Temperature and pressure response type plugging empty capsule as well as preparation method and application thereof

Abstract

The invention discloses a temperature and pressure response type plugging hollow capsule as well as a preparation method and application thereof, and belongs to the technical field of oil and gas field development and crack repair. The temperature and pressure response type plugging empty capsule is prepared from the following raw materials in parts by weight: 70 to 90 parts of polymer monomer, 5 to 15 parts of initiator, 5 to 15 parts of dispersing agent, 8 to 12 parts of metal oxide, 1 to 3 parts of oleophylic modifier, 1 to 3 parts of stabilizer and 90 to 110 parts of water. The invention further discloses a preparation method and application of the temperature and pressure response type plugging empty capsule. The temperature and pressure response type plugging hollow capsule has the temperature and pressure response characteristic, integrated intelligent response to the underground complex temperature and pressure environment can be achieved, the accuracy of the plugging behavior under the high-temperature condition is ensured, and therefore the efficient, accurate and reliable plugging purpose is achieved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development and fracture repair technology, specifically relating to a temperature and pressure responsive sealing hollow capsule, its preparation method and application. Background Technology

[0002] For the problems of annular pressure and downhole tubing seal failure in offshore oil and gas wells, the repair technologies currently commonly used in the industry can be mainly divided into two categories: traditional mechanical repair and chemical injection repair.

[0003] Traditional mechanical repair techniques mainly involve using mechanical tools such as packers, slips, and expansion tubes to physically seal the leak. While these techniques can restore the seal in a short period of time in some scenarios, their construction usually relies on large workover equipment and complex downhole operations, requiring multiple procedures such as running and pulling the tubing string and positioning and setting the seal. This results in problems such as long operation cycles, high costs, and high requirements for wellbore conditions. Especially in deepwater, high-temperature and high-pressure wells, it is difficult to run mechanical tools, and the reliability of the setting seal is significantly affected by well inclination, temperature, and corrosion. It is prone to failure again due to aging of sealing elements or fluctuations in operating conditions, and it is often unable to effectively deal with complex leakage patterns such as micro-gap and multi-point leakage. Another mainstream technology is chemical injection repair, with common materials including cement slurry, polymer gel, and resin. These are pumped into the annulus or leak channel and cured to form a barrier. However, most existing injection materials are static curing systems, heavily reliant on manual adjustment of pumping parameters and external activation (such as adding accelerators). They have poor adaptability to the dynamic temperature and pressure environment downhole, and are prone to premature curing or delayed hardening due to fluid flow erosion and temperature / pressure changes, resulting in inaccurate sealing locations or insufficient strength. Furthermore, conventional cement-based materials are highly brittle and prone to microcracks under continuous temperature cycling and formation creep. Organic polymers, on the other hand, have limited temperature and pressure resistance, poor long-term stability, and insufficient bonding strength with the metal / cement sheath interface. These materials generally lack intelligent response capabilities to complex downhole temperature and pressure conditions, leading to low first-time sealing success rates and a high risk of repeated leaks due to material degradation or interface failure, resulting in incomplete remediation.

[0004] Overall, existing repair methods all suffer from core defects such as cumbersome construction processes, high operational risks, poor economic efficiency, and limited adaptability. In particular, there is a lack of a high-performance plugging material that can automatically activate, precisely expand, and provide long-term sealing based on the well's own temperature and pressure conditions. Existing technologies are unable to meet the needs of efficient, safe, and low-cost annular pressure treatment for offshore production wells, thus hindering the improvement of oil and gas well integrity management and safe production levels under high-temperature conditions.

[0005] Therefore, developing a new type of intelligent material that can adapt to high temperature and high pressure environments and utilize downhole temperature and pressure differences to achieve self-activation and adaptive plugging has become a key direction for breaking through current technological bottlenecks. Summary of the Invention

[0006] The problem this invention aims to solve is to provide a thermo-baric responsive plugging hollow capsule, its preparation method, and its application, in order to address the issues of slow plugging efficiency, plugging strength failure, and low plugging success rate of existing plugging agents under high-temperature conditions.

