Stain-resistant salt-tolerant polymer for oil extraction and synthesis method thereof

Abstract

The invention discloses an anti-pollution and salt-tolerant polymer for oil extraction and a synthetic method, relates to the field of polymers for oil extraction, and discloses the anti-pollution and salt-tolerant polymer for oil extraction and the synthetic method, and the anti-pollution and salt-tolerant polymer for oil extraction is prepared by carrying out polymerization reaction on an aqueous phase material comprising a monomer A and a monomer B and then hydrolyzing. The viscosity-average molecular weight of the polymer is 1 million to 20 million, the hydration radius of a molecular chain is effectively increased, the rigidity and curling resistance of the polymer in high-temperature and high-salinity saline water or sewage are enhanced, and the polymer has excellent pollution resistance and salt resistance, can be used for oil field on-site sewage preparation and sewage dilution, and meanwhile, can be used for oil field on-site sewage treatment. The polymer has better viscoelasticity and a linear structure, so that the polymer has better injection performance and oil displacement performance, is especially suitable for high-temperature and hypersalinity underground water reservoirs, and can better improve the recovery efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemicals, and specifically to an anti-fouling and salt-tolerant polymer for oil production and a synthesis method thereof. Background Art

[0002] The stable supply of oil resources is inseparable from the stable development of the social economy and the guarantee of the quality of people's production and life. As the most important unit for oil extraction and gathering and transportation, the quality of the oilfield's extraction technology will directly affect the oil production and quality. Chemical flooding is one of the most effective methods for improving the crude oil recovery rate among many tertiary oil recovery technologies. Polymer flooding can increase the crude oil recovery rate by more than 10% on the basis of water flooding. It is the most mature and widely used technology in current chemical flooding, and it is of great significance for increasing the crude oil production.

[0003] With the gradual expansion of the scale of tertiary oil recovery, the development targets have shifted from Class I and Class II A oil layers to Class II B and Class III oil layers. The physical properties of the oil layers have deteriorated, the matching difficulty has increased, and the displacement effect has become worse. At the same time, to meet the environmental protection requirements, sewage cannot be discharged externally. The preparation method in some polymer flooding blocks has changed from clear preparation and clear dilution (prepared with fresh water and diluted with fresh water) to clear preparation and sewage dilution (prepared with fresh water and diluted with sewage), and the dry powder dosage has increased significantly. The recovery rate has decreased by 1-3 percentage points compared with clear preparation and clear dilution. To explore the technology of reducing the dry powder dosage and further improving the recovery rate under the conditions of polymer sewage system, combined with the actual situation analysis of the oilfield, using a new type of sewage-resistant polymer is one of the effective ways to solve the problem of large polymer dosage in sewage dilution.

[0004] Polyacrylamide is the most widely used polymer flooding agent in current oilfield tertiary oil recovery. Ordinary polymers have low viscosity in high-temperature and high-salinity water, and problems such as "fingering" and "channeling" are likely to occur during the oil displacement process, resulting in low displacement efficiency. Although many scientific research institutions and enterprises have carried out research on anti-fouling and salt-tolerant polymers, the actual anti-fouling and salt-tolerant properties of anti-fouling and salt-tolerant polymers on the market mostly cannot meet the needs of the oilfield. Therefore, there is an urgent need for polymers with anti-fouling, salt-tolerant, good salt-resistant properties, and can be prepared with on-site sewage in the current oilfield to improve the oil reservoir recovery efficiency. Summary of the Invention

[0005] In view of the above problems, the present invention aims to provide an anti-fouling and salt-tolerant polymer for oil production, with a molecular weight adjustable between 1 million and 20 million, which can be applied to the exploitation of Class I, Class II, and Class III oil reservoirs with various permeabilities; under high-temperature and high-salinity conditions, the polymer has excellent anti-fouling and salt-tolerant properties, can be prepared and diluted with sewage, and can preferably improve the polymer flooding recovery rate. At the same time, the present invention also provides a synthesis method of the anti-fouling and salt-tolerant polymer.

