Polymer and preparation method therefor and use thereof

Abstract

The present invention relates to the field of development and recovery of oilfields, and discloses a polymer and a preparation method therefor and use thereof. The polymer contains a structural unit A shown in formula (I), a structural unit B shown in formula (II) and a structural unit C shown in formula (III), wherein the molar ratio of the structural unit A : the structural unit B : the structural unit C is (30-480) : (10-85) : 1. The viscosity-average molecular weight of the polymer is 200-1200 g / mol. The polymer has low molecular weight, good water solubility and excellent salt resistance. Using an aqueous solution of the polymer to displace low permeability oil reservoirs can significantly improve the oil displacement effect and enhance the oil recovery efficiency.

Description

Polymer and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202311506132.7, filed on November 13, 2023, entitled “Polymers and Their Preparation Methods and Applications,” the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of oil field development and recovery, and in particular to a polymer and a preparation method and application thereof. Background Art

[0004] Most domestic oilfields are continental deposits characterized by severe heterogeneity and thick oil. Waterflooding has an average recovery rate of approximately 32%, and the industry has entered the late stages of waterflooding. Currently, polyacrylamide flooding is the primary method for tertiary oil recovery. Technicians have extensively researched and refined the supporting technologies for polyacrylamide flooding. Since the industrial rollout of polyacrylamide flooding at Daqing Oilfield in 1995, it has become a key pillar of stable production at the field. Meanwhile, other domestic oilfields, including Shengli Oilfield, Jilin Oilfield, and Xinjiang Oilfield, have also begun researching polymer flooding technologies.

[0005] To meet the requirements of efficient oilfield development, further research is needed into methods and technologies for improving oil recovery, as well as new oil displacement agent products that match these requirements. Chemical flooding, particularly polymer flooding, is a mature and viable development measure. For Class II and Class III reservoirs, which have low formation permeability and small pores, polymer flooding requires lower molecular weight polymers. However, conventional low- and medium-molecular-weight polymers have low viscosity in highly salinized water, making them prone to problems such as "fingering" and "surgery," resulting in low displacement efficiency.

[0006] Therefore, there is an urgent need to develop polymers with low molecular weight and higher viscosity in brine to improve the oil recovery efficiency of Class II and Class III reservoirs.

[0007] Summary of the Invention

[0008] The present invention aims to solve the problem that the oil displacement agent used in existing polymer flooding is difficult to achieve both low molecular weight and good salt resistance, which leads to low oil displacement efficiency in low permeability reservoirs. A polymer, a preparation method and application thereof are provided.

[0009] In order to achieve the above-mentioned object, the first aspect of the present invention provides a polymer, wherein the polymer comprises a structural unit A represented by formula (I), a structural unit B represented by formula (II), and a structural unit C represented by formula (III);

[0010] wherein R1, R2, R3, R4, R5 and R6 are each independently selected from -H or C1-C4 alkyl; R7 and R8 are each independently selected from C1-C2 alkyl; R9 is selected from C1-C2 alkylene; R 10 、R 11 and R 12 are each independently selected from -H or C1-C4 alkyl; R 13 、R 14 are each independently selected from -H or -CH3; R 15 Selected from -H, -CH3, -COOM 1 、-SO3M 2 or -X; Z is selected from H + , K + 、Na + or NH4 + ; n is an integer of 4-18; wherein, M 1 、M 2 Each independently selected from H + , K + 、Na + or NH4 + ; X is halogen;

[0011] The molar ratio of the structural unit A: structural unit B: structural unit C is (30-480): (10-85): 1;

[0012] The viscosity average molecular weight of the polymer is 200-1200 g / mol.

[0013] The second aspect of the present invention provides a method for preparing a polymer, comprising: polymerizing monomer A', monomer B' and monomer C' in the presence of an initiator, a cosolvent and a solvent to obtain a polymer;

[0014] Wherein, the monomer A' is a monomer having a structure represented by formula (IV), the monomer B' is a monomer having a structure represented by formula (V), and the monomer C' is a monomer having a structure represented by formula (VI).

[0015] wherein R1, R2, R3, R4, R5 and R6 are each independently selected from -H or C1-C4 alkyl; R7 and R8 are each independently selected from C1-C2 alkyl; R9 is selected from C1-C2 alkylene; R 10 、R 11 and R 12 are each independently selected from -H or C1-C4 alkyl; R 13 、R 14 are each independently selected from -H or -CH3; R 15 Selected from -H, -CH3, -COOM 1、-SO3M 2 or -X; Z is selected from H + , K + 、Na + or NH4 + ; n is an integer of 4-18; wherein, M 1 、M 2 Each independently selected from H + , K + 、Na + or NH4 + ; X is halogen;

[0016] The molar ratio of monomer A':monomer B':monomer C' is (30-480):(10-85):1.

