacrylate, 0.05 g of 1,4-butanediol diacrylate, 2 g of 2-hydroxyethyl methacrylate, and 0.3 g of benzoyl peroxide, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 85 °C for 10 h.

[0036] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0037] The product prepared in Example 1 does not contain lipophilic particles.

[0038] Example 2

[0039] Take 4 g of hydrophilic silica (TG100 from Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0040] Weigh 8 g of styrene, 6 g of butyl methacrylate, 6 g of lauryl methacrylate, 0.05 g of 1,4-butanediol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.3 g of benzoyl peroxide, and 0.3 g of 10,000-mesh graphite powder, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 85 °C for 10 h.

[0041] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0042] The product prepared in Example 2 contains lipophilic particles, and the lipophilic particles used are 10,000-mesh graphite powder.

[0043] Example 3

[0044] Take 4 g of hydrophilic silica (TG100 from Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0045] Weigh 8 g of styrene, 6 g of butyl methacrylate, 6 g of lauryl methacrylate, 0.05 g of ethylene glycol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.3 g of benzoyl peroxide, and 0.6 g of 10,000-mesh graphite powder, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 85 °C for 10 h.

[0046] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0047] The product prepared in Example 3 contains lipophilic particles, and the lipophilic particles used are graphite powder of 10,000 mesh.

[0048] Example 4

[0049] Take 4 g of hydrophilic silica (TG100, Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0050] Weigh 8 g of p-methylstyrene, 6 g of butyl methacrylate, 6 g of octyl acrylate, 0.05 g of 1,4-butanediol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.3 g of benzoyl peroxide, and 0.5 g of lipophilic nano-silica (TG96, Jingjiang Tonggao Chemical Co., Ltd.), and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 85 °C for 10 h.

[0051] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0052] The product prepared in Example 4 contains lipophilic particles, and the lipophilic particles used are lipophilic nano-silica.

[0053] Example 5

[0054] Take 6 g of hydrophilic silica (TG100, Jingjiang Tonggao Chemical Co., Ltd.) and add it to 100 g of water, and disperse it evenly by ultrasonic wave.

[0055] Weigh 10 g of 4-tert-butylstyrene, 10 g of butyl methacrylate, 0.05 g of trimethylolpropane triacrylate, 2 g of 2-hydroxypropyl methacrylate, 0.4 g of azobisisobutyronitrile, and 1 g of graphite powder of 6,000 mesh, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 90 °C for 8 h.

[0056] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0057] The product prepared in Example 5 contains lipophilic particles, and the lipophilic particles used are graphite powder of 6,000 mesh.

[0058] Example 6

[0059] Take 3 g of hydrophilic silica (TG100, Jingjiang Tonggao Chemical Co., Ltd.) and add it to 200 g of water, and disperse it evenly by ultrasonic wave.

[0060] Weigh 5 g of styrene, 15 g of lauryl methacrylate, 0.05 g of 1,4-butanediol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.2 g of azobisisobutyronitrile, and 0.3 g of graphite powder with 8000 mesh, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 80 °C for 14 h.

[0061] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0062] The product prepared in Example 6 contains lipophilic particles, and the lipophilic particles used are graphite powder with 8000 mesh.

[0063] Example 7

[0064] Take 1 g of hydrophilic silica (TG100 of Jingjiang Tonggao Chemical Co., Ltd.) and add it to 200 g of water, and disperse it evenly by ultrasonic wave.

[0065] Weigh 5 g of styrene, 15 g of lauryl methacrylate, 0.05 g of 1,4-butanediol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.2 g of benzoyl peroxide, and 0.3 g of graphite powder with 8000 mesh, mix them evenly, add them to the above water, stir evenly, at 80 °C for 14 h.

[0066] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0067] The product prepared in Example 7 contains lipophilic particles, but the particle size is too large, with an average particle size of 1 mm, which cannot meet the requirements of well cementing.

[0068] Example 8

[0069] Take 16 g of hydrophilic silica (TG100 of Jingjiang Tonggao Chemical Co., Ltd.) and add it to 200 g of water, and disperse it evenly by ultrasonic wave.

