Polymer microsphere profile control and water plugging agent as well as preparation method and application thereof

Abstract

The invention provides a polymer microsphere profile control water shutoff agent and a preparation method and application thereof, and the preparation method of the polymer microsphere profile control water shutoff agent comprises the following steps: dispersing molybdenum disulfide nanosheets in water, and adding a template carrier to form a Pickering emulsion; carrying out first polymerization reaction on the Pickering emulsion, a polymer monomer A, an RAFT (Reversible Addition-Fragmentation Chain Transfer) reagent and an initiator to obtain a hydrophilic polymer graft copolymerization nanosheet; carrying out second polymerization reaction on the hydrophilic polymer graft copolymerization nanosheet, a polymer monomer B and an initiator in a solvent to obtain a unilateral polymer modified nanosheet; and removing the template carrier, and carrying out third reaction on the unilateral polymer modified nanosheet and amino acid in water to obtain the polymer microsphere profile control water plugging agent. The polymer microsphere profile control and water plugging agent prepared by the invention is temperature-resistant and salt-resistant, can enter a deep stratum and is uniformly distributed in a high-permeability layer, the profile control and water plugging effects are good, and the recovery efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield recovery, and in particular to a polymer microsphere profile control and water plugging agent, and a preparation method and application thereof. Background Art

[0002] In the process of reservoir development, as the development time increases, the formation energy is lost, resulting in a decrease in crude oil recovery efficiency. In order to improve the recovery efficiency of formation crude oil, most oil fields use water injection development to replenish energy for the formation and achieve high and stable production of the oil field. However, due to the heterogeneity of the formation, this water usually preferentially enters the high permeability layer with low seepage resistance, while there is still a large amount of residual oil in the low permeability layer waiting for further development, which leads to premature water in the oil well, a rapid increase in water content in the production fluid and a low recovery rate. Therefore, in order to control the output of water, reduce the water content, and start the remaining oil in the low permeability layer or increase the development of the low permeability layer, relevant measures must be taken to selectively block the high permeability layer and adjust the uneven water absorption profile of the formation so that more water can penetrate into the low permeability layer, thereby driving more oil.

[0003] There are two major profile control and water plugging methods in existing oil fields, namely mechanical profile control and water plugging and chemical profile control and water plugging. Compared with the limitations of mechanical profile control and water plugging, chemical profile control and water plugging is the most widely used and widely used profile control and water plugging technology in oil fields.

[0004] Polymer microspheres are a kind of chemical profile control and water plugging agent that has been widely studied and applied in recent years. They are mainly formed by cross-linking of hydrophilic groups. The size of polymer microspheres is very small and can enter the formation smoothly with the solution. The microspheres are continuously hydrated and expanded in the formation until they expand to the maximum volume. They rely on bridging to plug the pores and throats of the formation to achieve the redirection of injected water. Ma Guoyan et al. (Ma Guoyan, Shen Yiding, Gao Ruimin et al. Research on the application performance of nano-micron acrylamide microsphere profile control agent [J]. Modern Chemical Industry, 2016, 36 (12): 94-96 + 98. DOI: 10.16606 / j.cnki.issn0253-4320.2016.12.023.) reported a temperature-resistant and salt-resistant amphiphilic polyacrylamide microsphere. After the microspheres are fully swollen in simulated water at 70°C, their particle size can expand from 50nm to 634nm, and the water absorption expansion multiple exceeds 2000. However, due to the excessive pursuit of maximizing the expansion performance of microspheres, the swollen microspheres are easily sheared and broken during their migration to deep depths, which seriously affects the profile control effect of the microspheres.

[0005] Liu Yuli (Liu Yuli. Research on heat-resistant and salt-resistant composite profile control system [D]. Yangtze University, 2015.) added acrylic acid to acrylamide and toughened it with bentonite to obtain a heat-resistant and salt-resistant pre-crosslinked polymer microsphere profile control agent. The particles can expand 100 times in clear water, but in high-mineralization water (16×10 4 mg / L), the expansion rate is only 15.8 times. It can be seen that conventional polymer microspheres have poor temperature and salt resistance. They will harden under high temperature and high mineralization formation conditions, resulting in poor deformability and inability to adjust the profile of deep formations.

[0006] Therefore, the main disadvantages of polymer microspheres can be summarized as follows: (1) The water absorption and swelling effect of polymer microspheres deteriorates under high temperature or high salt conditions, and the polymer is prone to chain breakage and degradation; (2) During the injection process into the formation, it absorbs water and swells and cannot reach deep into the formation; (3) Due to the limited effect of water absorption and swelling, polymer microspheres with a small initial particle size are less likely to effectively block the pore throat than polymer microspheres with a larger initial particle size, and polymer microspheres with a small initial particle size are more likely to enter the low permeability layer and cause damage to it.