[0006] In a first aspect, the present invention provides an anti-fouling and salt-tolerant polymer for oil production, which is prepared from an aqueous phase material including monomer A and monomer B through a polymerization reaction and a hydrolysis reaction. Monomer A is a monomer having the structure shown in formula (a), and monomer B is a monomer having the structure shown in formula (b), as follows:

[0007]

[0008] Wherein, R1, R2 and R3 are each independently selected from -H or an alkyl group of C1-C4; R4, R5 and R6 are each independently selected from -H or an alkyl group of C1-C4; X is selected from H + , K + , Na + or NH4 + ; m is an integer from 3 to 15; n is an integer from 5 to 17; R7 is selected from an alkyl group of C1-C2.

[0009] Furthermore, the viscosity-average molecular weight of the polymer is 1 million - 20 million.

[0010] Furthermore, the polymer is used to prepare a polymer brine solution with a concentration of 1000 mg / L - 3000 mg / L using brine with a salinity of 33000 mg / L, and the apparent viscosity at 85 °C is 30 - 550 mPa·s.

[0011] In a second aspect, the present invention provides a method for synthesizing an anti-fouling and salt-tolerant polymer for oil production, including the following steps:

[0012] (1) Prepare a monomer solution

[0013] The monomer solution includes monomer A, monomer B and deionized water. The mass ratio of monomer A to monomer B is 300 - 400:40 - 55; the total mass of monomer A and monomer B accounts for 30 - 45% of deionized water;

[0014] (2) Pass the monomer solution obtained in step (1) through nitrogen for deoxygenation, and carry out a polymerization reaction in the presence of an initiator to obtain a polymer colloid;

[0015] (3) Add an alkali to the polymer colloid obtained in step (2), raise the temperature to 70 - 99 °C, and keep it warm for 2 - 8 h to carry out a hydrolysis reaction to obtain an anti-fouling and salt-tolerant polymer for oil production.

[0016] Furthermore, the initiator in step (2) includes sulfate initiators, phosphate initiators, peroxide initiators and azo initiators, and the mass ratio of the initiator to monomer A is 1:(10 - 1000).

[0017] Further, the azo initiator can be selected from at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, azoisobutyronitrile carboxamide, dimethyl azobisisobutyrate, azobis (2-methylpropionamidine) dihydrochloride, and azodiisopropylimidazoline hydrochloride.

[0018] Further, the peroxide initiator can be selected from at least one of sodium persulfate, ammonium persulfate, potassium persulfate, hydrogen peroxide, and benzoyl peroxide.

[0019] Further, in step (2), the temperature of the polymerization reaction is -5°C - 50°C, the pH value is 3 - 11, and the reaction time is 1 - 24 h.

[0020] Further, the base in step (3) includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0021] Further, the mass ratio of the base to monomer A in step (3) is 1:(3 - 20).

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0023] After the polymerization of monomer A and monomer B in the present invention, a benzene ring side group is formed in the polymer molecular chain. The benzene ring side group contains two long-chain methylene sulfonic acid groups and alkyl groups. The hydrophilicity and strong charge of the sulfonic acid group endow the polymer with good water solubility and hydrolysis resistance. At the same time, due to the long-chain methylene group having a long flexible molecular chain structure, on the one hand, it greatly increases the rotational radius of the polymer molecular chain, enhances the intermolecular friction and physical entanglement, and improves the viscosity of the polymer. On the other hand, it increases the flexibility of the polymer molecular chain. Since the greater the flexibility of the molecular chain, the more significant the viscoelasticity, the oil displacement performance of the polymer is also improved. Due to the rigid structure of the benzene ring, the polymer molecules maintain good linearity. When the polymer solution is used for oil displacement in the formation, the better linear molecular structure is more likely to pass through small-sized rock pores and throats, improving the sweep efficiency of the polymer solution and increasing the recovery rate.

[0024] Since the polymer contains functional groups such as two long-chain methylene groups, sulfonic acid groups, benzene rings, and alkyl groups at the same time, the rigidity and viscoelasticity of the polymer are greatly enhanced, and it has excellent anti-fouling and salt tolerance properties. The polymer is used to prepare an aqueous polymer solution with a concentration of 1000 mg / L - 3000 mg / L using brine with a salinity of 33000 mg / L. The apparent viscosity of the aqueous polymer solution at 85°C is 30 - 550 mPa·s. Detailed Embodiments

[0025] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1

[0027] Synthesis of an anti-fouling and salt-tolerant polymer for oil production:

[0028] (1) Add 120 g of dichloromethane to a three-necked flask equipped with a stirrer, a dropping funnel, and a thermometer. Start the stirrer, add 20 g of dodecylsulfonyl chloride and 22 g of pentadecylsulfonyl chloride. After complete dissolution, slowly and uniformly add 30 g of 4-methylisopropenyltoluene to the above reaction system through the dropping funnel, keep the reaction temperature at 35 °C, and react for 5.5 h; add 10 g of sodium hydroxide to neutralize to a pH value of 6.6; filter the above reaction system, and the solid matter filtered out is dried to obtain monomer B1;

[0029] (2) Measure 1000 kg of deionized water and add it to the reaction kettle. Start the stirrer, add 350 kg of acrylamide and 52 kg of monomer B1, and stir until completely dissolved; add 0.7 kg of initiator azobisisobutyronitrile; pass nitrogen into the material system for 35 min to remove the dissolved oxygen in the water; add 20 g of sodium bisulfate, keep warm for 8 h to obtain a polymer colloid; send the above polymer colloid to the hydrolysis reaction kettle, add 112 kg of solid sodium hydroxide to the hydrolysis reaction kettle, stir well to mix, heat up to 90 °C, keep warm for 3 h, and then dry, grind, and screen to obtain the anti-fouling and salt-tolerant polymer HLKS-1 for oil production. The reaction equation is as follows:

[0030]

[0031] Example 2

[0032] Synthesis of an anti-fouling and salt-tolerant polymer for oil production:

[0033] (1) Add 120 g of dichloromethane to a three-necked flask equipped with a stirrer, a dropping funnel, and a thermometer. Start the stirrer, add 20 g of dodecylsulfonyl chloride and 22 g of pentadecylsulfonyl chloride. After complete dissolution, slowly and uniformly add 30 g of 4-methylisopropenyltoluene to the above reaction system through the dropping funnel, keep the reaction temperature at 35 °C, and react for 5.5 h; add 10 g of sodium hydroxide to neutralize to a pH value of 6.6; filter the above reaction system, and the solid matter filtered out is dried to obtain monomer B1;

[0034] (2) Weigh 1000 kg of deionized water and add it to the reaction kettle. Start the stirrer, add 350 kg of acrylamide, add 40 kg of monomer B1, and stir until completely dissolved; add 0.35 kg of initiator azobisisobutyronitrile; pass nitrogen into the material system for 35 minutes to remove the dissolved oxygen in the water; add 20 g of sodium bisulfate, keep the temperature at 8 h to obtain a polymer colloid; send the above polymer colloid to the hydrolysis reaction kettle for granulation. Add 35 kg of potassium hydroxide solid to the hydrolysis reaction kettle, stir well to mix, heat up to 90 °C, keep the temperature for 3 h, and then dry, grind and screen to obtain the anti-fouling and salt-resistant polymer HLKS-11 for oil production.

[0035] Example 3

[0036] Synthesis of an anti-fouling and salt-resistant polymer for oil production:

[0037] (1) Add 120 g of dichloromethane to a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. Start the stirrer, add 20 g of dodecylsulfonyl chloride and 22 g of pentadecylsulfonyl chloride. After complete dissolution, slowly and evenly drop 30 g of 4-methylisopropenyltoluene into the above reaction system through the dropping funnel, keep the reaction temperature at 35 °C, and react for 5.5 h; add 10 g of sodium hydroxide to neutralize to a pH value of 6.6; filter the above reaction system, and dry the filtered solid matter to obtain monomer B1.

[0038] (2) Weigh 1000 kg of deionized water and add it to the reaction kettle. Start the stirrer, add 350 kg of acrylamide, add 55 kg of monomer B1, and stir until completely dissolved; add 3.5 kg of initiator azobisisobutyronitrile; pass nitrogen into the material system for 35 minutes to remove the dissolved oxygen in the water; add 20 g of sodium bisulfate, keep the temperature at 8 h to obtain a polymer colloid; send the above polymer colloid to the hydrolysis reaction kettle for granulation. Add 35 kg of sodium carbonate to the hydrolysis reaction kettle, stir well to mix, heat up to 90 °C, keep the temperature for 3 h, and then dry, grind and screen to obtain the anti-fouling and salt-resistant polymer HLKS-12 for oil production.

