Anionic polyacrylamide for oil recovery and a method for preparing the same

Abstract

The application belongs to the technical field of tertiary oil recovery, and particularly relates to an anionic polyacrylamide for oil recovery and a preparation method thereof. The preparation method is as follows: nitrogen is introduced into a reaction kettle, acrylamide, 2-(trifluoromethyl) acrylic acid, 3-methyl acryloyloxy-2-hydroxypropyl sodium sulfonate, 1-vinyl-2-pyrrolidone, allyl alcohol polyoxyethylene ether, sodium dodecyl sulfate, buffer salt and deionized water are sequentially added into the reaction kettle, and stirring is uniformly performed; pH is adjusted to 8-8.5; an initiator is added into a high-position dropping groove; during the dropping process, the solution is automatically heated; when the temperature no longer continues to rise, heating is performed to 70-75 DEG C, and the temperature is kept for 50-60 min; the temperature is reduced to below 40 DEG C; the reaction product is granulated to obtain the product anionic polyacrylamide. The application has the advantages of simple synthesis process and no by-product; and has the characteristics of high viscosity, high interfacial activity and shear resistance.

Description

Technical Field

[0001] This invention belongs to the field of tertiary oil recovery technology, specifically relating to an anionic polyacrylamide for oil recovery and its preparation method. Background Technology

[0002] With rapid economic development, the world's demand for energy, especially oil, is constantly increasing. Therefore, improving oil recovery rates has become an important part of the business planning of international oil companies. In recent years, my country's sustained and rapid economic growth has led to a growing demand for crude oil, while domestic oil supply has struggled to meet this increasing demand.

[0003] As a non-renewable energy source, oil reserves underground are extremely limited. Under current waterflooding conditions, oil recovery rates are only 35-45%, meaning that a large portion of crude oil remains underground after waterflooding is completed. Maximizing the extraction of this remaining underground crude oil has become a crucial task for the oil industry.

[0004] To improve oil recovery, polymer flooding and ternary composite flooding technologies are currently being promoted. These technologies involve injecting an aqueous solution of polyacrylamide to improve the oil-water flow ratio, thereby increasing the crude oil content in the produced material.

[0005] In oil extraction, polyacrylamide is mainly used in drilling mud materials and to improve oil recovery. It is widely used in oilfield operations such as drilling, well completion, cementing, fracturing, and enhanced oil recovery, and has functions such as thickening, reducing filtration loss, rheological regulation, gelling, diversion, and profile adjustment.

[0006] PAM is a linear water-soluble polymer and one of the most widely used water-soluble polymers. In water, it readily forms hydrogen bonds with water, is easily soluble in water, and has a large hydrodynamic volume after hydration. Due to the electrostatic repulsion of the sodium carboxylate groups within the polyacrylamide molecule, the polyacrylamide molecule is in an extended state, resulting in strong thickening ability.

[0007] CN104448129B discloses a high-temperature resistant hydrolytic copolymer for oilfields, its preparation method, and its application in oil production. It primarily addresses the problem of poor hydrolytic stability of polyacrylamide under high-temperature and high-salinity conditions present in previous technologies. However, this invention lacks surfactant units in its molecular structure and can only function as a polymer-driven oil recovery agent. Its improved oil recovery principle relies on increasing the oil displacement profile and expanding the swept volume; it does not possess the function of surfactant-driven oil recovery.

[0008] CN105542073B discloses a method for preparing polyacrylamide for polymer flooding oil recovery, belonging to the field of polymer technology. The steps are as follows: cationic monomers, acrylamide, trimethylolpropionamide, surfactants, and water are mixed evenly, and nitrogen gas is introduced into the mixture; an initiator is added, the temperature is raised, the reaction is maintained, the temperature is lowered, hydroxyethyl acrylate and dimethylchlorosilane are added to the mixture, the pH of the reaction system is adjusted, the temperature is raised, the reaction is maintained, and after completion, the resulting gel-like product is taken out, cut, dried, granulated, and sieved to obtain the polyacrylamide product. This invention, by adjusting the monomer reaction sequence during the polymerization of modified polyacrylamide, first allows the cationic monomer to partially polymerize with acrylamide, and then the hydroxyethyl acrylate and dimethylchlorosilane continue the polymerization reaction, enabling the prepared modified polyacrylamide to have a viscosity-increasing effect in solutions with high ion concentrations. However, this product is a cationic polyacrylamide, which is prone to flocculation and precipitation in some clay-rich formations, clogging the formation, posing certain risks in field application. Summary of the Invention

[0009] This invention addresses the shortcomings of existing technologies by providing anionic polyacrylamide for oil production and its preparation method. This invention offers advantages such as a simple synthesis process and the absence of byproducts; it also features high viscosity, high interfacial activity, and shear resistance.

