A high-molecular salt-resistant viscoelastic particle and a preparation process thereof

Abstract

The application provides a kind of high molecular salt-resistant viscoelastic particles and its preparation process, belong to oilfield chemical technical field, including the following steps: step S1, preparation pre-reaction liquid;Step S2, phosphate buffer solution and polyvinyl alcohol aqueous solution are added to pre-reaction liquid, supplement deionized water, oxygen is removed by nitrogen, and water phase is obtained;Liquid paraffin, cyclohexane and Span-80 are mixed and stirred, and the oil phase is obtained by cooling;The water phase is slowly added to the oil phase, the temperature is controlled by ice bath, and the emulsion is obtained by homogenization treatment;Step S3, the mixed solution of tert-butyl hydroperoxide and ascorbic acid is added to the emulsion, and the emulsion is stirred under nitrogen protection, after the reaction is completed, the emulsion is broken, centrifuged, washed, dried, crushed and sieved, to obtain high molecular salt-resistant viscoelastic particles.The application can realize the purposes of good stability and high plugging efficiency of high molecular salt-resistant viscoelastic particles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil field chemistry, in particular to a high-molecular salt-resistant viscoelastic particle and a preparation process thereof. BACKGROUND

[0002] Traditional oil field plugging agents mainly rely on polyacrylamide (PAM) materials to achieve plugging through ionic groups (such as carboxyl) or rigid crosslinking networks. However, in high-salt reservoirs, ionic polymers are severely contracted and lose elasticity due to charge shielding effect, resulting in plugging failure; while rigid particles covalently crosslinked can withstand pressure for a short period of time, but lack environmental responsiveness and need to be treated with strong acid / oxidizing agent for plugging removal, which can easily damage the reservoir. The plugging agents developed in recent years focus on a single response mechanism (such as pH or temperature response), which still has significant limitations: for example, pH-responsive materials can remove plugging under acidic conditions, but cannot cope with high-salt environments; reduction-responsive materials rely on disulfide bonds, but lack salt-resistant support skeletons.

[0003] The patent application file with publication number CN107474807A discloses a fracture-cave type reservoir flow channel adjusting agent, which comprises a carrying liquid and a plugging particle, wherein the carrying liquid comprises a polymer and water in a ratio of (0-3):(97-100); the plugging particle is a viscoelastic particle mixture comprising a high-molecular polymer, calcium carbonate and bentonite in a ratio of (95-100):(0-5):(0-5); and the ratio of the carrying liquid to the plugging particle is (10-100):(0-90). The fracture-cave type reservoir flow channel adjusting agent of the present application is suitable for the flow channel of a reservoir with high temperature and high salinity, and can achieve step-by-step plugging, but it is difficult to achieve high plugging rate and does not have self-repairing ability, resulting in insufficient stability.

[0004] Therefore, it is necessary to provide a high-molecular salt-resistant viscoelastic particle and a preparation process thereof to solve the problems existing in the prior art. SUMMARY

[0005] Therefore, the present application provides a high-molecular salt-resistant viscoelastic particle and a preparation process thereof, which can achieve the purposes of good stability and high plugging efficiency of the high-molecular salt-resistant viscoelastic particle.

[0006] To achieve the above-mentioned purposes, the present application provides a preparation process of a high-molecular salt-resistant viscoelastic particle, which comprises the following steps:

[0007] Step S1, β-cyclodextrin and N-(adamantane-1-yl)prop-2-enamide are added to deionized water, heated and stirred, and then allowed to stand to obtain an inclusion compound; the inclusion compound is added to deionized water, and then acrylamide and N,N'-methylenebisacrylamide are added in sequence and stirred uniformly to obtain a pre-reaction solution;

[0008] Step S2, adding phosphate buffer and polyvinyl alcohol aqueous solution to the pre-reaction solution, supplementing deionized water, purging nitrogen to remove oxygen, obtaining the aqueous phase; mixing liquid paraffin, cyclohexane and Span-80 and stirring to obtain the oil phase by cooling; slowly adding the aqueous phase into the oil phase, controlling the temperature in ice bath, and homogenizing to obtain the emulsion;

[0009] Step S3, adding the mixed solution of tert-butyl hydroperoxide and ascorbic acid to the emulsion, stirring under nitrogen protection, after the reaction, breaking the emulsion, centrifuging, washing, drying, crushing and sieving to obtain the high-molecular salt-resistant viscoelastic particles.

