A viscoelastic polymer particle oil displacement agent and its preparation method and application

Abstract

The present invention belongs to the technical field of tertiary oil recovery, and specifically relates to a viscoelastic polymer particle oil-displacing agent and its preparation method and application. The preparation method is as follows: nitrogen is passed into the reactor to ensure that the material in the reactor is isolated from the air; acrylamide, 1-vinyl-2-pyrrolidone, p-styrenesulfonic acid, 4-methacrylamide salicylic acid, 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, sodium dihydrogen phosphate, carboxymethyl cellulose, dodecylphenol polyoxyethylene ether, deionized water are sequentially added, stirred, and pH is adjusted to 7-8; an initiator is added to a high-position drop-adding tank, and is added dropwise to a reactor. During the drop-adding process, the solution automatically heats up, continues to react, heats up, and is kept warm for reaction, and is cooled to less than 40°C, and pH is adjusted to 7-8; the above-mentioned mixed solution is dried and granulated to obtain a product viscoelastic polymer particle oil-displacing agent. The present invention has the characteristics of high interfacial activity, high viscosity, and shear resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of tertiary oil recovery, and in particular relates to a viscoelastic polymer particle oil displacement agent and a preparation method and application thereof. Background Art

[0002] Polymer flooding is the process of injecting high molecular polymers into the formation in the form of liquid through water injection wells. It can produce a comprehensive effect in the formation, such as viscosity increase of injected water, resistance reduction of crude oil, oil-water miscibility, and particle blockage of high permeability layers. Its purpose is to block the high permeability layer of the water injection well, increase the seepage resistance of the injected water, balance its water absorption profile, reduce the mobility ratio of oil and water, further drive out the residual oil in the formation, and form an active "oil wall" in the formation, producing a "piston-type" oil displacement effect, so as to reduce the water content of the oil well and increase the crude oil recovery rate.

[0003] At present, the main polymer used for polymer flooding on the market is polyacrylamide, which is a linear water-soluble polymer and one of the most widely used water-soluble polymer compounds. In water, it easily forms hydrogen bonds with water, is easily soluble in water, and has a large hydrodynamic volume after hydration.

[0004] However, polyacrylamide is easily hydrolyzed in formation water and is sensitive to some ions in formation water, so the viscosity of the polymer will drop quickly. In addition, after the polymer solution undergoes strong shear in the reservoir pores, its polymer molecular chains will deform and break, resulting in a rapid decrease in the viscosity of the polymer solution. Moreover, polyacrylamide has no active groups, which greatly affects the recovery effect.

[0005] Cross-linking of polyacrylamide molecules can obtain branched or network structures, which greatly improves the properties of polyacrylamide, especially increases the apparent viscosity and shear resistance, and accesses active groups, making it a good choice for obtaining high recovery rates.

[0006] CN114805677B discloses a polymer oil-displacing agent and a preparation method thereof, which relates to the field of oilfield chemical additives and polymer polymerization. The method comprises: reacting nitrile compounds, fuming sulfuric acid and long-chain olefins to obtain a dendritic branched monomer; mixing the dendritic branched monomer, acrylamide, acrylic acid, deionized water and a pH regulator to obtain a mixed solution; introducing nitrogen into the mixed solution, and then adding an initiator to initiate a polymerization reaction to obtain the polymer oil-displacing agent. The polymer oil-displacing agent prepared by the invention has a strong chelating effect on calcium and magnesium ions, is suitable for operations in high-mineralization areas, is salt-resistant, high-temperature-resistant and has high thermal stability. After 3 months under anaerobic conditions at 120°C, the solution viscosity still has a high retention rate. However, the apparent viscosity of the invention is lower than 80mPa•s, and the effect of water plugging and profile adjustment is not ideal, which will affect the oil displacement effect.

[0007] CN104910321B discloses a ternary copolymer cationic polyacrylamide. The preparation of the product includes the steps of preparing the cationic monomer E-AM, preparing the monomer aqueous solution, and ternary copolymerization of AM, E-AM, and DAC. The ternary copolymer cationic polyacrylamide provided by the invention better reflects the characteristics of high polymerization activity and good flocculation effect of the E-AM monomer and the ease of preparing high molecular weight copolymers by DAC. Compared with the existing common flocculant products, the present invention has the characteristics of high cationicity and high molecular weight, and exhibits excellent flocculation performance. The actual test results show that it also has the characteristics of high solubility, so it is suitable for use as a flocculant in sewage treatment projects. The invention is cationic and has a good effect when used as a coagulant aid in sewage treatment, but the invention is not suitable for oil extraction, so the scope of use is limited. Summary of the invention

[0008] The present invention aims at the deficiencies of the prior art and provides a viscoelastic polymer particle oil displacement agent and a preparation method and application thereof. The present invention has the characteristics of high interfacial activity, high viscosity and shear resistance.

