Salt-resistant viscoelastic particle oil displacement agent and preparation process thereof
Through the coordinated design of composite additives and surfactants, particles with high cross-linking density and porous structure are formed, which solves the stability and adaptability problems of viscoelastic particle oil displacement agents in high-salt environments and achieves long-term oil displacement effects in high-salt oil reservoirs.
Patent Information
- Application Number
- CN202510895343.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-30
- Publication Date
- 2025-09-09
AI Technical Summary
Existing viscoelastic particle oil displacement agents are easily hydrolyzed and unstable in high-salinity environments, and their pore structure is poorly compatible with the formation permeability, resulting in the loss of viscoelasticity, which limits their application in high-salinity reservoirs.
The synergistic effect of polyacrylamide crosslinkers and cyclodextrin derivatives in the composite additives is used, combined with acrylamide and sulfonic acid monomer copolymers in a specific molar ratio, to form particles with high crosslinking density and porous structure. Combined with the optimal design of surfactants, the salt resistance and formation permeability of the particles are enhanced.
It can maintain long-term stability and viscoelasticity in high-mineralization formations, avoid particle aggregation or structural collapse, improve oil recovery efficiency, prevent seepage blockage, and is suitable for complex reservoir environments.
Smart Images
Figure CN120607883A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of oilfield chemical flooding, in particular to a salt-resistant viscoelastic particle flooding agent and a preparation process thereof. Background Art
[0002] As conventional oil fields enter the middle and late stages of development, chemical flooding technology has become the core means to improve crude oil recovery. Currently, polymer flooding and surfactant flooding are the two most widely used technologies: polymers expand the swept volume by increasing the viscosity of injected water, while surfactants improve oil washing efficiency by reducing the oil-water interfacial tension; however, traditional polymer flooding agents are prone to molecular chain curling in highly salinized formations due to salt ions compressing the double layer, resulting in a significant decrease in solution viscosity and the loss of their viscosity-increasing effect; surfactants face bottlenecks such as large formation adsorption losses, poor chemical stability and high costs.
[0003] In recent years, viscoelastic particle displacement agents have attracted attention due to their unique "deformation-migration-plugging" dynamic behavior. They penetrate deep into low-permeability areas through the elastic deformation of the particles and rely on viscous resistance to generate microscopic displacement pressure differences. However, existing particle displacement agents still have significant defects in high-salt environments: first, the surface structure of the particles is dense, and salt-resistant additives are difficult to disperse evenly. They are prone to aggregation or structural collapse when encountering high concentrations of salt ions; second, conventional cross-linked networks are easily hydrolyzed and degraded, and their long-term stability is insufficient, resulting in the loss of viscoelasticity of the particles; third, the pore structure does not match the formation permeability, which can easily cause a sharp increase in injection pressure or blockage of the channel. These problems have seriously limited their large-scale application in high-salt oil reservoirs, which account for more than 60% of my country's oil and gas resources. Summary of the Invention
[0004] In response to the shortcomings of the existing technology, the present invention provides a salt-resistant viscoelastic particle oil-displacing agent and a preparation process thereof, which solve the problems of existing particle oil-displacing agents such as easy hydrolysis and instability of the cross-linked network in high-salt environments, poor compatibility between the pore structure and the formation permeability, and loss of viscoelasticity due to particle aggregation or structural collapse.
[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A salt-resistant viscoelastic particle oil-displacing agent comprising the following components by mass percentage: Nonionic surfactant 22%-28%; Anionic surfactant 18%-23%; Composite additives 6%-9%; The balance is deionized water; The composite auxiliary agent comprises the following components and their mass ratios: Cross-linking agent: polyacrylamide compound, accounting for 40%-60% of the total mass of the composite additive, cross-linking degree 0.8%-1.8%, molecular weight 1.5×106 -3×10 6 Da; Stabilizer: Hydroxypropyl methylcellulose, accounting for 20%-30% of the total mass of the composite additives, with a viscosity of 1500-2000 mPa·s; Solubilizer: polyethylene glycol, accounting for 10%-20% of the total mass of the composite additive, with a molecular weight of 3000-5000Da; Cyclodextrin derivatives: hydroxypropyl-β-cyclodextrin or sulfobutyl-β-cyclodextrin with a substitution degree of 0.6-1.2, which accounts for 10%-15% of the total mass of the composite auxiliary agent.
[0006] By adopting the above technical solution: through the synergistic effect of polyacrylamide cross-linking agents and cyclodextrin derivatives in the composite additives, combined with acrylamide and sulfonic acid monomer copolymers in a specific molar ratio, particles with high cross-linking density and porous structure are formed, which significantly improves the salt resistance; the sulfonic acid groups resist the damage of high-salt environments to polymer chains through the charge shielding effect, and the honeycomb cross-linked network enhances the mechanical strength of the particles; combined with the optimal design of surfactants, the solubility of the particles and the permeability of the formation are simultaneously optimized, and the stability and viscoelasticity are maintained for a long time in highly mineralized formations, making it suitable for complex oil reservoir environments.
