Nanoscale water shutoff agent and preparation method thereof

Abstract

The invention discloses a nanoscale water plugging agent which comprises the following components in parts by weight: 5-8 parts of white oil; 30 to 40 parts of a comonomer; 10 to 14 parts of a composite emulsifier; 20 to 26 parts of a composite monomer; 20 to 26 parts of deionized water; 0.2 to 0.3 part of a cross-linking agent; 2 to 3 parts of rhamnolipid; 2 to 3 parts of phosphatidyl ethanolamine; and 0.02 to 0.03 part of an initiator. The water plugging agent can smoothly enter the deep part of a stratum along with injected water, and plugging of a stratum pore throat is realized after the water swelling. The invention also discloses a preparation method of the nanoscale water shutoff agent.

Description

Technical Field

[0001] The invention belongs to the technical field of oil well water plugging materials, and in particular relates to a nanometer-level water plugging agent and a preparation method of the nanometer-level water plugging agent. Background Art

[0002] As the development time of oil fields increases, the formation pressure continues to decline. Most oil fields mainly use the "secondary oil recovery" method of water injection development to increase production and crude oil recovery. For an oil field with long-term water injection development, due to the horizontal and vertical heterogeneity of the reservoir and the difference in oil and water viscosity, the injected water will inevitably rush and flow along the high permeability zone to the production well, resulting in inefficient or ineffective circulation of the injected water. After decades of intensive exploitation, many oil fields in my country have entered the medium and high water content period. At this time, the underground recoverable reserves are still large, and there are still about 40% of the water injection reserves that have not been used. However, the efficiency of the production and injection measures that were widely used under water injection conditions has become increasingly low, and the situation of "high water content, high input, and low output" has emerged, making the water injection development technology more and more difficult, the output is decreasing, the water production is greatly increased, and the economic benefits are poor. At the same time, fracturing, acidification, and high-intensity mining will cause problems such as injected water tongue, edge water intrusion, bottom water cone intrusion, and external water intrusion, which not only affects the recovery of crude oil, but also consumes energy, increases the cost of processing the produced fluid, and causes corrosion of pipelines, thereby increasing the cost of crude oil recovery and causing environmental pollution. Some oil wells may also experience explosive flooding, resulting in the closure of oil wells and a large waste of resources. Therefore, how to effectively block water has become a serious problem faced in oil field development.

[0003] At present, the water plugging technology in oil fields is mainly divided into two categories: mechanical water plugging and chemical water plugging. The so-called mechanical water plugging technology is to use a packer to block the water-producing layer in the wellbore to prevent water from flowing into the well and block the water-producing layer section in the oil well. There are four water plugging methods: sealing the upper part to block the lower part, sealing the lower part to block the upper part, sealing the middle part to produce both ends, and sealing the two ends to produce the middle part. This technology requires the packer seat to be tightly and accurately sealed, which is the guarantee for the success of mechanical water plugging. The mechanical water plugging method is simple, easy to operate, low cost, and effective, but it is not easy to use in oil wells where the lower packer or other reasons cannot separate oil and water. Oil well chemical water plugging is a process technology that injects chemicals into the high permeability water-producing layer section through the oil well to reduce the water phase permeability of the near-well zone, control the output of injected water, bottom water and edge water, and thus increase crude oil production. The chemical water plugging method does not require well repair equipment, the operation is economical and convenient, and it is widely used.

