Temperature-resistant salt-tolerant polyacrylamide emulsion and preparation method thereof

Abstract

The invention provides a temperature-resistant and salt-resistant polyacrylamide emulsion and a preparation method thereof, and the preparation method comprises the following steps: adding acrylamide, an anionic monomer, a temperature-resistant and salt-resistant monomer and a structure regulator into water, and uniformly mixing to obtain a water-phase mixed solution; the preparation method comprises the following steps: uniformly stirring and mixing white oil and a compound emulsifier, adding a self-made hydrophobic association monomer and a chain transfer agent, and uniformly mixing to obtain an oil-phase mixed solution; wherein the self-made hydrophobic association monomer is provided with hydrophobic pyrenyl, a flexible spacer arm and a rigid benzene ring; and pouring the water-phase mixed solution into the oil-phase mixed solution, stirring and emulsifying, introducing nitrogen to remove oxygen, and adding an initiator water solution to initiate a reaction, thereby obtaining the temperature-resistant salt-tolerant polyacrylamide emulsion. The polyacrylamide emulsion provided by the invention can still maintain extremely high apparent viscosity at high temperature and high salinity; in addition, a hydrophobic association physical crosslinking point of the polymer can be reversibly damaged and reconstructed under shearing, effective tackifying can be carried out in a stratum, and the polymer is suitable for injection and oil displacement operation of an oil field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, in particular to a temperature-resistant and salt-tolerant polyacrylamide emulsion and a preparation method thereof. BACKGROUND

[0002] Hydrolyzed polyacrylamide (HPAM) is the most widely used polymer oil displacement agent in the current oil field enhanced oil recovery (EOR). However, the carboxyl group of the HPAM molecular chain is extremely sensitive to divalent cations (such as Ca 2+ , Mg 2+ ), which is easy to curl in high salinity formation water, resulting in a sharp decrease in solution viscosity. In addition, it is easy to break the molecular chain and further hydrolyze at high temperature, and has poor stability. These problems seriously limit the application of HPAM in high temperature and high salt reservoirs.

[0003] In the related art, a small amount of hydrophobic groups is generally introduced during the preparation of polyacrylamide to form a dynamic hydrophobic association network in water to improve the thickening performance and shear resistance; however, the general conventional hydrophobic groups not only have limited association ability, and the physical crosslinking network formed has insufficient strength, and in harsh environments of high temperature and high salt, the hydrophobic association is easily weakened or even destroyed, resulting in a sharp decrease in the thickening effect of the system, so that the thickening effect is not ideal.

[0004] Therefore, there is an urgent need to provide a temperature-resistant and salt-tolerant polyacrylamide emulsion and a preparation method thereof. SUMMARY

[0005] The present application provides a temperature-resistant and salt-tolerant polyacrylamide emulsion and a preparation method thereof, which can solve the problem of poor thickening effect and shear resistance of the existing polyacrylamide emulsion in a high temperature and high salt environment.

[0006] In a first aspect, the present application provides a preparation method of a temperature-resistant and salt-tolerant polyacrylamide emulsion, which comprises the following steps: (1) mixing acrylamide, anionic monomer, temperature-resistant and salt-tolerant monomer and structure regulator in water to obtain an aqueous phase mixed solution; (2) stirring and mixing white oil and a composite emulsifier, then mixing self-made hydrophobic association monomer and chain transfer agent to obtain an oil phase mixed solution; wherein the self-made hydrophobic association monomer has a hydrophobic pyrene group, a flexible spacer arm and a rigid benzene ring; (3) pouring the aqueous phase mixed solution into the oil phase mixed solution for stirring and emulsification, then adding an initiator aqueous solution to initiate the reaction after removing oxygen by nitrogen to obtain the temperature-resistant and salt-tolerant polyacrylamide emulsion.

[0007] Preferably, in step (1), the anionic monomer is at least one of 2-acrylamido-2-methylpropane sulfonic acid or sodium styrene sulfonate; the temperature-resistant and salt-resistant monomer is at least one of N-vinyl pyrrolidone or N,N-dimethyl acrylamide; the structure regulator is at least one of N-dodecyl acrylamide or N-n-butyl acrylamide.

[0008] Preferably, in step (2), the chain transfer agent is at least one of dodecanethiol or 3-mercaptopropionic acid.

[0009] Preferably, in step (2), the composite emulsifier is composed of isobutylene succinimide and Span-80; wherein the volume ratio of isobutylene succinimide and Span-80 is 1:1.

[0010] Preferably, in step (3), the aqueous initiator solution is ammonium persulfate and sodium bisulfite.

[0011] Preferably, in step (1), the pH value of the aqueous phase mixed solution is 7.0-7.2.

[0012] Preferably, the content of each reaction raw material is as follows in mass fraction: acrylamide 30-70 parts, anionic monomer 5-10 parts, temperature-resistant and salt-resistant monomer 1-5 parts, structure regulator 1-5 parts, and water 500 parts.

[0013] Preferably, in step (2), the mass ratio of white oil to composite emulsifier is (25-60):(3-5).

[0014] Preferably, in step (2), the mass ratio of self-made hydrophobic association monomer to acrylamide is (1-5):(30-70), and the mass ratio of chain transfer agent to acrylamide is (0.1-1):(30-70).

[0015] Preferably, in step (3), the stirring speed of emulsification gradually increases with time, the initial stirring speed is 300-500 rpm, the final stirring speed is 800-1000 rpm, and the stirring time is 30-40 min.

