Surfactant for oil-displacing agent, oil-displacing agent and preparation method of surfactant

Abstract

The invention provides a surfactant for an oil-displacing agent, the oil-displacing agent and a preparation method of the oil-displacing agent. The method comprises the following steps: mixing a C10-C18 alkyl alcohol material separated from crude oil of a target oil reservoir or a high-salinity and high-temperature oil reservoir of a target oil-displacing agent surfactant with concentrated sulfuric acid to obtain a mixture for preparing the surfactant, reacting at 55-75 DEG C, cooling a reaction product, adding hydroxide to adjust the pH value to 6.8-7.2, adding salt to perform salting-out purification, and separating the crude oil from the crude oil in the target oil reservoir or the high-salinity and high-temperature oil reservoir to obtain the target oil-displacing agent surfactant. And preparing to obtain the surfactant for the target oil-displacing agent. The preparation method comprises the following steps: mixing a surfactant for a target oil-displacing agent with an auxiliary surfactant, a polymer additive, a stabilizer, a wetting reversal agent and water to obtain a mixed stock solution; sequentially carrying out ultrasonic treatment and high-pressure homogenization treatment on the mixed stock solution to obtain the target oil-displacing agent. Wherein the wetting reversal agent is a mixture of alkyl trimethyl ammonium bromide, a fluorine surfactant and fatty acid in a mass ratio of (3-4): (0.8-1.5): 1.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil displacement agents, and relates to a surfactant for oil displacement agents and a preparation method thereof, and a low-tension wetting control oil displacement agent for composite flooding and a preparation method thereof. Background Art

[0002] In the field of oil extraction, crude oil recovery efficiency is directly related to energy utilization and economic benefits. Currently, conventional extraction methods have reached recovery bottlenecks in many oil fields, making the extraction of remaining reservoirs increasingly difficult. These reservoirs are often located in complex geological structures, such as fractured and heterogeneous reservoirs. Their extraction efficiency is limited by factors such as oil-water interfacial tension, rock wettability, and reservoir fluid properties. Therefore, developing an oil displacement agent that can effectively reduce oil-water interfacial tension and regulate reservoir wettability has become a key technology for improving oil recovery efficiency.

[0003] Currently, commonly used oil recovery technologies include water flooding, polymer flooding, and surfactant flooding. Surfactant flooding agents can reduce oil-water interfacial tension and improve reservoir wettability, thereby increasing oil recovery efficiency. However, traditional surfactant flooding agents suffer from poor stability. When used in highly salinized and high-temperature reservoirs, surfactants are prone to degradation, affecting recovery effectiveness and limiting their large-scale application.

[0004] In summary, there is still a need to study oil displacement agents with stable performance in high-salinity, high-temperature reservoirs that can reduce oil-water interfacial tension and improve reservoir wettability. Summary of the Invention

[0005] The object of the present invention is to provide an oil displacement agent which has stable performance when used in oil reservoirs including high-salinity and high-temperature oil reservoirs, can reduce oil-water interfacial tension, and improve reservoir wettability.

[0006] In order to achieve the above objectives, the present invention provides the following two technical solutions.

[0007] In a first aspect, the present invention provides a method for preparing a surfactant for an oil-displacing agent, wherein the preparation method comprises:

[0008] The alkyl alcohol material is mixed with concentrated sulfuric acid to obtain a mixture for preparing a surfactant; wherein the alkyl alcohol material is selected from crude oil with carbon atoms of C 2 separated from the target oil reservoir for the target oil displacement surfactant. 10 -C 18 The carbon number of the alkyl alcohol material or the crude oil separated from the high mineralization and high temperature oil reservoir is C 10 -C 18The alkyl alcohol material (the alkyl alcohol may have a linear hydrocarbon skeleton or a branched hydrocarbon skeleton); wherein the mass concentration of H2SO4 in the concentrated sulfuric acid is not less than 95%; the molar ratio of hydroxyl groups in the alkyl alcohol material to H2SO4 in the concentrated sulfuric acid is 1:1-1.8; high mineralization refers to a total mineralization (i.e., total dissolved solids TDS) of formation water ≥50,000 ppm; high temperature refers to a formation temperature ≥90°C;

[0009] The surfactant preparation mixture is reacted at 55-75° C., the obtained reaction product is cooled to 40-55° C., hydroxide is added to adjust the pH value to 6.8-7.2, and salt is added to the pH-adjusted product for salting out and purification, thereby preparing the target oil displacement agent surfactant.

[0010] In the preparation method of the surfactant for oil displacement agent provided by the present invention, the carbon number of C is separated from the crude oil of the target oil reservoir for use in preparing the surfactant for oil displacement agent. 10 -C 18 The special alkyl alcohol material is subjected to sulfonation reaction with concentrated sulfuric acid, and then hydroxide is added to adjust the pH value and salting out and purification is performed to prepare a surfactant for oil displacement agent. The prepared surfactant for oil displacement agent can well adapt to the temperature and salinity conditions of the target oil reservoir (even high temperature and high salinity conditions) when used in the target oil reservoir, achieve low interfacial tension, regulate the wettability of the oil reservoir, and reduce the potential impact on the oil reservoir and the environment. In the preparation method of the surfactant for oil displacement agent provided by the present invention, a carbon atom number of C is separated from crude oil of high salinity and high temperature oil reservoir. 10 -C 18 The special alkyl alcohol material is subjected to a sulfonation reaction with concentrated sulfuric acid, and then hydroxide is added to adjust the pH value and salting out and purification is performed to prepare a surfactant for oil displacement agent. The prepared surfactant for oil displacement agent can well adapt to the temperature and salinity conditions of high-temperature and high-salinity oil reservoirs, achieve low interfacial tension, and regulate the wettability of the oil reservoir.

[0011] In the preparation process of the oil displacement agent provided by the present invention, C 10 -C 18 Alkyl alcohol, using C 10 -C 18 The alkyl alcohol can ensure that the oil displacement agent forms an ideal molecular structure during the preparation process. The alkyl chain of moderate length can ensure sufficient hydrophobicity, which helps to reduce the oil-water interfacial tension, while maintaining sufficient hydrophilicity to allow it to exist stably in the aqueous phase; long-chain alkyl alcohols help to form more compact molecular stacking, which is particularly important for adjusting the wettability of the reservoir and improving the oil displacement efficiency; the alkyl chain of appropriate length helps to improve the thermodynamic stability of the oil displacement agent, so that it can maintain its performance in the high temperature and high pressure environment of the reservoir.

[0012] During the preparation of the oil-displacing agent provided by the present invention, high-concentration sulfuric acid is used. High-concentration sulfuric acid can promote the sulfonation reaction of alkyl alcohols, accelerate the introduction of sulfonic acid groups, and improve the preparation efficiency of surfactants. The use of high-concentration reagents is conducive to the formation of surfactant molecules, ensuring complete reaction and avoiding side reactions. The use of high-concentration reagents has a high reactant concentration, which is conducive to subsequent salting-out purification, neutralization and drying processes, simplifies the process flow, and reduces energy consumption. The use of high-concentration reagents helps to improve the purity and performance of the final product, ensuring that the oil-displacing agent exhibits better wetting control ability and improves the efficiency of crude oil recovery in the oil reservoir.

[0013] According to the specific embodiment provided in the first aspect, preferably, the alkyl alcohol material is selected from the crude oil of the target oil displacement agent surfactant target use oil reservoir with carbon atoms of C 10 -C 18 Alkyl alcohol materials;

[0014] More preferably, the target oil reservoir is a high-salinity, high-temperature oil reservoir.

