Polymers with viscosity-reducing function, their preparation methods and applications

Abstract

This invention relates to the field of oilfield development technology, and discloses a polymer with viscosity-reducing function, its preparation method, and its application. The polymer has the structural units shown in Formulas 1 and 2. Oil displacement agents containing this polymer exhibit high static viscosity reduction, high oil recovery, salt resistance, and high-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a polymer with viscosity-reducing function, its preparation method, and its application. Background Technology

[0002] my country's oilfield development process involves multiple extraction stages, and with each stage, the recovery rate decreases. Currently, most major oilfields are in the later stages of extraction. Therefore, to improve the recovery rate of existing oilfields, oil extraction technology is receiving increasing attention, with the development of displacement agents used in the extraction process attracting growing interest from major oil companies and researchers.

[0003] Chemical flooding is a major method in oil recovery technology. Currently, most commonly used displacement agents are applied to light oils, while systems for heavy oil are relatively rare. However, displacement is the most efficient development method for heavy oil due to its high viscosity and poor flowability. Compared to displacement agents used for light oils, heavy oil displacement systems are mostly based on polymers. By artificially injecting water-soluble high-molecular-weight polymers, the viscosity of the aqueous phase is increased, the permeability of the aqueous phase is reduced, and the oil-water viscosity ratio is improved, thereby enhancing oil recovery. However, given the complex reservoir conditions, current polymer displacement agents still face several challenges in their adaptive application: 1. They are prone to hydrolysis at high temperatures; 2. They are easily broken down by shearing; 3. They easily flocculate upon contact with calcium ions. These problems can easily lead to a sharp drop in the viscosity of the polymer solution, thus negating its viscosity-enhancing effect on the aqueous phase. Therefore, developing temperature-resistant, shear-resistant, and salt-resistant polymers is essential to achieving the effectiveness of heavy oil displacement agents. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of poor viscosity reduction effect caused by the easy hydrolysis, chain breakage and flocculation of polymer flooding agents at high temperature and calcium ions in the prior art, and to provide a polymer with viscosity reduction function, its preparation method and application.

[0005] To achieve the above objectives, the present invention provides a polymer with viscosity-reducing function, the polymer having the structural units shown in Formula 1 and Formula 2:

[0006]

[0007] Wherein, R, R2, and R3 are each independently selected from H or C1-C6 alkyl groups; M is selected from H or alkali metal elements; and x is selected from integers from 4 to 18.

[0008] The mass ratio of the structural unit shown in Equation 1 to the structural unit shown in Equation 2 is 1:0.1-5;

[0009] The polymer has a weight-average molecular weight of 600,000 to 1,200,000.

[0010] A second aspect of the present invention provides a method for preparing a polymer with viscosity-reducing function, the method comprising: mixing a compound represented by Formula I and a compound represented by Formula II in the presence of a solvent, an initiator and a catalyst and subjecting them to a polymerization reaction;

[0011]

[0012] Wherein, the weight ratio of the compound shown in Formula I to the compound shown in Formula II is 1:0.1-5; the definitions of R, R2, R3, x and M are the same as those described in the first aspect of the present invention.

[0013] A third aspect of the present invention provides a polymer obtained by the method described in the second aspect of the present invention.

[0014] The fourth aspect of the present invention provides the use of the polymers described in the first aspect and / or the third aspect of the present invention in oil displacement agents.

[0015] Through the above technical solution, the present invention has the following beneficial effects:

[0016] 1. At 80℃ and Ca 2+ In an aqueous solution system with a concentration of 5000 mg / L, the viscosity can reach above 25 mPa·s when the content of the polymer described in this invention is 0.5-1 wt%.

[0017] 2. The polymer described in this invention has a high static viscosity reduction rate of over 90% for heavy oil with a viscosity of 1000-2000 mPa·s.

[0018] 3. The polymer described in this invention is used as an oil displacement agent, and its core displacement recovery rate is above 60%.