[0016] Preferably, the preparation method of the self-made hydrophobic association monomer comprises the following steps: (21) adding an alcohol compound containing a pyrene group and an organic phosphorus compound into a first solvent and mixing uniformly, adding a halogenated compound under ice water bath condition to carry out a reaction, and obtaining a first reaction product; (22) adding the first reaction product, a nitrophenol compound and an inorganic base into a second solvent and mixing uniformly, carrying out a reaction under a nitrogen atmosphere, and obtaining a second reaction product; (23) stirring and mixing the second reaction product solution and hyposulphite in an alkaline aqueous solution system, and obtaining a third reaction product after a reaction; (24) the third reaction product and an organic base are added into a third solvent and mixed, and an acylation solution is added dropwise under the condition of an ice-salt bath to react, so that the self-made hydrophobic association monomer is obtained.

[0017] Preferably, the pyrene group-containing alcohol compound is 1-pyrene butanol; the organic phosphorus compound is triphenylphosphine; the first solvent is anhydrous dichloromethane; and the halogenated compound is carbon tetrabromide.

[0018] Preferably, the nitrophenol compound is p-nitrophenol; the inorganic base is anhydrous potassium carbonate; and the second solvent is anhydrous N,N-dimethylformamide. Preferably, the alkaline aqueous sodium dithionite system is a sodium dithionite-sodium hydroxide aqueous solution system.

[0019] Preferably, the organic base is anhydrous triethylamine; the third solvent is anhydrous tetrahydrofuran; and the acylation solution is an acryloyl chloride-tetrahydrofuran solution.

[0020] Preferably, the molar ratio of the pyrene group-containing alcohol compound, the organic phosphorus compound and the halogenated compound is 1:(1.1-1.3):(1.2-1.4).

[0021] Preferably, the molar ratio of the pyrene group-containing alcohol compound, the nitrophenol compound and the inorganic base is 1:(1.05-1.25):(1.5-2.5).

[0022] Preferably, the molar ratio of the pyrene group-containing alcohol compound and the dithionite salt is 1:(5-7).

[0023] Preferably, the molar ratio of the pyrene group-containing alcohol compound, the organic base and the acylation solution is 1:(1.2-1.5):(1.15-1.25).

[0024] Preferably, in step (21), the reaction temperature is 20-35℃, and the reaction time is 4-6h.

[0025] Preferably, in step (22), the reaction is carried out in an oil bath at 85-95℃ for 7-9h.

[0026] Preferably, in step (23), the reaction temperature is 65-75℃, and the reaction time is 1.5-2.5h.

[0027] Preferably, in step (24), the dropping speed of the acylation solution is 2-3mL / min, the reaction temperature is 5-10℃, and the reaction time is 1.5-2.5h.

[0028] In a second aspect, the embodiments of the present application also provide an anti-temperature and salt-tolerant polyacrylamide emulsion prepared by the preparation method of any one of the first aspect.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects: (1) In this invention, a novel self-made hydrophobic associating monomer is first synthesized. This monomer has a pyrene group with strong hydrophobicity and fluorescence, a flexible spacer arm, and a rigid benzene ring. The pyrene group, with its large conjugated plane and extremely strong hydrophobicity, can form a hydrophobic association with a strength much higher than that of traditional alkyl chains, thereby endowing the polymer with excellent thickening ability, salt resistance, and temperature resistance. Subsequently, the hydrophobic associating monomer is mixed with acrylamide, anionic monomer, and temperature- and salt-resistant monomer to form an aqueous phase, and then mixed with an oil-containing phase and a composite emulsifier system to prepare a polyacrylamide emulsion through reverse emulsion polymerization. This makes the emulsion exhibit excellent comprehensive performance. On the one hand, the electrostatic repulsion synergistic effect of the strong hydrophobic associating monomer and the anionic monomer enables it to maintain an extremely high apparent viscosity under high temperature and high salinity conditions. On the other hand, the physical cross-linking network formed by dynamic hydrophobic association gives the polymer excellent shear dilution behavior, and the viscosity can be quickly restored after shear removal, which is beneficial for pumping and injection operations in oil fields. In addition, this monomer endows the polymer with potential fluorescence sensing capabilities and has extremely high association efficiency. Only a small amount needs to be added to significantly improve the polymer's temperature and salt resistance, resulting in outstanding cost-effectiveness.

[0030] (2) The polyacrylamide emulsion in this invention exhibits strong applicability under harsh oil reservoir conditions of high temperature and high salinity; the strongly hydrophobic association structure introduced into its polymer molecular chain endows the polymer with extremely strong hydrophobic association ability, and at the same time, it can produce synergistic effects with anionic monomers and temperature- and salt-resistant monomers, enabling the polymer to withstand high temperatures (>110℃) and high salinity (>8×10⁻⁶) conditions. 4 Even under conditions of mg / L, it can maintain extremely high apparent viscosity; in addition, the hydrophobic associative physical crosslinking points of this polymer can be reversibly destroyed and rebuilt under shear. Under high shear, the associative points are reversibly destroyed, exhibiting significant shear dilution behavior, which is beneficial for pumping; after shear is removed, the associative network is rapidly rebuilt, with a high viscosity recovery rate, ensuring effective viscosity enhancement in the formation, and is suitable for oilfield injection and oil displacement operations.

[0031] (3) The polyacrylamide emulsion prepared in this invention has excellent solubility. It can dissolve rapidly within minutes after contact with water, which greatly improves the construction efficiency at the oilfield site and completely solves the problem of pipeline blockage and raw material waste caused by the easy formation of "fish eyes" in powder products. In addition, it has outstanding stability and can be stored and transported for a long time, effectively avoiding the inherent problems of easy deterioration and degradation of polymer aqueous solutions and easy moisture absorption and clumping of powder products. Detailed Implementation

[0032] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are some embodiments but not all of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present application.

