Polymer as well as preparation method and application thereof

Abstract

The invention relates to the field of oilfield development and recovery, and discloses a polymer as well as a preparation method and application thereof. The polymer contains a structural unit A as shown in a formula (I), a structural unit B as shown in a formula (II) and a structural unit C as shown in a formula (III), the molar ratio of the structural unit A to the structural unit B to the structural unit C is (30-480): (10-85): 1; the viscosity average molecular weight of the polymer is 200 to 1200 g / mol. The polymer has low molecular weight, good water solubility and excellent salt resistance, and by adopting an aqueous solution of the polymer to displace a low-permeability reservoir, the oil displacement effect can be remarkably improved, and the recovery efficiency can be improved. # imgabs0 #

Description

Technical Field

[0001] The 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

[0002] Most of the domestic oil fields are continental deposits, with serious heterogeneity and thick oil. The average water recovery rate is about 32%, and it has entered the late stage of water injection. At present, polyacrylamide flooding is the main means of tertiary oil recovery. The technical personnel have done a lot of work around polyacrylamide flooding. The supporting technology of polyacrylamide flooding is becoming more and more perfect. Since Daqing Oilfield began to promote polyacrylamide flooding industrially in 1995, polyacrylamide flooding technology has become an important technical pillar for the stable production of Daqing Oilfield. At the same time, other domestic oilfields such as Shengli Oilfield, Jilin Oilfield, Xinjiang Oilfield, etc. have also successively carried out research on polymer flooding technology.

[0003] In order to meet the requirements of efficient development of oil fields, it is necessary to further study the methods and technologies for improving oil recovery, as well as new oil displacement agent products that match them. Chemical flooding, especially polymer flooding, has mature application technology and is a feasible development measure. For Class II and Class III reservoirs, the formation permeability is low and the pores are small. For polymer flooding, lower molecular weight polymers are required. However, ordinary medium and low molecular weight polymers have low viscosity in high-salinity water, and are prone to problems such as "fingering" and "surge", resulting in low displacement efficiency.

[0004] 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. Summary of the invention

[0005] Aiming at the problem that the oil displacement agent used in the existing polymer flooding is difficult to have both low molecular weight and good salt resistance, which leads to low oil displacement efficiency in low permeability reservoirs, the present invention provides a polymer and a preparation method and application thereof.

[0006] 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);

[0007]

[0008] 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 , R14 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;

[0009] The molar ratio of the structural unit A: structural unit B: structural unit C is (30-480): (10-85): 1;

[0010] The viscosity average molecular weight of the polymer is 200-1200 g / mol.

[0011] The second aspect of the present invention provides a method for preparing a polymer, comprising: in the presence of an initiator, a cosolvent and a solvent, polymerizing a monomer A', a monomer B' and a monomer C' to obtain a polymer;

[0012] 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).

[0013]

[0014] 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 2Each independently selected from H + , K + 、Na + or NH4 + ; X is halogen;

[0015] The molar ratio of the monomer A':monomer B':monomer C' is (30-480):(10-85):1.

[0016] The third aspect of the present invention provides a polymer obtained by the method described in the second aspect.

[0017] The fourth aspect of the present invention provides use of the polymer described in the first aspect or the third aspect as an oil displacement agent in the exploitation of low permeability oil reservoirs.

[0018] The polymer provided by the present invention contains structural units And structural units provided by large skeleton functional monomers containing long chain side groups The polymer has a low molecular weight, good water solubility, can maintain a large hydrodynamic size in a water environment with high salinity, and has excellent salt resistance. The polymer is formulated into a polymer brine solution with a polymer concentration of 1000 mg / L and a salinity of 1100-6000 mg / L, and the apparent viscosity of the polymer brine solution at 45°C is 20-80 mPa·s. The use of the polymer aqueous solution to displace low permeability reservoirs can significantly improve the oil displacement effect and increase the recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the infrared test spectrum of the polymer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0021] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0022] In a first aspect, the present invention provides a polymer, the 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);

[0023]

[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 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;

[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 play the role of 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 the hydrolysis of the amide groups in the polymer by salt ions in the solution. Preferably, in the structural unit B shown in formula (II), R4, R5 and R6 are each independently selected from -H or C1-C2 alkyl; R7 and R8 are -CH3; and R9 is -CH2-. This preferred structural unit B can make the polymer have better water solubility and hydrolysis resistance.

