Multifunctional oil displacement polymer and preparation method thereof

Abstract

The invention discloses a multifunctional oil-displacing polymer and a preparation method thereof. Specifically, ricinoleic acid is used for synthesizing a hydrophobic monomer, an acid and alkali resistant functional monomer and a thick oil emulsifying monomer; the hydrophobic monomer, the acid and alkali resistant functional monomer and the thick oil emulsifying monomer are copolymerized with acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, and a copolymerized reaction product is the multifunctional oil displacement polymer; the polymer shows excellent temperature resistance, salt resistance and thickened oil emulsifying capacity under different pH conditions, and a multifunctional integrated solution is provided for improving the recovery ratio of an oil field.

Description

Technical Field

[0001] This disclosure relates to the field of polymer flooding technology for oilfields, specifically a multifunctional oil displacement polymer with high temperature resistance, high salt resistance and emulsification ability, and a method for preparing the same. Background Technology

[0002] In recent years, as my country's oilfield development has gradually entered the high water-cut stage, tertiary oil recovery technology has become the mainstream method for improving crude oil recovery efficiency. Among the many tertiary oil recovery technologies, polymer flooding technology has become the most crucial means due to its wide application and significant effects. This technology mainly improves crude oil recovery by increasing the viscosity of the displacing fluid and expanding its effective range. Acrylamide (AM) has become one of the most frequently used water-soluble polymers in tertiary oil recovery due to its high monomer activity, simple polymerization process, low cost, and ease of synthesizing high molecular weight polymers. However, HPAM's shortcomings in salt resistance, high temperature stability, and shear stability lead to a rapid decrease in its viscosity in the oil reservoir. In addition, due to the excessively high viscosity of some heavy oils, polymer solutions alone are insufficient for extraction, requiring emulsification for effective oil displacement. Furthermore, changes in the pH value of the reservoir environment also significantly affect polymer performance. Therefore, developing a multifunctional oil displacement polymer that adapts to different pH environments and possesses high temperature resistance, high salt resistance, and emulsification capabilities has significant practical importance and market potential. Summary of the Invention

[0003] In view of this, this disclosure provides a multifunctional oil displacement polymer and its preparation method, which solves the problems of current oil displacement polymers in terms of salt resistance, high temperature stability and shear stability, as well as their inability to adapt to heavy oil environments, i.e., different pH environments.

[0004] The molecular design concept of the multifunctional oil displacement polymer of this invention is as follows: Acrylamide (AM) and acrylic acid (AA) serve as hydrophilic units, providing a high viscosity basis for the polymer. 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) is used as a key monomer to improve temperature and salt resistance. A hydrophobic associative crosslinking network is constructed using a hydrophobic monomer (HM) synthesized from methyl ricinoleate to enhance the polymer's temperature and salt resistance. A cationic polymeric surfactant monomer (CSM) synthesized from ricinoleic acid provides emulsification in acidic environments and enhances the polymer's salt and temperature resistance in alkaline environments. Simultaneously, a nonionic polymeric surfactant monomer (NSM) synthesized from ricinoleic acid endows the polymer with excellent heavy oil emulsifying ability.

[0005] Based on the above-mentioned inventive concept, in a first aspect, the multifunctional oil displacement polymer disclosed herein has the following molecular structural formula:

[0006]

[0007] In the formula: p:q:r:s:t:u=1:(0.2~0.4):(0.02~0.04):(0.005~0.02):(0.005~0.02):(0.0025~0.01) in molar ratio; n is .

[0008] Secondly, the method for preparing the multifunctional oil displacement polymer described in the first aspect includes:

[0009] Hydrophobic monomers, acid and alkali resistant functional monomers, and heavy oil emulsifying monomers were synthesized using ricinoleic acid.

[0010] The hydrophobic monomer, acid and alkali resistant functional monomer, heavy oil emulsifying monomer, acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid are copolymerized, and the copolymerization reaction product is the multifunctional oil displacement polymer.

[0011] In this disclosure and possible embodiments, the method for synthesizing hydrophobic monomers using ricinoleic acid includes:

[0012] Methyl ricinoleate and triethylamine were dissolved in dichloromethane to form the first solution system;

[0013] Acryloyl chloride is dissolved in dichloromethane to form a second solution system;

[0014] The reaction product of the second solution system and the first solution system is the hydrophobic monomer.

[0015] In this disclosure and possible embodiments, 1 part of methyl ricinoleate and 2 parts of triethylamine are dissolved in dichloromethane to prepare a dichloromethane solution with a mass concentration of 5% to 10% as the first solution system;

[0016] Dissolve 1.2 parts of acryloyl chloride in dichloromethane to prepare a dichloromethane solution with a mass concentration of 5% to 10% as the second solution system;

[0017] At 0℃~5℃, the second solution system is added dropwise to the first solution system, and the reaction is stirred for 12h~24h. After the reaction is completed, the hydrophobic monomer is obtained by rotary evaporation for 2h~4h.