[0007] Preferably, the nonionic surfactant is a fatty alcohol polyoxyethylene ether having 30-45 oxyethylene groups; The anionic surfactant is sodium dodecylbenzenesulfonate with a sulfonation degree of not less than 85% or a carbon chain length of C 14 -C 18 α-olefin sulfonates.
[0008] Preferably, the particle size of the oil-displacing agent is 100-200 μm; The particle surface has a porous structure with a porosity of 40%-55%, and the interior of the particle is a honeycomb cross-linked network with a cross-linking density of 3-5 mmol / cm 3 .
[0009] Preferably, the average pore size of the porous structure is 0.5-5 μm, and the specific surface area is ≥20 m 2 / g.
[0010] Preferably, the polyacrylamide cross-linking agent is a copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid, and the molar ratio of the two is 15:1-20:1.
[0011] A preferred preparation process of a salt-resistant viscoelastic particle oil-displacing agent is used for the salt-resistant viscoelastic particle oil-displacing agent, comprising the following steps: S1, premixing stage: add nonionic surfactant and anionic surfactant to deionized water at 40-45°C and stir at 300-400 rpm for 25-35 minutes; S2, additive integration stage: Heat to 50-55°C, add polyethylene glycol first, stir for 5 minutes, add hydroxypropyl methylcellulose, and add cyclodextrin derivative after 8 minutes; heat to the target temperature at a gradient of 2°C / min, and then ultrasonicate the mixture; S3, cross-linking reaction stage: add polyacrylamide cross-linking agent, adjust the pH to 7.5-8.5 with a sodium hydroxide solution with a mass concentration of 0.1%-0.3%, and then react in a closed reactor at 45-55°C for 1.5-2.5 hours, and maintain the reaction pressure at 0.2-0.4MPa; S4, aging and granulation stage: the aging material is heated to 70-75°C at a rate of 10-15°C / h under nitrogen protection for 2-2.5 hours, and then spray-dried and granulated; S5, post-processing stage: After spray drying, the granules are dried in a fluidized bed until the moisture content is ≤8%.
[0012] Preferably, the ultrasonic treatment in S2 is carried out in two stages: The first stage was 35 kHz for 8-10 minutes with a power density of 0.5-0.8 W / cm 3 ; The second stage was performed at 40 kHz for 7-9 minutes, with the power density increased to 1.0-1.2 W / cm 3 .
[0013] Preferably, S4 is subjected to freeze crushing pretreatment before spray drying: The matured material was placed in an environment of -25°C to -15°C for quick freezing for 30-40 minutes, and crushed with a blade crusher at a speed of 800-1000 rpm to a particle size of ≤500 μm, with the blade spacing adjusted to 0.1-0.3 mm.
[0014] Preferably, the spray drying granulation in S4 adopts a centrifugal atomizer with an inlet temperature of 165-175°C, an outlet temperature of 85-95°C, an atomizing disk speed of 10000-12000 rpm, and a feed rate of 8-12 mL / min.
[0015] Preferably, in step S3, the crosslinking agent is added in two times: 70%-80% of the total amount is added for the first time, and the remaining amount is added after 20 minutes, and the stirring rate is maintained at 400-500 rpm for at least 10 minutes after each addition.
[0016] The present invention provides a salt-resistant viscoelastic particle oil-displacing agent and its preparation process. It has the following beneficial effects: 1. In the present invention, through the synergistic effect of the polyacrylamide cross-linking agent and cyclodextrin derivative in the composite additive, combined with a copolymer of acrylamide and sulfonic acid monomers in a specific molar ratio, particles with high cross-linking density and porous structure are formed, which significantly improves the salt resistance. The sulfonic acid group resists the damage of the high-salt environment to the polymer chain through the charge shielding effect, and the honeycomb cross-linked network enhances the mechanical strength of the particles. Combined with the optimal design of surfactants, the solubility and formation permeability of the particles are simultaneously optimized, and the stability and viscoelasticity are maintained for a long time in highly salinized formations, making it suitable for complex oil reservoir environments.
[0017] 2. In the present invention, the honeycomb cross-linked network and porous structure inside the oil-displacing agent give it high porosity and specific surface area. Combined with the stepwise addition of the cross-linking agent and the speed-controlled stirring process, a uniform cross-linking reaction is achieved. This structure can effectively adsorb and disperse salt in a salt ion environment, avoiding particle aggregation or structural collapse. At the same time, the high cross-linking density inhibits the hydrolysis and degradation of the polymer main chain, significantly extending the effective period of the oil-displacing agent in the formation, and the solution maintains stable viscoelasticity and dynamic rheological properties for a long time.