[0009] In order to achieve the above objectives, one of the objectives of the present invention is to disclose a viscoelastic polymer particle oil-displacing agent, the molecular structure of the oil-displacing agent is as follows:

[0010]

[0011] in:

[0012] a=2000-40000;

[0013] b = 100000-1000000;

[0014] c = 20000-400000;

[0015] d = 10000-200000;

[0016] e=10000-200000;

[0017] f=2000-40000;

[0018] g = 100000-1000000;

[0019] h = 20000-400000;

[0020] i = 10000-20000;

[0021] j=10000-200000.

[0022] The viscosity average molecular weight of the oil displacing agent is 40,000,000-60,000,000.

[0023] Another object of the present invention is to disclose a method for preparing the viscoelastic polymer particle oil-displacing agent, the specific steps of which are as follows:

[0024] (1) nitrogen is introduced into the reactor to replace the air therein. During the later synthesis process, nitrogen is introduced to ensure that the materials in the reactor are isolated from the air. acrylamide, 1-vinyl-2-pyrrolidone, p-styrenesulfonic acid, 4-methylacrylamidosalicylic acid, 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, sodium dihydrogen phosphate, carboxymethyl cellulose, dodecylphenol polyoxyethylene ether, and deionized water are added in sequence, stirred, and the pH is adjusted to 7-8 with sodium hydroxide solution;

[0025] (2) Add the initiator to the high-position drop-adding tank and drip it into the reactor. During the dripping process, the solution automatically heats up and continues to react for 0.5-1h. Heat to 55-70°C and keep the temperature for 4-10h. Cool down to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0026] (3) The mixed solution is dried and granulated into particles with a diameter of 1-4 mm to obtain a viscoelastic polymer particle oil displacement agent.

[0027] In the present invention, preferably, the molar ratio of 1-vinyl-2-pyrrolidone, p-styrenesulfonic acid, 4-methylacrylamidosalicylic acid, 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane and acrylamide is 0.2-0.4:0.1-0.2:0.1-0.2:0.02-0.04:1.

[0028] Preferably, in step (1), the weight ratio of sodium dihydrogen phosphate, carboxymethyl cellulose, dodecylphenol polyoxyethylene ether, deionized water and acrylamide is 0.02-0.04: 0.01-0.02: 0.02-0.04: 8-10: 1.

[0029] Preferably, in step (2), the initiator is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 8-12wt%, the concentration of sodium bisulfite is 2-5wt%, and the weight ratio of initiator to acrylamide is 0.2-0.6:1.

[0030] More preferably, the persulfate is one of potassium persulfate, ammonium persulfate and sodium persulfate.

[0031] The reaction equation for the synthesis of the viscoelastic polymer particle oil-displacing agent of the present invention is as follows:

[0032]

[0033]

[0034] The third object of the present invention is to disclose the application of the above oil displacement agent in polymer flooding.

[0035] The viscoelastic polymer particle oil-displacing agent of the invention is a five-component high molecular polymer with acrylamide, 1-vinyl-2-pyrrolidone, p-styrene sulfonic acid, 4-methacrylamide salicylic acid and 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane as monomers. Acrylamide is the main monomer for polymerization; 1-vinyl-2-pyrrolidone is a rigid monomer, which can greatly increase the viscoelasticity and shear resistance of the product; p-styrene sulfonic acid molecules contain benzene ring structure and sulfonic acid anions, which can improve shear resistance and reduce oil-water interfacial tension; 4-methacrylamide salicylic acid molecules contain benzene ring structure and carboxylic acid anions, which can improve shear resistance and reduce oil-water interfacial tension; 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane is a special surfactant lipophilic monomer, which has lower interfacial tension than conventional surfactants and can better strip crude oil. It contains two double bonds and is a cross-linking agent, which can greatly increase the molecular weight and viscosity of the polymer; carboxymethyl cellulose and dodecylphenol polyoxyethylene ether are dispersants and non-ionic emulsifiers, which can improve the quality of the polymerization reaction.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] (1) The viscoelastic polymer particle oil displacement agent of the present invention has good interfacial activity, and the interfacial tension at a concentration of 300 mg / L reaches 0.1×10 -3 Below mN / m;

[0038] (2) The viscoelastic polymer particle oil displacement agent of the present invention has a relatively high surface viscosity. At 70°C, the viscosity at a concentration of 1500 mg / L reaches 105 mPa•s or above;

[0039] (3) The viscoelastic polymer particle oil displacement agent of the present invention has shear resistance. After 6 hours of shearing, the viscosity retention rate can reach a maximum of more than 96%. DETAILED DESCRIPTION

[0040] 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.

