Self-suspension ultrahigh-intensity pressure activated phase-change sealed capsule for micro-leakage control and preparation method of self-suspension ultrahigh-intensity pressure activated phase-change sealed capsule

Abstract

The invention discloses a self-suspension ultrahigh-intensity pressure activated phase change sealing capsule for micro-leakage control and a preparation method thereof, and belongs to the technical field of leaking stoppage materials. The preparation raw materials comprise the following components in parts by weight: 50-100 parts of latex, 50-150 parts of water, 5-20 parts of an activating agent, 5-20 parts of a crystal phase change nano reinforcing agent, 5-20 parts of a defoaming agent, 1-10 parts of nano metal oxide, 0.5-5 parts of an anti-scorching agent, 0.5-5 parts of an accelerant and 50-150 parts of a terminating agent. The crystal phase change type nano reinforcing agent comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride and a copolymer of the polytetrafluoroethylene and the polyvinylidene fluoride. The obtained phase-change sealing capsule is high in plugging speed, easy and convenient to construct, low in cost and high in plugging strength, can be applied to rapid repair and control of underground tubular column micron-scale to millimeter-scale crack leakage, and solves the problems that the plugging and repairing work flow is complex, the period is long, the cost is high, the risk is large, the one-time plugging success rate is low, and hidden dangers are difficult to eradicate.

Description

Technical Field

[0001] This invention relates to the field of leak sealing materials technology, specifically to a self-suspended ultra-high strength pressure-activated phase change sealing capsule for micro-leak control and its preparation method. Background Technology

[0002] Well leakage is a long-standing industry problem in offshore oil and gas production. Under complex geological and engineering conditions, critical downhole components, such as chemical injection lines, downhole safety valves, casing, tubing, cement sheaths, and wellheads, are prone to failure due to the coupling effects of physical, chemical, and mechanical processes. Such failures can trigger blowouts, leaks, and other major accidents, causing safety risks, environmental damage, and economic losses far exceeding the costs of conventional well workovers.

[0003] Currently, the main methods for repairing annular pressure are traditional mechanical repair and injection repair. However, existing technologies generally suffer from problems such as complex construction processes, long operation cycles, high costs, significant risks, low success rates of first-time plugging, and difficulty in eradicating subsequent hidden dangers, making it difficult to meet the actual needs of rapid and safe treatment of annular pressure in offshore oil and gas wells.

[0004] With the increasing prominence of annular pressure in offshore oil and gas production wells, there is an urgent need to develop differential pressure activated plugging materials suitable for rapid plugging of leaks in downhole tubing, and to construct a rapid seal repair technology system applicable to offshore oil and gas wells, specifically addressing the characteristics of well seal damage. The establishment of this technology system will not only provide crucial technical support for well workover operations, safe production, and wellbore integrity management, but also hold significant strategic importance for overcoming existing technological limitations and ensuring national oil and gas resource security. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control and its preparation method, thereby solving the problems of complex construction processes, long operation cycles, high costs, high risks, low success rates of one-time sealing, and difficulty in eradicating subsequent hidden dangers in existing leak sealing and repair work.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control, the raw materials comprising the following components by weight: 50-100 parts latex, 50-150 parts water, 5-20 parts activator, 5-20 parts crystalline phase change nano-reinforcing agent, 5-20 parts defoamer, 1-10 parts nano-metal oxide, 0.5-5 parts anti-scorching agent, 0.5-5 parts accelerator, and 50-150 parts terminator; Crystalline phase change nano-reinforcing agents include at least one of polytetrafluoroethylene, polyvinylidene fluoride, and their copolymers.

[0007] The beneficial effects of this invention are as follows: This invention uses latex, crystalline phase change nano-reinforcing agents, and nano-metal oxides surrounding an activator to prepare hollow capsules. The resulting phase change sealing capsules have advantages such as fast sealing speed, simple construction, low cost, and high sealing strength. The nano-metal oxides not only act as fillers and reinforcements but also, under the promotion of accelerators such as ethylene thiourea, can induce a dynamic ionic cross-linking network on the surface of the rubber particles, thereby significantly improving the sealing strength and thermal stability of the entire sealing system. Simultaneously, the crystalline phase change nanomaterials ensure that the sealing particles can easily enter the leak point while greatly improving the sealing strength after entering the leak point, providing a more efficient and reliable leak solution for well site construction.