[0010] To achieve the above objectives, one objective of this invention discloses an anionic polyacrylamide for oil extraction, wherein the molecular structural formula of the anionic polyacrylamide is as follows:

[0011]

[0012] in:

[0013] o = 50000 - 500000;

[0014] a = 5000 - 100000;

[0015] b = 5000 - 100000;

[0016] c = 1000 - 20000;

[0017] d = 2000 - 40000;

[0018] n = 4 - 20.

[0019] The anionic polyacrylamide has a viscosity-average molecular weight of 30,000,000-40,000,000.

[0020] Another objective of this invention is to disclose a method for preparing the above-mentioned anionic polyacrylamide, the specific steps of which are as follows:

[0021] (1) Purge the reactor with nitrogen to remove the air. Add acrylamide, 2-(trifluoromethyl)acrylic acid, sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 1-vinyl-2-pyrrolidone, allyl alcohol polyoxyethylene ether, sodium dodecyl sulfate, buffer salt, and deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 200-300 rpm. Adjust the pH to 8-8.5 with 4-6 wt% sodium hydroxide solution.

[0022] (2) Add the initiator to the high-level dropping tank and slowly drop it into the reactor. The dropping time is controlled at 30-60 min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 70-75℃, keep it at the temperature for 50-60 min, and then cool it down to below 40℃.

[0023] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide products with a particle diameter of 0.7-2.0 mm.

[0024] In this invention, preferably, based on 1 mole of acrylamide, the amounts of 2-(trifluoromethyl)acrylic acid, sodium 3-methacryloyloxy-2-hydroxypropylsulfonate, 1-vinyl-2-pyrrolidone, and allyl alcohol polyoxyethylene ether are 0.05-0.2 moles, 0.05-0.2 moles, 0.01-0.05 moles, and 0.02-0.1 moles, respectively.

[0025] In a preferred embodiment, in step (1), the ventilation rate is 10-15 L / min and the ventilation time is 20-30 min.

[0026] In a preferred embodiment, in step (1), the buffer salt is one of ammonium acetate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate.

[0027] In a preferred embodiment, in step (1), the weight ratio of sodium dodecyl sulfate, buffer salt, deionized water and acrylamide is 0.005-0.01:0.005-0.05:6-10:1.

[0028] In this invention, preferably, in step (2), the initiator is one of the following: 8-10 wt% potassium persulfate + 4-6 wt% sodium sulfite mixed aqueous solution, 8-10 wt% sodium persulfate + 4-6 wt% sodium sulfite mixed aqueous solution, 8-10 wt% ammonium persulfate + 4-6 wt% sodium sulfite mixed aqueous solution, 8-12 wt% azobisisobutyronitrile ethanol solution, and 8-12 wt% azobisisobutyronitrile ethanol solution; the weight ratio of the initiator to acrylamide is 0.02-0.1:1.

[0029] The reaction equation for the synthesis of anionic polyacrylamide according to the present invention is as follows:

[0030]

