Environment-friendly oilfield oil displacement agent and preparation method thereof

Abstract

This invention provides an environmentally friendly oilfield displacement agent and its preparation method. The displacement agent comprises the following components in parts by weight: 0.1-0.5 parts modified cellulose, 40-60 parts amphoteric surfactant, and 50-70 parts water. The displacement agent prepared by this invention exhibits low interfacial tension, high oil recovery, and good high-temperature and high-salt stability. This indicates that the invention, through the synergistic effect of the amphoteric surfactant and modified cellulose, reduces the oil-water interfacial tension, effectively improving oil washing efficiency. The introduction of sulfonic acid groups into the amphoteric surfactant and modified cellulose allows the displacement agent to maintain good performance even at high temperatures and high salinity. Furthermore, the displacement agent prepared by this invention poses no environmental residue risk and demonstrates excellent environmental performance.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development technology, and in particular relates to an environmentally friendly oilfield displacement agent and its preparation method. Background Technology

[0002] In the secondary and tertiary oil recovery stages of oilfield development, chemical enhanced oil recovery (CEM) technology is one of the core methods to improve crude oil recovery rates. Traditional CEM systems mainly rely on synthetic polymers (such as partially hydrolyzed polyacrylamide) or conventional surfactants. However, these materials typically contain aromatic rings such as benzene rings and naphthalene rings, as well as their fused ring structures, resulting in poor biodegradability, long environmental persistence, and certain ecotoxicity. This does not align with the current industry development trend of green, low-carbon, and environmental protection.

[0003] In addition, many conventional surfactants are prone to stratification and precipitation due to salting-out effects under high temperature and high salt conditions. Their molecular structure is damaged, leading to a loss of interfacial activity and an inability to effectively reduce oil-water interfacial tension. While synthetic polymers possess some thickening properties, they are highly susceptible to cross-linking and precipitation in the presence of divalent cations, resulting in a sharp loss of viscosity. Even when surfactants and polymers are combined, poor compatibility or limited synergistic mechanisms often prevent the maintenance of stable oil displacement performance under extreme conditions, leading to a significant reduction in oil displacement effectiveness.

[0004] Therefore, how to provide an environmentally friendly oil displacement agent with high oil displacement efficiency and good high-temperature and high-salt stability is a problem that this invention urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to provide an environmentally friendly oilfield displacement agent and its preparation method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides an environmentally friendly oilfield displacement agent, characterized in that the displacement agent comprises the following components in parts by weight: 0.1-0.5 parts modified cellulose, 40-50 parts amphoteric surfactant, and 50-60 parts water. The amphoteric surfactant is prepared by reacting sodium methyl lauryl sulfonate, 4-dimethylaminobutyramine, and dichloroethane.

[0007] As a further improvement, the synthesis of the amphoteric surfactant includes the following steps: (1) Add lauric acid, methanol and catalyst to a flask and stir at 60-70℃ for 3-5 h. After the reaction is complete, add organic solvent and sulfonating agent to the system and continue stirring at 70-80℃ for 0.5-1 h. Then raise the temperature to 80-90℃ and add hydrogen peroxide to mix. Then add methanol and stir at 50-60℃ for 0.5-2 h. After the reaction is complete, post-process to obtain sodium methyl laurate sulfonate. (2) Sodium methyl laurate sulfonate and 4-dimethylaminobutyramine were added to a flask and an alkaline solution was added to adjust the pH of the system to 9-10 while stirring. The reaction was carried out at 70-90℃ for 3-5 hours. After the reaction was completed, the intermediate was obtained through post-processing. (3) Add the intermediate and dichloroethane to a flask, stir and mix at 50-70℃, adjust the pH of the system to 7-8 with alkaline solution, stir and react for 5-10 hours, and after the reaction is completed, perform post-treatment to obtain the amphoteric surfactant.

[0008] This invention utilizes a specific structure of amphoteric surfactant prepared by reacting 4-dimethylaminobutyramine, sodium methyl laurate sulfonate, and dichloroethane. The molecule contains both hydrophilic sulfonate groups and hydrophobic long-chain alkyl groups, which can form a highly efficient reaction with crude oil, thereby reducing surface tension and improving degreasing effect. The amphoteric surfactant molecule contains tertiary amine groups and sulfonate groups, thus it can resist hydrolysis at high temperatures and salt precipitation in high-salt environments, exhibiting good stability.

[0009] As a further improvement, the mass of hydrogen peroxide added in step (1) is 1-3% of the mass of lauric acid added.