[0008] Furthermore, the raw materials include the following components by weight: 70-90 parts latex, 80-120 parts water, 8-12 parts activator, 8-12 parts crystal phase change nano-reinforcing agent, 8-12 parts defoamer, 4-6 parts nano metal oxide, 1-3 parts anti-scorching agent, 1-3 parts accelerator and 80-120 parts terminator.

[0009] Furthermore, the raw materials include the following components by weight: 80 parts latex, 100 parts water, 10 parts activator, 10 parts crystal phase change nano-reinforcing agent, 10 parts defoamer, 5 parts nano metal oxide, 1 part anti-scorching agent, 1 part accelerator and 100 parts terminator.

[0010] Furthermore, the latex includes at least one of chloroprene latex, silicone rubber latex, EPDM latex, carboxylated nitrile butadiene latex, natural latex, and butyl latex.

[0011] Furthermore, the activator includes at least one of sodium chloride solution, magnesium chloride solution, and copper chloride solution.

[0012] Furthermore, the defoamer is an organosilicone defoamer.

[0013] Furthermore, the nano-metal oxides include at least one of nano-calcium oxide, nano-iron oxide, nano-zinc oxide, nano-magnesium oxide, and nano-lead oxide.

[0014] Furthermore, the particle size of the nano-metal oxide is 50-100 nm.

[0015] The beneficial effects of adopting the above-mentioned further technical solution are as follows: By adding nano-metal oxides, the present invention dissociates some metal ions in water. These metal ions crosslink with functional groups such as carboxyl groups in latex, and further form a dynamic ionic crosslinking agent under the action of the promoter. At the same time, under the synergistic effect of the activator, an ionic crosslinking self-healing network between rigid particles and flexible materials is constructed, which significantly improves the sealing strength of the phase change sealing capsule.

[0016] Furthermore, anti-scorching agents include magnesium oxide or lead oxide.

[0017] Furthermore, the particle size of the anti-scorching agent is 50-100 nm.

[0018] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By adding magnesium oxide and lead oxide, which have relatively slow reaction rates, and combining them with nano-metal oxides, the present invention avoids the failure of synthesis due to rapid polymerization during the synthesis of the sealing agent, thus ensuring the degree of polymerization and strength of the obtained phase change sealing capsule and improving the overall performance.

[0019] Furthermore, the accelerators include ethyl thiourea or tetramethylethylenediamine.

[0020] Furthermore, the terminating agent is at least one of anionic surfactant, cationic surfactant, and nonionic surfactant.

[0021] Furthermore, the raw materials also include special core additives.

[0022] Furthermore, the special core additives include at least one of phase change repair agents, tracers, nanoprobes, density modifiers, and rigid nanobridgers.

[0023] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By adding special core additives, the phase change sealing capsule carries various special core additives, thereby achieving the effects of improving sealing strength, eliminating leakage location, matching injection fluid, and low-cost enhancement.

[0024] A second aspect of the present invention provides a method for preparing the above-mentioned self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control, comprising the following steps: S1. Mix latex and water, and stir evenly to prepare a latex diluent; S2. Add nano-metal oxides, anti-scorching agents, accelerators, crystallization phase change nano-reinforcing agents and defoamers to the latex dilution solution obtained in S1 and stir to obtain a mixed liquid; S3. Add the activator dropwise to the mixed liquid obtained in S2, let it stand, and obtain an emulsion with hollow spheres; S4. Stir and add a terminator to the emulsion with hollow spheres obtained in S3 to prepare a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control.

[0025] The beneficial effects of this invention are: the preparation method of this invention is simple, the conditions are mild, the preparation process is short, the cost is low, and it is suitable for large-scale industrial production.

[0026] Furthermore, in S2, the stirring speed is 200-2000 rpm, the temperature is 40-90 ℃, and the time is 5-30 min.

[0027] Furthermore, the diameter of the inorganic salt droplets is controlled to be 500-1000 μm during the addition of S3; the standing time is 10-30 min.

[0028] Furthermore, in S4, the stirring speed is 200-2000 rpm, the temperature is 40-90 ℃, and the time is 5-30 min.

[0029] A third aspect of the invention provides the application of the above-described self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leak control in oil and gas leak sealing.