[0041] The technical solution of the present invention is further described below in conjunction with specific embodiments:

[0042] Example 1

[0043] (1) nitrogen was introduced into the reactor to replace the air therein. During the later synthesis process, nitrogen was introduced to ensure that the materials in the reactor were isolated from the air. 0.5 mol acrylamide, 0.1 mol 1-vinyl-2-pyrrolidone, 0.1 mol p-styrenesulfonic acid, 0.1 mol 4-methylacrylamidosalicylic acid, 0.01 mol 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 0.71 g sodium dihydrogen phosphate, 0.355 g carboxymethyl cellulose, 0.71 g dodecylphenol polyoxyethylene ether, and 284 g deionized water were added in sequence, stirred, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0044] (2) 7.1 g of initiator was added to the high-position drop tank. The initiator contained 12 wt% sodium persulfate and 5 wt% sodium bisulfite. During the drop addition, the solution automatically heated up and continued to react for 0.5 h. The temperature was raised to 70 ° C and kept at this temperature for 4 h. The temperature was lowered to below 40 ° C and the pH was adjusted to 7-8 with sodium hydroxide.

[0045] (3) The mixed solution is dried and granulated into particles with a diameter of 1-4 mm to obtain a viscoelastic polymer particle oil displacement agent.

[0046] Example 2

[0047] (1) nitrogen was introduced into the reactor to replace the air therein. During the later synthesis process, nitrogen was introduced to ensure that the materials in the reactor were isolated from the air. 0.5 mol acrylamide, 0.12 mol 1-vinyl-2-pyrrolidone, 0.09 mol p-styrenesulfonic acid, 0.09 mol 4-methylacrylamidosalicylic acid, 0.012 mol 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 0.82 g sodium dihydrogen phosphate, 0.44 g carboxymethyl cellulose, 0.84 g dodecylphenol polyoxyethylene ether, and 314 g deionized water were added in sequence, stirred, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0048] (2) 10.3 g of initiator was added to the high-position drop tank. The initiator contained 12 wt% sodium persulfate and 4 wt% sodium bisulfite. During the drop addition process, the solution automatically heated up and continued to react for 1 hour. The temperature was heated to 55°C and kept for 10 hours. The temperature was then lowered to below 40°C and the pH was adjusted to 7-8 with sodium hydroxide.

[0049] (3) The mixed solution is dried and granulated into particles with a diameter of 1-4 mm to obtain a viscoelastic polymer particle oil displacement agent.

[0050] Example 3

[0051] (1) nitrogen was introduced into the reactor to replace the air therein. nitrogen was introduced during the later synthesis process to ensure that the materials in the reactor were isolated from the air; 0.5 mol acrylamide, 0.14 mol 1-vinyl-2-pyrrolidone, 0.08 mol p-styrenesulfonic acid, 0.07 mol 4-methylacrylamidosalicylic acid, 0.015 mol 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 0.91 g sodium dihydrogen phosphate, 0.68 g carboxymethyl cellulose, 0.91 g dodecylphenol polyoxyethylene ether, and 328 g deionized water were added in sequence, stirred, and the pH was adjusted to 7-8 with sodium hydroxide solution;

[0052] (2) 15.8 g of initiator was added to the high-position drop tank. The initiator contained 11 wt% ammonium persulfate and 4 wt% sodium bisulfite. During the drop addition process, the solution automatically heated up and continued to react for 1 hour. The temperature was heated to 58°C and kept for 8 hours. The temperature was then lowered to below 40°C and the pH was adjusted to 7-8 with sodium hydroxide.

[0053] (3) The mixed solution is dried and granulated into particles with a diameter of 1-4 mm to obtain a viscoelastic polymer particle oil displacement agent.

[0054] Example 4

[0055] (1) nitrogen was introduced into the reactor to replace the air therein. During the later synthesis process, nitrogen was introduced to ensure that the materials in the reactor were isolated from the air. 0.5 mol acrylamide, 0.16 mol 1-vinyl-2-pyrrolidone, 0.06 mol p-styrenesulfonic acid, 0.05 mol 4-methylacrylamidosalicylic acid, 0.017 mol 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.33 g sodium dihydrogen phosphate, 0.66 g carboxymethyl cellulose, 1.22 g dodecylphenol polyoxyethylene ether, and 334 g deionized water were added in sequence, stirred, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0056] (2) 16.9 g of initiator was added to the high-position drop tank. The initiator contained 10 wt% ammonium persulfate and 3 wt% sodium bisulfite. During the drop addition process, the solution automatically heated up and continued to react for 0.8 h. The temperature was heated to 70 ° C and kept at this temperature for 6 h. The temperature was then lowered to below 40 ° C and the pH was adjusted to 7-8 with sodium hydroxide.

