Polymer initiator for oil displacement and preparation method thereof
By preparing azo initiators that do not contain nitrile groups, the problems of toxicity and gel formation during oil displacement were solved, high-efficiency high-molecular-weight polymerization at low temperature and low concentration was achieved, and oil displacement efficiency and polymer quality were improved.
Patent Information
- Application Number
- CN202510786263.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-12
- Publication Date
- 2025-09-16
AI Technical Summary
Existing azo initiators have toxicity problems during the oil recovery process, generate insoluble byproducts and gel blocks, and are difficult to produce high-linear high-molecular-weight polymers, affecting oil recovery efficiency and environmental safety.
By preparing an azo initiator with a specific structure, including condensation, hydrolysis and neutralization reactions, an azo compound without nitrile group is generated, avoiding side reactions and gel formation, and is suitable for low-temperature and low-concentration polymerization.
It can efficiently initiate polymerization at low temperature and low concentration to generate highly linear and high molecular weight polymers, improve oil displacement efficiency, reduce energy consumption, and is suitable for a variety of polymerization environments to generate high-quality polymer products.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of organic chemistry, in particular to a polymer initiator for oil displacement and a preparation method thereof. Background Art
[0002] Azo thermal initiators, containing an azo group in their molecules, are unique compounds. When exposed to thermal energy, these compounds undergo a decomposition process, generating free radicals (primarily carbon radicals) and simultaneously releasing nitrogen gas. The decomposition reaction of azo initiators is a first-order reaction with a well-defined reaction rate and mechanism. A unique feature of this type of initiator is that they do not undergo induced decomposition and remain stable even in contact with metals. Furthermore, their decomposition process is unaffected by solvents and impurities, ensuring the purity and reproducibility of the reaction. Compared to peroxide initiators, azo initiators produce fewer side reactions, resulting in improved selectivity and products with relatively high molecular weights, good water solubility, and low residual residues. They exhibit a smooth, stable, and controllable decomposition reaction, producing highly linear and high-molecular-weight polymers. In particular, in solutions containing Cl, when the pH is below 7, strong oxidizing groups such as S2O8 react with chloride ions to produce Cl2. Cl atoms act as chain terminators, reducing molecular weight. Based on this, the use of azo initiators, which cannot oxidize Cl, yields polymers with higher molecular weights. Unlike azonitrile products, these initiators lack a nitrile group, resulting in non-toxic decomposition products. They also decompose more smoothly than other initiators, offering higher conversion rates and no residue or agglomeration during the polymerization process. They can efficiently initiate polymerization at low temperatures and low concentrations, producing highly linear and high-molecular-weight polymers. Consequently, they are widely used in aqueous solution and emulsion polymerization for polymer synthesis. Furthermore, they exhibit excellent stability, even when subjected to shock, making them easy to handle, transport, and store for extended periods.
[0003] Polymer flooding technology is an important method for enhancing crude oil recovery. The performance of its core oil-displacing agents—polyacrylamide polymers (such as partially hydrolyzed polyacrylamide, HPAM), particularly their molecular weight, solubility, linearity, and shear resistance—directly determines their efficiency. The initiator system used in the polymerization reaction is a key factor in controlling the polymer's molecular structure and properties.
[0004] Nitrile-based azo compounds, such as azobis(isoheptanonitrile), have been explored for polymerization due to their excellent thermal decomposition activity at relatively low temperatures. However, their fatal drawback is that their decomposition products contain highly toxic nitriles. This not only poses environmental and occupational health risks, but also, when used in oilfields, the toxic residues can cause long-term, persistent pollution to the underlying environment and water quality. Furthermore, certain nitrile-containing azo initiators may generate insoluble byproducts or residues during the polymerization process or subsequent applications, leading to turbidity in the polymer solution or the formation of "fish eyes" and gel blocks, seriously affecting the solubility, injectability, and ultimate oil recovery efficiency of the polymer flooding agent. Although their decomposition is relatively smooth and side reactions are minimal, their inherent toxicity severely limits their application in oilfield chemicals, particularly in the production of oil-displacement polymers that involve large-scale production, transportation, and underground disposal.