[0031] The anionic polyacrylamide of this invention is a five-component polymer with acrylamide, 2-(trifluoromethyl)acrylic acid, sodium 3-methacryloyloxy-2-hydroxypropylsulfonate, 1-vinyl-2-pyrrolidone, and allyl alcohol polyoxyethylene ether as monomers. It is a structural modification of polyacrylamide to improve its oil displacement performance. 2-(trifluoromethyl)acrylic acid contains two functional groups. The trifluoromethyl group has a lower interfacial tension than conventional surfactants, allowing for better binding to crude oil. The carboxyl group is a hydrophilic anion, which can reduce interfacial tension and increase molecular viscosity. Sodium 3-methacryloyloxy-2-hydroxypropylsulfonate has strong shear resistance, and the sulfonic acid group has strong temperature and salt resistance, and is a commonly used anionic oil displacement surfactant. 1-Vinyl-2-pyrrolidone has strong rigidity, which can significantly improve the product's shear resistance. Allyl alcohol polyoxyethylene ether is a linear nonionic surfactant with a good effect on reducing interfacial tension, which can sweep away residual crude oil in the formation. Sodium dodecyl sulfate is also a conventional oil displacement surfactant, which can also improve the oil displacement effect by reducing interfacial tension. In summary, the anionic polyacrylamide of this invention reduces interfacial tension, has surfactant function, increases viscosity, improves oil displacement effect, improves temperature and salt resistance, and increases shear resistance.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] (1) The synthesis method of the present invention is a one-pot method, the raw materials are widely available, the synthesis process is simple, there are no by-products, and there is no environmental pollution.

[0034] (2) The anionic polyacrylamide of the present invention has good interfacial activity, and the interfacial tension at a concentration of 200 mg / L is less than 10. -2 mN / m;

[0035] (3) The anionic polyacrylamide of the present invention has a high surface viscosity, with a surface viscosity of more than 145 mPa·s at a concentration of 2000 mg / L;

[0036] (4) The anionic polyacrylamide of the present invention has shear resistance and retains a viscosity of more than 90% after 2 hours of shearing. Detailed Implementation

[0037] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0038] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0039] Example 1

[0040] (1) Purge the reactor with nitrogen gas to remove the air. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 1 mol 2-(trifluoromethyl)acrylic acid, 0.25 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.05 mol 1-vinyl-2-pyrrolidone, 0.1 mol allyl alcohol polyoxyethylene ether, 1.78 g sodium dodecyl sulfate, 1.78 g ammonium acetate, and 2130 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 200 rpm. Adjust the pH to 8-8.5 with 4 wt% sodium hydroxide solution.

[0041] (2) Add the initiator to the high-level dropping tank. The initiator is a mixed aqueous solution of 10wt% potassium persulfate and 4wt% sodium sulfite. The mass of the initiator is 7.1g. Slowly add it to the reaction vessel. The dropping time of the initiator is controlled at 30min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 70℃, keep it at the temperature for 60min, and then cool it down to below 40℃.

[0042] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P1 with a particle diameter of 0.7-2.0 mm.

[0043] Example 2

[0044] (1) Purge the reactor with nitrogen gas to remove the air. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.85 mol 2-(trifluoromethyl)acrylic acid, 0.33 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.08 mol 1-vinyl-2-pyrrolidone, 0.28 mol allyl alcohol polyoxyethylene ether, 2.14 g sodium dodecyl sulfate, 3.55 g sodium dihydrogen phosphate, and 2788 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 300 rpm. Adjust the pH to 8-8.5 with 5 wt% sodium hydroxide solution.

[0045] (2) Add the initiator to the high-level dropping tank. The initiator is a mixed aqueous solution of 8wt% potassium persulfate and 6wt% sodium sulfite. The mass of the initiator is 10.3g. Add it slowly to the reaction vessel. The dropping time of the initiator is controlled at 60min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 75℃, keep it at the temperature for 50min, and then cool it down to below 40℃.

[0046] (3) The reaction product in (3) is granulated to obtain anionic polyacrylamide product P2 with a particle diameter of 0.7-2.0 mm.

[0047] Example 3

[0048] (1) Purge the reactor with nitrogen gas to remove the air from the reactor. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.76 mol 2-(trifluoromethyl)acrylic acid, 0.45 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.11 mol 1-vinyl-2-pyrrolidone, 0.31 mol allyl alcohol polyoxyethylene ether, 3.55 g sodium dodecyl sulfate, 5.5 g potassium dihydrogen phosphate, and 2247 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 250 rpm. Adjust the pH to 8-8.5 with 4 wt% sodium hydroxide solution.

[0049] (2) Add the initiator to the high-level dropping tank. The initiator is a mixed aqueous solution of 8wt% sodium persulfate and 4wt% sodium sulfite. The mass of the initiator is 18.6g. Add it slowly to the reaction vessel. The dropping time of the initiator is controlled at 40min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 72℃, keep it at the temperature for 50min, and then cool it down to below 40℃.