[0033] In order to solve the problem of poor thickening effect and poor shear resistance of the existing polyacrylamide emulsion in high-temperature and high-salt environment, the present application provides a preparation method of a temperature-resistant and salt-tolerant polyacrylamide emulsion, which comprises the following steps: (1) acrylamide, anionic monomer, temperature-resistant and salt-tolerant monomer and structure regulator are added into water and uniformly mixed to obtain an aqueous phase mixed solution; (2) white oil and composite emulsifier are stirred and uniformly mixed, and then self-made hydrophobic association monomer and chain transfer agent are uniformly mixed to obtain an oil phase mixed solution; wherein the self-made hydrophobic association monomer has a hydrophobic pyrene group, a flexible spacer arm and a rigid benzene ring; (3) the aqueous phase mixed solution is poured into the oil phase mixed solution for stirring and emulsification, nitrogen is used to remove oxygen, and then an initiator aqueous solution is added to initiate the reaction to obtain the temperature-resistant and salt-tolerant polyacrylamide emulsion.

[0034] In the embodiments of the present application, a self-made hydrophobic association monomer with novel structure is first synthesized, which has a strong hydrophobic and fluorescent pyrene group, a flexible spacer arm and a rigid benzene ring; wherein the pyrene group can form a hydrophobic association with a strength much higher than that of a traditional alkyl chain due to its large conjugated plane and strong hydrophobicity, thereby being capable of imparting the polymer with excellent thickening capacity, salt resistance and temperature resistance. Subsequently, the hydrophobic association monomer is mixed with acrylamide, anionic monomer and temperature-resistant and salt-tolerant monomer to form an aqueous phase, and is mixed with an oil phase and a composite emulsifier system to prepare a polyacrylamide emulsion by inverse emulsion polymerization, so that the emulsion exhibits excellent comprehensive performance. On the one hand, the electrostatic repulsion synergy of the strong hydrophobic association monomer and the anionic monomer enables the emulsion to maintain a very high apparent viscosity under high temperature and high salinity conditions; on the other hand, the physical crosslinking network composed of dynamic hydrophobic association enables the polymer to have excellent shear thinning behavior and the viscosity can be quickly restored after shear is removed, thereby being beneficial to pumping and injection operations in oilfields. In addition, the monomer also imparts the polymer with potential fluorescent sensing function and has very high association efficiency, and only a small amount of addition can significantly improve the temperature resistance and salt tolerance of the polymer, thereby having outstanding cost effectiveness.

[0035] According to some preferred embodiments, in step (1), the anionic monomer is at least one of 2-acrylamido-2-methylpropanesulfonic acid or sodium styrene sulfonate; the temperature-resistant and salt-tolerant monomer is at least one of N-vinylpyrrolidone or N,N-dimethylacrylamide; and the structure regulator is at least one of N-dodecylacrylamide or N-n-butylacrylamide.

[0036] According to some preferred embodiments, in step (2), the chain transfer agent is at least one of dodecanethiol or 3-mercaptopropionic acid; the composite emulsifier is composed of isobutylene succinimide and Span-80; and the volume ratio of isobutylene succinimide to Span-80 is 1:1; in step (3), the aqueous initiator solution is ammonium persulfate and sodium bisulfite, and the mass concentration of the aqueous initiator solution is preferably 1-2%, and the mass ratio of ammonium persulfate to sodium bisulfite is preferably 1:1.

[0037] According to some preferred embodiments, in step (3), the stirring speed of emulsification is gradually increased over time, the initial stirring speed is 300-500 rpm (for example, it can be 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm), the final stirring speed is 800-1000 rpm (for example, it can be 800 rpm, 850 rpm, 900 rpm, 950 rpm or 1000 rpm), and the stirring time is 30-40 min (for example, it can be 30 min, 32 min, 35 min, 38 min or 40 min); the reaction temperature is 40-50℃ (for example, it can be 40℃, 42℃, 45℃, 48℃ or 50℃), and the reaction time is 6-8 h (for example, it can be 6 h, 7 h or 8 h).

[0038] In the embodiments of the present application, first, acrylamide is stirred and mixed with an anionic monomer, a temperature-resistant and salt-tolerant monomer and a structure regulator in water to form an aqueous phase mixed solution, and an oil phase and a composite emulsifier are stirred at a temperature of 40-50℃ until completely dissolved, and then, after cooling to room temperature, a self-made hydrophobic associating monomer and a chain transfer agent are stirred and mixed, the lipophilic property of the self-made hydrophobic associating monomer is used to make it uniformly dispersed in the oil phase, so that it can more efficiently and controllably participate in the subsequent emulsification and polymerization; then, the aqueous phase is slowly poured into the oil phase under stirring, and a stable water-in-oil type milky white pre-emulsion is formed through programmed emulsification from low speed to high speed, in this inverse emulsion system, free radical copolymerization is carried out through an oxidation-reduction initiation system to form an amphiphilic random polyacrylamide copolymer with a specific sequence distribution. When the polymer is dissolved in water, the strong hydrophobic pyrene groups on the chain form a dynamic and reversible physical crosslinking network in water through hydrophobic association, so that the polyacrylamide emulsion has excellent temperature resistance, salt tolerance, super thickening capacity and excellent shear resistance and self-repairing performance.