[0007] The technical solution adopted to solve the technical problem is to provide a temperature and pressure responsive sealing hollow capsule, comprising the following raw materials in parts by weight: 70-90 parts of polymer monomer, 5-15 parts of initiator, 5-15 parts of dispersant, 8-12 parts of metal oxide, 1-3 parts of lipophilic modifier, 1-3 parts of stabilizer and 90-110 parts of water; The polymer monomer is at least one of styrene, divinylbenzene and methyl methacrylate; the initiator is potassium persulfate or benzoyl peroxide; the dispersant is a surfactant; the metal oxide is nano-calcium oxide, nano-iron oxide or nano-zinc oxide; the lipophilic modifier is stearic acid or oleic acid; and the stabilizer is an inorganic salt solution.

[0008] The beneficial effects of the above-mentioned technical solution of this invention are as follows: The thermo-pressure responsive sealing hollow capsule of this invention exhibits a spherical structure with a hollow core, and its glass transition temperature is above 100℃. Above this temperature, the thermo-pressure responsive sealing hollow capsule changes from a glassy state to a viscoelastic state, possessing a pressure-activated sealing effect at the leakage point. Its hollow structure, combined with the design concept of mechanically responsive metamaterials, enhances the pressure activation effect. Under pressure, the gas in the internal cavity escapes, causing the overall Young's modulus of the material to increase. The low Young's modulus outside the leakage point helps the sealing agent enter the leakage point, while the high Young's modulus after entering the leakage point helps improve the sealing strength of the leakage point. Furthermore, the metal oxide further improves the intrinsic hardness of the material, thereby assisting in improving the sealing strength of the leakage point. The nano-metal oxide provides the polymer microspheres with properties that reduce interfacial tension during synthesis, thus forming a hollow layer encapsulating gas / water / pharmaceutical during synthesis. The formed three-dimensional cross-linked network can prevent the polymer from being crushed under high temperature and pressure, and the highly elastic state further enhances airtightness, preventing liquid leakage. The temperature- and pressure-responsive sealing hollow capsule of the present invention is a spherical particle when dried, and a suspension when prepared as a fluid. It can be used after being ultrasonically dispersed into a turbid liquid.

[0009] Meanwhile, the thermo-pressure responsive sealing hollow capsule of the present invention may also include 10 to 25 parts of core additive. The core additive is wrapped inside the thermo-pressure responsive sealing hollow capsule. When the capsule seals the leak point, the capsule can release the internal core additive to provide additional effects. The core additive can be a phase change repair agent, tracer, nano probe, density regulator or rigid nano bridging agent, which can be selected and added as needed according to actual requirements.

[0010] Preferably, the thermo-pressure responsive sealing hollow capsule comprises the following raw materials in parts by weight: 80 parts polymer monomer, 10 parts initiator, 10 parts dispersant, 10 parts metal oxide, 2 parts lipophilic modifier, 2 parts stabilizer, and 100 parts water.

[0011] More preferably, the particle size of the metal oxide is 60~100 nm.

[0012] More preferably, the particle size of the metal oxide is 80 nm.

[0013] More preferably, the surfactant is sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, or polyvinyl alcohol; and the inorganic salt solution is sodium chloride solution, magnesium chloride solution, or copper chloride solution.

[0014] More preferably, the mass concentration of the inorganic salt solution is 15-25%.

[0015] More preferably, the inorganic salt solution has a mass concentration of 20%.

[0016] This invention also provides a method for preparing the above-mentioned temperature and pressure responsive sealing hollow capsule, comprising the following steps: (1) Dissolve the lipophilic modifier in an organic solvent, then add the metal oxide and stir to obtain a lipophilic modified metal oxide solution; (2) Mix the polymer monomer, the lipophilic modified metal oxide solution and the initiator to obtain an oil phase polymer monomer solution; (3) Dissolve the dispersant in water, then add the oil phase polymer monomer solution dropwise. After the addition is complete, add the stabilizer and stir to obtain an oil-in-water suspension. (4) The water-in-oil suspension is subjected to polymerization reaction and washed to obtain the final product.