[0017] The third aspect of the present invention provides a polymer obtained by the method described in the second aspect.

[0018] The fourth aspect of the present invention provides use of the polymer described in the first or third aspect as an oil displacement agent in the exploitation of low permeability oil reservoirs.

[0019] The polymer provided by the present invention contains structural units And structural units provided by large skeleton functional monomers containing long chain side groups This polymer has a low molecular weight and good water solubility. It can maintain a large hydrodynamic size in highly saline water environments and exhibits excellent salt resistance. When formulated into a polymer brine solution with a polymer concentration of 1000 mg / L and a salinity of 1100-6000 mg / L, the polymer brine solution has an apparent viscosity of 20-80 mPa·s at 45°C. Using this polymer solution in low-permeability oil reservoirs can significantly improve oil displacement and increase oil recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is an infrared test spectrum of the polymer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0022] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0023] In a first aspect, the present invention provides a polymer comprising a structural unit A represented by formula (I), a structural unit B represented by formula (II), and a structural unit C represented by formula (III);

[0024] wherein R1, R2, R3, R4, R5 and R6 are each independently selected from -H or C1-C4 alkyl; R7 and R8 are each independently selected from C1-C2 alkyl; R9 is selected from C1-C2 alkylene; R 10 、R 11 and R 12 are each independently selected from -H or C1-C4 alkyl; R 13 、R 14 are each independently selected from -H or -CH3; R 15 Selected from -H, -CH3, -COOM 1 、-SO3M 2 or -X; Z is selected from H + , K + 、Na + or NH4 + ; n is an integer of 4-18; wherein, M 1 、M 2 Each independently selected from H + , K + 、Na + or NH4 + ; X is halogen;

[0025] The molar ratio of the structural unit A: structural unit B: structural unit C is (30-480): (10-85): 1;

[0026] The viscosity average molecular weight of the polymer is 200-1200 g / mol.

[0027] According to the present invention, in the polymer, the structural unit A can function as a polymer backbone. Preferably, in the structural unit A represented by formula (I), R1, R2 and R3 are each independently selected from -H or a C1-C2 alkyl group.

[0028] According to the present invention, in the polymer, the structural unit B can enhance the water solubility of the polymer and resist hydrolysis of the amide groups in the polymer by salt ions in the solution. Preferably, in the structural unit B represented by formula (II), R4, R5, and R6 are each independently selected from -H or a C1-C2 alkyl group; R7 and R8 are -CH3; and R9 is -CH2-. This preferred structural unit B can enhance the water solubility and hydrolysis resistance of the polymer.

[0029] According to the present invention, in the polymer, the structural unit C contains a long-chain large side group. Specifically, in formula (III), n is an integer of 3-18. The long-chain large side group can enhance the rigidity of the polymer molecular chain and increase the mean square rotation radius of the polymer molecular chain. The long-chain large side group can stretch and entangle in water, thereby increasing the viscosity of the polymer. By introducing the structural unit C with a larger skeleton into the molecular chain of the polymer, the rigidity of the polymer molecular chain can be enhanced, the hydration ability of the polymer can be improved, and the polymer molecules can maintain a larger hydrodynamic size in a high-mineralization water environment, which can enhance the salt resistance of the polymer to a certain extent. Furthermore, the structural unit C can inhibit the hydrolysis of the polymer under high-mineralization water conditions, thereby further improving the salt resistance of the polymer, and is not easy to react with calcium ions, magnesium ions, etc. to form precipitation. Preferably, in the structural unit C shown in formula (III), R 10 、R 11 and R 12 are each independently selected from -H or C1-C2 alkyl; R 13 、R 14 -H; R 15 Selected from -SO3M 2 Or -X. The preferred structural unit C can make the polymer have higher viscosity and better salt resistance.

[0030] According to the present invention, in the structural unit C represented by formula (III), the halogen X is preferably F, Cl or Br.

[0031] According to the present invention, in the structural unit C represented by formula (III), preferably, n is an integer of 8-16, which helps the polymer to better balance salt resistance and water solubility.

[0032] According to the present invention, on the basis of satisfying the above structure and composition, preferably, in the polymer, the molar ratio of the structural unit A: structural unit B: structural unit C is (100-280): (28-70): 1, which can make the polymer have better salt resistance and better water solubility.

[0033] According to the present invention, preferably, the viscosity average molecular weight of the polymer is 300-900 g / mol.