[0010] As a further improvement, the molar ratio of sodium methyl laurate sulfonate and 4-dimethylaminobutyramine added in step (2) is 1:1-1.5.

[0011] As a further improvement, the modified cellulose is sodium 3-chloro-2-hydroxypropanesulfonate modified cellulose.

[0012] As a further improvement, the synthesis of the modified cellulose includes the following steps: (1) Mix microcrystalline cellulose with deionized water, add hydrochloric acid dropwise under ice bath conditions, react at 70-80℃ for 1-3 hours, stop heating after the reaction is completed, add deionized water for dilution, then centrifuge at high speed, dialyze the obtained solid, freeze dry the dialyzed solid to obtain the treated cellulose. (2) Add the cellulose, ethanol and deionized water treated in step (1) into a flask, sonicate for 20-40 min, adjust the pH of the solution to 8-9 with sodium hydroxide, add sodium 3-chloro-2-hydroxypropanesulfonate, heat to 50-60℃ and react for 1-3 h. After the reaction is completed, perform post-treatment to obtain modified cellulose.

[0013] This invention improves dispersion stability by sulfonating and modifying cellulose, introducing strong hydrophilic sulfonate groups into the cellulose molecules, thus avoiding the aggregation and precipitation of cellulose in high-salt environments. In conjunction with amphoteric surfactants, the oil displacement agent can remain uniform and transparent even in high-temperature and high-salt environments.

[0014] As a further improvement, the particle size of the microcrystalline cellulose in step (1) is 40-100µm.

[0015] As a further improvement, the mass fraction of hydrochloric acid in step (1) is 20-40%, and the volume mass ratio of hydrochloric acid to microcrystalline cellulose is (1.5-2.5) mL:1g.

[0016] As a further improvement, the amount of modified cellulose added is 0.4-0.8% of the mass of the amphoteric surfactant added.

[0017] This invention also provides a method for preparing an environmentally friendly oilfield displacement agent, characterized by comprising the following steps: Add the modified cellulose to water according to the specified weight, stir and disperse at 20-40℃ to obtain a cellulose dispersion, then slowly add the amphoteric surfactant to the cellulose dispersion, continue stirring for 30-60 minutes, and then ultrasonically disperse for 15-25 minutes to obtain an environmentally friendly oilfield displacement agent.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention provides an environmentally friendly oilfield displacement agent and its preparation method. The resulting displacement agent exhibits low interfacial tension and high recovery rate, indicating that the amphoteric surfactant and modified cellulose prepared in this invention synergistically reduce the oil-water interfacial tension and possess good wetting regulation capabilities. This effectively removes residual oil films from rock pore surfaces, significantly improving microscopic oil washing efficiency. It also demonstrates good high-temperature and high-salt stability and retention rate, maintaining uniformity and transparency without stratification or precipitation even at high temperatures and high salinity. This indicates that the introduction of sulfonic acid groups into the amphoteric surfactant and modified cellulose improves dispersion stability, and their synergistic effect resists hydrolysis at high temperatures and salt precipitation in high-salt environments. Furthermore, this invention uses non-aryl sulfonates as the amphoteric surfactant, exhibiting good biodegradability and low environmental toxicity, meeting the requirements of green mining. Detailed Implementation

[0019] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0020] In the following examples, except for the amphoteric surfactant and modified cellulose, all other compound monomers and related reagents used were commercially available. Microcrystalline cellulose was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., product number C804601; lauramide propyl hydroxysulfonate betaine was purchased from Hubei Zhongnuo Yaxing Biotechnology Co., Ltd., product number LHSB-35; and carboxymethyl cellulose was purchased from Jinan Mingjiang Chemical Co., Ltd., product number 684954.

[0021] The preparation of amphoteric surfactants includes the following steps: (1) Add 20.0g lauric acid, 30mL methanol and 1.2g concentrated sulfuric acid to a flask equipped with a reflux tube, stir at 65℃ for 3.5h. After the reaction is complete, add 25mL chloroform to the system, and add 14.0g chlorosulfonic acid while stirring. React at 70℃ for 1h, then raise the temperature to 90℃ and add 0.3g hydrogen peroxide and stir to continue the reaction for 20min. Then add 2mL methanol, stir at 60℃ for 1h. After the reaction is complete, lower the temperature to 40℃ and adjust the pH of the system to 7 with sodium hydroxide solution with a mass concentration of 0.2g / mL. Then dry and pulverize the solution to obtain sodium methyl laurate sulfonate. (2) 31.6g sodium methyl laurate sulfonate and 12.2g 4-dimethylaminobutyramine were added to a flask. The pH of the system was adjusted to 9 with 40% sodium hydroxide solution under stirring. The reaction was carried out at 80°C for 5 hours. After the reaction was completed, the system was distilled under reduced pressure at 60°C and finally dried at 90°C to obtain the intermediate. (3) Add 41.4g of intermediate and 5g of dichloroethane to a flask, stir and mix at 60°C, adjust the pH of the system to 8 with 40% sodium hydroxide solution, stir and react for 9h, the reaction is completed, perform vacuum distillation at 50°C, and finally dry at 90°C to obtain amphoteric surfactant.