[0004] The chemical agent used in chemical water plugging is called water plugging agent. At present, there are three main types of water plugging agents, namely polymer gel plugging agent (jelly gel type), water glass calcium chloride precipitation plugging agent (water swelling type), cement type, etc., but all of them have certain limitations. When the oil well is extremely serious in water production, cement plugging agents are often used for plugging, but cement will cause permanent plugging of the formation and does not have the function of selective water plugging. Cement water plugging agents have fast pressure increase, are easily diluted by formation fluids, do not condense or have low condensation strength, and there is a risk of flagpole insertion. Water swelling plugging agents are mostly solid phase particles, which swell when exposed to water. They are often injected in the form of double liquid segment plugs to achieve the purpose of precipitation and plugging water in the reservoir. However, this type of plugging agent has the problem of unpredictable precipitation reaction timing, and is easy to accumulate in the near-wellbore area, resulting in rapid pressure increase in the wellbore and blockage near the wellbore. In addition, this type of plugging agent has poor scouring resistance and is not suitable for profile control and water plugging operations in fractured reservoirs. Gel plugging agents can enter deep reservoirs. They are mainly polymer gels formed by polyacrylamide or acrylamide copolymers plus crosslinking agents and other additives. They have been widely used in chemical profile control and water plugging technology. However, this type of plugging agent needs to be crosslinked underground, so it is affected by conditions such as formation temperature and prepared water, especially by formation pore shear, with obvious viscosity loss, fast gel breaking and short effective period.

[0005] At present, new water plugging agents and their supporting technologies continue to emerge and have obtained relevant patents. Chinese invention patent CN105967600A discloses an endogenous toughened corrosion-resistant cement slurry system, which has good impact resistance and compressive strength, and solves the problem of poor dispersibility and compatibility of exogenous toughened cement slurry systems. However, when the solidified cement stone is damaged by stress and produces microcracks, it does not have self-repairing ability, nor does it have hydrogen sulfide resistance. Therefore, it is not suitable for wellbore plugging of high-sulfur gas well continuous oil pipes. Chinese invention patent CN1888374A discloses "a high-temperature and high-salt resistant gel water plugging method". The main plugging section is a cross-linked system with modified tannin as the main agent, with a concentration of 3-12%, and the cross-linking agent is an aldehyde concentration range of 0.5-4.0%, or phenols, with a concentration range of 0.2-1.0%, and the auxiliary agent is an alkali or salt, with a concentration range of 0.3-1.2%. The applicable temperature range is 90-280℃. Chinese patent CN101086210A discloses "a coalbed methane profile control and water plugging technology", and designs a process scheme for water plugging agent and its dosage according to the principle of segmented plug design of water plugging gel system, gradual increase in strength, moderate gel viscosity, and reasonable crosslinking time of each segment plug, wherein the gel is mixed with polyacrylamide with a mother liquor of 0.04-1.0% mass concentration and modified phenolic resin as a crosslinking agent, and gels in situ to plug large fracture channels at formation temperature. Chinese patent CN101481604A discloses "gel foam selective water plugging agent and its application", and the basic formula of water plugging agent is: polyacrylamide, mass concentration: 30-50%, crosslinking agent: hexamethylenetetramine, mass concentration: 20-40%, phenol, mass concentration: 5-15%, tetraethylenepentamine, mass concentration: 5-15%, foaming agent, mass concentration: 5-15%, and a 0.5-2% aqueous solution is prepared on site, which can be used for oil well water plugging at 90-150°C. Many current selective plugging agents are based on a mixture of linear polymers and cross-linking agents. They are still a continuous bulk gel and cannot be truly selective water plugging agents. Summary of the invention

[0006] The first object of the present invention is to provide a nanometer-scale water-blocking agent, which can smoothly enter the deep formation along with the injected water, and after swelling in contact with water, can block the pore throats of the formation.

[0007] The second object of the present invention is to provide a method for preparing a nanoscale water plugging agent.

[0008] The first technical solution adopted by the present invention is that the nanoscale water plugging agent specifically comprises the following components in parts by weight:

[0009]

[0010] The present invention is also characterized in that:

[0011] The comonomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, alkylsulfonic acetamide and alkyl succinate sulfonate in random proportions.

[0012] The composite emulsifier is composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether mixed in any ratio;

[0013] The composite monomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N-vinyl pyrrolidone and ethylenediaminetetraacetic acid mixed in any proportion.

[0014] The crosslinking agent is N,N'-methylenebisacrylamide.