[0034] According to the present invention, the polymer satisfies the aforementioned structure and composition, thereby exhibiting excellent salt tolerance, as demonstrated by the polymer being soluble in a highly saline solution, resulting in the saline solution having a high apparent viscosity. Preferably, the polymer is formulated into a polymer saline solution having a polymer concentration of 1000 mg / L and a salinity of 1100-6000 mg / L, and the apparent viscosity of the polymer saline solution at 45°C is 20-80 mPa·s.

[0035] In the present invention, the apparent viscosity of the polymer salt solution is measured using a Brookfield DV-II viscometer from the United States, using a No. 0 (ie, 0#) rotor, at a rotation speed of 6 rpm and a temperature of 45°C.

[0036] In the present invention, the mineralization can be expressed by the amount of NaCl (mg / L) contained in 1 L of water.

[0037] The polymer provided by the present invention has a low molecular weight, and the molecular chain of the polymer is highly rigid and has a large rotation radius of the molecular chain. During its movement in the oil layer, the polymer can effectively drive the crude oil attached to the pore wall of the formation. At the same time, the polymer has excellent salt resistance and can still maintain its original structure and high viscosity in high-mineralization formations. The molecular chains of ordinary low-molecular-weight polymers are soft and easily entangled, resulting in a small rotation radius, making it difficult to drive the crude oil attached to the pore wall in the oil layer, and it is easy to precipitate and fail in high-mineralization formations. Therefore, the polymer provided by the present invention is used as an oil-displacing agent for oil reservoir development. Compared with the ordinary low-molecular-weight polymers used in existing polymer flooding, it has a better oil-displacing effect and can significantly improve the recovery rate of oil reservoirs (especially low-permeability oil reservoirs).

[0038] According to a most preferred embodiment of the present invention, the polymer contains structural unit A ( Structural unit B and structural unit C( and / or ), the weight ratio of structural unit A: structural unit B: structural unit C is (130-140): (45-48): 1, the number average molecular weight of the polymer is 600-750 g / mol, and it has better salt resistance and oil displacement performance.

[0039] The second aspect of the present invention provides a method for preparing a polymer, comprising: polymerizing monomer A', monomer B' and monomer C' in the presence of an initiator, a cosolvent and a solvent to obtain a polymer;

[0040] Wherein, the monomer A' is a monomer having a structure represented by formula (IV), the monomer B' is a monomer having a structure represented by formula (V), and the monomer C' is a monomer having a structure represented by formula (VI).

[0041] wherein R1, R2, R3, R4, R5 and R6 are each independently selected from -H or C1-C4 alkyl; R7 and R8 are each independently selected from C1-C2 alkyl; R9 is selected from C1-C2 alkylene; R 10 、R 11 and R 12 are each independently selected from -H or C1-C4 alkyl; R 13 、R 14 are each independently selected from -H or -CH3; R 15 Selected from -H, -CH3, -COOM 1 、-SO3M 2 or -X; Z is selected from H + , K + 、Na + or NH4 + ; n is an integer of 4-18; wherein, M 1 、M 2 Each independently selected from H + , K + 、Na + or NH4 + ; X is halogen;

[0042] The molar ratio of monomer A':monomer B':monomer C' is (30-480):(10-85):1.

[0043] According to the present invention, in the preparation method of the polymer, the monomer A' has excellent polymerizability and can serve as a polymer backbone. Preferably, in the monomer A' represented by formula (IV), R1, R2 and R3 are each independently selected from -H or a C1-C2 alkyl group.

[0044] According to the present invention, in the method for preparing the polymer, the monomer B' can make the resulting polymer more soluble in water and resist the hydrolysis of the amide groups in the resulting polymer by salt ions in the solution. Preferably, in the monomer B' represented by formula (V), R4, R5, and R6 are each independently selected from -H or a C1-C2 alkyl group; R7 and R8 are -CH3; and R9 is -CH2-.

[0045] According to the present invention, in the preparation method of the polymer, the monomer C' has a larger skeleton structure and contains long-chain large side groups, which can make the prepared polymer have stronger molecular chain rigidity, larger mean square rotation radius and higher viscosity. By introducing the structural unit provided by the monomer C' into the molecular chain of the polymer, the rigidity of the polymer molecular chain can be enhanced, the hydration ability can be improved, so that the polymer molecules can maintain a larger hydrodynamic size in a high-mineralization water environment, thereby enhancing the salt resistance of the polymer. Furthermore, the structural unit provided by the monomer C' can inhibit the hydrolysis of the polymer under high-mineralization water conditions, thereby further improving the salt resistance of the polymer. Preferably, in the monomer C' shown in formula (VI), R 10 、R 11 and R 12 are each independently selected from -H or C1-C2 alkyl; R 13 、R 14 -H; R 15 Selected from -SO3M 2 Or -X. The preferred monomer C' can make the obtained polymer have higher viscosity and better salt resistance.