[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 4-18. 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 it 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 R is independently selected from -H or C1-C2 alkyl; 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 is beneficial for 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 above structure and composition, and thus has excellent salt resistance, which can be manifested in that the polymer is soluble in a saline solution with a high mineralization degree, and the saline solution can have a higher apparent viscosity. Preferably, the polymer is formulated into a polymer saline solution with a polymer concentration of 1000 mg / L and a mineralization degree 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 degree can be expressed by the amount of NaCl (mg / L) contained in 1L of water.

[0037] The polymer provided by the present invention has a relatively low molecular weight, and at the same time, the polymer molecular chain has strong rigidity and a large molecular chain rotation radius, and can effectively drive the crude oil attached to the pore wall of the formation during movement in the oil layer. At the same time, the polymer has excellent salt resistance, and can still maintain the 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, and has a better oil-displacing effect than ordinary low-molecular-weight polymers used in existing polymer flooding, 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 recovery performance.

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

[0040] 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).

[0041]

[0042] 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;

[0043] The molar ratio of the monomer A':monomer B':monomer C' is (30-480):(10-85):1.

[0044] According to the present invention, in the preparation method of the polymer, the monomer A' has excellent polymerizability and can play the role of polymer backbone. Preferably, in the monomer A' represented by formula (IV), R1, R2 and R3 are each independently selected from -H or C1-C2 alkyl.

[0045] According to the present invention, in the preparation method of the polymer, the monomer B' can make the obtained polymer more soluble in water and can resist the hydrolysis of the amide groups in the obtained polymer by salt ions in the solution. Preferably, in the monomer B' shown in formula (V), R4, R5 and R6 are each independently selected from -H or C1-C2 alkyl; R7 and R8 are -CH3; and R9 is -CH2-.

[0046] According to the present invention, in the preparation method of the polymer, the monomer C' has a relatively large 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, and the hydration capacity 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 R is independently selected from -H or C1-C2 alkyl; 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.

[0047] 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.

[0048] 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.

[0049] 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 make the prepared polymer have better salt resistance and better water solubility.

[0050] According to the present invention, in the preparation method of 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.

[0051] 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.

[0052] According to the present invention, the cosolvent may be 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.

[0053] According to the present invention, in the method for preparing the polymer, preferably, the weight ratio of the initiator:monomer C' is 1:(10-1000).

[0054] According to the present invention, in the method for preparing the polymer, the initiator has a relatively wide restriction, and a conventional initiator for free radical polymerization reaction may be used, such as an azo initiator, a peroxide initiator or a redox system initiator.

[0055] 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), azoisobutylcyanoformamide (CABN), azobiscyclohexylcarbonitrile (ACCN), azobiscyanovaleric acid (ACVA), azobisisopropylimidazoline (AIP), azobisisobutyronitrile (AIBN), azobisisovaleronitrile (AMBN) and azobisisoheptanenitrile (ABVN).

[0056] 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.

[0057] 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.

[0058] 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.

[0059] According to the present invention, in the preparation method of the polymer, when the emulsion polymerization method is adopted, the organic matter can be selected from at least one of 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).

[0060] According to the present invention, in the method for preparing the polymer, the conditions of the polymerization reaction include: pH value of 4-11, temperature of 0-90° C., and time of 2-24 h.

[0061] 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.

[0062] According to some preferred embodiments of the present invention, the process of preparing the polymer by aqueous solution polymerization comprises:

[0063] (1) According to the above species and proportions, the monomer A', monomer B', monomer C', a co-solvent and water are mixed to obtain a reaction system;

[0064] In the reaction system, the total monomer concentration of the monomer A', the monomer B' and the monomer C' is 0.1-50 wt %;

[0065] (2-1) adding an initiator to the reaction system, and carrying out a first polymerization reaction under a protective atmosphere to obtain a first product system;

[0066] Wherein, the conditions of the first polymerization reaction include: pH value of 4-11, temperature of 0-30°C, and time of 1-8h;

[0067] (2-2) subjecting the first product system to a second polymerization reaction, and granulating, drying and pulverizing the obtained product colloid to obtain the polymer;

[0068] The conditions of the second polymerization reaction include: pH value of 4-11, temperature of 50-90° C., and time of 1-6 h.

[0069] According to some preferred embodiments of the present invention, the process of preparing the polymer by emulsion polymerization comprises:

[0070] (1) According to the above species and proportions, the monomer A', monomer B', monomer C', co-solvent, organic solvent and water are mixed to obtain an emulsion system;

[0071] In the emulsion system, the total monomer concentration of the monomer A', the monomer B' and the monomer C' is 1-30 wt%;

[0072] (2-1) adding an initiator to the emulsion system, and carrying out a first polymerization reaction under a protective atmosphere to obtain a first product system;

[0073] Wherein, the conditions of the first polymerization reaction include: pH value of 4-11, temperature of 0-30°C, and time of 1-16h;

[0074] (2-2) subjecting the first product system to a second polymerization reaction, filtering, drying and pulverizing the obtained product colloid to obtain the polymer;

[0075] The conditions of the second polymerization reaction include: pH value of 4-11, temperature of 40-70° C., and time of 1-8 h.