[0018] In this disclosure and possible embodiments, the method for synthesizing acid- and alkali-resistant functional monomers using ricinoleic acid includes:

[0019] Castor oil acid and N,N-dimethyl-1,3-propanediamine were dissolved in dichloromethane to form a first solution; 1,3-dicyclohexylcarbodiimide and 4-dimethylaminopyridine were dissolved in dichloromethane to form a second solution; the product of the reaction between the first solution and the second solution was used as an intermediate product.

[0020] The intermediate product is reacted with a dichloromethane solution of acryloyl chloride to obtain the acid and alkali resistant functional monomer.

[0021] In this disclosure and possible embodiments, 1 part of ricinoleic acid and 1.2 parts of N,N-dimethyl-1,3-propanediamine are dissolved in dichloromethane to prepare a first solution with a mass concentration of 5% to 10%; 2 parts of 1,3-dicyclohexylcarbodiimide and 0.2 parts of 4-dimethylaminopyridine are dissolved in dichloromethane to prepare a second solution with a mass concentration of 5% to 10%; the second solution is added dropwise to the first solution at 20°C to 25°C, and the reaction is stirred for 12 to 24 hours. After the reaction is completed, the mixture is filtered and rotary evaporated for 2 to 4 hours to obtain the intermediate product.

[0022] One part of the intermediate product was dissolved in dichloromethane to prepare an intermediate product solution with a mass concentration of 5% to 10%; 1.2 parts of acryloyl chloride were dissolved in dichloromethane to prepare an acryloyl chloride solution with a mass concentration of 5% to 10%; the acryloyl chloride solution was added dropwise to the intermediate product solution at 5℃ to 15℃, and the reaction was stirred for 36h to 48h. After the reaction was completed, the mixture was rotary evaporated for 2h to 4h to obtain the acid and alkali resistant functional monomer.

[0023] In this disclosure and possible embodiments, the method for synthesizing heavy oil emulsifying monomers using ricinoleic acid includes:

[0024] Castor oil acid and polyoxyethylene monomethyl ether are dissolved in dichloromethane to form a first system; 1,3-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are dissolved in dichloromethane to form a second system; the product of the reaction between the first system and the second system is used as an intermediate;

[0025] The intermediate is reacted with a dichloromethane solution of acryloyl chloride to obtain the heavy oil emulsifying monomer.

[0026] In this disclosure and possible embodiments, 1 part of castor oil acid and 1.2 parts of polyoxyethylene alkyl ether are dissolved in dichloromethane to prepare the first system with a mass concentration of 5% to 10%; 2 parts of 1,3-dicyclohexylcarbodiimide and 0.2 parts of 4-dimethylaminopyridine are dissolved in dichloromethane to prepare the second system with a mass concentration of 5% to 10%; the second system is added dropwise to the first system at 20°C to 25°C, and the reaction is stirred for 12 h to 24 h. After the reaction is completed, the mixture is filtered and rotary evaporated for 2 h to 4 h to obtain the intermediate.

[0027] One part of the intermediate was dissolved in dichloromethane to prepare an intermediate solution with a mass concentration of 5% to 10%; 1.2 parts of acryloyl chloride were dissolved in dichloromethane to prepare an acryloyl chloride solution with a mass concentration of 5% to 10%; the acryloyl chloride solution was added dropwise to the intermediate solution at 5°C to 15°C, and the reaction was stirred for 36 h to 48 h. After the reaction was completed, the mixture was rotary evaporated for 2 h to 4 h to obtain the heavy oil emulsifying monomer.

[0028] In this disclosure and possible embodiments, the molar ratio of each monomer is: acrylamide: acrylic acid: 2-acrylamide-2-methylpropanesulfonic acid: hydrophobic monomer: acid and alkali resistant functional monomer: heavy oil emulsifying monomer = 1: (0.2~0.4): (0.02~0.04): (0.005~0.02): (0.005~0.02): (0.0025~0.01); and / or,

[0029] The copolymerization method includes:

[0030] The monomers are mixed to prepare a total monomer solution of 20wt% to 30wt%, and urea of ​​2wt% to 5wt% of the total monomers and sodium dodecyl sulfate of 5wt% to 15wt% of the total monomers are dissolved in the total monomer solution.

[0031] After adjusting the pH of the system to 7.5–8.0 and the temperature to 0–10°C, add 0.02%–0.1% of the total monomer mass of a redox initiator and perform an adiabatic reaction for 8–12 hours. The reaction product is the multifunctional oil displacement polymer.