[0057] (3) The mixed solution is dried and granulated into particles with a diameter of 1-4 mm to obtain a viscoelastic polymer particle oil displacement agent.

[0058] Example 5

[0059] (1) nitrogen was introduced into the reactor to replace the air therein. nitrogen was introduced during the later synthesis process to ensure that the materials in the reactor were isolated from the air; 0.5 mol acrylamide, 0.18 mol 1-vinyl-2-pyrrolidone, 0.07 mol p-styrenesulfonic acid, 0.08 mol 4-methylacrylamidosalicylic acid, 0.019 mol 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.42 g sodium dihydrogen phosphate, 0.59 g carboxymethyl cellulose, 1.35 g dodecylphenol polyoxyethylene ether, and 355 g deionized water were added in sequence, stirred, and the pH was adjusted to 7-8 with sodium hydroxide solution;

[0060] (2) 21.3 g of initiator was added to the high-position drop tank. The initiator contained 8 wt% potassium persulfate and 2 wt% sodium bisulfite. During the drop addition, the solution automatically heated up and continued to react for 0.75 h. The temperature was heated to 65 ° C and kept for 8 h. The temperature was lowered to below 40 ° C and the pH was adjusted to 7-8 with sodium hydroxide.

[0061] (3) The mixed solution is dried and granulated into particles with a diameter of 1-4 mm to obtain a viscoelastic polymer particle oil displacement agent.

[0062] Example 6

[0063] (1) nitrogen was introduced into the reactor to replace the air therein. nitrogen was introduced during the later synthesis process to ensure that the materials in the reactor were isolated from the air; 0.5 mol acrylamide, 0.2 mol 1-vinyl-2-pyrrolidone, 0.05 mol p-styrenesulfonic acid, 0.06 mol 4-methylacrylamidosalicylic acid, 0.02 mol 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1.13 g sodium dihydrogen phosphate, 0.71 g carboxymethyl cellulose, 1.42 g dodecylphenol polyoxyethylene ether, and 346 g deionized water were added in sequence, stirred, and the pH was adjusted to 7-8 with sodium hydroxide solution;

[0064] (2) 18.4 g of initiator was added to the high-position drop tank. The initiator contained 9 wt% potassium persulfate and 3 wt% sodium bisulfite. During the drop addition process, the solution automatically heated up and continued to react for 1 hour. The temperature was heated to 70°C and kept for 10 hours. The temperature was then lowered to below 40°C and the pH was adjusted to 7-8 with sodium hydroxide.

[0065] (3) The mixed solution is dried and granulated into particles with a diameter of 1-4 mm to obtain a viscoelastic polymer particle oil displacement agent.

[0066] Example 7 Test of interfacial tension

[0067] The viscoelastic polymer particle oil-displacing agent of the present invention (Examples 1-6) was prepared into a solution with a concentration of 300 mg / L with tap water, and the interfacial tension was tested at 70°C according to the method in SY / T 5370-2018 "Surface and interfacial tension determination method". The oil phase was crude oil from Dongxin Oilfield, Shengli Oilfield, and the viscosity at 70°C was 255 mPa•s.

[0068] A comparative experiment was conducted using polyacrylamide produced by Shandong Wanhua Chemical Technology Co., Ltd. The test results are shown in Table 1.

[0069] It can be seen from Table 1 that the interfacial tension of the viscoelastic polymer particle oil displacement agent (Examples 1-6) of the present invention at a concentration of 300 mg / L is 0.1×10 -3 Below mN / m, the lowest is 0.056×10 -3 mN / m (Example 1); while the interfacial tension of the polyacrylamide of Shandong Wanhua Chemical Technology Co., Ltd. in the comparative example is 15mN / m, which is significantly higher than that of the present invention.

[0070] Example 8 Test of apparent viscosity

[0071] The viscoelastic polymer particle oil-displacing agent of the present invention (Examples 1-6) was prepared into a mother solution with a concentration of 5000 mg / L using tap water.

[0072] The properties of water at a joint station of Dongxin Oilfield, Shengli Oilfield: mineralization, 32000mg / L; hardness, 1700mg / L; temperature, 70℃.

[0073] The mother liquor and the water from the joint station were mixed evenly in a volume ratio of 3:7, and the apparent viscosity was tested using a Haake rheometer at 70°C.