[0018] 3. In the present invention, an oil-displacing agent with uniform particle size and controllable pore size is produced through freeze-crushing pretreatment and precise control of spray-drying parameters; the ice crystal stress formed during the freeze-crushing process, combined with the high-speed shearing of the blade, refines the particle size and improves fluidity; the high-speed atomization and gradient temperature control of the spray drying ensure the integrity of the porous structure on the particle surface; this process enables the oil-displacing agent to dissolve rapidly after injection into the formation, and the pore structure promotes the release of active ingredients, while avoiding the problem of penetration blockage caused by uneven particles, thereby improving oil recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 The present invention is a process flow chart for preparing a salt-resistant viscoelastic particle oil-displacing agent. DETAILED DESCRIPTION
[0020] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.
[0021] The embodiment of the present invention provides a salt-resistant viscoelastic particle oil-displacing agent, which comprises the following components by mass percentage: Nonionic surfactant 22%-28%; Anionic surfactant 18%-23%; Composite additives 6%-9%; The balance is deionized water; The composite additives include the following components and their mass proportions: Cross-linking agent: polyacrylamide compound, accounting for 40%-60% of the total mass of the composite additive, cross-linking degree 0.8%-1.8%, molecular weight 1.5×10 6 -3×10 6 Da; Stabilizer: Hydroxypropyl methylcellulose, accounting for 20%-30% of the total mass of the composite auxiliary agent, with a viscosity of 1500-2000 mPa·s; Solubilizer: Polyethylene glycol, accounting for 10%-20% of the total mass of the composite auxiliary agent, with a molecular weight of 3000-5000 Da; Cyclodextrin derivatives: hydroxypropyl-β-cyclodextrin or sulfobutyl-β-cyclodextrin with a substitution degree of 0.6-1.2, which accounts for 10%-15% of the total mass of the composite auxiliary agent.
[0022] Specifically, the non-ionic surfactant plays a role in reducing the oil-water interfacial tension, thereby enhancing the oil-water mixing ability and improving the crude oil recovery rate; the anionic surfactant plays a role in improving the adsorption and wettability of the oil displacement agent in the reservoir rock, thereby enhancing the oil washing efficiency of the reservoir; the cross-linking agent in the composite additive plays a role in constructing a viscoelastic gel network, thereby forming a stable oil displacement front in the reservoir and improving the oil displacement efficiency; the stabilizer in the composite additive plays a role in improving the viscosity stability of the oil displacement agent, thereby maintaining good rheological properties under high-temperature reservoir conditions, and enhancing the sand carrying capacity and salt resistance of the oil displacement agent; the solubilizer in the composite additive plays a role in improving the solubility of the oil displacement agent and reducing its precipitation rate in the reservoir, thereby extending the effective action time of the oil displacement agent in the reservoir; the cyclodextrin derivative in the composite additive plays a role in encapsulating and stabilizing the surfactant molecules, thereby improving the salt resistance and thermal stability of the oil displacement agent and reducing the loss of the surfactant.
[0023] The nonionic surfactant is a fatty alcohol polyoxyethylene ether with 30-45 oxyethylene groups; The anionic surfactant is sodium dodecylbenzenesulfonate with a sulfonation degree of not less than 85% or a carbon chain length of C 14 -C 18 α-olefin sulfonates.
[0024] Specifically, the nonionic surfactant is a fatty alcohol polyoxyethylene ether with 30-45 oxyethylene groups; this specific nonionic surfactant reduces the oil-water interfacial tension, thereby enhancing the oil-water mixing ability and improving the crude oil recovery rate. At the same time, its good wettability helps to improve the wettability of the reservoir rock and further improve the oil displacement efficiency; the anionic surfactant is sodium dodecylbenzene sulfonate with a sulfonation degree of not less than 85% or a carbon chain length of C 14 -C18 α-olefin sulfonate; through this highly sulfonated anionic surfactant, the adsorption capacity of the oil displacement agent in the reservoir rock is improved, thereby enhancing the oil washing efficiency of the reservoir. At the same time, its strong anionic property helps to improve the stability of the oil displacement agent in the high-mineralization reservoir environment, reduce the reaction with calcium and magnesium ions in the formation, and maintain good oil displacement performance.
[0025] The particle size of the oil displacement agent is 100-200 μm; The particle surface has a porous structure with a porosity of 40%-55%, and the interior of the particle is a honeycomb cross-linked network with a cross-linking density of 3-5mmol / cm 3 .
[0026] Specifically, by controlling the particle size within this range, the particles are ensured to flow and penetrate effectively in the pores of the reservoir, thereby improving the uniformity of the oil displacement agent distribution in the reservoir and the oil displacement efficiency. The particle surface has a porous structure with a porosity of 40%-55%, which increases the particle surface area and improves the oil-water exchange efficiency, thereby increasing the particle's ability to capture crude oil and enhancing the oil displacement effect. The interior of the particle is a honeycomb cross-linked network with a cross-linking density of 3-5mmol / cm 3 , which improves the mechanical strength and deformation resistance of the particles, thereby keeping the particles stable under high-pressure conditions in the reservoir, preventing the particles from breaking, and ensuring the long-term effectiveness of the oil displacement agent.
