Surfactant for improving recovery efficiency of oil field and preparation method of surfactant

Abstract

The invention discloses a surfactant for improving the recovery efficiency of an oil field and a preparation method of the surfactant, and belongs to the technical field of oilfield chemical agents. The surfactant is prepared from an amphiphilic block dendritic silicon polymer, a multifunctional response type fluorocarbon surfactant, rhamnolipid, dodecyl dimethyl amine oxide, zinc oxide nanoparticles, xanthan gum, sodium chloride and deionized water according to a specific weight part ratio. The preparation method comprises the following steps: dissolving xanthan gum in water to form a colloidal solution, adding other surfactants and salt components, and finally adding two key modified compounds and nanoparticles for homogeneous dispersion. The surfactant disclosed by the invention has the characteristics of ultralow interfacial tension, environmental response and excellent stability, and can remarkably improve the crude oil recovery rate.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical agents, specifically to a surfactant for enhancing oil recovery in oilfields and its preparation method. Background Technology

[0002] Oilfield development, as a crucial link in global energy supply, directly impacts the efficiency and economic value of energy resource utilization based on its ultimate recovery rate. In the development of conventional and unconventional oil and gas reservoirs, primary oil recovery relying on natural energy and secondary oil recovery using water injection to maintain pressure typically only extract a limited portion of the original underground oil reserves, leaving a large amount of crude oil trapped within complex geological structures. This residual oil is in a capillary-driven, bound state, and its initiation and migration require overcoming significant interfacial tension barriers. This makes chemical flooding technology, particularly surfactant flooding, a key technology for enhancing oil recovery, focusing on improving microscopic oil displacement efficiency. Surfactants, through their directional adsorption capacity at the oil-water interface, can significantly reduce the interfacial tension between the two phases, alter the surface wetting characteristics of reservoir rocks, and form a stable emulsion system. This effectively mobilizes and strips the oil film adhering to the rock surface, transforming the originally non-flowing residual oil into a flowable state. However, as oil and gas exploration and development expands into deeper and more complex geological environments, harsh reservoir conditions such as high temperature, high salinity, and low permeability pose severe challenges to traditional surfactant systems.

[0003] Current surfactant technology faces multiple technical bottlenecks when dealing with complex reservoir conditions. At high temperatures, the increased thermal motion of surfactant molecules easily disrupts their ordered assembly structure, leading to a significant decrease in interfacial activity and even irreversible degradation phenomena such as molecular chain breakage. In highly salinized formation water, especially in conditions rich in calcium and magnesium polyvalent ions, ionic surfactants are prone to salting out or forming insoluble precipitates, not only causing agent inactivation but also potentially clogging reservoir pore structures and causing secondary damage to the reservoir. Furthermore, the adsorption loss of surfactants on rock and mineral surfaces remains a key factor restricting the economic viability of chemical flooding technology. Large amounts of agents are ineffectively retained in the reservoir, significantly increasing operating costs and making it difficult to maintain the expected surfactant concentration at the displacement front. Although researchers have developed novel systems in recent years, including temperature- and salt-resistant zwitterionic surfactants, organosilicon surfactants, and fluorocarbon surfactants, these materials still have significant limitations in practical applications. These limitations include complex synthesis processes leading to high costs, poor environmental compatibility causing ecological concerns, or limited functionality making it difficult to meet the multiple requirements of complex reservoir conditions.

[0004] Faced with the technical shortcomings of existing surfactant systems, such as insufficient stability under high-temperature and high-salt environments, excessive adsorption on rock surfaces, and lack of intelligent response capabilities, there is an urgent need to develop a new generation of high-efficiency surfactant systems. An ideal new surfactant should possess excellent interfacial activity, superior temperature and salt resistance, low adsorption loss characteristics, and intelligent environmental response capabilities, autonomously adjusting its interfacial behavior according to changes in reservoir conditions. Furthermore, from an industrial application perspective, the synthesis process of new surfactants should be characterized by a rational route, readily available raw materials, and mild conditions to ensure the feasibility of large-scale production. In the context of increasingly stringent environmental protection requirements, new surfactant systems also need to consider environmentally friendly characteristics, using components with good biodegradability as much as possible to reduce potential impacts on the ecological environment. These technological requirements collectively point to the need for innovation at the molecular structure design level. By constructing novel surfactant molecules with specific topological structures and functional groups, efficient, stable, and intelligent oil displacement performance can be achieved under complex reservoir conditions, thereby opening up new technical avenues for enhanced oil recovery technologies in oilfields. Summary of the Invention

[0005] The purpose of this invention is to provide a surfactant for enhancing oil recovery in oilfields and its preparation method, which solves the technical problems of existing surfactants having poor chemical stability under high temperature and high salinity reservoir conditions, high adsorption loss on rock surfaces, and low utilization efficiency of residual oil in complex pores.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing a surfactant for enhancing oil recovery in oilfields, comprising the following steps: S1. Heat deionized water to 48-52℃, add xanthan gum while stirring, and continue stirring until completely dissolved to form a colloidal solution; then heat the colloidal solution to 58-62℃, add rhamnolipid, dodecyl dimethylamine oxide and sodium chloride in sequence, and continue stirring; S2. Then add the amphiphilic block dendritic silicone polymer and the multifunctional responsive fluorocarbon surfactant, stir and mix, then add zinc oxide nanoparticles and disperse using a high-speed homogenizer.