[0019] 4. The polymer described in this invention has excellent salt resistance and temperature resistance. Specifically, it can withstand a calcium ion concentration of up to 5000 mg / L and a high temperature of 80°C. Attached Figure Description

[0020] Figure 1 The results are from the sand tube displacement experiment of the product of Example 3. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] As mentioned above, one aspect of the present invention provides a polymer with viscosity-reducing function, characterized in that the polymer has the structural units shown in Formula 1 and Formula 2:

[0023]

[0024] Wherein, R, R2, and R3 are each independently selected from H or C1-C6 alkyl (especially straight-chain alkyl); M is selected from H or an alkali metal element; x is selected from an integer from 4 to 18;

[0025] The mass ratio of the structural unit shown in Equation 1 to the structural unit shown in Equation 2 is 1:0.1-5;

[0026] The polymer has a weight-average molecular weight of 600,000 to 1,200,000.

[0027] In some embodiments of the present invention, preferably, the molecular weight distribution index (the ratio of weight-average molecular weight to number-average molecular weight) of the polymer is 1.2-2.2.

[0028] In some embodiments of the present invention, preferably, R is selected from H, methyl, ethyl, propyl, butyl, or pentyl.

[0029] In some embodiments of the present invention, x is preferably selected from an integer from 4 to 16.

[0030] In some embodiments of the present invention, preferably, R2 and R3 are each independently selected from H, methyl or ethyl.

[0031] In some embodiments of the present invention, preferably, M is H or Na.

[0032] In some embodiments of the present invention, preferably, R is H, methyl, or ethyl.

[0033] In some embodiments of the present invention, x is preferably selected from an integer from 4 to 12.

[0034] In some embodiments of the present invention, preferably, R2 and R3 are each independently selected from H or methyl.

[0035] In some embodiments of the present invention, preferably, M is Na.

[0036] In some embodiments of the present invention, preferably, the weight ratio of the structural unit shown in Formula 1 to the structural unit shown in Formula 2 is 1:0.3-2.

[0037] In some embodiments of the present invention, preferably, the weight ratio of the structural unit shown in Formula 1 to the structural unit shown in Formula 2 is 1:0.5-1.5.

[0038] In some embodiments of the present invention, preferably, the weight-average molecular weight of the polymer is 650,000 to 1,100,000.

[0039] In some embodiments of the present invention, preferably, the molecular weight distribution index of the polymer is 1.2-2.

[0040] In some embodiments of the present invention, preferably, the weight-average molecular weight of the polymer is 700,000 to 1,000,000.

[0041] In some embodiments of the present invention, preferably, the molecular weight distribution index of the polymer is 1.2-1.6.

[0042] In this invention, conventional methods in the prior art can be used to test the content of each structural unit in the polymer, such as infrared spectroscopy, nuclear magnetic resonance, and the amount of monomers fed during polymerization. Preferably, the amount of monomers fed is used to determine the content of each structural unit in the polymer. Specifically, the actual feeding ratio of each monomer participating in polymerization is determined by testing the content of unreacted monomers, thereby determining the content of each structural unit in the polymer. Furthermore, in this invention, the content of each unreacted monomer in the polymer is found to be below 0.02% by weight, indicating that almost all monomers participate in the polymerization reaction. Specifically, the content of the residual monomers is determined using liquid chromatography.

[0043] A second aspect of the present invention provides a method for preparing a polymer with viscosity-reducing function, characterized in that the method comprises: mixing a compound represented by Formula I and a compound represented by Formula II in the presence of a solvent, an initiator and a catalyst and subjecting them to a polymerization reaction;

[0044]

[0045] Wherein, the weight ratio of the compound shown in Formula I to the compound shown in Formula II is 1:0.1-5; the definitions of R, R2, R3, x and M are the same as those described in the first aspect of the present invention.

[0046] In some embodiments of the present invention, preferably, the solvent is selected from solvents miscible with water, and more preferably at least one of water, tetrahydrofuran, and dioxane.

