Gemini-Type Isoalkyl Sulfobetaine Oil Displacement Agent and Preparation Method

Abstract

The present invention discloses a Gemini - type isomeric alkyl sulfobetaine oil displacement agent and its preparation method. Using alcohol and deionized water as a mixed solvent, sodium 2,3 - dibromo - 1,4 - butanedisulfonate is added. After stirring and dissolving, long - chain isomeric alkyl dimethyl tertiary amine is added, and a homogeneous liquid is obtained after reaction. The liquid is subjected to vacuum distillation to obtain a solid crude product, which is washed and dried to obtain Gemini - type isomeric alkyl sulfobetaine. Finally, the following components are weighed by mass percentage: 20% - 25% of Gemini - type isomeric alkyl sulfobetaine, 74.84% - 79.92% of deionized water. After stirring and dissolving, 0.12% - 0.24% of polyacrylamide is added and stirred until completely dissolved to obtain the Gemini - type isomeric alkyl sulfobetaine oil displacement agent. This product can not only effectively reduce the oil - water interfacial tension, but also significantly reduce the contact angle of water on the rock surface in the water - oil - rock system, greatly improving the recovery rate of crude oil.

Description

Technical Field

[0001] The present invention belongs to the technical field of tertiary oil recovery in oilfield development, and specifically relates to a Gemini-type isomeric alkyl sulfobetaine oil displacement agent and a preparation method thereof. Background Art

[0002] In the current situation of increasingly tense global energy, improving the recovery rate of crude oil has become a major research topic in world oil exploitation. Tertiary oil recovery is a particularly effective method for improving the recovery rate of crude oil. Tertiary oil recovery technology is a high-tech developed in China in the past decade or so. Its popularization and application have played an important role in improving the recovery rate of crude oil and stabilizing the crude oil production of old oilfields. Although there are many methods for tertiary oil recovery, surfactant flooding currently shows its obvious advantages. Among surfactant flooding, zwitterionic surfactants have outstanding advantages because the zwitterionic surfactant molecules have both anionic hydrophilic groups and cationic hydrophilic groups and show amphoteric properties. Common ones include betaine-type zwitterionic surfactants, etc. Since this kind of surfactant has a chelating effect on metal ions, most of them can be used for oil displacement in oil layers with high salinity and relatively high temperature, and can greatly reduce the chromatographic separation effect when non-ionic and anionic surfactants are compounded.

[0003] Among zwitterionic surfactants, the sulfonic acid group and the special inner salt structure in sulfobetaine determine its stable properties, with unique advantages such as resistance to high concentrations of acid, alkali, and salt, strong calcium soap dispersing power, effective reduction of the oil-water interfacial tension, good oil displacement efficiency, and excellent compatibility and synergistic effect with non-ionic and anionic surfactants. Therefore, it has become one of the research hotspots in tertiary oil recovery. At the same time, the development of new sulfobetaine surfactants provides technical support for improving the recovery rate of tertiary oil recovery. Summary of the Invention

[0004] The purpose of the present invention is to provide a Gemini-type isomeric alkyl sulfobetaine oil displacement agent, which solves the chromatographic separation problem of the existing ternary composite oil displacement agent, can effectively reduce the oil-water interfacial tension, and can also significantly reduce the contact angle of water on the rock surface in the water-oil-rock system.

[0005] Another purpose of the present invention is to provide a preparation method of the Gemini-type isomeric alkyl sulfobetaine oil displacement agent.

[0006] The first technical solution adopted by the present invention is that the Gemini-type isomeric alkyl sulfobetaine oil displacement agent is composed of the following components by mass percentage: 20% - 25% of Gemini-type isomeric alkyl sulfobetaine, 0.12% - 0.24% of polyacrylamide, and the balance is deionized water.

[0007] The features of the present invention also lie in:

[0008] Gemini-type isomeric alkyl sulfobetaine is made from the raw material 2,3-dibromo-1,4-butanedisulfonic acid sodium salt, long-chain isomeric alkyl dimethyl tertiary amine, and a mixed solvent. The mass ratio of the raw material to the mixed solvent is 1:1. The mixed solvent is deionized water and alcohol with a mass ratio of 1:1 to 1:3.