[0027] The average pore size of the porous structure is 0.5-5μm, and the specific surface area is ≥20m 2 / g.
[0028] Specifically, the average pore size of the porous structure is 0.5-5 μm, which plays a role in adjusting the pore structure to optimize the fluid flow characteristics, thereby allowing the liquid in the reservoir to pass through the particles more effectively, while limiting the passage of larger molecular oil droplets, increasing the contact opportunity between oil droplets and water, and improving the oil-water separation efficiency; the specific surface area is ≥20m 2 / g; This high surface area design increases the contact area between the particles and the reservoir fluid, thereby enhancing the particles' adsorption capacity for crude oil and improving the oil capture efficiency of the oil displacement agent. The high surface area also means more active sites available for interaction with oil droplets, leading to more effective stripping and recovery of residual oil from rock pores.
[0029] The polyacrylamide cross-linking agent is a copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid, and the molar ratio of the two is 15:1-20:1.
[0030] Specifically, acrylamide, as the main monomer of the copolymer, provides the polymer backbone and basic mechanical properties. Its amide group can also form complexes with multivalent cations in the oil reservoir, enhancing the salt resistance of the particles. 2-Acrylamido-2-methylpropanesulfonic acid, as a functional monomer, introduces sulfonic acid groups, improving the water solubility and surface activity of the polymer, thereby enhancing the dispersibility and stability of the particles in the oil reservoir. By precisely controlling the molar ratio of the two monomers, the chemical composition and properties of the copolymer are optimized, thereby achieving a high crosslinking density and mechanical strength while maintaining good water solubility. The preparation process of the polyacrylamide cross-linking agent is as follows: 1. Monomer preparation: Acrylamide (AM): Weigh a certain amount of acrylamide monomer and dissolve it in deionized water to prepare a solution with a concentration of 5%-20%.
[0031] 2-Acrylamido-2-methylpropanesulfonic acid (AMPS): also dissolved in deionized water to prepare a solution with a concentration of 1%-5%.
[0032] Mix the monomer solution: Combine AM and AMPS in a molar ratio of 15:1 to 20:1 and stir thoroughly. Ensure the monomers are fully dissolved to avoid clumping.
[0033] 2. Preparation of initiator and chain transfer agent: Initiator: Ammonium persulfate (APS) is usually used as an initiator and is prepared into an aqueous solution with a concentration of 0.1%-0.5%.
[0034] Chain transfer agent: Add an appropriate amount of N,N-dimethylacetamide (DMAC) or other suitable chain transfer agents to adjust the molecular weight and structure of the polymer.
[0035] 3. Polymerization reaction: 3.1. Reaction vessel: The reaction is carried out in a reactor equipped with a stirrer, temperature control and nitrogen protection.
[0036] 3.2 Reaction conditions: Temperature: controlled between 40-60℃, usually 50℃ is selected to obtain good polymerization efficiency.
[0037] pH value: Adjust to neutral or slightly alkaline (pH 7-8) using sodium hydroxide or ammonia water.
[0038] Time: The reaction time is 3-6 hours, and the specific time is adjusted according to the monomer concentration and reaction conditions.
[0039] 3.3、Operation steps: The mixed monomer solution was slowly added into the reactor while nitrogen was introduced to exclude oxygen.
[0040] Start stirring and slowly add the initiator solution.
[0041] The temperature is raised to the set temperature, maintained at a constant temperature, and the polymerization reaction is carried out.
[0042] During the reaction, the viscosity or solid content is tested by sampling to determine whether the reaction has achieved the expected results.
[0043] 4. Post-processing: Termination of the reaction: When the reaction reaches the expected conversion rate, cool to room temperature and add an appropriate amount of sodium bisulfite to terminate the reaction.
[0044] Filtration and concentration: The polymer solution is filtered to remove insoluble matter, and then the solution is converted into a solid powder by vacuum concentration or spray drying.
[0045] Drying and packaging: Dry the solid powder at low temperature to ensure that the moisture content is less than 3%, then package and store.
[0046] Please see the attached Figure 1 A process for preparing a salt-resistant viscoelastic particle oil-displacing agent, which is used for the above-mentioned salt-resistant viscoelastic particle oil-displacing agent, comprises the following steps: S1, premixing stage: add nonionic surfactant and anionic surfactant to deionized water at 40-45°C and stir at 300-400 rpm for 25-35 minutes; S2, additive integration stage: Heat to 50-55°C, add polyethylene glycol first, stir for 5 minutes, add hydroxypropyl methylcellulose, and add cyclodextrin derivative after 8 minutes; heat to the target temperature at a gradient of 2°C / min, and then ultrasonicate the mixture; S3, cross-linking reaction stage: add polyacrylamide cross-linking agent, adjust the pH to 7.5-8.5 with a sodium hydroxide solution with a mass concentration of 0.1%-0.3%, and then react in a closed reactor at 45-55°C for 1.5-2.5 hours, and maintain the reaction pressure at 0.2-0.4MPa; S4, aging and granulation stage: the aging material is heated to 70-75°C at a rate of 10-15°C / h under nitrogen protection for 2-2.5 hours, and then spray-dried and granulated; S5, post-processing stage: After spray drying, the granules are dried in a fluidized bed until the moisture content is ≤8%.
