A multi-block polyether E-surfactant for oil displacement, its preparation method, and its application.

Abstract

This invention belongs to the field of oilfield chemical enhanced oil recovery (DEOR), and relates to a multi-block polyether-type E-surfactant for DEOR, its preparation method, and its application. The preparation steps are as follows: fatty alcohol, KOH catalyst, and 18-crown ether-6 are sequentially added to a batch reactor, and a triblock AP is obtained through propoxylation or through a combination of propoxylation and ethoxylation. m E n P p or quadblock AP m E n P p E e Any one of the polyether blocks in the formulation is used; under urea catalysis, the obtained polyether block is reacted with aminosulfonic acid to prepare a fatty alcohol polyether ammonium sulfate intermediate; neutralized with NaOH aqueous solution to obtain crude fatty alcohol polyether sodium sulfate, which is then filtered and purified by rotary evaporation to obtain a multi-block polyether type E-surfactant for oil displacement. This surfactant has advantages such as high surface activity, ultra-low interfacial tension, excellent emulsification, low adsorption loss, and good electrolyte resistance, showing good application prospects in tertiary oil recovery.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical flooding technology, specifically to a multi-block polyether-type E-surfactant for oil displacement, its preparation method, and its application. Background Technology

[0002] As oilfield development progresses to later stages, many older oilfields are entering high and ultra-high water-cut phases. Under these circumstances, the oil recovery effects of primary and secondary recovery technologies diminish, making the efficient exploitation of remaining oil reservoirs a critical challenge for the petroleum industry. Currently, tertiary oil recovery (EOR) technology, with its significant advantages, has become a core technology for ensuring long-term stable production in older oilfields.

[0003] With the continuous development of tertiary oil recovery technology, a multi-technology system including polymer flooding, surfactant flooding, and alkaline flooding has developed synergistically, constructing a technology matrix for the efficient development of complex reservoirs. Among them, surfactant flooding, with its unique mechanism and significant effects, occupies an irreplaceable strategic position in the field of tertiary oil recovery.

[0004] However, surfactant flooding still faces many challenges in practical applications. Traditional single surfactants are difficult to adapt to extreme reservoir environments such as high temperature and high salinity, and their stability is insufficient. Although the use of multiple surfactants can improve performance, chromatographic separation phenomena are prone to occur, affecting the oil displacement effect. In order to improve crude oil recovery, surfactants are often combined with alkalis and polymers to form ternary composite flooding systems in actual production. However, although the addition of alkalis can reduce the oil-water interfacial tension, it can cause permanent damage to the rock formation, affecting the long-term development benefits of the reservoir.

[0005] Faced with these challenges, the development of new surfactants is urgently needed. There is a pressing need to develop surfactants with simple structures or similar polar structures that can generate ultra-low interfacial tension, significantly improving oil displacement efficiency, while also possessing excellent resistance to extreme environments, maintaining stable performance under harsh conditions such as high temperature and high salinity. This would provide strong support for the green and efficient development of tertiary oil recovery technology. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a multi-block polyether-type E-surfactant for oil displacement, its preparation method, and its applications. The multi-block polyether-type E-surfactant provided by this invention improves emulsification and wettability, generates ultra-low oil-water interfacial tension, thereby enhancing oil recovery. Furthermore, by adjusting the polyether blocks, it exhibits stronger environmental adaptability.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing a multi-block polyether type E-surfactant for oil displacement includes the following steps:

[0009] (1) Preparation of multi-block polyethers: fatty alcohol, catalyst KOH, and 18-crown ether-6 are sequentially added to a batch reactor, and tri-block AP is prepared by propoxylation reaction or by propoxylation and ethoxylation reaction. m E n P p or quadblock AP m E n P p E e Polyether blocks;

[0010] (2) Preparation of multi-block polyether type E-surfactant:

[0011] Under urea catalysis, the polyether block obtained in step (1) is reacted with aminosulfonic acid to prepare fatty alcohol polyether ammonium sulfate intermediate; NaOH aqueous solution is used for neutralization to obtain crude fatty alcohol polyether sodium sulfate, which is then filtered and evaporated to remove impurities to obtain fatty alcohol polyether sodium sulfate, thus obtaining a multi-block polyether type E-surfactant for oil displacement.