[0050] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P3 with a particle diameter of 0.7-2.0 mm.

[0051] Example 4

[0052] (1) Purge the reactor with nitrogen gas to remove the air. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.71 mol 2-(trifluoromethyl)acrylic acid, 0.48 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.25 mol 1-vinyl-2-pyrrolidone, 0.49 mol allyl alcohol polyoxyethylene ether, 3.21 g sodium dodecyl sulfate, 7.9 g ammonium dihydrogen phosphate, and 2563 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 200 rpm. Adjust the pH to 8-8.5 with 6 wt% sodium hydroxide solution.

[0053] (2) Add the initiator to the high-level dropping tank. The initiator is a mixed aqueous solution of 10wt% sodium persulfate and 6wt% sodium sulfite. The mass of the initiator is 27.4g. Slowly add it to the reaction vessel. The initiator dropping time is controlled at 50min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 73℃, keep it at the temperature for 60min, and then cool it down to below 40℃.

[0054] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P4 with a particle diameter of 0.7-2.0 mm.

[0055] Example 5

[0056] (1) Purge the reactor with nitrogen gas to remove the air. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.25 mol 2-(trifluoromethyl)acrylic acid, 0.86 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.14 mol 1-vinyl-2-pyrrolidone, 0.5 mol allyl alcohol polyoxyethylene ether, 1.98 g sodium dodecyl sulfate, 14.2 g disodium hydrogen phosphate, and 3000 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 300 rpm. Adjust the pH to 8-8.5 with 6 wt% sodium hydroxide solution.

[0057] (2) Add the initiator to the high-level dropping tank. The initiator is a mixed aqueous solution of 10wt% ammonium persulfate and 4wt% sodium sulfite. The mass of the initiator is 35.5g. Add it slowly to the reaction vessel. The dropping time of the initiator is controlled at 50min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 74℃, keep it at the temperature for 55min, and then cool it down to below 40℃.

[0058] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P5 with a particle diameter of 0.7-2.0 mm.

[0059] Example 6

[0060] (1) Purge the reactor with nitrogen gas to remove the air from the reactor. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.37 mol 2-(trifluoromethyl)acrylic acid, 0.72 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.18 mol 1-vinyl-2-pyrrolidone, 0.48 mol allyl alcohol polyoxyethylene ether, 1.72 g sodium dodecyl sulfate, 11.6 g dipotassium hydrogen phosphate, and 3306 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 220 rpm. Adjust the pH to 8-8.5 with 5 wt% sodium hydroxide solution.

[0061] (2) Add the initiator to the high-level dropping tank. The initiator is a mixed aqueous solution of 8wt% ammonium persulfate and 6wt% sodium sulfite. The mass of the initiator is 10.8g. Add it slowly to the reaction vessel. The dropping time of the initiator is controlled at 40min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 71℃, keep it at the temperature for 55min, and then cool it down to below 40℃.

[0062] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P6 with a particle diameter of 0.7-2.0 mm.

[0063] Example 7

[0064] (1) Purge the reactor with nitrogen gas to remove the air from the reactor. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.48 mol 2-(trifluoromethyl)acrylic acid, 0.79 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.22 mol 1-vinyl-2-pyrrolidone, 0.42 mol allyl alcohol polyoxyethylene ether, 2.33 g sodium dodecyl sulfate, 10.2 g ammonium acetate, and 3278 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 260 rpm. Adjust the pH to 8-8.5 with 5 wt% sodium hydroxide solution.

[0065] (2) Add the initiator to the high-level dropping tank. The initiator is a 12wt% azobisisobutyronitrile ethanol solution with a mass of 21.4g. Slowly drop it into the reactor. The dropping time of the initiator is controlled at 60min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 72℃, keep it at the temperature for 50min, and then cool it down to below 40℃.

[0066] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P7 with a particle diameter of 0.7-2.0 mm.

[0067] Example 8

[0068] (1) Purge the reactor with nitrogen gas to remove the air from the reactor. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.59 mol 2-(trifluoromethyl)acrylic acid, 0.92 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.16 mol 1-vinyl-2-pyrrolidone, 0.33 mol allyl alcohol polyoxyethylene ether, 2.14 g sodium dodecyl sulfate, 8.8 g diammonium hydrogen phosphate, and 3476 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 280 rpm. Adjust the pH to 8-8.5 with 6 wt% sodium hydroxide solution.