[0010] The β-cyclodextrin has a hydrophobic cavity, and the adamantane group in N-(adamantane-1-yl)prop-2-enamide can be embedded in the cavity of the β-cyclodextrin by hydrophobic interaction to form an inclusion compound, and the acrylamide group can also participate in the copolymerization reaction to fix the inclusion compound on the backbone of the polymer. In a high-salt environment, the salting-out effect of salt ions can strengthen the hydrophobic interaction, and the hydrophobic interaction increases with the increase of salt concentration, which can promote the improvement of the stability of the inclusion compound. At the same time, this combination can form reversible physical cross-linking in the polymer network, thereby endowing the polymer with good toughness and self-repairing property, and improving the salt resistance and viscoelasticity of the obtained particles.

[0011] Acrylamide, as the main polymerization monomer of the viscoelastic particles, rapidly polymerizes under free radical conditions to form a linear polyacrylamide backbone, providing a basic structure for the cross-linked polymer network, and can absorb water molecules through hydrogen bonding, thereby swelling and filling cracks in a low-salt environment. N,N'-methylene bisacrylamide as a covalent cross-linking agent constructs a cross-linked network to maintain the basic structure of the viscoelastic particles and resist high shear force.

[0012] Span-80 (sorbitan monooleate) as a low HLB value surfactant can form a tight monomolecular film at the oil-water interface to stabilize the W / O emulsion. Liquid paraffin and cyclohexane are not soluble in water and have moderate viscosity, which can adjust the polarity of the oil phase, and together with Span-80, a stable oil-in-water emulsion can be prepared to provide a dispersion template for polymerization, promote the uniformity of the particle size of the viscoelastic particles, and balance the permeability and plugging efficiency.

[0013] Tert-butyl hydroperoxide generates free radicals under the reduction of ascorbic acid, which is suitable for low-temperature slow polymerization, avoiding the chain heterogeneity and uneven cross-linking caused by high-temperature polymerization, and is helpful to obtain viscoelastic particles with uniform structure and narrow particle size distribution range.

[0014] Preferably, in step S1, the speed of heating and stirring is 150-250 rpm, the temperature is 45-55℃, and the time is 2-3h; the standing time is 12-14h.

[0015] The β-cyclodextrin and N-(adamantane-1-yl)prop-2-enamide form inclusion compounds by hydrophobic interaction.

[0016] Preferably, in the step S1, N,N'-bis(acryloyl)cystamine is added when acrylamide and N,N'-methylenebisacrylamide are added.

[0017] As a crosslinking agent, N,N'-bis(acryloyl)cystamine can participate in free radical copolymerization to form a covalent crosslinking network, and the double sulfur bond contained therein can be partially broken and recombined in a reducing environment (such as an oil reservoir containing sulfide), realizing controllable degradation of the viscoelastic particles, avoiding permanent plugging, and enhancing the crosslinking density of the initial crosslinking network.

[0018] Preferably, in the step S2, 3-(acrylamidophenyl)boronic acid is dissolved in the phosphate buffer.

[0019] By using 3-(acrylamidophenyl)boronic acid, boronic acid groups are introduced into the viscoelastic particles, and the boronic acid can form a reversible boronic ester bond with polyvinyl alcohol, dynamically adjusting the crosslinking state, improving the self-adaptive and self-healing performance of the crosslinking network, and enhancing the stability of the viscoelastic particles. In an acidic oil reservoir, the dynamic boronic ester bond breaks, and the viscoelastic particles shrink to reduce the plugging strength, while in an alkaline condition, the viscoelastic particles restore viscoelasticity, realizing degradable and repairable viscoelastic particles, avoiding permanent plugging, and improving the flexibility of oil reservoir exploitation.

[0020] Preferably, in the step S2, the speed of mixing and stirring is 200-300 rpm, and the time is 10-20 min.

[0021] Preferably, in the step S2, the speed of dropping is 1-2 mL / min.

[0022] Preferably, in the step S3, the speed of stirring reaction is 150-250 rpm, the time is 22-26 h, and the temperature is 4℃.

[0023] Preferably, in the step S3, the speed of centrifugation is 4000-5000 rpm, and the time is 5-15 min.

[0024] Preferably, in the step S3, the particle size of the high-molecular anti-salt viscoelastic particles is 20-100 μm.

[0025] In order to achieve the above-mentioned purpose, the application further provides a high-molecular anti-salt viscoelastic particle prepared by the preparation process of the high-molecular anti-salt viscoelastic particle, which comprises the following components in parts by weight:

[0026] The emulsion is 290-300 parts, the tert-butyl hydroperoxide solution is 2-3 parts, and the ascorbic acid solution is 2-3 parts.

[0027] The high-molecular salt-resistant viscoelastic particle prepared by the preparation process has good plugging effect.

[0028] Preferably, the emulsion comprises the following raw materials by weight: 100 parts of water phase and 200 parts of oil phase.

[0029] The raw materials of the above components can make the emulsion achieve better effect, and promote the performance of the prepared high-molecular salt-resistant viscoelastic particle to achieve better effect.