[0009] The long-chain isomeric alkyl dimethyl tertiary amine is one or more of isomeric dodecane, isomeric tetradecane, isomeric hexadecane, and isomeric octadecane dimethyl tertiary amine.

[0010] The alcohol is one or more of ethanol, propanol, and isopropanol

[0011] Another technical solution adopted by the present invention is: the preparation method of the above-mentioned Gemini-type isomeric alkyl sulfobetaine oil displacement agent, and the specific steps are as follows:

[0012] Step 1: In the initial reaction system during the synthesis of Gemini-type isomeric alkyl sulfobetaine, the mass ratio of each component is: the mass ratio of the raw material 2,3-dibromo-1,4-butanedisulfonic acid sodium salt to the long-chain isomeric alkyl dimethyl tertiary amine is 1:1.275 to 1:1.518; the mass ratio of deionized water to alcohol as the mixed solvent is 1:1 to 1:3, and the mass ratio of the raw material to the mixed solvent is 1:1.

[0013] Step 2: Add 12.5% - 25% of deionized water by mass percentage to a reactor equipped with a condensing reflux device, then add 25% - 37.5% of alcohol, start stirring, then add 19.9% - 24.7% of 2,3-dibromo-1,4-butanedisulfonic acid sodium salt and stir until completely dissolved, and finally add 25.3% - 30.1% of long-chain isomeric alkyl dimethyl tertiary amine. The sum of the mass percentages of the above components is 100%. After the feeding is completed, quickly raise the temperature to 85°C - 90°C to start the reaction, and maintain the temperature between 85°C - 90°C for constant temperature reaction for 6 - 8 hours to obtain a solution of Gemini-type isomeric alkyl sulfobetaine. After the reaction is completed, naturally cool it.

[0014] Step 3: Transfer all the solution of Gemini-type isomeric alkyl sulfobetaine in Step 2 to a rotary evaporator, and carry out vacuum distillation to obtain a mixed solvent of alcohol and water and a crude product of Gemini-type isomeric alkyl sulfobetaine solid. The mixed solvent is recovered and reused. Wash the crude product with a small amount of absolute ethanol 2 - 3 times. After the solid is filtered, place it in an electrothermal constant temperature forced air drying oven and dry it at 60°C for 4 - 6 hours to obtain pure Gemini-type isomeric alkyl sulfobetaine.

[0015] The synthesis chemical formula of Gemini-type isomeric alkyl sulfobetaine is as follows:

[0016]

[0017] Step 4: Weigh the following components by mass percentage: 20% - 25% of the pure Gemini - type isomeric alkyl sulfobetaine obtained in Step 3, 0.12% - 0.24% of polyacrylamide, and the balance is deionized water. The sum of the mass percentages of the above - mentioned components is 100%.

[0018] Step 5: First, add the pure Gemini - type isomeric alkyl sulfobetaine to deionized water according to the ratio in Step 4 and stir until completely dissolved.

[0019] Step 6: Then add polyacrylamide and stir rapidly until completely dissolved to obtain the Gemini - type isomeric alkyl sulfobetaine oil - displacement agent.

[0020] The characteristics of the present invention also lie in that

[0021] The long - chain isomeric alkyl dimethyl tertiary amine in Step 1 is one or more of isomeric dodecane, isomeric tetradecane, isomeric hexadecane, and isomeric octadecane dimethyl tertiary amine;

[0022] The alcohol in Step 1 is one or more of ethanol, propanol, and isopropanol;

[0023] The stirring speed in Step 2 and Step 5 is 150 r / min;

[0024] The stirring speed in Step 6 is 500 r / min.

[0025] The key innovation point of this application lies in:

[0026] The oil - displacement agent product of this application is a betaine - type amphoteric surfactant. In its molecule, the lipophilic group end is composed of isomeric alkyl groups, and the hydrophilic group end has both cations and anions. The positive charge center of the cation is carried on the quaternary ammonium N atom, while the negative charge center of the anion is carried on the negatively charged sulfonic acid group, forming an inner salt structure composed of cations and anions inside the oil - displacement agent molecule. Therefore, this molecule has both the properties of cationic surfactants and anionic surfactants.

