Flexible microgel modulated displacement materials for heavy oil extraction and their application methods

Abstract

This invention discloses a flexible microgel flood control material for heavy oil extraction and its application method, belonging to the field of chemical flood control technology. The material is prepared from the following components by weight percentage: 30%–70% acrylamide monomers, 10%–40% sulfonic acid monomers, 0.1%–5% flexible crosslinking agent, 0.05%–2% initiator, 1%–8% modifier, and the remainder being deionized water. The particle size of the flexible microgel flood control material is 50 nm–500 nm, as detected by dynamic light scattering. This invention uses a compound system of acrylamide monomers, sulfonic acid monomers, flexible crosslinking agent, and modifier. The prepared flexible microgel can remain stable for a long time in formation environments with temperatures ranging from 80℃ to 180℃ and salinity from 5000 to 20000 mg / L, without degradation or aggregation. It is adaptable to the high-temperature and high-salinity geological conditions of different types of heavy oil reservoirs, including ordinary heavy oil, extra-heavy oil, and super-heavy oil, solving the problems of easy failure at high temperatures and performance degradation under high salinity in traditional flood control gels.

Description

Technical Field

[0001] This invention relates to the field of chemical flooding technology, and more specifically, to flexible microgel flooding materials for heavy oil extraction and their application methods. Background Technology

[0002] Heavy oil reservoirs encompass three main types: ordinary heavy oil reservoirs, extra-heavy oil reservoirs, and ultra-heavy oil reservoirs. The mainstream field development methods are waterflooding, steam flooding, or a combination of both. Due to the strong heterogeneity and large differences in pore permeability within the reservoir layers, high-permeability layers easily form dominant water flow channels during development. The injected medium rapidly flows along these high-permeability layers, making it difficult to effectively reach medium- and low-permeability reservoirs. This results in low heavy oil displacement efficiency and a rapid increase in well water cut, severely hindering the overall development effectiveness of heavy oil reservoirs.

[0003] Currently, gel-based moderating materials are commonly used in heavy oil extraction to plug high-permeability layers and control fluid flow direction. However, existing conventional moderating gels generally suffer from high rigidity and lack of flexible deformation capabilities. They also exhibit insufficient stability in high-temperature, high-salinity formation environments, are applicable to only one type of reservoir, and cannot simultaneously adapt to different levels of reservoirs such as ordinary heavy oil, extra-heavy oil, and extra-heavy oil. Furthermore, they are incompatible with various in-situ extraction processes such as steam flooding, water flooding, and combined flooding. At the same time, traditional moderating materials have limited effectiveness in plugging high-permeability layers and do not thoroughly control formation cross-flow. Compared to conventional water flooding processes that rely solely on formation water displacement, the increase in oil recovery is small, failing to meet the actual needs of efficient development of heavy oil reservoirs.

[0004] To address the technical problems of poor reservoir adaptability, weak temperature and salt resistance, low plugging efficiency, and limited recovery rate improvement in existing technologies, this application proposes a flexible microgel modulated displacement material for heavy oil extraction and its application method. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible microgel-based modulated oil recovery material for heavy oil extraction and its application method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The flexible microgel flood control material for heavy oil extraction is prepared from the following components by weight percentage: 30%~70% acrylamide monomers, 10%~40% sulfonic acid monomers, 0.1%~5% flexible crosslinking agent, 0.05%~2% initiator, 1%~8% modifier, and the remainder is deionized water. The particle size of the flexible microgel flood control material is 50nm~500nm. It is stable under conditions of 80℃~180℃ and mineralization of 5000mg / L~20000mg / L, as detected by dynamic light scattering method. The swelling rate upon contact with water is 100%~500%, but it does not swell upon contact with oil. It has deformable and flexible characteristics, with a deformation rate ≥30% under pressure of 0.1~1MPa.

[0007] Preferably, the acrylamide monomer is one or a mixture of acrylamide, methacrylamide, and N-isopropylacrylamide.

[0008] Preferably, the sulfonic acid monomer is one or a mixture of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and sodium vinyl sulfonate.

[0009] Preferably, the flexible crosslinking agent is one or more of polyethylene glycol diacrylate, polyethyleneimine, and N,N'-methylenebisacrylamide, with a crosslinking degree of 5% to 30%, calculated using the gel weight loss method.

[0010] Preferably, the initiator is one or a mixture of potassium persulfate, ammonium persulfate, and azobisisobutyronitrile, and the modifier is one or a mixture of lignin magnesium sulfate, nano-silica, and chitosan. The preparation steps include: adding deionized water to a reaction vessel, adding acrylamide monomers, sulfonic acid monomers, and modifiers in sequence, stirring until completely dissolved, and adjusting the pH of the system to 6-8; adding a flexible crosslinking agent and an initiator, reacting at 40℃-80℃ for 2-6 hours, and after the reaction, centrifuging, ethanol purification, drying at 60-80℃ for 2-4 hours, and granulating to a particle size of 50nm-500nm to obtain the target flexible microgel modulating material.

