High-temperature-resistant oil-displacing agent for oil field and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant oil-displacing agent for an oil field and a preparation method thereof, and relates to the technical field of oilfield exploitation. The prepared oil displacement agent for the oil field comprises the following raw materials in parts by weight: 15-25 parts of polyacrylamide, 1-5 parts of nano silicon dioxide, 25-35 parts of an enhanced surfactant and 40-60 parts of water. The oil-displacing agent is prepared by mixing and stirring the raw materials, and has excellent oil-displacing performance, low surface tension and excellent high-temperature resistance when being used in the oilfield exploitation process; compared with a traditional surfactant, due to the introduction of the enhanced surfactant, the high temperature resistance and the oil displacement efficiency of the oil displacement agent are improved.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a high-temperature resistant oil displacement agent for oilfields and its preparation method. Background Technology

[0002] With the continued growth of global energy demand and the increasing depletion of conventional oil resources, the efficient extraction of residual oil from developed reservoirs has become a severe challenge for the petroleum industry. Waterflooding, as a primary technology for secondary oil recovery, can maintain formation energy, but its recovery rate is typically only 30% to 50%, with a large amount of crude oil remaining in the formation pores due to capillary forces. To improve crude oil recovery, chemical flooding, especially surfactant flooding, has become one of the core technologies for tertiary oil recovery. Its basic principle is to add surfactants to the injected water, significantly reducing the interfacial tension (IFT) between oil and water and altering the wettability of the reservoir rock, thereby stripping and activating the residual crude oil after waterflooding, forming an oil band and driving it towards the production well.

[0003] However, surfactant flooding technology faces significant bottlenecks when applied to high-temperature oil reservoirs. Numerous deep oil reservoirs exist in my country and globally, with formation temperatures often exceeding 85°C, and even reaching over 120°C, exhibiting high salinity and high content of divalent ions (such as Ca²⁺ and Mg²⁺). Under these harsh conditions, traditional surfactants, such as conventional petroleum sulfonates, alkylbenzene sulfonates, or nonionic surfactants, have inherent defects, such as poor thermochemical stability and failure of interfacial properties and wettability modification capabilities at high temperatures. Therefore, developing a novel oil displacement agent that combines high oil displacement efficiency with outstanding high-temperature stability is of great practical significance and economic value for fully tapping the potential of deep oil and gas resources and improving crude oil recovery. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a high-temperature resistant oil displacement agent for oil fields and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A high-temperature oil displacement agent for oil fields comprises the following raw materials in parts by weight: 15-25 parts polyacrylamide, 1-5 parts nano silica, 25-35 parts reinforced surfactant, and 40-60 parts water. The enhanced surfactant is prepared by the following steps: Step A1: Mix 4-vinylphenol, sodium hydroxide and acetonitrile evenly, then slowly add them to cyanochloroacetonitrile solution and stir evenly. Then place the mixture in an ice-water bath and stir for 4 hours to obtain product 1 solution. Further, in step A1, the ratio of the amounts of 4-vinylphenol, sodium hydroxide, acetonitrile, and cyanochloroacetonitrile solution is 0.01-0.03 mol: 0.4-1.2 g: 100 mL: 100 mL; Furthermore, in step A1, the cyanuric chloride acetonitrile solution is prepared by mixing and stirring cyanuric chloride and acetonitrile at a volume ratio of 0.01-0.03 mol: 100 mL; Step A2: Mix ethylenediamine, sodium hydroxide and acetonitrile until homogeneous, and record as mixture 1; heat the above product 1 solution to 55°C, then add 1 / 2 volume of mixture 1, and maintain the temperature for 4-6 hours; then heat to 90°C, add the remaining mixture 1, and maintain the temperature for 12 hours; filter, wash and dry to obtain triazine derivative. Furthermore, in step A2, the ratio of ethylenediamine, sodium hydroxide, and acetonitrile in mixture 1 is 0.02-0.06 mol: 0.8-2.4 g: 100 mL; Step A3: Add the triazine derivative and sodium 2-chloroethylsulfonate to the reactor in sequence, then add water, heat to 90-95℃ under nitrogen protection, heat to reflux for 24 hours, and maintain the pH of the system at 9-10. After the reaction is completed, rotary evaporate, wash and dry to obtain the triazine-sodium sulfonate derivative. Furthermore, in step A3, the molar ratio of the triazine derivative and sodium 2-chloroethylsulfonate is 1:2; Furthermore, in step A3, a 0.1 mol / L sodium hydroxide solution is used to maintain the pH of the system at 9-10; Step A4: Mix the triazine-sulfonate sodium derivative in water and stir until homogeneous. Heat to 60°C, then add chloroplatinic acid solution and stir for 10-20 min. Add heptamethyltrisiloxane and stir for 30 min. Heat to 100-120°C and reflux for 5-7 h. Add chloroform to dilute, then add activated carbon to remove the remaining catalyst. Distill under reduced pressure and dry to obtain the enhanced surfactant. Further, in step A4, the ratio of the amount of triazine-sulfonate sodium derivative, water, chloroplatinic acid solution, heptamethyltrisiloxane, chloroform and activated carbon is 0.02mol:100mL:0.25-0.35mL:0.02mol:30mL:5-10g; Furthermore, the chloroplatinic acid solution in step A4 is prepared by mixing and stirring chloroplatinic acid, isopropanol, and water in a volume ratio of 0.001 mol: 3 mL: 2 mL.