[0007] Therefore, developing a new type of polymer microsphere that can enter deep strata, be evenly distributed in high-permeability layers, and be resistant to temperature and salt is a practical problem that needs to be solved urgently. Summary of the invention

[0008] In order to solve the above technical problems, the purpose of the present invention is to provide a polymer microsphere profile control and water plugging agent and a preparation method and application thereof.

[0009] In order to achieve the above object, the present invention provides a method for preparing a polymer microsphere profile control and water plugging agent, which comprises the following steps:

[0010] S1: Disperse MoS2 nanosheets in water, add template carrier, heat and stir to form Pickering emulsion;

[0011] S2: subjecting the Pickering emulsion, polymer monomer A, RAFT agent and initiator to a first polymerization reaction in a solvent to obtain a hydrophilic polymer graft copolymer nanosheet;

[0012] S3: subjecting the hydrophilic polymer graft copolymer nanosheet, polymer monomer B, and initiator to a second polymerization reaction in a solvent to obtain a single-side polymer modified nanosheet;

[0013] S4: removing the template carrier in the single-sided polymer-modified nanosheet, and then performing a third reaction between the single-sided polymer-modified nanosheet and an amino acid in water to obtain the polymer microsphere profile control and water plugging agent;

[0014] Wherein, the mass ratio of molybdenum disulfide nanosheets to polymer monomer A, polymer monomer B and amino acid is 1:30-100:30-100:5-15.

[0015] According to a specific embodiment of the present invention, more preferably, the mass ratio of molybdenum disulfide nanosheets to polymer monomer A is 1:50-100; the mass ratio of molybdenum disulfide nanosheets to polymer monomer B is 1:50-100.

[0016] The polymer microsphere profile control and water plugging agent of the present invention uses molybdenum disulfide nanosheets as the core structure, and the polymer formed by polymer monomer A and polymer monomer B and amino acids modify the surface of the nanosheets, thereby improving the rigidity of the polymer microspheres as a whole, increasing the tolerance to temperature and salinity, being heat-resistant and salt-resistant, and being able to enter deep formations and be evenly distributed in high-permeability layers, having good profile control and water plugging effects, and improving the recovery rate. The present invention connects amino acids and block copolymers to the surface of molybdenum disulfide nanosheets to form a new type of polymer microsphere profile control and water plugging agent, which has a slow expansion speed, can enter deep formations, and has a strong force with the rock surface, and reduces the permeability of the high-permeability layer by reducing the radius of the high-permeability pore throat; finally, due to the composite nanomaterials, the sensitivity to temperature and salinity is reduced, and it has the characteristics of heat-resistant and salt-resistant.

[0017] At present, the improvement of polymer microspheres is concentrated in two directions: one is to increase salt-resistant monomers and temperature-resistant monomers to strengthen the rigidity of polymer chains, and the other is to prepare rigid microspheres by compounding with nanomaterials. However, polymer microspheres still have obvious defects. On the one hand, they cannot enter the deep low layers, and on the other hand, after blocking the high permeability layer near the wellbore, the fluid will bypass and reduce the profile control effect.

[0018] The profile control and water plugging agent prepared by the present invention improves the wettability of the hyperpermeable layer by introducing amino acids, increases the seepage resistance of the hyperpermeable layer, and reduces the pore throat radius of the hyperpermeable layer. Different from conventional polymer microspheres that bridge and plug pore throats, the polymer microsphere profile control and water plugging agent of the present invention is uniformly adsorbed on the surface of the pore throat to achieve the effect of reducing the diameter, which not only allows the polymer microspheres to enter the deep formation, but also can uniformly modify the hyperpermeable layer and reduce the occurrence of bypass flow.

[0019] According to a specific embodiment of the present invention, preferably, the polymer monomer A is a hydrophilic polymer monomer, and the polymer monomer B is a hydrophobic polymer monomer.

[0020] According to a specific embodiment of the present invention, preferably, the polymer monomer A is selected from one or a combination of two or more of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.

[0021] According to a specific embodiment of the present invention, preferably, the polymer monomer B is selected from one or a combination of two or more of styrene, 4-vinylpyridine and vinyltriethoxysilane.

[0022] According to a specific embodiment of the present invention, preferably, the molybdenum disulfide nanosheets are selected from molybdenum disulfide nanosheets with a 1T crystal form, and the size of the nanosheets is 80-150 nm.

[0023] According to a specific embodiment of the present invention, preferably, the mass ratio of the molybdenum disulfide nanosheets to the template carrier is 1:10-12.

[0024] According to a specific embodiment of the present invention, preferably, the initiator is azobisisobutyronitrile (AIBN).