[0015] According to the specific embodiment provided in the first aspect, preferably, the number of carbon atoms separated from crude oil is C 10 -C 18 The alkyl alcohol material is a purified product of a fraction obtained by atmospheric distillation of crude oil within a distillation range of 200-350°C; more preferably, the purification comprises solvent extraction and crystallization; further preferably, a polar solvent such as methanol and / or ethanol is used in the solvent extraction; further preferably, the volume ratio of the solvent used in the solvent extraction process to the fraction is 1:1-2; further preferably, the crystallization process adopts a low-temperature crystallization method of 0-5°C;

[0016] In one embodiment, the number of carbon atoms separated from crude oil is C 10 -C 18 The alkyl alcohol material is obtained by the following method:

[0017] Pretreatment: heat the crude oil to 80-100℃, dehydrate it with a demulsifier, and then desalt it;

[0018] Distillation separation: The pre-treated crude oil is subjected to atmospheric distillation, and the crude oil with a distillation range of 200-350℃ (corresponding to the carbon number of C 10 -C 18 The target fraction is obtained by fractionating within the boiling point of the alkyl alcohol.

[0019] Solvent extraction: A polar solvent (e.g., methanol and / or ethanol) is mixed with the target fraction (the volume ratio of the polar solvent to the target fraction is preferably 1:1-2) to extract and remove non-alcohol impurities (e.g., alkanes and aromatics);

[0020] Low-temperature crystallization separation: The extract obtained by solvent extraction is cooled to 0-5°C and allowed to stand (preferably for 12-24 hours) to precipitate alkyl alcohol crystals, which are then collected;

[0021] Drying: The collected alkyl alcohol crystals are vacuum dried (the vacuum drying temperature is preferably 50-60°C and the pressure is preferably ≤10kPa) until the moisture content is ≤0.5%, and the carbon atoms separated from the crude oil are C 10 -C 18 Alkyl alcohol materials;

[0022] Furthermore, based on the crude oil quality, the demulsifier dosage is 10-200ppm; further, the demulsifier dosage is adjusted according to the water content. Generally,

[0023] Based on the total mass of crude oil, when the water content of crude oil is less than 0.5% (i.e. low water content, the emulsification degree is usually not high at this time): the demulsifier dosage is 10-50ppm;

[0024] Based on the total mass of crude oil, when the water content of crude oil is 0.5-2% (i.e. medium-high water content, the emulsification degree is usually medium): the demulsifier dosage is 50-150ppm;

[0025] Based on the total mass of crude oil, when the water content of crude oil is greater than 2% (i.e. high water content, in which case the emulsification degree is serious): the demulsifier dosage is 150-200ppm;

[0026] Further, the desalination treatment is carried out using an electric desalination device at a voltage of 10-20 kV; further, the treatment time is 20-60 minutes;

[0027] Furthermore, during the solvent extraction purification process, the extraction temperature is 40-60°C;

[0028] Furthermore, during the solvent extraction purification process, stirring was performed at a speed of 200-400 rpm;

[0029] Furthermore, during the solvent extraction purification process, the extraction time is 1-2 h;

[0030] Furthermore, the alkyl alcohol crystals are collected by centrifugal separation; furthermore, the rotation speed of the centrifugal separation is 3000-5000 rpm, and the time is 10-20 minutes.

[0031] According to the specific embodiment provided in the first aspect, preferably, the molar ratio of hydroxyl groups in the alkyl alcohol material to H2SO4 in concentrated sulfuric acid is 1:1-1.5; more preferably, the molar ratio of hydroxyl groups in the alkyl alcohol material to H2SO4 in concentrated sulfuric acid is 1:1-1.2.

[0032] According to the specific embodiment provided in the first aspect, preferably, the surfactant preparation mixture is reacted at 60-70°C.

[0033] According to the specific embodiment provided in the first aspect, preferably, the obtained reaction product is cooled to 45-50° C. and then hydroxide is added to adjust the pH value to 6.8-7.2.

[0034] According to the specific embodiment provided in the first aspect, preferably, during the salting-out purification process of adding salt to the pH-adjusted product, the mass ratio of the added salt to the pH-adjusted product is 1.5-2:1.

[0035] According to the specific embodiment provided in the first aspect, preferably, the method for preparing a surfactant for an oil-displacing agent further comprises: drying, crushing, and sieving the product obtained by salting out and purification to obtain the target surfactant for an oil-displacing agent;

[0036] More preferably, the mesh size of the sieve is 80-120 meshes.

[0037] According to the specific embodiment provided in the first aspect, preferably, the reaction time of the surfactant preparation mixture is 3-4 hours.

[0038] According to the specific embodiment provided in the first aspect, preferably, the surfactant preparation mixture is subjected to a reaction process and stirred at a stirring speed of 250-350 rpm.

[0039] According to the specific embodiment provided in the first aspect, preferably, the adding salt to the pH-adjusted product for salting out purification comprises:

[0040] adding salt to the pH-adjusted product to obtain a mixture which is centrifuged to collect crystals, and washing and drying the collected crystals to complete salting-out purification;

[0041] During the salting-out process, the addition of salt causes the surfactant to precipitate from the solution. Centrifugal separation effectively removes impurities, improving the surfactant's purity. Centrifugal separation and subsequent drying effectively remove water and other volatile impurities, enhancing the surfactant's chemical stability. Washing eliminates the presence of other chemical reagents, improving the surfactant's safety and environmental friendliness. High-purity surfactants help enhance the performance of oil displacement agents, including reducing oil-water interfacial tension and improving wettability, thereby increasing crude oil recovery.

[0042] More preferably, the centrifugal speed during the centrifugal separation process is 2500-3500 rpm; further preferably, the centrifugal time during the centrifugal separation process is 8-20 min;

[0043] More preferably, washing is performed with water;

[0044] More preferably, the drying temperature is 85-100° C.; further preferably, the drying time is 8-20 h.

[0045] According to the specific embodiment provided in the first aspect, preferably, the hydroxide comprises at least one of sodium hydroxide and potassium hydroxide; more preferably, the hydroxide is sodium hydroxide; further preferably, the sodium hydroxide is added in the form of a sodium hydroxide solution; wherein, based on the total mass of the sodium hydroxide solution being 100%, the concentration of sodium hydroxide in the sodium hydroxide solution is 25-35%.

[0046] According to the specific embodiment provided in the first aspect, preferably, the salt added in the salting-out purification includes at least one of chloride, nitrate, and sulfate; more preferably, the salt added in the salting-out purification includes at least one of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, and potassium sulfate; further preferably, the salt added in the salting-out purification is sodium chloride.

[0047] In a second aspect, the present invention provides a surfactant for an oil-displacing agent, which can be prepared by the preparation method of the surfactant for an oil-displacing agent provided by the first aspect of the present invention.

[0048] In a third aspect, the present invention provides the use of the surfactant for oil displacement agent provided in the second aspect of the present invention as an oil displacement agent component in oil reservoir development; wherein the oil reservoir is the source reservoir of the alkyl alcohol material as the raw material for preparing the surfactant for oil displacement agent.