[0070] Weigh 5 g of styrene, 15 g of lauryl methacrylate, 0.05 g of 1,4-butanediol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.2 g of benzoyl peroxide, and 0.3 g of graphite powder with 10000 mesh, mix them evenly, add them to the above water, stir evenly, at 80 °C for 14 h.

[0071] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0072] The product prepared in Example 8 contains lipophilic particles, but due to the remaining excess hydrophilic silica, obvious stratification occurs in the aqueous solution, a large amount of hydrophilic silica is dispersed in the water body, and the polymerized product sinks to the bottom of the water.

[0073] Example 9

[0074] Take 4 g of hydrophilic silica (TG100 from Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0075] Weigh 4 g of 4-tert-butylstyrene, 8 g of butyl methacrylate, 8 g of lauryl methacrylate, 0.05 g of ethylene glycol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.3 g of benzoyl peroxide, and 0.6 g of 10,000-mesh graphite powder, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 85 °C for 10 h.

[0076] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0077] The product prepared in Example 9 contains lipophilic particles, but due to the too small proportion of rigid monomers, its thermal stability is poor, it is difficult to be used in high-temperature wells above 100 °C, and it cannot meet the requirements of cementing.

[0078] Example 10

[0079] Take 4 g of hydrophilic silica (TG100 from Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0080] Weigh 12 g of styrene, 4 g of butyl methacrylate, 4 g of lauryl methacrylate, 0.05 g of ethylene glycol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.3 g of benzoyl peroxide, and 0.6 g of 10,000-mesh graphite powder, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 85 °C for 10 h.

[0081] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0082] The product prepared in Example 10 contains lipophilic particles, but due to the too large proportion of rigid monomers, the oil swelling ability of the product is poor. After several oil absorption tests, there is almost no performance, and it cannot meet the cementing requirements.

[0083] Example 11

[0084] Take 4 g of hydrophilic silica (TG100 from Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0085] Weigh 8 g of styrene, 6 g of butyl methacrylate, 6 g of lauryl methacrylate, 0.05 g of ethylene glycol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.1 g of benzoyl peroxide, and 0.6 g of 10,000-mesh graphite powder, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion, at 85 °C for 10 h.

[0086] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0087] The product obtained in Example 11 contains lipophilic particles, but the amount of initiator added is too small, resulting in too high molecular weight of the formed polymer and poor continuous swelling ability in oil.

[0088] Example 12

[0089] Take 4 g of hydrophilic silica (TG100 of Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0090] Weigh 8 g of styrene, 6 g of butyl methacrylate, 6 g of lauryl methacrylate, 0.05 g of 1,4-butanediol diacrylate, 2 g of 2-hydroxyethyl methacrylate, 0.5 g of benzoyl peroxide, and 0.6 g of 10,000-mesh graphite powder, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion at 85 °C for 10 h.

[0091] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0092] The product obtained in Example 12 contains lipophilic particles, but the initiator is in excess, resulting in too low molecular weight of the polymer and poor swelling performance in oil.

[0093] Example 13

[0094] Take 4 g of hydrophilic silica (TG100 of Jingjiang Tonggao Chemical Co., Ltd.) and add it to 160 g of water, and disperse it evenly by ultrasonic wave.

[0095] Weigh 24 g of styrene, 8 g of butyl methacrylate, 8 g of lauryl methacrylate, 0.1 g of ethylene glycol diacrylate, 4 g of 2-hydroxyethyl methacrylate, 0.6 g of benzoyl peroxide, and 1.2 g of 10,000-mesh graphite powder, and mix them evenly. Add them to the above water, stir evenly to form a pre-emulsion at 85 °C for 10 h.

[0096] Cool to room temperature, filter, wash the particles and dry them at room temperature.

[0097] The product obtained in Example 13 contains lipophilic particles, but the ratio of polymerization monomer to water is too high, and suspension adhesion occurs during the polymerization process, resulting in uneven particle size distribution of the synthesized product, with the maximum particle size reaching 1 mm, which cannot meet the requirements of well cementing.

[0098] Based on the performance of the products prepared in each example, the products obtained in Examples 1 to 6 are used as self-healing agents.

[0099] Performance test of each example:

[0100] (1) Wettability test:

[0101] Take the samples of each example, adhere them to the glass slide, and place them on a static contact angle measuring instrument to measure the contact angle.

