Water shutoff agent for oil field as well as preparation method and application of water shutoff agent

Abstract

The invention belongs to the technical field of tertiary oil recovery, and particularly relates to a water shutoff agent for an oil field and a preparation method and application thereof. The preparation method comprises the following steps: sequentially adding N-acryloyl (trihydroxymethyl) aminomethane, sodium p-styrenesulfonate, allylmalonic acid, N-(3-(triethoxysilyl) propyl) methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1, 6-diene-4-alcohol, OP-10, a dispersing agent, buffer salt and deionized water into a reactor, stirring, and adjusting the pH value to be 7-8; adding an initiator into the elevated tank, slowly dropwise adding the initiator into the reactor, after dropwise adding, heating to 40-45 DEG C, continuously stirring, continuously heating to 70-75 DEG C, continuously stirring for 2-3 hours, cooling to 40 DEG C or below, and adjusting the pH value to 7-8 to obtain a viscous liquid; and drying and granulating to obtain the water shutoff agent product. The water shutoff agent disclosed by the invention has the characteristics of high viscosity, strong shear resistance and high breakthrough pressure.

Description

Technical Field

[0001] The invention belongs to the technical field of tertiary oil recovery, and in particular relates to a water plugging agent for oil fields and a preparation method and application thereof. Background Art

[0002] After a period of exploitation, the injected water in the oil field developed by water injection often enters the high permeability layer first due to the multi-layer and heterogeneous nature of the strata, causing these layers to be flooded prematurely, while the low permeability layer cannot be effectively used. This unevenness of the injection profile causes the water content in some blocks to rise rapidly, while the water injection effect in some blocks is not obvious. In order to adjust the water absorption profile of the injection formation and reduce the water output of the oil well, it is necessary to plug the high permeability layer or the water-producing layer. Chemical water plugging technology has gradually become the mainstream method to solve this problem due to its advantages such as simple operation, controllable water plugging and profile adjustment depth, and partial selectivity.

[0003] A good water plugging agent has good dispersibility. After absorbing water and swelling, it is adsorbed on the surface of the rock to block large pores. Generally, there is a phenomenon of water plugging and profile control agent retention in the pore structure. Due to the retention effect, the seepage resistance of the high permeability layer increases, the suction pressure difference between the medium and low permeability layers is increased, and the deep liquid flow is forced to turn and enter the low permeability zone, starting the reservoir with high oil saturation, increasing the suction volume and swept volume of the medium and low permeability layers, realizing deep control and expansion, expanding the swept volume of injected water, improving the water drive development effect, and further improving the purpose of improving the recovery rate.

[0004] 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 control is still not ideal.

[0005] CN101353571A discloses a slag plugging agent for oil and water wells, which is composed of the following components: 30-40% slag, 5-10% suspension dispersant, 0.1%-3.0% hydration activator, and the rest is water. The plugging agent has the characteristics of good suspension stability, good rheology, adjustable curing time, high curing strength, etc. By adjusting the component content in the system, the plugging agent can meet different plugging requirements and can be used for oil and water well profile adjustment and water plugging. It has the characteristics of safety, reliability, low cost, etc. The mineralization degree has little effect on the performance of the plugging agent, but the inorganic plugging agent failed in the article "Analysis of the success and failure factors of the field test of ultra-deep well water plugging in high-temperature fractured oil reservoirs" in "Petroleum Exploration and Development" in April 2005. The reason for the analysis is that after the plugging agent is gelled, it is possible to completely block the oil layer and the water layer, so that no liquid will come out, so this type of inorganic plugging agent has risks in the water plugging operation of high-temperature and high-salinity oil reservoirs. Summary of the invention

[0006] The present invention aims at the above-mentioned deficiencies of the prior art and provides a water plugging agent for oil fields and its preparation method and application. The water plugging agent of the present invention has the characteristics of high viscosity, strong shear resistance and high breakthrough pressure.

[0007] In order to achieve the above objectives:

[0008] In a first aspect, the present invention discloses a method for preparing a water plugging agent for oil fields, and the specific steps of the preparation method are as follows:

[0009] (1) Add N-acryloyl (trimethylol) aminomethane, sodium p-styrene sulfonate, allyl malonic acid, N-(3-(triethoxysilyl)propyl) methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, OP-10 (nonylphenol polyoxyethylene ether), dispersant, buffer salt, and deionized water to the reactor in sequence, stir at high speed until all the raw materials are completely formed into a uniform emulsion, and adjust the pH to 7-8 with sodium hydroxide solution.