[0046] According to the present invention, in the method for preparing the polymer, in the monomer C' represented by formula (VI), the halogen X is preferably F, Cl or Br.

[0047] According to the present invention, in the method for preparing the polymer, in the monomer C' represented by formula (VI), preferably, n is an integer of 8-16, so that the prepared polymer can better balance salt resistance and water solubility.

[0048] According to the present invention, in the preparation method of the polymer, the monomer A', monomer B' and monomer C', on the basis of satisfying the above-mentioned proportional relationship, preferably, the molar ratio of the structural unit A: structural unit B: structural unit C is (100-280): (28-70): 1, which can enable the prepared polymer to have better salt resistance and better water solubility.

[0049] According to the present invention, in the method for preparing the polymer, preferably, in the reaction system containing the initiator, cosolvent, solvent, monomer A', monomer B' and monomer C', the total monomer concentration of monomer A', monomer B' and monomer C' is 0.1-50wt%, which is conducive to the control of the polymerization reaction process.

[0050] According to the present invention, in the method for preparing the polymer, preferably, the weight ratio of the cosolvent:monomer C' is 1:(1-10), which can make the monomer C' better dissolved and participate in polymerization.

[0051] According to the present invention, the cosolvent can be selected from at least one of alkyl sulfates, alkyl sulfonates, alkylbenzene sulfonates, alkyltrimethylammonium halides, alkylbenzenetrimethylammonium halides, fatty alcohol polyoxyethylene ethers and alkylphenol polyoxyethylene ethers.

[0052] According to the present invention, in the method for preparing the polymer, preferably, the weight ratio of the initiator to the monomer C' is 1:(10-1000).

[0053] According to the present invention, in the method for preparing the polymer, the initiator has a relatively wide range of restrictions, and conventional initiators for free radical polymerization reactions, such as azo initiators, peroxide initiators, or redox system initiators, can be used.

[0054] According to the present invention, preferably, the azo initiator can be selected from at least one of azobisisobutyric acid dimethyl ester (AIBME), azobisisobutyramidine hydrochloride (AIBA), azodicarbonamide (ADC), azobisisopropylimidazoline hydrochloride (AIB1), azoisobutylcyanamide (CABN), azobiscyclohexylcarbonitrile (ACCN), azobiscyanovaleric acid (ACVA), azobisisopropylimidazoline (AIP), azobisisobutyronitrile (AIBN), azobisisovaleronitrile (AMBN) and azobisisoheptanenitrile (ABVN).

[0055] According to the present invention, preferably, the peroxide initiator can be selected from at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, benzoyl peroxide and tert-butyl benzoyl peroxide.

[0056] According to the present invention, preferably, the redox system initiator can be selected from at least one of sulfate-sulfite, persulfate-thiourea, persulfate-organic salt, ammonium persulfate-fatty amine and persulfate-thiosulfate.

[0057] According to the present invention, in the method for preparing the polymer, the polymerization reaction preferably adopts aqueous solution polymerization or emulsion polymerization. When aqueous solution polymerization is adopted, the solvent is water; when emulsion polymerization is adopted, the solvent is a mixture of water and organic matter.

[0058] According to the present invention, in the preparation method of the polymer, when an emulsion polymerization method is used, the organic matter can be at least one selected from hexane, petroleum ether, acetone, ethyl acetate, benzene, toluene, xylene, dichloromethane, chloroform, and kerosene. Preferably, the weight ratio of water to organic matter is 1:(1-20).

[0059] According to the present invention, in the method for preparing the polymer, the polymerization reaction conditions include: pH value of 4-11, temperature of 0-90° C., and time of 2-24 hours.

[0060] According to the present invention, in the method for preparing the polymer, the polymerization reaction is carried out under a protective atmosphere, such as helium, neon, argon or nitrogen.

[0061] According to some preferred embodiments of the present invention, the process of preparing the polymer by aqueous solution polymerization comprises:

[0062] (1) mixing the monomer A', monomer B', monomer C', a cosolvent and water according to the above species and proportions to obtain a reaction system;

[0063] In the reaction system, the total monomer concentration of the monomer A', monomer B' and monomer C' is 0.1-50 wt%;

[0064] (2-1) adding an initiator to the reaction system and conducting a first polymerization reaction under a protective atmosphere to obtain a first product system;

[0065] The conditions of the first polymerization reaction include: pH value of 4-11, temperature of 0-30°C, and time of 1-8h;

[0066] (2-2) subjecting the first product system to a second polymerization reaction, and granulating, drying, and pulverizing the resulting product colloid to obtain the polymer;

[0067] The conditions of the second polymerization reaction include: pH value of 4-11, temperature of 50-90° C., and time of 1-6 hours.