[0011] A method for applying a flexible microgel-based modulated displacement material in heavy oil extraction includes the following steps: S1. Reservoir Pretreatment: Conduct formation parameter testing on heavy oil reservoirs to determine reservoir temperature, permeability, crude oil viscosity, and formation water salinity, ensuring that the inherent reservoir temperature is 80℃~180℃, the inherent permeability is 10mD~1000mD, the inherent crude oil viscosity is 100mPa·s~10000mPa·s, and the inherent formation water salinity is 5000mg / L~20000mg / L; S2. Preparation of the moderating agent: Mix the flexible microgel moderating material with formation water at a mass ratio of 0.01% to 1%, stir for 10 to 30 minutes, and prepare a uniformly dispersed moderating working solution. S3. Segmented Injection: The regulating and driving working fluid is injected into the reservoir in a segmented manner using a metering pump. The injection rate is 0.5 m³ / d to 5 m³ / d, and the total injection volume is 0.5% to 5% of the reservoir pore volume. During the injection process, the injection pressure is controlled to not exceed the reservoir fracture pressure. S4. Subsequent Displacement: After the adjustment and displacement working fluid is injected, continue to inject formation water into the reservoir for displacement. The displacement rate is 1m³ / d to 8m³ / d until the water cut of the oil well stabilizes, the water cut fluctuation is ≤5% for 7 consecutive days and the crude oil recovery rate no longer increases, and the recovery rate increase is ≤0.1% for 7 consecutive days.

[0012] Preferably, the slug method in step S3 is as follows: first, a pre-slug is injected, which is a mixture of the regulating and displacement working fluid and the displacement aid. The displacement aid is an organic displacement aid selected from fluorocarbon surfactants and polyoxypropylene ethers, and the amount added is 0.1% to 0.5% of the mass of the regulating and displacement working fluid; then, the main slug is injected, which is the regulating and displacement working fluid; finally, a post-slug is injected, which is formation water. The volume ratio of the pre-slug, main slug, and post-slug is 1:3 to 5:1 to 2.

[0013] Preferably, the stirring speed in step S2 is 100 r / min to 300 r / min, and 0.05% to 0.2% of a dispersant can be added during the stirring process. The dispersant is one of sodium dodecylbenzene sulfonate and polyoxyethylene ether.

[0014] Preferably, the injection process in step S3 can be continuous or intermittent. In intermittent injection, the injection is carried out for 1 to 3 days, followed by a 1 to 2-day pause, and the cycle is repeated until the total injection volume is completed.

[0015] Preferably, the heavy oil reservoir is a common heavy oil reservoir, an extra-heavy oil reservoir, or an ultra-heavy oil reservoir, suitable for steam drive, water drive, or combined drive extraction processes; after injection, the oil recovery rate of the reservoir is increased by 5% to 20% compared with conventional water drive. Conventional water drive is a pure formation water drive displacement process without the addition of this regulating and driving material, and the high-permeability layer plugging rate reaches more than 80%, which is detected by dynamic plugging test method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses a compound system of acrylamide monomers, sulfonic acid monomers, flexible crosslinking agents and modifiers to prepare flexible microgels that can exist stably for a long time in formation environments with a salinity of 5000-20000 mg / L at 80℃~180℃ without degradation or aggregation. It can adapt to the high temperature and high salinity geological conditions of different types of heavy oil reservoirs such as ordinary heavy oil, extra-heavy oil and super-heavy oil, and solves the problems of traditional regulating and driving gels being prone to failure at high temperatures and performance degradation under high salinity. The microgels of this application have good flexibility and deformability, and can adapt to irregular pores and throat structures in the formation; at the same time, they have the characteristics of swelling when exposed to water and not swelling when exposed to oil, which can accurately block the dominant channels of water flow in high-permeability layers without blocking the pores of medium and low permeability reservoirs. In the examples, the high-permeability layer blocking rate can reach more than 83.5%, which is much higher than the blocking level of 62.1% of conventional rigid gels, and the blocking durability and targeting are greatly improved. The composition of each component in this application is reasonable and the selection of monomers is rich, which can be flexibly adapted and adjusted according to different reservoir conditions. The preparation process has mild reaction conditions and controllable parameters. After centrifugation, ethanol purification, constant temperature drying and precise granulation, the microgel particles are uniform in size, high in purity and have good batch consistency. The process is simple and easy to realize industrial mass production.