[0039] According to some preferred embodiments, in step (1), the pH value of the aqueous phase mixed solution is 7.0-7.2 (for example, it can be 7.0, 7.1 or 7.2); the content of each reaction material is as follows in mass fraction: acrylamide 30-70 parts (for example, it can be 30 parts, 40 parts, 50 parts, 60 parts or 70 parts), anionic monomer 5-10 parts (for example, it can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts), temperature-resistant and salt-resistant monomer 1-5 parts (for example, it can be 1 part, 2 parts, 3 parts, 4 parts or 5 parts), structure regulator 1-5 parts (for example, it can be 1 part, 2 parts, 3 parts, 4 parts or 5 parts), water 500 parts.

[0040] In the embodiments of the present application, by controlling the content of each reaction monomer in the polymerization reaction, a polyacrylamide emulsion with excellent temperature resistance, salt resistance, viscosity increase performance and shear resistance can be prepared. Acrylamide serves as the main chain skeleton, providing long molecular chains and adsorption bridging capacity. An appropriate content of anionic monomer (such as a monomer containing a sulfonic acid group) can maintain the extended conformation of the polymer chain in salt water through strong hydration groups and electrostatic repulsion insensitive to salt, laying the structural foundation for strong hydrophobic association. However, if the content of the anionic monomer is too high, not only the cost will increase, but also the required segment mobility for hydrophobic association will be weakened, and the network formation efficiency will be affected. In addition, an appropriate content of temperature-resistant and salt-resistant monomer can further improve the temperature resistance, salt resistance and shear stability of the polymer. However, if the content of the temperature-resistant and salt-resistant monomer is too high, not only the cost will increase, but also the molecular weight will be hindered from increasing, and the viscosity of the final polymer will be affected. The synergistic effect of the structure regulator and the pyrene-based hydrophobic association monomer can reduce the association concentration and enhance the strength and toughness of the dynamic network. However, if the content of the structure regulator is too high, the core association structure will be destroyed, and the solution viscosity will decrease. Therefore, by optimizing the control of the content of each monomer, the flexibility, electrostatic repulsion and hydrophobic association of the polymer chain can be balanced optimally while the cost is low, so as to ensure the excellent comprehensive performance of the polyacrylamide emulsion.

[0041] According to some preferred embodiments, in step (2), the mass ratio of the white oil to the composite emulsifier is (25-60):(3-5) (for example, it can be 25:3, 25:4, 25:5, 30:3, 30:4, 30:5, 40:3, 40:4, 40:5, 50:3, 50:4, 50:5, 60:3, 60:4 or 60:5); the mass ratio of the self-made hydrophobic association monomer to the acrylamide is (1-5):(30-70) (for example, it can be 1:30, 2:30, 3:30, 4:30, 5:30, 1:40, 2:40, 3:40, 4:40, 5:40, 1:50, 2:50, 3:50, 4:50, 5:50, 1:60, 2:60, 3:60, 4:60, 5:60, 1:70, 2:70, 3:70, 4:70 or 5:40); and the mass ratio of the chain transfer agent to the acrylamide is (0.1-1):(30-70) (for example, it can be 0.1:30, 0.5:30, 0.8:30, 1:30, 0.1:40, 0.5:40, 0.8:40, 1:40, 0.1:50, 0.5:50, 0.8:50, 1:50, 0.1:60, 0.5:60, 0.8:60, 1:60, 0.1:70, 0.5:70, 0.8:70 or 1:70).

[0042] In the embodiments of the present application, after the white oil and the composite emulsifier are stirred and uniformly mixed, the self-made hydrophobic association monomer and the chain transfer agent are added into the oil phase in a proper amount and are uniformly mixed, which is beneficial to the higher efficiency of the hydrophobic association monomer and the chain transfer agent in the polymer molecular chain in the polymerization reaction. The addition of the chain transfer agent can actively control the molecular weight of the polymer. If the content of the hydrophobic association monomer is too high, not only the final polymer emulsion is difficult to dissolve, but also the stability of the water-in-oil emulsion is destroyed. If the content of the chain transfer agent is too high, the molecular weight of the polymer is too low, and the viscosity of the final polymer emulsion is low.

[0043] According to some preferred embodiments, the preparation method of the self-made hydrophobic association monomer comprises the following steps: (21) the alcohol compound containing pyrene group and the organic phosphorus compound are added into the first solvent and are uniformly mixed, and the halogenated compound is added under the condition of ice water bath to react, to obtain a first reaction product; (22) the first reaction product, the nitrophenol compound and the inorganic base are added into the second solvent and are uniformly mixed, and the reaction is carried out under the nitrogen atmosphere to obtain a second reaction product; (23) the second reaction product solution and the dithionite are stirred and uniformly mixed in the alkaline aqueous solution system, and after the reaction, a third reaction product is obtained; (24) the third reaction product and organic base are added into a third solvent and mixed, an acylation solution is added dropwise under the condition of ice-salt bath to carry out reaction, and the self-made hydrophobic association monomer is obtained.

[0044] According to some preferred embodiments, the pyrene group-containing alcohol compound is 1-pyrene butanol; the organic phosphorus compound is triphenylphosphine; the first solvent is anhydrous dichloromethane; the halogenated compound is carbon tetrabromide; the nitrophenol compound is p-nitrophenol; the inorganic base is anhydrous potassium carbonate; the second solvent is anhydrous N,N-dimethylformamide; the sodium hydrosulfite alkaline aqueous solution system is a sodium hydrosulfite sodium hydroxide aqueous solution system; the organic base is anhydrous triethylamine; the third solvent is anhydrous tetrahydrofuran; and the acylation solution is an acryloyl chloride tetrahydrofuran solution.