[0032] In this disclosure and possible embodiments, the redox initiator is ammonium persulfate oxidant and sodium bisulfite reducing agent, wherein the mass ratio of the oxidant to the reducing agent is 1:(3-1); and / or,

[0033] After adding the redox initiator, nitrogen gas is purged into the system for 0.25 h to 0.5 h; and / or,

[0034] The reaction product is a polymer block, which is crushed into polymer particles; the polymer particles are then dried, granulated, and sieved to obtain the multifunctional oil-displacing polymer powder.

[0035] This disclosure has the following beneficial effects:

[0036] The molecular design principle of the multifunctional oil displacement polymer of this invention is based on the synthesis of three functional monomers using ricinoleic acid and its derivatives. Specifically, a hydrophobic monomer (HM) synthesized from methyl ricinoleate is used to construct a hydrophobic associative crosslinking network, enhancing the polymer's temperature and salt resistance. A cationic polymeric surfactant monomer (CSM) synthesized from ricinoleic acid serves as an acid and alkali resistant functional monomer, providing emulsification in acidic environments and enhancing the polymer's salt and temperature resistance in alkaline environments. A nonionic polymeric surfactant monomer (NSM) synthesized from ricinoleic acid serves as a heavy oil emulsifying monomer, endowing the polymer with excellent heavy oil emulsifying capabilities. Acrylamide (AM) and acrylic acid (AA) serve as hydrophilic units, providing the polymer with a high viscosity base. 2-Acrylamide-2-methylpropanesulfonic acid (AMPS) serves as a key monomer for improving temperature and salt resistance. In summary, the multifunctional oil displacement polymer of this invention exhibits excellent temperature resistance, salt resistance, and heavy oil emulsifying capabilities under different pH conditions, providing a multifunctional integrated solution for enhancing oil recovery in oilfields.

[0037] In addition, the multifunctional oil displacement polymer of the present invention has the following properties:

[0038] (1) Reduction of interfacial tension: The functional monomers disclosed herein exhibit excellent ability to reduce the interfacial tension between oil and water. At 45°C, only 0.5% of the functional monomer solution can reduce the interfacial tension between oil and water to 1.78 × 10⁻⁶. -2 mN / m;

[0039] (2) Rapid solubility: The polymer disclosed herein also exhibits remarkable rapid solubility, capable of dissolving rapidly in brine at 45°C in just 18 minutes.

[0040] (3) Increased viscosity: At 45℃ and pH=5, the viscosity of the polymer solution disclosed herein is 45.9 mPa·s; when the polymer brine solution is emulsified and mixed with crude oil at a 1:1 ratio, the separation of the aqueous phase after emulsification is observed. After 72 hours, only 6.0% of the aqueous phase is separated. At 45℃ and pH=10, the viscosity of the polymer solution disclosed herein is 68.1 mPa·s; when the polymer brine solution is emulsified and mixed with crude oil at a 1:1 ratio, the separation of the aqueous phase after emulsification is observed. After 72 hours, only 8.2% of the aqueous phase is separated.

[0041] These properties make the polymer disclosed herein a potential application in oilfield enhanced oil recovery. Attached Figure Description

[0042] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0043] Figure 1 This is the molecular structural formula of the multifunctional oil displacement polymer disclosed in this paper;

[0044] Figure 2 This refers to the dissolution time of the polymer in Example 1 of this disclosure;

[0045] Figure 3 This is a graph showing the viscosity of the polymer in Example 1 of this disclosure at different concentrations as a function of temperature;

[0046] Figure 4 This is a graph showing the change in viscosity of the polymer solution in Example 1 of this disclosure as a function of aging days;

[0047] Figure 5 This is a functional relationship between the oil recovery rate and displacement pressure of the polymer solution (concentration 0.3%) in Example 1 of this disclosure and the cumulative injection volume;

[0048] Figure 6-1 , 6-2 These are the relationships between the oil recovery rate and injection pressure of the polymer in Example 1 of this disclosure and the injection volume. Detailed Implementation

[0049] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0050] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0051] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples.

[0052] To address the need for improved performance in terms of temperature resistance, salt resistance, and emulsification of polyacrylamide polymers, this disclosure presents the following molecular design for polyacrylamide polymers: acrylamide (AM) and acrylic acid (AA) are used as hydrophilic units, providing a high-viscosity foundation for the polymer; 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is used as a key monomer to improve temperature and salt resistance; a hydrophobic associative crosslinking network is constructed using a hydrophobic monomer (HM) synthesized from methyl ricinoleate to enhance the polymer's temperature and salt resistance; a cationic polymeric surfactant monomer (CSM) synthesized from ricinoleic acid is used as an acid and alkali resistant functional monomer to provide emulsification in acidic environments and enhance the polymer's salt and temperature resistance in alkaline environments; simultaneously, a nonionic polymeric surfactant monomer (NSM) synthesized from ricinoleic acid is used as a heavy oil emulsifying monomer to endow the polymer with excellent heavy oil emulsifying ability.