[0017] Preferably, the organic solvent in step (1) is anhydrous ethanol; the stirring temperature is 40~90℃, the stirring speed is 500~900 r / min, and the time is 15~25 min.

[0018] Preferably, in step (1), the stirring temperature is 40°C, the stirring speed is 500 r / min, and the time is 20 min.

[0019] More preferably, the weight ratio of the lipophilic modifier to the organic solvent is 1 to 3:20.

[0020] Preferably, in step (3), the drop acceleration rate is 0.05~0.2 g / s; and the stirring speed is 500~900 r / min.

[0021] More preferably, in step (3), the droplet acceleration rate is 0.1 g / s and the stirring speed is 500 r / min.

[0022] Preferably, the polymerization reaction in step (4) is carried out under stirring conditions, with a stirring speed of 500~900 r / min, a temperature of 40~90℃, and a time of 2.5~3.5 h.

[0023] More preferably, in step (4), the polymerization reaction is carried out under stirring conditions, with a stirring speed of 500 r / min, a temperature of 80℃, and a time of 3 h.

[0024] The present invention also provides the application of the above-mentioned temperature and pressure responsive sealing hollow capsule in the repair of micro-leakage in cracks.

[0025] The present invention also provides the application of the above-mentioned temperature and pressure responsive plugging hollow capsule in the repair of micro-leakage in downhole tubing fractures.

[0026] The present invention has the following beneficial effects: The thermo-pressure responsiveness of the hollow plugging capsule provided by this invention stems from the synergistic effect of its components. Regarding temperature response, the selected polymer monomers and initiator system possess specific activation temperature thresholds, enabling efficient activation within the target downhole temperature range. Simultaneously, the addition of metal oxides not only provides reinforcement but also contributes to uniform heat transfer within the system, ensuring consistent response. Regarding pressure response, once the glass transition temperature is exceeded, the polymer transitions from a glass stage to a viscoelastic state. At this point, the combined action of the lipophilic modifier, stabilizer, and the unique structure of the hollow capsule imparts specific rheological properties to the initial colloidal system, maintaining stable suspension and fluidity under static or low-pressure conditions. Once a significant pressure differential is encountered at the leak point, shearing action triggers a rapid change in the colloidal rheological state, causing the material to rapidly accumulate, remain, and seal at the leak point. More importantly, the microscopic hollow spherical structure inside the capsule constitutes a pressure-sensitive amplification mechanism. Under the influence of external pressure differentials, this structure can deform or collapse, thereby accelerating the release and contact of internal reactive components. This significantly improves the material's detection sensitivity to minute pressure fluctuations and the plugging trigger speed. This invention achieves integrated intelligent response to complex downhole temperature and pressure environments, ensuring that plugging behavior is precisely activated only under target temperature and pressure conditions, i.e., at the leak point, thus achieving efficient, accurate, and reliable plugging. Attached Figure Description