[0030] The above technical solutions of the present application at least include the following beneficial effects:

[0031] 1. The inclusion complex is formed by the hydrophobic interaction between the beta-cyclodextrin and the adamantane group in N-(adamantane-1-yl)prop-2-enamide. This combination can form reversible physical cross-linking in the polymer network, thereby endowing the polymer with good toughness and self-repairing property, and improving the salt resistance and viscoelasticity of the obtained particle.

[0032] 2. The cross-linking network is formed by the physical cross-linking brought by the inclusion complex and the dynamic cross-linking in the emulsion, which promotes the viscoelastic particle to maintain stable cross-linking structure in a high-salt ion environment, and significantly improves the viscoelasticity and stability of the viscoelastic particle in a salt solution.

[0033] 3. The free radicals are generated by the reduction of tert-butyl hydroperoxide under ascorbic acid, which is suitable for low-temperature slow polymerization, avoids the chain inhomogeneity and cross-linking inhomogeneity caused by high-temperature polymerization, and helps to obtain viscoelastic particles with uniform structure and narrow particle size distribution range. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. The described embodiments are part of the embodiments of the present application, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present application belong to the scope of protection of the present application.

[0035] Embodiment 1

[0036] 10 g of beta-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide were weighed and added to a beaker containing 250 mL of deionized water, heated to 50℃, stirred at 200 rpm for 2.5 h, cooled to room temperature, and left to stand for 13 h. The inclusion complex was obtained by filtration. 4 g of the inclusion complex was added to 40 mL of deionized water, and ultrasonic treatment was performed at 50℃ for 30 min until complete dissolution. Then, 28 g of acrylamide, 0.06 g of N,N'-methylenebisacrylamide, and 0.5 g of N,N'-bis(acryloyl)cystamine were sequentially added, and stirred uniformly at room temperature to obtain a pre-reaction solution.

[0037] Dissolve 1 g of 3-(acrylamido)benzenboronic acid in 5 mL of phosphate buffer with pH of 7.5; dissolve 3 g of polyvinyl alcohol in 30 mL of deionized water, heat to 90 °C, stir until completely dissolved, cool to obtain a polyvinyl alcohol aqueous solution; add the phosphate buffer and the polyvinyl alcohol aqueous solution into the pre-reaction solution at the same time, maintain the temperature at 4 °C, and introduce nitrogen to remove oxygen to obtain an aqueous phase.

[0038] Under nitrogen protection, dissolve 0.3 mL of tert-butyl hydroperoxide in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; dissolve 0.6 g of ascorbic acid in 3 mL of deionized water to obtain an ascorbic acid solution; then add 2.5 mL of the tert-butyl hydroperoxide solution and 2.5 mL of the ascorbic acid solution into 290 mL of the emulsion, maintain the temperature at 4 °C, and stir at a speed of 350 rpm for 24 h; after the reaction is completed, add ethanol to break the emulsion, and centrifuge at a speed of 4000 rpm for 10 min to obtain microspheres, which are washed, dried, crushed, and sieved to obtain 20-100 μm high-molecular anti-salt viscoelastic particles.

[0039] Example 2

[0040] Weigh 10 g of β-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide, add them into a beaker containing 250 mL of deionized water, heat to 45 °C, stir at a speed of 250 rpm for 2 h, cool to room temperature, stand for 12 h, and filter to obtain an inclusion compound. Add 4.5 g of the inclusion compound into 40 mL of deionized water, ultrasonically treat at 50 °C for 30 min until completely dissolved, and then sequentially add 30 g of acrylamide, 0.05 g of N,N'-methylenebisacrylamide, and 0.6 g of N,N'-bis(acryloyl)cystamine, and stir uniformly at room temperature to obtain a pre-reaction solution.

[0041] Dissolve 1 g of 3-(acrylamido)benzenboronic acid in 5 mL of phosphate buffer with pH of 7.5; dissolve 3 g of polyvinyl alcohol in 30 mL of deionized water, heat to 90 °C, stir until completely dissolved, cool to obtain a polyvinyl alcohol aqueous solution; add the phosphate buffer and the polyvinyl alcohol aqueous solution into the pre-reaction solution at the same time, maintain the temperature at 4 °C, and introduce nitrogen to remove oxygen to obtain an aqueous phase.

[0042] Into a beaker, 150 mL of liquid paraffin and 50 mL of cyclohexane were added, followed by 8 g of Span-80, and stirred at a speed of 250 rpm for 15 min, and cooled to 4 ℃ to obtain an oil phase. 100 mL of the aqueous phase was added dropwise to 200 mL of the oil phase at a speed of 1 mL / min, and homogenized at a speed of 8000 rpm for 5 min under ice bath conditions to obtain an emulsion.