[0007] In this invention, the preparation mechanism of the surfactant for oilfield enhanced oil recovery is manifested in the formation of a stable composite oil displacement system through physical mixing and self-assembly of multiple functional components. During the preparation process, xanthan gum, a biopolymer, is first dissolved in water under heating and stirring. Its polysaccharide molecular chains unfold in water and form a three-dimensional network structure through hydrogen bonding, providing the necessary viscosity basis for the entire system. Subsequently, commercially available surfactants such as rhamnolipid and dodecyl dimethylamine oxide, as well as sodium chloride electrolyte, are added. After dissolution, they are rapidly dispersed in the xanthan gum aqueous solution. The biocompatibility and emulsifying ability of rhamnolipid, combined with the mild and synergistic effect of dodecyl dimethylamine oxide, initially reduce the interfacial tension of the system. The addition of sodium chloride regulates the ionic strength through electrostatic shielding, affecting the morphology and size of the surfactant micelles. When the two core synthetic products, an amphiphilic block dendritic silicon polymer and a multifunctional responsive fluorocarbon surfactant, are added, they rapidly occupy the oil-water interface due to their excellent interfacial activity. The dendritic polymer forms a dense adsorption layer at the interface through its rigid core-shell structure, while the fluorocarbon surfactant further enhances the interfacial adsorption efficiency due to its low surface energy. Together, they reduce the interfacial tension to an ultra-low level. Finally, the added zinc oxide nanoparticles are effectively dispersed and stabilized in the system by the surfactant molecules and polymer chains under high-speed homogeneous shear force. These nanoparticles not only enhance the thermal stability of the system but also play a micro-fluidic role in the rock pores, synergistically altering the rock wettability with the surfactant and stripping away crude oil, ultimately forming a highly efficient composite oil displacement system that integrates ultra-low interfacial tension, intelligent response, flow control, and good stability.

[0008] According to a preferred embodiment of the present invention, in step S1, the stirring time is 1-2 hours.

[0009] According to a preferred embodiment of the present invention, in step S2, the dispersion time using a high-speed homogenizer is 30-40 minutes.

[0010] According to a preferred embodiment of the present invention, the preparation method of the amphiphilic block dendritic silicon polymer includes: A1, adding aminopropyl heptamethyltrisiloxane and G1.0 polyamide-amine dendritic polymer to a four-necked flask, purging with nitrogen for protection, and heating to 78-82°C to react and obtain a dendritic siloxane intermediate; A2, cooling to 64-66°C, adding epichlorohydrin dropwise in the presence of triethylamine, and then heating to 80-85°C to carry out a quaternization cyclization reaction to obtain a quaternized siloxane intermediate; finally, adding polyethylene glycol monomethyl ether and stannous octoate, heating to 88-92°C to react, and then distilling under reduced pressure after the reaction is completed.

[0011] In this invention, the preparation mechanism of the amphiphilic block dendritic silicon polymer is based on stepwise molecular construction and functionalization modification. The process begins with a nucleophilic substitution or amidation reaction under heating between the primary amino group at the end of aminopropylheptamethyltrisiloxane and the carboxyl group or potential reaction site on the surface of the polyamide-amine dendritic polymer, forming an intermediate with a siloxane core and a dendritic polymer as the primary backbone. Subsequently, in the presence of the basic catalyst triethylamine, the amino group surrounding the dendritic backbone in this intermediate molecule undergoes ring-opening addition with the epoxy group of epichlorohydrin. This reaction first generates a linear structure with a chloropropyl chain and hydroxyl groups. Then, with increasing temperature, the chlorine atom, driven by heat, acts as a leaving group and undergoes intramolecular quaternization cyclization with another amino group within or between molecules, constructing a positively charged rigid quaternary ammonium salt structure. This transformation significantly enhances the molecule's water solubility and interfacial adsorption capacity. Finally, under the catalysis of the metal catalyst stannous octoate, the hydroxyl groups at the end of the pre-synthesized polyethylene glycol monomethyl ether undergo etherification or esterification grafting reactions with the residual epoxy or hydroxyl groups in the quaternization intermediate, successfully introducing flexible polyoxyethylene ether segments into the molecular periphery, ultimately forming an amphiphilic block dendritic polymer with a core-shell structure. Its unique topology enables it to form a high-strength film at the oil-water interface, significantly reducing interfacial tension.

[0012] According to a preferred embodiment of the present invention, the preparation steps of the aminopropyl heptamethyltrisiloxane include: adding 500g of heptamethyltrisiloxane and 0.5g of a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex as a catalyst to a 1000mL four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and nitrogen inlet tube; heating to 85°C under nitrogen protection; then slowly adding 125g of allylamine dropwise through a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction temperature at 85°C; continuing the reaction at this temperature for 8 hours after the addition is complete; and monitoring the reaction at 2150cm² using Fourier transform infrared spectroscopy. -1 The reaction endpoint was determined when the characteristic Si-H absorption peaks at the point completely disappeared. After the reaction was completed, the reaction mixture was cooled to 25°C and transferred to a distillation apparatus for vacuum fractionation. The fraction at 125-130°C / 10 mmHg was collected to obtain colorless and transparent aminopropylheptamethyltrisiloxane.