[0047] In some embodiments of the present invention, preferably, the initiator is selected from at least one of azo compounds, persulfides, and peroxides.

[0048] In some embodiments of the present invention, preferably, the initiator is an azo compound.

[0049] In some embodiments of the present invention, preferably, the initiator is selected from at least one of azobisisobutyramidine hydrochloride (AIBA), azobisisobutyronitrile (ABVN), and azobisisobutyramidazole hydrochloride (AIBI).

[0050] In some embodiments of the present invention, preferably, the catalyst is selected from organometallic compounds and / or metal halides.

[0051] In some embodiments of the present invention, preferably, the catalyst is selected from at least one of zirconium acetylacetonate (Zr(acac)4), triethylaluminum (AlEt3), titanium tetrachloride and copper bromide.

[0052] In some embodiments of the present invention, preferably, the weight ratio of the compound represented by Formula I to the compound represented by Formula II is 1:0.3-2.

[0053] In some embodiments of the present invention, preferably, the weight ratio of the compound represented by Formula I to the compound represented by Formula II is 1:0.5-1.5.

[0054] In some embodiments of the present invention, preferably, the weight ratio of the initiator to the compound represented by Formula I is 1:30-250, more preferably 1:100-200.

[0055] In some embodiments of the present invention, preferably, the weight ratio of the catalyst to the compound represented by Formula I is 1:30-250, more preferably 1:100-200.

[0056] In some embodiments of the present invention, preferably, the temperature of the polymer reaction is 50-90°C, more preferably 60-80°C.

[0057] In some embodiments of the present invention, preferably, the polymer reaction time is 12-48 hours, more preferably 18-30 hours.

[0058] A third aspect of the present invention provides a polymer obtained by the method described in the second aspect of the present invention.

[0059] The fourth aspect of the present invention provides the use of the polymers described in the first aspect and / or the third aspect of the present invention in oil displacement agents.

[0060] The present invention will be described in detail below through examples. In the following examples, the compound represented by Formula I is a commercially available product of Beijing Baomo Biotechnology Co., Ltd.; the compound represented by Formula II is a commercially available product of Aladdin Company with CAS number: 15214-89-8 (R2 and R3 are both methyl, M is H); AIBA is a commercially available product of Aladdin Company with CAS number: 78-67-1; Zr(acac)4 is a commercially available product of Aladdin Company with CAS number: 17501-44-9; ABVN is a commercially available product of Aladdin Company with CAS number: 4419-11-8; TiCl4 is a commercially available product of Sigma-Aldrich Company with CAS number: 7550-45-0; AIBI is a commercially available product of Chengdu McCarthy Chemical Co., Ltd. with CAS number: 27776-21-2; and AlEt3 is a commercially available product of Wuhan Hongde Yuexin Pharmaceutical Technology Co., Ltd. with CAS number: 97-93-8.

[0061] Example 1

[0062] 30g of compound I (x=4) and 20g of compound II were dissolved in 100g of tetrahydrofuran and 40g of deionized water, respectively. After thorough mixing, the solutions were sequentially poured into 500mL three-necked round-bottom flasks equipped with a magnetic stir bar, thermometer, and nitrogen circulation system. Nitrogen gas was continuously purged at room temperature for 30min under stirring. Then, 0.2g of initiator AIBA and 0.2g of catalyst Zr(acac)4 were added sequentially, and the mixture was heated to 60℃ and reacted for 24 hours. The gel was then removed from the flask, cut into small pieces, dried at 180℃ for 4 hours, and granulated to obtain product 1 with a yield of 94.3%.

[0063] Examples 2-8

[0064] The polymer was prepared according to the method of Example 1, except that the amounts or values ​​of the compounds shown in Formula I, Formula II, X, AIBA and Zr(acac)4 were different, as shown in Table 1.