[0069] (2) Add the initiator to the high-level dropping tank. The initiator is an 8wt% azobisisobutyronitrile ethanol solution with a mass of 25.6g. Slowly add it to the reaction vessel. The initiator dropping time is controlled at 50min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 70℃, keep it at the temperature for 60min, and then cool it down to below 40℃.

[0070] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P8 with a particle diameter of 0.7-2.0 mm.

[0071] Example 9

[0072] (1) Purge the reactor with nitrogen gas to remove the air from the reactor. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.66 mol 2-(trifluoromethyl)acrylic acid, 0.9 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.2 mol 1-vinyl-2-pyrrolidone, 0.45 mol allyl alcohol polyoxyethylene ether, 2.22 g sodium dodecyl sulfate, 14.4 g diammonium hydrogen phosphate, and 3324 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 210 rpm. Adjust the pH to 8-8.5 with 4 wt% sodium hydroxide solution.

[0073] (2) Add the initiator to the high-level dropping tank. The initiator is an 8wt% azobisisobutyronitrile ethanol solution with a mass of 20.7g. Slowly drop it into the reaction vessel. The dropping time of the initiator is controlled at 40min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 75℃, keep it at the temperature for 50min, and then cool it down to below 40℃.

[0074] (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide product P9 with a particle diameter of 0.7-2.0 mm.

[0075] Example 10

[0076] (1) Purge the reactor with nitrogen gas to remove the air. The purging rate is 10-15 L / min and the purging time is 20-30 min. Add 5 mol acrylamide, 0.7 mol 2-(trifluoromethyl)acrylic acid, 1 mol sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 0.21 mol 1-vinyl-2-pyrrolidone, 0.5 mol allyl alcohol polyoxyethylene ether, 2.16 g sodium dodecyl sulfate, 17.75 g dipotassium hydrogen phosphate, and 3550 g deionized water to the reactor in sequence. Stir until homogeneous at a stirring speed of 270 rpm. Adjust the pH to 8-8.5 with 5 wt% sodium hydroxide solution.

[0077] (2) Add the initiator to the high-level dropping tank. The initiator is a 12wt% azobisisobutyronitrile ethanol solution with a mass of 35.5g. Slowly add it to the reaction vessel. The initiator dropping time is controlled at 45min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 72℃, keep it at the temperature for 60min, and then cool it down to below 40℃.

[0078] (3) Granulate the reaction product from (2) to obtain anionic polyacrylamide product P with a particle diameter of 0.7-2.0 mm. 10 .

[0079] Example 11: Testing of Surface Tension and Interfacial Tension

[0080] The present invention was prepared into a 200 mg / L solution using tap water. Surface tension was determined using the ring pull method in SY / T5370-2018 "Methods for Determination of Surface and Interfacial Tension", and interfacial tension was tested using the pendant drop method. PAM for oil displacement from Henan Puyang Haizhiyuan Chemical Industry Co., Ltd. was used as a control sample. The test results are shown in Table 1.

[0081] As can be seen from Table 1:

[0082] (1) The anionic polyacrylamide P1-P of the present invention 10 The surface tension of all of them is less than 30 mN / m, of which P 10 The lowest surface tension reached 26.5 mN / m; while the surface tension of the comparative sample was 45.2 mN / m, which was significantly higher than that of the present invention;

[0083] (2) The anionic polyacrylamide P1-P of the present invention 10 The interfacial tensions are all less than 1.0 × 10⁻⁶. -2 mN / m, where P 10 The lowest surface tension reached 0.0072 mN / m; while the surface tension of the comparison sample was 7.5 mN / m, which is significantly higher than that of the present invention.

[0084] Example 12 Apparent viscosity test

[0085] The present invention was prepared into a 2000 mg / L solution using tap water, and its apparent viscosity was measured using a Hacker rheometer at 50°C. A PAM solution for oil displacement from Henan Puyang Haizhiyuan Chemical Industry Co., Ltd. was used as a control sample. The test results are shown in Table 1.