[0012] Furthermore, in step (1), the three-block AP m E n P p The preparation process is as follows:

[0013] Fatty alcohol, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130-145°C to carry out a propoxylation reaction to obtain a monoblock AP. m Ethylene oxide was added at 125℃-135℃ to carry out an ethoxylation reaction to obtain diblock AP. m E n ;

[0014] The mass of the added catalyst potassium hydroxide is 2‰-4‰ of the total mass of fatty alcohol and propylene oxide; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the molar ratio of the added propylene oxide to the fatty alcohol is (1.00-1.20)m:1.00.

[0015] The molar ratio of added ethylene oxide to fatty alcohol is (1.00-1.20)n:1.00.

[0016] Take two segments AP m E n Catalyst KOH and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130℃-145℃ to carry out a propoxylation reaction to obtain AP. m E n P p Polyether blocks;

[0017] The added catalyst, potassium hydroxide, has a mass of diblock AP. m E n The content of the added propylene oxide is 2‰-4‰ of the total mass; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the added propylene oxide and diblock AP m E n The molar ratio is (1.40-1.80)p:1.00.

[0018] Furthermore, in step (1), the four-block AP m E n P p E e The preparation process is as follows:

[0019] Fatty alcohol, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130-145°C to carry out a propoxylation reaction to obtain a monoblock AP. m Ethylene oxide was added at 125℃-135℃ to carry out an ethoxylation reaction to obtain diblock AP. m E n ;

[0020] The mass of the added catalyst potassium hydroxide is 2‰-4‰ of the total mass of fatty alcohol and propylene oxide; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the molar ratio of the added propylene oxide to the fatty alcohol is (1.00-1.20)m:1.00.

[0021] The molar ratio of added ethylene oxide to fatty alcohol is (1.00-1.20)n:1.00.

[0022] Take two segments AP m E n Catalyst KOH and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130℃-145℃ to carry out a propoxylation reaction to obtain triblock AP. m E n P p AP is obtained by adding ethylene oxide at 125℃-135℃ to carry out an ethoxylation reaction. m E n P p E e Polyether blocks;

[0023] The added catalyst, potassium hydroxide, has a mass of diblock AP. m E nThe content of the added propylene oxide is 2‰-4‰ of the total mass; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the added propylene oxide and diblock AP m E n The molar ratio is (1.40-1.80)p:1.00;

[0024] Adding ethylene oxide and diblock AP m E n The molar ratio is (1.00-1.30)e:1.00.

[0025] Further, step (2) includes:

[0026] Under urea catalysis, the polyether block obtained in step (1) is reacted with aminosulfonic acid at a molar ratio of 1:(1.15~3) at 100℃-120℃ for 2-4h to obtain fatty alcohol polyether ammonium sulfate intermediate; the reaction solution is neutralized with a NaOH aqueous solution with a concentration of 10-50wt% to pH=11-13 to obtain crude fatty alcohol polyether sodium sulfate, which is then filtered and evaporated at 40-60℃ to remove impurities to obtain fatty alcohol polyether sodium sulfate, thus obtaining a multi-block polyether type E-surfactant for oil displacement.

[0027] The fatty alcohol involved in the oil displacement multi-block polyether type E-surfactant prepared by this invention is a straight-chain saturated alcohol with 8-18 carbon atoms.

[0028] The polyether block of the oil displacement multi-block polyether type E-surfactant prepared by this invention is PO. m -EO n -PO p and PO m -EO n -PO p -EO e Where m takes values ​​from 3 to 30, n takes values ​​from 3 to 30, p takes values ​​from 2 to 20, and e takes values ​​from 2 to 20.

[0029] The multi-block polyether E-surfactant for oil displacement prepared by this invention can reduce the oil-water interfacial tension to ultra-low (10) -3 It can improve oil recovery rate (mN / m), and also improve emulsification and wettability, thereby improving oil recovery rate.