[0027] First, due to the presence of the cationic quaternary ammonium nitrogen at the hydrophilic end of the molecule, it has a certain adsorption property on the negatively charged rock surface. Through the interaction between the positive charge carried by the cation and the rock surface, it adsorbs on the negatively charged rock surface, forming a hydrophobic adsorption layer with the lipophilic group facing outward. This can increase the oil-phase permeability, reduce the water-phase permeability, cause the residual oil in the pore wall to aggregate and detach from the rock surface, change its wettability, and play a role in selective water plugging. Through mass transfer and diffusion between the oil and water phases, it can not only reduce the oil-water interfacial tension but also improve the wettability of the liquid-solid interface through adsorption, causing the formation rock surface to change from lipophilic to hydrophilic, thereby reducing the contact angle between the rock surface and water.

[0028] Secondly, selecting an isomeric alkyl group with 12 to 18 carbon atoms at the lipophilic end of the molecule ensures its good lipophilic property. By choosing the lipophilic and hydrophilic groups of the surfactant molecule, it is ensured that the oil displacement agent reaches a balance between lipophilicity and hydrophilicity in the aqueous solution, thereby improving its surface activity.

[0029] Finally, because an internal salt structure composed of cations and anions is formed inside the surfactant molecule, its greatest feature is that it is easily soluble in water whether in acidic, neutral or alkaline conditions, and there is no precipitation even at the isoelectric point. Therefore, it has a wide applicable pH range, and at the same time its salt tolerance ability is also significantly enhanced.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. The chromatographic separation phenomenon of the composite ternary oil displacement agent in the formation is successfully avoided.

[0032] 2. Due to the presence of sulfonic acid groups and a special internal salt structure in the surfactant molecule of this product, its salt tolerance ability is significantly enhanced compared with traditional oil displacement agents.

[0033] 3. By blocking the high-permeability layer with polyacrylamide, allowing water flooding to enter the low-permeability layer and then continuing the displacement, the swept volume of water flooding is greatly increased, the contact area between the oil displacement agent and the crude oil is increased, and the oil displacement efficiency is improved.

[0034] 4. This product can change the wettability of the rock surface from lipophilic to hydrophilic, and can significantly reduce the contact angle of water on the rock surface in the water-oil-rock system.

[0035] 5. The reduction of the oil-water interfacial tension is also obvious, and it can be effectively stabilized at 10 -3 mN / m or even lower. Specific embodiments

[0036] The present invention will be described in detail below in conjunction with specific embodiments.

[0037] Example 1

[0038] Step 1: In the synthesis of Gemini-type isomeric alkyl sulfobetaine, the mass ratio of each component in the initial reaction system is as follows: the mass ratio of the raw material 2,3-dibromo-1,4-butanedisulfonate sodium to the long-chain isomeric alkyl dimethyl tertiary amine is 1:1.275 to 1:1.518; the mass ratio of deionized water to alcohol as the mixed solvent is 1:1 to 1:3, and the mass ratio of the raw material to the mixed solvent is 1:1.

[0039] Step 2: Add 12.5% of deionized water and then 37.5% of alcohol by mass percentage to a reactor equipped with a condensing reflux device. Start stirring, then add 19.9% of 2,3-dibromo-1,4-butanedisulfonate sodium and stir until completely dissolved. Finally, add 30.1% of the long-chain isomeric alkyl dimethyl tertiary amine. After the feeding is completed, quickly raise the temperature to 85°C to start the reaction, and maintain the temperature at 85°C for a constant reaction for 6 hours to obtain a solution of Gemini-type isomeric alkyl sulfobetaine. After the reaction is completed, let it cool naturally.

[0040] Step 3: Transfer all the solution of Gemini-type isomeric alkyl sulfobetaine in Step 2 to a rotary evaporator, and carry out vacuum distillation to obtain a mixed solvent of alcohol and water and a crude product of Gemini-type isomeric alkyl sulfobetaine solid. The mixed solvent is recycled and reused. Wash the crude product with a small amount of absolute ethanol 2 - 3 times. After filtration, place the solid in an electrothermal constant temperature blast drying oven and dry it at 60°C for 4 hours to obtain pure Gemini-type isomeric alkyl sulfobetaine.

[0041] Step 4: Weigh the following components by mass percentage: 20% of the pure Gemini-type isomeric alkyl sulfobetaine obtained in Step 3, 0.12% of polyacrylamide, and the balance is deionized water. The sum of the mass percentages of the above components is 100%.