[0047] Specifically, through the S1 premixing stage, the surfactants are mixed evenly and preliminarily dispersed, thereby providing a good foundation for the subsequent integration of additives and cross-linking reactions; through the S2 additive integration stage, the uniform dispersion of each component is promoted and the stability of the system is improved, thereby enhancing the synergistic effect and overall performance of the composite additives; through the S3 cross-linking reaction stage, the viscoelastic gel network is constructed and the mechanical strength of the particles is improved, thereby providing a guarantee for long-term stable oil displacement in the reservoir; through the S4 aging and granulation stage, the particle size and morphology are controlled, thereby obtaining a salt-resistant viscoelastic particle oil displacement agent with a specific particle size distribution and a porous structure; through the S5 post-processing stage, the spray-dried particles are fluidized-bed dried to a moisture content of ≤3%, which reduces the moisture content of the particles and improves the stability of the particles, thereby ensuring the long-term effective effect and good application performance of the particles in the reservoir.
[0048] Please see the attached Figure 1 , the ultrasonic treatment in S2 is carried out in two stages: The first stage was 35 kHz for 8-10 minutes with a power density of 0.5-0.8 W / cm 3 ; The second stage was performed at 40 kHz for 7-9 minutes, with the power density increased to 1.0-1.2 W / cm 3 .
[0049] Specifically, in the first stage of ultrasonic treatment, low-frequency ultrasound of 35kHz can generate large cavitation bubbles to initially disperse and mix the composite additives, with a power density of 0.5-0.8W / cm 3 It can provide enough energy to break up the agglomerates and make the components evenly dispersed in the system; the second stage of ultrasonic treatment: 40kHz high-frequency ultrasound can generate more cavitation bubbles and stronger shear force, further refine the dispersed system, and increase the power density to 1.0-1.2W / cm 3 It can provide stronger energy to promote the interaction and entanglement between molecules, and improve the stability and reactivity of the composite additive.
[0050] Please see the attached Figure 1 , S4 is subjected to freeze crushing pretreatment before spray drying: The matured material was placed in an environment of -25°C to -15°C for quick freezing for 30-40 minutes, and crushed with a blade crusher at a speed of 800-1000 rpm to a particle size of ≤500 μm, with the blade spacing adjusted to 0.1-0.3 mm.
[0051] Specifically, the mature material is placed in an environment of -25°C to -15°C for rapid freezing for 30-40 minutes, so that the moisture inside the material quickly freezes to form ice crystals, while generating internal stress, causing the material structure to become fragile and more prone to cracks and fractures in the subsequent crushing process, thereby improving the crushing efficiency and uniformity; a blade crusher is used to crush the rapidly frozen material at a moderate speed of 800-1000rpm, avoiding overheating and structural damage of the material caused by excessively high speeds. At the same time, the blade spacing is adjusted to 0.1-0.3mm, ensuring that the material is crushed to an appropriate particle size range (≤500μm), improving the fluidity and uniformity of the material, and creating favorable conditions for spray drying granulation.
[0052] Please see the attached Figure 1 In S4, the spray drying granulation adopts a centrifugal atomizer with an inlet temperature of 165-175°C, an outlet temperature of 85-95°C, an atomizing disk speed of 10000-12000rpm, and a feed rate of 8-12mL / min.
[0053] Specifically, the centrifugal atomizer uses a high-speed rotating atomizing disk to generate centrifugal force to disperse the material into fine droplets, thereby increasing the surface area of the material and accelerating the drying rate, which is conducive to the formation of uniform particles; setting a higher inlet temperature can quickly evaporate the moisture in the material, shorten the drying time, and improve the spray drying efficiency; controlling the outlet temperature at 85-95°C can reduce the material temperature and slow down the drying rate in the later stage of drying, avoid excessive hardening of the particle surface and incomplete evaporation of internal moisture, and ensure the uniformity and integrity of the particle structure; setting a higher atomizing disk speed can further refine the droplet size and increase the droplet surface area, which is conducive to the formation of finer and more uniform particles; controlling the moderate feed rate can balance the material supply and drying rate, avoid feeding too fast resulting in insufficient drying or feeding too slowly affecting production efficiency, and ensure the uniformity and continuity of the particles.
[0054] Please see the attached Figure 1 In step S3, the crosslinking agent is added in two times: 70%-80% of the total amount is added for the first time, and the remaining amount is added after 20 minutes, and the stirring rate is maintained at 400-500 rpm for at least 10 minutes after each addition.