[0086] As can be seen from Table 1:

[0087] The anionic polyacrylamide P1-P of the present invention 10 The apparent viscosity of all samples was greater than 145 mPa·s, with P6 reaching a maximum of 178 mPa·s; while the apparent viscosity of the comparative sample was 76 mPa·s, which was significantly lower than that of the present invention.

[0088] Example 13 Shear resistance test

[0089] The sample from Example 12 was subjected to 50°C for 170 seconds. - Under the condition of continuous shearing for 2 hours, the apparent viscosity was tested, and the viscosity retention rate was calculated. PAM for oil displacement from Henan Puyang Haizhiyuan Chemical Industry Co., Ltd. was used as a control sample. The test results are shown in Table 1.

[0090] Table 1. Test results of surface tension, interfacial tension, apparent viscosity, and shear resistance.

[0091]

[0092] Table 1 shows that at 50℃ and 170 seconds... - Under the condition of continuous shearing for 2 hours, the anionic polyacrylamide P1-P of the present invention... 10 The viscosity retention rate of the samples was greater than 90%, with P9 reaching a maximum of 97.1%; while the viscosity retention rate of the comparative samples was 81.6%, which was significantly lower than that of the present invention.

[0093] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0094] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing anionic polyacrylamide for oil extraction, characterized in that, The specific steps of the preparation method are as follows: (1) Purge the reactor with nitrogen to purge the air. Add acrylamide, 2-(trifluoromethyl)acrylic acid, sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 1-vinyl-2-pyrrolidone, allyl alcohol polyoxyethylene ether, sodium dodecyl sulfate, buffer salt, and deionized water sequentially to the reactor. Stir until homogeneous at 200-300 rpm. Adjust the pH to 8-8.5 with a 4-6 wt% sodium hydroxide solution. Based on 1 mole of acrylamide, the... The amounts of 2-(trifluoromethyl)acrylic acid, sodium 3-methacryloyloxy-2-hydroxypropyl sulfonate, 1-vinyl-2-pyrrolidone, and allyl alcohol polyoxyethylene ether are 0.05-0.2 moles, 0.05-0.2 moles, 0.01-0.05 moles, and 0.02-0.1 moles, respectively; the weight ratio of sodium dodecyl sulfate, buffer salt, deionized water, and acrylamide is 0.005-0.01:0.005-0.05:6-10:

1. (2) Add the initiator to the high-level dropping tank and slowly drop it into the reactor. The dropping time is controlled at 30-60 min. During the dropping process, the solution automatically heats up. When the temperature no longer continues to rise, heat it to 70-75℃, keep it at the temperature for 50-60 min, and then cool it down to below 40℃. (3) Granulate the reaction product in (2) to obtain anionic polyacrylamide products with a particle diameter of 0.7-2.0 mm.

2. The method for preparing anionic polyacrylamide for oil extraction according to claim 1, characterized in that, In step (1), the nitrogen gas is introduced at a rate of 10-15 L / min and the gas introduction time is 20-30 min.

3. The method for preparing anionic polyacrylamide for oil extraction according to claim 1, characterized in that, In step (1), the buffer salt is one of ammonium acetate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate.

4. The method for preparing anionic polyacrylamide for oil extraction according to claim 1, characterized in that, In step (2), the initiator is one of the following: 8-10wt% potassium persulfate + 4-6wt% sodium sulfite mixed aqueous solution, 8-10wt% sodium persulfate + 4-6wt% sodium sulfite mixed aqueous solution, 8-10wt% ammonium persulfate + 4-6wt% sodium sulfite mixed aqueous solution, 8-12wt% azobisisobutyronitrile ethanol solution, and 8-12wt% azobisisoheptanenitrile ethanol solution.

5. The method for preparing anionic polyacrylamide for oil extraction according to claim 4, characterized in that, The weight ratio of the initiator to acrylamide is 0.02-0.1:

1.

6. The anionic polyacrylamide prepared by the preparation method according to claim 1, characterized in that, The molecular structure of the anionic polyacrylamide is as follows: in: o=50000-500000； a=5000-100000； b=5000-100000； c=1000-20000； d=2000-40000； n=4-20。 7. The anionic polyacrylamide according to claim 6, characterized in that, The anionic polyacrylamide has a viscosity-average molecular weight of 30,000,000-40,000,000.

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