[0042] Step 5: Add the pure Gemini-type isomeric alkyl sulfobetaine to deionized water according to the ratio in Step 4 and stir until completely dissolved.

[0043] Step 6: Then add polyacrylamide and stir quickly until completely dissolved to obtain a novel Gemini-type isomeric alkyl sulfobetaine oil displacement agent.

[0044] Example 2

[0045] Step 1: In the synthesis of Gemini-type isomeric alkyl sulfobetaine, the mass ratio of each component in the initial reaction system is as follows: the mass ratio of the raw material 2,3-dibromo-1,4-butanedisulfonate sodium to the long-chain isomeric alkyl dimethyl tertiary amine is 1:1.275 to 1:1.518; the mass ratio of deionized water to alcohol as the mixed solvent is 1:1 to 1:3, and the mass ratio of the raw material to the mixed solvent is 1:1.

[0046] Step 2: Add 25% deionized water and then 25% alcohol by mass percentage to a reactor equipped with a condensing reflux device. Start stirring, then add 24.7% of 2,3-dibromo-1,4-butanedisulfonic acid sodium salt and stir until completely dissolved. Finally, add 25.3% of long-chain isomeric alkyl dimethyl tertiary amine. After the feeding is completed, quickly raise the temperature to 90 °C to start the reaction, and maintain the temperature at 90 °C for constant-temperature reaction for 8 hours to obtain a solution of Gemini-type isomeric alkyl sulfobetaine. After the reaction is completed, let it cool naturally.

[0047] Step 3: Transfer all the solution of Gemini-type isomeric alkyl sulfobetaine in Step 2 to a rotary evaporator, and carry out vacuum distillation to obtain a mixed solvent of alcohol and water and a crude product of Gemini-type isomeric alkyl sulfobetaine solid. The mixed solvent is recycled. Wash the crude product with a small amount of absolute ethanol 2 - 3 times. After the solid is filtered, place it in an electrothermal constant-temperature blast drying oven and dry it at 60 °C for 4 - 6 h under constant temperature to obtain pure Gemini-type isomeric alkyl sulfobetaine.

[0048] Step 4: Weigh the following components by mass percentage: 25% of the pure Gemini-type isomeric alkyl sulfobetaine obtained in Step 3, 0.24% of polyacrylamide, and the balance is deionized water. The sum of the mass percentages of the above components is 100%.

[0049] Step 5: Add the pure Gemini-type isomeric alkyl sulfobetaine to deionized water according to the ratio in Step 4 and stir until completely dissolved.

[0050] Step 6: Then add polyacrylamide and stir quickly until completely dissolved to obtain a novel Gemini-type isomeric alkyl sulfobetaine oil displacement agent.

[0051] Example 3

[0052] Step 1: In the initial reaction system for the synthesis of Gemini-type isomeric alkyl sulfobetaine, the mass ratio of each component is as follows: the mass ratio of the raw material 2,3-dibromo-1,4-butanedisulfonic acid sodium salt to long-chain isomeric alkyl dimethyl tertiary amine is 1:1.275 - 1:1.518; the mass ratio of deionized water to alcohol as the mixed solvent is 1:1 - 1:3, and the mass ratio of the raw material to the mixed solvent is 1:1.

[0053] Step 2: Add 17% deionized water and then 33% alcohol by mass percentage to a reactor equipped with a condensing reflux device. Start stirring, then add 21.1% of 2,3-dibromo-1,4-butanedisulfonic acid sodium salt and stir until completely dissolved. Finally, add 28.9% of long-chain isomeric alkyl dimethyl tertiary amine. After the feeding is completed, quickly raise the temperature to 87 °C to start the reaction, and maintain the temperature at 87 °C for constant-temperature reaction for 7 hours to obtain a solution of Gemini-type isomeric alkyl sulfobetaine. After the reaction is completed, let it cool naturally.

[0054] Step 3: Transfer all the solution of Gemini-type isomeric alkyl sulfobetaine in Step 2 to a rotary evaporator, and perform vacuum distillation to obtain a mixed solvent of alcohol and water and a crude product of Gemini-type isomeric alkyl sulfobetaine solid. The mixed solvent is recycled and reused. Wash the crude product with a small amount of absolute ethanol 2 - 3 times. After filtration, place the solid in an electrothermal constant temperature blast drying oven and dry it at a constant temperature of 60°C for 4 - 6 hours to obtain pure Gemini-type isomeric alkyl sulfobetaine.