[0017] (2) The application method of this invention sets up a process of pre-screening reservoir parameters, precise mixing, three-stage injection of pre-, main-, and post-plant plugs, and controllable speed for subsequent displacement; it can flexibly adopt continuous injection or intermittent cyclic injection methods, strictly control the injection pressure to avoid damaging the formation structure; the addition of dispersants and drainage aids can reduce injection resistance and avoid microgel aggregation, and quantitative judgment criteria are set for the displacement endpoint, with strong process standardization and repeatability. The moderating and displacement materials and processes of this application can be adapted to the mainstream heavy oil extraction processes of water drive, steam drive, and composite drive, without the need to modify the existing equipment on site, and can be directly applied, with strong versatility and low promotion threshold. This application can increase the recovery rate of heavy oil crude oil by 8.9% to 17.2% compared with conventional water drive; compared with traditional rigid moderating and displacement materials, it not only greatly improves the plugging and displacement effect, but also effectively reduces the on-site application cost, and improves the utilization of heavy oil reservoir reserves and the economic benefits of resource development. This application avoids the drawbacks of gels being prone to brittleness in formations, having poor porosity, and easily damaging low-permeability layers; compared with materials without modifiers, it significantly improves high-temperature structural strength and resistance to degradation; compared with single-stage plug injection process, three-stage plug injection method makes the distribution of the modulated drive system more uniform, effectively expands the swept volume of medium and low permeability layers, and has obvious comprehensive modulated drive efficiency advantages. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Example: The flexible microgel modulator for heavy oil extraction is prepared from the following components by weight percentage: 30%~70% acrylamide monomers, 10%~40% sulfonic acid monomers, 0.1%~5% flexible crosslinking agent, 0.05%~2% initiator, 1%~8% modifier, and the remainder is deionized water. The particle size of the flexible microgel modulator is 50nm~500nm. It is stable under conditions of 80℃~180℃ and mineralization of 5000mg / L~20000mg / L, as detected by dynamic light scattering method. The swelling rate in water is 100%~500%, but it does not swell in oil. It has deformable and flexible characteristics, with a deformation rate ≥30% under pressure of 0.1~1MPa, which can achieve selective plugging of high-permeability layers. The synergistic effect of each component ensures the basic structural stability of the microgel and endows it with excellent temperature and salt resistance, making it suitable for various heavy oil reservoir environments with temperatures ranging from 80℃ to 180℃ and mineralization from 5000mg / L to 20000mg / L. This addresses the technical pain points of existing gel-based moderating and flooding materials, such as easy degradation and poor stability under high temperature and high mineralization conditions. The particle size design of 50nm to 500nm allows it to smoothly enter reservoir pores. Its characteristic of swelling when exposed to water but not when exposed to oil enables precise selective plugging of high-permeability layers, avoiding blockage of low-permeability layers. At the same time, its deformable and flexible characteristics allow it to adapt to the complex morphology of formation pores, improving the durability and effectiveness of the plugging.

[0021] In this application, the acrylamide monomer is one or more of acrylamide, methacrylamide, and N-isopropylacrylamide; the acrylamide monomer has good polymerization activity and is easy to cross-link with other monomers to form a structurally stable microgel framework; multiple monomers can be flexibly combined, and the monomer ratio can be adjusted according to different reservoir conditions to optimize the expansion performance and stability of the microgel, expand the compatibility range of the material, and compared with a single monomer, the use of mixtures can take into account the flexibility and mechanical strength of the microgel, and avoid the performance shortcomings of microgels prepared by a single monomer.

[0022] In this application, the sulfonic acid monomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and sodium vinyl sulfonate, used to improve the salt resistance of the material. The sulfonic acid groups contained in the sulfonic acid monomer molecules have extremely strong hydrophilicity and salt resistance, which can effectively resist the erosion of salt ions in formation water, prevent the microgel from agglomerating and degrading due to the action of salt ions, and significantly improve the salt resistance of the material. At the same time, the sulfonic acid groups can enhance the binding ability of the microgel with water, optimize its water swelling performance, and ensure that it can still maintain a good sealing effect in high-salinity reservoirs, solving the problem that the existing moderating and flooding materials have insufficient salt resistance and are not suitable for high-salinity heavy oil reservoirs.

[0023] In this application, the flexible crosslinking agent is one or more of polyethylene glycol diacrylate, polyethyleneimine, and N,N'-methylenebisacrylamide, with a crosslinking degree of 5% to 30%, calculated using the gel weight loss method. This imparts the material with flexible deformation capability, ensuring that the microgel is not easily broken during injection and that it can deform under formation pressure to adapt to pores and throats of different sizes, thereby improving the coverage of the sealing. At the same time, this type of crosslinking agent has good compatibility with other monomers and can form a uniform and stable crosslinking network, further improving the temperature stability and service life of the microgel.