[0039] Example 3

[0040] Synthesis of an anti-fouling and salt-resistant polymer for oil production:

[0041] (1) Add 150 g of chloroform to a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. Start the stirrer, add 25 g of dodecylsulfonyl chloride and 29 g of octadecylsulfonyl chloride. After complete dissolution, slowly and evenly drop 36 g of 4-methylisopropenyltoluene into the above reaction system through the dropping funnel, keep the reaction temperature at 40 °C, and react for 8 h; add 13 g of sodium hydroxide to neutralize to a pH value of 7.2; filter the above reaction system, and dry the filtered solid matter to obtain monomer B2.

[0042] (2) Weigh 1000 kg of deionized water and add it to the reaction kettle. Start the stirrer, add 350 kg of acrylamide, add 46 kg of monomer B2, and stir until completely dissolved. Add 0.7 kg of initiator azobisisobutyronitrile. Pass nitrogen gas through the material system for 35 minutes to remove the dissolved oxygen in the water. Add 20 g of sodium bisulfate, keep the temperature at 8 h to obtain a polymer colloid. Feed the above polymer colloid into the hydrolysis reaction kettle, add 112 kg of solid sodium hydroxide in the hydrolysis reaction kettle, stir well to mix, heat up to 90 °C, keep the temperature for 2 h, and then dry, grind, and screen to obtain the anti-fouling and salt-tolerant polymer HLKS-2 for oil production. The reaction equation is as follows:

[0043]

[0044] Example 4

[0045] Synthesis of an anti-fouling and salt-tolerant polymer for oil production:

[0046] (1) Add 150 g of chloroform to a three-necked flask equipped with a stirrer, a dropping funnel, and a thermometer. Start the stirrer, add 25 g of dodecylsulfonyl chloride and 29 g of octadecylsulfonyl chloride. After fully dissolving, slowly and evenly add 36 g of 4-methylisopropenyltoluene to the above reaction system through the dropping funnel, keep the reaction temperature at 40 °C, and react for 8 h. Add 13 g of sodium hydroxide to neutralize to a pH value of 7.2. Filter the above reaction system, and after drying the filtered solid matter, obtain monomer B2;

[0047] (2) Weigh 1000 kg of deionized water and add it to the reaction kettle. Start the stirrer, add 350 kg of acrylamide, add 40 kg of monomer B2, and stir until completely dissolved. Add 0.35 kg of initiator azobisisobutyronitrile. Pass nitrogen gas through the material system for 35 minutes to remove the dissolved oxygen in the water. Add 20 g of sodium bisulfate, keep the temperature at 8 h to obtain a polymer colloid. Feed the above polymer colloid into the hydrolysis reaction kettle, add 112 kg of solid sodium hydroxide in the hydrolysis reaction kettle, stir well to mix, heat up to 90 °C, keep the temperature for 2 h, and then dry, grind, and screen to obtain the anti-fouling and salt-tolerant polymer HLKS-21 for oil production.

[0048] Example 5

[0049] Synthesis of an anti-fouling and salt-tolerant polymer for oil production:

[0050] (1) Add 150 g of chloroform into a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. Start the stirrer, add 25 g of dodecylsulfonyl chloride and 29 g of octadecylsulfonyl chloride. After complete dissolution, slowly and uniformly add 36 g of 4-methylisopropenyltoluene into the above reaction system through the dropping funnel. Keep the reaction temperature at 40 °C and the reaction time at 8 h. Add 13 g of sodium hydroxide to neutralize to a pH value of 7.2. Filter the above reaction system, and after drying the filtered solid, monomer B2 is obtained;

[0051] (2) Measure 1000 kg of deionized water and add it into the reaction kettle. Start the stirrer, add 350 kg of acrylamide and 55 kg of monomer B2, and stir until completely dissolved. Add 1 kg of initiator hydrogen peroxide. Pass nitrogen into the material system for 35 min to remove the dissolved oxygen in the water. Add 20 g of sodium bisulfate and keep the temperature for 8 h to obtain a polymer colloid. Feed the above polymer colloid into the hydrolysis reaction kettle, add 112 kg of solid sodium hydroxide in the hydrolysis reaction kettle, stir and mix well, heat up to 90 °C, keep the temperature for 2 h, and then dry, grind and screen to obtain the anti-fouling and salt-tolerant polymer HLKS-22 for oil recovery.