[0027] Figure 1 The images show the appearance of the temperature-pressure responsive sealing hollow capsule; (a) is a fluid diagram of the temperature-pressure responsive sealing hollow capsule prepared in Comparative Example 1; (b) is a fluid diagram of the temperature-pressure responsive sealing hollow capsule prepared in Example 1; and (c) is an appearance diagram of the temperature-pressure responsive sealing hollow capsule prepared in Example 1 after drying. Figure 2 The above is a comprehensive thermal analysis diagram of the thermo-baric responsive sealing hollow capsule prepared in Example 1; Figure 3 The diagram shows the performance evaluation of the thermo-pressure responsive plugging hollow capsule in Example 1; where (a) is the head dimension of the rubber nail formed after the thermo-pressure responsive plugging hollow capsule plugs a 0.5 mm diameter crack; and (b) is the tail dimension of the rubber nail formed after the thermo-pressure responsive plugging hollow capsule plugs a 0.5 mm diameter crack. Figure 4 The graph shows the sealing strength test results of the thermo-pressure responsive sealing hollow capsule of Example 1 for leak points with pore sizes of 0.5 mm and 1 mm. Figure 5 The graph shows the sealing strength test results of the thermo-pressure responsive sealing hollow capsule for leakage points with 0.5 mm and 1 mm pore diameters, as shown in Comparative Example 1. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0029] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0031] Example 1 A thermo-pressure responsive sealing hollow capsule comprises the following raw materials in parts by weight: 60 parts styrene, 20 parts divinylbenzene, 10 parts benzoyl peroxide, 10 parts sodium dodecylbenzenesulfonate, 10 parts nano-iron oxide with a particle size of 80 nm, 2 parts stearic acid, 2 parts magnesium chloride solution with a mass concentration of 20%, and 100 parts deionized water.

[0032] The thermo-barotropic sealing hollow capsule in this embodiment is prepared through the following steps: (1) Dissolve stearic acid in 20 parts by weight of anhydrous ethanol, then add nano-iron oxide, and stir at 500 r / min for 20 min at 40℃ to obtain a lipophilic modified metal oxide solution. (2) Styrene, divinylbenzene, lipophilic modified metal oxide solution and benzoyl peroxide are mixed to obtain an oil phase polymer monomer solution; (3) Sodium dodecylbenzenesulfonate was dissolved in deionized water, and then an oil-phase polymer monomer solution was dropped at a rate of 0.1 g / s. After the drop was completed, magnesium chloride solution was added and stirred at a speed of 500 r / min to obtain an oil-in-water suspension. (4) Under stirring conditions of 500 r / min, the oil-in-water suspension was subjected to polymerization reaction at 80℃ for 3 h. The precipitate was screened out and washed with deionized water to obtain the final product.

[0033] Example 2 A thermo-pressure responsive sealing hollow capsule comprises the following raw materials in parts by weight: 80 parts styrene, 10 parts benzoyl peroxide, 10 parts sodium dodecylbenzenesulfonate, 10 parts nano zinc oxide with a particle size of 80 nm, 2 parts stearic acid, 2 parts magnesium chloride solution with a mass concentration of 20%, and 100 parts deionized water.

[0034] The thermo-barotropic sealing hollow capsule in this embodiment is prepared through the following steps: (1) Dissolve stearic acid in 20 parts by weight of anhydrous ethanol, then add nano zinc oxide, and stir at 500 r / min for 20 min at 40℃ to obtain a lipophilic modified metal oxide solution. (2) Styrene, lipophilic modified metal oxide solution and benzoyl peroxide are mixed to obtain an oil phase polymer monomer solution; (3) Sodium dodecylbenzenesulfonate was dissolved in deionized water, and then an oil-phase polymer monomer solution was dropped at a rate of 0.1 g / s. After the drop was completed, magnesium chloride solution was added and stirred at a speed of 500 r / min to obtain an oil-in-water suspension. (4) Under stirring conditions of 500 r / min, the oil-in-water suspension was subjected to polymerization reaction at 80℃ for 3 h. The precipitate was screened out and washed with deionized water to obtain the final product.

[0035] Example 3 A thermo-pressure responsive sealing hollow capsule comprises the following raw materials in parts by weight: 20 parts styrene, 60 parts methyl methacrylate, 5 parts benzoyl peroxide, 10 parts sodium dodecylbenzenesulfonate, 10 parts nano-iron oxide with a particle size of 80 nm, 2 parts stearic acid, 2 parts magnesium chloride solution with a mass concentration of 20%, and 100 parts deionized water.