[0013] According to a preferred embodiment of the present invention, in step A1, the reaction time is 12-14 hours after the temperature is raised to 78-82°C.

[0014] According to a preferred embodiment of the present invention, in step A2, the reaction time is 24-30 hours after heating to 88-92°C.

[0015] According to a preferred embodiment of the present invention, the preparation method of the multifunctional responsive fluorocarbon surfactant includes: B1, adding perfluorohexyl ethanol and isophorone diisocyanate to a dry four-necked flask, purging with nitrogen for protection, and heating to 68-72°C to react and obtain a fluorinated urethane intermediate; B2, then cooling to 58-62°C, adding N-aminoethylpiperazine to react and obtain a piperazine-functionalized fluorocarbon compound; finally, adding terminal epoxy polypropylene oxide-ethylene oxide block copolymer and triphenylphosphine, heating to 84-86°C to react, cooling to room temperature, adding dimethyl sulfate to carry out a quaternization reaction, washing with water, and distilling under reduced pressure.

[0016] In this invention, the key to the preparation reaction mechanism of the multifunctional responsive fluorocarbon surfactant lies in the sequential introduction of a fluorocarbon chain, a responsive group, and a hydrophilic segment. First, the terminal hydroxyl group of perfluorohexyl ethanol undergoes nucleophilic addition with a highly reactive isocyanate group in the isophorone diisocyanate molecule under heating conditions, forming a carbamate bond to obtain a monoisocyanate-terminated fluorinated urethane intermediate. Subsequently, this intermediate reacts with an excess of the bifunctional reagent aminoethylpiperazine, where the primary amine in the intermediate selectively attacks the remaining isocyanate group, generating a fluorocarbon compound bridged by a piperazine ring and terminated with a secondary amine. This piperazine ring provides a site for subsequent quaternization and endows the molecule with potential acid-base responsive properties. Finally, under the catalysis of triphenylphosphine, the epoxy groups of the terminal epoxy polypropylene oxide and ethylene oxide block copolymer undergo a ring-opening reaction with the above-mentioned secondary amine to form stable carbon-nitrogen bonds, grafting the temperature-sensitive polyether long chain onto the fluorocarbon chain; subsequently, the tertiary amine is quaternized using dimethyl sulfate, ultimately yielding an amphiphilic molecule with a fluorocarbon hydrophobic tail, a polyether hydrophilic head, and an intermediate piperazine quaternary ammonium salt structure. Its unique molecular structure enables it to intelligently adjust its interfacial behavior in response to changes in carbon dioxide and temperature.

[0017] According to a preferred embodiment of the present invention, the preparation steps of the end-epoxy polypropylene oxide-ethylene oxide block copolymer include: using 10.0 g of propylene glycol as an initiator, adding it to a 2L high-pressure reactor that has been dried at 150°C and is equipped with a mechanical stirrer, thermometer, nitrogen inlet pipe, and monomer feeding system; purging the reactor with high-purity nitrogen three times to replace the air in the reactor; raising the temperature to 115°C under continuous nitrogen protection and turning on the vacuum system to reduce the system pressure to -0.095 MPa, maintaining this condition for dehydration treatment for 30 min; then rapidly adding 1.5 g of precisely weighed potassium hydroxide catalyst through a dedicated feeding port, maintaining the reaction system temperature at 115°C, and continuously adding 500 g of propylene oxide dropwise at a rate of 150 g / h using a precision metering pump; during this process, precisely controlling the reaction pressure to 0.3 MPa through a back pressure valve; judging the reaction endpoint by monitoring the pressure gauge reading of the reactor; when the pressure continuously decreases from the highest point and finally stabilizes at a constant value, it indicates that the propylene oxide has been consumed; subsequently, precisely raising the system temperature to 120°C, and similarly... 300g of ethylene oxide was continuously added dropwise at a rate of 120g / h using a precision metering pump, while the reaction pressure was controlled at 0.3MPa for ethoxylation. The reaction continued until the pressure gauge reading remained stable, indicating that the reaction had reached its endpoint, yielding a hydroxyl-terminated block copolymer intermediate. Finally, end-group epoxy functionalization was performed by adding 200g of epichlorohydrin as a cyclizing agent to the reaction system via a feeding system. Simultaneously, 20g of a 30% sodium hydroxide solution was added to provide an alkaline environment. The reaction was carried out at a constant temperature of 70℃ at a speed of 300r / m. The reaction was carried out at a stirring speed of 1000 rpm for 6 hours. After the reaction was completed, the reactants were cooled to 25°C using a circulating water cooling system. Then, the unreacted epichlorohydrin was recovered by vacuum distillation at 85°C and -0.098 MPa. The remaining product was transferred to a separatory funnel and washed three times with 60°C warm deionized water until the aqueous phase was neutral. Finally, the product was dehydrated under vacuum at 90°C and -0.095 MPa for 2 hours to obtain a clear and transparent end-epoxy polypropylene oxide-ethylene oxide block copolymer final product.

[0018] According to a preferred embodiment of the present invention, in step B1, the reaction time is 6-8 hours after the temperature is raised to 68-72°C.

[0019] According to a preferred embodiment of the present invention, in step B2, the reaction time is 6-8 hours after the temperature is raised to 84-86°C.