[0049] In a fourth aspect, the present invention provides a method for preparing an oil-displacing agent, wherein the preparation method comprises:

[0050] Mixing a primary surfactant, a secondary surfactant, a polymer additive, a stabilizer, a wettability reversal agent and water to obtain a mixed stock solution;

[0051] The mixed stock solution is subjected to ultrasonic treatment and high-pressure homogenization treatment in sequence to obtain an oil-displacing agent;

[0052] The main surfactant is the surfactant for oil displacement provided by the second aspect of the present invention; the auxiliary surfactant is a quaternary ammonium salt; the polymer auxiliary agent is polyacrylamide; the stabilizer is a block copolymer of polyoxypropylene and polyoxyethylene; the wettability reversal agent is a mixture of alkyltrimethylammonium bromide, fluorinated surfactant and fatty acid in a mass ratio of 3-4:0.8-1.5:1;

[0053] Among them, based on the total mass of the main surfactant, the auxiliary surfactant and water as 100%, the amount of the main surfactant is 2-7%, the amount of the auxiliary surfactant is 0.5-3%, the amount of the polymer additive is 0.1-0.5%, the amount of the stabilizer is 0.05-0.1%, and the amount of the wettability reversal agent is 0.5-1.5%.

[0054] In the method for preparing the oil-displacing agent provided by the present invention, the alkyl alcohol material used in the preparation of the main surfactant is selected from the crude oil of the target oil-displacing agent surfactant target oil reservoir, that is, the target oil-displacing agent target oil reservoir separated from the carbon atom number C 10 -C 18 The carbon number of the alkyl alcohol material or the crude oil separated from the high mineralization and high temperature oil reservoir is C 10 -C 18 Alkyl alcohol material (the alkyl alcohol may have a straight chain carbon hydrogen skeleton or a branched chain carbon hydrogen skeleton).

[0055] The oil-displacing agent provided by the present invention is used in conjunction with a special main surfactant and a co-surfactant and a special wettability reversal agent, and it is possible to achieve effective reduction of oil-water interfacial tension and improvement of reservoir wettability under reservoir conditions including high temperature and high salinity, thereby increasing crude oil recovery; wherein, the synergistic effect of the special main surfactant and the co-surfactant helps to improve the fluidity of the fluid, making the oil-displacing agent more permeable in the reservoir, and improving the oil displacement effect; wherein, alkyl trimethylammonium bromide, as a cationic surfactant, can significantly reduce the interfacial tension between the aqueous phase and the reservoir rock, and improve the oil displacement efficiency; fluorosurfactants have extremely low surface tension and good interfacial activation properties, and can enhance the wettability reversal effect; fatty acids belong to a type of anionic surfactant, and can further improve the oil-water distribution state under synergistic action, and promote wettability reversal. The oil-displacing agent provided by the present invention enhances the stability of the oil-water interface by the addition of polymer additives and stabilizers, is conducive to oil-water separation, and improves oil displacement efficiency. The synergistic effect of the main surfactant and the co-surfactant improves the fluidity of the fluid, making the oil-displacing agent more permeable in the reservoir, and improving the oil displacement effect.

[0056] The application of ultrasonic treatment and high-pressure homogenizer can further refine the oil displacement agent particles, improve its dispersibility and stability in the oil reservoir, and enhance the penetration ability of the oil displacement agent.

[0057] According to different reservoir conditions, by adjusting the proportion of oil displacement agent components and processing parameters, its adaptability and oil displacement effect in different reservoir environments can be improved.

[0058] According to the specific embodiment provided in the fourth aspect, the surfactant with a quaternary ammonium salt structure has high chemical stability, can effectively resist the high temperature and high pressure in the oil reservoir environment, and extend the service life of the oil displacement agent;

[0059] Preferably, the quaternary ammonium salt includes at least one of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, didodecyldimethylammonium chloride and benzyltrimethylammonium chloride;

[0060] More preferably, the quaternary ammonium salt can be prepared by the following preparation method:

[0061] Adding hydrogen chloride gas to dodecyldimethyl tertiary amine at 50-60° C., then reacting at 45-65° C. to neutralize excess hydrogen chloride in the resulting reaction product, and then purifying it by reduced pressure distillation or solvent extraction, and then separating the quaternary ammonium salt and drying it, thereby completing the preparation of the quaternary ammonium salt;

[0062] Further preferably, neutralizing the excess hydrogen chloride in the obtained reaction product is carried out using at least one of sodium hydroxide, potassium hydroxide, sodium carbonate and triethylamine;

[0063] Further preferably, the reaction time is 3-5h;

[0064] Dodecyldimethylamine reacts with hydrogen chloride to form a quaternary ammonium salt, which, in combination with the primary surfactant, enhances surface activity and effectively reduces interfacial tension. Precise control of reaction temperature and time ensures a complete and controllable reaction, avoiding the formation of by-products. Neutralization of excess hydrogen chloride with sodium hydroxide solution, combined with purification methods such as vacuum distillation or solvent extraction, effectively removes any impurities that may remain in the reaction and improves product purity.

[0065] According to the specific embodiment provided in the fourth aspect, preferably, the polymer auxiliary agent can be prepared by the following preparation method:

[0066] Mixing acrylamide, an initiator, and water to obtain a mixture to be polymerized; adjusting the pH value of the mixture to be polymerized to 8-9, and then performing a polymerization reaction at a temperature of 50-60° C.; drying and pulverizing the polymerization reaction product to obtain the polymer auxiliary agent;

[0067] Wherein, the mass of the initiator is 0.1-2.5% of the mass of acrylamide, and the mass of the water is 5-10 times the mass of acrylamide;

[0068] More preferably, the initiator comprises at least one of ammonium persulfate, potassium persulfate and azobisisobutyronitrile;

[0069] More preferably, the pH value of the mixture to be polymerized is adjusted using at least one of sodium hydroxide, sodium carbonate and ammonia water;

[0070] More preferably, the polymerization reaction time is 3-8h;

[0071] More preferably, the pulverization is pulverization to no more than 100 μm;

[0072] Carrying out the polymerization reaction at a temperature of 50-60°C is beneficial to improving the swelling properties of the polymer, making it easier to dissolve in the aqueous phase in subsequent applications, and improving the dispersibility and stability of the oil displacement agent; by adjusting the amount of initiator, the molecular weight of the polymer can be controlled, thereby affecting its adsorption properties at the oil-water interface and enhancing the performance of the oil displacement agent; optimizing the pH value ensures that the polymerization reaction is carried out under optimal conditions, which is conducive to the formation of polymers with uniform structure and stable performance; the use of polymer additives can significantly improve the adsorption capacity of the oil displacement agent on reservoir rocks, while increasing the viscosity of the aqueous phase and improving the oil displacement efficiency; the polymer product is dried and crushed to facilitate packaging, transportation and storage, while ensuring that it can be quickly and evenly dispersed in water when used.

[0073] According to the specific embodiment provided in the fourth aspect, the block copolymer of polyoxypropylene and polyoxyethylene can form a stable film at the oil-water interface due to its special molecular structure, effectively reducing the interfacial tension and enhancing the stability of the emulsion; by changing the content of polyoxyethylene, the hydrophilic-lipophilic balance value of the block copolymer of polyoxypropylene and polyoxyethylene can be adjusted; the block copolymer of polyoxyethylene and polyoxypropylene generally has low chemical activity and is not easy to react with other chemical substances, which helps to maintain the chemical stability of the oil displacement agent;

[0074] Preferably, the mass content of the polyoxyethylene segment in the block copolymer of polyoxypropylene and polyoxyethylene is 20-40% (based on the total mass of the block copolymer of polyoxypropylene and polyoxyethylene being 100%).