[0036] The thermo-barotropic sealing hollow capsule in this embodiment is prepared through the following steps: (1) Dissolve stearic acid in 20 parts by weight of anhydrous ethanol, then add nano-iron oxide, and stir at 500 r / min for 20 min at 40℃ to obtain a lipophilic modified metal oxide solution. (2) Styrene, methyl methacrylate, lipophilic modified metal oxide solution and benzoyl peroxide are mixed to obtain an oil phase polymer monomer solution; (3) Sodium dodecylbenzenesulfonate was dissolved in deionized water, and then an oil-phase polymer monomer solution was dropped at a rate of 0.1 g / s. After the drop was completed, magnesium chloride solution was added and stirred at a speed of 500 r / min to obtain an oil-in-water suspension. (4) Under stirring conditions of 500 r / min, the oil-in-water suspension was subjected to polymerization reaction at 80℃ for 3 h. The precipitate was screened out and washed with deionized water to obtain the final product.

[0037] Example 4 A thermo-pressure responsive sealing hollow capsule comprises the following raw materials in parts by weight: 70 parts divinylbenzene, 5 parts potassium persulfate, 5 parts sodium dodecyl sulfate, 8 parts nano-calcium oxide with a particle size of 80 nm, 1 part stearic acid, 1 part sodium chloride solution with a mass concentration of 15%, and 90 parts deionized water.

[0038] The thermo-barotropic sealing hollow capsule in this embodiment is prepared through the following steps: (1) Dissolve stearic acid in 20 parts by weight of anhydrous ethanol, then add nano calcium oxide, and stir at 700 r / min for 15 min at 60℃ to obtain a lipophilic modified metal oxide solution. (2) Mix divinylbenzene, lipophilic modified metal oxide solution and potassium persulfate to obtain an oil phase polymer monomer solution; (3) Dissolve sodium dodecyl sulfate in deionized water, and then drop an oil-phase polymer monomer solution at a rate of 0.05 g / s. After the drop is completed, add sodium chloride solution and stir at a speed of 700 r / min to obtain an oil-in-water suspension. (4) Under stirring conditions of 700 r / min, the oil-in-water suspension was subjected to polymerization reaction at 60°C for 3.5 h. The precipitate was screened out and washed with deionized water to obtain the final product.

[0039] Example 5 A thermo-pressure responsive sealing hollow capsule comprises the following raw materials in parts by weight: 90 parts methyl methacrylate, 15 parts benzoyl peroxide, 15 parts polyvinyl alcohol, 12 parts nano zinc oxide with a particle size of 80 nm, 3 parts oleic acid, 3 parts copper chloride solution with a mass concentration of 25%, and 110 parts deionized water.

[0040] The thermo-barotropic sealing hollow capsule in this embodiment is prepared through the following steps: (1) Dissolve oleic acid in 20 parts by weight of anhydrous ethanol, then add nano zinc oxide, and stir at 900 r / min for 15 min at 90℃ to obtain a lipophilic modified metal oxide solution. (2) Methyl methacrylate, lipophilic modified metal oxide solution and benzoyl peroxide are mixed to obtain an oil phase polymer monomer solution; (3) Dissolve polyvinyl alcohol in deionized water, and then drop an oil-phase polymer monomer solution at a rate of 0.2 g / s. After the drop is completed, add copper chloride solution and stir at a speed of 900 r / min to obtain an oil-in-water suspension. (4) Under stirring conditions of 900 r / min, the oil-in-water suspension was subjected to polymerization reaction at 90℃ for 2.5 h. The precipitate was screened out and washed with deionized water to obtain the final product.

[0041] Comparative Example 1 A thermo-pressure responsive sealing hollow capsule comprises the following raw materials in parts by weight: 80 parts styrene, 10 parts benzoyl peroxide, 10 parts sodium dodecylbenzenesulfonate, 2 parts magnesium chloride solution with a mass concentration of 20%, and 100 parts deionized water.