[0068] According to some preferred embodiments of the present invention, the process of preparing the polymer by emulsion polymerization includes:

[0069] (1) Mixing the monomer A', monomer B', monomer C', a cosolvent, an organic solvent and water according to the above species and proportions to obtain an emulsion system;

[0070] In the emulsion system, the total monomer concentration of the monomer A', monomer B' and monomer C' is 1-30 wt%;

[0071] (2-1) adding an initiator to the emulsion system, and conducting a first polymerization reaction under a protective atmosphere to obtain a first product system;

[0072] The conditions of the first polymerization reaction include: pH 4-11, temperature 0-30°C, and time 1-16h;

[0073] (2-2) subjecting the first product system to a second polymerization reaction, and granulating, drying, and pulverizing the resulting product colloid to obtain the polymer;

[0074] The conditions of the second polymerization reaction include: pH value of 4-11, temperature of 40-70° C., and time of 1-8 hours.

[0075] The polymer prepared by the method of the present invention has a low molecular weight, a viscosity-average molecular weight of 200-1200 g / mol, and excellent salt resistance. The polymer is prepared into a polymer brine solution with a polymer concentration of 1000 mg / L and a salinity of 1100-6000 mg / L. The polymer brine solution has an apparent viscosity of 20-80 mPa·s at 45°C. As an oil displacement agent, the polymer can significantly improve the oil displacement effect and increase the recovery rate.

[0076] The third aspect of the present invention provides a polymer obtained by the method described in the second aspect.

[0077] According to the present invention, the structure, composition and properties of the polymer prepared by the method described in the second aspect are the same as those of the polymer described in the first aspect of the present invention, and will not be described in detail here.

[0078] The fourth aspect of the present invention provides use of the polymer described in the first or third aspect as an oil displacement agent in the exploitation of low permeability oil reservoirs.

[0079] According to the present invention, the polymer has a low molecular weight, strong molecular chain rigidity, a large molecular chain rotation radius, and excellent salt resistance. It can still maintain a high viscosity in a high salinity environment. As an oil displacement agent, it can significantly improve the recovery rate of oil reservoirs (especially low permeability oil reservoirs).

[0080] The present invention will be described in detail below through examples. In the following preparation examples, examples and comparative examples, unless otherwise specified, all methods are conventional methods; and the reagents and materials described, unless otherwise specified, can be obtained from commercial sources.

[0081] In the following examples and comparative examples, the weight ratio of the structural units contained in the prepared polymers was calculated based on the feed amounts of the raw materials.

[0082] Example 1

[0083] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), and after being fully dissolved, a reaction system is obtained;

[0084] The molar ratio of monomer A':monomer B':monomer C' is 138.6:46.2:1; the weight ratio of cosolvent:monomer C' is 1:10; and the total monomer concentration of monomer A', monomer B', and monomer C' in the reaction system is 25 wt%;

[0085] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:125). A first polymerization reaction was carried out at 20°C for 2 h under a nitrogen atmosphere, and then the temperature was raised to 80°C for a second polymerization reaction for 4 h. The resulting product colloid was granulated, dried, and crushed to obtain a white polymer powder (denoted as P1);

[0086] The infrared spectrum of P1 is tested, and the results are shown in Figure 1. In Figure 1, 3420cm -1 and 3209cm -1 It is the characteristic peak of -NH2, 2935m -1 -CH3 characteristic peak, 2860m -1 -CH2- characteristic peak, 1668m -1 It is the characteristic peak of C=O, 1453m -1 It is the characteristic peak of CN, 1265m -1 、1038m -1 and 605m -1 It is the characteristic peak of -SO3H, 1570m -1 It is a characteristic peak of -NH-, indicating that monomer A', monomer B', and monomer C' are successfully polymerized to obtain a polymer.

[0087] In P1, structural unit A Structural unit B Structural unit C The molar ratio of P1 is 138.6:46.2:1. The viscosity average molecular weight of P1 is 652 g / mol.

[0088] Example 2

[0089] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), and after being fully dissolved, a reaction system is obtained;

[0090] The molar ratio of monomer A':monomer B':monomer C' is 135:45:1; the weight ratio of cosolvent:monomer C' is 1:3; and the total monomer concentration of monomer A', monomer B', and monomer C' in the reaction system is 25 wt%;

[0091] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:125). A first polymerization reaction was carried out at 20°C for 2 h under a nitrogen atmosphere. The temperature was then raised to 80°C for a second polymerization reaction for 4 h. The resulting product colloid was granulated, dried, and pulverized to obtain a white polymer powder (denoted as P2);

[0092] In P2, structural unit A Structural unit B Structural unit C The molar ratio of P2 is 135:45:1. The viscosity average molecular weight of P2 is 721 g / mol.