[0024] In this application, the initiator is one or a mixture of potassium persulfate, ammonium persulfate, and azobisisobutyronitrile, and the modifier is one or a mixture of lignin magnesium sulfate, nano silica, and chitosan. The preparation steps include: adding deionized water to a reaction vessel, adding acrylamide monomers, sulfonic acid monomers, and modifiers in sequence, stirring until completely dissolved, and adjusting the pH of the system to 6-8; adding a flexible crosslinking agent and an initiator, reacting at 40℃-80℃ for 2-6 hours, centrifuging after the reaction, purifying with ethanol, drying at 60-80℃ for 2-4 hours, and granulating to a particle size of 50nm-500nm to obtain the target flexible microgel modulating material; the modifier can further optimize the performance of the microgel. Lignosulfate, nano silica, and chitosan all have good stability and compatibility, which can enhance the mechanical strength, temperature resistance, and sealing performance of the microgel, and prolong its effective action time in the formation. The preparation steps are scientifically designed and the process is simple. The parameters (pH value, reaction temperature, reaction time, drying temperature, etc.) work together to achieve batch and stable preparation of microgels. The centrifugation and ethanol purification steps can effectively remove impurities and ensure the purity and performance consistency of the materials. Granulation to the specified particle size ensures that the microgels can smoothly enter the reservoir pores and improve the application effect. Moreover, the entire preparation process is simple to operate and cost-controllable, making it suitable for industrial production.

[0025] Please see Figure 1 A method for applying a flexible microgel modulated displacement material in heavy oil extraction includes the following steps: S1. Reservoir Pretreatment: Formation parameters are detected in heavy oil reservoirs to determine reservoir temperature, permeability, crude oil viscosity, and formation water salinity. This ensures that the inherent reservoir temperature is 80℃~180℃, inherent permeability is 10mD~1000mD, inherent crude oil viscosity is 100mPa·s~10000mPa·s, and inherent formation water salinity is 5000mg / L~20000mg / L. This step accurately determines the inherent parameters of the reservoir, providing a scientific basis for subsequent formulation of modifiers and optimization of injection parameters. It avoids material waste and poor modifier effects caused by blind injection, ensuring that modifiers are precisely matched with reservoir conditions, improving modifier efficiency from the source. At the same time, it can detect reservoir anomalies in advance, ensuring the smooth progress of subsequent applications.

[0026] S2. Preparation of the flood control agent: Mix the flexible microgel flood control material with formation water at a mass ratio of 0.01%~1% and stir for 10~30 min to prepare a uniformly dispersed flood control working fluid. The stirring speed is 100 r / min~300 r / min. During the stirring process, 0.05%~0.2% of a dispersant can be added. The dispersant is one of sodium dodecylbenzene sulfonate and polyoxyethylene ether. The addition of the dispersant can further optimize the dispersion effect, prevent the microgel from agglomerating during preparation and injection, and at the same time improve the fluidity of the flood control working fluid and reduce the injection resistance. Sodium dodecylbenzene sulfonate and polyoxyethylene ether dispersants have good compatibility with the flood control material, will not affect the performance of the microgel, and are low in cost and easy to obtain.

[0027] S3. Segmented Injection: The regulating fluid is injected into the reservoir in a segmented manner using a metering pump at a rate of 0.5 m³ / d to 5 m³ / d. The total injection volume is 0.5% to 5% of the reservoir pore volume. During the injection process, the injection pressure is controlled to not exceed the reservoir fracture pressure. The injection process can be carried out continuously or intermittently. In intermittent injection, injection is carried out for 1 to 3 days, followed by a 1 to 2-day pause, and the cycle is repeated until the total injection volume is completed. The two methods of continuous and intermittent injection can be flexibly selected. Intermittent injection allows the microgel to have sufficient time to expand and be adsorbed in the reservoir pores, improving the sealing effect and adapting to heavy oil reservoirs with different heterogeneity, thus expanding the application scenarios.

[0028] S4. Subsequent Displacement: After the working fluid for adjusting the displacement is injected, formation water is continued to be injected into the reservoir for displacement at a rate of 1 m³ / d to 8 m³ / d until the water cut of the oil well stabilizes, with water cut fluctuations ≤5% for 7 consecutive days and oil recovery no longer increasing, and recovery rate increase ≤0.1% for 7 consecutive days. The subsequent displacement step can push the injected water that has been blocked by microgel and redirected to fully affect the medium and low permeability reservoir, effectively displacing the heavy oil in it to the oil well and improving the oil recovery rate.