[0005] Oil recovery polymers urgently require ultra-high molecular weight (ranging from tens of millions to tens of millions of Daltons) and highly linear polymer structures. This not only provides the necessary viscoelastic properties for viscosity enhancement, but also ensures long-term thermal, chemical, and mechanical stability in porous media. Existing initiation systems fall short in meeting these core requirements.
[0006] During the polymerization process, heterogeneity within the reactor, such as localized overheating or high concentrations, often leads to the formation of insoluble microgels, fisheyes, or polymer aggregates (lumps). These polymer gels can significantly block reservoir pores, preventing the flow of crude oil and causing permanent reservoir damage, reducing injectivity and ultimately compromising recovery. Therefore, developing an initiation system that can decompose smoothly and uniformly throughout the polymerization process to avoid gel formation is crucial.
[0007] In summary, the development of a new initiator that is highly efficient (especially at low temperature and low concentration), safe and non-toxic, not interfered with by chloride ions, can stably initiate in salt-containing systems without producing residue / agglomeration, and can obtain ultra-high linear and ultra-high molecular weight polymers has become an urgent need to improve the effectiveness of polymer flooding technology and expand its applicable mine conditions. Summary of the Invention
[0008] The object of the present invention is to provide a polymer initiator for oil displacement, which can be used for monomer polymerization, can efficiently initiate polymerization at low temperature and low concentration, does not produce residue and agglomeration during the polymerization process, generates highly linear and high molecular weight polymers, and can significantly improve polymer products and quality, so as to solve the problems existing in the prior art.
[0009] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a polymer initiator for oil displacement, comprising the following preparation steps:
[0010] (1) Condensation reaction: Add a certain amount of ethanol to a reaction vessel equipped with a stirrer and a thermometer, start the stirrer, introduce a certain amount of hydrogen chloride gas, add a certain amount of azobisisoheptanonitrile, and react at a temperature of 0°C to 60°C for 2 to 24 hours;
[0011] (2) Hydrolysis reaction: adding a certain amount of desalted water to step (1) and carrying out a hydrolysis reaction at a temperature of 0°C-60°C for 0.5-8h;
[0012] (3) Neutralization reaction: add a certain amount of sodium carbonate to the system of step (2), and neutralize at a temperature of 0°C-60°C for 0.5-4 hours. After the reaction liquid is allowed to stand, it separates into two layers, and the upper layer liquid is separated to obtain intermediate S1;
[0013] (4) Synthesis reaction: Add a certain amount of ethanol to dissolve the intermediate S1, add a certain amount of diaminobutane and acetyl chloride, and react at a temperature of 0°C-60°C for 1-16 hours. Then add a certain amount of desalted water. After the reaction solution is still, it separates into two layers, and the upper layer liquid is separated to obtain the initiator.
[0014] Furthermore, in step (1), the weight ratio of ethanol, hydrogen chloride and azobisisoheptanenitrile is 58-209:45-182:60.
[0015] Furthermore, in step (2), the weight ratio of desalted water to azobisisoheptanonitrile is 1 to 5:1.
[0016] Furthermore, in step (3), the weight ratio of sodium carbonate to azobisisoheptanonitrile is 0.2-2.5:1.
[0017] Furthermore, the pH value at the end point of the neutralization reaction in step (3) is 6.0-7.5.
[0018] Furthermore, in step (4), the weight ratio of the intermediate S1 to ethanol is 1:3-15.
[0019] Furthermore, in step (4), the weight ratio of the intermediate S1 to butanediamine and acetyl chloride is 1:0.1-1.5:0.12-1.2.