[0030] A multi-block polyether-type E-surfactant for oil displacement, wherein the multi-block polyether-type E-surfactant generates an ultra-low interfacial tension on the order of 10⁻³ mN / m to improve oil displacement efficiency.

[0031] The use of the multi-block polyether type E-surfactant for oil displacement in tertiary oil recovery.

[0032] The beneficial effects of this invention are:

[0033] (1) This invention provides a method for preparing a multi-block polyether type E-surfactant for oil displacement. The multi-block polyether type E-surfactant prepared by this method can generate an ultra-low interfacial tension on the order of 10-3 mN / m, which effectively reduces the retention force (such as capillary force) of oil droplets in rock pores, making it easier for oil droplets to be replaced by injected water, thereby improving the oil displacement efficiency.

[0034] (2) The present invention provides a multi-block polyether E-surfactant for oil displacement. The synergistic effect of PPO and PEO blocks in the surfactant gives it excellent emulsifying properties, which can reduce residual oil saturation and thus improve micro-displacement efficiency. The polyether blocks can be closely arranged at the interface. The insertion of PPO blocks is equivalent to increasing hydrophobicity, and the insertion of PEO blocks increases hydrophilicity, making it easier for water molecules and oil molecules to be inserted into the gaps between surfactant molecules, thereby increasing the thickness and viscosity of the interface, slowing down the flocculation rate between emulsion droplets, and prolonging the demulsification time.

[0035] (3) The present invention provides a multi-block polyether type E-surfactant for oil displacement. The surfactant has good wettability and can achieve wettability reversal, making it easier for oil droplets to detach from the rock and flow, thereby improving the oil recovery rate and showing good application prospects in tertiary oil recovery. Attached Figure Description

[0036] Figure 1 For C 12 Synthetic route of multi-block polyether E-surfactants, taking P9E3 and P6E2 as examples;

[0037] Figure 2 The polyether block C prepared in Examples 1 and 2 12 P9 proton nuclear magnetic resonance spectroscopy analysis;

[0038] Figure 3 The polyether block C prepared in Examples 1 and 2 12 P9E3 proton NMR spectrum analysis;

[0039] Figure 4 The polyether block C prepared in Example 1 12 P9E3P6 1H NMR spectrum analysis;

[0040] Figure 5 The polyether block C prepared in Example 2 12 P9E3P6E2 1H NMR spectrum analysis;

[0041] Figure 6 The polyether block C prepared in Examples 1 and 2 12 P9 and E-surfactant C 12 Fourier transform infrared spectroscopy analysis of P9S;

[0042] Figure 7 The polyether block C prepared in Examples 1 and 2 12 P9E3 and E-surfactant C 12 Fourier transform infrared spectroscopy analysis of P9E3S;

[0043] Figure 8 The polyether block C prepared in Example 1 12 P9E3P6 and E-surfactant C 12 Fourier transform infrared spectroscopy analysis of P9E3P6S;

[0044] Figure 9 The polyether block C prepared in Example 2 12 -P9E3P6E2 and E-surfactant C 12 Fourier transform infrared spectroscopy analysis of -P9E3P6E2S;

[0045] Figure 10 The oil-water interfacial tension of four multi-block polyether E-surfactants for oil displacement at different salt concentrations at 45℃;

[0046] Figure 11 The graph shows the emulsifying power of four multi-block polyether E-surfactants for oil displacement.

[0047] Figure 12 The graph shows the test results of the wettability of four multi-block polyether E-surfactants for oil displacement. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] A method for preparing a multi-block polyether type E-surfactant for oil displacement includes the following steps:

[0050] (1) Preparation of multi-block polyethers: fatty alcohol, catalyst KOH, and 18-crown ether-6 are added sequentially to a batch reactor, and tri-block AP is prepared by propoxylation reaction or by propoxylation and ethoxylation reaction. m E n Pp or quadblock AP m E n P p E e Any polyether block in the alcohol; specifically, the fatty alcohol is a straight-chain saturated alcohol with 8-18 carbon atoms.