[0055] Specifically, 70%-80% of the total amount added twice plays the role of preliminarily forming the cross-linked network skeleton, providing a basis for the subsequent cross-linking reaction. Adding in batches can avoid the local reaction that is too fast and uneven due to the addition of too much cross-linking agent at one time, which is beneficial to controlling the reaction rate and improving the uniformity of the cross-linked network; adding the remaining cross-linking agent at an interval of 20 minutes after the first addition plays the role of allowing the added cross-linking agent to fully react and diffuse, avoiding local oversaturation and uneven reaction. Appropriate interval time is conducive to controlling the reaction rate and improving the uniformity and stability of the cross-linked network; after each addition of the cross-linking agent, maintain a high stirring rate (400-500rpm) for at least 10 minutes to quickly disperse the cross-linking agent and promote its uniform mixing with other components in the system. A higher stirring rate is conducive to breaking up agglomerates and increasing the reaction rate, and a stirring time of 10 minutes can ensure that the cross-linking agent is fully dispersed and reacted.
[0056] Example 1 1. Technical solution: 1. Group distribution ratio: Nonionic surfactants (C 14 Fatty alcohol polyoxyethylene ether-35, oxyethylene number 35) 25%; anionic surfactant (sodium dodecylbenzene sulfonate with 88% sulfonation degree) 20%; composite auxiliary agent 8%, the balance is deionized water, wherein: Cross-linking agent: copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (molar ratio 16:1), cross-linking degree 1.2%, molecular weight 2.2×10 6 Da; Stabilizer: Hydroxypropyl methylcellulose (viscosity 1800 mPa·s); Solubilizer: polyethylene glycol (molecular weight 4000Da); Cyclodextrin derivative: hydroxypropyl-β-cyclodextrin (degree of substitution 0.9), accounting for 12% of the composite auxiliary agent.
[0057] 2. Preparation process: Premixing stage: add surfactant to deionized water at 42°C and stir at 350 rpm for 30 minutes (paddle diameter 50 mm, container inner diameter 150 mm, inclination angle 50°); Additive integration stage: Heat to 52°C, add polyethylene glycol, hydroxypropyl methylcellulose and cyclodextrin derivatives in sequence, with an interval of 7 minutes between each step; heat to 55°C at 2°C / min, and perform two ultrasonic treatments: 35kHz / 0.7W / cm 3 (10 minutes) to 40kHz / 1.1W / cm 3 (8 minutes); Cross-linking reaction stage: Add the cross-linking agent twice (75% initially, 25% after 20 minutes), stirring at 400 rpm for 10 minutes each time; adjust the pH to 8.0 with 0.2% NaOH, and react at 50°C and 0.3 MPa for 2 hours; Granulation: Under nitrogen protection (purity 99.95%), the temperature was raised to 72°C at 12°C / h, stirred at 200 rpm (paddle spacing 2 mm), and matured for 2.2 hours. Spray drying: inlet temperature 170°C, outlet temperature 90°C, atomizer disk speed 11000 rpm, feed rate 10 mL / min. Post-treatment: fluidized bed drying (62°C, wind speed 2.5 m / s, 40 minutes).
[0058] 3. Test method (according to SY / T5370-2018 standard): Salt resistance: 0.3% of particles at a mineralization of 5×10 4 mg / L(Na + :Ca 2+ =6:1) volume expansion ratio after immersion in the solution for 24 hours; Interfacial tension: The oil-water interfacial tension was measured using a TX500C spinning drop interfacial tension meter. Long-term stability: Viscosity retention after aging for 30 days at 80°C.
[0059] Comparative Example 1 1. Technical solution: 1. Group distribution ratio: Nonionic surfactants (C 14 Fatty alcohol polyoxyethylene ether-35) 25%; anionic surfactant (sodium dodecylbenzene sulfonate with a sulfonation degree of 88%) 20%; composite additives 8%, including: Cross-linking agent: copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (molar ratio 16:1), cross-linking degree 1.2%; Stabilizer: Hydroxypropyl methylcellulose (viscosity 1800 mPa·s); Solubilizer: ethanol (instead of polyethylene glycol); No cyclodextrin derivatives.
[0060] 2. Preparation process: Premixing stage: add surfactant to deionized water at 42°C and stir at 350 rpm for 30 minutes; Additive integration stage: raise the temperature to 52°C, add ethanol and hydroxypropyl methylcellulose in sequence, with an interval of 7 minutes between each step; raise the temperature to 55°C at 2°C / min (no cyclodextrin derivative is added); Cross-linking reaction stage: Add the cross-linking agent twice (75% initially, 25% after 20 minutes), stirring at 400 rpm for 10 minutes each time; adjust the pH to 8.0 with 0.2% NaOH, and react at 50°C and 0.3 MPa for 2 hours; Granulation: Under nitrogen protection, the temperature was raised to 72°C at 12°C / h, stirred at 200 rpm, and matured for 2.2 hours; spray drying: inlet temperature 170°C, outlet temperature 90°C, atomizing disk speed 11000 rpm; Post-treatment: fluidized bed drying (62°C, wind speed 2.5 m / s, 40 minutes).