[0022] The preparation of modified cellulose includes the following steps: (1) Mix 5g of microcrystalline cellulose with 80mL of deionized water, add 10mL of 30% hydrochloric acid dropwise under ice bath conditions, react at 80℃ for 1.5h, stop heating after the reaction is finished, add 800mL of deionized water for dilution, then centrifuge at 10000rpm for 10min using a high-speed centrifuge, remove the supernatant, repeat the centrifugation operation 4 times, remove the supernatant after centrifugation, dialyze the obtained lower layer material with deionized water for 24h, freeze-dry the dialyzed material to obtain the treated cellulose; (2) Take 16.2g of treated cellulose, 100mL of ethanol and 50mL of deionized water and add them to a flask. Disperse the mixture by sonication for 30min and adjust the pH of the system to 8 with 10% sodium hydroxide. Then add 6.0g of sodium 3-chloro-2-hydroxypropanesulfonate and heat to 50℃ for 2h (maintain pH at 8 during the reaction). After the reaction is complete, adjust the pH to 7 with 10% acetic acid. Cool to room temperature, filter and wash with anhydrous ethanol. Freeze-dry the solid to obtain modified cellulose.

[0023] Example 1 Add 0.3 parts of modified cellulose to 60 parts of water, stir and disperse at 20°C for 40 minutes to obtain a uniform modified cellulose dispersion. Slowly add 45 parts of amphoteric surfactant to the modified cellulose dispersion, continue stirring for 60 minutes, and then ultrasonically disperse for 20 minutes to obtain an environmentally friendly oilfield displacement agent.

[0024] Example 2 Add 0.2 parts of modified cellulose to 55 parts of water, stir and disperse at 20°C for 40 minutes to obtain a uniform modified cellulose dispersion. Slowly add 42 parts of amphoteric surfactant to the modified cellulose dispersion, continue stirring for 50 minutes, and then ultrasonically disperse for 20 minutes to obtain an environmentally friendly oilfield displacement agent.

[0025] Example 3 Add 0.4 parts of modified cellulose to 63 parts of water, stir and disperse at 20°C for 40 minutes to obtain a uniform modified cellulose dispersion. Slowly add 50 parts of amphoteric surfactant to the modified cellulose dispersion, continue stirring for 60 minutes, and then ultrasonically disperse for 15 minutes to obtain an environmentally friendly oilfield displacement agent.

[0026] Comparative Example 1 The example is essentially the same as Example 1, except that the amphoteric surfactant is replaced with lauramide propyl hydroxysulfonate betaine (i.e., a conventional amphoteric surfactant).

[0027] Comparative Example 2 The example is essentially the same as Example 1, except that the amphoteric surfactant is replaced with sodium dodecylbenzenesulfonate (i.e., anionic surfactant).

[0028] Comparative Example 3 It is basically the same as Example 1, except that the modified cellulose is replaced with ordinary commercially available carboxymethyl cellulose.

[0029] The environmentally friendly oilfield displacement agents prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to tests for interfacial tension, oil displacement effect, and high-temperature and high-salt stability. The specific test methods are as follows: Interfacial tension: Performed according to SY / T 6424-2000 standard; Oil displacement effect: The recovery rate was obtained according to the SY / T 6424-2000 standard. High temperature and high salt stability: The oil displacement agent was placed in a simulated high temperature and high salt environment (temperature 120℃, salinity 20000mg / L) and kept at a constant temperature for 7 days. The stratification and precipitation were observed. The recovery rate was then measured after the standing period (test method is the same as oil displacement effect). The performance retention rate was calculated (retention rate = performance value after standing period / initial performance value × 100%).