[0006] A method for preparing a high-temperature resistant oil displacement agent for oil fields includes the following steps: Weigh the raw materials according to the weight proportions, add the enhanced surfactant to the water and mix for 15-25 minutes, then add the polyacrylamide and stir for 30 minutes, finally add the nano silica and stir for 10 minutes, and then sonicate for 2 hours to obtain the high-temperature oil displacement agent for oil fields.

[0007] The beneficial effects of this invention are: The oil displacement agent prepared by this invention is made by mixing and stirring polyacrylamide, enhanced surfactant, nano silica and water. When used in oilfield extraction, it has excellent oil displacement performance, low surface tension and excellent high temperature resistance. Among them, the introduction of enhanced surfactant improves the high temperature resistance and oil displacement efficiency of the oil displacement agent compared with traditional surfactant.

[0008] The enhanced surfactant prepared in this invention is made by grafting a benzene ring, -Si-(CH3)3, and sodium sulfonate structure onto a triazine structure as a "bridge." The sodium sulfonate structure provides strong hydrophilicity, enabling the molecule to be firmly anchored in the aqueous phase, while the benzene ring, -Si-(CH3)3, and sodium sulfonate structure provide strong hydrophobicity. This amphiphilic structure, with one end being hydrophilic and the other hydrophobic, allows it to accumulate at the oil-water interface. The hydrophobic group penetrates into the oil phase, while the hydrophilic group remains in the aqueous phase, thereby effectively reducing the interfacial tension between oil and water. This surfactant can stabilize these oil droplets, forming an oil-in-water emulsion, preventing small oil droplets from re-aggregating into large oil beads and clogging pores again, thus significantly improving the oil recovery rate. Ordinary surfactants degrade or become ineffective rapidly in high-temperature (e.g., >85°C) oil reservoirs. However, the enhanced structure of this invention endows it with excellent thermal stability. This is because the triazine ring structure is a thermally stable aromatic heterocyclic structure with high chemical bond energies, requiring significant energy to break, thus exhibiting excellent resistance to thermal decomposition. Furthermore, the Si-C and Si-O bonds within it possess high bond energies, contributing to good thermal stability. The benzene ring, a classic aromatic ring structure, exhibits resonance effects that make it highly stable and resistant to ring-opening or degradation reactions at high temperatures. This ensures the structural integrity of the surfactant at high temperatures. In addition, the nitrogen atom on the triazine ring possesses a lone pair of electrons, allowing it to coordinate with metal ions on rock surfaces (such as clay minerals) or form hydrogen bonds with surface hydroxyl groups. This strong adsorption effectively "anchors" the surfactant molecule to the rock surface, significantly reducing its desorption rate under high-temperature water flow, thereby extending its effective lifespan. Detailed Implementation