[0053] Based on the above molecular design, this disclosure discloses a method for preparing a multifunctional oil-displacing polymer using ricinoleic acid, the specific steps of which are as follows:

[0054] 1. Preparation of functional monomers

[0055] ①Preparation of hydrophobic monomer HM

[0056] The synthetic route for the hydrophobic monomer HM described in this disclosure is as follows:

[0057]

[0058] Following the above synthetic route, the specific preparation process is as follows:

[0059] Weigh 1 part methyl ricinoleate and 2 parts triethylamine into a flask, and dissolve them in dichloromethane to a concentration of 5%–10%. Then weigh 1.2 parts acryloyl chloride and dissolve them in dichloromethane to a concentration of 5%–10%. At 0℃–5℃, add the dichloromethane-dissolved acryloyl chloride solution dropwise into the flask and stir the reaction for 12h–24h. After the reaction is complete, rotary evaporate for 2h–4h to obtain the hydrophobic monomer HM.

[0060] ② Preparation of acid and alkali resistant functional monomer CSM

[0061] The synthetic route of the acid and alkali resistant functional monomer CSM described in this disclosure is as follows:

[0062]

[0063] Following the above synthetic route, the specific preparation process is as follows:

[0064] a) Weigh 1 part ricinoleic acid and 1.2 parts N,N-dimethyl-1,3-propanediamine and add them to a flask, followed by dichloromethane, to a total concentration of 5%–10%. Dissolve 2 parts condensing agent 1,3-dicyclohexylcarbodiimide and 0.2 parts catalyst 4-dimethylaminopyridine in dichloromethane, to a total concentration of 5%–10%. At 20℃–25℃, add the dichloromethane solution containing the condensing agent and catalyst dropwise to the flask and stir the reaction for 12h–24h. After the reaction is complete, filter and rotary evaporate for 2h–4h to obtain intermediate product A.

[0065] (b) Weigh 1 part of intermediate product A and dissolve it in dichloromethane to a concentration of 5%–10%. Then weigh 1.2 parts of acryloyl chloride and dissolve it in dichloromethane to a concentration of 5%–10%. At 5℃–15℃, add the acryloyl chloride solution dissolved in dichloromethane dropwise to a flask and stir the reaction for 36h–48h. After the reaction is complete, rotary evaporate for 2h–4h to obtain the acid and alkali resistant functional monomer CSM.

[0066] ③ Preparation of heavy oil emulsifying monomer NSM

[0067] The synthetic route of the heavy oil emulsifying monomer NSM described in this disclosure is as follows:

[0068]

[0069] Following the above synthetic route, the specific preparation process is as follows:

[0070] a) Weigh 1 part ricinoleic acid and 1.2 parts polyoxyethylene monomethyl ether and add them to a flask, along with dichloromethane, to a total concentration of 5%–10%. Dissolve 2 parts condensing agent 1,3-dicyclohexylcarbodiimide and 0.2 parts catalyst 4-dimethylaminopyridine in dichloromethane, to a total concentration of 5%–10%. At 20℃–25℃, add the dichloromethane solution containing the condensing agent and catalyst dropwise to the flask and stir the reaction for 12h–24h. After the reaction is complete, filter and rotary evaporate for 2h–4h to obtain intermediate product B.

[0071] (b) Weigh 1 part of intermediate product B and dissolve it in dichloromethane to a concentration of 5%–10%. Then weigh 1.2 parts of acryloyl chloride and dissolve it in dichloromethane to a concentration of 5%–10%. At 5℃–15℃, add the acryloyl chloride solution dissolved in dichloromethane dropwise to a flask and stir the reaction for 36h–48h. After the reaction is complete, rotary evaporate for 2h–4h to obtain the heavy oil emulsifying monomer NSM.

[0072] 2. Synthesis of Multifunctional Oil Displacement Polymers

[0073] ① Polymer synthesis

[0074] The synthetic route of the multifunctional oil displacement polymer described in this disclosure is as follows:

[0075]

[0076] Following the above synthetic route, the specific preparation process is as follows:

[0077] Weigh out a certain mass of AM, AA, AMPS, and functional monomers HM, CSM, and NSM and place them in a beaker containing ultrapure water. Stir and dissolve. The total monomer mass fraction is 20wt%–30wt%, and the molar ratio of each monomer is AM:AA:AMPS:HM:CSM:NSM = 1:(0.2–0.4):(0.02–0.04):(0.005–0.02):(0.005–0.02):(0.0025–0.01). Simultaneously, add 2wt%–5wt% urea and 5wt%–15wt% sodium dodecyl sulfate to the system for dissolution. Then, adjust the pH of the solution to 7.5–8.0 using NaOH solution (30wt%). The mixture is transferred to a reactor, and the temperature is adjusted to 0℃~10℃. A redox initiator is then added, with ammonium persulfate as the oxidant and sodium bisulfite as the reductant. The mass ratio of oxidant to reductant is 1:(3~1). The amount of initiator added is 0.02%~0.1% of the total monomer mass. The temperature control is then turned off, and nitrogen gas is introduced for 0.25h~0.5h. The elastic block is obtained after an adiabatic reaction of 8h~12h.