[0029] In this application, the slug method in step S3 is as follows: first, a pre-slug is injected, which is a mixture of the regulating and displacement working fluid and the displacement aid. The displacement aid is an organic displacement aid selected from fluorocarbon surfactants and polyoxypropylene ethers, and the amount added is 0.1% to 0.5% of the mass of the regulating and displacement working fluid; then, the main slug is injected, which is the regulating and displacement working fluid; finally, a post-slug is injected, which is formation water. The volume ratio of the pre-slug, main slug, and post-slug is 1:3 to 5:1 to 2. The addition of drainage aids to the pre-slug can reduce the interfacial tension between the regulating fluid and the formation rock, decrease injection resistance, and clean formation pores, creating favorable conditions for the injection and plugging of the main slug. Fluorocarbon surfactants and polyoxypropylene ether-based organic drainage aids exhibit excellent temperature and salt resistance, good compatibility with regulating fluid materials, and do not affect the plugging performance of the microgel. An addition of 0.1% to 0.5% can control costs while ensuring drainage effectiveness. The optimized volume ratio design of the pre-slug, main slug, and post-slug achieves a synergistic effect of "cleaning-plugging-displacement." The pre-slug cleans the formation, the main slug achieves efficient plugging, and the post-slug promotes the full functioning of the main slug, further enhancing the plugging and displacement effects. Compared to single-slug injection, segmented slug injection significantly improves the targeting and effectiveness of regulating fluid. In this application, the heavy oil reservoir is a common heavy oil reservoir, an extra-heavy oil reservoir, or an ultra-heavy oil reservoir, suitable for steam drive, water drive, or combined drive extraction processes; after injection, the crude oil recovery rate of the reservoir is increased by 5% to 20% compared with conventional water drive. Conventional water drive is a pure formation water drive displacement process without the addition of this moderating material, and the high-permeability layer plugging rate reaches more than 80%, which is detected by dynamic plugging test method. This modified oil recovery material and its application method have a wide range of applications, compatible with various heavy oil reservoirs including ordinary heavy oil, extra-heavy oil, and super-heavy oil. It is also compatible with mainstream field exploitation processes such as steam flooding, water flooding, and combined flooding, without requiring large-scale modifications to existing exploitation equipment, thus reducing application costs and expanding application scenarios. The high-permeability layer plugging rate reaches over 80%, effectively blocking the dominant water flow channels in high-permeability layers, reducing injection medium cross-flow, and forcing injected water to redirect to medium- and low-permeability reservoirs, significantly improving oil recovery by 5% to 20% compared to conventional water flooding. This effectively addresses the technical pain points of low displacement efficiency and limited recovery rate improvement in existing heavy oil reservoir development, improving the economic efficiency and resource utilization of heavy oil reservoir development. The plugging rate is detected using a dynamic plugging experiment method, with results more closely reflecting actual formation conditions, providing accurate and reliable data that precisely reflects the plugging effect of the material.

[0030] Example 1: Conventional heavy oil reservoir + waterflooding process 1.1 Preparation of modulated drive materials Ingredients by weight percentage: Acrylamide (45%), 2-acrylamido-2-methylpropanesulfonic acid (25%), polyethylene glycol diacrylate (1.5%), potassium persulfate (0.8%), nano silica (4%), and the remainder is deionized water (23.7%).

[0031] Preparation steps: Deionized water was added to the reaction vessel, followed by acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and nano-silica. The mixture was stirred until completely dissolved, and the pH of the system was adjusted to 7. Polyethylene glycol diacrylate and potassium persulfate were added, and the mixture was reacted at 60°C for 4 hours. After the reaction was completed, the mixture was centrifuged, purified with ethanol, dried at 70°C for 3 hours, and granulated to a particle size of 200 nm to obtain a flexible microgel modulated material.

[0032] 1.2 Application Method S1. Reservoir Pretreatment: Parameters of ordinary heavy oil reservoirs were tested to determine that the reservoir's inherent temperature was 100℃, inherent permeability was 150mD, inherent crude oil viscosity was 500mPa·s, and inherent formation water salinity was 8000mg / L, which met the suitability conditions. S2. Preparation of the moderating agent: The flexible microgel moderating material prepared above is mixed with formation water at a mass ratio of 0.3%, stirred at a speed of 200 r / min for 20 min, and 0.1% sodium dodecylbenzenesulfonate dispersant is added to prepare a uniformly dispersed moderating working solution. S3. Segmented Injection: Injected via metering pump in a slug manner, with the volume ratio of the pre-slug (adjusting fluid + 0.3% fluorocarbon surfactant for drainage), main slug (adjusting fluid), and post-slug (formation water) being 1:4:1.5. The injection rate is 2 m³ / d, and the total injection volume is 2% of the reservoir pore volume. The injection pressure is controlled below the reservoir fracture pressure, and a continuous injection method is adopted. S4. Subsequent Displacement: After injection, inject formation water at a rate of 4 m³ / d to displace the oil well until the water cut fluctuation of the oil well is ≤5% for 7 consecutive days and the recovery rate increase is ≤0.1%, then stop the displacement.

[0033] 1.3 Performance Test Results The moderating material remains stable under these reservoir conditions, without degradation or aggregation; the high-permeability layer plugging rate is 86.3%; the crude oil recovery rate is 12.7% higher than that of conventional waterflooding; no modification to existing waterflooding equipment is required during application, and the application cost is 18% lower than that of conventional moderating materials.

[0034] Example 2: Extra-heavy oil reservoir + steam drive process 2.1 Preparation of modulated drive materials Ingredients by weight percentage: methacrylamide (55%), sodium styrene sulfonate (20%), polyethyleneimine (2.2%), ammonium persulfate (1.2%), chitosan (5%), and the remainder is deionized water (16.6%).