[0045] In the related art, hydrophobic association polymers usually use long-chain alkyl groups (such as C 12 -C 18As a hydrophobic monomer, however, its association ability is limited, and the hydrophobic association is easily destroyed in high temperature and high salt environment, and the thickening effect is not ideal. Based on this, in the embodiments of the present application, first, the alcohol compound containing pyrene group and the organic phosphorus compound are mixed in the first solvent, then the halogenated compound is added into the above mixed solution in batches under ice water bath condition for halogenation reaction, after the reaction is completed, the reaction liquid is washed with 50mL water, the organic phase is dried with anhydrous magnesium sulfate, filtered, rotary evaporated to remove the solvent, to obtain the crude product, then purified by column chromatography to obtain the first reaction product of light yellow solid; then, the product is mixed with nitrophenol compound and inorganic base in the second solvent, then stirred in the oil bath under nitrogen protection, after the reaction mixture is cooled, it is poured into 200mL ice water, yellow solid is precipitated, then filtered, the filter cake is washed with water, dried, recrystallized with ethanol to obtain the second reaction product of yellow needle-shaped crystal; then the second reaction product is dissolved in tetrahydrofuran, the dithionite salt is dissolved in sodium hydroxide aqueous solution, and the two solutions are mixed and reacted, then extracted with anhydrous dichloromethane three times after cooling, the organic phase is combined, washed with brine, dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation to obtain the crude product, which is purified by column chromatography (silica gel, petroleum ether: ethyl acetate = 3:1) to obtain the third reaction product of white solid; finally, the third reaction product and the organic base are dissolved in the third solvent, cooled to 0~5℃ in ice-salt bath, and the acylation solution is slowly added dropwise with constant pressure dropping funnel under stirring, first reacted at 5~10℃ for 1.5~2.5h, then the temperature is increased to 20~35℃ for continuous reaction for 1.5~2.5h, after the reaction is completed, the reaction liquid is poured into 100mL ice water, and solid is precipitated, then filtered, and the filter cake is washed with water until neutral; the crude product is dissolved in a small amount of anhydrous dichloromethane, purified by column chromatography (silica gel, petroleum ether: ethyl acetate = 4:1 to 2:1 gradient elution) to remove the polar by-product and residual raw material, and the target component is collected, then rotary evaporated to obtain the self-made hydrophobic association monomer of light yellow solid. The molecular structure of the self-made hydrophobic association monomer collects the hydrophobic pyrene group, the flexible spacer arm and the rigid benzene ring, the pyrene group can form a hydrophobic association with a strength much higher than that of the traditional alkyl chain by virtue of its large conjugated plane and strong hydrophobicity, thereby being able to endow the polymer with excellent thickening capacity, salt resistance and temperature resistance.

[0046] It should be noted that in the embodiments of the present application, in step (21), the mass-volume ratio of the alcohol compound containing pyrene group to the first solvent is (2.7~2.9):50g / mL; in step (22), the mass-volume ratio of the nitrophenol compound to the second solvent is (15~1.7):40g / mL; in step (23), the mass-volume ratio of the organic base to the third solvent is (1.5~1.6):50g / mL.

[0047] According to some preferred embodiments, the molar ratio of the pyrenyl-containing alcohol compound, the organic phosphorus compound and the halogenated compound is 1 : (1.1-1.3) : (1.2-1.4) (e.g., it can be 1 : 1.1 : 1.2, 1 : 1.2 : 1.3 or 1 : 1.3 : 1.4); the molar ratio of the pyrenyl-containing alcohol compound, the nitrophenol compound and the inorganic base is 1 : (1.05-1.25) : (1.5-2.5) (e.g., it can be 1 : 1.05 : 1.5, 1 : 1.1 : 2.0 or 1 : 1.25 : 2.5); the molar ratio of the pyrenyl-containing alcohol compound and the hydrosulfite is 1 : (5-7) (e.g., it can be 1 : 5, 1 : 6 or 1 : 7); the molar ratio of the pyrenyl-containing alcohol compound, the organic base, the acylation solution is 1 : (1.2-1.5) : (1.15-1.25) (e.g., it can be 1 : 1.2 : 1.15, 1 : 1.3 : 1.20, 1 : 1.5 : 1.2 or 1 : 1.5 : 1.25).

[0048] According to some preferred embodiments, in step (21), the temperature of the reaction is 20-35°C (e.g., it can be 20°C, 22°C, 25°C, 28°C, 30°C or 35°C) and the time is 4-6h (e.g., it can be 4h, 5h or 6h); in step (22), the reaction is carried out in an oil bath at 85-95°C (e.g., it can be 85°C, 90°C or 95°C) for 7-9h (e.g., it can be 7h, 8h or 9h); in step (23), the temperature of the reaction is 65-75°C (e.g., it can be 65°C, 70°C or 75°C) and the time is 1.5-2.5h (e.g., it can be 1.5h, 2.0h or 2.5h); in step (24), the dropping speed of the acylation solution is 2-3mL / min (e.g., it can be 2mL / min, 2.5mL / min or 3mL / min) and the temperature of the reaction is 5-10°C (e.g., it can be 5°C, 6°C, 7°C, 8°C, 9°C or 10°C) and the time is 1.5-2.5h (e.g., it can be 1.5h, 2.0h or 2.5h).