[0075] According to the specific embodiment provided in the fourth aspect, preferably, the fluorosurfactant includes at least one of potassium perfluorooctane sulfonate, perfluorononanoic acid and perfluoropolyether.

[0076] According to the specific embodiment provided in the fourth aspect, preferably, the fatty acid includes at least one of lauric acid, stearic acid, oleic acid and isostearic acid.

[0077] According to the specific embodiment provided in the fourth aspect, preferably, during the ultrasonic treatment, the ultrasonic power is 450-550W and the ultrasonic frequency is 18-25kHz;

[0078] More preferably, the ultrasonic treatment time is 25-45 min.

[0079] According to the specific embodiment provided in the fourth aspect, preferably, during the high-pressure homogenization process, the pressure is 250-350 bar;

[0080] More preferably, during the high-pressure homogenization process, the number of treatments is 2-4 times, and each treatment time is 1-2 minutes.

[0081] According to the specific embodiment provided in the fourth aspect, preferably, the mixing of the main surfactant, the auxiliary surfactant, the polymer auxiliary agent, the stabilizer, the wettability reversal agent and water comprises:

[0082] dissolving the primary surfactant and the auxiliary surfactant in the water to obtain an active agent solution;

[0083] Then, a polymer auxiliary, a stabilizer, and a wettability reversal agent are sequentially added to the active agent solution, and the active agent solution, the polymer auxiliary, the stabilizer, and the wettability reversal agent are mixed, thereby achieving mixing of the main surfactant, the auxiliary surfactant, the polymer auxiliary, the stabilizer, the wettability reversal agent, and water;

[0084] More preferably, the primary surfactant and the auxiliary surfactant are dissolved in the water at 25-55° C.; more preferably, the primary surfactant and the auxiliary surfactant are dissolved in the water under stirring; wherein the stirring speed is 300-500 rpm; further preferably, the stirring time is 20-40 min;

[0085] More preferably, the active agent solution, polymer auxiliary, stabilizer and wettability reversal agent are mixed at 45-55°C;

[0086] More preferably, the active agent solution, polymer auxiliary agent, stabilizer and wettability reversal agent are mixed at a stirring speed of 700-900 rpm; further preferably, the stirring time is 0.5-2 h.

[0087] In a fifth aspect, the present invention provides an oil-displacing agent, which can be prepared by the method for preparing the oil-displacing agent provided in the fourth aspect of the present invention.

[0088] In a sixth aspect, the present invention provides an application of the oil displacement agent provided in the fifth aspect of the present invention in oil reservoir development; wherein the oil reservoir is the source reservoir of the alkyl alcohol material, which is the raw material for preparing the main surfactant in the oil displacement agent.

[0089] The technical solution provided by the present invention uses a carbon atom number of C separated from crude oil in a target oil reservoir to be used for preparing a surfactant for an oil displacement agent. 10 -C 18 A special surfactant for oil displacement is prepared from a special alkyl alcohol material. The surfactant is combined with an auxiliary surfactant, a special wettability reversal agent, and a polymer additive and stabilizer to prepare an oil displacement agent that can adapt well to the temperature and salinity conditions of the target reservoir when used in the target reservoir, even under high temperature and high salinity conditions. Another technical solution provided by the present invention uses a carbon atom number of C separated from crude oil with high salinity and high temperature. 10 -C 18 A special surfactant for oil displacement is prepared from a special alkyl alcohol material. This surfactant, combined with an auxiliary surfactant, a special wettability reversal agent, and supplemented with a polymer additive and a stabilizer, produces an oil displacement agent that is well adapted to the temperature and salinity conditions of high-temperature and high-salinity reservoirs. The oil displacement agent provided by the present invention can effectively reduce oil-water interfacial tension and improve reservoir wettability under reservoir conditions including high temperature and high salinity, thereby effectively increasing the recovery rate. By effectively increasing the recovery rate, the residual oil content in the reservoir can be reduced, helping to extend the production cycle of the reservoir and increase the economic life of the oil field. DETAILED DESCRIPTION

[0090] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0091] Example 1

[0092] This embodiment provides a surfactant for an oil-displacing agent and an oil-displacing agent.

[0093] The surfactant for oil displacement agent is prepared by the following preparation method:

[0094] 1) mixing an alkyl alcohol material with concentrated sulfuric acid to obtain a mixture for preparing a surfactant;

[0095] The molar ratio of the hydroxyl groups in the alkyl alcohol material to the H2SO4 in the concentrated sulfuric acid is 1:1.25;

[0096] The alkyl alcohol material is selected from crude oil of the target oil displacement agent surfactant target use reservoir A (also the target use reservoir of the target oil displacement agent in this embodiment, the temperature of reservoir A is about 85 ° C, the salinity is about 100000 ppm, and the pressure is about 10 MPa). 14 The number of carbon atoms separated from crude oil is C 14 The linear hydrocarbon skeleton alkyl alcohol material is the product of the 275℃ fraction obtained by atmospheric distillation of crude oil, which is purified by solvent extraction and low-temperature crystallization. The number of carbon atoms separated from crude oil is C 14 The straight-chain hydrocarbon skeleton alkyl alcohol material is specifically obtained by the following method:

[0097] Pretreatment: The crude oil was heated to 90°C and dehydrated with a demulsifier (100 ppm based on the crude oil mass); then desalted for 40 minutes using an electric desalter at 15 kV.

[0098] Distillation separation: The pre-treated crude oil is distilled under normal pressure, and the crude oil at 275℃ (corresponding to C 14 boiling point of alkyl alcohol) to obtain the target fraction;

[0099] Solvent extraction treatment: polar solvent methanol was mixed with the target fraction at a volume ratio of 1:1.5, and the extraction time was 1.5 h at 50°C and a stirring speed of 300 rpm to remove non-alcoholic impurities;

[0100] Low-temperature crystallization separation: The extract obtained by solvent extraction was cooled to 2.5°C and allowed to stand for 18 hours to precipitate alkyl alcohol crystals, which were then collected by centrifugation at 4000 rpm for 15 minutes.

[0101] Drying: The collected alkyl alcohol crystals were vacuum dried (vacuum drying temperature was 55 ° C, pressure was 5kPa) until the moisture content was 0.2%, and the carbon number of the separated crude oil was C 14 Alkyl alcohol materials;

[0102] Wherein, the mass concentration of H2SO4 in the concentrated sulfuric acid is 96.5%;

[0103] 2) stirring the surfactant preparation mixture at 65° C. and 300 rpm for 3.5 hours to react, cooling the obtained reaction product to 47.5° C. and adding a sodium hydroxide solution having a sodium hydroxide mass concentration of 30% to adjust the pH value to 7, adding sodium chloride to the pH-adjusted product to obtain a mixture, centrifuging (centrifugation time 14 minutes, centrifugal speed 3000 rpm), collecting crystals, washing the collected crystals with deionized water, and then drying at 92.5° C. for 14 hours to complete salting-out purification;

[0104] The mass ratio of sodium chloride to the pH-adjusted product is 1.75:1;

[0105] 3) Drying, crushing, and sieving the product obtained by salting out and purification to obtain the target surfactant for oil displacement agent; wherein the mesh number of the sieve is 100 mesh.