[0035] Preparation steps: Deionized water was added to the reaction vessel, followed by the addition of methacrylamide, sodium styrene sulfonate, and chitosan. The mixture was stirred until completely dissolved, and the pH of the system was adjusted to 6.5. Polyethyleneimine and ammonium persulfate were added, and the mixture was reacted at 70°C for 3 hours. After the reaction was completed, the mixture was centrifuged, purified with ethanol, dried at 75°C for 2.5 hours, and granulated to a particle size of 300 nm to obtain the flexible microgel modulated material.

[0036] 2.2 Application Method S1. Reservoir Pretreatment: The parameters of the extra-heavy oil reservoir were detected, and the inherent temperature of the reservoir was determined to be 150℃, the inherent permeability was 300mD, the inherent crude oil viscosity was 3000mPa·s, and the inherent salinity of the formation water was 15000mg / L, which met the suitable conditions. S2. Preparation of the modulating agent: The flexible microgel modulating material prepared above is mixed with formation water at a mass ratio of 0.6%, stirred at a speed of 250 r / min for 25 min, and 0.15% polyoxyethylene ether dispersant is added to prepare a uniformly dispersed modulating working solution. S3. Segmented Injection: Injected via metering pump in a slug manner, with the volume ratio of the pre-slug (adjusting fluid + 0.4% polyoxypropylene ether drainage aid), main slug (adjusting fluid), and post-slug (formation water) being 1:5:2. The injection rate is 3 m³ / d, and the total injection volume is 3.5% of the reservoir pore volume. The injection pressure is controlled below the reservoir fracture pressure, and an intermittent injection method is adopted (inject for 2 days, stop for 1 day, and cycle until the total injection volume is completed). S4. Subsequent Displacement: After injection, combined with steam drive technology, inject formation water at a rate of 6 m³ / d to displace the oil well until the water cut fluctuation of the oil well is ≤5% for 7 consecutive days and the recovery rate increase is ≤0.1%, then stop the displacement.

[0037] 2.3 Performance Test Results The controlled-drive material exhibits good stability under high temperature and high salinity conditions and can withstand a 150℃ steam drive environment; the high-permeability layer plugging rate is 89.7%; the crude oil recovery rate is 17.2% higher than that of conventional water drive; it is compatible with existing steam drive equipment without additional modifications and has strong adaptability to various application scenarios.

[0038] Example 3: Extra-heavy oil reservoir + composite flooding process 3.1 Preparation of modulated drive materials Ingredients by weight percentage: N-isopropylacrylamide (35%), sodium vinyl sulfonate (30%), N,N'-methylenebisacrylamide (0.8%), azobisisobutyronitrile (0.5%), magnesium lignin sulfate (3%), and the remainder is deionized water (30.7%).

[0039] Preparation steps: Deionized water was added to the reaction vessel, followed by N-isopropylacrylamide, sodium vinyl sulfonate, and magnesium lignin sulfate. The mixture was stirred until completely dissolved, and the pH of the system was adjusted to 7.5. N,N'-methylenebisacrylamide and azobisisobutyronitrile were added, and the mixture was reacted at 50°C for 5 hours. After the reaction was completed, the mixture was separated by centrifugation, purified with ethanol, dried at 65°C for 3.5 hours, and granulated to a particle size of 100 nm to obtain the flexible microgel modulated driving material.

[0040] 3.2 Application Method S1. Reservoir Pretreatment: The parameters of the extra-heavy oil reservoir were detected, and the inherent temperature of the reservoir was determined to be 120℃, the inherent permeability was 800mD, the inherent crude oil viscosity was 8000mPa·s, and the inherent formation water salinity was 12000mg / L, which met the suitable conditions. S2. Preparation of the regulating agent: The flexible microgel regulating material prepared above is mixed with formation water at a mass ratio of 0.1%, stirred at a speed of 150 r / min for 15 min, and 0.08% sodium dodecylbenzenesulfonate dispersant is added to prepare a uniformly dispersed regulating working solution. S3. Segmented Injection: Injected via metering pump in a slug manner, with the volume ratio of the pre-slug (adjusting fluid + 0.2% fluorocarbon surfactant for drainage), the main slug (adjusting fluid), and the post-slug (formation water) being 1:3:1. The injection rate is 1 m³ / d, and the total injection volume is 1% of the reservoir pore volume. The injection pressure is controlled below the reservoir fracture pressure, and a continuous injection method is adopted. S4. Subsequent Displacement: After injection, combined with the composite displacement process, inject formation water at a rate of 3 m³ / d to displace the oil well until the water cut fluctuation of the oil well is ≤5% for 7 consecutive days and the recovery rate increase is ≤0.1%, then stop the displacement.