[0093] Example 3

[0094] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), and after being fully dissolved, a reaction system is obtained;

[0095] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:7; and the total monomer concentration of monomer A', monomer B', and monomer C' in the reaction system is 28 wt%;

[0096] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:100). Under a nitrogen atmosphere, a first polymerization reaction was carried out at 25°C for 2.5 hours, and then the temperature was raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and crushed to obtain a white polymer powder (denoted as P3);

[0097] In P3, structural unit A Structural unit B Structural unit C The molar ratio of P3 is 60:20:1. The viscosity average molecular weight of P3 is 227 g / mol.

[0098] Example 4

[0099] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), and after being fully dissolved, a reaction system is obtained;

[0100] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:2; and the total monomer concentration of monomer A', monomer B' and monomer C' in the reaction system is 28 wt%;

[0101] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:100). A first polymerization reaction was carried out at 25°C for 2.5 hours under a nitrogen atmosphere. The temperature was then raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and pulverized to obtain a white polymer powder (denoted as P4);

[0102] In P4, structural unit A Structural unit B Structural unit C The molar ratio of P4 is 60:20:1. The viscosity average molecular weight of P4 is 325 g / mol.

[0103] Example 5

[0104] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), and after being fully dissolved, a reaction system is obtained;

[0105] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:2; and the total monomer concentration of monomer A', monomer B' and monomer C' in the reaction system is 28 wt%;

[0106] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:100). Under a nitrogen atmosphere, a first polymerization reaction was carried out at 25°C for 2.5 hours, and then the temperature was raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and crushed to obtain a white polymer powder (denoted as P5);

[0107] In P5, structural unit A Structural unit B Structural unit C The molar ratio of P5 is 60:20:1. The viscosity average molecular weight of P5 is 247 g / mol.

[0108] Example 6

[0109] (1) Monomer A' Monomer B' and water (water: petroleum ether weight ratio is 1:3) to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), and after being fully dissolved, mixed with petroleum ether, Span-20 and Span-60 (the weight ratio of Span-20:Span-60 is 4:1, accounting for 1% of the total weight of the reaction system) are added, and then fully stirred to obtain an emulsion system;

[0110] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:2; and the total monomer concentration of monomer A', monomer B' and monomer C' in the emulsion system is 25 wt%;

[0111] (2) An initiator (azobisisovaleronitrile, i.e., AMBN) was added to the above emulsion system (the weight ratio of initiator to monomer C' was 1:30). A first polymerization reaction was carried out at 30°C for 12 h under a nitrogen atmosphere. The temperature was then raised to 70°C for a second polymerization reaction for 4 h. The resulting product colloid was filtered, dried, and pulverized to obtain a white polymer powder (denoted as P6);

[0112] In P6, structural unit A Structural unit B Structural unit C The molar ratio of P6 is 60:20:1. The viscosity average molecular weight of P6 is 215 g / mol.

[0113] Example 7

[0114] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), and after being fully dissolved, a reaction system is obtained;

[0115] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:5; and the total monomer concentration of monomer A', monomer B', and monomer C' in the reaction system is 28 wt%;

[0116] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:100). Under a nitrogen atmosphere, a first polymerization reaction was carried out at 25°C for 2.5 hours, and then the temperature was raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and crushed to obtain a white polymer powder (denoted as P7);

[0117] In P7, structural unit A Structural unit B Structural unit C The molar ratio of P7 is 60:20:1. The viscosity average molecular weight of P7 is 327 g / mol.

[0118] Example 8

[0119] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium hexadecylbenzenesulfonate), and after fully dissolving, a reaction system is obtained;

[0120] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:1; and the total monomer concentration of monomer A', monomer B', and monomer C' in the reaction system is 28 wt%;

[0121] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:100). Under a nitrogen atmosphere, a first polymerization reaction was carried out at 25°C for 2.5 hours, and then the temperature was raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and crushed to obtain a white polymer powder (denoted as P8);

[0122] In P8, structural unit A Structural unit B Structural unit C The molar ratio of P8 is 60:20:1. The viscosity average molecular weight of P8 is 452 g / mol.

[0123] Comparative Example 1

[0124] (1) Monomer A' Monomer B' and water to prepare a solution, and adjust the pH value of the solution to 7.0 to obtain a reaction system;

[0125] The molar ratio of monomer A':monomer B' is 60:20; in the reaction system, the total monomer concentration of monomer A' and monomer B' is 28 wt%;

[0126] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer A' was 1:6000). A first polymerization reaction was carried out at 25°C for 2.5 hours under a nitrogen atmosphere. The temperature was then raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and pulverized to obtain a white polymer powder (denoted as D1).