[0106] The oil-displacing agent is prepared by the following preparation method:

[0107] 1) dissolving the primary surfactant and the auxiliary surfactant in water at 40° C. with stirring to obtain an active agent solution;

[0108] Among them, the stirring speed is 400 rpm and the stirring time is 30 min;

[0109] Among them, the main surfactant is the surfactant for oil displacement agent provided in this embodiment;

[0110] The auxiliary surfactant is a quaternary ammonium salt, which is prepared by the following method: adding dodecyldimethyl tertiary amine to a reactor, introducing hydrogen chloride gas while maintaining the temperature at 55° C., controlling the temperature at 55° C. under stirring (stirring speed of 350 rpm) for 4 hours until the reaction is complete; neutralizing excess hydrogen chloride with a sodium hydroxide solution having a sodium hydroxide mass concentration of 30%, purifying the product by a reduced pressure distillation method, separating the quaternary ammonium salt, and drying the quaternary ammonium salt to constant weight to obtain the auxiliary surfactant;

[0111] Among them, the dosage of the main surfactant is 4.5% and the dosage of the auxiliary surfactant is 2%;

[0112] 2) Adding a polymer additive, a stabilizer, and a wettability reversal agent to the active agent solution in sequence, and stirring at 50° C. and 800 rpm for 1.25 h until the components are fully mixed and dissolved to obtain a mixed stock solution;

[0113] The polymer auxiliary agent is polyacrylamide, which is prepared by the following method: acrylamide and an initiator, ammonium persulfate, are dissolved in deionized water and stirred uniformly, the pH value is adjusted to 8.5 with sodium carbonate, a polymerization reaction is carried out at 55° C. for 5.5 hours, and the product after the polymerization reaction is dried and crushed to a particle size of ≤100 μm to obtain the polymer auxiliary agent; wherein the initiator accounts for 0.85% of the mass of the acrylamide, and the amount of deionized water added is 7 times the mass of the acrylamide;

[0114] The stabilizer is a block copolymer of polyoxypropylene and polyoxyethylene, wherein the mass content of the polyoxyethylene segment in the block copolymer of polyoxypropylene and polyoxyethylene is 30%;

[0115] The wettability reversal agent is a mixture of alkyl trimethylammonium bromide, fluorinated surfactant perfluoropolyether, and fatty acid isostearic acid in a mass ratio of 4:1:1.

[0116] Wherein, based on the total mass of the main surfactant, the auxiliary surfactant and water as 100%, the amount of the polymer additive is 0.35%, the amount of the stabilizer is 0.075%, and the amount of the wettability reversal agent is 1%;

[0117] 3) The mixed stock solution was subjected to ultrasonic treatment with a power of 500 W, an ultrasonic frequency of 21.5 kHz, and a treatment time of 35 min; then, a high-pressure homogenizer was used for high-pressure homogenization treatment with a pressure set to 300 bar, and the treatment was performed three times, each treatment time of 1.5 min, to obtain the target oil-displacing agent.

[0118] Example 2

[0119] This embodiment provides a surfactant for an oil-displacing agent and an oil-displacing agent.

[0120] The surfactant for oil-displacing agent provided in this embodiment differs from the surfactant for oil-displacing agent provided in Example 1 only in that: during the preparation process, (1) alkyl alcohol and sulfuric acid are mixed in a molar ratio of 1:1, (2) the surfactant preparation mixture is stirred at 60°C at a stirring speed of 250 rpm for 3 hours to react, and the obtained reaction product is cooled to 45°C and then a sodium hydroxide solution with a sodium hydroxide mass concentration of 30% is added to adjust the pH value to 6.8, and (3) the mass ratio of sodium chloride to the product after pH adjustment is 1.5:1.

[0121] The oil-displacing agent provided in this embodiment is different from the oil-displacing agent provided in Example 1 only in that the main surfactant is the surfactant for the oil-displacing agent provided in this embodiment.

[0122] Example 3

[0123] This embodiment provides a surfactant for an oil-displacing agent and an oil-displacing agent.

[0124] The surfactant for oil-displacing agent provided in this embodiment differs from the surfactant for oil-displacing agent provided in Example 1 only in that: during the preparation process, (1) alkyl alcohol and sulfuric acid are mixed in a molar ratio of 1:1.5, (2) the surfactant preparation mixture is stirred at 350 rpm for 4 h at 70°C for reaction, and the obtained reaction product is cooled to 50°C and then a sodium hydroxide solution with a sodium hydroxide mass concentration of 30% is added to adjust the pH value to 7.2, and (3) the mass ratio of sodium chloride to the pH-adjusted product is 2:1.

[0125] The oil-displacing agent provided in this embodiment is different from the oil-displacing agent provided in Example 1 only in that the main surfactant is the surfactant for the oil-displacing agent provided in this embodiment.

[0126] Example 4

[0127] This embodiment provides an oil-displacing agent.

[0128] The oil-displacing agent provided in this embodiment is different from the oil-displacing agent provided in Example 1 only in that the preparation method of the auxiliary surfactant is different, specifically: dodecyldimethylamine is added to the reactor, hydrogen chloride gas is introduced under the condition of maintaining the temperature at 50°C, the temperature is controlled to 45°C and the reaction is carried out under stirring conditions (stirring speed is 300 rpm) for 3 hours until the reaction is complete; the excess hydrogen chloride is neutralized using a sodium hydroxide solution with a sodium hydroxide mass concentration of 30%, the product is purified by vacuum distillation, the quaternary ammonium salt is separated, and the quaternary ammonium salt is dried to constant weight to obtain an auxiliary surfactant.

[0129] Example 5

[0130] This embodiment provides an oil-displacing agent.

[0131] The oil-displacing agent provided in this embodiment is different from the oil-displacing agent provided in Example 1 only in that the preparation method of the auxiliary surfactant is different, specifically: dodecyldimethyl tertiary amine is added to the reactor, hydrogen chloride gas is introduced under the condition of maintaining the temperature at 60°C, the temperature is controlled to 65°C and the reaction is carried out under stirring conditions (stirring speed is 400 rpm) for 5 hours until the reaction is complete; the excess hydrogen chloride is neutralized using a sodium hydroxide solution with a sodium hydroxide mass concentration of 30%, the product is purified by vacuum distillation, the quaternary ammonium salt is separated, and the quaternary ammonium salt is dried to constant weight to obtain an auxiliary surfactant.

[0132] Example 6

[0133] This embodiment provides an oil-displacing agent.

[0134] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that: (1) based on the total mass of the main surfactant, the auxiliary surfactant and water being 100%, the amount of the polymer additive is 0.1%, the amount of the stabilizer is 0.05%, and the amount of the wettability reversal agent is 0.5%; (2) after the polymer additive, the stabilizer and the wettability reversal agent are added to the active agent solution in sequence, the mixture is reacted at 45°C and a stirring speed of 700 rpm for 0.5 h until the components are fully reacted to obtain a mixed stock solution.

[0135] Example 7

[0136] This embodiment provides an oil-displacing agent.

[0137] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that: (1) based on the total mass of the main surfactant, the auxiliary surfactant and water being 100%, the amount of the polymer additive is 0.5%, the amount of the stabilizer is 0.1%, and the amount of the wettability reversal agent is 1.5%; and (2) after the polymer additive, the stabilizer and the wettability reversal agent are sequentially added to the active agent solution, the mixture is reacted at 55° C. and a stirring speed of 900 rpm for 2 h until the components are fully reacted to obtain a mixed stock solution.

[0138] Example 8

[0139] This embodiment provides an oil-displacing agent.

[0140] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that: (1) during the ultrasonic treatment, the ultrasonic power is controlled to 450 W, the ultrasonic frequency is 18 kHz, and the treatment time is 25 min; (2) during the high-pressure homogenization treatment, the pressure is set to 250 bar, the treatment is performed twice, and the treatment time for each time is 1 min.