[0041] 3.3 Performance Test Results The modulating flooding material exhibits good dispersibility and excellent deformability in the high-viscosity environment of extra-heavy oil reservoirs; it achieves a high-permeability layer plugging rate of 83.5%; the crude oil recovery rate is 8.9% higher than that of conventional waterflooding; it is compatible with composite flooding processes and existing extraction equipment, and its application cost is controllable.

[0042] II. Comparative Example Comparative Example 1: Conventional rigid gel modulated drive material (without flexible crosslinking agent) 1.1 Material preparation: Except for replacing the flexible crosslinking agent with a rigid crosslinking agent (epoxychloropropane) and adjusting the degree of crosslinking to 40%, the other ingredient ratios and preparation steps are completely the same as in Example 1.

[0043] 1.2 Application method: The application method is completely consistent with that in Example 1 (ordinary heavy oil reservoir + water drive process).

[0044] 1.3 Performance test results: Rigid gels are prone to brittle fracture under reservoir conditions and have poor stability; the high-permeability layer plugging rate is 62.1%; the crude oil recovery rate is only 3.8% higher than that of conventional waterflooding; due to its high rigidity, it cannot adapt to complex pore structures, has poor plugging durability, and is prone to clogging low-permeability layers.

[0045] Comparative Example 2: Modified Drive Material without Modifier 2.1 Material preparation: Except for the absence of modifier (nano silica), the proportions of other ingredients and the preparation steps are completely the same as in Example 2.

[0046] 2.2 Application method: The application method is completely consistent with that in Example 2 (extra-heavy oil reservoir + steam drive process).

[0047] 2.3 Performance test results: The modifier-free waterflooding material is easily degraded at high temperature (150℃) and has poor adaptability to mineralization; the high-permeability layer plugging rate is 70.3%; the oil recovery rate is 7.5% higher than that of conventional waterflooding; the material has insufficient mechanical strength and is easily broken during injection, making it impossible to achieve long-term effective plugging.

[0048] Comparative Example 3: Single Injection Method (without segmented plug injection) 3.1 Material preparation: The preparation of the modulated driving material is completely consistent with that in Example 3.

[0049] 3.2 Application method: Except for step S3, which uses a single main slug injection (without injecting the front and rear slugs), the other application steps are completely consistent with Example 3 (extra-heavy oil reservoir + composite flooding process).

[0050] 3.3 Performance test results: The single injection method resulted in high injection resistance and uneven dispersion of the working fluid; the high-permeability layer plugging rate was 75.8%; the oil recovery rate was 5.2% higher than that of conventional waterflooding; local agglomeration occurred during the injection process, resulting in uneven plugging effect and failure to fully reach medium and low permeability reservoirs.

[0051] III. Comparative Analysis of Examples and Comparative Cases The detection results of Examples 1-3 and Comparative Examples 1-3 above show that: 1. The flexible microgel modulating and driving materials of this application (Examples 1-3) have significantly improved stability and deformability compared with conventional rigid gels (Comparative Example 1) through the synergistic effect of flexible crosslinking agents and modifiers, with a blocking rate increased by more than 20% and a recovery rate increased by more than 5%, which can effectively avoid clogging of low-permeability layers. 2. The addition of modifiers (Example 2 vs Comparative Example 2) can significantly improve the temperature and salt resistance and mechanical strength of the modulating and driving materials, avoid high-temperature degradation, increase the plugging rate by more than 19%, increase the recovery rate by nearly 10%, and ensure long-term effective plugging; 3. The segmented slug injection method (Example 3 vs Comparative Example 3) can reduce injection resistance, achieve uniform dispersion of the modulating fluid, increase the plugging rate by more than 7%, increase the recovery rate by 3.7%, and fully affect medium and low permeability reservoirs to improve displacement efficiency. 4. The moderating and flooding materials and application methods of this application are applicable to various reservoirs of ordinary heavy oil, extra-heavy oil, and super-heavy oil, and are compatible with multiple processes such as water flooding, steam flooding, and combined flooding. No modification of existing equipment is required, the application cost is low, the plugging rate reaches more than 80%, and the recovery rate is increased by 5% to 20% compared with conventional water flooding. It effectively solves the pain points of existing technologies and improves the economic efficiency and resource utilization of heavy oil reservoir development.

[0052] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flexible microgel-based modulated displacement material for heavy oil extraction, characterized in that, It is prepared from the following components by weight percentage: 30%~70% acrylamide monomers, 10%~40% sulfonic acid monomers, 0.1%~5% flexible crosslinking agent, 0.05%~2% initiator, 1%~8% modifier, and the remainder is deionized water; the particle size of the flexible microgel modulated material is 50nm~500nm, and it is stable under conditions of 80℃~180℃ and mineralization of 5000mg / L~20000mg / L, as detected by dynamic light scattering method. It has a water swelling rate of 100%~500%, does not swell when exposed to oil, and has deformable and flexible characteristics, with a deformation rate ≥30% under pressure of 0.1~1MPa.