[0049] In the embodiment of the present application, by synergistically controlling the content of each reaction monomer in the reaction and the reaction temperature, a hydrophobic associating monomer with a hydrophobic pyrene group, a flexible spacer and a rigid benzene ring integrated on the molecular chain can be synthesized. In the monomer, the pyrene group can produce a strong π-π stacking effect, and the associating node formed by the effect has a firmness far exceeding that of the associating node relying on the traditional alkane hydrophobic effect. Even in a harsh environment of high temperature and high salt, the polymer network has excellent temperature-resistant and salt-resistant stability. More importantly, this force gives the polymer good self-repairing performance. When the associating node is destroyed by shear force and the pyrene groups are temporarily separated, the pyrene groups can re-dock and stack by virtue of their precise directional effect, efficiently rebuild the physical crosslinking network, and realize the rapid recovery of performance.

[0050] The embodiment of the present application also provides a temperature-resistant and salt-resistant polyacrylamide emulsion prepared by any one of the preparation methods.

[0051] The polyacrylamide emulsion in the embodiment of the present application has strong applicability under harsh reservoir conditions of high temperature and high salt. The strong hydrophobic associating structure introduced into the polymer molecular chain gives the polymer a strong hydrophobic associating ability, and at the same time, can produce a synergistic effect with an anionic monomer and a temperature-resistant and salt-resistant monomer, so that the polymer can still maintain a very high apparent viscosity under the condition of high temperature (> 110℃) and high salinity (> 8×10 4 mg / L). In addition, the hydrophobic associating physical crosslinking points of the polymer can be reversibly destroyed and rebuilt under shear. Under high shear action, the associating points are reversibly destroyed, showing a significant shear thinning behavior, which is beneficial to pumping. After the shear is removed, the associating network is quickly rebuilt, the viscosity recovery rate is high, the effective viscosity increase in the formation is ensured, and the product is suitable for injection and oil displacement operations in oilfields.

[0052] The polyacrylamide emulsion prepared in the embodiment of the present application has excellent solubility and can be rapidly dissolved in water within a few minutes, greatly improving the construction efficiency of oilfield sites and completely solving the problems of pipeline blockage and raw material waste caused by the powder product due to the generation of "fish eyes". Moreover, the stability is outstanding, and the product can be stored and transported for a long time, effectively avoiding the inherent problems of degradation of the polymer aqueous solution and moisture absorption and caking of the powder product.

[0053] In order to more clearly illustrate the technical solutions and advantages of the present application, the following examples are used to describe a temperature-resistant and salt-resistant polyacrylamide emulsion and a preparation method thereof in detail. In the following examples, the content of each reaction monomer is expressed by mass fraction.

[0054] Example 1: Preparation of self-made hydrophobic associating monomer: (21) Under a nitrogen atmosphere, 2.8 g of a pyrenyl-containing alcohol compound (1-pyrenylbutanol) and 3.15 g of an organophosphorus compound (triphenylphosphine) were mixed in 50 mL of a first solvent (anhydrous dichloromethane), and the mixture was cooled to 0°C using an ice water bath. Then, 4.31 g of a halogenated compound (carbon tetrabromide) was added to the mixture in portions, and the ice bath was removed, and the temperature was slowly increased to 25°C to perform the reaction for 5 h. After the reaction was completed, the reaction solution was washed with 50 mL of water, and the organic phase was dried over anhydrous magnesium sulfate, filtered, and distilled under reduced pressure to remove the solvent, thereby obtaining a crude product. The crude product was purified by column chromatography to obtain a first reaction product in the form of a light yellow solid; (22) In a round-bottom flask, 3.47 g of the first reaction product, 1.67 g of a nitrophenol compound (p-nitrophenol), and 2.76 g of an inorganic base (anhydrous potassium carbonate) were mixed in 40 mL of a second solvent (anhydrous N,N-dimethylformamide). Then, the mixture was stirred at 90°C in an oil bath under a nitrogen atmosphere to perform the reaction for 8 h. After the reaction mixture was cooled, it was poured into 200 mL of ice water, and a yellow solid was precipitated. The solid was filtered, washed with water, and dried. Then, the solid was recrystallized from ethanol to obtain a second reaction product in the form of yellow needle-shaped crystals; (23) 4.10 g of the second reaction product was dissolved in 30 mL of tetrahydrofuran to obtain a second reaction product solution. Then, 10.45 g of sodium hydrosulfite was dissolved in 30 mL of an aqueous sodium hydroxide solution. The two solutions were mixed and stirred, and the mixture was stirred vigorously at 70°C for 2 h. After the mixture was cooled, it was extracted with anhydrous dichloromethane three times, and the combined organic phase was washed with brine, dried over anhydrous sodium sulfate, and distilled under reduced pressure to remove the solvent, thereby obtaining a crude product. The crude product was purified by column chromatography (silica gel, petroleum ether: ethyl acetate = 3:1) to obtain a third reaction product in the form of a white solid; (24) 3.79 g of the third reaction product and 1.52 g of an organic base (anhydrous triethylamine) were mixed in 50 mL of a third solvent (anhydrous tetrahydrofuran), and the mixture was cooled to 5°C using an ice-salt bath. Then, an acylation solution (1.09 g of acryloyl chloride dissolved in 5 mL of anhydrous tetrahydrofuran) was slowly added dropwise at a rate of 2 mL / min using a constant-pressure dropping funnel. After the dropwise addition was completed, the mixture was reacted for 2 h, and then the temperature was slowly increased to 25°C to perform the reaction for 2 h. After the reaction was completed, the reaction solution was poured into 100 mL of ice water, and a solid was precipitated. The solid was filtered, washed with water until the filtrate became neutral, and dissolved in a small amount of anhydrous dichloromethane. The solution was purified by column chromatography (silica gel, petroleum ether: ethyl acetate = 4:1 to 2:1 gradient elution) to remove polar by-products and residual starting materials. The target component was collected, and distilled under reduced pressure to obtain a self-made hydrophobically associating monomer in the form of a light yellow solid; (1) In a beaker, 500 parts of deionized water, 60 parts of acrylamide, 7 parts of anionic monomer (2-acrylamido-2-methylpropanesulfonic acid), 3 parts of temperature-resistant and salt-resistant monomer (N-vinylpyrrolidone) and 3 parts of structure regulator (N-dodecyl acrylamide) were added in sequence, and completely dissolved under magnetic stirring to form a clear solution. The pH was adjusted to 7.0 with dilute sodium hydroxide solution to obtain an aqueous phase mixture solution; (2) In a 500 mL four-necked flask (equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen inlet tube), 40 parts of white oil and 4 parts of a composite emulsifier (spans-80 and polyisobutylene succinimide in a volume ratio of 1:1) were added, slowly warmed to 40-50°C, stirred until completely dissolved, cooled to room temperature 25°C, and then 1 part of the above self-made hydrophobic association monomer and 0.5 parts of a chain transfer agent (dodecanethiol) were added and mixed to obtain an oil phase mixture solution; (3) The aqueous phase mixture solution was slowly poured into the oil phase mixture solution, and mechanical stirring was started for emulsification. First, the stirring speed was 300 rpm, and then it was gradually increased to 800 rpm. The emulsification was carried out at room temperature 25°C for 35 min, and then the temperature of the reaction system was increased to 45°C. After 30 min of nitrogen deoxygenation, 0.03 parts of a 1% mass concentration initiator aqueous solution (mass ratio of ammonium persulfate and sodium bisulfite 1:1) was added to initiate the reaction. After 7 h of reaction, the system was cooled to room temperature to obtain a temperature-resistant and salt-resistant polyacrylamide emulsion.