[0010] (2) Purge the reactor with nitrogen for 5-10 minutes, and slowly introduce nitrogen in the later stage to ensure that oxygen is isolated as much as possible during the synthesis process; add initiator to the high-level tank and slowly drip it into the reactor. After the dripping is completed, heat it to 40-45°C and continue to stir until the solution becomes viscous, continue to heat it to 70-75°C, continue to stir for 2-3 hours, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0011] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0012] Preferably, the molar ratio of sodium p-styrene sulfonate, allyl malonic acid, N-(3-(triethoxysilyl)propyl)methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol and N-acryloyl(trihydroxymethyl)aminomethane is 0.2-0.4:0.2-0.4:0.1-0.2:0.05-0.1:1.

[0013] Preferably, in step (1), the mass ratio of OP-10, dispersant, buffer salt, deionized water and N-acryloyl(trishydroxymethyl)aminomethane is 0.1-0.2:0.1-0.2:0.05-0.1:10-12:1.

[0014] Preferably, in step (1), the dispersant is one of hydroxypropyl methylcellulose, methyl cellulose and hydroxyethyl cellulose.

[0015] Preferably, in step (1), the buffer salt is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate.

[0016] Preferably, in step (2), the initiator is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 8-15wt%, the concentration of sodium bisulfite is 3-5wt%, and the mass ratio of initiator to N-acryloyl(trihydroxymethyl)aminomethane is 0.1-0.3:1.

[0017] More preferably, the persulfate is one of ammonium persulfate, sodium persulfate and potassium persulfate.

[0018] The reaction equation of the water plugging agent used in the oil field of the present invention is as follows:

[0019]

[0020] In another aspect, the present invention discloses a water plugging agent for oil fields, wherein the molecular structure of the water plugging agent is as follows:

[0021]

[0022] in:

[0023] a=1000-20000;

[0024] b = 20000-200000;

[0025] c = 4000-80000;

[0026] d = 4000-80000;

[0027] e = 2000-40000;

[0028] f = 1000-20000;

[0029] g = 20000-200000;

[0030] h = 4000-80000;

[0031] i = 4000-80000;

[0032] j=2000-40000.

[0033] Preferably, the viscosity-average molecular weight of the water plugging agent is 25,000,000-40,000,000.

[0034] In a third aspect, the present invention discloses the use of the water plugging agent in water plugging and profile control in oil and water wells.

[0035] The water plugging agent for oil fields of the present invention is a high molecular water plugging agent with N-acryloyl (trihydroxymethyl) aminomethane, sodium p-styrene sulfonate, allyl malonic acid, N-(3-(triethoxysilyl) propyl) methacrylamide and 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol as polymerization units. N-acryloyl (trihydroxymethyl) aminomethane is the main polymer, contains a large number of hydrogen bonds, and has strong intermolecular forces; sodium p-styrene sulfonate and allylmalonic acid contain sulfonic acid and carboxyl anions, which are hydrophilic groups, and can make the product molecules adsorb to the surface of large-pore rock formations to improve water plugging efficiency; N-(3-(triethoxysilyl)propyl) methacrylamide molecules contain silicon surfactants, which can seamlessly bond with the rock surface, greatly improving the plugging rate of large pores in the formation and improving water plugging efficiency; 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol is a cross-linking agent, which can greatly increase the molecular weight of the product and increase the product viscosity; dispersants can prevent the emulsion droplets of the polymerized product from becoming excessively large, enhance stability, and improve the polymerization effect.

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

[0037] (1) The water plugging agent for oil fields of the present invention has a relatively high surface viscosity, and the apparent viscosity at 80° C. reaches above 60 mPa.s;

[0038] (2) The water plugging agent for oil fields of the present invention has strong shear resistance and a viscosity retention rate of more than 95%;

[0039] (3) The water plugging agent for oil fields of the present invention has a relatively high breakthrough pressure, which reaches above 10 MPa. 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 present invention will be further described below in conjunction with specific embodiments:

[0042] Example 1

[0043] (1) 0.1 mol N-acryloyl (trihydroxymethyl) aminomethane, 0.02 mol sodium p-styrene sulfonate, 0.04 mol allyl malonic acid, 0.02 mol N-(3-(triethoxysilyl)propyl) methacrylamide, 0.005 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 1.75 g OP-10, 1.75 g hydroxypropyl methylcellulose, 0.88 g sodium dihydrogen phosphate, and 175 g deionized water were added to the reactor in sequence, and stirred at high speed until all the raw materials were completely formed into a uniform emulsion, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0044] (2) Purge the reactor with nitrogen for 5 minutes, and slowly introduce nitrogen in the later stage to ensure that oxygen is isolated as much as possible during the synthesis process. Add 1.75g ​​of initiator to the high-level tank, the initiator contains 15wt% sodium persulfate and 5wt% sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 40°C and continue stirring until the solution becomes viscous. Continue to heat it to 70°C and continue stirring for 2.3h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0045] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0046] Example 2

[0047] (1) 0.1 mol of N-acryloyl (trihydroxymethyl) aminomethane, 0.022 mol of sodium p-styrene sulfonate, 0.035 mol of allyl malonic acid, 0.018 mol of N-(3-(triethoxysilyl)propyl) methacrylamide, 0.006 mol of 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 2 g of OP-10, 2.2 g of hydroxypropyl methylcellulose, 1.1 g of sodium dihydrogen phosphate, and 188 g of deionized water were added to the reactor in sequence, and stirred at high speed until all the raw materials were completely formed into a uniform emulsion, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0048] (2) Purge the reactor with nitrogen for 10 minutes, and slowly introduce nitrogen in the later process to ensure that oxygen is isolated as much as possible during the synthesis process. Add 2.5g of initiator to the high-level tank, the initiator contains 15wt% sodium persulfate and 5wt% sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 45°C and continue stirring until the solution becomes viscous. Continue to heat it to 75°C and continue stirring for 2.6h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0049] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0050] Example 3

[0051] (1) 0.1 mol N-acryloyl (trihydroxymethyl) aminomethane, 0.025 mol sodium p-styrene sulfonate, 0.032 mol allyl malonic acid, 0.016 mol N-(3-(triethoxysilyl)propyl) methacrylamide, 0.007 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 2.2 g OP-10, 2.5 g hydroxypropyl methylcellulose, 1.2 g sodium dihydrogen phosphate, and 185 g deionized water were added to the reactor in sequence and stirred at high speed until all the raw materials were completely formed into a uniform emulsion, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0052] (2) Purge the reactor with nitrogen for 8 minutes, and slowly introduce nitrogen in the later process to ensure that oxygen is isolated as much as possible during the synthesis process. Add 3.1g of initiator to the high-level tank, the initiator contains 12wt% of sodium persulfate and 4wt% of sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 40°C and continue stirring until the solution becomes viscous. Continue to heat it to 72°C and continue stirring for 2.2h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0053] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0054] Example 4

[0055] (1) 0.1 mol N-acryloyl (trihydroxymethyl) aminomethane, 0.03 mol sodium p-styrene sulfonate, 0.03 mol allyl malonic acid, 0.015 mol N-(3-(triethoxysilyl)propyl) methacrylamide, 0.008 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 2.5 g OP-10, 2.8 g methyl cellulose, 1.3 g sodium dihydrogen phosphate, and 196 g deionized water were added to the reactor in sequence and stirred at high speed until all the raw materials were completely formed into a uniform emulsion, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0056] (2) Purge the reactor with nitrogen for 7 minutes, and slowly introduce nitrogen in the later stage to ensure that oxygen is isolated as much as possible during the synthesis process. Add 3.5g of initiator to the high-level tank, the initiator contains 12wt% sodium persulfate and 4wt% sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 45°C and continue stirring until the solution becomes viscous. Continue to heat it to 73°C and continue stirring for 2.5h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0057] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0058] Example 5

[0059] (1) 0.1 mol N-acryloyl (trihydroxymethyl) aminomethane, 0.033 mol sodium p-styrene sulfonate, 0.027 mol allyl malonic acid, 0.014 mol N-(3-(triethoxysilyl)propyl) methacrylamide, 0.008 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 2.8 g OP-10, 3 g methyl cellulose, 1.4 g potassium dihydrogen phosphate, and 200 g deionized water were added to the reactor in sequence and stirred at high speed until all the raw materials were completely formed into a uniform emulsion, and the pH was adjusted to 7-8 with sodium hydroxide solution.