2. The flexible microgel modulated displacement material for heavy oil extraction according to claim 1, characterized in that, The acrylamide monomer is one or a mixture of acrylamide, methacrylamide, and N-isopropylacrylamide.

3. The flexible microgel modulated displacement material for heavy oil extraction according to claim 1, characterized in that, The sulfonic acid monomer is one or a mixture of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and sodium vinyl sulfonate.

4. The flexible microgel modulated displacement material for heavy oil extraction according to claim 1, characterized in that, The flexible crosslinking agent is one or more of polyethylene glycol diacrylate, polyethyleneimine, and N,N'-methylenebisacrylamide, with a crosslinking degree of 5% to 30%, calculated using the gel weight loss method.

5. The flexible microgel modulated displacement material for heavy oil extraction according to claim 1, characterized in that, The initiator is one or a mixture of potassium persulfate, ammonium persulfate, and azobisisobutyronitrile; the modifier is one or a mixture of magnesium lignin sulfate, nano silica, and chitosan. The preparation steps include: adding deionized water to a reaction vessel, adding acrylamide monomers, sulfonic acid monomers, and modifiers in sequence, stirring until completely dissolved, and adjusting the pH of the system to 6-8; adding a flexible crosslinking agent and an initiator, reacting at 40℃-80℃ for 2-6 hours, and after the reaction, centrifuging, ethanol purification, drying at 60-80℃ for 2-4 hours, and granulating to a particle size of 50nm-500nm to obtain the target flexible microgel modulated material.

6. A method for applying the flexible microgel modulated displacement material for heavy oil extraction as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Reservoir Pretreatment: Conduct formation parameter testing on heavy oil reservoirs to determine reservoir temperature, permeability, crude oil viscosity, and formation water salinity, ensuring that the inherent reservoir temperature is 80℃~180℃, the inherent permeability is 10mD~1000mD, the inherent crude oil viscosity is 100mPa·s~10000mPa·s, and the inherent formation water salinity is 5000mg / L~20000mg / L; S2. Preparation of the moderating agent: Mix the flexible microgel moderating material with formation water at a mass ratio of 0.01% to 1%, stir for 10 to 30 minutes, and prepare a uniformly dispersed moderating working solution. S3. Segmented Injection: The regulating and driving working fluid is injected into the reservoir in a segmented manner using a metering pump. The injection rate is 0.5 m³ / d to 5 m³ / d, and the total injection volume is 0.5% to 5% of the reservoir pore volume. During the injection process, the injection pressure is controlled to not exceed the reservoir fracture pressure. S4. Subsequent Displacement: After the adjustment and displacement working fluid is injected, continue to inject formation water into the reservoir for displacement. The displacement rate is 1m³ / d to 8m³ / d until the water cut of the oil well stabilizes, the water cut fluctuation is ≤5% for 7 consecutive days and the crude oil recovery rate no longer increases, and the recovery rate increase is ≤0.1% for 7 consecutive days.

7. The application method of the flexible microgel modulated displacement material for heavy oil extraction according to claim 6, characterized in that, The slug method described in step S3 is as follows: First, a pre-slug is injected, which is a mixture of the regulating and displacement working fluid and the displacement aid. The displacement aid is an organic displacement aid selected from fluorocarbon surfactants and polyoxypropylene ethers, and the amount added is 0.1% to 0.5% of the mass of the regulating and displacement working fluid; then, the main slug is injected, which is the regulating and displacement working fluid; finally, a post-slug is injected, which is formation water. The volume ratio of the pre-slug, main slug, and post-slug is 1:3 to 5:1 to 2.

8. The application method of the flexible microgel modulated displacement material for heavy oil extraction according to claim 6, characterized in that, In step S2, the stirring speed is 100 r / min to 300 r / min. During the stirring process, 0.05% to 0.2% of a dispersant can be added. The dispersant is one of sodium dodecylbenzene sulfonate or polyoxyethylene ether.

9. The application method of the flexible microgel modulated displacement material for heavy oil extraction according to claim 6, characterized in that, In step S3, the injection process can be continuous or intermittent. In intermittent injection, the injection is carried out for 1 to 3 days, followed by a 1 to 2-day pause, and this cycle is repeated until the total injection volume is completed.

10. The application method of the flexible microgel modulated displacement material for heavy oil extraction according to claim 6, characterized in that, The heavy oil reservoir is a typical heavy oil reservoir, an extra-heavy oil reservoir, or an ultra-heavy oil reservoir, suitable for steam drive, water drive, or combined drive extraction processes. After injection, the oil recovery rate of the reservoir is increased by 5% to 20% compared with conventional water drive. Conventional water drive is a pure formation water drive process without the addition of this moderating material. The high-permeability layer plugging rate reaches more than 80%, which is detected by dynamic plugging test method.

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