[0020] The polymer initiator for oil displacement of the present invention does not contain a nitrile group. Compared with azonitrile initiator products, the decomposition product is non-toxic. At the same time, it decomposes more smoothly than ordinary azo initiators, is not easily cross-linked, has a higher conversion rate, is free of residue, and does not produce residues or lumps during the polymerization process. It can also efficiently initiate polymerization at low temperature and low concentration to generate highly linear and high molecular weight polymers. It is particularly suitable for aqueous solution polymerization or emulsion polymerization of acrylamide, acrylic acid, etc., and can be used to produce products such as polyacrylamide oil displacement agents, water absorbents (raw materials for making diapers), and water purifiers. At the same time, the polymer initiator for oil displacement of the present invention also has good stability and can remain stable even when subjected to impact, making it easy to operate, transport, and store for a long time.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] (1) The initiator of the present invention can efficiently initiate polymerization reactions at relatively low temperatures (reaction temperature is only 0°C to 60°C) and relatively low monomer concentrations, significantly reducing the energy consumption requirements of the reaction. It is suitable for a variety of polymerization environments, especially for temperature-sensitive monomer polymerization processes, thus broadening its scope of application.
[0023] (2) The initiator of the present invention belongs to the azo initiator class with a specific structure, does not contain a nitrile group, and has unique properties different from peroxide initiators. Its decomposition process is not affected by chloride ions and pH value, avoiding the disadvantage of generating chain-terminating Cl atoms in chloride-containing solutions, which leads to a decrease in polymer molecular weight. Therefore, it can stably and controllably generate high-molecular-weight, highly linear polymers, which is crucial for improving the viscosity-increasing and shear resistance of polymer oil displacement agents.
[0024] (3) Due to the specific structural design and precise control of the preparation process, the initiator of the present invention decomposes smoothly during the polymerization process, does not cause residue and agglomeration in the system, and effectively prevents the formation of secondary by-products such as gel clusters.
[0025] (4) The preparation method of the present invention ensures a high purity of the initiator. It has a high conversion rate during polymerization initiation, few side reactions, and can produce a polymer product with a high relative molecular mass, a narrow molecular weight distribution, and excellent water solubility, thereby ensuring the quality of the final polymer used for oil recovery.
[0026] (5) The initiator of the present invention is conducive to the generation of high molecular weight, high linear polymers, thereby achieving better viscosity enhancement, viscoelasticity, long-term stability and displacement and plugging effects on oil reservoirs, which can significantly improve crude oil recovery.
[0027] (6) The synthetic preparation process of the present invention is highly operable, easy to control, and has good reproducibility, and is suitable for industrial production. DETAILED DESCRIPTION
[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. 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.
[0029] Example 1: Synthesis of a polymer initiator for oil displacement:
[0030] (1) Condensation reaction: 158 g of ethanol was added to a flask equipped with a stirrer and a thermometer. The stirrer was started, 91 g of hydrogen chloride gas was introduced, and 85 g of azobisisoheptanonitrile was added. The reaction temperature was maintained at 10°C and the reaction time was 12 h.
[0031] (2) Hydrolysis reaction: Add 120 g of desalted water to the above reaction system and stir at 10°C and 30 rpm for 0.5 h;
[0032] (3) Neutralization reaction: 100 g of a 20 wt% sodium carbonate aqueous solution was added to the above reaction system and the reaction was allowed to neutralize at 10°C for 1 h. The pH value of the reaction solution was detected by pH test paper to 6.8. The reaction solution was allowed to stand for 3 h. The reaction solution separated into two layers, and the upper layer was separated to obtain the intermediate S1.
[0033] (4) Synthesis reaction: After the intermediate S1 was dissolved in 300 g of ethanol, 20 g of diaminobutane and 25 g of acetyl chloride were added, and the mixture was stirred at 40°C for 8 h. 150 g of desalted water was added, and the reaction solution was allowed to stand and separate into two layers. The upper layer of liquid was separated to obtain the azo compound sample SGA-01.