[0015] The initiator is azobisisobutyronitrile or azobisisoheptanitrile, or a mixture of azobisisobutyronitrile and azobisisoheptanitrile, and the volume ratio of the two in the mixture is 1:1.

[0016] The second technical solution adopted by the present invention is a method for preparing the above-mentioned nanoscale water plugging agent, which specifically comprises the following steps:

[0017] Step 1, preparing the oil phase;

[0018] Step 2, preparing the aqueous phase;

[0019] Step 3, placing the oil phase in a reaction kettle, stirring the solution evenly with a magnetic stirring needle, and then slowly adding the water phase for emulsification while stirring. The emulsification time is 0.5 hour to 1 hour;

[0020] Step 4: After emulsification is completed, the temperature is raised and nitrogen is introduced for 0.5 hour to 1 hour for deoxygenation;

[0021] Step 5, heating again, adding azobisisobutyronitrile or azobisisoheptanenitrile initiator to initiate polymerization reaction, and keeping warm for 2 hours to 3 hours;

[0022] The present invention is also characterized in that:

[0023] Step 1 is as follows:

[0024] Add a copolymer monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide and alkyl succinate sulfonate in any ratio into white oil, stir evenly, and then add a composite emulsifier mixed with sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio to prepare an oil phase.

[0025] Step 2 is as follows:

[0026] A composite monomer of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone and ethylenediaminetetraacetic acid mixed in any ratio is weighed and dissolved in deionized water, and then a cross-linking agent of N,N'-methylenebisacrylamide, rhamnolipid and phosphatidylethanolamine are added in sequence, and the mixture is mixed and stirred evenly to prepare an aqueous phase.

[0027] In step 4, the temperature raising treatment is specifically as follows: using a reaction kettle to raise the temperature to 30° C.;

[0028] In step 5, after the temperature is raised to 60° C. again, azobisisobutyronitrile or azobisisoheptanenitrile initiator is added to initiate a polymerization reaction;

[0029] Step 6 specifically comprises: after cooling to room temperature, centrifuging the liquid obtained in step 5 after the polymerization reaction with anhydrous ethanol at a rotation speed of 6000 rpm-8000 rpm for 10 minutes-15 minutes.

[0030] The beneficial effects of the present invention are:

[0031] (1) The water plugging agent of the present invention has a particle size of only nanometers. In the initial stage of injection, since the original size of the nanometer-scale water plugging agent is much smaller than the size of the formation pore throat, it can smoothly enter the deep formation along with the injected water, and after swelling in water, it can achieve the plugging of the formation pore throat.

[0032] (2) As the injection time continues to increase, the nanoscale water plugging agent of the present invention continues to hydrate and expand, and the final expansion system can reach 80 to 100 times the initial volume, thereby blocking large pores or high permeability layers, improving the liquid production profile, and forming a dynamic accumulation zone to block the end matrix micropores.

[0033] (3) The water plugging agent of the present invention can expand the swept volume as the injected water advances, drive out more residual oil, and improve the oil well recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a water blocking principle diagram of the nano-scale water blocking agent of the present invention;

[0035] Figure 2 This is a microscopic morphology of the nanoscale water plugging agent prepared in Example 1 of the present invention.

[0036] In the figure, 1. Formation pore throat, 2. Water plugging agent. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with specific implementation modes.

[0038] The present invention provides a nanoscale water plugging agent, which comprises the following components in parts by weight:

[0039]

[0040]

[0041] The comonomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, alkylsulfonic acetamide and alkyl succinate sulfonate in random proportions.

[0042] The composite emulsifier is composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether mixed in any ratio;

[0043] The composite monomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N-vinyl pyrrolidone and ethylenediaminetetraacetic acid mixed in any proportion.

[0044] The crosslinking agent is N,N'-methylenebisacrylamide.

[0045] The initiator is azobisisobutyronitrile or azobisisoheptanitrile, or a mixture of azobisisobutyronitrile and azobisisoheptanitrile, and the volume ratio of the two in the mixture is 1:1.