[0025] According to a specific embodiment of the present invention, preferably, the RAFT agent is S, S-dibenzyl trithiocarbonate or 2-[(dodecylsulfanyl)thioacyl]-sulfanyl propionic acid. RAFT is the abbreviation of Reversible Addition-Fragmentation Chain Transfer Polymerization, which is a kind of active / controlled radical polymerization (CRP). It can be understood that RAFT is a polymer method. The RAFT agent described in the present invention is a small molecule organic substance that links a hydrophilic polymer and a hydrophobic polymer.

[0026] According to a specific embodiment of the present invention, preferably, in S2, the temperature of the first polymerization reaction is 60-80°C, and the time is 10-15h.

[0027] According to a specific embodiment of the present invention, preferably, in S2, the amount of the initiator added is 1-1.5% of the mass of the polymer monomer A, and the amount of the RAFT agent added is 3-5% of the mass of the polymer monomer A.

[0028] According to a specific embodiment of the present invention, preferably, in S3, the temperature of the second polymerization reaction is 60-80° C., and the reaction time is 10-15 h.

[0029] According to a specific embodiment of the present invention, preferably, in S3, the amount of the initiator added is 0.5-1% of the mass of the polymer monomer B.

[0030] According to a specific embodiment of the present invention, preferably, the solvent used in S2 and S3 is ethanol.

[0031] According to a specific embodiment of the present invention, preferably, the template carrier is paraffin; the mass ratio of molybdenum disulfide nanosheets, paraffin and water in S1 is 1:10-12:100-110.

[0032] According to a specific embodiment of the present invention, preferably, the heating temperature in S1 is 60-80° C., and the added template carrier is melted paraffin.

[0033] According to a specific embodiment of the present invention, preferably, the stirring speed in S1 is 5000-8000 rpm, and the stirring time is 3-5 min.

[0034] According to a specific embodiment of the present invention, preferably, the method for removing the template carrier in S4 is: dispersing the hydrophilic polymer graft copolymer nanosheets in cyclohexane, and then washing with cyclohexane and deionized water.

[0035] According to a specific embodiment of the present invention, preferably, in S4, the temperature of the third reaction is 30-50° C., and the reaction time is 20-40 h.

[0036] According to a specific embodiment of the present invention, preferably, in S4, the amino acid is selected from one or a combination of two or more of glycine, alanine, serine and cysteine.

[0037] According to a specific embodiment of the present invention, preferably, the method for preparing the polymer microsphere profile control and water plugging agent further comprises: using the product of any step S1-S4 as a detergent; the detergent is an ethanol aqueous solution with a concentration of 10-20% (ethanol mass fraction).

[0038] According to a specific embodiment of the present invention, the preparation method of the above-mentioned polymer microsphere profile control and water plugging agent comprises the following steps:

[0039] S1: ultrasonically dispersing molybdenum disulfide nanosheets in water to obtain a molybdenum disulfide aqueous solution, then raising the temperature to 60-80°C, and then adding melted paraffin; then stirring in a high-speed stirrer at 5000-8000 rpm for 3-5 minutes to form a Pickering emulsion, and then cooling it statically; after cooling to below 25°C, centrifugally washing with a 10-20% ethanol aqueous solution and taking the upper white emulsion;

[0040] S2: white emulsion, ethanol, polymer monomer A and RAFT agent are mixed in a beaker, and then an initiator is added, and the reaction is carried out at 60-80° C. for 10-15 hours. After the reaction is completed, the product is washed with a 10-20% ethanol aqueous solution to obtain hydrophilic polymer grafted molybdenum disulfide nanosheets;

[0041] S3: The hydrophilic polymer grafted molybdenum disulfide nanosheets obtained in S2, ethanol, initiator AIBN and polymer monomer B are mixed in a beaker, and reacted at 60-80° C. for 10-15 hours. After the reaction, the product is washed with a 10-20% ethanol aqueous solution to obtain a single-side polymer-modified molybdenum disulfide nanosheet;

[0042] S4: Disperse the unilateral polymer-modified molybdenum disulfide nanosheet emulsion in cyclohexane, wash with cyclohexane and deionized water, collect and precipitate the unilateral polymer-modified molybdenum disulfide nanosheet; disperse the unilateral polymer-modified molybdenum disulfide nanosheet in an aqueous solution of amino acids, stir at 30-50°C for 20-40h, and after the reaction is completed, wash the product with a 10-20% ethanol aqueous solution to obtain a polymer microsphere profile control and water plugging agent.

[0043] The present invention also provides a polymer microsphere profile control and water plugging agent obtained by the preparation method of the polymer microsphere profile control and water plugging agent.

[0044] According to a specific embodiment of the present invention, the above-mentioned polymer microsphere profile control and water plugging agent includes molybdenum disulfide nanosheets, one side of the molybdenum disulfide nanosheets is grafted with a hydrophilic polymer, the other end of the hydrophilic polymer is connected to a modified polymer, and the other side of the molybdenum disulfide nanosheets is grafted with amino acids.

[0045] The present invention also provides an application of the polymer microsphere profile control and water plugging agent in profile control and water plugging.