[0051] (2) Preparation of multi-block polyether type E-surfactant:

[0052] Under urea catalysis, the polyether block obtained in step (1) is reacted with aminosulfonic acid to prepare fatty alcohol polyether ammonium sulfate intermediate; NaOH aqueous solution is used for neutralization to obtain crude fatty alcohol polyether sodium sulfate, which is then filtered and evaporated to remove impurities to obtain fatty alcohol polyether sodium sulfate, thus obtaining a multi-block polyether type E-surfactant for oil displacement.

[0053] Tri-segment AP m E n P p The preparation process is as follows:

[0054] Fatty alcohol, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130-145°C to carry out a propoxylation reaction to obtain a monoblock AP. m Ethylene oxide was added at 125℃-135℃ to carry out an ethoxylation reaction to obtain diblock AP. m E n ;

[0055] The mass of the added catalyst potassium hydroxide is 2‰-4‰ of the total mass of fatty alcohol and propylene oxide; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the molar ratio of the added propylene oxide to the fatty alcohol is (1.00-1.20)m:1.00.

[0056] The molar ratio of added ethylene oxide to fatty alcohol is (1.00-1.20)n:1.00.

[0057] Take two segments AP m E n Catalyst KOH and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130℃-145℃ to carry out a propoxylation reaction to obtain AP. m E n P p Polyether blocks;

[0058] The added catalyst, potassium hydroxide, has a mass of diblock AP. m E nThe content of the added propylene oxide is 2‰-4‰ of the total mass; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the added propylene oxide and diblock AP m E n The molar ratio is (1.40-1.80)p:1.00.

[0059] Quad-block AP m E n P p E e The preparation process is as follows:

[0060] Fatty alcohol, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130-145°C to carry out a propoxylation reaction to obtain a monoblock AP. m Ethylene oxide was added at 125℃-135℃ to carry out an ethoxylation reaction to obtain diblock AP. m E n ;

[0061] The mass of the added catalyst potassium hydroxide is 2‰-4‰ of the total mass of fatty alcohol and propylene oxide; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the molar ratio of the added propylene oxide to the fatty alcohol is (1.00-1.20)m:1.00.

[0062] The molar ratio of added ethylene oxide to fatty alcohol is (1.00-1.20)n:1.00.

[0063] Take two segments AP m E n Catalyst KOH and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130℃-145℃ to carry out a propoxylation reaction to obtain triblock AP. m E n P p AP is obtained by adding ethylene oxide at 125℃-135℃ to carry out an ethoxylation reaction. m E n P p E e Polyether blocks;

[0064] The added catalyst, potassium hydroxide, has a mass of diblock AP. m E n The content of the added propylene oxide is 2‰-4‰ of the total mass; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the added propylene oxide and diblock AP m E nThe molar ratio is (1.40-1.80)p:1.00;

[0065] Adding ethylene oxide and diblock AP m E n The molar ratio is (1.00-1.30)e:1.00.

[0066] Step (2) includes:

[0067] Under urea catalysis, the polyether block obtained in step (1) is mixed with aminosulfonic acid at a molar ratio of 1:(1.15~3). The mixture is stirred and heated to make it uniform. When the temperature reaches 50℃, aminosulfonic acid is added in small amounts several times. After stirring evenly, the temperature is raised to the reaction temperature of 100℃-120℃ and reacted for 2-4 hours to obtain fatty alcohol polyether ammonium sulfate intermediate. After the reaction is cooled to room temperature, it is dissolved in anhydrous ethanol. While passing nitrogen, the generated ammonia gas is neutralized with NaOH aqueous solution and absorbed by dilute hydrochloric acid solution. Specifically, the reaction solution is neutralized to pH=11-13 with NaOH aqueous solution with a concentration of 10-50wt% to obtain crude fatty alcohol polyether sodium sulfate. After filtration and rotary evaporation at 40-60℃ to remove impurities, fatty alcohol polyether sodium sulfate is obtained, which is the multi-block polyether type E-surfactant for oil displacement.

[0068] The amount of urea catalyst used is 1%-2% of the total mass of the reactants.