[0076] The polymer prepared by the method of the present invention has a relatively 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 mineralization of 1100-6000 mg / L. The apparent viscosity of the polymer brine solution at 45° C. is 20-80 mPa·s. The polymer is used as an oil displacement agent to significantly improve the oil displacement effect and increase the recovery rate.

[0077] The third aspect of the present invention provides a polymer obtained by the method described in the second aspect.

[0078] 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.

[0079] The fourth aspect of the present invention provides use of the polymer described in the first aspect or the third aspect as an oil displacement agent in the exploitation of low permeability oil reservoirs.

[0080] 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 mineralization environment. As an oil displacement agent, it can significantly improve the recovery rate of oil reservoirs (especially low permeability oil reservoirs).

[0081] The present invention will be described in detail below by way of examples. In the following examples and comparative examples, unless otherwise specified, all are conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial sources.

[0082] In the following examples and comparative examples, the weight ratio of the structural units contained in the prepared polymers is calculated based on the feed amounts of the raw materials.

[0083] Example 1

[0084] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), after fully dissolving, to obtain a reaction system;

[0085] 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; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 25wt%;

[0086] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:125), and carrying out a first polymerization reaction at 20°C for 2 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as P1);

[0087] The infrared spectrum test of P1 shows the following results: Figure 1 As shown, in Figure 1 Medium, 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.

[0088] In P1, structural unit A Structural unit B Structural unit C The molar ratio of is 138.6:46.2:1. The viscosity average molecular weight of P1 is 652 g / mol.

[0089] Example 2

[0090] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), after fully dissolving, to obtain a reaction system;

[0091] The molar ratio of monomer A':monomer B':monomer C' is 135:45:1; the weight ratio of cosolvent:monomer C' is 1:3; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 25wt%;

[0092] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:125), and carrying out a first polymerization reaction at 20°C for 2 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as P2);

[0093] In P2, the 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.

[0094] Example 3

[0095] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), after fully dissolving, to obtain a reaction system;

[0096] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:7; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 28wt%;

[0097] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:100), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as P3);

[0098] 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.

[0099] Example 4

[0100] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), after fully dissolving, to obtain a reaction system;

[0101] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:2; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 28wt%;

[0102] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:100), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as P4);

[0103] 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.

[0104] Example 5

[0105] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), after fully dissolving, to obtain a reaction system;

[0106] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:2; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 28wt%;

[0107] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:100), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The obtained product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as P5);

[0108] In P5, structural unit A Structural unit B Structural unit C The molar ratio of is 60:20:1. The viscosity average molecular weight of P5 is 247g / mol.

[0109] Example 6

[0110] (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 dodecylbenzene sulfonate), after being fully dissolved, mixed with petroleum ether, added with 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), and then fully stirred to obtain an emulsion system;

[0111] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:2; in the emulsion system, the total monomer concentration of monomer A', monomer B' and monomer C' is 25wt%;

[0112] (2) adding an initiator (azobisisovaleronitrile, i.e., AMBN) to the above emulsion system (the weight ratio of initiator to monomer C' is 1:30), and carrying out a first polymerization reaction at 30° C. for 12 h under a nitrogen atmosphere, and then heating to 70° C. for a second polymerization reaction for 4 h. The obtained product colloid is filtered, dried, and crushed to obtain a white polymer powder (denoted as P6);

[0113] 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.

[0114] Example 7

[0115] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium dodecylbenzenesulfonate), after fully dissolving, to obtain a reaction system;

[0116] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:5; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 28wt%;

[0117] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:100), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as P7);

[0118] 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.

[0119] Example 8

[0120] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (sodium hexadecylbenzenesulfonate), after fully dissolving, to obtain a reaction system;

[0121] The molar ratio of monomer A':monomer B':monomer C' is 60:20:1; the weight ratio of cosolvent:monomer C' is 1:1; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 28wt%;

[0122] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:100), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as P8);

[0123] In P8, structural unit A Structural unit B Structural unit C The molar ratio of is 60:20:1. The viscosity average molecular weight of P8 is 452g / mol.

[0124] Comparative Example 1

[0125] (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;

[0126] 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%;

[0127] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer A' is 1:6000), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The obtained product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as D1);

[0128] 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.