[0065] Table 1

[0066]

[0067]

[0068] Example 9

[0069] 30g of compound I (x=4) and 20g of compound II were dissolved in 100g of dioxane and 100g of deionized water, respectively. After thorough mixing, the solutions were sequentially poured into 500mL three-necked round-bottom flasks equipped with a magnetic stir bar, thermometer, and nitrogen circulation system. Nitrogen gas was continuously purged at room temperature for 30min under stirring. Then, 0.2g of initiator ABVN and 0.2g of catalyst TiCl4 were added sequentially, and the mixture was heated to 70℃ and reacted for 24 hours. The gel was then removed from the flask, cut into small pieces, dried at 180℃ for 4 hours, and granulated to obtain product 9, with a yield of 93.8%.

[0070] Example 10

[0071] 40g of compound I (x=4) and 40g of compound II were dissolved in 100g of dioxane and 100g of deionized water, respectively. After thorough mixing, the solutions were sequentially poured into 500mL three-necked round-bottom flasks equipped with a magnetic stir bar, thermometer, and nitrogen circulation system. Nitrogen gas was continuously purged at room temperature for 30min under stirring. Then, 0.4g of initiator AIBI and 0.4g of catalyst AlEt3 were added sequentially, and the mixture was heated to 80℃ and reacted for 24 hours. The gel was then removed from the flask, cut into small pieces, dried at 180℃ for 4 hours, and granulated to obtain product 10, with a yield of 90.1%.

[0072] The experimental results above show that, under the conditions described in Examples 1-10, both compounds represented by Formula I and II can undergo polymerization. In Examples 5 and 6, the weight ratios of initiator to Formula I compound were 1:250 and 1:33, respectively, and the weight ratios of catalyst to Formula I compound were 1:250 and 1:33, respectively, with yields of 80.2% and 80.8%, respectively. Compared with other examples where the yields were all above 90%, the preferred initiator-to-Formula I compound ratios of 1:100-1:200 and catalyst-to-Formula I compound ratios can further improve the yield of the polymerization product. Compared with Examples 1-3, the smaller the value of x in Formula I compound, the higher the yield of the polymerization product.

[0073] Example 11

[0074] The polymer was prepared according to the method of Example 1, except that 30 g of compound I and 60 g of compound II were used to obtain product 11.

[0075] Example 12

[0076] The polymer was prepared according to the method of Example 1, except that 30 g of compound I and 9 g of compound II were used to obtain product 12.

[0077] Example 13

[0078] The polymer was prepared according to the method of Example 1, except that the amount of compound I was 25g and the amount of compound II was 12g, to obtain product 13.

[0079] Comparative Example 1

[0080] The polymer was prepared according to the method of Example 1, except that 50g of compound I and 3g of compound II were used to obtain product D1.

[0081] Comparative Example 2

[0082] The polymer was prepared according to the method of Example 1, except that the amount of compound shown in Formula I was 5g and the amount of compound shown in Formula II was 40g.

[0083] Comparative Example 3

[0084] The polymer was prepared according to the method of Example 1, except that in the compound represented by Formula I, R is a straight-chain C. 10 H 21 Product D3 was obtained.

[0085] Test Example 1

[0086] The weight-average molecular weight and molecular weight distribution index of each example and comparative example were determined by gel permeation chromatography, and the results are shown in Table 2.

[0087] Prepare CaCl2 as Ca 2+ A 5000 mg / L aqueous solution was used to prepare polymer solutions of 0.5 wt%, 0.8 wt%, and 1.0 wt% for each example and comparative example, respectively. These solutions were then analyzed using a HAKKE MARSII rheometer at 120°C for 100 seconds. -1 Under the given rotational speed, the viscosity of the solution after 2 hours of shearing was tested, and the results are shown in Table 2.

[0088] Table 2

[0089]

[0090]

[0091] As the concentration increases, the viscosity of the solution also increases. At 80℃, the solution Ca... 2+ The viscosity of the 5000 mg / L solution was greater than 25 mPa·s, and the higher the molecular weight, the greater the viscosity of the solution.