[0102] And place the samples of each example in a mixed solution of water and ethanol of hydrofluoric acid (100 mL of 2 wt% hydrofluoric acid aqueous solution and 10 mL of ethanol) to remove the silica particles on the surface, and then conduct the contact angle measurement.

[0103] The contact angle measurement results are shown in Table 1.

[0104] Table 1:

[0105]

[0106]

[0107] (2) Oil absorption test:

[0108] Take 5 g of each sample of each example respectively, immerse them in kerosene and octane respectively, wait for 0.5 hour, filter and weigh, calculate the mass of the oil phase absorbed by the comparative example and the samples of each example, and test the number of times the samples of each example can be reused with kerosene as the medium.

[0109] The measurement results are shown in Table 2.

[0110] Table 2:

[0111]

[0112] Note: The "-" in Examples 9 and 12 indicates that the sample dissolved in kerosene and there was no solid substance after filtration.

[0113] (3) Thermal stability test:

[0114] The initial temperature of thermal weight loss can be used to represent the initial temperature when the material decomposes, so it can be used to represent the thermal stability of the material. The initial temperature of thermal weight loss of each example is shown in Table 3.

[0115] Table 3:

[0116]

[0117] Cement slurry performance test:

[0118] Referring to the National Standard of the People's Republic of China GB / T 19139-2012 "Test Methods for Oil Well Cement", the self-healing agents of Examples 1 to 6 were formulated into cement slurries, and the performance evaluation was carried out at 80 °C. The results are shown in Table 4.

[0119] Table 4:

[0120]

[0121] The formulation is Class G oil well cement (Jiahua) + 2.5% fluid loss reducer + self-healing agent (dosage as shown in Table 3) + 44% water. The measurement of fluid loss is carried out under the condition of 80°C. The sedimentation density difference is carried out under the condition of 80°C. The thickening conditions are 80°C, 35 MPa, and the heating and pressure increasing time is 40 min.

[0122] Performance testing of cement stone

[0123] Referring to the national standard of the People's Republic of China GB / T 19139-2012 "Test Methods for Oil Well Cement" and SY-T6466-2016 "Test Methods for Performance of Oil Well Cement Stone", the self-healing agents of Examples 1 to 6 were added to the cement slurry, and the performance of the formed cement stone was evaluated. The cement slurry containing the self-healing agent of the present invention (density 1.90 g / cm 3 ) was placed in a strength module (5.08 cm * 5.08 cm * 5.08 cm) and cured for 1 day and 7 days at a test temperature of 80°C, and its strength was measured. The results are shown in Table 5.

[0124] Table 5:

[0125]

[0126] The strengths of each example after removing the silica particles on the surface of the self-healing agent are shown in Table 6.

[0127] Table 6:

[0128]

[0129] The cement slurry containing the self-healing agent of the present invention (density 1.90 g / cm 3 ) was placed in a cylindrical mold (inner diameter 2.5 cm, length 5 cm), cured for 2 days at 80°C, a crack was made using the Brazilian splitting method, the crack width was measured, and it was cured for 1 day in a kerosene medium at 80°C. The permeability of the cured cement stone was tested. The results are shown in Table 7.

[0130] Table 7:

[0131]