[0034] Example 2: Synthesis of a polymer initiator for oil displacement:
[0035] (1) Condensation reaction: 198 g of ethanol was added to a flask equipped with a stirrer and a thermometer. The stirrer was started, 112 g of hydrogen chloride gas was introduced, and 98 g of azobisisoheptanonitrile was added. The reaction temperature was maintained at 15°C and the reaction time was 10 h.
[0036] (2) Hydrolysis reaction: Add 150 g of desalted water to the above reaction system and stir at 15°C and 30 rpm for 1 h;
[0037] (3) Neutralization reaction: 120 g of 20 wt% sodium carbonate solution was added to the above reaction system and the reaction was allowed to neutralize at 15°C for 1 h. The pH value of the reaction solution was detected by pH test paper to 6.8. The reaction solution was allowed to stand for 3 h. The reaction solution separated into two layers, and the upper layer was separated to obtain intermediate S1.
[0038] (4) Synthesis reaction: After the intermediate S1 was dissolved in 330 g of ethanol, 23 g of diaminobutane and 29 g of acetyl chloride were added, and the mixture was stirred at 38°C for 12 h. 200 g of desalted water was added, and the reaction solution was allowed to stand and separate into two layers. The upper layer of liquid was separated to obtain the azo compound sample SGA-02.
[0039] Example 3: Synthesis of a polymer initiator for oil displacement:
[0040] (1) Condensation reaction: 168 g of ethanol was added to a flask equipped with a stirrer and a thermometer. The stirrer was started, 102 g of hydrogen chloride gas was introduced, and 90 g of azobisisoheptanonitrile was added. The reaction temperature was maintained at 10°C and the reaction time was 12 h.
[0041] (2) Hydrolysis reaction: Add 140 g of desalted water to the above reaction system and stir at 10°C for 1 h;
[0042] (3) Neutralization reaction: 105 g of 20 wt% sodium carbonate solution was added to the above reaction system and the reaction was allowed to neutralize at 10°C for 1 h. The pH value of the reaction solution was detected by pH test paper to 6.8. The reaction solution was allowed to stand for 3 h. The reaction solution separated into two layers, and the upper layer was separated to obtain intermediate S1.
[0043] (4) Synthesis reaction: After the intermediate S1 was dissolved in 320 g of ethanol, 22 g of diaminobutane and 27 g of acetyl chloride were added, and the mixture was stirred at 30°C for 12 h. 220 g of desalted water was added, and the reaction solution was allowed to stand and separate into two layers. The upper layer of liquid was separated to obtain the azo compound sample SGA-03.
[0044] Example 4: Synthesis of a polymer initiator for oil displacement:
[0045] (1) Condensation reaction: 178 g of ethanol was added to a flask equipped with a stirrer and a thermometer. The stirrer was started, 99 g of hydrogen chloride gas was introduced, and 80 g of azobisisoheptanonitrile was added. The reaction temperature was maintained at 20°C and the reaction time was 10 h.
[0046] (2) Hydrolysis reaction: Add 140 g of desalted water to the above reaction system and stir at 20°C for 1 h;
[0047] (3) Neutralization reaction: 130 g of 20 wt% sodium carbonate solution was added to the above reaction system and the reaction was allowed to neutralize at 20°C for 1 h. The pH value of the reaction solution was detected by pH test paper until it reached 7.0. The reaction solution was allowed to stand for 3 h. The reaction solution separated into two layers, and the upper layer was separated to obtain intermediate S1.
[0048] (4) Synthesis reaction: The intermediate S1 was added to 300 g of ethanol to dissolve, and then 22 g of diaminobutane and 25 g of acetyl chloride were added. The mixture was stirred at 30°C for 12 h. 230 g of desalted water was added. The reaction solution was allowed to stand and separated into two layers. The upper layer of liquid was separated to obtain the azo compound sample SGA-04.