[0074] A comparative experiment was conducted using polyacrylamide produced by Shandong Wanhua Chemical Technology Co., Ltd. The test results are shown in Table 1.

[0075] It can be seen from Table 1 that the apparent viscosity of the viscoelastic polymer particle oil-displacing agent of the present invention (Examples 1-6) at a concentration of 1500 mg / L at 70°C all reached 105 mPa•s or above, with the highest reaching 128 mPa•s (Example 6); while the apparent viscosity of the polyacrylamide of Shandong Wanhua Chemical Technology Co., Ltd. in the comparative example was 27 mPa•s, which was significantly lower than that of the present invention.

[0076] Example 9 Shear resistance test

[0077] The sample in Example 8 was heated at 70°C and 170S -1 Shear continuously for 6 hours under the conditions, test the apparent viscosity, and calculate the viscosity retention rate.

[0078] A comparative experiment was conducted using polyacrylamide produced by Shandong Wanhua Chemical Technology Co., Ltd. The test results are shown in Table 1.

[0079] Table 1 Test results of apparent viscosity and shear resistance

[0080]

[0081] It can be seen from Table 1 that the viscoelastic polymer particle oil-displacing agent of the present invention (Examples 1-6) at 70°C and 170S -1 Under the conditions of continuous shearing for 6 hours, the viscosity retention rate reached more than 96%, with the highest reaching 97.7% (Example 6); while the viscosity retention rate of polyacrylamide of Shandong Wanhua Chemical Technology Co., Ltd. in the comparative example was 74.1%, which was significantly lower than that of the present invention.

[0082] 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 method for preparing a viscoelastic polymer particle oil-displacing agent, characterized in that: The specific steps of the preparation method are as follows: (1) nitrogen is introduced into the reactor to replace the air therein. During the later synthesis process, nitrogen is introduced to ensure that the materials in the reactor are isolated from the air. acrylamide, 1-vinyl-2-pyrrolidone, p-styrenesulfonic acid, 4-methylacrylamidosalicylic acid, 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, sodium dihydrogen phosphate, carboxymethyl cellulose, dodecylphenol polyoxyethylene ether, and deionized water are added in sequence, stirred, and the pH is adjusted to 7-8 with sodium hydroxide solution; (2) Add the initiator to the high-position drop-adding tank and drip it into the reactor. During the dripping process, the solution automatically heats up and continues to react for 0.5-1h. Heat to 55-70°C and keep the temperature for 4-10h. Cool down to below 40°C and adjust the pH to 7-8 with sodium hydroxide. (3) drying and granulating the mixed solution to obtain a viscoelastic polymer granular oil displacement agent with a particle diameter of 1-4 mm; The molar ratio of 1-vinyl-2-pyrrolidone, p-styrenesulfonic acid, 4-methylacrylamidosalicylic acid, 1,6-di(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane and acrylamide is 0.2-0.4: 0.1-0.2: 0.1-0.2: 0.02-0.04: 1; The molecular structural formula of the oil displacing agent is as follows: ， in: a=2000-40000； b=100000-1000000； c=20000-400000； d=10000-200000； e=10000-200000； f=2000-40000； g=100000-1000000； h=20000-400000； i=10000-20000； j=10000-200000。 2. The preparation method according to claim 1, characterized in that: In step (1), the weight ratio of sodium dihydrogen phosphate, carboxymethyl cellulose, dodecylphenol polyoxyethylene ether, deionized water and acrylamide is 0.02-0.04: 0.01-0.02: 0.02-0.04: 8-10:

1.

3. The preparation method according to claim 1, characterized in that: In step (2), the initiator is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 8-12wt% and the concentration of sodium bisulfite is 2-5wt%.

4. The preparation method according to claim 3, characterized in that: The persulfate is one of potassium persulfate, ammonium persulfate and sodium persulfate.

5. The preparation method according to claim 1 or 3, characterized in that: The weight ratio of the initiator to acrylamide is 0.2-0.6:

1.

6. A viscoelastic polymer particle oil-displacing agent, characterized in that: The molecular structural formula of the oil displacing agent is as follows: ， in: a=2000-40000； b=100000-1000000； c=20000-400000； d=10000-200000； e=10000-200000； f=2000-40000； g=100000-1000000； h=20000-400000； i=10000-20000； j=10000-200000。 7. The viscoelastic polymer particle oil-displacing agent according to claim 6, characterized in that: The viscosity average molecular weight of the oil displacing agent is 40,000,000-60,000,000.

8. Use of the viscoelastic polymer particle oil-displacing agent according to claim 7 in polymer flooding.

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