[0055] Step 4: Weigh the following components by mass percentage: 22% of the pure Gemini-type isomeric alkyl sulfobetaine obtained in Step 3, 0.18% of polyacrylamide, and the balance is deionized water. The sum of the mass percentages of the above components is 100%.

[0056] Step 5: First, add the pure Gemini-type isomeric alkyl sulfobetaine to deionized water according to the ratio in Step 4 and stir until completely dissolved.

[0057] Step 6: Then add polyacrylamide and stir rapidly until completely dissolved to obtain a novel Gemini-type isomeric alkyl sulfobetaine oil displacement agent.

[0058] Example 4

[0059] Step 1: In the initial reaction system for the synthesis of Gemini-type isomeric alkyl sulfobetaine, the mass ratio of each component is as follows: the mass ratio of the raw materials 2,3-dibromo-1,4-butanesulfonate sodium to long-chain isomeric alkyl dimethyl tertiary amine is 1:1.275 - 1:1.518; the mass ratio of deionized water to alcohol as the mixed solvent is 1:1 - 1:3, and the mass ratio of the raw materials to the mixed solvent is 1:1.

[0060] Step 2: Add 22% of deionized water to a reactor equipped with a condensation reflux device by mass percentage, then add 28% of alcohol, start stirring, then add 23.5% of 2,3-dibromo-1,4-butanesulfonate sodium and stir until completely dissolved. Finally, add 26.5% of long-chain isomeric alkyl dimethyl tertiary amine. After the feeding is completed, quickly raise the temperature to 85°C to start the reaction, and maintain the temperature at 85°C for a constant reaction for 6 hours to obtain a solution of Gemini-type isomeric alkyl sulfobetaine. After the reaction is completed, let it cool naturally.

[0061] Step 3: Transfer all the solution of Gemini-type isomeric alkyl sulfobetaine in Step 2 to a rotary evaporator, and conduct vacuum distillation to obtain a mixed solvent of alcohol and water and a crude product of Gemini-type isomeric alkyl sulfobetaine solid. The mixed solvent is recycled. Wash the crude product with a small amount of absolute ethanol 2 - 3 times. After filtration, place the solid in an electrothermal constant temperature forced air drying oven and dry it at a constant temperature of 60°C for 5 hours to obtain pure Gemini-type isomeric alkyl sulfobetaine.

[0062] Step 4: Weigh the following components by mass percentage: 24% of the pure Gemini-type isomeric alkyl sulfobetaine obtained in Step 3, 0.22% of polyacrylamide, and the balance is deionized water. The sum of the mass percentages of the above components is 100%.

[0063] Step 5: First, add the pure Gemini-type isomeric alkyl sulfobetaine to deionized water according to the ratio in Step 4 and stir until completely dissolved.

[0064] Step 6: Then add polyacrylamide and stir rapidly until completely dissolved to obtain a novel Gemini-type isomeric alkyl sulfobetaine oil displacement agent.

[0065] Example 5

[0066] Step 1: In the initial reaction system during the synthesis of Gemini-type isomeric alkyl sulfobetaine, the mass ratio of each component is as follows: the mass ratio of the raw materials 2,3-dibromo-1,4-butanesulfonate sodium to long-chain isomeric alkyl dimethyl tertiary amine is 1:1.275 - 1:1.518; the mass ratio of deionized water to alcohol as the mixed solvent is 1:1 - 1:3, and the mass ratio of the raw materials to the mixed solvent is 1:1.

[0067] Step 2: Add 22.5% of deionized water to the reactor equipped with a condensing reflux device by mass percentage, then add 27.5% of alcohol, start stirring, then add 22.1% of 2,3-dibromo-1,4-butanesulfonate sodium and stir until completely dissolved. Finally, add 27.9% of long-chain isomeric alkyl dimethyl tertiary amine. After the feeding is completed, quickly raise the temperature to 90°C to start the reaction, and maintain the temperature at 90°C for constant temperature reaction for 8 hours to obtain a solution of Gemini-type isomeric alkyl sulfobetaine. After the reaction ends, cool it naturally.