[0043] Under nitrogen protection, 0.3 mL of tert-butyl hydroperoxide was dissolved in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; 0.6 g of ascorbic acid was dissolved in 3 mL of deionized water to obtain an ascorbic acid solution; then 2 mL of the tert-butyl hydroperoxide solution and 2 mL of the ascorbic acid solution were added to 290 mL of the emulsion, and the temperature was maintained at 4 ℃, and stirred at a speed of 300 rpm for 26 h; after the reaction was completed, ethanol was added to break the emulsion, and centrifuged at a speed of 4000 rpm for 10 min to obtain microspheres, which were washed, dried, crushed, and sieved to obtain 20-100 μm high-molecular anti-salt viscoelastic particles.

[0044] Example 3

[0045] 10 g of β-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide were weighed into a beaker containing 250 mL of deionized water, heated to 55 ℃, and stirred at a speed of 200 rpm for 2.5 h, and cooled to room temperature, and stood for 14 h, and filtered to obtain an inclusion compound. 3.5 g of the inclusion compound was added to 40 mL of deionized water, and ultrasonically treated at 50 ℃ for 30 min until completely dissolved, and then 25 g of acrylamide, 0.06 g of N,N'-methylenebisacrylamide, and 0.5 g of N,N'-bis(acryloyl)cystamine were added in sequence, and stirred uniformly at room temperature to obtain a pre-reaction solution.

[0046] 1 g of 3-(acrylamido)phenylboronic acid was dissolved in 5 mL of phosphate buffer with a pH of 7.5; 3 g of polyvinyl alcohol was dissolved in 30 mL of deionized water, heated to 90 ℃, and stirred until completely dissolved, and cooled to obtain a polyvinyl alcohol aqueous solution; the phosphate buffer and the polyvinyl alcohol aqueous solution were simultaneously added to the pre-reaction solution, and the temperature was maintained at 4 ℃, and nitrogen was introduced to remove oxygen to obtain an aqueous phase.

[0047] Into a beaker, 150 mL of liquid paraffin and 50 mL of cyclohexane were added, followed by 6 g of Span-80, and stirred at a speed of 300 rpm for 10 min, and cooled to 4 ℃ to obtain an oil phase. 100 mL of the aqueous phase was added dropwise to 200 mL of the oil phase at a speed of 2 mL / min, and homogenized at a speed of 8000 rpm for 5 min under ice bath conditions to obtain an emulsion.

[0048] Under nitrogen protection, 0.3 mL of tert-butyl hydroperoxide was dissolved in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; 0.6 g of ascorbic acid was dissolved in 3 mL of deionized water to obtain an ascorbic acid solution; then 3 mL of the tert-butyl hydroperoxide solution and 3 mL of the ascorbic acid solution were added to 300 mL of the emulsion, the temperature was maintained at 4°C, and stirring was carried out at a speed of 350 rpm for 26 h; after the reaction was completed, ethanol was added for demulsification, centrifugation was carried out at a speed of 4000 rpm for 10 min, and microspheres were obtained; after washing, drying, and crushing, the high-molecular anti-salt viscoelastic particles with a size of 20-100 μm were obtained by sieving.

[0049] Example 4

[0050] 10 g of β-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide were weighed and added to a beaker containing 250 mL of deionized water, heated to 55°C, stirred at a speed of 150 rpm for 3 h, cooled to room temperature, and left to stand for 13 h; then filtration was carried out to obtain an inclusion compound. 4.5 g of the inclusion compound was added to 40 mL of deionized water, ultrasonic treatment was carried out at 50°C for 30 min until complete dissolution, and then 28 g of acrylamide, 0.06 g of N,N'-methylenebisacrylamide, and 0.6 g of N,N'-bis(acryloyl)cystamine were sequentially added; after uniform stirring at room temperature, a pre-reaction solution was obtained.

[0051] 1 g of 3-(acrylamido)phenylboronic acid was dissolved in 5 mL of phosphate buffer with a pH of 7.5; 3 g of polyvinyl alcohol was dissolved in 30 mL of deionized water, heated to 90°C, and stirred until complete dissolution; after cooling, a polyvinyl alcohol aqueous solution was obtained; the phosphate buffer and the polyvinyl alcohol aqueous solution were simultaneously added to the pre-reaction solution, the temperature was maintained at 4°C, and nitrogen was introduced to remove oxygen to obtain an aqueous phase.