[0042] The thermo-barotropic sealing hollow capsule in this comparative example was prepared through the following steps: (1) Styrene and benzoyl peroxide were mixed to obtain an oil-phase polymer monomer solution; (2) Sodium dodecylbenzenesulfonate was dissolved in deionized water, and then an oil-phase polymer monomer solution was dropped at a rate of 0.1 g / s. After the drop was completed, magnesium chloride solution was added and stirred at a speed of 500 r / min to obtain an oil-in-water suspension. (3) Under stirring conditions of 500 r / min, the oil-in-water suspension was subjected to polymerization reaction at 80℃ for 3 h. The precipitate was screened out and washed with deionized water to obtain the final product.

[0043] Experimental Example 1. Appearance Analysis The appearance of the thermo-baric responsive plugging hollow capsules prepared in Example 1 and Comparative Example 1 was observed, and the results are as follows: Figure 1 As shown.

[0044] from Figure 1 As can be seen from the above, the temperature-pressure responsive sealing hollow capsule prepared in Example 1 of the present invention is a heavy black hollow sphere, and its black spherical structure can be clearly observed after drying; the temperature-pressure responsive sealing hollow capsule prepared in Comparative Example 1 is a light white hollow sphere.

[0045] 2. Thermal stability analysis The thermo-baric responsive sealing hollow capsule prepared in Example 1 was tested using a comprehensive thermal analyzer, and the results are as follows: Figure 2 As shown.

[0046] from Figure 2As can be seen from the data, the thermo-baric responsive sealing hollow capsule prepared in Example 1 exhibits significant mass loss between 351°C and 460°C, indicating that the cross-linked polystyrene skeleton has undergone thermal decomposition. A step appears in the TG curve at 118°C, which is a typical characteristic of the glass transition temperature (Tg) of this type of polymer. The glass transition temperature determines the ability of the thermo-baric responsive sealing hollow capsule to deform in the crack. Therefore, the thermo-baric responsive sealing hollow capsule of the present invention can operate at high temperatures, with an operating range of 118~351°C.

[0047] 3. Blocking performance analysis In a laboratory simulation of microfracture sealing in a downhole tubing string, a syringe-type simulation device and an electronic universal testing instrument were used to test the sealing strength of the thermo-pressure responsive sealing hollow capsules prepared in Example 1 and Comparative Example 1 for cylindrical pores with diameters of 0.5 mm and 1 mm, respectively, at room temperature. The test temperature was 150°C, heated by a heating jacket. A hydraulic press drove the push rod downwards at a rate of 10 mm / min, pushing the thermo-pressure responsive sealing hollow capsules to seal the bottom pores of 0.5 mm and 1 mm. Under increasing pressure, the pressure eventually exceeded the ultimate pressure limit, and the area at the point where the push rod connected to the liquid surface was approximately 0.785 cm². 2 The result is as follows Figure 3 As shown.

[0048] from Figure 3 As can be seen from the above, the temperature and pressure responsive plugging hollow capsule of the present invention can effectively plug micro-cracks in the downhole tubing. Under high temperature and high pressure, the plugging hollow capsule can form a rubber nail, thereby sealing the leakage point.

[0049] Furthermore, the sealing strength was calculated using the pressure-displacement curve obtained by an electronic universal testing instrument, and the results are as follows: Figures 4-5 As shown.

[0050] from Figures 4-5 As can be seen, the temperature-pressure responsive sealing hollow capsule prepared in Example 1 has a maximum pressure resistance of 26.32 MPa when sealing a small hole with a diameter of 0.5 mm, and a maximum pressure resistance of 13.82 MPa when sealing a large hole with a diameter of 1 mm. The temperature-pressure responsive sealing hollow capsule prepared in Comparative Example 1 has a maximum pressure resistance of 17.48 MPa when sealing a small hole with a diameter of 0.5 mm, and a maximum pressure resistance of 12.36 MPa when sealing a large hole with a diameter of 1 mm. Therefore, it can be seen that the sealing strength of the temperature-pressure responsive sealing hollow capsule prepared in Comparative Example 1 is significantly lower than that of the temperature-pressure responsive sealing hollow capsule in Example 1.