[0092] Test Example 2

[0093] The 0.5% by weight solution prepared in Test Example 1 was poured into 100mL test tubes containing 25g of crude oil a, b, and c (viscosities at 50℃: a, 1000mPa·s; b, 1500mPa·s; c, 2000mPa·s) at a 1:1 solution-to-crude oil mass ratio, without stirring or shaking. The tubes were then heated in an oven at 80℃ for 15 minutes, cooled to 50℃, and the static viscosity reduction rate was measured using a Brookfield DVIII rotational viscometer. The results are shown in Table 3. Static viscosity reduction rate = (initial viscosity - viscosity after viscosity reduction) / initial viscosity × 100%.

[0094] Table 3

[0095]

[0096]

[0097] The minimum usage concentration is 0.5% by weight of the polymer solution. After heating at 80°C, Ca... 2+ At a concentration of 5000 mg / L, the static viscosity reduction rate for crude oil with a viscosity between 1000-2000 mPa·s is >90%, indicating that the polymer of this invention is particularly suitable for reducing the viscosity of crude oil with a viscosity of 1000-2000 mPa·s and can still maintain high viscosity reduction performance under high temperature and high salinity conditions. The static viscosity reduction rates of the polymer solutions synthesized in comparative examples D1, D2, and D3 are all <80%. When the weight-average molecular weight deviates from the range of 600,000-1,200,000, the monomer polymerization rate becomes unevenly distributed, leading to a significant decrease in viscosity reduction performance. Comparing the above viscosity reduction effects, the polymer with a weight-average molecular weight of 700,000-1,000,000 exhibits the best viscosity reduction effect.

[0098] Test Example 3

[0099] Product 3, obtained from Example 3 (with the lowest viscosity reduction and highest viscosity), Product 1, obtained from Example 1 (with intermediate viscosity reduction and viscosity), and Product 6, obtained from Example 6 (with the highest viscosity reduction and lowest viscosity), were selected for testing. A 0.5% by weight concentration solution was prepared according to the method described in Test Example 1. A core sample of quartz sand, natural oil sand, and epoxy resin cemented together was used, with dimensions of φ2.5cm × 30cm and a gas permeability of 2200 × 10⁻⁶. -3 μm 2 The experimental temperature was 80℃, and the recovery rate of degassed and dehydrated crude oil with viscosities of 1000 mPa·s and 2000 mPa·s was tested respectively. The solution was adjusted to CaCl2 in deionized water. 2+A concentration of 5000 mg / L was used as the displacement water. The polymer solution was then injected at a rate of 0.3 mL / min until the water content reached 98 wt%. The recovery rate was calculated and compared with water flooding. The results showed that for heavy oil with a viscosity of 1000-2000 mPa·s, the core displacement recovery rate was >60%. Specific test results are shown in Table 4.

[0100] like Figure 1 As shown, under the conditions of calcium ion concentration of 5000 mg / L, temperature of 80℃, and system dosage of 0.5 wt%, for heavy oil with viscosity of 2000 mPa·s, after injecting 2.87 PV system solution, the water content reached 98.4 wt%, and the core displacement recovery rate of product 3 obtained in Example 3 was 60.5%.

[0101] Table 4

[0102] product Recovery rate at 1000 mPa·s, % Recovery rate at 2000 mPa·s, % 1 65.3 66.1 6 61.5 64.5 3 63.5 60.5

[0103] The results in Tables 1-4 show that the embodiments employing the technical solution of this invention have the beneficial effects of high static viscosity reduction, high recovery rate, and excellent salt and temperature resistance. Based on the recovery rate results of Example 3, it can be inferred that because the products obtained in other embodiments have lower viscosity and higher viscosity reduction rates, under the conditions of a calcium ion concentration of 5000 mg / L, a temperature of 80°C, and a system dosage of 0.5 wt%, the core displacement recovery rate for heavy oil with a viscosity of 2000 mPa·s is >60%.