[0055] Example 2: Example 2 is basically the same as Example 1, except that in step (2), the amount of self-made hydrophobic association monomer added is 3 parts.

[0056] Example 3: Example 3 is basically the same as Example 1, except that in step (2), the amount of self-made hydrophobic association monomer added is 5 parts.

[0057] Example 4: Example 4 is basically the same as Example 1, except that in step (1), the amount of anionic monomer (2-acrylamido-2-methylpropanesulfonic acid) added is 10 parts.

[0058] Example 5: Example 5 is basically the same as Example 1, except that in step (1), the amount of temperature-resistant and salt-resistant monomer (N-vinylpyrrolidone) added is 5 parts.

[0059] Example 6: Example 6 is basically the same as Example 1, except that in step (1), the amount of anionic monomer added is 15 parts.

[0060] Example 7: Example 7 is substantially the same as Example 1, except that in step (1), the amount of temperature-resistant and salt-tolerant monomer added is 8 parts.

[0061] Example 8: Example 8 is substantially the same as Example 1, except that in step (2), the amount of self-made hydrophobic association monomer added is 8 parts.

[0062] Comparative Example 1 Comparative Example 1 is substantially the same as Example 1, except that in step (2), no self-made hydrophobic association monomer is added.

[0063] Comparative Example 2 Comparative Example 2 is substantially the same as Example 1, except that in step (1), no anionic monomer (2-acrylamido-2-methylpropane sulfonic acid) is added.

[0064] Comparative Example 3 Comparative Example 3 is substantially the same as Example 1, except that in step (1), no temperature-resistant and salt-tolerant monomer (N-vinyl pyrrolidone) is added.

[0065] Comparative Example 4 Comparative Example 4 is substantially the same as Example 1, except that in step (2), the self-made hydrophobic association monomer is replaced by the same amount of dodecyl methacrylate.

[0066] The performance of the temperature-resistant and salt-tolerant polyacrylamide emulsion samples (hereinafter referred to as samples) provided by the examples and comparative examples is tested, and the test results are shown in Table 1 below: The test method is as follows: unless otherwise specified, the performance test of the samples in the examples of the present application is carried out under the following uniform conditions: the concentration of the polymer solution is 3000 mg / L, the solvent is simulated salt water with a total mineralization degree of 8 x 10 4 mg / L (wherein, Ca 2+ , Mg 2+ is 3000-4000 mg / L); Determination of apparent viscosity: a Brookfield DV3T rheometer is used for determination, with a UL Adapter rotor system, 16.0 mL of the above prepared sample test solution is carefully injected into the sample cup of the rheometer to avoid air bubbles; the temperature is set to 110°C, the shear rate is 7.34 s -1 , and the viscosity reading is continuously measured until it is stable, and the stable viscosity value is recorded, with the unit of mPa·s, which is the apparent viscosity of the sample solution under high temperature and high salt conditions. Each sample is tested in triplicate, and the average value is taken as the final result.

[0067] Shear recovery rate determination: according to the apparent viscosity determination procedure described above, the initial viscosity of the sample solution is measured at 110℃ and a shear rate of 7.34s -1 -1, the shear rate is instantaneously increased to 300s -1 -1, and the solution is continuously sheared under this high shear condition for 5min to destroy the hydrophobic association physical crosslinking network in the solution, then the shear rate is immediately restored to 7.34s -1 -1, and the change of viscosity with time is continuously recorded until the viscosity value reaches a new stable state, and the stable viscosity value is recorded as η2; shear recovery rate (%) = (η2 / η1) x 100%.

[0068] Viscosity retention rate determination: 50mL of freshly prepared sample solution is placed in a sealed stainless steel aging tank with a polytetrafluoroethylene liner, and the aging tank is placed in a constant temperature air drying oven at 110℃ for continuous aging for 30 days; after aging, the aging tank is taken out and cooled to room temperature, the aged solution is shaken, and the above apparent viscosity determination procedure is repeated to measure the viscosity after aging; wherein the viscosity retention rate (%) = (apparent viscosity after aging / apparent viscosity before aging) x 100%.