[0052] Example 6

[0053] (1) Add 160 g of chloroform into a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. Start the stirrer, add 23 g of pentadecylsulfonyl chloride and 25 g of octadecylsulfonyl chloride. After complete dissolution, slowly and uniformly add 39 g of 4-methylisopropenyltoluene into the above reaction system through the dropping funnel. Keep the reaction temperature at 45 °C - 55 °C and the reaction time at 12 h. Add 11.2 g of sodium hydroxide to neutralize to a pH value of 6.9. Filter the above reaction system, and after drying the filtered solid, monomer B3 is obtained;

[0054] (2) Measure 1000 kg of deionized water and add it into the reaction kettle. Start the stirrer, add 350 kg of acrylamide and 44 kg of monomer B3, and stir until completely dissolved. Add 0.7 kg of initiator azobisisobutyronitrile. Pass nitrogen into the material system for 35 min to remove the dissolved oxygen in the water. Add 20 g of sodium bisulfate and keep the temperature for 8 h to obtain a polymer colloid. Feed the above polymer colloid into the hydrolysis reaction kettle, add 112 kg of solid sodium hydroxide in the hydrolysis reaction kettle, stir and mix well, heat up to 90 °C, keep the temperature for 4 h, and then dry, grind and screen to obtain the anti-fouling and salt-tolerant polymer HLKS-3 for oil recovery. The reaction equation is as follows:

[0055]

[0056] Example 7

[0057] (1) Add 160 g of chloroform into a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. Start the stirrer, add 23 g of pentadecylsulfonyl chloride and 25 g of octadecylsulfonyl chloride. After complete dissolution, slowly and uniformly add 39 g of 4-methylisopropenyltoluene into the above reaction system through the dropping funnel. Keep the reaction temperature at 45°C - 55°C and the reaction time for 12 h. Add 11.2 g of sodium hydroxide to neutralize to a pH value of 6.9. Filter the above reaction system, and after drying the filtered solid, monomer B3 is obtained;

[0058] (2) Measure 1000 kg of deionized water and add it into the reaction kettle. Start the stirrer, add 350 kg of acrylamide and 40 kg of monomer B3, and stir until completely dissolved. Add 0.7 kg of initiator potassium persulfate. Pass nitrogen into the material system for 35 min to remove the dissolved oxygen in the water. Add 20 g of sodium bisulfate, keep the temperature for 8 h to obtain a polymer colloid. Feed the above polymer colloid into the hydrolysis reaction kettle. Add 112 kg of sodium carbonate into the hydrolysis reaction kettle, stir well to mix, heat up to 90°C, keep the temperature for 4 h, and then dry, grind and screen to obtain the anti-fouling and salt-tolerant polymer HLKS-31 for oil production.

[0059] Example 8

[0060] (1) Add 160 g of chloroform into a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. Start the stirrer, add 23 g of pentadecylsulfonyl chloride and 25 g of octadecylsulfonyl chloride. After complete dissolution, slowly and uniformly add 39 g of 4-methylisopropenyltoluene into the above reaction system through the dropping funnel. Keep the reaction temperature at 45°C - 55°C and the reaction time for 12 h. Add 11.2 g of sodium hydroxide to neutralize to a pH value of 6.9. Filter the above reaction system, and after drying the filtered solid, monomer B3 is obtained;

[0061] (2) Measure 1000 kg of deionized water and add it into the reaction kettle. Start the stirrer, add 350 kg of acrylamide and 55 kg of monomer B3, and stir until completely dissolved. Add 0.7 kg of initiator azodiisopentanenitrile. Pass nitrogen into the material system for 35 min to remove the dissolved oxygen in the water. Add 20 g of sodium bisulfate, keep the temperature for 8 h to obtain a polymer colloid. Feed the above polymer colloid into the hydrolysis reaction kettle. Add 112 kg of potassium hydroxide into the hydrolysis reaction kettle, stir well to mix, heat up to 90°C, keep the temperature for 4 h, and then dry, grind and screen to obtain the anti-fouling and salt-tolerant polymer HLKS-32 for oil production.