[0009] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] Example 1: The enhanced surfactant was prepared by the following steps: Step A1: Mix 0.01 mol 4-vinylphenol, 0.4 g sodium hydroxide and 100 mL acetonitrile until homogeneous, then slowly add to 100 mL cyanochloroacetonitrile solution and stir until homogeneous. Place in an ice-water bath and stir for 4 hours to obtain product 1 solution. The cyanochloroacetonitrile solution is prepared by mixing cyanochlorochloroacetonitrile and acetonitrile in a ratio of 0.01 mol: 100 mL. Step A2: Mix 0.02 mol ethylenediamine, 0.8 g sodium hydroxide and 100 mL acetonitrile until homogeneous, and record as mixture 1; heat the above product 1 solution to 55°C, then add 50 mL of mixture 1, and maintain the temperature for 4 h; then heat to 90°C, add the remaining 50 mL of mixture 1, and maintain the temperature for 12 h; filter, wash and dry to obtain triazine derivative; Step A3: 0.1 mol of triazine derivative and 0.2 mol of sodium 2-chloroethyl sulfonate were added to the reactor in sequence, followed by 200 mL of water. The temperature was raised to 90 °C under nitrogen protection and heated to reflux for 24 h. The pH of the system was maintained at 9 using 0.1 mol / L sodium hydroxide solution. After the reaction was completed, the system was rotary evaporated, washed, and dried to obtain the triazine-sodium sulfonate derivative. Step A4: Mix 0.02 mol of sodium triazine sulfonate derivative in 100 mL of water and stir until homogeneous. Heat to 60°C, then add 0.25 mL of chloroplatinic acid solution and stir for 10 min. Add 0.02 mol of heptamethyltrisiloxane and stir for 30 min. Heat to 100°C and reflux for 5 h. Dilute with 30 mL of chloroform, then add 5 g of activated carbon to remove the remaining catalyst. Distill under reduced pressure and dry to obtain the enhanced surfactant. The chloroplatinic acid solution is prepared by mixing chloroplatinic acid, isopropanol and water in a ratio of 0.001 mol: 3 mL: 2 mL.

[0011] Example 2: The enhanced surfactant was prepared by the following steps: Step A1: Mix 0.02 mol 4-vinylphenol, 0.8 g sodium hydroxide and 100 mL acetonitrile until homogeneous, then slowly add to 100 mL cyanochloroacetonitrile solution and stir until homogeneous. Place in an ice-water bath and stir for 4 hours to obtain product 1 solution. The cyanochloroacetonitrile solution is prepared by mixing cyanochlorochloroacetonitrile and acetonitrile in a ratio of 0.02 mol: 100 mL. Step A2: Mix 0.04 mol ethylenediamine, 1.6 g sodium hydroxide and 100 mL acetonitrile until homogeneous, and record as mixture 1; heat the above product 1 solution to 55°C, then add 50 mL of mixture 1 and maintain the temperature for 5 h, then heat to 90°C, add the remaining 50 mL of mixture 1, maintain the temperature and continue the reaction for 12 h, filter, wash and dry to obtain triazine derivative; Step A3: Add 0.1 mol of triazine derivative and 0.2 mol of sodium 2-chloroethyl sulfonate to the reactor in sequence, then add 200 mL of water. Under nitrogen protection, heat to 95 °C and reflux for 24 h. Use 0.1 mol / L sodium hydroxide solution to maintain the pH of the system at 9.5. After the reaction is completed, rotary evaporate, wash and dry to obtain triazine-sodium sulfonate derivative. Step A4: Mix 0.02 mol of sodium triazine sulfonate derivative in 100 mL of water and stir until homogeneous. Heat to 60°C, then add 0.3 mL of chloroplatinic acid solution and stir for 15 min. Add 0.02 mol of heptamethyltrisiloxane and stir for 30 min. Heat to 110°C and reflux for 6 h. Dilute with 30 mL of chloroform, then add 7.5 g of activated carbon to remove the remaining catalyst. Distill under reduced pressure and dry to obtain the enhanced surfactant. The chloroplatinic acid solution is prepared by mixing chloroplatinic acid, isopropanol and water in a ratio of 0.001 mol: 3 mL: 2 mL.