[0020] The present invention also provides a method for preparing a surfactant for oilfield enhanced oil recovery, comprising the following raw materials in parts by weight: 10-25 parts by weight of amphiphilic block dendritic silicone polymer; 5-15 parts by weight of multifunctional responsive fluorocarbon surfactant; 5-10 parts by weight of rhamnolipid; 3-8 parts by weight of dodecyl dimethylamine oxide; 0.5-2 parts by weight of zinc oxide nanoparticles; 0.1-0.5 parts by weight of xanthan gum; 1-3 parts by weight of sodium chloride; and 40-80 parts by weight of deionized water.

[0021] The beneficial effects of this invention are as follows: The surfactant and its preparation method for oilfield enhanced oil recovery provided by this invention exhibit significantly superior technical effects compared to traditional surfactant systems in many aspects through unique molecular structure design and innovative compounding process. Its core technological advantages are primarily reflected in its excellent interfacial performance and stability. By combining a dendritic polymer with a precise three-dimensional structure with highly flexible organosilicon segments, the amphiphilic block dendritic silicone polymer can form a high-strength, high-density oriented film at the oil-water interface. This unique topology enables it to reduce the interfacial tension between oil and water to an ultra-low range, effectively overcoming the capillary force binding residual oil. Simultaneously, the multifunctional responsive fluorocarbon surfactant, with its inherently extremely low surface energy of the fluorocarbon segments, further enhances the interfacial activity of the system. More importantly, this composite system exhibits remarkable stability in harsh oil reservoir environments with high temperature and high salinity. Its organosilicon framework and stable chemical bonding structure can resist molecular chain breakage and performance degradation caused by high temperature. The specific molecular design gives it a high tolerance for multivalent cations in formation water, effectively avoiding salting out and precipitation, and ensuring the durability and stability of performance during long-term displacement.

[0022] Another outstanding technical effect of this invention lies in its intelligent response characteristics and multi-mechanism synergistic oil displacement capability. The design of the multifunctional responsive fluorocarbon surfactant introduces environmentally responsive groups, enabling it to sense and respond to changes in carbon dioxide concentration and temperature in the reservoir environment, achieving intelligent interfacial behavior regulation. During the injection and migration phases, the molecule remains relatively inert, minimizing ineffective adsorption on the rock surface; upon reaching the target reservoir area, under specific carbon dioxide partial pressure and temperature triggering, its molecular conformation and hydrophilic-hydrophobic balance change, and its surface activity is fully activated, thereby achieving "precise energy release" and "targeted oil displacement." This intelligent response mechanism perfectly complements the functions of other components in the system: the amphiphilic block dendritic silica polymer is mainly responsible for achieving ultra-low interfacial tension and effectively reversing rock wettability, transforming it from an oleophilic state to a hydrophilic state; zinc oxide nanoparticles and xanthan gum regulate the rheological properties of the system at the micro and macro scales, respectively, improving the mobility ratio and expanding the swept volume; while the biosurfactant rhamnolipid not only enhances the emulsifying ability of the system but also improves its environmental friendliness. This synergistic effect of multiple mechanisms and components constitutes a three-dimensional and efficient oil displacement network, which can address the challenge of residual oil mobilization in pores of different scales in complex reservoirs.

[0023] Furthermore, this invention also offers significant advantages in reducing adsorption losses and improving economic and environmental benefits. The high adsorption capacity of traditional surfactants on rock mineral surfaces, especially clay minerals, is a major reason for their high cost and reduced oil displacement efficiency. The two core modified compounds in this invention, through their specific molecular structures and charge distributions, can significantly reduce static and dynamic adsorption on rock surfaces. The steric hindrance effect of the dendritic structure, the charge shielding effect of the quaternary ammonium groups, and the low surface energy characteristics of the fluorocarbon segments collectively weaken the adhesion of molecules to the rock surface. This not only improves reagent utilization and reduces the feed cost per well chemical flooding, but also ensures the effective surfactant concentration at the displacement front, resulting in a more uniform and thorough oil displacement effect. From a life-cycle assessment, some components of this surfactant system exhibit good biodegradability, reducing the potential pollution risk to the producing formation and surrounding environment, aligning with the concept of green oil and gas field development. Simultaneously, the preparation process is clear, the reaction conditions are mild, and most of the raw materials used are commonly used industrial chemicals, avoiding the use of expensive or scarce raw materials. This lays a solid foundation for large-scale industrial production, demonstrating broad application prospects and significant comprehensive benefits. Detailed Implementation

[0024] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0025] The following is information on domestic suppliers of key related equipment and materials: The xanthan gum was purchased from Zibo Zhongxuan Biotechnology Co., Ltd.

[0026] The rhamnose glycolipid was purchased from Wuhan Yuancheng Gongchuang Technology Co., Ltd.

[0027] The dodecyl dimethylamine oxide was purchased from Zhangjiagang Hanbadu Chemical Co., Ltd.

[0028] The zinc oxide nanoparticles were purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0029] The G1.0 polyamide-amine dendritic polymer was purchased from Shanghai Yihui Biochemical Technology Co., Ltd.

[0030] The triethylamine was purchased from Hangzhou Xinruijia Biotechnology Co., Ltd.

[0031] The epichlorohydrin was purchased from Binhua Group Co., Ltd.