[0062] Performance Effect Test

[0063] 1. Evaluation of Salt Tolerance Performance

[0064] The anti-fouling and salt-tolerant polymers HLKS-1, HLKS-2, HLKS-3 for oil production and the commercially available polymer LHG-1 for oil production (a super-high molecular weight polyacrylamide product of Daqing Refining and Chemical Company, with a molecular weight of 26.5 million) were formulated into polymer brine solutions with a polymer concentration of 1000 mg / L using brine with a salinity of 33000 mg / L. The apparent viscosity of the above polymer brine solutions was measured using an American Brookfield DV-II viscometer, with a 0# rotor, at a rotational speed of 6 rpm and a temperature of 85°C. The results are shown in Table 1.

[0065] Table 1 Data Sheet for Viscosity Detection of Polymer Brine Solutions (Salinity 33000 mg / L)

[0066] Sample Number <![CDATA[Viscosity-average molecular weight, ×10 6 > Viscosity (mPa·s) HLKS-1 1415 30.9 HLKS-11 1187 37.8 HLKS-12 1668 26.2 HLKS-2 1230 33.1 HLKS-21 1056 36.8 HLKS-22 1388 32.5 HLKS-3 1070 35.3 HLKS-31 988 36.5 HLKS-32 1353 32.8 LHG-1 2650 8.2

[0067] Take the anti-fouling and salt-tolerant polymer HLKS-1 for oil production and formulate polymer brine solutions with polymer concentrations of 1000 mg / L, 1250 mg / L, 1500 mg / L, 1750 mg / L, 2000 mg / L, 2250 mg / L, 2500 mg / L, 2750 mg / L, and 3000 mg / L respectively using brine with a salinity of 33000 mg / L. Use an American Brookfield viscometer to measure the apparent viscosity of the above polymer brine solutions at a temperature of 85°C. The test results are shown in Table 2.

[0068] Table 2 Data Sheet for Viscosity-Concentration Detection of Anti-fouling and Salt-tolerant Polymer HLKS-1 for Oil Production

[0069] Concentration (ppm) Viscosity (mPa·s) 1000 30.9 1250 48 1500 76.8 1750 133.3 2000 188.8 2250 248.5 2500 338.1 2750 407.5 3000 509.9

[0070] Take the anti-fouling and salt-tolerant polymer HLKS-2 for oil production and formulate polymer brine solutions with polymer concentrations of 1000 mg / L, 1250 mg / L, 1500 mg / L, 1750 mg / L, 2000 mg / L, 2250 mg / L, 2500 mg / L, 2750 mg / L, and 3000 mg / L respectively using brine with a salinity of 33000 mg / L. Use an American Brookfield viscometer to measure the apparent viscosity of the above polymer brine solutions at a temperature of 85°C. The test results are shown in Table 3.

[0071] Table 3 Data Sheet for Viscosity-Concentration Detection of Anti-fouling and Salt-tolerant Polymer HLKS-2 for Oil Production

[0072]

[0073]

[0074] Take the anti-fouling and salt-tolerant polymer HLKS-3 for oil production, and prepare polymer brine solutions with polymer concentrations of 1000 mg / L, 1250 mg / L, 1500 mg / L, 1750 mg / L, 2000 mg / L, 2250 mg / L, 2500 mg / L, 2750 mg / L, and 3000 mg / L respectively using brine with a salinity of 33000 mg / L. Use an American Brookfield viscometer to measure the apparent viscosity of the above polymer brine solutions at a temperature of 85°C, and the test results are shown in Table 4.

[0075] Table 4 Viscosity-Concentration Detection Data Table of Anti-fouling and Salt-tolerant Polymer HLKS-3 for Oil Production

[0076] Concentration (ppm) Viscosity (mPa·s) 1000 35.3 1250 55.1 1500 84.7 1750 145.8 2000 195.4 2250 257.1 2500 348.2 2750 417.4 3000 525.1

[0077] A salt resistance comparison test was carried out on the anti-fouling and salt-tolerant polymers HLKS-1, HLKS-2, and HLKS-3 and the commercially available oil production polymer LHG-1 (a super-high molecular weight polyacrylamide product from Daqing Refining and Chemical Company, with a molecular weight of 26.5 million). The ordinary polymer is a conventional polyacrylamide with a molecular weight of 16 million, the polymer concentration is 1000 ppm, the detection temperature is 45°C, the detection instrument is a Brookfield viscometer, and the viscosity of the aqueous solution under different concentrations of sodium chloride is shown in Table 5 below.