[0046] In the above application, preferably, the polymer microsphere profile control and water plugging agent is used at a concentration of 1000-5000 mg / L.

[0047] The technical solution provided by the present invention has the following beneficial effects:

[0048] (1) In order to increase the interaction between the nanomaterial and the rock surface and achieve uniform adsorption in the pores, the present invention selects the sheet-like nanomaterial molybdenum disulfide as the core, and modifies different functional groups on both sides of the molybdenum disulfide so that the two sides have different functionalities. Since the molybdenum disulfide nanosheet is used as the core structure, the surface is modified with polymer (polymer monomer A + polymer monomer B) and small molecule organic matter (amino acid), the overall rigidity of the polymer microsphere is improved, the tolerance to temperature and mineralization is increased, and the temperature and salt resistance of the polymer microsphere is enhanced.

[0049] (2) The wettability of the two sides of the novel polymer microspheres provided by the present invention is different. The side modified with small molecules (amino acids) is mainly strongly hydrophilic. By increasing the number of polar functional groups, the interaction between the polymer microspheres and the rock surface is increased, so that the polymer microspheres are uniformly adsorbed on the rock surface. In addition, molybdenum disulfide is a flaky nanomaterial with a larger contact area than that of a spherical nanomaterial, highlighting the advantage of the flaky nanomaterial as the core.

[0050] (3) The present invention also uses block polymers to modify the other side of molybdenum disulfide. The block polymer is formed by connecting a hydrophilic polymer (polymer monomer A) and a lipophilic polymer (polymer monomer B). The hydrophilic polymer is connected to the surface of molybdenum disulfide, and the hydrophobic end extends outward. Conventional polymer microspheres are based on hydrophilic polymers. Some hydrophobic monomers or salt-resistant monomers are added to the monomers to increase the heat and salt resistance of the polymer. However, the addition of a small amount of monomers will not have a decisive effect on the structure of the overall polymer. Therefore, the block polymers used in the present invention are stronger than conventional polymers.

[0051] (4) The profile control mechanism of the polymer microsphere profile control and water plugging agent of the present invention is that after the polymer microsphere enters the formation along with the fluid, the strongly hydrophilic side of the grafted amino acid will generate a strong van der Waals force with the rock surface, thereby being adsorbed on the rock surface, so that one side of the grafted polymer will be exposed. Due to the hydrophobicity of the polymer, the wettability of the rock surface changes from hydrophilic to hydrophobic, and the capillary force changes from a driving force to a resistance. At the same time, there is a hydrophilic polymer in the block polymer, which will gradually absorb water and expand over time, further reducing the pore throat radius, thereby reducing the water phase permeability of the deep layer.

[0052] (5) If the polymer microsphere profile control and water plugging agent of the present invention encounters an oil-bearing layer, the structure of the polymer microsphere is similar to that of a surfactant and has amphiphilicity. The hydrophobic end (polymer) on one side of the nanosheet interacts with crude oil, and the hydrophilic end (formed by amino acids) on the other side interacts with water to form a stable emulsion, thereby achieving the purpose of emulsified oil displacement. This also prevents the polymer microsphere from entering the low permeability layer before expansion and causing damage to the low permeability layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic diagram of the preparation method of the polymer microsphere profile control and water plugging agent of the present invention;

[0054] Figure 2 The water absorption rate of the polymer microsphere profile control and water plugging agent prepared in Example 1;

[0055] Figure 3 The particle size distribution of the polymer microsphere profile control and water plugging agent prepared in Example 1 (without water absorption and swelling);

[0056] Figure 4 This is a microscope image of the polymer microsphere profile control and water plugging agent prepared in Example 1 after being placed at 100° C. for 7 days. DETAILED DESCRIPTION

[0057] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0058] Unless otherwise specified, the raw materials and reagents in the following examples are all commercially available products, and the purity is analytical purity.

[0059] Example 1

[0060] This example prepares a polymer microsphere profile control and water plugging agent, such as Figure 1 As shown, the preparation method thereof comprises the following steps:

[0061] (1) 1 g of 1T crystalline molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution, and then the temperature was raised to 80° C., followed by adding 10 g of melted paraffin wax; then the mixture was stirred in a high-speed stirrer at 8000 rpm for 3 min to form a Pickering emulsion, and then cooled statically; after cooling to below 25° C., the mixture was centrifugally washed with a 20% ethanol aqueous solution, and the upper white emulsion was taken;

[0062] (2) the upper white emulsion obtained in step (1), 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylsulfanyl)thioacyl]-sulfanylpropionic acid reagent were mixed in a beaker, and then 0.75 g of AIBN was added, and the mixture was reacted at 60° C. for 10 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain hydrophilic polymer grafted molybdenum disulfide nanosheets;