[0030] The beneficial effects of this invention are as follows: The phase change sealing capsule provided by this invention exhibits excellent sealing performance in both small-diameter leaks and perforation sealing. Specifically, the sealing strength for a 0.5 mm diameter leak reaches 481 MPa, an improvement of 1541% compared to Comparative Example 1; and the sealing strength for a 1 mm diameter leak reaches 74.3 MPa, an improvement of 327% compared to Comparative Example 1, making it suitable for sealing conditions with higher pressure requirements. Furthermore, the density of the phase change sealing capsule prepared by this invention can be controlled by adjusting the internal substances, enabling it to self-suspend in pure water and disperse stably without the need for thickeners. This phase change sealing capsule can achieve rapid, ultra-high pressure sealing of downhole tubing leaks. Additionally, by adjusting the special additives inside the capsule, further effects can be provided as needed, offering a more efficient and reliable solution for well site operations.

[0031] The present invention has the following beneficial effects: 1. The preparation method of this invention is simple, the conditions are mild, the preparation process is short, the cost is low, and it is suitable for large-scale industrial production.

[0032] 2. The phase change sealing capsule obtained by this invention can only seal at the leakage location where there is a pressure difference in the pipe. Under normal flow and static storage conditions, it can maintain a stable flow state even without the addition of a thickener. After the sealing operation is completed, the excess sealing agent colloid in the system can be returned to the surface, effectively achieving sealing while avoiding blockage or damage to downhole precision components.

[0033] 3. The phase change sealing capsule obtained by this invention has advantages such as fast sealing speed, simple construction, low cost, and high sealing strength. The nano-metal oxide not only acts as a filler and reinforcement but also, under the promotion of accelerators such as ethyl thiourea, can induce a dynamic ionic cross-linking network on the surface of the rubber particles, thereby significantly improving the sealing strength and thermal stability of the entire sealing system. Simultaneously, the crystalline phase change nanomaterials ensure that the sealing particles can easily enter the leak point while greatly enhancing the sealing strength after entering the leak point.

[0034] 4. The phase change sealing capsule prepared by this invention can carry other special additives inside. By carrying phase change plugging agents, tracers, density regulators, rigid bridging agents, etc., it can respectively achieve the functions of improving plugging strength, tracing leakage location, compatibility with injection fluid, and low-cost enhancement. Attached Figure Description

[0035] Figure 1 The following are images of the fluid appearance, sealing effect, diameter test, and shell thickness test of the phase change sealing capsule prepared in Example 1. (a) is a fluid appearance image, (b) is a sealing effect image, (c) is a diameter test image, and (d) is a shell thickness test image. Figure 2 The microscopic morphology of the phase change sealed capsule prepared in Example 1 is shown in (a) as a cross-sectional view with a magnification of 100x and (b) as a surface view with a magnification of 80,000x. Figure 3 The figures are test curves of the sealing strength of the phase change sealing capsules prepared in Example 1 and Comparative Example 1 when sealing a 0.5 mm pore diameter. (a) is Example 1 and (b) is Comparative Example 1. Figure 4 The figures are test curves of the sealing strength of the phase change sealing capsules prepared in Example 1 and Comparative Example 1 when sealing a 1 mm pore diameter. (a) is Example 1 and (b) is Comparative Example 1. Figure 5 The graphs show the start-up pressure test curves of the phase change sealing capsules prepared in Example 1 and Comparative Example 1 when sealing a 0.5 mm orifice. (a) is Comparative Example 1 and (b) is Example 1. Detailed Implementation

[0036] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0037] Example 1: A self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control, comprising the following components by weight: 80 parts carboxylated nitrile latex, 100 parts deionized water, 10 parts magnesium chloride solution with a mass concentration of 20%, 10 parts polytetrafluoroethylene nanoparticles, 10 parts silicone defoamer (purchased from Beijing Boning Biotechnology Co., Ltd.), 5 parts nano calcium oxide (50-100 nm), 1 part magnesium oxide (50-100 nm), 1 part ethylidene thiourea and 100 parts sodium dodecylbenzenesulfonate solution with a mass concentration of 20%.

[0038] The preparation method of the above-mentioned self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control includes the following steps: S1. Mix carboxylated nitrile latex and deionized water, stir well to obtain a latex dilution; S2. Stir the latex dilution obtained in S1 at 85 ℃ (300 rpm) using a stirrer, and add silicone defoamer, nano calcium oxide, magnesium oxide, ethyl thiourea and polytetrafluoroethylene nanoparticles. Continue stirring for 20 min to obtain a mixed liquid. S3. Add magnesium chloride solution dropwise to a flask containing the mixed liquid, controlling the droplet diameter to 0.5 mm during addition. Then stop stirring and let stand for 20 min to obtain an emulsion with micron to millimeter-sized hollow capsules. S4. While stirring (85 ℃, 300 rpm), add sodium dodecylbenzenesulfonate solution and continue stirring for 15 min to obtain a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control.

