A water-blocking agent for oil fields, its preparation method and application

Abstract

This invention belongs to the field of tertiary oil recovery technology, specifically relating to a water-blocking agent for oilfields, its preparation method, and its application. The preparation method is as follows: N-acryloyl(tris(hydroxymethyl)aminomethane), sodium p-styrenesulfonate, allylmalonic acid, N-(3-(triethoxysilyl)propyl)methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1,6-dien-4-ol, OP-10, dispersant, buffer salt, and deionized water are added sequentially to a reactor. The mixture is stirred, and the pH is adjusted to 7-8. An initiator is added to a high-level tank and slowly dripped into the reactor. After the dripping is complete, the temperature is raised to 40-45°C, and stirring continues. The temperature is then raised to 70-75°C, and stirring continues for 2-3 hours. The temperature is then lowered to below 40°C, and the pH is adjusted to 7-8 to obtain a viscous liquid. The liquid is then dried and granulated to obtain the water-blocking agent product. The water-blocking agent of this invention has the characteristics of high viscosity, strong shear resistance, and high breakthrough pressure.

Description

Technical Field

[0001] This invention belongs to the field of tertiary oil recovery technology, specifically relating to a water shut-off agent for oil fields, its preparation method, and its application. Background Technology

[0002] In water-injected oilfields, after a period of production, due to the multi-layered and heterogeneous nature of the formations, injected water often preferentially enters high-permeability layers, causing these layers to flood prematurely, while low-permeability layers remain unutilized. This unevenness in the injection profile leads to a rapid increase in water content in some blocks, while the water injection effect is not significant in others. To adjust the water absorption profile of the injected formation and reduce water production from wells, sealing high-permeability or water-producing layers becomes a necessary measure. Chemical water shut-off technology, due to its advantages such as ease of operation, controllable water shut-off and profile adjustment depth, and selectivity in some cases, has gradually become the mainstream method for solving this problem.

[0003] A good water-blocking agent has good dispersibility. After absorbing water and swelling, it adsorbs onto the rock surface and seals large pores. Generally, water-blocking and profile control agents are retained in the pore structure. This retention increases the seepage resistance in high-permeability layers, raises the pressure difference between medium and low-permeability layers, forces the deep fluid flow to change direction, enters the low-permeability zone, activates reservoirs with higher oil saturation, increases the fluid absorption and swept volume in medium and low-permeability layers, achieves deep water drive, expands the injected water swept volume, improves waterflooding development, and further enhances oil recovery.

[0004] CN114805677B discloses a polymer flooding agent and its preparation method, relating to the fields of oilfield chemical additives and polymer polymerization. The method includes: reacting a nitrile compound, fuming sulfuric acid, and a long-chain olefin to obtain a dendritic branched monomer; mixing the dendritic branched monomer, acrylamide, acrylic acid, deionized water, and a pH adjuster to obtain a mixed solution; introducing nitrogen gas into the mixed solution, and then adding an initiator to initiate a polymerization reaction to obtain the polymer flooding agent. The polymer flooding agent prepared by this invention has a strong chelating effect on calcium and magnesium ions, making it suitable for operation in high-salinity areas. It exhibits salt resistance, high temperature resistance, and high thermal stability; even after 3 months under anaerobic conditions at 120°C, the solution viscosity still maintains a high retention rate. However, the apparent viscosity of this invention is below 80 mPa·s, and the effect of water shut-off and profile control is still not ideal.

[0005] CN101353571A discloses a slag plugging agent for oil and water wells, composed of the following components: 30-40% slag, 5-10% suspending dispersant, 0.1%-3.0% hydration activator, and the remainder being water. This plugging agent exhibits good suspension stability, good rheological properties, adjustable curing time, and high curing strength. By adjusting the component content in the system, the plugging agent can meet different plugging requirements and is applicable to profile control and water shut-off in oil and water wells. It is safe, reliable, and low-cost. While salinity has a relatively small impact on the performance of the plugging agent, this inorganic plugging agent failed in the April 2005 issue of *Petroleum Exploration and Development* in the article "Analysis of Success and Failure Factors in Field Tests of Water Shut-off in Ultra-Deep Wells of High-Temperature Fractured Reservoirs." The analysis suggested that after gelation, the plugging agent might completely seal both the oil and water layers, preventing fluid from being produced. Therefore, this type of inorganic plugging agent poses a risk in water shut-off operations in high-temperature, high-salinity reservoirs. Summary of the Invention

[0006] This invention addresses the shortcomings of the prior art by providing a water-blocking agent for oil fields, its preparation method, and its application. The water-blocking agent of this invention features high viscosity, strong shear resistance, and high breakthrough pressure.