[0063] (3) then mixing the hydrophilic polymer grafted molybdenum disulfide nanosheets obtained in step (2), ethanol, 0.5 g AIBN and 50 g styrene in a beaker, reacting at 60° C. for 12 h, and washing the product with a 20% ethanol aqueous solution after the reaction to obtain a single-side polymer-modified molybdenum disulfide nanosheet emulsion;

[0064] (4) dispersing the unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) in cyclohexane, washing with cyclohexane and deionized water, collecting and precipitating the unilateral polymer-modified molybdenum disulfide nanosheet; dispersing the unilateral polymer-modified molybdenum disulfide nanosheet in an aqueous solution, adding 15 g of serine, stirring at 30° C. for 20 h, and washing the product with a 20% ethanol aqueous solution after the reaction is completed to obtain the polymer microsphere profile control and water plugging agent.

[0065] In order to test the salt resistance of the polymer microsphere profile control and water plugging agent (polymer microsphere) prepared in this example, 0.1 g of the synthesized polymer microsphere was dispersed in 6.0 mL of 1 mol / L sodium chloride solution, and the water absorption rate of the polymer microsphere was measured at different times. The experimental results are as follows: Figure 2 As shown, it can be seen that the polymer microsphere profile control and water plugging agent has high salt resistance.

[0066] This example also measured the particle size distribution of the prepared polymer microsphere profile control and water plugging agent under unexpanded conditions. The results are as follows: Figure 3 As shown, the particle size of the prepared polymer microspheres is mainly distributed in the range of 160-180 nm, among which the microspheres with a particle size of 163 nm account for 3%, the microspheres with a particle size of 177 nm account for 32%, the microspheres with a particle size of 180 nm account for 43%, and the microspheres with a particle size of 183 nm account for 22%.

[0067] The present invention also measured that the particle size of the polymer microspheres of Example 1 was micrometer level after being placed at 100°C for 7 days. Figure 4 As shown, this property enables the polymer microsphere profile control and water plugging agent to enter deeper formations, achieve profile control, and improve recovery.

[0068] Example 2

[0069] This embodiment provides a polymer microsphere profile control and water plugging agent, and the preparation method thereof comprises the following steps:

[0070] (1) 1 g of 1T crystalline molybdenum disulfide (size 80 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution, and then the temperature was raised to 80° C., and then 12 g of melted paraffin was added; then the mixture was stirred in a high-speed stirrer at 8000 rpm for 3 min to form a Pickering emulsion, and then cooled statically; after cooling to below 25° C., the mixture was centrifuged and washed with a 20% ethanol aqueous solution, and the upper white emulsion was taken;

[0071] (2) The upper white emulsion obtained in step (1), 300 mL of ethanol, 100 g of acrylamide and 5 g of S,S-dibenzyl trithiocarbonate reagent were mixed in a beaker, and then 1.5 g of AIBN was added, and the mixture was reacted at 60° C. for 15 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain hydrophilic polymer grafted molybdenum disulfide nanosheets;

[0072] (3) then mixing the hydrophilic polymer grafted molybdenum disulfide nanosheets obtained in step (2), ethanol, 1 g of AIBN and 100 g of vinyltriethoxysilane in a beaker, reacting at 60° C. for 15 h, and washing the product with a 20% ethanol aqueous solution after the reaction to obtain a single-side polymer-modified molybdenum disulfide nanosheet emulsion;

[0073] (4) dispersing the unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) in cyclohexane, washing with cyclohexane and deionized water, collecting and precipitating the unilateral polymer-modified molybdenum disulfide nanosheet; dispersing the unilateral polymer-modified molybdenum disulfide nanosheet in an aqueous solution, adding 10 g of cysteine, stirring at 30° C. for 30 h, and washing the product with a 20% ethanol aqueous solution after the reaction is completed to obtain the polymer microsphere profile control and water plugging agent.

[0074] Example 3

[0075] This embodiment provides a polymer microsphere profile control and water plugging agent, comprising the following steps:

[0076] (1) 1 g of 1T crystal form molybdenum disulfide (size 100 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution, and then the temperature was raised to 80° C., followed by adding 10 g of melted paraffin wax; then stirred in a high-speed stirrer at 8000 rpm for 3 min to form a Pickering emulsion, and then cooled statically. After cooling to below 25° C., the upper white emulsion was washed by centrifugation with a 20% ethanol aqueous solution and then taken.

[0077] (2) The upper white emulsion obtained in step (1), 300 mL of ethanol, 50 g of acrylamide, 50 g of acrylic acid and 7.5 g of 2-[(dodecylsulfanyl)thioacyl]-sulfanylpropionic acid reagent were mixed in a beaker, and then 2.25 g of AIBN was added. The mixture was reacted at 60° C. for 15 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain hydrophilic polymer grafted molybdenum disulfide nanosheets.