[0068] Step 3: Transfer all the solution of Gemini-type isomeric alkyl sulfobetaine in Step 2 to a rotary evaporator, and conduct vacuum distillation to obtain a mixed solvent of alcohol and water and a crude product of Gemini-type isomeric alkyl sulfobetaine solid. The mixed solvent is recycled. Wash the crude product with a small amount of absolute ethanol 2 - 3 times. After filtration, place the solid in an electrothermal constant temperature forced air drying oven and dry it at a constant temperature of 60°C for 6 hours to obtain pure Gemini-type isomeric alkyl sulfobetaine.

[0069] Step 4: Weigh the following components by mass percentage: 21% of the pure Gemini-type isomeric alkyl sulfobetaine obtained in Step 3, 0.12% of polyacrylamide, and the balance is deionized water. The sum of the mass percentages of the above components is 100%.

[0070] Step 5: First, add the pure Gemini-type isomeric alkyl sulfobetaine to deionized water according to the ratio in Step 4 and stir until completely dissolved.

[0071] Step 6: Then add polyacrylamide and stir rapidly until completely dissolved to obtain a novel Gemini-type isomeric alkyl sulfobetaine oil displacement agent.

[0072] According to the relationship among the adhesion work of oil, contact angle, and oil-water interfacial tension during the oil production process:

[0073] W = σ(1 - cosθ)

[0074] Where:

[0075] W--is the adhesion work of oil on the rock surface in the water-oil-rock system, mJ·m -2

[0076] σ--is the oil-water interfacial tension, mN / m

[0077] θ--is the contact angle of water on the rock surface in the water-oil-rock system, °

[0078] During the water flooding process, washing the oil is equivalent to pulling the oil away from the rock surface. Therefore, the smaller the adhesion work, the more beneficial it is for washing the oil. It can be seen from the above formula that the smaller the oil-water interfacial tension, the smaller the adhesion work, and the better the oil washing efficiency; the smaller the contact angle, that is, the more hydrophilic the rock, the smaller the adhesion work, and the easier the oil is to be washed off. Therefore, there are two ways to reduce the adhesion work. One is to reduce the oil-water interfacial tension, and the other is to reduce the contact angle of water. It can be seen from Table 1 that the product of the present invention just meets these two requirements, indicating that the product can significantly improve the oil washing efficiency during use, thereby increasing the oil recovery rate.

[0079] The results of the effect evaluation of the product performance obtained in each example are as follows:

[0080] Note: When testing the product performance, first configure the oil displacement agent obtained in the example into an oil displacement agent aqueous solution with a mass concentration of 0.5% with injection water, measure the oil-water interfacial tension at 50°C, and measure the contact angle at room temperature, and use the injection water without adding the oil displacement agent as a blank control.

[0081] Table 1. Effects of the aqueous solutions of the products in the examples and injection water on wettability, interfacial tension, and adhesion work

[0082]

[0083] According to the data in the table, it shows that the product can effectively reduce the oil-water interfacial tension to 10 -3 mN / m. At the same time, it also reduces the contact angle of water on the rock surface in the water-oil-rock system from 91.14° to 26.038° on average, and the adhesion work to oil is reduced by nearly 10 4 orders of magnitude.

Claims

1. Gemini - type isomeric alkyl sulfobetaine oil displacement agent, characterized in that, It consists of the following components by mass percentage: 20% - 25% of Gemini type isomeric alkyl sulfobetaine, 0.12% - 0.24% of polyacrylamide, and the balance is deionized water; The Gemini type isomeric alkyl sulfobetaine is made from the raw materials of sodium 2,3 - dibromo - 1,4 - butanedisulfonate, long - chain isomeric alkyl dimethyl tertiary amine, and a mixed solvent. The mass ratio of the raw materials to the mixed solvent is 1:1, and the mixed solvent is deionized water and alcohol with a mass ratio of 1:1 - 1:3; The long - chain isomeric alkyl dimethyl tertiary amine is one or several of isododecane, isotetradecane, isohexadecane, isooctadecane dimethyl tertiary amine; The alcohol is one or several of ethanol, propanol, isopropanol.