[0052] Into a beaker, 150 mL of liquid paraffin and 50 mL of cyclohexane were added, and then 6 g of Span-80 was added; stirring was carried out at a speed of 250 rpm for 20 min, and the temperature was cooled to 4°C to obtain an oil phase. 100 mL of the aqueous phase was added dropwise to 200 mL of the oil phase at a speed of 1 mL / min, and homogenization treatment was carried out at a speed of 8000 rpm for 5 min under ice bath conditions to obtain an emulsion.

[0053] Under nitrogen protection, 0.3 mL of tert-butyl hydroperoxide was dissolved in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; 0.6 g of ascorbic acid was dissolved in 3 mL of deionized water to obtain an ascorbic acid solution; then 2.5 mL of the tert-butyl hydroperoxide solution and 2.5 mL of the ascorbic acid solution were added to 295 mL of the emulsion, the temperature was maintained at 4°C, and stirring was carried out at a speed of 400 rpm for 22 h; after the reaction was completed, ethanol was added for demulsification, and centrifugation was carried out at a speed of 4000 rpm for 10 min to obtain microspheres, which were washed, dried, crushed, and sieved to obtain 20-100 μm high-molecular anti-salt viscoelastic particles.

[0054] Example 5

[0055] 10 g of β-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide were weighed into a beaker containing 250 mL of deionized water, heated to 45°C, stirred at a speed of 250 rpm for 2 h, cooled to room temperature, and left to stand for 14 h; then filtration was carried out to obtain an inclusion compound. 4 g of the inclusion compound was added to 40 mL of deionized water, and ultrasonic treatment was carried out at 50°C for 30 min until complete dissolution; then 30 g of acrylamide, 0.06 g of N,N'-methylenebisacrylamide, and 0.6 g of N,N'-bis(acryloyl)cystamine were sequentially added, and uniform stirring was carried out at room temperature to obtain a pre-reaction solution.

[0056] 1 g of 3-(acrylamido)phenylboronic acid was dissolved in 5 mL of a phosphate buffer with a pH of 7.5; 3 g of polyvinyl alcohol was dissolved in 30 mL of deionized water, heated to 90°C, and stirred until complete dissolution; then the polyvinyl alcohol aqueous solution was obtained after cooling; the phosphate buffer and the polyvinyl alcohol aqueous solution were simultaneously added to the pre-reaction solution, the temperature was maintained at 4°C, and nitrogen was introduced to remove oxygen to obtain an aqueous phase.

[0057] A beaker was charged with 150 mL of liquid paraffin and 50 mL of cyclohexane, and then 7 g of Span-80 was added; stirring was carried out at a speed of 300 rpm for 10 min, and the temperature was cooled to 4°C to obtain an oil phase. 100 mL of the aqueous phase was added dropwise to 200 mL of the oil phase at a speed of 1 mL / min, and homogenization treatment was carried out at a speed of 8000 rpm for 5 min under ice bath conditions to obtain an emulsion.

[0058] Under nitrogen protection, 0.3 mL of tert-butyl hydroperoxide was dissolved in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; 0.6 g of ascorbic acid was dissolved in 3 mL of deionized water to obtain an ascorbic acid solution; then 2 mL of the tert-butyl hydroperoxide solution and 2 mL of the ascorbic acid solution were added to 295 mL of the emulsion, the temperature was maintained at 4°C, and stirring was carried out at a speed of 400 rpm for 24 h; after the reaction was completed, ethanol was added for demulsification, and centrifugation was carried out at a speed of 4000 rpm for 10 min to obtain microspheres, which were washed, dried, crushed, and sieved to obtain 20-100 μm high-molecular anti-salt viscoelastic particles.

[0059] Example 6

[0060] 10 g of β-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide were weighed into a beaker containing 250 mL of deionized water, heated to 50°C, stirred at a speed of 150 rpm for 3 h, cooled to room temperature, and left to stand for 14 h, and then filtered to obtain an inclusion compound. 3.5 g of the inclusion compound was added to 40 mL of deionized water, and ultrasonic treatment was carried out at 50°C for 30 min until complete dissolution. Then, 25 g of acrylamide, 0.05 g of N,N'-methylenebisacrylamide, and 0.5 g of N,N'-bis(acryloyl)cystamine were sequentially added, and stirring was carried out at room temperature until uniformity to obtain a pre-reaction solution.

[0061] 1 g of 3-(acrylamido)phenylboronic acid was dissolved in 5 mL of phosphate buffer with a pH of 7.5; 3 g of polyvinyl alcohol was dissolved in 30 mL of deionized water, heated to 90°C, and stirred until complete dissolution, and then cooled to obtain a polyvinyl alcohol aqueous solution; the phosphate buffer and the polyvinyl alcohol aqueous solution were simultaneously added to the pre-reaction solution, the temperature was maintained at 4°C, and nitrogen was introduced to remove oxygen to obtain an aqueous phase.