[0078] Table 5 Viscosity under Different Concentrations of Sodium Chloride

[0079]

[0080]

[0081] As can be seen from Table 1 and Table 2, the anti-fouling and salt-tolerant polymers HLKS-1, HLKS-2, and HLKS-3 for oil production provided by the present invention exhibit excellent anti-fouling, salt-tolerant, and salt resistance properties in brine with a temperature of 85°C and a salinity of 33000 mg / L (under the same conditions, compared with the oil production polymer LHG-1). The apparent viscosity of the polymer brine solution is relatively low, indicating that the anti-fouling, salt-tolerant, and salt resistance properties of the anti-fouling and salt-tolerant polymers for oil production provided by the present invention are significantly superior to those of commercially available ordinary polyacrylamide products, and no similar oil production polymer products meeting the above indicators have been found in China.

[0082] Ordinary polyacrylamide is dissolved in a saline solution. Since the salt ions have a repulsive effect on the ionic groups on the polymer molecular chain, increasing the salt ion concentration causes the polymer molecular chain to be further compressed and curled, resulting in a significant reduction in the hydrodynamic volume and a substantial decrease in viscosity macroscopically. Due to the fact that the molecular chain of the anti-fouling and salt-tolerant polymer for oil recovery in the present invention contains functional groups such as long-chain groups, benzene rings, and sulfonic acid groups, it greatly increases the hydrated molecular radius of the polymer, enhances the rigidity of the polymer molecule and the ability to resist salt ion compression, making the polymer molecular chain not easily curled in high-concentration brine or sewage, and its viscosity value is much higher than that of ordinary polymer products after the salt concentration increases.

[0083] In the study of the salt tolerance of polymers, introducing rigid monomers often leads to a decrease in the water solubility of the polymer. Therefore, it is difficult to obtain a polymer with both improved water solubility and salt tolerance, or at least maintaining good water solubility while improving salt tolerance. The anti-fouling and salt-tolerant polymer for oil recovery provided by the present invention preferably solves this contradiction between water solubility and salt tolerance. By introducing functional groups such as long-chain alkyl groups, sulfonate groups, and benzene rings into the main molecular chain of polyacrylamide, and reasonably controlling the proportion of each group in the molecular chain, on the basis of ensuring molecular linearity, the polymer molecular radius is greatly increased, the rigidity of the polymer molecular chain is enhanced, and on the premise of ensuring good water solubility of the polymer, the viscosity stability, anti-fouling and salt-tolerant properties, and oil displacement performance of the polymer are improved.

[0084] 2. Evaluation of the oil displacement effect of the anti-fouling and salt-tolerant polymer for oil recovery:

[0085] A Berea core (30×4.5×4.5; water permeability is 100 mD) was used to carry out an oil displacement experiment to study the oil displacement effect of the anti-fouling and salt-tolerant polymer for oil recovery in the injection slug. Polymer aqueous solutions with a concentration of 1150 mg / L (viscosity of 40 mPa·s) were prepared using the anti-fouling and salt-tolerant polymers for oil recovery HLKS-1, HLKS-2, and HLKS-3, and a polymer aqueous solution with a concentration of 1150 mg / L (viscosity of 40 mPa·s) was prepared using the comparative sample polymer for oil recovery LHG-1 (Daqing Refining and Chemical Company, partially hydrolyzed polyacrylamide, molecular weight 26.5 million). Water was injected into the core at a rate of 0.35 mL / min, and water flooding ended when the water cut was above 98%; after injecting 0.5 PV at the same injection rate, subsequent water was injected, and the experiment ended when the produced liquid water cut was greater than 98%. The results of the oil displacement experiment are shown in Table 3.

[0086] Table 6 Statistical table of the results of the oil displacement experiment

[0087]

[0088]

[0089] As can be seen from Table 6, the total recovery rate of the anti-fouling and salt-tolerant polymer HLKS-1 for oil production is 5.04 percentage points higher than that of the polymer LHG-1 for oil production (Daqing Refining and Chemical Company, partially hydrolyzed polyacrylamide, molecular weight of 26.5 million), indicating that the anti-fouling and salt-tolerant polymer for oil production of the present invention can further improve the recovery rate compared with ordinary polymers. The anti-fouling and salt-tolerant polymer for oil production provided by the present invention has excellent viscosity-increasing, anti-fouling and salt-tolerant, and salt-resisting properties. The anti-fouling and salt-tolerant polymer for oil production provided by the present invention has a relatively high oil displacement recovery rate.