[0078] ② Polymer post-processing

[0079] The obtained polymer blocks were pulverized using a granulator to obtain polymer granules, which were then dried at 40–60°C for 2 hours to obtain dried polymer particles. The dried polymer was then granulated using a pulverizer and sieved to obtain the target polymer powder. The molecular structure of the target polymer is as follows: Figure 1 As shown.

[0080] Example 1:

[0081] 1. Preparation of functional monomers

[0082] ①Preparation of hydrophobic monomer HM

[0083] Weigh 3.12 g of methyl ricinoleate and 2.02 g of triethylamine into a flask, and dissolve them in 80 mL of dichloromethane. Then weigh 1.08 g of acryloyl chloride and dissolve it in 20 mL of dichloromethane. At 5 °C, add the acryloyl chloride solution dissolved in dichloromethane dropwise into the flask and stir the reaction for 24 h. After the reaction is complete, rotary evaporate for 4 h to obtain the hydrophobic monomer HM.

[0084] ② Preparation of acid and alkali resistant functional monomer CSM

[0085] a) Weigh 3.12 g of ricinoleic acid and 1.22 g of N,N-dimethyl-1,3-propanediamine and add them to a flask, along with 80 ml of dichloromethane. Dissolve 4.12 g of the condensing agent 1,3-dicyclohexylcarbodiimide and 0.24 g of the catalyst 4-dimethylaminopyridine in the 80 ml of dichloromethane. At 25 °C, add the dichloromethane solution containing the condensing agent and catalyst dropwise to the flask and stir the reaction for 24 h. After the reaction is complete, filter and rotary evaporate for 2 h–4 h to obtain intermediate product A.

[0086] (b) Weigh 3.96 g of intermediate product A and dissolve it in 80 ml of dichloromethane. Then weigh 1.08 g of acryloyl chloride and dissolve it in 20 ml of dichloromethane. At 10 °C, add the acryloyl chloride solution dissolved in dichloromethane dropwise to a flask and stir the reaction for 48 h. After the reaction is complete, rotary evaporate for 4 h to obtain the acid and alkali resistant functional monomer CSM.

[0087] ③ Preparation of heavy oil emulsifying monomer NSM

[0088] a) Weigh 3.12 g of ricinoleic acid and 0.88 g of polyoxyethylene monomethyl ether and add them to a flask, along with 70 ml of dichloromethane. Dissolve 4.12 g of the condensing agent 1,3-dicyclohexylcarbodiimide and 0.24 g of the catalyst 4-dimethylaminopyridine in 80 ml of dichloromethane. At 25 °C, add the dichloromethane solution containing the condensing agent and catalyst dropwise to the flask and stir the reaction for 24 h. After the reaction is complete, filter and rotary evaporate for 4 h to obtain intermediate product B.

[0089] (b) Weigh 3.20 g of intermediate product B and dissolve it in 60 ml of dichloromethane. Then weigh 1.08 g of acryloyl chloride and dissolve it in 30 ml of dichloromethane. At 10 °C, add the acryloyl chloride solution dissolved in dichloromethane dropwise to a flask and stir the reaction for 48 h. After the reaction is complete, rotary evaporate for 4 h to obtain the heavy oil emulsifying monomer NSM.

[0090] 2. Preparation of multifunctional oil displacement polymers

[0091] Weigh 150g AM, 45g AA, 13g AMPS, and functional monomers 8g HM, 9g CSM, and 9g NSM into a beaker containing ultrapure water and stir to dissolve. The total monomer mass fraction is 25wt%. Add 10g urea and 18g sodium dodecyl sulfate sequentially, then adjust the pH of the solution to 7.5 with NaOH solution (30wt%). Transfer the solution to a reactor, adjust the temperature to 5°C, and add 0.04g ammonium persulfate and 0.08g sodium bisulfite. Turn off the temperature control and purge with nitrogen for 0.5h. After adiabatic reaction for 12h, an elastic block is obtained. After granulation, drying, pulverizing, and sieving, the multifunctional oil-displacing polymer dry powder of Example 1 is obtained.

[0092] 3. Performance testing of multifunctional oil displacement polymers and HPAM (commercial)

[0093] The multifunctional oil displacement polymer dry powder of Example 1 was prepared into a polymer solution. The preparation method of the polymer solution is to dilute the impurities with a solution of clean and impure. Specifically, the polymer was prepared into a polymer stock solution of 5000 mg / L using 950 mg / L NaCl saline solution, and then the polymer solution concentration was diluted to 1000 mg / L using 4000 mg / L NaCl saline solution.