[0062] Into a beaker, 150 mL of liquid paraffin and 50 mL of cyclohexane were added, and then 8 g of Span-80 was added, and stirring was carried out at a speed of 200 rpm for 20 min, and then the temperature was cooled to 4°C to obtain an oil phase. 100 mL of the aqueous phase was added dropwise to 200 mL of the oil phase at a speed of 1 mL / min, and homogenization treatment was carried out at a speed of 8000 rpm for 5 min under ice bath conditions to obtain an emulsion.

[0063] Under nitrogen protection, 0.3 mL of tert-butyl hydroperoxide was dissolved in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; 0.6 g of ascorbic acid was dissolved in 3 mL of deionized water to obtain an ascorbic acid solution; then 3 mL of the tert-butyl hydroperoxide solution and 3 mL of the ascorbic acid solution were added to 295 mL of the emulsion, the temperature was maintained at 4°C, and stirring was carried out at a speed of 350 rpm for 25 h; after the reaction was completed, ethanol was added for demulsification, centrifugation was carried out at a speed of 4000 rpm for 10 min, and microspheres were obtained; after washing, drying, crushing, and sieving, 20-100 μm of the high-molecular anti-salt type viscoelastic particles were obtained.

[0064] Example 7

[0065] 10 g of β-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide were weighed and added to a beaker containing 250 mL of deionized water, heated to 55°C, and stirred at a speed of 200 rpm for 2.5 h; after cooling to room temperature, standing for 13 h, and filtering, an inclusion compound was obtained. 4.5 g of the inclusion compound was added to 40 mL of deionized water, and ultrasonic treatment was carried out at 50°C for 30 min until complete dissolution; then 30 g of acrylamide, 0.06 g of N,N'-methylenebisacrylamide, and 0.6 g of N,N'-bis(acryloyl)cystamine were sequentially added, and stirring was carried out at room temperature until uniformity, to obtain a pre-reaction solution.

[0066] 1 g of 3-(acrylamido)phenylboronic acid was dissolved in 5 mL of a phosphate buffer with a pH of 7.5; 3 g of polyvinyl alcohol was dissolved in 30 mL of deionized water, heated to 90°C, and stirred until complete dissolution; after cooling, a polyvinyl alcohol aqueous solution was obtained; the phosphate buffer and the polyvinyl alcohol aqueous solution were simultaneously added to the pre-reaction solution, the temperature was maintained at 4°C, and nitrogen was introduced to remove oxygen, to obtain an aqueous phase.

[0067] Into a beaker, 150 mL of liquid paraffin and 50 mL of cyclohexane were added, and then 7 g of Span-80 was added; stirring was carried out at a speed of 300 rpm for 10 min, and the temperature was lowered to 4°C, to obtain an oil phase. 100 mL of the aqueous phase was added dropwise to 200 mL of the oil phase at a speed of 2 mL / min, and homogenization treatment was carried out at a speed of 8000 rpm for 5 min under ice bath conditions, to obtain an emulsion.

[0068] Under nitrogen protection, 0.3 mL of tert-butyl hydroperoxide was dissolved in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; 0.6 g of ascorbic acid was dissolved in 3 mL of deionized water to obtain an ascorbic acid solution; then 2.5 mL of the tert-butyl hydroperoxide solution and 2.5 mL of the ascorbic acid solution were added to 295 mL of the emulsion, the temperature was maintained at 4°C, and stirring was carried out at a speed of 350 rpm for 24 h; after the reaction was completed, ethanol was added for demulsification, centrifugation was carried out at a speed of 4000 rpm for 10 min, and microspheres were obtained; after washing, drying, crushing, and sieving, 20-100 μm of the high-molecular anti-salt viscoelastic particles were obtained.

[0069] Example 8

[0070] 10 g of β-cyclodextrin and 1.8 g of N-(adamantane-1-yl)prop-2-enamide were weighed and added to a beaker containing 250 mL of deionized water, heated to 55°C, and stirred at a speed of 200 rpm for 2.5 h; after cooling to room temperature, standing for 13 h, and filtration, an inclusion compound was obtained. 4.5 g of the inclusion compound was added to 40 mL of deionized water, and ultrasonic treatment was carried out at 50°C for 30 min until complete dissolution; then 30 g of acrylamide and 0.06 g of N,N'-methylenebisacrylamide were sequentially added, and uniform stirring was carried out at room temperature to obtain a pre-reaction solution.

[0071] 1 g of 3-(acrylamido)phenylboronic acid was dissolved in 5 mL of a phosphate buffer with a pH of 7.5; 3 g of polyvinyl alcohol was dissolved in 30 mL of deionized water, heated to 90°C, and stirred until complete dissolution; after cooling, a polyvinyl alcohol aqueous solution was obtained; the phosphate buffer and the polyvinyl alcohol aqueous solution were simultaneously added to the pre-reaction solution, the temperature was maintained at 4°C, and nitrogen was introduced to remove oxygen to obtain an aqueous phase.