[0046] The present invention also provides a method for preparing the above-mentioned nanoscale water plugging agent, which specifically comprises the following steps:

[0047] Step 1, adding a copolymer monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkylsulfonic acetamide, and alkyl succinate sulfonate in any ratio into white oil, stirring evenly, and then adding a composite emulsifier composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio to prepare an oil phase.

[0048] Step 2: weigh a composite monomer of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in any ratio, dissolve it in deionized water, and then add N,N'-methylenebisacrylamide crosslinking agent, rhamnolipid, and phosphatidylethanolamine in sequence, mix and stir evenly to prepare an aqueous phase.

[0049] Step 3, placing the oil phase in a reaction kettle, stirring the solution evenly with a magnetic stirring needle, and then slowly adding the water phase for emulsification while stirring. The emulsification time is 0.5 hour to 1 hour;

[0050] Step 4: After emulsification is completed, the reactor is heated to 30°C and nitrogen is introduced for 0.5-1 hour to remove oxygen;

[0051] Step 5, after heating to 60° C., add azobisisobutyronitrile or azobisisoheptanenitrile initiator to initiate polymerization reaction, and keep warm for 2 to 3 hours;

[0052] Step 6, after cooling to room temperature, obtain nano-scale water plugging agent by centrifugation; specifically, after cooling to room temperature, centrifuge the liquid obtained in step 5 after polymerization with anhydrous ethanol at a speed of 6000rpm-8000rpm and a centrifugation time of 10 minutes-15 minutes.

[0053] The principle of using the water plugging agent of the present invention to plug water is as follows Figure 1 As shown, since the water plugging agent 2 is nanometer-scale and its microstructure is microspherical, in the initial stage of injection, since the original size of the nanometer water plugging agent is much smaller than the size of the formation pore throat 1, it can smoothly enter the deep formation with the injected water, and after swelling with water, the formation pore throat can be blocked. As the injection time continues to increase, the nanometer-scale plugging agent continues to hydrate and expand, and the final expansion system can reach about 100 times the initial volume, thereby blocking the formation pore throat, large pores or high permeability layers, improving the production profile, and forming a dynamic accumulation zone to block the end matrix micropores. At the same time, after the measure, as the injected water advances, the swept volume can be expanded, more residual oil can be driven out, and the oil well recovery rate can be improved.

[0054] Embodiment 1:

[0055] First, 30 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkylsulfonic acetamide and alkyl succinate sulfonate in equal weight ratios are added to 5 parts by weight of white oil, and the mixture is stirred evenly. Then, 10 parts by weight of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios is added to prepare an oil phase.

[0056] Then, 20 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone and ethylenediaminetetraacetic acid in equal weight ratios were weighed and dissolved in 20 parts of deionized water, and then 0.2 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 2 parts by weight of rhamnolipid and 2 parts by weight of phosphatidylethanolamine were added in sequence, and the mixture was mixed and stirred evenly to prepare an aqueous phase;

[0057] Then, the oil phase was placed in a reaction kettle, and the solution was stirred evenly with a magnetic stirring needle, and then the water phase was slowly added for emulsification, with stirring during the addition, and the emulsification time was 0.5 hours;

[0058] Then, after the emulsification was completed, the reactor was heated to 30°C and nitrogen was introduced for 0.5 hours to deoxygenate.

[0059] After the temperature was raised to 60° C., 0.02 parts by weight of azobisisobutyronitrile initiator was added to initiate the polymerization reaction, and the temperature was kept for 3 hours.

[0060] Finally, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation. Specifically, after the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a speed of 8000 rpm for 15 minutes.

[0061] like Figure 2 As shown, the original size of the prepared nanoscale water plugging agent micelle is 302 nm.

[0062] The test results are shown in Table 1.