[0051] 4. Evaluation of fluid physicochemical properties Fluid performance analysis was performed on the thermo-baric responsive plugging hollow capsules prepared in Example 1 and Comparative Example 1, including properties such as the density of the plugging unit, fluid density, acid solubility of the plugging unit, and dispersion stability. The plugging agent obtained by sonicating the thermo-baric responsive plugging hollow capsules at room temperature for 30 min was subjected to the following tests.

[0052] Fluid density: The density of the plugging agent fluid was determined using a 50 mL density bottle. The specific steps are as follows: First, weigh the dried density bottle and record its mass. m 1. Fill the density bottle with kerosene and record the mass. m 2. Next, pour out the kerosene and rinse the dried density bottle. Add the sealing agent fluid into the separatory funnel, align the lower end of the funnel with the dried density bottle, and open the funnel valve to allow the sealing agent fluid to fall freely into the density bottle. During this process, ensure that the density bottle is not shaken. After the density bottle is full of sealing agent, weigh the total weight and record it as follows: m 3.

[0053] The formula for calculating fluid density is: (1) In the formula: ρ b To test the fluid density of the plugging agent, g / cm³ 3 ; m 1 represents the mass of the drying density bottle, in grams; m 2 represents the mass of the density bottle after it is filled with kerosene, in grams; m 3 represents the total mass of the density bottle and the sealing agent, in grams; ρ 0 represents the density of kerosene, in g / cm³. 3 .

[0054] Particle density of the sealing unit: The particle density of the sealing unit is obtained by filling the voids between the sealing agent with kerosene to determine the volume of the sealing unit particles. Then, the apparent density of the sealing agent is calculated by dividing the known mass of the sealing unit particles by the volume. The specific steps are as follows: First, weigh 10 g of thermobaric responsive sealing hollow capsules for later use, and record the mass as... m p Next, weigh the dried density bottle and record its mass. m 4. Next, pour the kerosene into a 50 mL density bottle, ensuring there are no air bubbles in the bottle. Weigh the bottle and record the total mass of the kerosene. m 5. Next, pour out at least half of the kerosene from the density bottle. Then, align the lower end of the separatory funnel with the mouth of the density bottle and add the prepared thermo-barometric responsive sealing hollow capsule. Fill the remaining space in the bottle with kerosene. If air bubbles appear, remove them and fill the bottle with kerosene to the mark. Weigh the total mass. m 6.

[0055] The density of kerosene is calculated as follows: (2) In the formula: m 4 represents the mass of the dry, empty density bottle, in grams; m 5 represents the mass (in grams) of a density bottle containing kerosene at room temperature. V 密度瓶 The volume of the density bottle is in cm³. 3 .

[0056] The formula for calculating the density of the plugging unit particles is: (3) In the formula: ρ p The density of the sealing unit particles, in g / cm³ 3 ; m p The dry weight of the sealing unit particles, in grams; m 6 represents the total mass of the sealing unit particles, kerosene, and density bottle, in grams.

[0057] The fluid density and particle density of the thermo-baric responsive plugging hollow capsules prepared in Example 1 and Comparative Example 1 are shown in Table 1.

[0058] Acid solubility: The solid plugging unit of the plugging agent was dried and weighed, then soaked in 20% hydrochloric acid for 72 h. Finally, the plugging unit was washed with deionized water, dried and weighed. The acid solubility was calculated by dividing the difference between the acid-dissolved plugging unit particles and the initial mass by the initial mass. The test results are shown in Table 1.

[0059] Dispersion stability: The dispersion stability test only tested the stacking performance of the millimeter-scale large plugging unit, because the dispersion performance of the micron-scale polymer monomer plugging unit of the plugging capsule is far superior to that of the millimeter-scale polymer monomer plugging unit. The suspension of the thermo-baric response plugging hollow capsule was dispersed into a turbid liquid by ultrasound and then added to a 50 mL graduated cylinder with a height of 10 cm. The plugging unit at the highest point was allowed to settle completely and the time was recorded. The results are shown in Table 1.