[0069] The following are specific examples:

[0070] Example 1: A method for preparing a multi-block polyether type E-surfactant for oil displacement, comprising the following steps:

[0071] (1) 1.0753 mol dodecanol was added to a batch reactor as an initiator, along with 0.0437 mol KOH and 0.0437 mol g 18-crown ether-6 as catalysts. At 135 °C, 10.6455 mol g propylene oxide was added to carry out a propoxylation reaction to obtain polyether block C. 12 P9 was then subjected to an ethoxylation reaction with 3.2259 mol of ethylene oxide added at 125 °C to obtain polyether block C. 12 P9E3, the structural formula is shown below:

[0072]

[0073] (2) Add 0.1786 mol of polyether block C to the batch reactor. 12 Using P9E3 as an initiator, 0.0130 mol KOH and 0.0130 mol 18-crown ether-6 were added as catalysts, and 1.6074 mol propylene oxide was added at 130 °C to carry out a propoxylation reaction, obtaining polyether block C. 12P9E3P6, the structural formula is shown below;

[0074]

[0075] (3) Add 0.0500 mol of polyether block C to a four-necked flask 12 P9E3P6 was reacted with 0.0123 mol of urea at 50°C, and then 0.1500 mol of aminosulfonic acid was added. The mixture was reacted at 120°C for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, neutralized with 30% NaOH aqueous solution, and the final product C was obtained by filtration and rotary evaporation to remove impurities. 12 P9E3P6S, Product C 12 The structural formula of P9E3P6S is shown below:

[0076]

[0077] Example 2: A method for preparing a multi-block polyether type E-surfactant for oil displacement, such as... Figure 1 As shown, it includes the following steps:

[0078] (1) 1.0753 mol dodecanol was added to a batch reactor as an initiator, along with 0.0437 mol KOH and 0.0437 mol g 18-crown ether-6 as catalysts. At 135 °C, 10.6455 mol g propylene oxide was added to carry out a propoxylation reaction to obtain polyether block C. 12 P9 was then subjected to an ethoxylation reaction with 3.2259 mol of ethylene oxide added at 125 °C to obtain polyether block C. 12 P9E 3, The structural formula is as follows:

[0079]

[0080] (2) Add 0.1786 mol of polyether block C to the batch reactor. 12 Using P9E3 as an initiator, 0.0130 mol KOH and 0.0130 mol 18-crown ether-6 were added as catalysts, and 1.6074 mol propylene oxide was added at 130 °C to carry out a propoxylation reaction, obtaining polyether block C. 12 P9E3P6 was then subjected to an ethoxylation reaction with 0.3572 mol of ethylene oxide at 125 °C to obtain polyether block C. 12 P9E3P6E2, the structural formula is shown below;

[0081]

[0082] (3) Add 0.0500 mol of polyblock copolymer to a four-necked flask. 12P9E3P6E2 was reacted with 0.0131 mol of urea at 50°C, and then 0.1500 mol of aminosulfonic acid was added. The mixture was reacted at 120°C for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, neutralized with 30% NaOH aqueous solution, and then filtered and purified by rotary evaporation to obtain the target product C. 12 P9E3P6E2S, Product C 12 The structural formula of P9E3P6E2S is shown below:

[0083]

[0084] Example 3: A method for preparing a multi-block polyether type E-surfactant for oil displacement, comprising the following steps:

[0085] (1) 1.0753 mol tetradecyl alcohol was added to a batch reactor as an initiator, along with 0.0423 mol KOH and 0.0423 mol g 18-crown ether-6 as catalysts. At 135 °C, 10.6455 mol g propylene oxide was added to carry out a propoxylation reaction to obtain polyether block C. 14 P9 was then subjected to an ethoxylation reaction with 3.2259 mol of ethylene oxide added at 125 °C to obtain polyether block C. 14 P9E 3, The structural formula is as follows:

[0086]

[0087] (2) Add 0.1786 mol of polyether block C to the batch reactor. 14 Using P9E3 as an initiator, 0.0133 mol KOH and 0.0133 mol 18-crown ether-6 were added as catalysts, and 1.6074 mol propylene oxide was added at 130 °C to carry out a propoxylation reaction, obtaining polyether block C. 14 P9E3P6, the structural formula is shown below;