[0063] Table 1 Test results of nanoscale water plugging agent in Example 1

[0064] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 30.2 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.85-1.1 1.02 4 Original size of micelle (nm) 300±20 302

[0065] Embodiment 2:

[0066] First, 40 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide and alkyl succinate sulfonate in equal weight ratios are added to 8 parts by weight of white oil, and the mixture is stirred evenly. Then, 14 parts by weight of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios is added to prepare an oil phase.

[0067] Then, 26 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in equal weight ratios were weighed and dissolved in 26 parts of deionized water, and then 0.3 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 3 parts by weight of rhamnolipid, and 3 parts by weight of phosphatidylethanolamine were added in sequence, mixed and stirred evenly to prepare an aqueous phase;

[0068] Then, the oil phase was placed in a reaction kettle, and after the solution was stirred evenly with a magnetic stirring needle, the water phase was slowly added for emulsification, stirring while adding, and the emulsification time was 1 hour;

[0069] Then, after the emulsification was completed, the reactor was heated to 30°C and nitrogen was introduced for 1 hour to deoxygenate.

[0070] After the temperature was raised to 60° C., 0.02 parts by weight of azobisisoheptanenitrile initiator was added to initiate the polymerization reaction, and the temperature was kept for 3 hours.

[0071] Finally, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation. Specifically, after the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a speed of 6000 rpm for 10 minutes.

[0072] The original size of the prepared nanoscale water plugging agent micelle is 314 nm.

[0073] The test results are shown in Table 2.

[0074] Table 2 Test results of nanoscale water plugging agent in Example 2

[0075] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 35.8 3 <![CDATA[Density, g / cm 3 (at 25°C)]]> 0.85-1.1 1.06 4 Original size of micelle (nm) 300±20 314

[0076] Embodiment 3:

[0077] First, 35 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide and alkyl succinate sulfonate in equal weight ratios are added to 6 parts of white oil, and the mixture is stirred evenly. Then, 12 parts of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios are added to prepare an oil phase.

[0078] Then, 22 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in equal weight ratios were weighed and dissolved in 22 parts of deionized water, and then 0.25 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 2.5 parts by weight of rhamnolipid, and 2.5 parts by weight of phosphatidylethanolamine were added in sequence, and the mixture was mixed and stirred evenly to prepare an aqueous phase;

[0079] Then, the oil phase was placed in a reaction kettle, and the solution was stirred evenly with a magnetic stirring needle, and then the water phase was slowly added for emulsification, with stirring during the addition, and the emulsification time was 0.75 hours;

[0080] Then, after the emulsification was completed, the reactor was heated to 30°C and nitrogen was introduced for 0.5 hours to deoxygenate.

[0081] After the temperature was raised to 60° C., 0.025 parts by weight of an initiator consisting of azobisisobutyronitrile and azobisisoheptanenitrile in an equal volume ratio was added to initiate a polymerization reaction, and the temperature was kept for 2.5 hours.

[0082] Finally, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation. Step 6 is specifically as follows: after the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a speed of 7000 rpm for 12 minutes.

[0083] The original size of the prepared nanoscale water plugging agent micelle is 308nm.

[0084] The test results are shown in Table 3.

[0085] Table 3 Test results of nanoscale water plugging agent in Example 3

[0086] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 31.6 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.85-1.1 1.03 4 Original size of micelle (nm) 300±20 308

[0087] Embodiment 4:

[0088] First, 36 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide and alkyl succinate sulfonate in equal weight ratios are added to 7 parts by weight of white oil, and the mixture is stirred evenly. Then, 13 parts by weight of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios is added to prepare an oil phase.

[0089] Then, 23 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in equal weight ratios were weighed and dissolved in 23 parts of deionized water, and then 0.25 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 2.5 parts by weight of rhamnolipid, and 2.5 parts by weight of phosphatidylethanolamine were added in sequence, and the mixture was mixed and stirred evenly to prepare an aqueous phase;

[0090] Then, the oil phase was placed in a reaction kettle, and the solution was stirred evenly with a magnetic stirring needle, and then the water phase was slowly added for emulsification, with stirring during the addition, and the emulsification time was 0.75 hours;

[0091] Then, after the emulsification was completed, the reactor was heated to 30°C and nitrogen was introduced for 0.75 hours to remove oxygen.