[0127] In D1, structural unit A Structural unit B The molar ratio of D1 is 60:20. The viscosity average molecular weight of D1 is 1015 g / mol.

[0128] Comparative Example 2

[0129] (1) Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (dodecylbenzenesulfonic acid), and after being fully dissolved, a reaction system is obtained;

[0130] The molar ratio of monomer B':monomer C' is 20:1; the weight ratio of cosolvent:monomer C' is 1:2; and the total monomer concentration of monomer B' and monomer C' in the reaction system is 28 wt%;

[0131] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:100). A first polymerization reaction was carried out at 25°C for 2.5 hours under a nitrogen atmosphere. The temperature was then raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and pulverized to obtain a white polymer powder (denoted as D2);

[0132] In D2, structural unit B Structural unit C The molar ratio of D2 is 20: 1. The viscosity average molecular weight of D2 is 34 g / mol.

[0133] Comparative Example 3

[0134] (1) Monomer A' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (dodecylbenzenesulfonic acid), and after being fully dissolved, a reaction system is obtained;

[0135] The molar ratio of monomer A':monomer C' is 60:1; the weight ratio of cosolvent:monomer C' is 1:2; and the total monomer concentration of monomer A' and monomer C' in the reaction system is 28 wt%;

[0136] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:100). Under a nitrogen atmosphere, a first polymerization reaction was carried out at 25°C for 2.5 hours, and then the temperature was raised to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid was granulated, dried, and crushed to obtain a white polymer powder (denoted as D3);

[0137] In D3, structural unit A Structural unit C The molar ratio of D3 is 60: 1. The viscosity average molecular weight of D3 is 1137 g / mol.

[0138] Comparative Example 4

[0139] (1) Monomer A' Monomer B' Prepare a solution with water, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (dodecylbenzenesulfonic acid), and after being fully dissolved, a reaction system is obtained;

[0140] The molar ratio of monomer A':monomer B':monomer C' is 600:200:1; the weight ratio of cosolvent:monomer C' is 1:2; and the total monomer concentration of monomer A', monomer B' and monomer C' in the reaction system is 28 wt%;

[0141] (2) An initiator (potassium persulfate-sodium thiosulfate) was added to the above reaction system (the weight ratio of initiator to monomer C' was 1:50). A first polymerization reaction was carried out at 25°C under a nitrogen atmosphere for 2.5 hours. The temperature was then raised to 80°C for a second polymerization reaction for 4 hours. The resulting colloid was granulated, dried, and pulverized to obtain a white polymer powder (denoted as D4);

[0142] In D4, structural unit A Structural unit B Structural unit C The molar ratio of D4 is 600:200:1. The viscosity average molecular weight of D4 is 959 g / mol.

[0143] Test Case

[0144] The polymers P1-P8 and D1-D4 prepared in Examples 1-8 and Comparative Examples 1-4 were respectively subjected to salt resistance test and oil displacement performance test.

[0145] 1. Salt resistance test

[0146] Polymers P1-P8, D1-D4, and commercially available oil-displacing agent A (low molecular weight polyacrylamide, manufactured by Daqing Refining and Chemical Company, molecular weight 709 g / mol) were each mixed with saline water (2410 mg of NaCl dissolved in 1 L of water) to create polymer-salt solutions (denoted L1-L8 and DL1-DL5, respectively) with a polymer concentration of 1000 mg / L. The apparent viscosities of these polymer-salt solutions were measured using a Brookfield DV-II viscometer with a #0 rotor at 6 rpm and 45°C. The results are shown in Table 1.

[0147] Table 1 Note: D3 is not soluble in saline of this concentration, so the apparent viscosity of D3 saline solution cannot be tested.

[0148] As can be seen from Table 1, the polymers P1-P8 provided by the present invention have relatively low molecular weights and exhibit excellent salt tolerance. Under the same conditions, the polymer brine solutions of polymers D1-D4 prepared in Comparative Examples 1-4 and commercially available oil-displacing agent A have low apparent viscosities and significantly inferior salt tolerance to P1-P8.

[0149] 2. Oil displacement performance test

[0150] Polymers P1-P8, D1, D2, and D4, along with the commercially available oil-displacing agent A, were mixed with water to create aqueous polymer solutions with an apparent viscosity of 18 mPa·s (denoted as Q1-Q8 and DQ1-DQ4, respectively). Oil recovery capabilities were evaluated using these solutions in artificial rectangular cores (with a permeability of 100 mD). The injection rate of the polymer solutions was 0.3 mL / min, and the volume of the injected polymer solution was 0.9 PV. The results are shown in Table 2.