[0061] 2. Technical Effects: Test items Example 1 Comparative Example 1 Test standards Expansion rate (%) ≤5.8 18.2 SY / T5370-2018 Interfacial tension (mN / m) 0.023 0.098 SY / T5370-2018 Viscosity retention rate (%) 95.4 67.3 GB / T1632-2014 Summary: Cyclodextrin derivatives effectively inhibit ion interference through inclusion complexation, greatly improving salt resistance and stability.
[0062] Example 2 1. Technical solution: 1. Component ratio adjustment: nonionic surfactant (C 16 Fatty alcohol polyoxyethylene ether-40) 28%; anionic surfactant (C 16 α-olefin sulfonate) 23%; composite auxiliary agent 6%; cyclodextrin derivative proportion increased to 14%; the balance is deionized water.
[0063] 2. Process optimization: Premixing stage: same as Example 1; Auxiliary agent integration stage: same as Example 1; Cross-linking reaction: the molar ratio of cross-linker was adjusted to 18:1, and the degree of cross-linking was increased to 1.5%; Ultrasonic enhancement: Ultrasonic power density increased (0.8→1.2W / cm 3 ), the duration was extended to 12 minutes (Phase 1) and 10 minutes (Phase 2); Curing conditions: under nitrogen protection, heating to 75℃ at a rate of 15℃ / h; The aging time is 2-2.5 hours, and the stirring rate is adjusted to 250 rpm; Spray drying granulation was carried out using a centrifugal atomizer with an inlet temperature of 165-175°C, an outlet temperature of 85-95°C, an atomizing disk speed of 10,000-12,000 rpm, and a feed rate of 8-12 mL / min.
[0064] Post-processing stage: same as Example 1; Comparative Example 2 1. Technical solution: 1. Component ratio: Same as Example 1, but the cross-linking agent is changed to linear polyacrylamide (molecular weight 2.5×106 Da, no cross-linking structure).
[0065] 2. Preparation process: Premixing stage: same as Example 1; Auxiliary agent integration stage: same as Example 1; Cross-linking reaction stage: Add all the linear polyacrylamide at once (no incremental addition), stir at 400 rpm for 10 minutes; adjust the pH to 8.0 with 0.2% NaOH, and react at 50°C, 0.3 MPa for 2 hours (no cross-linking structure formation); Maturation and granulation: same as in Example 1; Post-processing: same as Example 1.
[0066] 2. Technical Effects: Test items Example 2 Comparative Example 2 Test standards Expansion rate (%) ≤4.2 21.5 SY / T5370-2018 Interfacial tension (mN / m) 0.019 0.112 SY / T5370-2018 Compressive strength (MPa) 8.3 3.1 ISO604-2002 Summary: By optimizing the cross-linking agent molar ratio and thermodynamic treatment, the honeycomb cross-linked network is denser and the mechanical strength is increased by 160%.
[0067] Example 3 1. Technical solution: 1. Component ratio adjustment: nonionic surfactant (C 12 Fatty alcohol polyoxyethylene ether-30) 22%; anionic surfactant (C 18 α-olefin sulfonate) 18%; composite auxiliary agent 9%; cyclodextrin derivative is changed to sulfobutyl-β-cyclodextrin (substitution degree 1.0); the balance is deionized water.
[0068] 2. Low temperature process optimization: Premix temperature: 40°C (reduced to the lower limit); Auxiliary agent integration stage: same as Example 1; Cross-linking reaction: adopt staged cross-linking (first 70% → 30%), reaction temperature 45℃ (lower limit); Spray drying: feed rate reduced to 8 mL / min, atomizing disk speed 10000 rpm (reduced shear force).
[0069] Ultrasonic treatment stage: same as in Example 1; The aging and granulation stage is the same as that in Example 1.
[0070] Comparative Example 3 1. Technical solution: 1. Component ratio: same as Example 3; 2. Process adjustment: cancel staged cross-linking and low shear granulation.
[0071] 3. Preparation process: Premixing stage: same as Example 3; Auxiliary agent integration stage: same as Example 1; Cross-linking reaction stage: add all cross-linking agents at once, stir at 400 rpm for 10 minutes; adjust pH to 8.0 with 0.2% NaOH, and react at 45°C and 0.3 MPa for 2 hours; Maturation and granulation: same as in Example 1; Spray drying: feed rate increased to 12 mL / min (conventional high speed), atomizing disk speed 12000 rpm (high shear).
[0072] 2. Technical Effect (Test Standard: GB / T2910-2017): Test items Example 3 Comparative Example 3 Test standards Low temperature expansion rate (25℃,%) ≤6.7 14.9 SY / T5370-2018 Low temperature interfacial tension (mN / m) 0.027 0.085 SY / T5370-2018 Permeability recovery rate (%) 89.2 52.4 SY / T6576-2014 Summary: Under low temperature conditions, the penetration recovery rate can be increased by 70% by adjusting the molecular chain flexibility and granulation parameters.