[0039] The phase change sealed capsule fluid prepared in this embodiment is as follows: Figure 1 Figure (a) shows the effect of sealing a 0.5 mm orifice. Figure 1 As shown in Figure (b), the large unit diameter of the phase change sealed capsule is as follows: Figure 1 As shown in Figure (c), the thickness is 3.42 mm, and the shell thickness is as follows. Figure 1 As shown in Figure (d), the value is 1.04 mm.

[0040] Example 2: A self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control, comprising the following components by weight: 50 parts chloroprene latex, 50 parts deionized water, 8 parts sodium chloride solution with a mass concentration of 20%, 8 parts polyvinylidene fluoride nanoparticles, 8 parts silicone defoamer (purchased from Beijing Boning Biotechnology Co., Ltd.), 3 parts nano iron oxide (50-100 nm), 0.5 parts lead oxide (50-100 nm), 0.5 parts tetramethylethylenediamine, and 50 parts sodium dodecylbenzenesulfonate solution with a mass concentration of 20%.

[0041] The preparation method of the above-mentioned self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control includes the following steps: S1. Mix chloroprene latex and deionized water, stir well to obtain a latex dilution; S2. Stir the latex dilution obtained in S1 at 85 ℃ (300 rpm) using a stirrer, and add organosilicon defoamer, nano-iron oxide, lead oxide, tetramethylethylenediamine and polyvinylidene fluoride nanoparticles. Continue stirring for 20 min to obtain a mixed liquid. S3. Add sodium chloride solution dropwise to a flask containing the mixed liquid, controlling the droplet diameter to 0.75 mm during addition. Then stop stirring and let stand for 20 min to obtain an emulsion with hollow capsules in the micrometer to millimeter range. S4. While stirring (85 ℃, 300 rpm), add sodium dodecylbenzenesulfonate solution and continue stirring for 15 min to obtain a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control.

[0042] Example 3: A self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control, comprising the following components by weight: 100 parts silicone rubber latex, 150 parts deionized water, 20 parts copper chloride solution with a mass concentration of 20%, 15 parts polytetrafluoroethylene nanoparticles, 15 parts silicone defoamer (purchased from Beijing Boning Biotechnology Co., Ltd.), 8 parts nano zinc oxide (50-100 nm), 3 parts magnesium oxide (50-100 nm), 3 parts tetramethylethylenediamine and 150 parts sodium dodecylbenzenesulfonate solution with a mass concentration of 20%.

[0043] The preparation method of the above-mentioned self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control includes the following steps: S1. Mix silicone rubber latex and deionized water, stir well to obtain a latex dilution; S2. Stir the latex dilution obtained in S1 at 85 ℃ (300 rpm) using a stirrer, and add silicone defoamer, nano zinc oxide, magnesium oxide, tetramethylethylenediamine and polytetrafluoroethylene nanoparticles. Continue stirring for 20 min to obtain a mixed liquid. S3. Add copper chloride solution dropwise to a flask containing the mixed liquid, controlling the droplet diameter to 1.0 mm during addition. Then stop stirring and let stand for 20 min to obtain an emulsion with hollow capsules in the micrometer to millimeter range. S4. While stirring (85 ℃, 300 rpm), add sodium dodecylbenzenesulfonate solution and continue stirring for 15 min to obtain a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control.

[0044] Comparative Example 1: A self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control, comprising the following components by weight: 80 parts carboxylated nitrile latex, 100 parts deionized water, 10 parts magnesium chloride solution with a mass concentration of 20%, 1 part polytetrafluoroethylene nanoparticles, 10 parts silicone defoamer (purchased from Beijing Boning Biotechnology Co., Ltd.), 5 parts nano calcium oxide (50-100 nm), 1 part magnesium oxide (50-100 nm), 1 part ethylidene thiourea and 100 parts sodium dodecylbenzenesulfonate solution with a mass concentration of 20%.