[0072] A beaker was added with 150 mL of liquid paraffin and 50 mL of cyclohexane, and then 7 g of Span-80 was added; stirring was carried out at a speed of 300 rpm for 10 min, and the temperature was lowered to 4°C to obtain an oil phase. 100 mL of the aqueous phase was added dropwise to 200 mL of the oil phase at a speed of 2 mL / min, and homogenization treatment was carried out at a speed of 8000 rpm for 5 min under ice bath conditions to obtain an emulsion.

[0073] Under nitrogen protection, 0.3 mL of tert-butyl hydroperoxide was dissolved in 3 mL of deionized water to obtain a tert-butyl hydroperoxide solution; 0.6 g of ascorbic acid was dissolved in 3 mL of deionized water to obtain an ascorbic acid solution; 2.5 mL of the tert-butyl hydroperoxide solution and 2.5 mL of the ascorbic acid solution were then added to 295 mL of the emulsion, the temperature was maintained at 4°C, and the mixture was stirred at 350 rpm for 24 hours. After the reaction was completed, ethanol was added to break the emulsion, and the mixture was centrifuged at 4000 rpm for 10 minutes to obtain microspheres, which were then washed, dried, crushed, and sieved to obtain 20-100 μm polymer salt-resistant viscoelastic particles.

[0074] The present invention also carried out comparative examples and related tests.

[0075] Comparative Example 1

[0076] The only difference between Comparative Example 1 and Example 1 is that no inclusion compound was prepared, and only acrylamide and N,N'-methylenebisacrylamide were used to prepare the pre-reaction liquid. Other compositions and preparation processes were the same as those in Example 1, and polymer salt-resistant viscoelastic particles were prepared.

[0077] Comparative Example 2

[0078] The difference between Comparative Example 2 and Example 1 is that tert-butyl hydroperoxide and ascorbic acid are not used for low-temperature initiation, but ammonium persulfate is used as an initiator for thermal initiation. The other compositions and preparation process are the same as those of Example 1, and polymer salt-resistant viscoelastic particles are prepared.

[0079] Performance testing

[0080] The solid content of the polymer salt-resistant viscoelastic particles prepared in Examples 1-8 and Comparative Examples 1-2 was tested. 2.0 g of the sample was placed in a weighing bottle and weighed, which was recorded as W1. The weighing bottle was placed in a constant temperature drying oven at 120° C. for 2 h, and then weighed again, which was recorded as W2.

[0081] Solid content = ×100%;

[0082] The apparent viscosity of the salt-resistant polymer viscoelastic particles prepared in Examples 1-8 and Comparative Examples 1-2 was tested. 15 g of a 5000 mg / L mother liquor was prepared and transferred to 35 g of standard saline to obtain a 1500 mg / L test solution. The water bath temperature was set to 70 ± 0.1°C and maintained at this temperature for 0.5 h. The rotor was connected to a Brookfield viscometer, and approximately 16 mL of the 1500 mg / L test solution was transferred into the measuring cylinder. The temperature was maintained for 10 min, and then the speed was set to 6 rpm. The viscosity was measured using the Brookfield viscometer. Three replicate samples were measured, and the arithmetic mean was taken as the measurement result.

[0083] Dissolution time test was carried out on the polymer salt-resistant viscoelastic particles prepared in Examples 1-8 and Comparative Examples 1-2. The sample was dissolved in brine, and a constant speed stirrer was started at 25℃ in a water bath. The stirring rate was 500±20 rpm. At 20 min, 30 min, 40 min, 50 min and 60 min, the viscosity of the solution was measured by a Brookfield viscometer. When the viscosity values at two time points met the formula |η n -η n-1 |η n < 3% (n≥2), it was considered that the sample was completely dissolved within time Tn.

[0084] Plugging rate test was carried out on the polymer salt-resistant viscoelastic particles prepared in Examples 1-8 and Comparative Examples 1-2. 10 g of ceramic was added to an acid burette, and the ceramic was tightly laid on the bottom of the burette by gently shaking the burette. The bottom valve of the burette was closed. 25 mL of deionized water was added to the burette, and the bottom valve was fully opened. At the same time, a stopwatch was started. The amount of filtration loss was recorded at 7.5 min, which was recorded as F1. 0.5 g of the sample was added to a 250 mL beaker, followed by 99.5 g of deionized water. After stirring for 5 min by a magnetic stirrer, the sample was swelled at room temperature for 2 h. The same test method was used, and the filtration loss was recorded as F2 using the sample solution instead of deionized water.