[0078] (3) then mixing the hydrophilic polymer grafted molybdenum disulfide nanosheets obtained in step (2), ethanol, 1 g of AIBN and 100 g of styrene in a beaker, reacting at 60° C. for 15 h, and washing the product with a 20% ethanol aqueous solution after the reaction to obtain a unilateral polymer-modified molybdenum disulfide nanosheet emulsion;

[0079] (4) dispersing the unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) in cyclohexane, washing with cyclohexane and deionized water, collecting and precipitating the unilateral polymer-modified molybdenum disulfide nanosheet; dispersing the unilateral polymer-modified molybdenum disulfide nanosheet in an aqueous solution, adding 10 g of glycine, stirring at 30° C. for 20 h, and washing the product with a 20% ethanol aqueous solution after the reaction is completed to obtain the polymer microsphere profile control and water plugging agent.

[0080] Example 4

[0081] In this embodiment, a polymer microsphere profile control and water plugging agent is prepared, and the preparation method thereof comprises the following steps:

[0082] (1) 1 g of 1T crystalline molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution, and then the temperature was raised to 80° C., followed by adding 10 g of melted paraffin wax; then the mixture was stirred in a high-speed stirrer at 5000 rpm for 5 min to form a Pickering emulsion, and then cooled statically; after cooling to below 25° C., the mixture was centrifugally washed with a 20% ethanol aqueous solution, and the upper white emulsion was taken;

[0083] (2) The upper white emulsion obtained in step (1), 200 mL of ethanol, 20 g of acrylamide, 10 g of 2-acrylamido-2-methylpropanesulfonic acid and 2.5 g of 2-[(dodecylsulfanyl)thioacyl]-sulfanylpropionic acid reagent were mixed in a beaker, and then 0.75 g of AIBN was added, and the mixture was reacted at 80° C. for 10 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain hydrophilic polymer grafted copolymerized molybdenum disulfide nanosheets;

[0084] (3) then mixing the hydrophilic polymer grafted molybdenum disulfide nanosheets obtained in step (2), ethanol, 0.5 g AIBN, 20 g styrene and 10 g 4-vinylpyridine in a beaker, reacting at 80° C. for 12 h, and washing the product with a 20% ethanol aqueous solution after the reaction to obtain a unilateral polymer-modified molybdenum disulfide nanosheet emulsion;

[0085] (4) dispersing the unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) in cyclohexane, washing with cyclohexane and deionized water, collecting and precipitating the unilateral polymer-modified molybdenum disulfide nanosheet; dispersing the unilateral polymer-modified molybdenum disulfide nanosheet in an aqueous solution, adding 5 g of serine, stirring at 30° C. for 20 h, and washing the product with a 20% ethanol aqueous solution after the reaction is completed to obtain the polymer microsphere profile control and water plugging agent.

[0086] Example 5

[0087] In this embodiment, a polymer microsphere profile control and water plugging agent is prepared, and the preparation method thereof comprises the following steps:

[0088] (1) 1 g of 1T crystalline molybdenum disulfide (size 80 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution, and then the temperature was raised to 80° C., followed by adding 10 g of melted paraffin wax; then the mixture was stirred at 5000 rpm in a high-speed stirrer for 3 min to form a Pickering emulsion, and then cooled statically; after cooling to below 25° C., the mixture was centrifugally washed with a 20% ethanol aqueous solution, and the upper white emulsion was taken;

[0089] (2) The upper white emulsion obtained in step (1), 200 mL of ethanol, 40 g of acrylamide and 2.5 g of 2-[(dodecylsulfanyl)thioacyl]-sulfanylpropionic acid reagent were mixed in a beaker, and then 0.4 g of AIBN was added, and the mixture was reacted at 80° C. for 13 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain hydrophilic polymer grafted molybdenum disulfide nanosheets;

[0090] (3) then mixing the hydrophilic polymer grafted molybdenum disulfide nanosheets obtained in step (2), ethanol, 0.2 g AIBN and 40 g styrene in a beaker, reacting at 80° C. for 10 h, and washing the product with a 20% ethanol aqueous solution after the reaction to obtain a single-side polymer-modified molybdenum disulfide nanosheet emulsion;

[0091] (4) dispersing the unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) in cyclohexane, washing with cyclohexane and deionized water, collecting and precipitating the unilateral polymer-modified molybdenum disulfide nanosheet; dispersing the unilateral polymer-modified molybdenum disulfide nanosheet in an aqueous solution, adding 5 g of glycine, stirring at 30° C. for 20 h, and washing the product with a 20% ethanol aqueous solution after the reaction is completed to obtain the polymer microsphere profile control and water plugging agent.

[0092] Comparative Example 1

[0093] This comparative example provides a profile control and water plugging agent, and its preparation method is as follows:

[0094] (1) 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylsulfanyl)thioacyl]-sulfanylpropionic acid reagent were mixed in a beaker, and then 0.75 g of AIBN was added. The mixture was reacted at 60° C. for 10 h. After the reaction was completed, the product was washed with a 20% ethanol aqueous solution to obtain a hydrophilic polymer.