[0094] ① Heavy oil emulsification performance: At 45℃ and pH=5, the viscosity of the polymer solution was 59.3 mPa·s. When the polymer brine solution was emulsified with crude oil at a 1:1 ratio, the separation of the aqueous phase was observed. After 72 hours, only 5.8% of the aqueous phase separated, while HPAM showed no significant heavy oil emulsification effect. At 45℃ and pH=10, the viscosity of the polymer solution was 88.7 mPa·s. When the polymer brine solution was emulsified with crude oil at a 1:1 ratio, the separation of the aqueous phase was observed. After 72 hours, only 8.3% of the aqueous phase separated, while HPAM showed no significant heavy oil emulsification effect.

[0095] ② Salt resistance: Figure 2 The effect of different NaCl concentrations on the apparent viscosity of the polymer of Example 1 and HPAM is shown. With increasing NaCl concentration, the apparent viscosity of both the polymer of Example 1 and HPAM showed a decreasing trend, but the salt resistance of the polymer of Example 1 was significantly better than that of HPAM.

[0096] ③ Solubility test: At room temperature, the polymer (0.02g) of Example 1 was dissolved in 20g of salt water. The dissolution time was approximately 0.8 hours. Figure 3 The shorter the dissolution time, the faster the dissolution rate, and the better the water solubility. Clearly, the polymer in Example 1 can dissolve well in the brine of the Daqing oil reservoir.

[0097] ④ The effect of temperature: such as Figure 4 As shown, in the brine of the Daqing oil reservoir, the viscosity-temperature curves of different polymer concentrations (Example 1) show that the viscosity of the polymer solution decreases with increasing temperature, exhibiting the 'thermal thinning' phenomenon similar to most water-soluble polymers, following the Arrhenius law.

[0098] ④Aging stability: An aging test was conducted in a 45℃ oven; Figure 5 The effect of different aging times on the apparent viscosity of the polymer was demonstrated. The results showed that the polymer in Example 1 still had a viscosity of over 50 mPa·s after aging at 45°C for 60 days, exhibiting excellent long-term thermal stability, while the viscosity of HPAM was only about 15 mPa·s after aging for 69 days.

[0099] ⑤ Enhanced oil recovery experiment: This experiment was conducted using a multi-functional oil displacement device. Figure 6-1 , 6-2 The effects of the polymer in Example 1 on oil recovery and injection pressure as a function of injection volume are shown. The results indicate that the polymer in Example 1, at a concentration of 0.3%, increased oil recovery by 10.22%, demonstrating a good oil displacement effect, while HPAM increased recovery by 8.21% under the same conditions.

[0100] Example 2:

[0101] Weigh 150g AM, 45g AA, 13g AMPS, and functional monomers 4g HM, 9g CSM, and 9g NSM (these three functional monomers are the same as in Example 1) and place them in a beaker containing ultrapure water. Stir and dissolve to achieve a total monomer mass fraction of 25wt%. Add 10g urea and 18g sodium dodecyl sulfate sequentially. Then adjust the pH of the solution to 7.5 with NaOH solution (30wt%). Transfer the solution to a reactor, adjust the temperature to 5°C, and add 0.04g ammonium persulfate and 0.08g sodium bisulfite. Turn off the temperature control and purge with nitrogen for 0.5h. After adiabatic reaction for 12h, an elastic block is obtained. After granulation, drying, pulverizing, and sieving, the multifunctional oil-displacing polymer dry powder of Example 2 is obtained.

[0102] Following the polymer solution preparation method of Example 1, the polymer solution of Example 2 was prepared. At 45°C and pH=5, the viscosity of the polymer solution was 45.9 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 6.0% of the aqueous phase had separated. At 45°C and pH=10, the viscosity of the polymer solution was 68.1 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 8.2% of the aqueous phase had separated.

[0103] Example 3:

[0104] Weigh 150g AM, 45g AA, 13g AMPS, and functional monomers 8g HM, 4.5g CSM, and 9g NSM (these three functional monomers are the same as in Example 1) and place them in a beaker containing ultrapure water. Stir and dissolve to achieve a total monomer mass fraction of 25wt%. Add 10g urea and 18g sodium dodecyl sulfate sequentially. Then adjust the pH of the solution to 7.5 with NaOH solution (30wt%). Transfer the solution to a reactor, adjust the temperature to 5°C, and add 0.04g ammonium persulfate and 0.08g sodium bisulfite. Turn off the temperature control and purge with nitrogen for 0.5h. After adiabatic reaction for 12h, an elastic block is obtained. After granulation, drying, pulverizing, and sieving, the multifunctional oil-displacing polymer dry powder of Example 3 is obtained.