[0032] The polyethylene glycol monomethyl ether was purchased from Hubei Rishengchang New Material Technology Co., Ltd.

[0033] The stannous octanoate was purchased from Beijing Innocare Technology Co., Ltd.

[0034] The perfluorohexylethanol was purchased from Harbin Xuejia Fluorosilicon Chemical Co., Ltd.

[0035] The isophorone diisocyanate was purchased from Shanghai Jinjinle Industrial Co., Ltd.

[0036] The N-aminoethylpiperazine was purchased from Sichuan Kulinan Technology Co., Ltd.

[0037] The triphenylphosphine was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0038] The dimethyl sulfate was purchased from Tianjin Kemio Chemical Reagent Co., Ltd.

[0039] The heptamethyltrisiloxane was purchased from Shanghai Aoji Chemical Co., Ltd.

[0040] The 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex was purchased from Hubei Changfu Chemical Co., Ltd.

[0041] The allylamine was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0042] Preparation Example 1 This preparation example provides a method for preparing aminopropylheptamethyltrisiloxane. The steps include: adding 500g of heptamethyltrisiloxane and 0.5g of a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex as a catalyst to a 1000mL four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and nitrogen inlet tube; heating to 85℃ under nitrogen protection; then slowly adding 125g of allylamine dropwise through a constant-pressure dropping funnel, controlling the dropping rate to maintain the reaction temperature at 85℃; continuing the reaction at this temperature for 8 hours after the addition is complete; and monitoring the reaction at 2150cm² using Fourier transform infrared spectroscopy. -1 The reaction endpoint was determined when the characteristic Si-H absorption peaks at the point completely disappeared. After the reaction was completed, the reaction mixture was cooled to 25°C and transferred to a distillation apparatus for vacuum fractionation. The fraction at 125-130°C / 10 mmHg was collected to obtain colorless and transparent aminopropylheptamethyltrisiloxane.

[0043] Preparation Example 2 This preparation example provides a method for preparing an epoxy-terminated propylene oxide-ethylene oxide block copolymer. The steps include: using 10.0 g of propylene glycol as an initiator, adding it to a 2L high-pressure reactor that has been dried at 150°C and is equipped with a mechanical stirrer, thermometer, nitrogen inlet pipe, and monomer feeding system; purging the reactor with high-purity nitrogen three times to replace the air in the reactor; raising the temperature to 115°C under continuous nitrogen protection and turning on the vacuum system to reduce the system pressure to -0.095 MPa, maintaining this condition for dehydration treatment for 30 min; then rapidly adding 1.5 g of precisely weighed potassium hydroxide catalyst through a dedicated feeding port, maintaining the reaction system temperature at 115°C, and continuously adding 500 g of propylene oxide dropwise at a rate of 150 g / h using a precision metering pump. During this process, the reaction pressure is precisely controlled at 0.3 MPa using a back pressure valve. The reaction endpoint is determined by monitoring the pressure gauge reading of the reactor. When the pressure continuously decreases from the highest point and finally stabilizes at a constant value, it indicates that the propylene oxide has been consumed. Subsequently, the system temperature is precisely raised to 120°C, and the reaction is again controlled by a precision metering pump. 300g of ethylene oxide was continuously added dropwise at a rate of 120g / h using a metering pump, while the reaction pressure was controlled at 0.3MPa for ethoxylation. The reaction continued until the pressure gauge reading remained stable, indicating that the reaction had reached its endpoint, yielding a hydroxyl-terminated block copolymer intermediate. Finally, end-group epoxy functionalization was performed by adding 200g of epichlorohydrin as a cyclizing agent to the reaction system via a feeding system. Simultaneously, 20g of a 30% sodium hydroxide solution was added to provide an alkaline environment. The reaction was carried out at a constant temperature of 70℃ at a rate of 300r / min. The reaction was carried out at a stirring speed of n for 6 hours. After the reaction was completed, the reactants were cooled to 25°C using a circulating water cooling system. Then, the unreacted epichlorohydrin was recovered by vacuum distillation at 85°C and -0.098 MPa. The remaining product was transferred to a separatory funnel and washed three times with 60°C warm deionized water until the aqueous phase was neutral. Finally, the product was dehydrated under vacuum at 90°C and -0.095 MPa for 2 hours to obtain a clear and transparent end-epoxy polypropylene oxide-ethylene oxide block copolymer final product. Example

[0044] Preparation of amphiphilic block dendritic silicone polymer: In a four-necked flask, 50 g of aminopropylheptamethyltrisiloxane and 45 g of G1.0 polyamide-amine dendritic polymer were added. Nitrogen gas was introduced for protection, and the mixture was heated to 80 °C and reacted for 13 h to obtain a dendritic siloxane intermediate. The temperature was then lowered to 65 °C, and 1 g of triethylamine catalyst was added, followed by dropwise addition of 28 g of epichlorohydrin. After the addition was complete, the temperature was raised to 83 °C for a quaternization cyclization reaction for 8 h to obtain a quaternized siloxane intermediate. Finally, 120 g of polyethylene glycol monomethyl ether and 0.5 g of stannous octoate were added, and the mixture was heated to 90 °C and reacted for 28 h. After the reaction, volatile components were removed by vacuum distillation to obtain a pale yellow viscous liquid product.