2. Preparation method of Gemini-type isomeric alkyl sulfobetaine oil displacement agent, characterized in that, Add alcohol and deionized water as a mixed solvent into the reactor, start stirring, then add sodium 2,3 - dibromo - 1,4 - butanedisulfonate, continue stirring until completely dissolved, and finally add long - chain isomeric alkyl dimethyl tertiary amine; after the feeding is completed, quickly raise the temperature to 85°C - 90°C. After the reaction ends, obtain a homogeneous liquid. Transfer the liquid to a rotary evaporator for vacuum distillation to obtain a crude product of Gemini type isomeric alkyl sulfobetaine solid. Wash the solid crude product with absolute ethanol, and after drying, pure Gemini type isomeric alkyl sulfobetaine can be obtained; finally, weigh the following components by mass percentage: 20% - 25% of Gemini type isomeric alkyl sulfobetaine, add it to 74.84% - 79.92% of deionized water and stir until completely dissolved, then add 0.12% - 0.24% of polyacrylamide, and continue stirring until completely dissolved to obtain a novel Gemini type isomeric alkyl sulfobetaine oil - displacement agent.

3. The preparation method of the Gemini-type isomeric alkyl sulfobetaine oil displacement agent according to claim 2, wherein, The specific steps are as follows: Step 1: In the synthesis of Gemini type isomeric alkyl sulfobetaine, the mass ratio of each component in the initial reaction system is: the mass ratio of the raw material sodium 2,3 - dibromo - 1,4 - butanedisulfonate to the long - chain isomeric alkyl dimethyl tertiary amine is 1:1.275 - 1:1.518; the mass ratio of deionized water to alcohol as the mixed solvent is 1:1 - 1:3, and the mass ratio of the raw materials to the mixed solvent is 1:1; Step 2: Add 12.5% - 25% of deionized water by mass percentage to a reactor equipped with a condensing reflux device, then add 25% - 37.5% of alcohol, start stirring, then add 19.9% - 24.7% of sodium 2,3 - dibromo - 1,4 - butanedisulfonate and stir until completely dissolved, and finally add 25.3% - 30.1% of long - chain isomeric alkyl dimethyl tertiary amine. The sum of the mass percentages of the above components is 100%. After the feeding is completed, quickly raise the temperature to 85°C - 90°C to start the reaction, and maintain the temperature between 85°C - 90°C for constant - temperature reaction for 6 - 8 hours to obtain a solution of Gemini type isomeric alkyl sulfobetaine. After the reaction ends, cool naturally; Step 3: Transfer all the solution of Gemini-type isomeric alkyl sulfobetaine in Step 2 to a rotary evaporator, and perform vacuum distillation to obtain a mixed solvent of alcohol and water and a crude product of Gemini-type isomeric alkyl sulfobetaine solid. The mixed solvent is recycled and reused. The crude product is washed 2 - 3 times with absolute ethanol. After filtration, the solid is placed in an electrothermal constant temperature blast drying oven and dried at 60°C for 4 - 6 h to obtain pure Gemini-type isomeric alkyl sulfobetaine; Step 4: Weigh the following components by mass percentage: 20% - 25% of the pure Gemini-type isomeric alkyl sulfobetaine obtained in Step 3, 0.12% - 0.24% of polyacrylamide, and the balance is deionized water. The sum of the mass percentages of the above components is 100%; Step 5: First, add the pure Gemini-type isomeric alkyl sulfobetaine to deionized water according to the ratio in Step 4 and stir until completely dissolved; Step 6: Then add polyacrylamide and stir rapidly until completely dissolved to obtain a Gemini-type isomeric alkyl sulfobetaine oil displacement agent.

4. The preparation method of the Gemini-type isomeric alkyl sulfobetaine oil displacement agent according to claim 3, characterized in that, The stirring speed in Step 2 and Step 5 is 150 r / min; the stirring speed in Step 6 is 500 r / min.

5. The preparation method of the Gemini-type isomeric alkyl sulfobetaine oil displacement agent according to claim 3, wherein, The long-chain isomeric alkyl dimethyl tertiary amine in Step 1 is one or several of isomeric dodecyl dimethyl tertiary amine, isomeric tetradecyl dimethyl tertiary amine, isomeric hexadecyl dimethyl tertiary amine, and isomeric octadecyl dimethyl tertiary amine.

6. The preparation method of the Gemini-type isomeric alkyl sulfobetaine oil displacement agent according to claim 3, characterized in that, The alcohol in Step 1 is one or several of ethanol, propanol, and isopropanol.

Images