[0141] Example 9

[0142] This embodiment provides an oil-displacing agent.

[0143] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that: (1) during the ultrasonic treatment, the ultrasonic power is controlled to 550 W, the ultrasonic frequency is 25 kHz, and the treatment time is 45 min; (2) during the high-pressure homogenization treatment, the pressure is set to 350 bar, the treatment is performed 4 times, and the treatment time for each time is 2 min.

[0144] Example 10

[0145] This embodiment provides a surfactant for an oil-displacing agent and an oil-displacing agent.

[0146] The surfactant for oil displacement agent provided in this embodiment is different from the surfactant for oil displacement agent provided in Example 1 only in that: during the preparation process, (1) the mass concentration of H2SO4 in the concentrated sulfuric acid used is 95%, and (2) the mass concentration of sodium hydroxide in the sodium hydroxide solution used is 25%.

[0147] The oil-displacing agent provided in this embodiment is different from the oil-displacing agent provided in Example 1 only in that the main surfactant is the surfactant for the oil-displacing agent provided in this embodiment.

[0148] Example 11

[0149] This embodiment provides a surfactant for an oil-displacing agent and an oil-displacing agent.

[0150] The surfactant for oil displacement agent provided in this embodiment is different from the surfactant for oil displacement agent provided in Example 1 only in that: during the preparation process, (1) the mass concentration of H2SO4 in the concentrated sulfuric acid used is 98%, and (2) the mass concentration of sodium hydroxide in the sodium hydroxide solution used is 35%.

[0151] Example 12

[0152] This embodiment provides an oil-displacing agent.

[0153] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that: (1) based on the total mass of the main surfactant, the auxiliary surfactant and water being 100%, the amount of the main surfactant used is 2% and the amount of the auxiliary surfactant used is 0.5%; (2) the main surfactant and the auxiliary surfactant are dissolved in water at a temperature of 25°C and under stirring conditions to obtain an active agent solution, wherein the stirring speed is 300 rpm and the stirring time is 20 min.

[0154] Example 13

[0155] This embodiment provides an oil-displacing agent.

[0156] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that: (1) based on the total mass of the main surfactant, the auxiliary surfactant and water being 100%, the amount of the main surfactant used is 7% and the amount of the auxiliary surfactant used is 3%; (2) the main surfactant and the auxiliary surfactant are dissolved in water at a temperature of 55°C and under stirring conditions to obtain an active agent solution, wherein the stirring speed is 500 rpm and the stirring time is 40 min.

[0157] Example 14

[0158] This embodiment provides an oil-displacing agent.

[0159] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that the preparation method of the polymer auxiliary agent is different, specifically: acrylamide and the initiator ammonium persulfate are dissolved in deionized water and stirred evenly, the pH value is adjusted to 8 with sodium hydroxide, and a polymerization reaction is carried out at 50°C for 5 hours. The product after the polymerization reaction is dried and crushed to a particle size of ≤100 μm to obtain a polymer auxiliary agent; wherein the initiator accounts for 0.1% of the mass of the acrylamide, and the amount of deionized water added is 5 times the mass of the acrylamide.

[0160] Example 15

[0161] This embodiment provides an oil-displacing agent.

[0162] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that the preparation method of the polymer auxiliary agent is different, specifically: acrylamide and the initiator ammonium persulfate are dissolved in deionized water and stirred evenly, the pH value is adjusted to 9 with sodium hydroxide, and a polymerization reaction is carried out at 60°C for 6 hours. The product after the polymerization reaction is dried and crushed to a particle size of ≤100 μm to obtain a polymer auxiliary agent; wherein the initiator accounts for 2.5% of the mass of the acrylamide, and the amount of deionized water added is 10 times the mass of the acrylamide.

[0163] Example 16

[0164] This embodiment provides an oil-displacing agent.

[0165] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that the stabilizer is different. In this embodiment, the stabilizer is a block copolymer of polyoxypropylene and polyoxyethylene, and the mass content of the polyoxyethylene segment in the block copolymer of polyoxypropylene and polyoxyethylene is 20%.

[0166] Example 17

[0167] This embodiment provides an oil-displacing agent.

[0168] The oil-displacing agent provided in this embodiment differs from the oil-displacing agent provided in Example 1 only in that the stabilizer is different. In this embodiment, the stabilizer is a block copolymer of polyoxypropylene and polyoxyethylene, and the mass content of the polyoxyethylene segment in the block copolymer of polyoxypropylene and polyoxyethylene is 40%.

[0169] Comparative Example 1

[0170] This comparative example provides an oil-displacing agent.

[0171] The oil-displacing agent provided in this comparative example is different from the oil-displacing agent provided in Example 1 only in that no auxiliary surfactant is added.

[0172] Comparative Example 2

[0173] This comparative example provides a surfactant for an oil-displacing agent and an oil-displacing agent.

[0174] The surfactant for oil-displacing agent provided in this comparative example differs from the surfactant for oil-displacing agent provided in Example 1 only in that: during the preparation process, (1) alkyl alcohol and sulfuric acid are mixed in a molar ratio of 1:1.8, (2) the surfactant preparation mixture is stirred at 80°C at a stirring speed of 400 rpm for 5 hours to react, and the obtained reaction product is cooled to 55°C and then a sodium hydroxide solution with a sodium hydroxide mass concentration of 30% is added to adjust the pH value to 6.5, and (3) the mass ratio of sodium chloride to the product after pH adjustment is 3:1.

[0175] The oil-displacing agent provided in this embodiment is different from the oil-displacing agent provided in Example 1 only in that the main surfactant is the surfactant for the oil-displacing agent provided in this embodiment.

[0176] Comparative Example 3

[0177] This comparative example provides an oil-displacing agent.

[0178] The oil-displacing agent provided in this comparative example is different from the oil-displacing agent provided in Example 1, except that the preparation method of the auxiliary surfactant is different, specifically: dodecyldimethyl tertiary amine is added to the reactor, hydrogen chloride gas is introduced under the condition of maintaining the temperature at 70°C, the temperature is controlled to 75°C and the reaction is carried out under stirring conditions (stirring speed is 450 rpm) for 6 hours until the reaction is complete; the excess hydrogen chloride is neutralized with a sodium hydroxide solution having a sodium hydroxide mass concentration of 30%, the product is purified by a reduced pressure distillation method, the quaternary ammonium salt is separated, and the quaternary ammonium salt is dried to constant weight to obtain an auxiliary surfactant.

[0179] Comparative Example 4

[0180] This comparative example provides an oil-displacing agent.

[0181] The oil-displacing agent provided in this comparative example differs from the oil-displacing agent provided in Example 1 only in that: (1) based on the total mass of the main surfactant, the auxiliary surfactant and water being 100%, the amount of the polymer additive used is 1%, the amount of the stabilizer used is 0.5%, and the amount of the wettability reversal agent used is 2%; (2) after the polymer additive, the stabilizer and the wettability reversal agent are added to the active agent solution in sequence, the mixture is reacted at 65° C. and a stirring speed of 950 rpm for 3 h until the components are fully reacted to obtain a mixed stock solution.

[0182] Comparative Example 5

[0183] This comparative example provides a surfactant for an oil-displacing agent and an oil-displacing agent.