[0088]

[0089] (3) Add 0.0500 mol of polyether block C to a four-necked flask 14 P9E3P6 was reacted with 0.0126 mol of urea at 50°C, and then 0.1500 mol of aminosulfonic acid was added. The mixture was reacted at 120°C for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, neutralized with 30% NaOH aqueous solution, and the final product C was obtained by filtration and rotary evaporation to remove impurities. 14 P9E3P6S, Product C 14 The structural formula of P9E3P6S is shown below:

[0090] Example 4: A method for preparing a multi-block polyether type E-surfactant for oil displacement, such as... Figure 1 As shown, it includes the following steps:

[0091] (1) 1.0753 mol tetradecyl alcohol was added to a batch reactor as an initiator, along with 0.0423 mol KOH and 0.0423 mol g 18-crown ether-6 as catalysts. At 135 °C, 10.6455 mol g propylene oxide was added to carry out a propoxylation reaction to obtain polyether block C. 14 P9 was then subjected to an ethoxylation reaction with 3.2259 mol of ethylene oxide added at 125 °C to obtain polyether block C. 14 P9E 3, The structural formula is as follows:

[0092]

[0093] (2) Add 0.1786 mol of polyether block C to the batch reactor. 14 Using P9E3 as an initiator, 0.0133 mol KOH and 0.0133 mol 18-crown ether-6 were added as catalysts, and 1.6074 mol propylene oxide was added at 130 °C to carry out a propoxylation reaction, obtaining polyether block C. 14 P9E3P6 was then subjected to an ethoxylation reaction with 0.3572 mol of ethylene oxide at 125 °C to obtain polyether block C. 14 P9E3P6E2, the structural formula is shown below;

[0094]

[0095] (3) Add 0.0500 mol of polyblock copolymer to a four-necked flask. 14 P9E3P6E2 was reacted with 0.0133 mol of urea at 50°C, and then 0.1500 mol of aminosulfonic acid was added. The mixture was reacted at 120°C for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, neutralized with 30% NaOH aqueous solution, and then filtered and rotary evaporated to remove impurities to obtain the target product C. 14 P9E3P6E2S, Product C 14 The structural formula of P9E3P6E2S is shown below:

[0096]

[0097] The four polyether blocks from Examples 1-2 were analyzed by 1H NMR and Fourier transform infrared spectroscopy. The two E-surfactants from Examples 1-2 were also analyzed by... 12 P9E3P6S, C 12 P9E3P6E2S and E-surfactant C 12P9S, C 12 Fourier transform infrared spectroscopy analysis using P9E3S confirmed that the obtained product was the target product, as shown in the attached diagram. Figures 2-9 As shown.

[0098] The two E-surfactants C obtained in Examples 1-2 12 P9E3P6S, C 12 P9E3P6E2S and E-surfactant C 12 P9S, C 12 P9E3S underwent interfacial tension testing, emulsifying power testing, and wettability testing; the specific test conditions were as follows:

[0099] Interfacial tension test: A series of surfactant aqueous solutions with different salt concentrations and surfactant concentrations of 0.1-1% were prepared. Under constant temperature conditions, the interfacial tension (IFT) between the surfactant and alkanes was measured using a rotating drop interfacial tension meter to evaluate its ability and stability to achieve ultra-low interfacial tension under different salt concentrations.

[0100] Emulsifying power test: Prepare a surfactant aqueous solution with a concentration of 0.1-1%. Add liquid paraffin and surfactant aqueous solution in equal volumes to a stoppered graduated cylinder, shake it vigorously to ensure complete emulsification, and record the time when 10 mL of aqueous phase is precipitated. This is used to characterize the emulsifying power EP(s) of the surfactant.

[0101] Wettability test: Prepare a surfactant aqueous solution with a concentration of 0.1-1%, and drop the test solution onto the solid paraffin film substrate in a vertical direction using a syringe. Measure the contact angle between the droplet and the paraffin film using a contact angle meter. Measure each sample three times and take the average value. The test temperature is 25℃ to evaluate its wettability on the hydrophobic film.