[0129] Comparative Example 2

[0130] (1) Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C'( C) and a cosolvent (dodecylbenzenesulfonic acid), after fully dissolving, to obtain a reaction system;

[0131] The molar ratio of monomer B': monomer C' is 20:1; the weight ratio of cosolvent: monomer C' is 1:2; in the reaction system, the total monomer concentration of monomer B' and monomer C' is 28wt%;

[0132] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:100), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The obtained product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as D2);

[0133] 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.

[0134] Comparative Example 3

[0135] (1) Monomer A' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (dodecylbenzenesulfonic acid), after being fully dissolved, a reaction system is obtained;

[0136] The molar ratio of monomer A':monomer C' is 60:1; the weight ratio of cosolvent:monomer C' is 1:2; in the reaction system, the total monomer concentration of monomer A' and monomer C' is 28wt%;

[0137] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:100), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as D3);

[0138] 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.

[0139] Comparative Example 4

[0140] (1) Monomer A' Monomer B' and water to prepare a solution, adjust the pH value of the solution to 7.0, and then add monomer C' and a cosolvent (dodecylbenzenesulfonic acid), after being fully dissolved, a reaction system is obtained;

[0141] The molar ratio of monomer A':monomer B':monomer C' is 600:200:1; the weight ratio of cosolvent:monomer C' is 1:2; in the reaction system, the total monomer concentration of monomer A', monomer B' and monomer C' is 28wt%;

[0142] (2) adding an initiator (potassium persulfate-sodium thiosulfate) to the above reaction system (the weight ratio of initiator to monomer C' is 1:50), and carrying out a first polymerization reaction at 25°C for 2.5 hours under a nitrogen atmosphere, and then heating to 80°C for a second polymerization reaction for 4 hours. The resulting product colloid is granulated, dried and crushed to obtain a white polymer powder (denoted as D4);

[0143] 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.

[0144] Test Case

[0145] 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.

[0146] 1. Salt resistance test

[0147] Polymers P1-P8, D1-D4 and commercially available oil displacement agent A (low molecular weight polyacrylamide, manufacturer: Daqing Refining and Chemical Company, molecular weight 709g / mol) were respectively mixed with saline water with a salinity of 2410mg / L (2410mg of NaCl dissolved in 1L of water) to prepare polymer brine solutions with a polymer concentration of 1000mg / L (respectively recorded as L1-L8 and DL1-DL5). The apparent viscosity of the above polymer brine solutions was measured using a US Brookfield DV-II viscometer with a 0# rotor at a speed of 6rpm and a temperature of 45°C. The results are shown in Table 1.

[0148] Table 1

[0149] Test subjects Apparent viscosity (45℃) / mPa·s L1 67.7 L2 48.3 L3 31.3 L4 38.6 L5 32.6 L6 29.7 L7 21.9 L8 41.3 DL1 11.5 DL2 4.7 DL3 / DL4 10.2 DL5 (containing commercially available oil displacement agent A) 10.7

[0150] Note: D3 is not soluble in the saline of this concentration, so the apparent viscosity of D3 saline solution cannot be tested.

[0151] 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 resistance. Under the same conditions, the polymer brine solutions of polymers D1-D4 prepared in Comparative Examples 1-4 and commercially available oil displacement agent A have low apparent viscosities and significantly inferior salt resistance to P1-P8.

[0152] 2. Oil displacement performance test

[0153] Polymers P1-P8, D1, D2, D4 and the commercially available oil displacement agent A were respectively prepared with water to prepare polymer aqueous solutions with an apparent viscosity of 18 mPa·s (respectively denoted as Q1-Q8, DQ1-DQ4), and the above polymer aqueous solutions Q1-Q8 and DQ1-DQ4 were used to conduct oil displacement experiments on artificial rectangular cores (core permeability of 100 mD), the injection rate of the polymer aqueous solution was 0.3 mL / min, and the volume of the injected polymer aqueous solution was 0.9 PV, and the polymer recovery capacity was evaluated. The results are shown in Table 2.

[0154] Table 2

[0155]

[0156]

[0157] As can be seen from Table 2, in the above-mentioned oil displacement experiment, the polymers P1-P8 provided by the present invention showed excellent oil displacement effect, and the recovery rates were all higher than 9.5% under the experimental conditions. Compared with ordinary low molecular weight polymers, the low molecular weight salt-resistant polymer provided by the present invention has a higher viscosity of aqueous solution at the same concentration, and the molecular chain is more rigid and elastic, and it is easier to bring out the remaining oil from the reservoir pores.

[0158] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope 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 5, 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.

Images