[0060] Table 1. Evaluation of the fluid physicochemical properties of Example 1 and Comparative Example 1

[0061] As shown in Table 1, the fluid densities of the thermo-baric responsive plugging hollow capsules in Comparative Example 1 and Example 1 are 1.06 g / cm³. 3 and 1.13 g / cm 3 The particle density of the plugging unit is 1.12 g / cm³. 3 and 1.21 g / cm 3Therefore, it can be seen that the particle density and fluid density of the plugging unit in Example 1 are both greater than those in Comparative Example 1, which is due to the higher quality of the nano-metal oxide. Furthermore, in Example 1, due to the large amount of high-density nanoparticles such as nano-metal oxide, the density of the thermo-pressure responsive plugging hollow capsule increases, the acid solubility increases, and the settling time increases.

[0062] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the scope of the present invention.

Claims

1. A thermo-pressure responsive sealing hollow capsule, characterized in that, It includes the following raw materials in parts by weight: 70-90 parts polymer monomer, 5-15 parts initiator, 5-15 parts dispersant, 8-12 parts metal oxide, 1-3 parts lipophilic modifier, 1-3 parts stabilizer, and 90-110 parts water; The polymer monomer is at least one of styrene, divinylbenzene, and methyl methacrylate; the initiator is potassium persulfate or benzoyl peroxide; the dispersant is a surfactant; the metal oxide is nano-calcium oxide, nano-iron oxide, or nano-zinc oxide; the lipophilic modifier is stearic acid or oleic acid; and the stabilizer is an inorganic salt solution.

2. The thermo-baric responsive sealing hollow capsule as described in claim 1, characterized in that, The raw materials include the following parts by weight: 80 parts polymer monomer, 10 parts initiator, 10 parts dispersant, 10 parts metal oxide, 2 parts lipophilic modifier, 2 parts stabilizer, and 100 parts water.

3. The thermo-baric responsive sealing hollow capsule as described in claim 1, characterized in that, The surfactant is sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, or polyvinyl alcohol; the inorganic salt solution is sodium chloride solution, magnesium chloride solution, or copper chloride solution.

4. The thermo-baric responsive sealing hollow capsule as described in claim 3, characterized in that, The inorganic salt solution has a mass concentration of 15-25%.

5. The method for preparing the thermo-barotropic sealing hollow capsule according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Dissolve the lipophilic modifier in an organic solvent, then add the metal oxide and stir to obtain a lipophilic modified metal oxide solution; (2) Mix the polymer monomer, the lipophilic modified metal oxide solution and the initiator to obtain an oil phase polymer monomer solution; (3) Dissolve the dispersant in water, then add the oil phase polymer monomer solution dropwise. After the addition is complete, add the stabilizer and stir to obtain an oil-in-water suspension. (4) The water-in-oil suspension is subjected to polymerization reaction and washed to obtain the final product.

6. The method for preparing the thermo-barotropic sealing hollow capsule as described in claim 5, characterized in that, The organic solvent in step (1) is anhydrous ethanol; the stirring temperature is 40~90℃, the stirring speed is 500~900 r / min, and the stirring time is 15~25 min.

7. The method for preparing the thermo-barotropic sealing hollow capsule as described in claim 5, characterized in that, In step (3), the droplet acceleration rate is 0.05~0.2 g / s; the stirring speed is 500~900 r / min.

8. The method for preparing the thermo-baric responsive sealing hollow capsule as described in claim 5, characterized in that, In step (4), the polymerization reaction is carried out under stirring conditions, with a stirring speed of 500~900 r / min, a temperature of 40~90℃, and a time of 2.5~3.5 h.

9. The application of the thermo-pressure responsive sealing hollow capsule according to any one of claims 1 to 4 in the repair of micro-leakage in cracks.

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