[0060] (2) Purge the reactor with nitrogen for 6 minutes, and slowly introduce nitrogen in the later process to ensure that oxygen is isolated as much as possible during the synthesis process. Add 4g of initiator to the high-level tank, the initiator contains 10wt% ammonium persulfate and 4wt% sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 42°C and continue stirring until the solution becomes viscous. Continue to heat it to 71°C and continue stirring for 3h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0061] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0062] Example 6

[0063] (1) 0.1 mol N-acryloyl (trihydroxymethyl) aminomethane, 0.035 mol sodium p-styrene sulfonate, 0.025 mol allyl malonic acid, 0.013 mol N-(3-(triethoxysilyl)propyl) methacrylamide, 0.009 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 3 g OP-10, 3.2 g methyl cellulose, 1.5 g potassium dihydrogen phosphate, and 205 g deionized water were added to the reactor in sequence and stirred at high speed until all the raw materials were completely formed into a uniform emulsion. The pH was adjusted to 7-8 with sodium hydroxide solution.

[0064] (2) Purge the reactor with nitrogen for 8 minutes, and slowly introduce nitrogen in the later stage to ensure that oxygen is isolated as much as possible during the synthesis process. Add 1.75g ​​of initiator to the high-level tank, the initiator contains 10wt% ammonium persulfate and 4wt% sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 43°C and continue stirring until the solution becomes viscous. Continue to heat it to 74°C and continue stirring for 2h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0065] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0066] Example 7

[0067] (1) 0.1 mol of N-acryloyl(trihydroxymethyl)aminomethane, 0.037 mol of sodium p-styrenesulfonate, 0.023 mol of allylmalonic acid, 0.012 mol of N-(3-(triethoxysilyl)propyl)methacrylamide, 0.009 mol of 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 3.2 g of OP-10, 3.4 g of hydroxyethyl cellulose, 1.6 g of diammonium phosphate, and 210 g of deionized water were added to the reactor in sequence and stirred at high speed until all the raw materials were completely formed into a uniform emulsion. The pH was adjusted to 7-8 with sodium hydroxide solution.

[0068] (2) Purge the reactor with nitrogen for 10 minutes, and slowly introduce nitrogen in the later process to ensure that oxygen is isolated as much as possible during the synthesis process. Add 4.8g of initiator to the high-level tank, the initiator contains 8wt% potassium persulfate and 3wt% sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 44°C and continue stirring until the solution becomes viscous. Continue to heat it to 72°C and continue stirring for 2h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0069] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0070] Example 8

[0071] (1) 0.1 mol N-acryloyl (trihydroxymethyl) aminomethane, 0.04 mol sodium p-styrene sulfonate, 0.02 mol allyl malonic acid, 0.01 mol N-(3-(triethoxysilyl)propyl) methacrylamide, 0.01 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, 3.5 g OP-10, 3.5 g hydroxyethyl cellulose, 1.75 g diammonium phosphate, and 210 g deionized water were added to the reactor in sequence and stirred at high speed until all the raw materials were completely formed into a uniform emulsion. The pH was adjusted to 7-8 with sodium hydroxide solution.

[0072] (2) Purge the reactor with nitrogen for 9 minutes, and slowly introduce nitrogen in the later process to ensure that oxygen is isolated as much as possible during the synthesis process. Add 5.25g of initiator to the high-level tank, the initiator contains 8wt% potassium persulfate and 3wt% sodium bisulfite, and slowly add it dropwise to the reactor. After the addition is completed, heat it to 41°C and continue stirring until the solution becomes viscous, continue to heat it to 73°C, continue stirring for 3h, cool it to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0073] (3) The viscous liquid is dried and granulated into particles with a particle size of 1-4 mm to obtain a water plugging agent product.

[0074] Example 9: Test of apparent viscosity

[0075] The water plugging agent (Examples 1-8) of the present invention was diluted with water to a solution with a concentration of 5000 mg / L, and the apparent viscosity was tested using a Haake rheometer at 80°C.

[0076] The polyacrylamide produced by Shengli Petrochemical Co., Ltd. was used as a comparative sample. The test results are shown in Table 1.

[0077] From Table 1 we can see that:

[0078] The water plugging agent for oil field of the present invention (Examples 1-8) has a relatively high surface viscosity.

[0079] When the concentration is 5000 mg / L and the temperature is 80° C., the apparent viscosity reaches above 60 mPa.s, and the highest reaches 67 mPa.s (Example 8), while the apparent viscosity of the comparative example is 12 mPa.s, which is significantly lower than that of the present invention.

[0080] Example 10 Evaluation of shear resistance

[0081] The sample in Example 9 was heated at 80°C and 170S -1 Shear continuously for 2 hours under the conditions and test the apparent viscosity.