[0105] Following the polymer solution preparation method of Example 1, the polymer solution of Example 3 was prepared. At 45°C and pH=5, the viscosity of the polymer solution was 57.2 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 6.9% of the aqueous phase had separated. At 45°C and pH=10, the viscosity of the polymer solution was 76.1 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 8.4% of the aqueous phase had separated.

[0106] Example 4:

[0107] Weigh 150g AM, 45g AA, 13g AMPS, and functional monomers 8g HM, 9g CSM, and 4.5g NSM into a beaker containing ultrapure water and stir to dissolve. The total monomer mass fraction is 25wt%. Add 10g urea and 18g sodium dodecyl sulfate sequentially, then adjust the pH of the solution to 7.5 with NaOH solution (30wt%). Transfer the solution to a reactor, adjust the temperature to 5°C, and add 0.04g ammonium persulfate and 0.08g sodium bisulfite. Turn off the temperature control and purge with nitrogen for 0.5h. After adiabatic reaction for 12h, an elastic block is obtained. After granulation, drying, pulverizing, and sieving, the multifunctional oil-displacing polymer dry powder of Example 4 is obtained.

[0108] Following the polymer solution preparation method of Example 1, the polymer solution of Example 4 was prepared. At 45°C and pH=5, the viscosity of the polymer solution was 56.8 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 7.2% of the aqueous phase had separated. At 45°C and pH=10, the viscosity of the polymer solution was 85.4 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 9.6% of the aqueous phase had separated.

[0109] Example 5:

[0110] Weigh 150g AM, 45g AA, 13g AMPS, and functional monomers 8g HM, 9g CSM, and 9g NSM into a beaker containing ultrapure water and stir to dissolve. The total monomer mass fraction is 30wt%. Add 10g urea and 18g sodium dodecyl sulfate sequentially, then adjust the pH of the solution to 7.5 with NaOH solution (30wt%). Transfer the solution to a reactor, adjust the temperature to 5°C, and add 0.04g ammonium persulfate and 0.08g sodium bisulfite. Turn off the temperature control and purge with nitrogen for 0.5h. After adiabatic reaction for 12h, an elastic block is obtained. After granulation, drying, pulverizing, and sieving, the multifunctional oil-displacing polymer dry powder of Example 5 is obtained.

[0111] Following the polymer solution preparation method of Example 1, the polymer solution of Example 5 was prepared. At 45°C and pH=5, the viscosity of the polymer solution was 64.3 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 5.7% of the aqueous phase had separated. At 45°C and pH=10, the viscosity of the polymer solution was 90.2 mPa·s. The polymer brine solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed. After 72 hours, only 8.5% of the aqueous phase had separated.

[0112] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A multifunctional oil displacement polymer, characterized in that, Its molecular structural formula is: In the formula: p:q:r:s:t:u = 1:(0.2~0.4):(0.02~0.04):(0.005~0.02):(0.005~0.02):(0.0025~0.01); n is between 3 and 11.

2. The preparation method of the multifunctional oil displacement polymer according to claim 1, characterized in that, include: Hydrophobic monomers, acid and alkali resistant functional monomers, and heavy oil emulsifying monomers were synthesized using ricinoleic acid. The hydrophobic monomer, acid and alkali resistant functional monomer, heavy oil emulsifying monomer, acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid are copolymerized, and the copolymerization reaction product is the multifunctional oil displacement polymer.

3. The preparation method of the multifunctional oil displacement polymer according to claim 2, characterized in that, The method for synthesizing hydrophobic monomers using ricinoleic acid includes: Methyl ricinoleate and triethylamine were dissolved in dichloromethane to form the first solution system; Acryloyl chloride is dissolved in dichloromethane to form a second solution system; The reaction product of the second solution system and the first solution system is the hydrophobic monomer.

4. The preparation method of the multifunctional oil displacement polymer according to claim 3, characterized in that: One part of methyl ricinoleate and two parts of triethylamine were dissolved in dichloromethane to prepare a dichloromethane solution with a mass concentration of 5% to 10% as the first solution system; Dissolve 1.2 parts of acryloyl chloride in dichloromethane to prepare a dichloromethane solution with a mass concentration of 5% to 10% as the second solution system; At 0℃~5℃, the second solution system is added dropwise to the first solution system, and the reaction is stirred for 12h~24h. After the reaction is completed, the hydrophobic monomer is obtained by rotary evaporation for 2h~4h.

5. The preparation method of the multifunctional oil displacement polymer according to claim 2, characterized in that, The method for synthesizing acid- and alkali-resistant functional monomers using ricinoleic acid includes: Castor oil acid and N,N-dimethyl-1,3-propanediamine were dissolved in dichloromethane to form a first solution; 1,3-dicyclohexylcarbodiimide and 4-dimethylaminopyridine were dissolved in dichloromethane to form a second solution; the product of the reaction between the first solution and the second solution was used as an intermediate product. The intermediate product is reacted with a dichloromethane solution of acryloyl chloride to obtain the acid and alkali resistant functional monomer.