[0184] The surfactant for oil displacement agent provided in this comparative example is different from the surfactant for oil displacement agent provided in Example 1 in that: during the preparation process, the alkyl alcohol material is selected from the crude oil of conventional oil reservoir B (temperature 45°C, total salinity 30,000 ppm, non-high salinity / high temperature oil reservoir) with a carbon atom number of C 14 Straight-chain hydrocarbon skeleton alkyl alcohol material.

[0185] The oil-displacing agent provided in this comparative example is different from the oil-displacing agent provided in Example 1 only in that the main surfactant is the surfactant for the oil-displacing agent provided in this comparative example.

[0186] In order to explore the performance of the oil-displacing agents of Examples 1 to 17 and Comparative Examples 1 to 5, the oil-displacing agents provided in the examples were respectively taken as experimental samples of oil-displacing agents for testing. Each experimental sample of the oil-displacing agent was placed in an environment simulating the conditions of reservoir A (temperature 85°C, salinity 100,000 ppm, pressure 10 MPa) for aging test for 72 hours. After the test, the oil-water interfacial tension was detected using an interfacial tension meter. At the same time, a core flooding experiment of reservoir A was carried out to verify its oil displacement efficiency under high salinity and high temperature conditions. The oil displacement experiment used produced oil from reservoir A as the experimental crude oil.

[0187] 1. To explore the influence of the preparation process parameters of the main surfactant (i.e., the surfactant used for oil displacement) on the oil displacement performance:

[0188] As shown in Table 1, a comparison of Examples 1 to 3 shows that the interfacial tension of each Example is lower than 0.003 mN / m, meeting the requirements of a low-tension oil-displacing agent. The oil displacement efficiency of Example 1 reaches a maximum of 81.2%, while the oil displacement efficiencies of Examples 2 and 3 are 79.3% and 79.6%, respectively. This indicates that controlling parameters such as the molar ratio of alkyl alcohol to sulfuric acid and temperature during the preparation of the primary surfactant has a certain influence on the oil displacement performance.

[0189] Compared with Comparative Example 2, it can be seen that: although the interfacial tension of Comparative Example 2 is similar to that of Examples 1 to 3, which is 0.0026 mN / m, the oil displacement efficiency of Comparative Example 2 is much lower than that of Examples 1 to 3, which is only 72.8%. It can be seen that Comparative Example 2 uses process parameters (molar ratio of alkyl alcohol to sulfuric acid and temperature) that are out of range, which is not conducive to the preparation of high-efficiency main surfactants.

[0190] Table 1

[0191] Grouping Interfacial tension (mN / m) Oil displacement efficiency (%) Example 1 0.0021 81.2 Example 2 0.0025 79.3 Example 3 0.0023 79.6 Comparative Example 2 0.0026 72.8 Example 8 0.0023 79.5 Example 9 0.0020 82.1 Example 10 0.0025 78.9 Example 11 0.0022 80.7 Example 12 0.0028 76.3 Example 13 0.0024 80.9 Example 14 0.0026 78.1 Example 15 0.0029 77.5 Example 16 0.0027 79.0 Example 17 0.0025 80.4

[0192] 2. Investigate the effect of auxiliary surfactants on the performance of oil displacement agents:

[0193] As shown in Table 2, by comparing Example 4 and Example 5, it can be seen that the interfacial tensions of Example 4 and Example 5 are 0.0023 mN / m and 0.0024 mN / m, respectively, both lower than 0.003 mN / m, meeting the requirements of a low-tension oil displacement agent. The oil displacement efficiency of Example 5 is slightly higher than that of Example 4.

[0194] Compared with Comparative Example 1 and Comparative Example 3, it can be seen that the interfacial tension of Comparative Example 1 and Comparative Example 3 is higher than that of Example 4 and Example 5, which are 0.0033 mN / m and 0.0031 mN / m, respectively. It can be seen that the addition of auxiliary surfactant has a significant effect on reducing the interfacial tension; the oil displacement efficiency of Comparative Example 3 is 75.8%, which is lower than that of Example 4 and Example 5. It can be seen that the auxiliary surfactant not only affects the interfacial tension, but also has a direct impact on the oil displacement efficiency. Comparative Example 3 uses process parameters out of the range, and the improvement effect of the oil displacement agent performance is poor compared with Examples 4 and 5.

[0195] Table 2

[0196]

[0197]

[0198] 3. Investigate the influence of process parameters for preparing mixed stock solution on the performance of oil displacement agent:

[0199] As shown in Table 3, by comparing Example 6 and Example 7, it can be seen that the interfacial tensions of Example 6 and Example 7 are 0.0026 mN / m and 0.0024 mN / m, respectively, both lower than 0.003 mN / m, meeting the requirements of a low-tension oil-displacing agent; the oil displacement efficiency of Example 7 is higher than that of Example 6, at 80.2% versus 79.4%. It can be seen that the optimization of parameters such as the distribution ratio of each component in the mixed stock solution and the stirring conditions can improve the oil displacement efficiency of the oil-displacing agent;

[0200] Compared with Comparative Example 4, it can be seen that the interfacial tension of Comparative Example 4 is 0.0029 mN / m, which is higher than that of Example 6 and Comparative Example 7, indicating that the preparation conditions of the mixed stock solution have a significant effect on the interfacial tension; the oil displacement efficiency of Comparative Example 4 is 77.5%, which is lower than that of Example 6 and Example 7; Comparative Example 4 uses process parameters out of the range, which is not conducive to improving the performance of the oil displacement agent; it can be seen that the preparation process parameters of the mixed stock solution, such as component ratio, temperature, etc., have a certain influence on the overall oil displacement efficiency of the oil displacement agent.

[0201] Table 3

[0202] Grouping Interfacial tension (mN / m) Oil displacement efficiency (%) Example 6 0.0026 79.4 Example 7 0.0024 80.2 Comparative Example 4 0.0029 77.5

[0203] 4. Investigate the effect of alkyl alcohol materials on oil displacement performance:

[0204] As shown in Table 4, by comparing Example 1 with Comparative Example 5, it can be seen that compared with Example 1 using C from the target reservoir, 14 The oil displacement agent prepared by alkyl alcohol is prepared by using surfactant to prepare the oil displacement agent. In Comparative Example 5, C 14 The oil displacement performance of the oil displacement agent prepared by alkyl alcohol and configured with a surfactant has obvious deficiencies: (1) the interfacial tension increases, and the molecular structure is unstable under high temperature and high salinity conditions, resulting in an increase in interfacial tension (>0.004mN / m); (2) the oil displacement efficiency decreases: the wetting control ability is insufficient, and it cannot effectively adapt to the target reservoir conditions. The oil displacement efficiency decreases by 12.9% compared with Example 1.

[0205] Table 4

[0206] Grouping Interfacial tension (mN / m) Oil displacement efficiency (%) Example 1 0.0021 81.2 Comparative Example 5 0.0048 68.3

[0207] 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a surfactant for an oil-displacing agent, wherein: The preparation method comprises: The alkyl alcohol material is mixed with concentrated sulfuric acid to obtain a mixture for preparing a surfactant; wherein the alkyl alcohol material is selected from crude oil with carbon atoms of C 2 separated from the target oil reservoir for the target oil displacement surfactant. 10 -C 18 The carbon number of the alkyl alcohol material or the crude oil separated from the high mineralization and high temperature oil reservoir is C 10 -C 18 wherein the mass concentration of H2SO4 in the concentrated sulfuric acid is not less than 95%; the molar ratio of hydroxyl groups in the alkyl alcohol material to H2SO4 in the concentrated sulfuric acid is 1:1-1.8; high mineralization refers to a total mineralization of ≥50,000 ppm, and high temperature refers to a formation temperature of ≥90°C; The surfactant preparation mixture is reacted at 55-75° C., the obtained reaction product is cooled to 40-55° C., hydroxide is added to adjust the pH value to 6.8-7.2, and salt is added to the pH-adjusted product for salting out and purification, thereby preparing the target oil displacement agent surfactant; Preferably, the alkyl alcohol material is selected from the crude oil of the target oil displacement agent surfactant target use oil reservoir with carbon atoms of C 10 -C 18 alkyl alcohol material; more preferably, the target oil reservoir is a high salinity, high temperature oil reservoir.