[0007] To achieve the above objectives:

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

[0009] (1) N-acryloyl(tris(hydroxymethyl)aminomethane), sodium p-styrenesulfonate, allylmalonic acid, N-(3-(triethoxysilyl)propyl)methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1,6-dien-4-ol, OP-10 (nonylphenol polyoxyethylene ether), dispersant, buffer salt, and deionized water were added to the reactor in sequence. The mixture was stirred at high speed until all raw materials were completely formed into a homogeneous emulsion. The pH was adjusted to 7-8 with sodium hydroxide solution.

[0010] (2) Purge the reactor with nitrogen for 5-10 minutes. In the later stages of the process, slowly introduce nitrogen to ensure that oxygen is isolated as much as possible during the synthesis. Add the initiator to the high-level tank and slowly add it to the reactor. After the addition is complete, raise the temperature to 40-45℃ and continue stirring until the solution becomes viscous. Continue to raise the temperature to 70-75℃ and continue stirring for 2-3 hours. Cool down to below 40℃ and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0011] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking 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-dien-4-ol to 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(trihydroxymethyl)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, methylcellulose, and hydroxyethylcellulose.

[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 8-15 wt%, the concentration of sodium bisulfite is 3-5 wt%, 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 for the water shut-off agent of this invention used in oil fields is as follows:

[0019]

[0020] In another aspect, this invention discloses a water-blocking agent for oil fields, the molecular structural formula of which 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-blocking agent is 25,000,000-40,000,000.

[0034] Thirdly, this invention discloses the application of the above-mentioned water-blocking agent in water plugging and profile control of oil and water wells.

[0035] The water-blocking agent for oil fields of the present invention is a polymeric water-blocking agent with N-acryloyl(trihydroxymethyl)aminomethane, sodium p-styrenesulfonate, allylmalonic acid, N-(3-(triethoxysilyl)propyl)methacrylamide, and 4-(1-amino-2-methyl-propyl)-hepta-1,6-dien-4-ol as polymeric units. N-Acryloyl(tris(hydroxymethyl)aminomethane) is the polymer matrix, containing a large number of hydrogen bonds and strong intermolecular forces. Sodium p-styrenesulfonate and allylmalonic acid contain sulfonic acid and carboxyl anions, which are hydrophilic groups, allowing the product molecules to adsorb onto the surface of large-pore rock formations, thus improving water shut-off efficiency. N-(3-(triethoxysilyl)propyl)methacrylamide contains a silicone surfactant, which can seamlessly bond with the rock surface, significantly increasing the plugging rate of large-pore formations and improving water shut-off efficiency. 4-(1-amino-2-methyl-propyl)-hepta-1,6-dien-4-ol is a crosslinking agent, which can significantly increase the molecular weight and viscosity of the product. The dispersant can prevent the emulsion droplets of the polymerized product from becoming excessively large, enhancing stability and improving the polymerization effect.

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

[0037] (1) The water shut-off agent for oil fields of the present invention has a high surface viscosity, with an apparent viscosity of more than 60 mPa·s at 80°C;

[0038] (2) The water shut-off agent for oil fields of the present invention has strong shear resistance and viscosity retention rate of over 95%.

[0039] (3) The water shut-off agent for oil fields of the present invention has a high breakthrough pressure, which reaches more than 10 MPa. Detailed Implementation

[0040] 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.

[0041] The present invention will be further described below with reference to specific embodiments:

[0042] Example 1

[0043] (1) 0.1 mol N-acryloyl(tris(hydroxymethyl)aminomethane), 0.02 mol sodium p-styrenesulfonate, 0.04 mol allylmalonic acid, 0.02 mol N-(3-(triethoxysilyl)propyl)methacrylamide, 0.005 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-dien-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. The mixture was stirred at high speed until all raw materials were completely formed into a homogeneous emulsion. The pH was adjusted to 7-8 with sodium hydroxide solution.