[0102] Interfacial tension test results: The interfacial tension of the four E-surfactants in the decane-salt water system all showed a trend of first decreasing and then increasing with increasing salt concentration. 12 The optimal salinity for P9S surfactant is 3% NaCl, with an IFT of 1.02 × 10⁻⁶. -4 mN / m; C 12 The optimal salinity for the P9E3S surfactant is 4% NaCl, with an IFT of 1.10 × 10⁻⁶. -5 mN / m; C 12 The optimal salinity for the P9E3P6S surfactant is 2% NaCl, with an IFT of 3.00 × 10⁻⁶. -5 mN / m; C 12 The optimal salinity for the P9E3P6E2S surfactant is 2% NaCl, with an IFT of 5.40 × 10⁻⁶. -5With mN / m, all four E-surfactants achieved ultra-low interfacial tension, and the increased PO block size helped reduce the salt concentration required to reach the minimum equilibrium interfacial tension. The interfacial tension test results are shown in the attached figure. Figure 10 As shown.

[0103] Emulsifying power test results: The emulsifying ability of the four E-surfactants on liquid paraffin showed an increasing trend with the increase of block size, indicating that multi-block E-surfactants have good oil solubility and are suitable as oil displacement surfactants. The emulsifying power test results are shown in the attached figure description. Figure 11 As shown.

[0104] Wettability test results: The contact angles of the four E-surfactants on the paraffin film showed a C-shape. 12 P9E3P6S <C 12 P9 <C 12 P9E3P6E2S <C 12 The P9E3S exhibits a consistent pattern, with contact angles all less than 90°. When the droplet size is less than 90°, the surface is considered highly wettable; when the droplet size is greater than 90°, the surface is considered poorly wettable. Therefore, all four E-surfactants exhibit good wettability on paraffin films, enabling wettability reversal and facilitating oil droplet detachment from the rock, thereby improving oil recovery. The wettability test results are shown in the attached diagram. Figure 12 As shown.

[0105] The sulfate E-surfactant containing multiple PPO and PEO polyether blocks provided by this invention exhibits excellent comprehensive performance due to its unique molecular structure: the amphiphilicity of the PPO block can compensate for the hydrophobicity of the alkyl chain and also provide weak polarity; the polar contribution of the PEO block can significantly improve the electrolyte resistance of the surfactant. The alternating intercalation of multiple PPO and PEO blocks enables the E-surfactant to form a dense packing at the interface, resulting in excellent oil-water interface properties, which is beneficial for generating ultra-low interfacial tension. By adjusting the ratio of PPO and PEO and the degree of polymerization, the oil displacement performance can be adjusted, giving the E-surfactant better environmental adaptability and avoiding problems such as chromatographic separation, performance stability, and environmental pollution caused by compounding.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a multi-block polyether type E-surfactant for oil displacement, characterized in that, Includes the following steps: (1) Preparation of multi-block polyether: fatty alcohol, catalyst KOH and 18-crown ether-6 are added to a batch reactor in sequence, and triblock APmEnPp or tetrablock APmEnPpEe polyether blocks are prepared by propoxylation reaction or by propoxylation and ethoxylation reaction. Fatty alcohols are straight-chain saturated alcohols with 8-18 carbon atoms; m takes values ​​of 3-30, n takes values ​​of 3-30, p takes values ​​of 2-20, and e takes values ​​of 2-20. (2) Preparation of multi-block polyether type E-surfactant: Under urea catalysis, the polyether block obtained in step (1) is reacted with aminosulfonic acid to prepare fatty alcohol polyether ammonium sulfate intermediate; NaOH aqueous solution is used for neutralization to obtain crude fatty alcohol polyether sodium sulfate, which is then filtered and evaporated to remove impurities to obtain fatty alcohol polyether sodium sulfate, thus obtaining a multi-block polyether type E-surfactant for oil displacement.