[0085] Plugging rate = (F2-F1) / F1 × 100%;

[0086] The test results are shown in Table 1.

[0087] Table 1

[0088]

[0089] As shown in Table 1, the apparent viscosity and plugging rate of the polymer salt-resistant viscoelastic particles prepared in Comparative Example 1 decreased significantly, indicating that the preparation of the inclusion compound can improve the plugging efficiency of the polymer salt-resistant viscoelastic particles and form a dynamic cross-linked three-dimensional network with dynamic borate ester and disulfide bond to improve the viscosity. Compared with Example 7, the dissolution time of Comparative Example 2 decreased significantly, indicating that low-temperature initiation by tert-butyl hydroperoxide and ascorbic acid can avoid the chain heterogeneity and cross-linking heterogeneity caused by high-temperature polymerization, which is helpful to obtain viscoelastic particles with uniform structure.

[0090] Compared with Example 7, no N,N'-bis(acryloyl)cystamine is added as a crosslinking agent in Example 8, so that the plugging efficiency of the prepared high molecular salt-resistant viscoelastic particles is reduced, which indicates that N,N'-bis(acryloyl)cystamine can participate in the formation of a covalent crosslinking network through free radical copolymerization, promote the enhancement of the crosslinking network density, and improve the plugging efficiency. It can be seen from the performance test results of the high molecular salt-resistant viscoelastic particles prepared in Examples 1-7 that the performances of the high molecular salt-resistant viscoelastic particles are good, which indicates that the prepared high molecular salt-resistant viscoelastic particles can achieve the purposes of good stability and high plugging efficiency.

[0091] The above is the preferred embodiment of the present application, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A process for preparing a high molecular salt-resistant viscoelastic particle, characterized by, The preparation method comprises the following steps: Step S1, β-cyclodextrin and N-(adamantane-1-yl)prop-2-enamide are added into deionized water, heated and stirred, and then left to stand to obtain an inclusion compound; the inclusion compound is added into deionized water, acrylamide and N,N'-methylenebisacrylamide are sequentially added, and then stirred uniformly to obtain a pre-reaction solution; Step S2, phosphate buffer and polyvinyl alcohol aqueous solution are added into the pre-reaction solution, deionized water is supplemented, nitrogen is introduced to remove oxygen, and then a water phase is obtained; liquid paraffin, cyclohexane and Span-80 are mixed and stirred, and then cooled to obtain an oil phase; the water phase is slowly added into the oil phase, temperature is controlled in an ice bath, and then homogenization treatment is performed to obtain an emulsion; Step S3, under the protection of nitrogen, t-butyl hydroperoxide solution and ascorbic acid solution are added into the emulsion, and then stirred and reacted; after the reaction is completed, demulsification is performed, centrifugation, washing, drying, crushing and sieving are performed to obtain high-molecular anti-salt viscoelastic particles; In the step S2, 3-(acrylamido)phenylboronic acid is dissolved in the phosphate buffer.

2. The preparation process of the polymer salt-resistant viscoelastic particle according to claim 1, characterized in that, In the step S1, the speed of heating and stirring is 150-250 rpm, the temperature is 45-55 °C, and the time is 2-3 h; the standing time is 12-14 h.

3. The preparation process of the polymer salt-resistant viscoelastic particle according to claim 1, characterized in that, In the step S1, N,N'-bis(acryloyl)cystamine is further added when the acrylamide and N,N'-methylenebisacrylamide are added.

4. The preparation process of the polymer salt-resistant viscoelastic particle according to claim 1, characterized in that, In the step S2, the speed of mixing and stirring is 200-300 rpm, and the time is 10-20 min.

5. The preparation process of the polymer salt-resistant viscoelastic particle according to claim 1, characterized in that, In the step S2, the speed of dropping is 1-2 mL / min.

6. The preparation process of the polymer salt-resistant viscoelastic particle according to claim 1, characterized in that, In the step S3, the speed of stirring and reaction is 300-400 rpm, and the time is 22-26 h.

7. The process according to claim 1, wherein the process is characterized by, In the step S3, the speed of centrifugation is 4000-5000 rpm, and the time is 5-15 min.

8. The preparation process of the polymer salt-resistant viscoelastic particle according to claim 1, characterized in that, In the step S3, the particle size of the high-molecular anti-salt viscoelastic particles is 20-100 μm.

9. A high molecular salt resistant viscoelastic particle, characterized by, The high-molecular anti-salt viscoelastic particles are prepared by the preparation process of any one of claims 1-8, and comprise the following components in parts by weight: emulsion 290-300 parts, t-butyl hydroperoxide solution 2-3 parts, and ascorbic acid solution 2-3 parts.

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