[0045] Preparation of a multifunctional responsive fluorocarbon surfactant: 62 g of perfluorohexyl ethanol and 44 g of isophorone diisocyanate were added to a dry four-necked flask. Under nitrogen protection, the mixture was heated to 70 °C and reacted for 7 h to obtain a fluorinated urethane intermediate. The temperature was then lowered to 60 °C, and 26 g of N-aminoethylpiperazine was added. The reaction was continued for 12 h to obtain a piperazine-functionalized fluorocarbon compound. Finally, 240 g of terminal epoxy-polypropylene oxide-ethylene oxide block copolymer and 0.8 g of triphenylphosphine were added. The mixture was heated to 85 °C and reacted for 7 h. After cooling to 25 °C, 25 g of dimethyl sulfate was added for a quaternization reaction for 8 h. Byproducts were removed by washing with water, and the product was obtained by vacuum distillation, yielding a light brown viscous liquid product.

[0046] Preparation of surfactants for oilfield enhanced oil recovery: 700g of deionized water was heated to 50℃, and 0.3g of xanthan gum was added with stirring until completely dissolved, forming a colloidal solution. The colloidal solution was then heated to 60℃, and 8g of rhamnolipid, 5g of dodecyl dimethylamine oxide, and 2g of sodium chloride were added sequentially, with stirring continuing for 1.5h. Then, 20g of the previously prepared amphiphilic block dendritic silica polymer and 12g of a multifunctional responsive fluorocarbon surfactant were added, and after thorough mixing, 1g of zinc oxide nanoparticles were added. The mixture was dispersed using a high-speed homogenizer at 8000 r / min for 35min to obtain the final product. Example

[0047] The preparation method is the same as in Example 1, except for the preparation of the amphiphilic block dendritic silicone polymer: In a four-necked flask, 48 g of aminopropylheptamethyltrisiloxane and 43 g of G1.0 polyamide amine dendritic polymer were added, and the mixture was protected with nitrogen gas and heated to 79°C for 12 h to obtain a dendritic siloxane intermediate. Then, the temperature was lowered to 64°C, and 0.9 g of triethylamine catalyst was added, followed by the dropwise addition of 26 g of epichlorohydrin. After the addition was complete, the temperature was raised to 81°C for a quaternization cyclization reaction for 7 h to obtain a quaternized siloxane intermediate. Finally, 115 g of polyethylene glycol monomethyl ether and 0.4 g of stannous octoate were added, and the mixture was heated to 89°C for 24 h. After the reaction, volatile components were removed by vacuum distillation to obtain the product.

[0048] Preparation of a multifunctional responsive fluorocarbon surfactant: 60 g of perfluorohexyl ethanol and 42 g of isophorone diisocyanate were added to a dry four-necked flask. Under nitrogen protection, the mixture was heated to 69 °C and reacted for 6 h to obtain a fluorinated urethane intermediate. The temperature was then lowered to 59 °C, and 24 g of N-aminoethyl piperazine was added. The reaction was continued for 11 h to obtain a piperazine-functionalized fluorocarbon compound. Finally, 230 g of terminal epoxy-polypropylene oxide-ethylene oxide block copolymer and 0.7 g of triphenylphosphine were added. The mixture was heated to 84 °C and reacted for 6 h. After cooling to 24 °C, 23 g of dimethyl sulfate was added to initiate a quaternization reaction for 7 h. Byproducts were removed by washing with water, and the product was obtained by vacuum distillation.

[0049] Preparation of surfactants for oilfield enhanced oil recovery: 750g of deionized water was heated to 49℃, and 0.2g of xanthan gum was added while stirring until completely dissolved to form a colloidal solution. The colloidal solution was then heated to 59℃, and 6g of rhamnolipid, 4g of dodecyl dimethylamine oxide, and 1.5g of sodium chloride were added sequentially, with stirring continuing for 1 hour. Then, 15g of the previously prepared amphiphilic block dendritic silica polymer and 8g of a multifunctional responsive fluorocarbon surfactant were added, and after thorough mixing, 0.6g of zinc oxide nanoparticles were added. The mixture was dispersed using a high-speed homogenizer at 7500 r / min for 30 minutes to obtain the final product. Example

[0050] The preparation method is the same as in Example 1, except for the preparation of the amphiphilic block dendritic silicone polymer: In a four-necked flask, 52 g of aminopropylheptamethyltrisiloxane and 47 g of G1.0 polyamide amine dendritic polymer were added, and the mixture was protected with nitrogen gas and heated to 81°C for 14 h to obtain a dendritic siloxane intermediate. Then, the temperature was lowered to 66°C, and 1.1 g of triethylamine catalyst was added, followed by the dropwise addition of 30 g of epichlorohydrin. After the addition was complete, the temperature was raised to 84°C for a quaternization cyclization reaction for 9 h to obtain a quaternized siloxane intermediate. Finally, 125 g of polyethylene glycol monomethyl ether and 0.6 g of stannous octoate were added, and the mixture was heated to 91°C for 30 h. After the reaction, volatile components were removed by vacuum distillation to obtain the product.