[0090] 3. Viscosity Stability

[0091] The polymer was prepared and diluted with the on-site sewage of an oil production plant in Daqing into a 1000 mg / L solution, and the viscosity after standing for 0 d, 3 d, 15 d, 30 d, 60 d, and 90 d at 45 °C under anaerobic conditions was detected with a Brookfield viscometer. The ordinary polymer was LHG-1. The detection results are shown in Table 7 below:

[0092] Table 7 Viscosity after Standing for Different Times

[0093]

[0094]

[0095] As can be seen from the data in the table, for the anti-fouling and salt-tolerant polymer for oil production of the present invention, after standing for 90 days at 45 °C under anaerobic conditions, the average viscosity retention rate exceeds 110%, while that of the ordinary polymer is 0, indicating that the present invention can resist sewage and has excellent stability.

[0096] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0097] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A pollution-resistant and salt-resistant polymer for oil production, prepared by polymerization and hydrolysis of aqueous materials including monomer A and monomer B, characterized in that: The monomer A is a monomer having a structure shown in formula (a), and the monomer B is a monomer having a structure shown in formula (b), which are represented as follows: wherein R1, R2 and R3 are each independently selected from -H or C1-C4 alkyl; R4, R5 and R6 are each independently selected from -H or C1-C4 alkyl; X is selected from H + , K + 、Na + or NH4 + ; m is an integer of 3-15; n is an integer of 5-17; R7 is selected from a C1-C2 alkyl group.

2. The anti-fouling and salt-resistant polymer for oil production according to claim 1, characterized in that: The viscosity average molecular weight of the polymer is 1 million to 20 million.

3. The anti-fouling and salt-resistant polymer for oil production according to claim 1, characterized in that: The polymer salt water solution with a concentration of 1000 mg / L-3000 mg / L is prepared by using salt water with a salinity of 33000 mg / L, and the apparent viscosity at 85° C. is 30-550 mPa·s.

4. A method for synthesizing an anti-fouling and salt-tolerant polymer for oil production, characterized in that: The following steps are involved: (1) Preparation of monomer solution The monomer solution comprises monomer A, monomer B and deionized water, wherein the mass ratio of monomer A to monomer B is 300-400:40-55; the total mass of monomer A and monomer B accounts for 30-45% of the deionized water; (2) passing nitrogen gas into the monomer solution obtained in step (1) to deoxygenate, and performing a polymerization reaction in the presence of an initiator to obtain a polymer colloid; (3) adding alkali to the polymer colloid obtained in step (2), raising the temperature to 70-99° C., and keeping the temperature for 2-8 hours to carry out a hydrolysis reaction to obtain an anti-fouling and salt-resistant polymer for oil recovery.

5. The method for synthesizing a pollution-resistant and salt-resistant polymer for oil production according to claim 4, characterized in that: The initiator in step (2) includes sulfate initiator, phosphate initiator, peroxide initiator and azo initiator, and the mass ratio of the initiator to monomer A is 1:(10-1000).

6. The method for synthesizing a pollution-resistant and salt-resistant polymer for oil production according to claim 4, characterized in that: The azo initiator may be selected from at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptylnitrile, azoisobutylcyanoformamide, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride and azobisisopropylimidazoline hydrochloride.

7. The method for synthesizing a pollution-resistant and salt-resistant polymer for oil production according to claim 4, characterized in that: The peroxide initiator may be selected from at least one of sodium persulfate, ammonium persulfate, potassium persulfate, hydrogen peroxide and benzoyl peroxide.

8. The method for synthesizing a pollution-resistant and salt-resistant polymer for oil production according to claim 4, characterized in that: The polymerization reaction temperature in step (2) is -5°C-50°C, the pH value is 3-11, and the reaction time is 1-24h.

9. The method for synthesizing a pollution-resistant and salt-resistant polymer for oil production according to claim 4, characterized in that: The alkali in step (3) includes at least one of sodium hydroxide, potassium hydroxide and sodium carbonate.

10. The method for synthesizing a pollution-resistant and salt-resistant polymer for oil production according to claim 4, characterized in that: The mass ratio of the base to monomer A in step (3) is 1:(3-20).

Images