[0045] The preparation method of the above-mentioned self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control includes the following steps: S1. Mix carboxylated nitrile latex and deionized water, stir well to obtain a latex dilution; S2. Stir the latex dilution obtained in S1 at 85 ℃ (300 rpm) using a stirrer, and add silicone defoamer, nano calcium oxide, magnesium oxide, ethyl thiourea and polytetrafluoroethylene nanoparticles. Continue stirring for 20 min to obtain a mixed liquid. S3. Add magnesium chloride solution dropwise to a flask containing the mixed liquid, controlling the droplet diameter to 0.5 mm during addition. Then stop stirring and let stand for 20 min to obtain an emulsion with micron to millimeter-sized hollow capsules. S4. While stirring (85 ℃, 300 rpm), add sodium dodecylbenzenesulfonate solution and continue stirring for 15 min to obtain a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control.

[0046] Experimental Example 1: Microscopic Morphology Characterization The phase change sealed capsule prepared in Example 1 was subjected to cross-sectional and surface scanning electron microscopy analysis, and the characterization results are as follows: Figure 2 As shown.

[0047] Figure 2 The cross section in Figure (a) shows that the thickness of the spherical shell is 162-449 μm and has a fibrous surface. The fibrous surface is formed by the cross-linking of metal oxide nanoparticles and latex under the action of an accelerator. The spherical shell is formed by the rapid aggregation and flocculation of droplets on the surface of the latex when a high concentration of ion solution enters the latex, breaking the zeta potential. Figure 2 Figure (b) shows that the surface of the phase change sealed capsule has nanoparticles of neck-relaxing particles and crystalline phase change nano-reinforcing agents, indicating that metal oxides and crystalline phase change nano-reinforcing agents were successfully synthesized onto the surface of the phase change sealed capsule.

[0048] Experimental Example 2: Sealing Performance This experimental example simulates the sealing of microfractures in a downhole tubing string in a laboratory setting. Using a syringe-type simulation device and an electronic universal testing instrument, the sealing strength of the phase change sealing capsules prepared in Example 1 and Comparative Example 1 was tested at room temperature for cylindrical pores with diameters of 0.5 mm and 1 mm. A hydraulic press drove the push rod downwards at a rate of 10 mm / min, pushing the phase change sealing capsule to seal the bottom 0.5 mm or 1 mm pores. Under continuously increasing pressure, the pressure eventually exceeded the ultimate pressure resistance. The area at the point where the push rod connects with the liquid surface is approximately 0.785 cm². 2 .

[0049] The sealing strength was calculated using the pressure-displacement curve obtained from an electronic universal testing instrument. The experimental results are as follows: Figure 3 and Figure 4 As shown in the figure. The horizontal axis represents the stroke of the hydraulic press, and the vertical axis represents the pressure applied to the sealing fluid.

[0050] The results showed that the phase change sealing capsule prepared in Example 1 of the present invention achieved a sealing strength of 481 MPa for a small hole with a diameter of 0.5 mm. Figure 3 Figure (a) shows a sealing strength of 31.2 MPa compared to Comparative Example 1. Figure 3 The phase change sealing capsule prepared in Example 1 showed a strength of 74.3 MPa for sealing large pores with a diameter of 1 mm (Figure b). The strength of the capsule increased by 1541%. Figure 4 Figure (a) shows a comparison with 22.7 MPa in Comparative Example 1. Figure 4 Figure (b) shows an enhancement of 327%. Furthermore, the hydraulic press travels at a rate of 10 mm / min, the water flow is slow, and the pressure difference at the leak point is small, indicating that the phase change sealing capsule prepared in Example 1 can achieve sealing under a small pressure difference.

[0051] Experimental Example 3: Fluid Performance I. Characterization Methods The fluid properties of the phase change sealed capsules prepared in Example 1 and Comparative Example 1 were characterized, including density, fluid density, acid solubility, and dispersion stability. Each sample was tested after sonication at room temperature for 30 min, and the test methods are as follows: (1) Density Density and fluid density of phase change sealed capsules The density of the plugging agent fluid was determined using a 50 mL density bottle. The specific steps for determining the density of the plugging agent fluid using a 50 mL density bottle are as follows: First, weigh the dried density bottle and record the mass as m1. Next, fill the density bottle with kerosene and record the mass as m2. Then, pour out the kerosene and rinse the dried density bottle. Add the plugging agent fluid to a separatory funnel, align the lower end of the funnel with the dried density bottle, and open the funnel to allow the plugging agent fluid to fall freely into the density bottle. During this process, it is essential to ensure that the density bottle is not shaken. After the density bottle is full of plugging agent, weigh the total weight and record it as m3.