[0051] Preparation of a multifunctional responsive fluorocarbon surfactant: 64 g of perfluorohexyl ethanol and 46 g of isophorone diisocyanate were added to a dry four-necked flask. Under nitrogen protection, the mixture was heated to 71 °C and reacted for 8 h to obtain a fluorinated urethane intermediate. The temperature was then lowered to 61 °C, and 28 g of N-aminoethylpiperazine was added. The reaction was continued for 13 h to obtain a piperazine-functionalized fluorocarbon compound. Finally, 250 g of terminal epoxy-polypropylene oxide-ethylene oxide block copolymer and 0.9 g of triphenylphosphine were added. The mixture was heated to 86 °C and reacted for 8 h. After cooling to 26 °C, 27 g of dimethyl sulfate was added to initiate a quaternization reaction for 9 h. Byproducts were removed by washing with water, and the product was obtained by vacuum distillation.

[0052] Preparation of surfactants for oilfield enhanced oil recovery: 650g of deionized water was heated to 51℃, and 0.4g of xanthan gum was added with stirring until completely dissolved, forming a colloidal solution. The colloidal solution was then heated to 61℃, and 9g of rhamnolipid, 6g of dodecyl dimethylamine oxide, and 2.5g of sodium chloride were added sequentially, with stirring continuing for 2 hours. Then, 24g of the previously prepared amphiphilic block dendritic silica polymer and 14g of a multifunctional responsive fluorocarbon surfactant were added, and after thorough mixing, 1.5g of zinc oxide nanoparticles were added. The mixture was dispersed using a high-speed homogenizer at 8500 r / min for 40 minutes to obtain the final product.

[0053] Comparative Example 1 The preparation method is the same as in Example 1, except that this comparative example does not contain the amphiphilic block dendritic silicone polymer and the multifunctional responsive fluorocarbon surfactant. 800g of deionized water was heated to 50°C, and 0.3g of xanthan gum was added while stirring until completely dissolved, forming a colloidal solution. The colloidal solution was then heated to 60°C, and 8g of rhamnolipid, 5g of dodecyl dimethylamine oxide, and 2g of sodium chloride were added sequentially, with stirring continuing for 1.5h. Then, 1g of zinc oxide nanoparticles were added, and the mixture was dispersed using a high-speed homogenizer at 8000 r / min for 35min to obtain the product.

[0054] Comparative Example 2 The preparation method is the same as in Example 1, except that this comparative example contains only amphiphilic block dendritic silica polymer and does not contain multifunctional responsive fluorocarbon surfactant. The preparation method of the amphiphilic block dendritic silica polymer is the same as in Example 1. Preparation of surfactant for oilfield enhanced oil recovery: 712g of deionized water was heated to 50°C, and 0.3g of xanthan gum was added while stirring until completely dissolved to form a colloidal solution. The colloidal solution was then heated to 60°C, and 8g of rhamnolipid, 5g of dodecyl dimethylamine oxide, and 2g of sodium chloride were added sequentially, and stirring was continued for 1.5h. Then, 20g of the aforementioned prepared amphiphilic block dendritic silica polymer was added, and after stirring and mixing evenly, 1g of zinc oxide nanoparticles were added. The mixture was dispersed using a high-speed homogenizer at a speed of 8000 r / min for 35min to obtain the product.

[0055] Comparative Example 3 The preparation method is the same as in Example 1, except that sodium dodecylbenzenesulfonate is used instead of the two modified compounds in this comparative example. 700g of deionized water was heated to 50°C, and 0.3g of xanthan gum was added while stirring until completely dissolved, forming a colloidal solution. The colloidal solution was then heated to 60°C, and 8g of rhamnolipid, 5g of dodecyl dimethylamine oxide, 2g of sodium chloride, and 32g of sodium dodecylbenzenesulfonate were added sequentially, with stirring continued for 1.5 hours. Then, 1g of zinc oxide nanoparticles were added, and the mixture was dispersed using a high-speed homogenizer at 8000 r / min for 35 minutes to obtain the product.

[0056] Performance testing and results analysis According to existing national and industry standards, the performance of the surfactants prepared in Examples 1-3 and Comparative Examples 1-3 for oilfield enhanced oil recovery was tested using the following methods: The surfactant products prepared in Examples 1-3 and Comparative Examples 1-3 were tested under simulated oilfield formation water conditions. The test conditions were: temperature 90℃, salinity 150,000 mg / L, and total calcium and magnesium ion concentration 5,000 mg / L. Interfacial tension was tested using a TX-500C spin-drop interfacial tension meter. The surfactant was prepared into a 0.3% mass fraction solution, and the dynamic interfacial tension was measured with simulated crude oil at a constant temperature of 90℃. The equilibrium interfacial tension value was recorded after 120 minutes. Emulsification performance was tested by mixing the surfactant solution with simulated crude oil at a volume ratio of 1:1, stirring at 3000 r / min for 10 minutes in a 90℃ constant temperature water bath, and then allowing it to stand. The time required for 50% aqueous phase to separate from the emulsion was recorded. Thermal stability testing involved placing the surfactant solution in a 90℃ constant-temperature oven, periodically sampling to determine its interfacial activity and emulsifying properties, and continuously observing for 30 days. Adsorption loss testing employed a static adsorption method, mixing the surfactant solution with oil sands at a mass ratio of 10:1, shaking at 90℃ for 24 hours, and calculating the adsorption amount by measuring the change in solution concentration before and after adsorption. Core displacement experiments used standard Bailey sand cores, 30 cm in length, 2.5 cm in diameter, with a porosity of 18-22% and a permeability of 150-200 mD. Water flooding was first performed at 90℃ to a water cut of 98%, followed by surfactant flooding, injecting 0.3 times the pore volume of surfactant solution, and then water flooding was repeated to a water cut of 98%. The increase in oil recovery was calculated.