[0095] (2) The product from the previous step, ethanol, 0.5 g AIBN and 50 g styrene were mixed in a beaker and reacted at 60° C. for 12 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain a block polymer, i.e., the profile control and water plugging agent of this embodiment.

[0096] Comparative Example 2

[0097] This comparative example provides a profile control and water plugging agent, and its preparation method is as follows:

[0098] (1) 1 g of 1T crystalline molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution, and then the temperature was raised to 80° C., followed by adding 10 g of melted paraffin wax; then the mixture was stirred in a high-speed stirrer at 8000 rpm for 3 min to form a Pickering emulsion, and then cooled statically; after cooling to below 25° C., the mixture was centrifugally washed with a 20% ethanol aqueous solution, and the upper white emulsion was taken;

[0099] (2) The upper white emulsion, 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylsulfanyl)thioacyl]-sulfanylpropionic acid reagent were mixed in a beaker, and then 0.75 g of AIBN was added, and the reaction was carried out at 60° C. for 10 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain a hydrophilic polymer grafted copolymerized molybdenum disulfide nanosheet;

[0100] (3) The product from the previous step, ethanol, 0.5 g AIBN and 50 g styrene were mixed in a beaker and reacted at 60° C. for 12 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain a single-side polymer-modified molybdenum disulfide nanosheet, i.e., the profile control and water plugging agent of this embodiment.

[0101] Comparative Example 3

[0102] This comparative example provides a profile control and water plugging agent, and its preparation method is as follows:

[0103] (1) 1 g of 1T crystalline molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution, and then the temperature was raised to 80° C., followed by adding 10 g of melted paraffin wax; then the mixture was stirred in a high-speed stirrer at 8000 rpm for 3 min to form a Pickering emulsion, and then cooled statically; after cooling to below 25° C., the mixture was centrifugally washed with a 20% ethanol aqueous solution, and the upper white emulsion was taken;

[0104] (2) The upper white emulsion, 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylsulfanyl)thioacyl]-sulfanylpropionic acid reagent were mixed in a beaker, and then 0.75 g of AIBN was added, and the reaction was carried out at 60° C. for 10 h. After the reaction, the product was washed with a 20% ethanol aqueous solution to obtain a hydrophilic polymer grafted copolymerized molybdenum disulfide nanosheet emulsion;

[0105] (3) dispersing the hydrophilic polymer grafted copolymerized molybdenum disulfide nanosheet emulsion in cyclohexane, then washing with cyclohexane and deionized water, collecting and precipitating the single-side polymer modified molybdenum disulfide nanosheet; dispersing the single-side polymer modified molybdenum disulfide nanosheet in aqueous solution, adding 15g of serine, stirring at 30°C for 20h, and washing the product with 20% ethanol aqueous solution after the reaction to obtain a profile control and water plugging agent.

[0106] Experimental Example 1

[0107] This experimental example is used to test the profile control and water plugging performance of the profile control and water plugging agents of the above embodiments and comparative examples.

[0108] The one-dimensional core displacement device was used to conduct an experimental study on the effect of microsphere flooding. The device consists of a horizontal flow pump, an intermediate container (for containing experimental fluids such as oil, water and displacement agent), and a core holder with a pressure measuring point. The experimental steps are as follows:

[0109] ① Preparation stage: Install pipelines and debug equipment, weigh the core dry weight in advance and prepare the experimental displacement agent;

[0110] ② Water saturation stage: Use a horizontal flow pump at a constant speed of 10 mL / min to complete the core water saturation operation, weigh the wet weight of the core and calculate the pore volume PV based on the mass difference before and after water saturation;

[0111] ③ Oil saturation stage: Use a horizontal flow pump at a constant speed of 10 mL / min to saturate the core with oil. During the process, the water volume is recorded and the oil saturation So is calculated;

[0112] ④ Water flooding stage: Use a horizontal flow pump to flood the water at a constant speed of 2 mL / min until the water cut reaches 98%, record the pressure change data, and calculate the numerical changes of water cut and recovery factor;

[0113] ⑤ Microsphere flooding stage: Use a horizontal flow pump at a constant speed of 0.3mL / min to perform 0.3PV microsphere displacement operation, record the pressure change data and calculate the water content value during the process, and let it stand for 1 day after injecting the microspheres;

[0114] ⑥ Subsequent water flooding stage: Use a horizontal flow pump at a constant speed of 2mL / min to perform 2PV water flooding operation on the core after the microspheres are injected and left to stand for 1 day, record the pressure change data, and calculate the water content value change and recovery factor increase.

[0115] The results are shown in Table 1.