[0069] Table 1 Note: “--” in the table indicates that the performance cannot be determined As can be seen from Table 1, the polyacrylamide emulsion prepared in the embodiments of the present application has good thickening performance and shear resistance under high temperature and high salt.

[0070] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a temperature- and salt-resistant polyacrylamide emulsion, characterized in that, The preparation method includes the following steps: (1) Add acrylamide, anionic monomer, temperature- and salt-resistant monomer and structure modifier to water and mix well to obtain an aqueous mixed solution; (2) After stirring and mixing the white oil and the composite emulsifier, add the self-made hydrophobic associating monomer and the chain transfer agent and mix well to obtain an oil phase mixed solution; wherein the self-made hydrophobic associating monomer has a hydrophobic pyrene group, a flexible spacer arm and a rigid benzene ring; (3) The aqueous phase mixture is poured into the oil phase mixture and stirred and emulsified. After nitrogen is introduced to remove oxygen, an initiator aqueous solution is added to initiate the reaction, and the temperature-resistant and salt-resistant polyacrylamide emulsion is obtained.

2. The preparation method according to claim 1, characterized in that, In step (1), the anionic monomer is at least one of 2-acrylamido-2-methylpropanesulfonic acid or sodium styrene sulfonate; The temperature- and salt-resistant monomer is at least one of N-vinylpyrrolidone or N,N-dimethylacrylamide; The structure modifier is at least one of N-dodecylacrylamide or N-n-butylacrylamide.

3. The preparation method according to claim 1, characterized in that, In step (2), the chain transfer agent is at least one of dodecyl mercaptohydric acid or 3-mercaptopropionic acid; the composite emulsifier is composed of isobutylene succinimide and Span-80; wherein the volume ratio of isobutylene succinimide to Span-80 is 1:

1. In step (3), the initiator aqueous solution is ammonium persulfate and sodium bisulfite.

4. The preparation method according to claim 1, characterized in that, In step (1), the pH value of the aqueous mixed solution is 7.0~7.2; and / or The contents of each reaction raw material by mass parts are as follows: 30-70 parts acrylamide, 5-10 parts anionic monomer, 1-5 parts temperature and salt resistant monomer, 1-5 parts structure modifier, and 500 parts water.

5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of white oil to composite emulsifier is (25~60):(3~5); and / or The mass ratio of the self-made hydrophobic associating monomer to acrylamide was (1~5):(30~70), and the mass ratio of the chain transfer agent to acrylamide was (0.1~1):(30~70).

6. The preparation method according to claim 1, characterized in that, In step (3), the stirring speed during emulsification gradually increases over time, with an initial stirring speed of 300-500 rpm and a final stirring speed of 800-1000 rpm, and a stirring time of 30-40 min; and / or The reaction is carried out at a temperature of 40-50°C for 6-8 hours.

7. The preparation method according to claim 1, characterized in that, The preparation method of the self-made hydrophobic associating monomer includes the following steps: (21) Add the pyrene-containing alcohol and organophosphorus compound to the first solvent and mix well. Add the halogenated compound under ice-water bath conditions to react and obtain the first reaction product. Preferably, the pyrene-containing alcohol is 1-pyrenebutanol; the organophosphorus compound is triphenylphosphine; the first solvent is anhydrous dichloromethane; and the halogenated compound is carbon tetrabromide. (22) The first reaction product, nitrophenolic compound and inorganic base are added to the second solvent and mixed well. The reaction is carried out under nitrogen atmosphere to obtain the second reaction product. Preferably, the nitrophenol compound is p-nitrophenol; the inorganic base is anhydrous potassium carbonate; and the second solvent is anhydrous N,N-dimethylformamide. (23) The solution of the second reaction product and dithionite are stirred and mixed in an alkaline aqueous solution system, and the third reaction product is obtained after the reaction. Preferably, the alkaline aqueous solution system of sodium dithionite is an aqueous solution system of sodium dithionite and sodium hydroxide. (24) The third reaction product and the organic base are added to the third solvent and mixed well. The acylation solution is added dropwise under ice-salt bath conditions to carry out the reaction and obtain the self-made hydrophobic associative monomer. The organic base is anhydrous triethylamine; the third solvent is anhydrous tetrahydrofuran; and the acylation solution is a tetrahydrofuran solution of acryloyl chloride.

8. The preparation method according to claim 7, characterized in that, The molar ratio of pyrene-containing alcohols, organophosphorus compounds, and halogenated compounds is 1:(1.1~1.3):(1.2~1.4). The molar ratio of pyrene-containing alcohols, nitrophenols, and inorganic bases is 1:(1.05~1.25):(1.5~2.5). The molar ratio of pyrene-containing alcohols to dithionites is 1:(5~7); and / or The molar ratio of pyrene-containing alcohols, organic bases, and acylation solutions is 1:(1.2~1.5):(1.15~1.25).

9. The preparation method according to claim 7, characterized in that, In step (21), the reaction temperature is 20~35℃ and the time is 4~6h; In step (22), the reaction is carried out in an oil bath at 85~95℃ for 7~9h; In step (23), the reaction temperature is 65~75℃ and the time is 1.5~2.5h; and / or In step (24), the dropping rate of the acylation solution is 2~3 mL / min, the reaction temperature is 5~10℃, and the time is 1.5~2.5 h.

10. A temperature- and salt-resistant polyacrylamide emulsion, characterized in that, It is prepared by any one of claims 1 to 9.

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