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

[0045] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0046] Example 2

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

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

[0049] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0050] Example 3

[0051] (1) 0.1 mol N-acryloyl(tris(hydroxymethyl)aminomethane), 0.025 mol sodium p-styrenesulfonate, 0.032 mol allylmalonic acid, 0.016 mol N-(3-(triethoxysilyl)propyl)methacrylamide, 0.007 mol 4-(1-amino-2-methyl-propyl)-hepta-1,6-dien-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. The mixture was stirred at high speed until all raw materials were completely formed into a homogeneous emulsion. The pH was adjusted to 7-8 with sodium hydroxide solution.

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

[0053] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0054] Example 4

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

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

[0057] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0058] Example 5

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

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

[0061] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0062] Example 6

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

[0064] (2) Purge the reactor with nitrogen for 8 minutes. In the later stages of the process, slowly introduce nitrogen to ensure that oxygen is isolated as much as possible during the synthesis. Add 1.75g ​​of initiator to the high-level tank. The initiator contains 10wt% ammonium persulfate and 4wt% sodium bisulfite. Add it slowly dropwise to the reactor. After the addition is complete, raise the temperature to 43℃ and continue stirring until the solution becomes viscous. Continue to raise the temperature to 74℃ and continue stirring for 2 hours. Cool down to below 40℃ and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid.

[0065] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0066] Example 7

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

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

[0069] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0070] Example 8

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

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

[0073] (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product.

[0074] Example 9: Test of apparent viscosity

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

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

[0077] As can be seen from Table 1:

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

[0079] When the concentration is 5000 mg / L and the temperature is 80°C, the apparent viscosity reaches more than 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 Shear resistance evaluation

[0081] The sample from Example 9 was subjected to 80°C for 170 seconds. -1 Under the condition of continuous shearing for 2 hours, the apparent viscosity was tested.

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

[0083] As can be seen from Table 1:

[0084] The water shut-off agent for oil fields of the present invention (Examples 1-8) has strong shear resistance. It is used at a concentration of 5000 mg / L at 80°C for 170 seconds. -1 Under the condition of continuous shearing for 2 hours, the viscosity retention rate reached more than 95%, with a maximum of 97.0% (Example 7), while the viscosity retention rate of the comparative example was 75%, which is significantly lower than that of the present invention.

[0085] Example 11: Testing of sealing strength

[0086] At 80℃, an artificially sealed rock core (6.5 cm in length, with a permeability of 0.26 μm) was prepared. 2 ), and inject 1PV, 5000mg / L of the water-blocking agent of the present invention (Examples 1-8), and test its sealing strength.

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

[0088] Table 1. Results of apparent viscosity, shear resistance, and breakthrough pressure tests.

[0089]

[0090] As can be seen from Table 1:

[0091] The water shut-off agent for oil fields of the present invention (Examples 1-8) has a high breakthrough pressure. When the concentration is 5000 mg / L, the breakthrough pressure reaches more than 10 MPa, and the highest reaches 11.2 MPa (Example 1). In contrast, 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 have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a water-blocking agent for oil fields, characterized in that, The specific steps of the preparation method are as follows: (1) N-acryloyl(tris(hydroxymethyl)aminomethane), sodium p-styrenesulfonate, allylmalonic acid, N-(3-(triethoxysilyl)propyl)methacrylamide, 4-(1-amino-2-methyl-propyl)-hepta-1,6-dien-4-ol, OP-10, dispersant, buffer salt, and deionized water were added to the reactor in sequence. The mixture was stirred at high speed until all raw materials were completely formed into a homogeneous emulsion. The pH was adjusted to 7-8 with sodium hydroxide solution. (2) Purge the reactor with nitrogen for 5-10 minutes. In the later stages of the process, slowly introduce nitrogen to ensure that oxygen is isolated as much as possible during the synthesis. Add the initiator to the high-level tank and slowly add it to the reactor. After the addition is complete, raise the temperature to 40-45℃ and continue stirring until the solution becomes viscous. Continue to raise the temperature to 70-75℃ and continue stirring for 2-3 hours. Cool down to below 40℃ and adjust the pH to 7-8 with sodium hydroxide solution to obtain a viscous liquid. (3) The above viscous liquid is dried and granulated to a particle size of 1-4 mm to obtain the water-blocking agent product; 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-dien-4-ol to 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-blocking 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(trihydroxymethyl)aminomethane is 0.1-0.2:0.1-0.2:0.05-0.1:10-12:

1.

3. The method for preparing a water-blocking agent for oil fields according to claim 1, characterized in that, In step (1), the dispersant is one of hydroxypropyl methylcellulose, methylcellulose, and hydroxyethylcellulose.

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

1.

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

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