[0092] After the temperature was raised to 60° C., 0.025 parts by weight of azobisisoheptanenitrile initiator was added to initiate the polymerization reaction, and the temperature was kept for 2.5 hours.

[0093] Finally, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation. Specifically, after the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a speed of 6500 rpm for 15 minutes.

[0094] The original size of the prepared nanoscale water plugging agent micelle is 309 nm.

[0095] The test results are shown in Table 4.

[0096] Table 4 Test results of nanoscale water plugging agent in Example 4

[0097] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 33.5 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.85-1.1 1.05 4 Original size of micelle (nm) 300±20 309

Claims

1. Nano-scale water plugging agent, characterized in that: The invention comprises the following components in parts by weight:

2. The nanoscale water plugging agent according to claim 1, characterized in that: The comonomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, alkylsulfonic acetamide and alkyl succinate sulfonate mixed in any proportion.

3. The nanoscale water plugging agent according to claim 1, characterized in that: The composite emulsifier is composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether mixed in any ratio.

4. The nanoscale water plugging agent according to claim 1, characterized in that: The composite monomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N-vinyl pyrrolidone and ethylenediaminetetraacetic acid mixed in any proportion.

5. The nanoscale water plugging agent according to claim 1, characterized in that: The cross-linking agent is N,N'-methylenebisacrylamide.

6. The nanoscale water plugging agent according to claim 1, characterized in that: The initiator is azobisisobutyronitrile or azobisisoheptanitrile, or a mixture of azobisisobutyronitrile and azobisisoheptanitrile, and the volume ratio of the two in the mixture is 1:

1.

7. The method for preparing the nanoscale water plugging agent according to claim 1, characterized in that: The specific steps include: Step 1, preparing oil phase; Step 2, preparing the aqueous phase; Step 3, placing the oil phase in a reaction kettle, stirring the solution evenly with a magnetic stirring needle, and then slowly adding the water phase for emulsification while stirring. The emulsification time is 0.5 hour to 1 hour; Step 4: After emulsification is completed, the temperature is raised and nitrogen is introduced for 0.5 hour to 1 hour for deoxygenation; Step 5, heating again, adding azobisisobutyronitrile or azobisisoheptanenitrile initiator to initiate polymerization reaction, and keeping warm for 2 hours to 3 hours; Step 6: After cooling to room temperature, nanometer-scale water plugging agent is obtained by centrifugation.

8. The method for preparing the nanoscale water plugging agent according to claim 1, characterized in that: Step 1 is as follows: Add a copolymer monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide and alkyl succinate sulfonate in any ratio into white oil, stir evenly, and then add a composite emulsifier mixed with sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio to prepare an oil phase.

9. The method for preparing the nanoscale water plugging agent according to claim 1, characterized in that: Step 2 is as follows: A composite monomer of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone and ethylenediaminetetraacetic acid mixed in any ratio is weighed and dissolved in deionized water, and then a cross-linking agent of N,N'-methylenebisacrylamide, rhamnolipid and phosphatidylethanolamine are added in sequence, and the mixture is mixed and stirred evenly to prepare an aqueous phase.

10. The method for preparing the nanoscale water plugging agent according to claim 1, characterized in that: In step 4, the temperature raising treatment is specifically as follows: using a reaction kettle to raise the temperature to 30° C.; In step 5, after the temperature is raised to 60° C. again, azobisisobutyronitrile or azobisisoheptanenitrile initiator is added to initiate a polymerization reaction; Step 6 specifically comprises: after cooling to room temperature, centrifuging the liquid obtained in step 5 after the polymerization reaction with anhydrous ethanol at a rotation speed of 6000 rpm-8000 rpm for 10 minutes-15 minutes.

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