[0030] The test results are shown in Table 1, and are as follows: Table 1 As can be seen from the test results in Table 1, the oil displacement agent prepared by the method of the present invention has low interfacial tension, high recovery rate, and good high-temperature and high-salt stability. This indicates that the present invention reduces the oil-water interfacial tension by preparing amphoteric surfactants and modified cellulose in synergy, which can effectively remove residual oil film on the surface of rock pores and greatly improve the micro-washing efficiency. The introduction of sulfonic acid groups into the amphoteric surfactants and modified cellulose enables the oil displacement agent to maintain good performance under high temperature and high salinity. Furthermore, the oil displacement agent prepared by the present invention has no environmental residue risk and excellent environmental performance.

[0031] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An environmentally friendly oilfield displacement agent, characterized in that, The oil displacement agent comprises the following components in parts by weight: 0.1-0.5 parts modified cellulose, 40-60 parts amphoteric surfactant, and 50-70 parts water; The amphoteric surfactant is prepared by reacting sodium methyl lauryl sulfonate, 4-dimethylaminobutyramine, and dichloroethane.

2. The environmentally friendly oilfield displacement agent according to claim 1, characterized in that, The synthesis of the amphoteric surfactant includes the following steps: (1) Add lauric acid, methanol and catalyst to a flask and stir at 60-70℃ for 3-5 h. After the reaction is complete, add organic solvent and sulfonating agent to the system and continue stirring at 70-80℃ for 0.5-1 h. Then raise the temperature to 80-90℃ and add hydrogen peroxide to mix. Then add methanol and stir at 50-60℃ for 0.5-2 h. After the reaction is complete, post-process to obtain sodium methyl laurate sulfonate. (2) Sodium methyl laurate sulfonate and 4-dimethylaminobutyramine were added to a flask and an alkaline solution was added to adjust the pH of the system to 9-10 while stirring. The reaction was carried out at 70-90℃ for 3-5 hours. After the reaction was completed, the intermediate was obtained through post-processing. (3) Add the intermediate and dichloroethane to a flask, stir and mix at 50-70℃, adjust the pH of the system to 7-8 with alkaline solution, stir and react for 5-10 hours, and after the reaction is completed, perform post-treatment to obtain the amphoteric surfactant.

3. The environmentally friendly oilfield displacement agent according to claim 2, characterized in that, In step (1), the mass of hydrogen peroxide added is 1-3% of the mass of lauric acid added.

4. The environmentally friendly oilfield displacement agent according to claim 2, characterized in that, In step (2), the molar ratio of sodium methyl laurate sulfonate and 4-dimethylaminobutyramine is 1:1-1.

5.

5. The environmentally friendly oilfield displacement agent according to claim 1, characterized in that, The modified cellulose is sodium 3-chloro-2-hydroxypropanesulfonate modified cellulose.

6. The environmentally friendly oilfield displacement agent according to claim 1, characterized in that, The synthesis of the modified cellulose includes the following steps: (1) Mix microcrystalline cellulose with deionized water, add hydrochloric acid dropwise under ice bath conditions, react at 70-80℃ for 1-3 hours, stop heating after the reaction is completed, add deionized water for dilution, then centrifuge at high speed, dialyze the obtained solid, freeze dry the dialyzed solid to obtain the treated cellulose. (2) Add the cellulose, ethanol and deionized water treated in step (1) into a flask, sonicate for 20-40 min, adjust the pH of the solution to 8-9 with sodium hydroxide, add sodium 3-chloro-2-hydroxypropanesulfonate, heat to 50-60℃ and react for 1-3 h. After the reaction is completed, perform post-treatment to obtain modified cellulose.

7. The environmentally friendly oilfield displacement agent according to claim 6, characterized in that, In step (1), the particle size of microcrystalline cellulose is 40-100µm.

8. The environmentally friendly oilfield displacement agent according to claim 6, characterized in that, In step (1), the mass fraction of hydrochloric acid is 20-40%, and the volume mass ratio of hydrochloric acid to microcrystalline cellulose is (1.5-2.5) mL:1g.

9. The environmentally friendly oilfield displacement agent according to claim 1, characterized in that, The amount of modified cellulose added is 0.4-0.8% of the mass of the amphoteric surfactant added.

10. A method for preparing an environmentally friendly oilfield displacement agent according to any one of claims 1-9, characterized in that, Includes the following steps: Add the modified cellulose to water according to the specified weight, stir and disperse at 20-40℃ to obtain a modified cellulose dispersion, then slowly add the amphoteric surfactant to the modified cellulose dispersion, continue stirring for 30-60 minutes, and then ultrasonically disperse for 15-25 minutes to obtain an environmentally friendly oilfield displacement agent.

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