[0104] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polymer with viscosity-reducing function, characterized in that, The polymer has structural units shown in Formula 1 and Formula 2: wherein R, R2 and R3 are each independently selected from H or C1-C6 alkyl; M is selected from H or an alkali metal element; and x is an integer selected from 4-18; the mass ratio of the structural unit shown in Formula 1 to the structural unit shown in Formula 2 is 1:0.1-5; the weight average molecular weight of the polymer is 60-120 million.

2. The polymer of claim 1, wherein, the molecular weight distribution index of the polymer is 1.2-2.2; and / or, R is selected from H, methyl, ethyl, propyl, butyl or pentyl; and / or, x is an integer selected from 4-16; and / or, R2 and R3 are each independently selected from H, methyl or ethyl; and / or, M is H or Na.

3. The polymer of claim 2, wherein, R is H, methyl or ethyl; and / or, x is an integer selected from 4-12; and / or, R2 and R3 are each independently selected from H or methyl; and / or, M is Na.

4. The polymer according to any one of claims 1 to 3, wherein, the weight ratio of the structural unit shown in Formula 1 to the structural unit shown in Formula 2 is 1:0.3-2.

5. The polymer of claim 4, wherein, the weight ratio of the structural unit shown in Formula 1 to the structural unit shown in Formula 2 is 1:0.5-1.

5.

6. The polymer of any one of claims 1-5, wherein, the weight average molecular weight of the polymer is 65-110 million; and / or, the molecular weight distribution index of the polymer is 1.2-2.

7. The polymer of claim 6, wherein, the weight average molecular weight of the polymer is 70-100 million; and / or, the molecular weight distribution index of the polymer is 1.2-1.

6.

8. A method for producing a polymer having a viscosity-reducing function, characterized by, The method comprises: mixing a compound shown in Formula I and a compound shown in Formula II in the presence of a solvent, an initiator and a catalyst to occur a polymerization reaction; wherein the weight ratio of the compound shown in Formula I to the compound shown in Formula II is 1:0.1-5; and R, R2, R3, x and M are defined as the same as the definitions in any one of claims 1-7.

9. The method of claim 8, wherein, The solvent is selected from water-miscible solvents, preferably at least one of water, tetrahydrofuran and dioxane.

10. The method of claim 8 or 9, wherein, The initiator is selected from at least one of azo compounds, persulfides and peroxides.

11. The method of claim 10, wherein, The initiator is an azo compound.

12. The method of claim 11, wherein, The initiator is selected from at least one of azobisdimethylamidinum hydrochloride, azobisdimethylazepine and azobisdimethylimidazoline hydrochloride.

13. The method of any of claims 8-12, wherein, The catalyst is selected from organic metal compounds and / or metal halides.

14. The method of claim 13, wherein, The catalyst is selected from at least one of acetylacetone zirconium, triethylaluminum, titanium tetrachloride and copper bromide.

15. The method of claim 8, wherein, The weight ratio of the compound shown in Formula I to the compound shown in Formula II is 1:0.3-2.

16. The method of claim 15, wherein, The weight ratio of the compound shown in Formula I to the compound shown in Formula II is 1:0.5-1.

5.

17. The method according to any one of claims 8-16, wherein the weight ratio of the initiator to the compound shown in Formula I is 1:30-250, preferably 1:100-200.

18. The method according to any one of claims 8-17, wherein the weight ratio of the catalyst to the compound shown in Formula I is 1:30-250, preferably 1: 100-200.

19. The method of any of claims 8-18, wherein, The temperature of the polymerization reaction is 50-90℃, preferably 60-80℃.

20. The method of claim 19, wherein, The time of the polymerization reaction is 12-48h, preferably 18-30h.

21. The polymer obtained by the method according to any one of claims 8-20.

22. The use of the polymer according to any one of claims 1-7 and 21 in an oil displacement agent.

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