[0052] The formula for calculating bulk density is:

[0053] In the formula: ρ b -Test the bulk density of the plugging agent, g / cm³ 3 ; m 1 - Mass of the dry density bottle, g; m 2 - The mass of the density bottle after it is filled with kerosene, in grams; m 3-Total mass of density bottle and sealing agent, g; ρ 0 - Density of kerosene, g / cm³ 3 .

[0054] The density of phase change sealing capsule particles is determined by filling the voids between the sealing agent with kerosene to obtain the volume of the phase change sealing capsule particles. Then, the apparent density of the sealing agent is calculated by dividing the known mass of the phase change sealing capsule particles by the volume. The specific steps are as follows: First, weigh 10 g of phase change sealing capsule particles and record the mass as m. p Next, weigh the dried density bottle and record its mass as m4. Then, pour kerosene into the 50 ml density bottle (ensuring no air bubbles are present), and weigh the total mass of the density bottle and kerosene, recording it as m5. Afterward, 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 phase change sealing capsule granules. Fill the remaining space in the bottle with kerosene; if air bubbles appear, remove them and fill with kerosene to the graduation mark, weighing the total mass as m6.

[0055] Calculate the density of kerosene ρ 0 is:

[0056] In the formula: m 4- The mass of a dry, empty density bottle, in g; m 5. Mass of a density bottle containing kerosene at room temperature, in g; V 密度瓶 - Volume of the density bottle, in cm³ 3 .

[0057] The formula for calculating the density of phase change sealed capsule particles is:

[0058] In the formula: ρ p - Density of phase change sealed capsule particles, g / cm³ 3 ; m p -Dry weight of phase change sealed capsule particles, g; m 6-Total mass of phase change sealed capsule particles, kerosene, and density bottle, g.

[0059] (2) Acid solubility The acid solubility was determined using hydrochloric acid. The solid phase change sealing capsules of the sealing agent were dried and weighed, then immersed in 20% hydrochloric acid for 72 hours. Finally, the phase change sealing capsules were washed with deionized water, dried, and weighed. The acid solubility was calculated by dividing the difference between the acid-dissolved phase change sealing capsule particles and their initial mass by the initial mass.

[0060] (3) Dispersion stability The dispersion stability test only tested the sedimentation performance of millimeter-sized phase change sealed capsules, because the dispersion performance of micron-sized latex phase change sealed capsules far exceeds that of millimeter-sized latex phase change sealed capsules. After ultrasonic dispersion, the capsules were added to a 50 mL graduated cylinder with a height of 10 cm, and the time was recorded after the phase change sealed capsules at the highest point had completely settled.

[0061] II. Characterization Results The characterization results of fluid properties are as follows: Figure 5 As shown in Table 1.

[0062] Table 1. Evaluation of the fluid physicochemical properties of Example 1 and Comparative Example 1

[0063] As shown in the table, the fluid density and particle density of the phase change sealed capsule prepared in Example 1 of this invention are 1.14 g / mL and 1.16 g / cm³, respectively. 3 Both were higher than those of the phase change sealed capsules prepared in Comparative Example 1 (1.10 g / mL and 1.12 g / cm³). 3 Meanwhile, the acid solubility and sedimentation time of the phase change sealed capsule prepared in Example 1 were significantly lower than those in Comparative Example 1. This is mainly because the amount of polytetrafluoroethylene nanoparticles added in Example 1 was higher, resulting in better fluid properties.

[0064] Experiment Example 4: Blocking Simulation Experiment An experimental system was constructed in the laboratory to simulate the sealing of micro-fractures in downhole tubing using a self-suspended ultra-high pressure activated phase change sealing capsule for micro-leakage control. The critical start-up pressure for effective sealing in Comparative Example 1 and Example 1 was compared and tested. The device uses a horizontal flow pump to displace water into the leakage simulation component, and a pressure monitoring component is inserted to monitor the displacement pressure in real time. The leakage component consists of a core holder cavity and an outlet leak. The core holder cavity is filled with a phase change sealing capsule, and an analytical balance is connected to the leak as a flow rate monitoring component. During operation, the phase change sealing capsule is first added to the sealed vessel, the control valve is closed, and the horizontal flow pump is turned on. At this time, the horizontal flow pump displaces water into the core holder cavity, pushing the phase change sealing capsule through the leak. The discharged liquid falls onto the analytical balance, and the pressure curve is recorded in real time. The experimental flow rates, from low to high, are 0.5, 1, 1.5, 2.5, 5, 10, 15, 20, 25, and 30 mL / min. The leak was simulated using a cylinder with a diameter of 0.5 mm and a length of 10 mm. The experimental results are as follows: Figure 5 As shown.