[0132] Based on the above embodiments, it can be seen that Embodiments 2 to 13 all contain lipophilic particles compared to Embodiment 1, and the difference between Embodiment 2 and Embodiment 1 lies only in this. The products formed in Embodiment 2 are better than those formed in Embodiment 1 in terms of the oil-swelling persistence ability and thermal stability, indicating that the addition of lipophilic particles helps to improve the thermal stability of the products; however, the thermal stability of the products formed in Embodiment 9 and Embodiment 12 is lower than that of the product in Embodiment 1, indicating that although lipophilic particles contribute to improving the thermal stability, the final thermal stability of the products is also related to the type and proportion of oil-soluble monomers and the dosage of initiators. Among the embodiments, the products prepared in Embodiments 1 to 6 have good thermal stability, and the oil-swelling property is still greater than 4.5 g / g after multiple uses, indicating their excellent swelling property and durability. By comparing Embodiment 6 with Embodiments 7 and 8, it is found that adjusting the dosage of the suspending agent in water has a great influence on the particle size and uniformity of the formed products. Too small a dosage results in too large particle size of the products, while too large a dosage leads to the remaining of some suspending agents. Therefore, the dosage of the suspending agent should be controlled at 1.5 - 6 wt% of the water quality; by comparing Embodiment 3 with Embodiments 9 and 10, too high or too low mass ratio of the olefin monomer with long alkane chain to the rigid olefin monomer will affect the performance of the prepared products. Therefore, the mass ratio of the olefin monomer with long alkane chain to the rigid olefin monomer should be controlled between 1:1 and 3:1; by comparing Embodiment 3 with Embodiments 11 and 12, too high or too low dosage of the initiator will reduce the oil-swelling performance of the products. Therefore, its dosage accounts for 1 - 2 wt% of the sum of the masses of the olefin monomer with long alkane chain and the rigid olefin monomer. It can be seen from Embodiment 13 that the ratio of the oil-soluble monomer to water should not be too large, not greater than 1:5. By removing the surface particles of the self-healing agent synthesized in Embodiments 1 to 6 and making comparisons, it is found that hydrophilic silica as a suspending agent can appropriately reduce the contact angle of the self-healing agent, improve the hydrophilicity, and contribute to enhancing the strength of the cement stone. The thickening curves of the cement slurries prepared with the self-healing agents formed in each embodiment at various dosages are normal, indicating that they have a relatively wide range of applications and can be increased or decreased according to the actual situation.

Claims

1. An oil-swelling self-healing agent, Characterized in that, The oil-swelling self-healing agent is a polymer organic-inorganic hybrid compound, wherein the polymer organic compound is a styrene-acrylate polymer, and the inorganic material is silica and / or graphite powder material.

2. A method for preparing the oil-swelling self-healing agent according to claim 1, Characterized in that, The method adopts a suspension polymerization method, using hydrophilic nano-silica as a suspending agent, including: Adding an oil-soluble monomer and an initiator to the aqueous suspension of the suspending agent, and carrying out a polymerization reaction at a temperature above 80 °C.

3. The method according to claim 2, Characterized in that, An oil-loving particle is further added to the aqueous suspension of the suspending agent, and the oil-loving particle is pre-mixed with the oil-soluble monomer and the initiator and then added to the aqueous suspension of the suspending agent.

4. The method according to claim 3, Characterized in that, In the aqueous suspension of the suspending agent, the addition amount of the suspending agent is 1.5-6 wt% of the mass of water.

5. The method according to claim 3, Characterized in that, The oil-soluble monomers include: (1) Acrylate olefin monomers containing long alkane chains, preferably butyl methacrylate, octyl acrylate and / or lauryl methacrylate; (2) Styrene-based olefin monomers containing rigid groups, preferably styrene, p-methylstyrene and / or 4-tert-butylstyrene; (3) Diacrylate cross-linking agent monomers containing multiple olefin groups, preferably 1,4-butanediol diacrylate, ethylene glycol diacrylate and / or trimethylolpropane triacrylate; (4) Hydroxy-containing olefin monomers, preferably 2-hydroxyethyl methacrylate and / or 2-hydroxypropyl methacrylate.

6. The method according to claim 5, Characterized in that, The oil-loving particles are oil-loving nano-silica and / or graphite powder with a particle size of 6000-10000 mesh, and the dosage is 0-5 wt% of the sum of the masses of the acrylate olefin monomers containing long alkane chains and the styrene-based olefin monomers containing rigid groups.

7. The method according to claim 5, Characterized in that, The mass ratio of the acrylate olefin monomers containing long alkane chains to the styrene-based olefin monomers containing rigid groups is between 1:1 and 3:1, and the addition amount of the diacrylate cross-linking agent monomers containing multiple olefin groups is 0.25 wt% of the total mass of the acrylate olefin monomers containing long alkane chains and the styrene-based olefin monomers containing rigid groups.

8. The method according to claim 3, Characterized in that, The mass ratio of the oil-soluble monomer to water is not greater than 1:

5.

9. The method according to claim 3, Characterized in that, The initiator is benzoyl peroxide, and the addition amount is 1-2 wt% of the oil-soluble monomer.

10. A cement slurry, Characterized in that, It contains the oil-swelling self-healing agent according to claim 1.

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