[0012] Example 3: The enhanced surfactant was prepared by the following steps: Step A1: Mix 0.03 mol 4-vinylphenol, 1.2 g sodium hydroxide and 100 mL acetonitrile until homogeneous, then slowly add to 100 mL cyanochloroacetonitrile solution and stir until homogeneous. Then place in an ice-water bath and stir for 4 h to obtain product 1 solution. The cyanochloroacetonitrile solution is prepared by mixing cyanochlorochloroacetonitrile and acetonitrile in a ratio of 0.03 mol: 100 mL. Step A2: Mix 0.06 mol ethylenediamine, 2.4 g sodium hydroxide and 100 mL acetonitrile until homogeneous, and record as mixture 1; heat the above product 1 solution to 55°C, then add 50 mL of mixture 1, and maintain the temperature for 6 h; then heat to 90°C, add the remaining 50 mL of mixture 1, and maintain the temperature for 12 h; filter, wash and dry to obtain triazine derivative. Step A3: 0.1 mol of triazine derivative and 0.2 mol of sodium 2-chloroethyl sulfonate were added to the reactor in sequence, followed by 200 mL of water. The mixture was heated to 95 °C under nitrogen protection and refluxed for 24 h. The pH of the system was maintained at 10 using 0.1 mol / L sodium hydroxide solution. After the reaction was completed, the mixture was rotary evaporated, washed, and dried to obtain the triazine-sodium sulfonate derivative. Step A4: Mix 0.02 mol of sodium triazine sulfonate derivative in 100 mL of water and stir until homogeneous. Heat to 60°C, then add 0.35 mL of chloroplatinic acid solution and stir for 20 min. Add 0.02 mol of heptamethyltrisiloxane and stir for 30 min. Heat to 120°C and reflux for 7 h. Dilute with 30 mL of chloroform, then add 10 g of activated carbon to remove the remaining catalyst. Distill under reduced pressure and dry to obtain the enhanced surfactant. The chloroplatinic acid solution is prepared by mixing chloroplatinic acid, isopropanol and water in a ratio of 0.001 mol: 3 mL: 2 mL.

[0013] Example 4: A method for preparing a high-temperature resistant oil displacement agent for oil fields includes the following steps: 15 parts polyacrylamide, 1 part nano silica, 25 parts of the enhanced surfactant prepared in Example 1, and 40 parts water; Weigh the raw materials according to the weight parts, add the enhanced surfactant prepared in Example 1 to water and mix for 15 min, then add polyacrylamide and stir for 30 min, finally add nano silica and stir for 10 min, and then sonicate for 2 h to obtain the high temperature oil displacement agent for oil fields.

[0014] Example 5: A method for preparing a high-temperature resistant oil displacement agent for oil fields includes the following steps: 20 parts polyacrylamide, 3 parts nano silica, 30 parts enhanced surfactant prepared in Example 2, and 50 parts water; Weigh the raw materials according to the weight parts, add the enhanced surfactant prepared in Example 2 to water and mix for 20 min, then add polyacrylamide and stir for 30 min, finally add nano silica and stir for 10 min, and then sonicate for 2 h to obtain the high temperature oil displacement agent for oil fields.

[0015] Example 6: A method for preparing a high-temperature resistant oil displacement agent for oil fields includes the following steps: 25 parts polyacrylamide, 5 parts nano silica, 35 parts enhanced surfactant prepared in Example 3, and 60 parts water; Weigh the raw materials according to the weight parts, add the enhanced surfactant prepared in Example 3 to water and mix for 25 min, then add polyacrylamide and stir for 30 min, finally add nano silica and stir for 10 min, and then sonicate for 2 h to obtain the high temperature oil displacement agent for oil fields.

[0016] Comparative Example 1: This comparative example is an oilfield displacement agent. The difference between this example and Example 6 is that fatty acid alkanolamide is used instead of the enhanced surfactant prepared in Example 3. All other aspects are the same.

[0017] Comparative Example 2: This comparative example is an oilfield displacement agent. The difference between this example and Example 6 is that dodecylbenzenesulfonic acid is used instead of the enhanced surfactant prepared in Example 3. All other aspects are the same.

[0018] The performance of the oilfield displacement agents prepared in Examples 4-6 and Comparative Examples 1-2 was tested: Interfacial tension performance test: The oilfield displacement agents of each embodiment and comparative example were diluted with reinjection water to 0.3 wt%, and the oil-water interfacial tension between the displacement agent and the simulated oil at 80℃ was measured by rotating drop interface. High temperature resistance test: The oilfield displacement agents of each example and comparative example were aged at 90°C, 100°C, 120°C and 140°C for 48 hours respectively. After aging, the surface tension of the solution was tested. The test results are shown in Table 1: Table 1: Performance Test Results

[0019] As can be seen from Table 1, the oil displacement agent prepared by this invention still has a low surface tension at high temperatures, indicating that the use of this oil displacement agent in oilfield exploitation has better environmental adaptability than the use of traditional oil displacement agents, can adapt to higher temperatures, and maintains excellent oil displacement efficiency at high temperatures.