[0049] Example 5: Performance evaluation of a polymer initiator for oil displacement
[0050] 1) Polyacrylamide polymerization and product physical and chemical properties testing:
[0051] Taking the above-mentioned azo compounds SGA-01, SGA-02, SGA-03, SGA-04 and the commercially available azo initiator azobisisobutyronitrile as comparison, the polyacrylamide synthesis method is as follows:
[0052] 1000 kg of deionized water was measured and added to the reactor, the stirrer was started, 350 kg of acrylamide was added, and stirred until completely dissolved; 0.8 kg of initiator was added; nitrogen was passed through the material system for 35 minutes to remove dissolved oxygen in the water; the above-mentioned polymer colloid material was sent to the hydrolysis reactor, 49 kg of sodium hydroxide solid was added to the hydrolysis reactor, and the mixture was stirred thoroughly. The temperature was raised to 90°C and kept warm for 3 hours. After that, the polymer samples P1, P2, P3, P4, and P5 were obtained respectively. The basic physical and chemical properties of the four polymer samples P1, P2, P3, P4, and P5 were tested according to the interim provisions of the "Testing and Evaluation Methods and Technical Requirements for Salt-Resistant Polymers for Oil Displacement" of Daqing Oilfield Company. The results are shown in Table 1.
[0053] Table 1 Evaluation results of physicochemical properties of 4 polymers
[0054]
[0055]
[0056] As can be seen from Table 1, in terms of the molecular weight indicators of the polymers synthesized under the same conditions, the molecular weights of polymers P1, P2, P3, and P4 synthesized using the oil displacement polymer initiator as the polymerization initiator are all ≥16 million, which is higher than the molecular weight of polymer P5 synthesized using azobisisobutyronitrile as the initiator, which is 12 million.
[0057] Viscosity index: the viscosities of polymers P1, P2, P3, and P4 synthesized using the oil displacement polymer initiator as the polymerization initiator are all ≥45 mPa·s, which is higher than the viscosity of polymer P5 synthesized using azobisisobutyronitrile as the initiator, which is 40.3 mPa·s.
[0058] As for the filtration factor index, the filtration factors of polymers P1, P2, P3 and P4 synthesized using the polymer initiator for oil displacement as the polymerization initiator are all 1.1, which is lower than the filtration factor of polymer P5 synthesized using azobisisobutyronitrile as the initiator, which is 1.4.
[0059] As for the water-insoluble index, the filtration factors of polymers P1, P2, P3, and P4 synthesized using the oil displacement polymer initiator as the polymerization initiator are all less than 0.10, which is lower than the water-insoluble index of polymer P5 synthesized using azobisisobutyronitrile as the initiator, which is 0.13.
[0060] As for the residual monomer index, the residual monomer content of polymers P1, P2, P3 and P4 synthesized using the oil displacement polymer initiator as the polymerization initiator is 0.01%, which is lower than the residual monomer content of polymer P5 synthesized using azobisisobutyronitrile as the initiator, which is 0.04%.
[0061] In summary, polymers P1, P2, P3, and P4 synthesized using the oil displacement polymer initiator as the polymerization initiator are much better than polymer P5 synthesized using azobisisobutyronitrile as the initiator in terms of molecular weight, viscosity, filtration factor, water-insoluble matter, residual monomer content, etc., indicating that the azo compound (SGA) has better polymerization initiation performance, and the performance indicators of the polymer products synthesized therefrom are better than those of the polymers synthesized using the common azo initiator azobisisobutyronitrile.
[0062] 2) Polymer viscosity increasing performance test
[0063] Polymers P1, P2, P3, P4, and P5 were prepared into 5000 mg / L polymer mother solutions using saline solution with a salinity of 2410 mg / L. The mother solutions were then diluted to concentrations of 200 mg / L to 2000 mg / L. The viscosities of the target solutions were measured at 45°C. The results are shown in Table 2.
[0064] Table 24 polymer concentration-viscosity test results
[0065]
[0066]
[0067] As can be seen from Table 2, the viscosities of polymers P1, P2, P3, and P4 synthesized using the oil displacement polymer initiator as the polymerization initiator at each concentration are higher than those of polymer P5 synthesized using azobisisobutyronitrile as the initiator, and the synthesized polymers have better viscosity-increasing properties.