2. The preparation method according to claim 1, wherein The molar ratio of hydroxyl groups in the alkyl alcohol material to H2SO4 in the concentrated sulfuric acid is 1:1-1.5; preferably, the molar ratio of hydroxyl groups in the alkyl alcohol material to H2SO4 in the concentrated sulfuric acid is 1:1-1.2; and / or reacting the surfactant preparation mixture at 60-70° C.; and / or The obtained reaction product is cooled to 45-50° C. and then hydroxide is added to adjust the pH value to 6.8-7.2; and / or In the process of adding salt to the product after pH adjustment for salting out and purification, the mass ratio of the amount of salt added to the product after pH adjustment is 1.5-2:

1.

3. The preparation method according to claim 1, wherein The number of carbon atoms separated from crude oil is C 10 -C 18 The alkyl alcohol material is a purified product of a fraction with a distillation range of 200-350°C obtained by atmospheric distillation of crude oil; preferably, the purification comprises solvent extraction and crystallization; more preferably, a polar solvent such as methanol and / or ethanol is used in the solvent extraction; more preferably, the volume ratio of the solvent used in the solvent extraction process to the fraction is 1:1-2; more preferably, the crystallization is performed by a low-temperature crystallization method at 0-5°C; and / or The salt added in the salting-out purification comprises at least one of chloride, nitrate, and sulfate; preferably, the salt added in the salting-out purification comprises at least one of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, and potassium sulfate; more preferably, the salt added in the salting-out purification is sodium chloride; and / or The hydroxide comprises at least one of sodium hydroxide and potassium hydroxide; preferably, the hydroxide is sodium hydroxide, and the sodium hydroxide is added in the form of a sodium hydroxide solution; wherein, based on the total mass of the sodium hydroxide solution being 100%, the concentration of the sodium hydroxide in the sodium hydroxide solution is 25-35%.

4. A surfactant for an oil-displacing agent, which can be prepared by the preparation method of a surfactant for an oil-displacing agent according to any one of claims 1 to 3.

5. Use of the surfactant for oil displacement agent according to claim 4 as an oil displacement agent component in oil reservoir development; wherein, The oil reservoir is the source of the alkyl alcohol material, which is the raw material for preparing the surfactant for the oil displacement agent.

6. A method for preparing an oil-displacing agent, wherein: The preparation method comprises: Mixing a primary surfactant, a secondary surfactant, a polymer additive, a stabilizer, a wettability reversal agent and water to obtain a mixed stock solution; The mixed stock solution is subjected to ultrasonic treatment and high-pressure homogenization treatment in sequence to obtain an oil-displacing agent; The main surfactant is the surfactant for oil displacement provided by the second aspect of the present invention; the auxiliary surfactant is a quaternary ammonium salt; the polymer auxiliary agent is polyacrylamide; the stabilizer is a block copolymer of polyoxypropylene and polyoxyethylene; the wettability reversal agent is a mixture of alkyltrimethylammonium bromide, fluorinated surfactant and fatty acid in a mass ratio of 3-4:0.8-1.5:1; Wherein, based on the total mass of the main surfactant, the auxiliary surfactant and water as 100%, the amount of the main surfactant is 2-7%, the amount of the auxiliary surfactant is 0.5-3%, the amount of the polymer additive is 0.1-0.5%, the amount of the stabilizer is 0.05-0.1%, and the amount of the wettability reversal agent is 0.5-1.5%; Preferably, the mixing of the main surfactant, the auxiliary surfactant, the polymer auxiliary agent, the stabilizer, the wettability reversal agent and the water comprises: dissolving the main surfactant and the auxiliary surfactant in the water to obtain an active agent solution; then sequentially adding a polymer auxiliary agent, a stabilizer and a wettability reversal agent to the active agent solution, and mixing the active agent solution, the polymer auxiliary agent, the stabilizer and the wettability reversal agent, thereby achieving mixing of the main surfactant, the auxiliary surfactant, the polymer auxiliary agent, the stabilizer, the wettability reversal agent and the water; more preferably, dissolving the main surfactant and the auxiliary surfactant in the water at 25-55° C.; more preferably, mixing the active agent solution, the polymer auxiliary agent, the stabilizer and the wettability reversal agent is carried out at 45-55° C.

7. The preparation method according to claim 6, wherein The method includes: The quaternary ammonium salt includes at least one of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, didodecyldimethylammonium chloride and benzyltrimethylammonium chloride; preferably, the quaternary ammonium salt can be prepared by the following preparation method: hydrogen chloride gas is introduced into dodecyldimethyl tertiary amine at 50-60° C., and then the reaction is carried out at 45-65° C., and then the excess hydrogen chloride in the obtained reaction product is neutralized, and then the product is purified by vacuum distillation or solvent extraction, and then the quaternary ammonium salt is separated and dried, thereby completing the preparation of the quaternary ammonium salt; more preferably, the excess hydrogen chloride in the obtained reaction product is neutralized using at least one of sodium hydroxide, potassium hydroxide, sodium carbonate and triethylamine; and / or The polymer auxiliary agent can be prepared by the following preparation method: mixing acrylamide, an initiator and water to obtain a mixture to be polymerized; adjusting the pH value of the mixture to be polymerized to 8-9, and then performing a polymerization reaction at a temperature of 50-60°C; drying and crushing the polymerization reaction to obtain the polymer auxiliary agent; wherein the mass of the initiator is 0.1-2.5% of the mass of the acrylamide, and the mass of the water is 5-10 times the mass of the acrylamide; preferably, the initiator includes at least one of ammonium persulfate, potassium persulfate and azobisisobutyronitrile; preferably, the pH value of the mixture to be polymerized is adjusted using at least one of sodium hydroxide, sodium carbonate and ammonia water; preferably, the crushing is to crush to no more than 100 μm; and / or The mass content of the polyoxyethylene segment in the block copolymer of polyoxypropylene and polyoxyethylene is 20-40%; and / or The fluorosurfactant comprises at least one of potassium perfluorooctane sulfonate, perfluorononanoic acid and perfluoropolyether; and / or The fatty acid includes at least one of lauric acid, stearic acid, oleic acid, and isostearic acid.

8. The preparation method according to claim 6, wherein During the ultrasonic treatment, the ultrasonic power is 450-550W and the ultrasonic frequency is 18-25kHz; preferably, the ultrasonic treatment time is 25-45min; and / or During the high-pressure homogenization process, the pressure is 250-350 bar; preferably, during the high-pressure homogenization process, the number of treatments is 2-4 times, and each treatment time is 1-2 minutes.

9. An oil-displacing agent, which can be prepared by the method for preparing an oil-displacing agent according to any one of claims 6 to 8.

10. Use of the oil displacement agent according to claim 9 in oil reservoir development; wherein, The oil reservoir is the source oil reservoir of the alkyl alcohol material which is the raw material for preparing the main surfactant in the oil displacement agent.

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