[0151] Table 2

[0152] As can be seen from Table 2, in the above-mentioned oil displacement experiments, the polymers P1-P8 provided by the present invention exhibited excellent oil displacement effects, with recovery rates exceeding 9.5% under the experimental conditions. Compared with ordinary low-molecular-weight polymers, the low-molecular-weight salt-resistant polymers provided by the present invention have higher aqueous solution viscosity at the same concentration, and their molecular chains are more rigid and elastic, making it easier to remove residual oil from the reservoir pores.

[0153] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A polymer, characterized in that The polymer contains a structural unit A represented by formula (I), a structural unit B represented by formula (II) and a structural unit C represented by formula (III); Wherein, R1, R2, R3, R4, R5 and R6 are each independently selected from -H or C1-C4 alkyl; R7 and R8 are each independently selected from C1-C2 alkyl; R9 is selected from C1-C2 alkylene; R 10 , R 11 and R 12 Each is independently selected from -H or C1-C4 alkyl; R 13 , R 14 are each independently selected from -H or -CH3; R 15 Selected from -H, -CH3, -COOM 1 、-SO3M 2 or -X; Z is selected from H + , K + 、Na + or NH4 + ; n is an integer of 4-18; wherein, M 1 、M 2 Each independently selected from H + , K + 、Na + or NH4 + ; X is halogen; The molar ratio of the structural unit A: structural unit B: structural unit C is (30-480): (10-85): 1; The viscosity average molecular weight of the polymer is 200-1200 g / mol.

2. The polymer according to claim 1, wherein R1, R2, R3, R4, R5 and R6 are each independently selected from -H or C1-C2 alkyl; R7 and R8 are -CH3; R9 is -CH2-; R 10 , R 11 and R 12 R is independently selected from -H or C1-C2 alkyl; 13 , R 14 -H; R 15 Selected from -SO3M 2 or -X; And / or, n is an integer from 8 to 16.

3. The polymer according to claim 1 or 2, wherein The molar ratio of the structural unit A: structural unit B: structural unit C is (100-280): (28-70):

1.

4. The polymer according to claim 1 or 2, wherein The viscosity average molecular weight of the polymer is 300-900 g / mol.

5. The polymer according to claim 1 or 2, wherein The polymer is formulated into a polymer saline solution with a polymer concentration of 1000 mg / L and a mineralization of 1100-6000 mg / L. The apparent viscosity of the polymer saline solution at 45° C. is 20-80 mPa·s.

6. A method for preparing a polymer, comprising: In the presence of an initiator, a cosolvent and a solvent, monomer A', monomer B' and monomer C' are polymerized to obtain a polymer; Wherein, the monomer A' is a monomer having a structure shown in formula (IV), the monomer B' is a monomer having a structure shown in formula (V), and the monomer C' is a monomer having a structure shown in formula (VI). Wherein, R1, R2, R3, R4, R5 and R6 are each independently selected from -H or C1-C4 alkyl; R7 and R8 are each independently selected from C1-C2 alkyl; R9 is selected from C1-C2 alkylene; R 10 , R 11 and R 12 Each is independently selected from -H or C1-C4 alkyl; R 13 , R 14 are each independently selected from -H or -CH3; R 15 Selected from -H, -CH3, -COOM 1 、-SO3M 2 or -X; Z is selected from H + , K + 、Na + or NH4 + ; n is an integer of 4-18; wherein, M 1 、M 2 Each independently selected from H + , K + 、Na + or NH4 + ; X is halogen; The molar ratio of the monomer A':monomer B':monomer C' is (30-480):(10-85):

1.

7. The method according to claim 6, wherein: In a reaction system containing the initiator, cosolvent, solvent, monomer A', monomer B' and monomer C', the total monomer concentration of the monomer A', monomer B' and monomer C' is 0.1-50wt%; and / or, the weight ratio of the cosolvent:monomer C' is 1:(1-10); And / or, the weight ratio of the initiator:monomer C' is 1:(10-1000).

8. The method according to claim 6 or 7, wherein: The solvent is water or a mixture of water and organic matter; And / or, the cosolvent is selected from at least one of alkyl sulfates, alkyl sulfonates, alkylbenzene sulfonates, alkyl trimethyl ammonium halides, alkyl benzene trimethyl ammonium halides, fatty alcohol polyoxyethylene ethers and alkylphenol polyoxyethylene ethers; And / or, the polymerization reaction conditions include: pH value of 4-11, temperature of 0-90° C., and time of 2-24 h.

9. A polymer obtained by the method according to any one of claims 6 to 8.

10. Use of the polymer according to any one of claims 1 to 5 and 9 as an oil displacement agent in the exploitation of low permeability oil reservoirs.

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