[0057] Table 1: Performance test results of each embodiment and comparative example

[0058] As shown in Table 1, the surfactants prepared in Examples 1-3 exhibit excellent overall performance under high temperature and high salt conditions. Example 1 showed the best results, with an interfacial tension of 3.2 × 10⁻⁶. -4 With an ultra-low mN / m level, emulsification stability reached 48.5 hours, and interfacial activity remained good after 30 days of thermal aging, with an adsorption loss of only 0.25 mg / g sand. Core displacement experiments increased oil recovery by 18.7%. In contrast, Comparative Example 1, lacking two key modifying compounds, showed a significant decline in various properties; Comparative Example 2, containing only amphiphilic block dendritic silica polymer, performed better than Comparative Example 1 but worse than the Example; Comparative Example 3, using the traditional surfactant sodium dodecylbenzenesulfonate, showed significantly inferior performance compared to the Example. This fully demonstrates the key contribution of the synergistic effect of amphiphilic block dendritic silica polymer and multifunctional responsive fluorocarbon surfactant to improving product performance.

[0059] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a surfactant for enhancing oil recovery in oilfields, characterized in that the steps include... include: S1. Heat deionized water to 48-52℃, add xanthan gum while stirring, and continue stirring until completely dissolved to form a colloidal solution; The colloidal solution was then heated to 58-62°C, and rhamnolipid, dodecyl dimethylamine oxide, and sodium chloride were added sequentially, while stirring continued. S2. Then add the amphiphilic block dendritic silicone polymer and the multifunctional responsive fluorocarbon surfactant, stir and mix, then add zinc oxide nanoparticles and disperse using a high-speed homogenizer.

2. The method for preparing a surfactant for enhancing oil recovery in oilfields according to claim 1, characterized in that, In step S1, the stirring time continues for 1-2 hours.

3. The method for preparing a surfactant for oilfield enhanced oil recovery according to claim 1, characterized in that, In step S2, the dispersion time using a high-speed homogenizer is 30-40 minutes.

4. The method for preparing a surfactant for enhancing oil recovery in oilfields according to claim 1, characterized in that, The preparation method of the amphiphilic block dendritic silicon polymer includes: A1, adding aminopropyl heptamethyltrisiloxane and G1.0 polyamide-amine dendritic polymer to a four-necked flask, purging with nitrogen for protection, and heating to 78-82℃ to react and obtain a dendritic siloxane intermediate; A2, cooling to 64-66℃, adding epichlorohydrin dropwise in the presence of triethylamine, and then heating to 80-85℃ to carry out a quaternization cyclization reaction to obtain a quaternized siloxane intermediate; finally, adding polyethylene glycol monomethyl ether and stannous octoate, heating to 88-92℃ to react, and distilling under reduced pressure after the reaction is completed.

5. The method for preparing a surfactant for enhancing oil recovery in oilfields according to claim 4, characterized in that, In step A1, the temperature is raised to 78-82℃ and the reaction time is 12-14 hours.

6. The method for preparing a surfactant for oilfield enhanced oil recovery according to claim 4, characterized in that, In step A2, the temperature is raised to 88-92℃ and the reaction time is 24-30 hours.

7. The method for preparing a surfactant for enhancing oil recovery in oilfields according to claim 1, characterized in that, The preparation method of the multifunctional responsive fluorocarbon surfactant includes: B1, adding perfluorohexyl ethanol and isophorone diisocyanate to a dry four-necked flask, purging with nitrogen for protection, and heating to 68-72℃ to react and obtain a fluorinated urethane intermediate; B2, then cooling to 58-62℃, adding N-aminoethylpiperazine to react and obtain a piperazine-functionalized fluorocarbon compound; finally, adding terminal epoxy polypropylene oxide-ethylene oxide block copolymer and triphenylphosphine, heating to 84-86℃ to react, cooling to room temperature, adding dimethyl sulfate to carry out a quaternization reaction, washing with water, and distilling under reduced pressure.

8. The method for preparing a surfactant for enhancing oil recovery in oilfields according to claim 7, characterized in that, In step B1, the temperature is raised to 68-72℃ and the reaction time is 6-8 hours.

9. The method for preparing a surfactant for oilfield enhanced oil recovery according to claim 7, characterized in that, In step B2, the temperature is raised to 84-86℃ and the reaction time is 6-8 hours.

10. A surfactant for oilfield enhanced oil recovery prepared by the method according to any one of claims 1-9, characterized in that, The raw materials include the following parts by weight: 10-25 parts by weight of amphiphilic block dendritic silicone polymer; Multifunctional responsive fluorocarbon surfactant (5-15 parts by weight); rhamnolipid (5-10 parts by weight); Dodecyl dimethylamine oxide 3-8 parts by weight; zinc oxide nanoparticles 0.5-2 parts by weight; xanthan gum 0.1-0.5 parts by weight; sodium chloride 1-3 parts by weight; deionized water 40-80 parts by weight.

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