2. The method for preparing a multi-block polyether E-surfactant for oil displacement according to claim 1, characterized in that, In step (1), the preparation of triblock APmEnPp is specifically as follows: Fatty alcohol, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor. Propylene oxide was added at 130-145℃ to carry out a propoxylation reaction to obtain a monoblock APm; ethylene oxide was added at 125℃-135℃ to carry out an ethoxylation reaction to obtain a diblock APmEn. The mass of the added catalyst potassium hydroxide is 2‰-4‰ of the total mass of fatty alcohol and propylene oxide; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the molar ratio of the added propylene oxide to the fatty alcohol is (1.00-1.20)m:1.

00. The molar ratio of ethylene oxide to fatty alcohol added is (1.00-1.20)n:1.00; Diblock APmEn, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor, and propylene oxide was added at 130℃-145℃ to carry out a propoxylation reaction to obtain APmEnPp polyether block. The added catalyst, potassium hydroxide, has a mass of 2‰-4‰ of the total mass of the diblock APmEn and propylene oxide; the added complexing agent, 18-crown ether-6, has a molar ratio of (1.00-3.00):1.00 to potassium hydroxide; and the added propylene oxide has a molar ratio of (1.40-1.80)p:1.00 to propylene oxide.

3. The method for preparing a multi-block polyether E-surfactant for oil displacement according to claim 1, characterized in that, In step (1), the preparation of the tetrablock APmEnPpEe is specifically as follows: Fatty alcohol, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor. Propylene oxide was added at 130-145℃ to carry out a propoxylation reaction to obtain a monoblock APm; ethylene oxide was added at 125℃-135℃ to carry out an ethoxylation reaction to obtain a diblock APmEn. The mass of the added catalyst potassium hydroxide is 2‰-4‰ of the total mass of fatty alcohol and propylene oxide; the molar ratio of the added complexing agent 18-crown ether-6 to the catalyst potassium hydroxide is (1.00-3.00):1.00; the molar ratio of the added propylene oxide to the fatty alcohol is (1.00-1.20)m:1.

00. The molar ratio of ethylene oxide to fatty alcohol added is (1.00-1.20)n:1.00; Diblock APmEn, catalyst KOH, and 18-crown ether-6 were sequentially added to a batch reactor. Propylene oxide was added at 130℃-145℃ to carry out a propoxylation reaction to obtain triblock APmEnPp. Ethylene oxide was added at 125℃-135℃ to carry out an ethoxylation reaction to obtain APmEnPpEe polyether block. The added catalyst, potassium hydroxide, has a mass of 2‰-4‰ of the total mass of the diblock APmEn and propylene oxide; the added complexing agent, 18-crown ether-6, has a molar ratio of (1.00-3.00):1.00 to potassium hydroxide; and the added propylene oxide has a molar ratio of (1.40-1.80)p:1.00 to propylene oxide. The molar ratio of added ethylene oxide to diblock APmEn is (1.00-1.30)e:1.

00.

4. The method for preparing a multi-block polyether E-surfactant for oil displacement according to claim 1, characterized in that, Step (2) includes: Under urea catalysis, the polyether block obtained in step (1) is reacted with aminosulfonic acid at a molar ratio of 1:(1.15~3) at 100℃-120℃ for 2-4h to obtain fatty alcohol polyether ammonium sulfate intermediate; the reaction solution is neutralized with a NaOH aqueous solution with a concentration of 10-50wt% to pH=11-13 to obtain crude fatty alcohol polyether sodium sulfate, which is then filtered and evaporated at 40-60℃ to remove impurities to obtain fatty alcohol polyether sodium sulfate, thus obtaining a multi-block polyether type E-surfactant for oil displacement.

5. A multi-block polyether-type E-surfactant for oil displacement, prepared by the preparation method according to any one of claims 1-4, characterized in that, The oil displacement is achieved by using a multi-block polyether E-surfactant to generate an ultra-low interfacial tension on the order of 10⁻³ mN / m, thereby improving the oil displacement efficiency.

6. The use of the multi-block polyether E-surfactant for oil displacement according to claim 5, characterized in that, The aforementioned multi-block polyether E-surfactant for oil displacement is used in tertiary oil recovery.

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