6. The method for preparing the multifunctional oil displacement polymer according to claim 5, characterized in that: One part of ricinoleic acid and 1.2 parts of N,N-dimethyl-1,3-propanediamine were dissolved in dichloromethane to prepare a first solution with a mass concentration of 5% to 10%. Two parts of 1,3-dicyclohexylcarbodiimide and 0.2 parts of 4-dimethylaminopyridine were dissolved in dichloromethane to prepare a second solution with a mass concentration of 5% to 10%. The second solution was added dropwise to the first solution at 20°C to 25°C, and the reaction was stirred for 12 to 24 hours. After the reaction was completed, the mixture was filtered and rotary evaporated for 2 to 4 hours to obtain the intermediate product. One part of the intermediate product was dissolved in dichloromethane to prepare an intermediate product solution with a mass concentration of 5% to 10%; 1.2 parts of acryloyl chloride were dissolved in dichloromethane to prepare an acryloyl chloride solution with a mass concentration of 5% to 10%; the acryloyl chloride solution was added dropwise to the intermediate product solution at 5℃ to 15℃, and the reaction was stirred for 36h to 48h. After the reaction was completed, the mixture was rotary evaporated for 2h to 4h to obtain the acid and alkali resistant functional monomer.

7. The preparation method of the multifunctional oil displacement polymer according to claim 2, characterized in that, The method for synthesizing heavy oil emulsifying monomers using ricinoleic acid includes: Castor oil acid and polyoxyethylene monomethyl ether are dissolved in dichloromethane to form a first system; 1,3-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are dissolved in dichloromethane to form a second system; the product of the reaction between the first system and the second system is used as an intermediate; The intermediate is reacted with a dichloromethane solution of acryloyl chloride to obtain the heavy oil emulsifying monomer.

8. The method for preparing the multifunctional oil displacement polymer according to claim 7, characterized in that: One part of ricinoleic acid and 1.2 parts of polyoxyethylene alkyl ether were dissolved in dichloromethane to prepare the first system with a mass concentration of 5% to 10%; two parts of 1,3-dicyclohexylcarbodiimide and 0.2 parts of 4-dimethylaminopyridine were dissolved in dichloromethane to prepare the second system with a mass concentration of 5% to 10%; the second system was added dropwise to the first system at 20°C to 25°C, and the reaction was stirred for 12 h to 24 h. After the reaction was completed, the mixture was filtered and rotary evaporated for 2 h to 4 h to obtain the intermediate. One part of the intermediate was dissolved in dichloromethane to prepare an intermediate solution with a mass concentration of 5% to 10%; 1.2 parts of acryloyl chloride were dissolved in dichloromethane to prepare an acryloyl chloride solution with a mass concentration of 5% to 10%; the acryloyl chloride solution was added dropwise to the intermediate solution at 5°C to 15°C, and the reaction was stirred for 36 h to 48 h. After the reaction was completed, the mixture was rotary evaporated for 2 h to 4 h to obtain the heavy oil emulsifying monomer.

9. The method for preparing the multifunctional oil displacement polymer according to any one of claims 2-8, characterized in that: The molar ratio of each monomer is as follows: acrylamide: acrylic acid: 2-acrylamide-2-methylpropanesulfonic acid: hydrophobic monomer: acid and alkali resistant functional monomer: heavy oil emulsifying monomer = 1: (0.2~0.4): (0.02~0.04): (0.005~0.02): (0.005~0.02): (0.0025~0.01); And / or, The copolymerization method includes: The monomers are mixed to prepare a total monomer solution of 20wt% to 30wt%, and urea of ​​2wt% to 5wt% of the total monomers and sodium dodecyl sulfate of 5wt% to 15wt% of the total monomers are dissolved in the total monomer solution. After adjusting the pH of the system to 7.5–8.0 and the temperature to 0–10°C, add 0.02%–0.1% of the total monomer mass of a redox initiator and perform an adiabatic reaction for 8–12 hours. The reaction product is the multifunctional oil displacement polymer.

10. The method for preparing the multifunctional oil displacement polymer according to claim 9, characterized in that, The redox initiator is ammonium persulfate oxidant and sodium bisulfite reducing agent, wherein the mass ratio of the oxidant to the reducing agent is 1:(3-1); and / or, After adding the redox initiator, nitrogen gas is purged into the system for 0.25 h to 0.5 h; and / or, The reaction product is a polymer block, which is crushed into polymer particles; the polymer particles are then dried, granulated, and sieved to obtain the multifunctional oil-displacing polymer powder.

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