[0068] Compared with general azo initiators, the polymer initiator for oil displacement of the present invention has a smoother, more stable and controllable decomposition reaction. When used for polymerization, it has a higher initiation efficiency, the synthesized polymer product has a higher relative molecular mass, good water solubility and less residual body, and it is easier to synthesize highly linear and high molecular weight polymers.
[0069] Polymerization experiments show that the polyacrylamide synthesized using the polymer initiator for oil displacement of the present invention as a polymerization initiator is superior to the polyacrylamide product synthesized using azobisisobutyronitrile as an initiator in terms of indicators such as molecular weight, viscosity, filtration factor, water-insoluble matter, residual monomer content, and viscosity-increasing performance. This indicates that the polymer initiator for oil displacement of the present invention has better polymerization initiation performance than ordinary azo initiators, and the performance indicators of the polymer product synthesized therefrom are superior to those of the polymer synthesized using ordinary azo initiators.
[0070] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Anyone familiar with the technical specifications of this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solution of the present invention, still fall within the scope of the technical solution of the present invention.
[0071] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.
Claims
1. A method for preparing a polymer initiator for oil displacement, characterized in that: The method comprises the following preparation steps: (1) Condensation reaction: Add a certain amount of ethanol to a reaction vessel equipped with a stirrer and a thermometer, start the stirrer, introduce a certain amount of hydrogen chloride gas, add a certain amount of azobisisoheptanonitrile, and react for 2 to 24 hours; (2) Hydrolysis reaction: adding a certain amount of desalted water to step (1) and carrying out the hydrolysis reaction for 0.5-8 hours; (3) Neutralization reaction: Add a certain amount of sodium carbonate to the system of step (2), and neutralize for 0.5-4 hours. After the reaction solution is allowed to stand, it separates into two layers, and the upper layer is separated to obtain the intermediate S1; (4) Synthesis reaction: Add a certain amount of ethanol to dissolve the intermediate S1, add a certain amount of diaminobutane and acetyl chloride, and react at a temperature of 0°C-60°C for 1-16 hours. Then add a certain amount of desalted water. After the reaction solution is still, it separates into two layers, and the upper layer liquid is separated to obtain the initiator.
2. The method for preparing a polymer initiator for oil displacement according to claim 1, wherein The weight ratio of ethanol, hydrogen chloride and azobisisoheptanenitrile in step (1) is 58-209:45-182:
60.
3. The method for preparing a polymer initiator for oil displacement according to claim 1, wherein: The weight ratio of desalted water to azobisisoheptanonitrile in step (2) is 1 to 5:
1.
4. The method for preparing a polymer initiator for oil displacement according to claim 1, wherein: In step (3), the weight ratio of sodium carbonate to azobisisoheptanonitrile is 0.2-2.5:
1.
5. The method for preparing a polymer initiator for oil displacement according to claim 1, wherein: The pH value at the end point of the neutralization reaction in step (3) is 6.0-7.
5.
6. The method for preparing a polymer initiator for oil displacement according to claim 1, wherein: The reaction temperature in step (1), step (2) and step (3) is 0-60°C.
7. The method for preparing a polymer initiator for oil displacement according to claim 1, wherein: The weight ratio of the intermediate S1 to ethanol in step (4) is 1:3-15.
8. The method for preparing a polymer initiator for oil displacement according to claim 1, wherein: In step (4), the weight ratio of intermediate S1 to diaminodiamine and acetyl chloride is 1: 0.1～1.5：0.12-1.2。 9. A polymer initiator for oil displacement, characterized in that: The polymer initiator for oil displacement prepared by the preparation method according to any one of claims 1 to 7 is an azo compound, and its structural formula is as follows:
10. Use of the polymer initiator for oil displacement according to claim 9 or the polymer initiator for oil displacement obtained by the preparation method according to any one of claims 1 to 8 in the preparation of oil displacement polymers.