[0020] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A high-temperature resistant oil displacement agent for oilfields, characterized in that, The raw materials include the following parts by weight: 15-25 parts polyacrylamide, 1-5 parts nano silica, 25-35 parts reinforced surfactant, and 40-60 parts water. The enhanced surfactant is prepared by reacting a sodium triazine sulfonate derivative and heptamethyltrisiloxane under chloroplatinic acid catalysis and reflux at 100-120°C for 5-7 h. The sodium triazine sulfonate derivative is prepared by reacting a triazine derivative and sodium 2-chloroethylsulfonate under nitrogen at 90-95°C for 24 h. The triazine derivative is prepared by reacting cyanuric chloride sequentially with 4-vinylphenol and ethylenediamine.

2. The high-temperature resistant oil displacement agent for oilfields according to claim 1, characterized in that, The enhanced surfactant is prepared by the following steps: Step A1: Mix 4-vinylphenol, sodium hydroxide and acetonitrile evenly, then slowly add them to cyanochloroacetonitrile solution and stir evenly. Then place the mixture in an ice-water bath and stir for 4 hours to obtain product 1 solution. Step A2: Mix ethylenediamine, sodium hydroxide and acetonitrile until homogeneous, and record as mixture 1; heat the above product 1 solution to 55°C, then add 1 / 2 volume of mixture 1, and maintain the temperature for 4-6 hours; then heat to 90°C, add the remaining mixture 1, and maintain the temperature for 12 hours; filter, wash and dry to obtain triazine derivative. Step A3: Add the triazine derivative and sodium 2-chloroethylsulfonate to the reactor in sequence, then add water, heat to 90-95℃ under nitrogen protection, heat to reflux for 24 hours, and maintain the pH of the system at 9-10. After the reaction is completed, rotary evaporate, wash and dry to obtain the triazine-sodium sulfonate derivative. Step A4: Mix the triazine-sulfonate sodium derivative in water and stir until homogeneous. Heat to 60°C, then add chloroplatinic acid solution and stir for 10-20 min. Add heptamethyltrisiloxane and stir for 30 min. Then heat to 100-120°C and reflux for 5-7 h. Add chloroform to dilute, then add activated carbon to remove the remaining catalyst. Distill under reduced pressure and dry to obtain the enhanced surfactant.

3. The high-temperature resistant oil displacement agent for oilfields according to claim 2, characterized in that, In step A1, the ratio of the amounts of 4-vinylphenol, sodium hydroxide, acetonitrile, and cyanochloroacetonitrile solution is 0.01-0.03 mol: 0.4-1.2 g: 100 mL: 100 mL.

4. The high-temperature resistant oil displacement agent for oilfields according to claim 2, characterized in that, In step A1, the cyanuric chloride acetonitrile solution is prepared by mixing and stirring cyanuric chloride and acetonitrile at a ratio of 0.01-0.03 mol: 100 mL.

5. The high-temperature resistant oil displacement agent for oilfields according to claim 2, characterized in that, In step A2, the ratio of ethylenediamine, sodium hydroxide, and acetonitrile in mixture 1 is 0.02-0.06 mol: 0.8-2.4 g: 100 mL.

6. The high-temperature resistant oil displacement agent for oilfields according to claim 2, characterized in that, In step A3, the molar ratio of the triazine derivative and sodium 2-chloroethylsulfonate is 1:

2.

7. The high-temperature resistant oil displacement agent for oilfields according to claim 2, characterized in that, In step A3, a 0.1 mol / L sodium hydroxide solution is used to maintain the pH of the system at 9-10.

8. The high-temperature resistant oil displacement agent for oilfields according to claim 2, characterized in that, In step A4, the ratio of the amounts of triazine-sulfonate sodium derivative, water, chloroplatinic acid solution, heptamethyltrisiloxane, chloroform, and activated carbon is 0.02 mol: 100 mL: 0.25-0.35 mL: 0.02 mol: 30 mL: 5-10 g.

9. The high-temperature resistant oil displacement agent for oilfields according to claim 2, characterized in that, The chloroplatinic acid solution in step A4 is prepared by mixing and stirring chloroplatinic acid, isopropanol and water in a volume ratio of 0.001 mol: 3 mL: 2 mL.

10. A method for preparing a high-temperature resistant oil displacement agent for oilfields according to any one of claims 1-9, characterized in that, Includes the following steps: Weigh the raw materials according to the weight proportions, add the enhanced surfactant to the water and mix for 15-25 minutes, then add the polyacrylamide and stir for 30 minutes, finally add the nano silica and stir for 10 minutes, and then sonicate for 2 hours to obtain the high-temperature oil displacement agent for oil fields.

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