[0065] The results showed that the critical start-up sealing capsule prepared in Comparative Example 1 had a critical start-up sealing flow rate of 1.5 mL / L, while the phase change sealing capsule prepared in Example 1 had a critical start-up sealing flow rate of 2.5 mL / L. The higher critical start-up flow rate means that a higher pump pressure is required in practical applications to achieve a seal. The phase change sealing capsule obtained in Example 1, with its greater use of crystalline phase change nanoparticles such as polytetrafluoroethylene, therefore requires a relatively higher pressure to achieve effective sealing.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control, characterized in that, The raw materials include the following components by weight: 50-100 parts latex, 50-150 parts water, 5-20 parts activator, 5-20 parts crystal phase change nano-reinforcing agent, 5-20 parts defoamer, 1-10 parts nano metal oxide, 0.5-5 parts anti-scorching agent, 0.5-5 parts accelerator and 50-150 parts terminator; The crystalline phase change nano-reinforcing agent includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, and their copolymers.

2. The self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to claim 1, characterized in that, The raw materials include the following components by weight: 70-90 parts latex, 80-120 parts water, 8-12 parts activator, 8-12 parts crystal phase change nano-reinforcing agent, 8-12 parts defoamer, 4-6 parts nano metal oxide, 1-3 parts anti-scorching agent, 1-3 parts accelerator and 80-120 parts terminator.

3. The self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to claim 2, characterized in that, The raw materials include the following components by weight: 80 parts latex, 100 parts water, 10 parts activator, 10 parts crystal phase change nano-reinforcing agent, 10 parts defoamer, 5 parts nano metal oxide, 1 part anti-scorching agent, 1 part accelerator and 100 parts terminator.

4. The self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to any one of claims 1-3, characterized in that, The latex includes at least one of chloroprene latex, silicone rubber latex, EPDM latex, carboxylated nitrile butadiene latex, natural latex, and butyl latex; The activator includes at least one of sodium chloride solution, magnesium chloride solution and copper chloride solution; The defoamer is an organosilicone defoamer; The nano-metal oxides include at least one of nano-calcium oxide, nano-iron oxide, nano-zinc oxide, nano-magnesium oxide, and nano-lead oxide. The anti-scorching agent includes magnesium oxide or lead oxide; The accelerator includes ethyl thiourea or tetramethylethylenediamine; The terminator is at least one of anionic surfactants, cationic surfactants, and nonionic surfactants.

5. The self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to any one of claims 1-3, characterized in that, The raw materials also include special core additives; The special core additives include at least one of phase change repair agents, tracers, nanoprobes, density modifiers, and rigid nanobridgers.

6. The method for preparing the self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Mix latex and water, and stir evenly to prepare a latex diluent; S2. Add nano-metal oxides, anti-scorching agents, accelerators, crystallization phase change nano-reinforcing agents and defoamers to the latex dilution solution obtained in S1 and stir to obtain a mixed liquid; S3. Add the activator dropwise to the mixed liquid obtained in S2, let it stand, and obtain an emulsion with hollow spheres; S4. Stir and add a terminator to the emulsion with hollow spheres obtained in S3 to prepare a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control.

7. The preparation method of the self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to claim 6, characterized in that, In step S2, the stirring speed is 200-2000 rpm, the temperature is 40-90 ℃, and the time is 5-30 min.

8. The method for preparing a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to claim 6, characterized in that, In step S3, the diameter of the inorganic salt droplets is controlled to be 500-1000 μm during addition; the settling time is 10-30 min.

9. The method for preparing a self-suspended ultra-high-strength pressure-activated phase change sealing capsule for micro-leakage control according to claim 6, characterized in that, The stirring speed in S4 is 200-2000 rpm, the temperature is 40-90 ℃, and the time is 5-30 min.

10. The application of the self-suspending ultra-high-strength pressure-activated phase change sealing capsule for micro-leak control as described in any one of claims 1-5 in the sealing of oil and gas leaks.

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