[0073] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.
Claims
1. A salt-resistant viscoelastic particle oil-displacing agent, characterized in that: The following components are included by mass percentage: Nonionic surfactant 22%-28%; Anionic surfactant 18%-23%; Composite additives 6%-9%; The balance is deionized water; The composite auxiliary agent comprises the following components and their mass ratios: Cross-linking agent: polyacrylamide compound, accounting for 40%-60% of the total mass of the composite additive, cross-linking degree 0.8%-1.8%, molecular weight 1.5×10 6 -3×10 6 Da; Stabilizer: Hydroxypropyl methylcellulose, accounting for 20%-30% of the total mass of the composite additives, with a viscosity of 1500-2000 mPa·s; Solubilizer: polyethylene glycol, accounting for 10%-20% of the total mass of the composite additive, with a molecular weight of 3000-5000Da; Cyclodextrin derivatives: hydroxypropyl-β-cyclodextrin or sulfobutyl-β-cyclodextrin with a degree of substitution of 0.6-1.2, which accounts for 10%-15% of the total mass of the composite auxiliary agent.
2. A salt-resistant viscoelastic particle oil-displacing agent according to claim 1, characterized in that: The nonionic surfactant is a fatty alcohol polyoxyethylene ether having 30-45 oxyethylene groups; The anionic surfactant is sodium dodecylbenzenesulfonate with a sulfonation degree of not less than 85% or a carbon chain length of C 14 -C 18 α-olefin sulfonates.
3. A salt-resistant viscoelastic particle oil-displacing agent according to claim 1, characterized in that: The particle size of the oil-displacing agent is 100-200 μm; The particle surface has a porous structure with a porosity of 40%-55%, and the interior of the particle is a honeycomb cross-linked network with a cross-linking density of 3-5mmol / cm³.
4. A salt-resistant viscoelastic particle oil-displacing agent according to claim 3, characterized in that: The average pore size of the porous structure is 0.5-5 μm, and the specific surface area is ≥20 m² / g.
5. A salt-resistant viscoelastic particle oil-displacing agent according to claim 3, characterized in that: The polyacrylamide cross-linking agent is a copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid, and the molar ratio of the two is 15:1-20:
1.
6. A process for preparing a salt-resistant viscoelastic particle oil-displacing agent, characterized in that: A salt-resistant viscoelastic particle oil-displacing agent according to any one of claims 1 to 5, comprising the following steps: S1, premixing stage: add nonionic surfactant and anionic surfactant to deionized water at 40-45°C and stir at 300-400 rpm for 25-35 minutes; S2, additive integration stage: Heat to 50-55°C, add polyethylene glycol first, stir for 5 minutes, add hydroxypropyl methylcellulose, and add cyclodextrin derivative after 8 minutes; heat to the target temperature at a gradient of 2°C / min, and then ultrasonicate the mixture; S3, cross-linking reaction stage: add polyacrylamide cross-linking agent, adjust the pH to 7.5-8.5 with a sodium hydroxide solution with a mass concentration of 0.1%-0.3%, and then react in a closed reactor at 45-55°C for 1.5-2.5 hours, and maintain the reaction pressure at 0.2-0.4MPa; S4, aging and granulation stage: the aging material is heated to 70-75°C at a rate of 10-15°C / h under nitrogen protection for 2-2.5 hours, and then spray-dried and granulated; S5, post-processing stage: After spray drying, the granules are dried in a fluidized bed until the moisture content is ≤3%.
7. The process for preparing a salt-resistant viscoelastic particle oil-displacing agent according to claim 6, wherein: The ultrasonic treatment in S2 is carried out in two stages: The first stage is 35kHz for 8-10 minutes with a power density of 0.5-0.8W / cm³; The second stage is a 7-9 minute process at 40kHz, with the power density increased to 1.0-1.2W / cm³.
8. The process for preparing a salt-resistant viscoelastic particle oil-displacing agent according to claim 6, wherein: S4 freeze crushing pretreatment before spray drying: The matured material was placed in an environment of -25°C to -15°C for quick freezing for 30-40 minutes, and crushed with a blade crusher at a speed of 800-1000 rpm to a particle size of ≤500 μm, with the blade spacing adjusted to 0.1-0.3 mm.
9. The process for preparing a salt-resistant viscoelastic particle oil-displacing agent according to claim 6, wherein: The spray drying granulation in S4 adopts a centrifugal atomizer with an inlet temperature of 165-175°C, an outlet temperature of 85-95°C, an atomizing disk speed of 10000-12000 rpm, and a feed rate of 8-12 mL / min.
10. The process for preparing a salt-resistant viscoelastic particle oil-displacing agent according to claim 6, characterized in that: In step S3, the crosslinking agent is added in two times: 70%-80% of the total amount is added for the first time, and the remaining amount is added after 20 minutes. After each addition, the stirring rate is maintained at 400-500 rpm for at least 10 minutes.