[0116] Table 1 Performance test results of profile control and water plugging agent

[0117]

[0118] From the experimental results, the polymer microsphere profile control and water plugging agent of the embodiment of the present invention has a significant water plugging effect, and the recovery rate can generally be increased by more than 10%.

[0119] Compared with the embodiment, the comparative example 1 does not add molybdenum disulfide nanosheets, and the obtained block copolymer polymer is not easy to form a plug due to the self-assembly characteristics of the polymer. The comparative example 2 does not add amino acids, and only the molybdenum disulfide nanosheets modified by the unilateral polymer work. Due to the weak interaction with the rock surface, it is difficult to achieve the effect of adsorption and retention, and can only play the role of expansion and plugging. The comparative example 3 does not carry out block copolymerization, and only acrylamide (polymer monomer A) is homopolymerized. Its effect is similar to that of conventional water-blocking microspheres, mainly plugging the pore throat by water absorption and expansion. Since the wettability of the pore throat is not changed, its effect is poorer than that of the embodiment of the present invention.

Claims

1. A method for preparing a polymer microsphere profile control and water plugging agent, comprising the following steps: S1: Disperse MoS2 nanosheets in water, add template carrier, heat and stir to form Pickering emulsion; S2: subjecting the Pickering emulsion, polymer monomer A, RAFT agent and initiator to a first polymerization reaction in a solvent to obtain a hydrophilic polymer graft copolymer nanosheet; S3: subjecting the hydrophilic polymer graft copolymer nanosheet, polymer monomer B, and initiator to a second polymerization reaction in a solvent to obtain a single-side polymer modified nanosheet; S4: removing the template carrier in the single-sided polymer-modified nanosheet, and then performing a third reaction between the single-sided polymer-modified nanosheet and an amino acid in water to obtain the polymer microsphere profile control and water plugging agent; in, The mass ratio of molybdenum disulfide nanosheets to polymer monomer A, polymer monomer B and amino acid is 1:30-100:30-100:5-15.

2. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: The polymer monomer A is selected from one or a combination of two or more of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.

3. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: The polymer monomer B is selected from one or a combination of two or more of styrene, 4-vinylpyridine and vinyltriethoxysilane.

4. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: The molybdenum disulfide nanosheets are selected from molybdenum disulfide nanosheets with a 1T crystal form, and the size of the nanosheets is 80-150nm.

5. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: The mass ratio of the molybdenum disulfide nanosheets to the template carrier is 1:10-12.

6. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: The initiator is azobisisobutyronitrile.

7. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: The RAFT agent is S,S-dibenzyl trithiocarbonate or 2-[(dodecylsulfanyl)thioacyl]-sulfanyl propionic acid.

8. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: In S2, the temperature of the first polymerization reaction is 60-80°C and the time is 10-15h.

9. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: In S2, the amount of the initiator added is 1-1.5% of the mass of the polymer monomer A, and the amount of the RAFT agent added is 3-5% of the mass of the polymer monomer A.

10. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: In S3, the temperature of the second polymerization reaction is 60-80°C, and the reaction time is 10-15h.

11. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: In S3, the amount of initiator added is 0.5-1% of the mass of polymer monomer B; Preferably, the solvent used in S2 and S3 is ethanol.

12. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: The template carrier is paraffin; the mass ratio of molybdenum disulfide nanosheets, paraffin, and water in S1 is 1:10-12:100-110; Preferably, the heating temperature in S1 is 60-80° C., and the added template carrier is melted paraffin.

13. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 11, wherein: The method for removing the template carrier in S4 is: dispersing the hydrophilic polymer graft copolymer nanosheets in cyclohexane, and then washing with cyclohexane and deionized water.

14. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: In S4, the temperature of the third reaction is 30-50°C, and the reaction time is 20-40h.

15. The method for preparing the polymer microsphere profile control and water plugging agent according to claim 1, wherein: In S4, the amino acid is selected from one or a combination of two or more of glycine, alanine, serine, and cysteine; Preferably, the method for preparing the polymer microsphere profile control and water plugging agent further comprises: using the product of any step S1-S4 as a detergent; the detergent is a 10%-20% ethanol aqueous solution.

16. A polymer microsphere profile control and water plugging agent obtained by the preparation method of the polymer microsphere profile control and water plugging agent according to any one of claims 1 to 15.

17. The polymer microsphere profile control and water plugging agent according to claim 16, comprising molybdenum disulfide nanosheets, one side of the molybdenum disulfide nanosheets is grafted with a hydrophilic polymer, the other end of the hydrophilic polymer is connected to a modified polymer, and the other side of the molybdenum disulfide nanosheets is grafted with an amino acid.

18. Use of the polymer microsphere profile control and water plugging agent according to claim 16 or 17 in profile control and water plugging.

19. The use according to claim 18, wherein: The polymer microsphere profile control and water plugging agent is used at a concentration of 1000-5000 mg / L.

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