[0082] The polyacrylamide produced by Shengli Petrochemical Co., Ltd. was used as a comparative sample. The test results are shown in Table 1.

[0083] From Table 1 we can see that:

[0084] The water plugging agent for oil field of the present invention (Examples 1-8) has strong anti-shear ability, and the use concentration is 5000 mg / L, at 80°C, 170S -1 Under the conditions of continuous shearing for 2 hours, the viscosity retention rate reaches more than 95%, and the highest reaches 97.0% (Example 7), while the viscosity retention rate of the comparative example is 75%, which is significantly lower than that of the present invention.

[0085] Example 11 Testing of plugging strength

[0086] At 80°C, an artificial core (length 6.5 cm, permeability 0.26 μm) was used. 2 ), squeeze and inject 1PV, 5000mg / L of the water plugging agent of the present invention (Example 1-8), and test its plugging strength.

[0087] The polyacrylamide produced by Shengli Petrochemical Co., Ltd. was used as a comparative sample. The test results are shown in Table 1.

[0088] Table 1 Test results of apparent viscosity, shear resistance and breakthrough pressure

[0089]

[0090] From Table 1 we can see that:

[0091] The water plugging agent for oil fields of the present invention (Examples 1-8) has a relatively high breakthrough pressure. When the concentration is 5000 mg / L, the breakthrough pressure reaches above 10 MPa, and the highest reaches 11.2 MPa (Example 1), while the breakthrough pressure of the comparative example is 2.3 MPa, which is significantly lower than that of the present invention.

[0092] 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 water plugging agent for oil fields, characterized in that: The specific steps of the preparation method are as follows: (1) Add N-acryloyl (trimethylol) aminomethane, sodium p-styrene sulfonate, allyl malonic acid, N-(3-(triethoxysilyl)propyl) methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol, OP-10, dispersant, buffer salt, and deionized water to the reactor in sequence, stir at high speed until all raw materials are completely formed into a uniform emulsion, and adjust the pH to 7-8 with sodium hydroxide solution; (2) Purge the reactor with nitrogen for 5-10 minutes, and slowly introduce nitrogen in the later stage to ensure that oxygen is isolated as much as possible during the synthesis process; add the initiator to the high-level tank and slowly drip it into the reactor. After the dripping is completed, heat it to 40-45° C. and continue to stir until the solution becomes viscous, continue to heat it to 70-75° C., continue to stir for 2-3 hours, cool it to below 40° C., and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid; (3) drying and granulating the viscous liquid to obtain a water plugging agent product with a particle size of 1-4 mm; The molar ratio of sodium p-styrene sulfonate, allyl malonic acid, N-(3-(triethoxysilyl)propyl)methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1,6-diene-4-ol and N-acryloyl(trihydroxymethyl)aminomethane is 0.2-0.4:0.2-0.4:0.1-0.2:0.05-0.1:

1.

2. The method for preparing a water plugging agent for oil fields according to claim 1, characterized in that: In step (1), the mass ratio of OP-10, dispersant, buffer salt, deionized water and N-acryloyl (trishydroxymethyl) aminomethane is 0.1-0.2:0.1-0.2:0.05-0.1:10-12:

1.

3. The method for preparing a water plugging agent for oil fields according to claim 1, characterized in that: In step (1), the dispersant is one of hydroxypropyl methylcellulose, methyl cellulose and hydroxyethyl cellulose.

4. The method for preparing a water plugging agent for oil fields according to claim 1, characterized in that: In step (1), the buffer salt is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate.

5. The method for preparing a water plugging agent for oil fields 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 8-15wt%, the concentration of sodium bisulfite is 3-5wt%, and the mass ratio of the initiator to N-acryloyl(trihydroxymethyl)aminomethane is 0.1-0.3:

1.

6. The method for preparing a water plugging agent for oil fields according to claim 5, characterized in that: The persulfate is one of ammonium persulfate, sodium persulfate and potassium persulfate.

7. A water plugging agent for oil fields, characterized in that: The molecular structural formula of the water plugging agent is as follows: in: a＝1000-20000； b＝20000-200000； c＝4000-80000； d＝4000-80000； e＝2000-40000； f＝1000-20000； g＝20000-200000； h＝4000-80000； i＝4000-80000； j＝2000-40000。 8. The water plugging agent according to claim 7, characterized in that: The viscosity average molecular weight of the water plugging agent is 25,000,000-40,000,000.

9. Use of the water plugging agent according to claim 7 or 8 in water plugging and profile control in oil and water wells.

Images