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

Abstract

The application provides a polymer microsphere profile control water plugging agent and a preparation method and application thereof, and the preparation method comprises the following steps: dispersing molybdenum disulfide nanosheets in water, adding a template carrier to form a Pickering emulsion; performing a first polymerization reaction on the Pickering emulsion, polymer monomer A, a RAFT reagent and an initiator to obtain hydrophilic polymer grafted copolymer nanosheets; performing a second polymerization reaction on the hydrophilic polymer grafted copolymer nanosheets, polymer monomer B and an initiator in a solvent to obtain one-side polymer modified nanosheets; removing the template carrier, and performing a third reaction on the one-side polymer modified nanosheets and amino acids in water to obtain the polymer microsphere profile control water plugging agent. The polymer microsphere profile control water plugging agent prepared by the application is resistant to temperature and salt, can enter deep strata, is uniformly distributed in high-permeability layers, has good profile control and water plugging effects, and can improve recovery efficiency.

Description

Technical Field

[0001] This invention relates to the field of oilfield recovery technology, specifically to a polymer microsphere profile control and water shut-off agent, its preparation method, and its application. Background Technology

[0002] During reservoir development, as development time increases, formation energy is depleted, leading to a decline in crude oil recovery efficiency. To improve formation crude oil recovery efficiency, most oilfields employ water injection to replenish formation energy and achieve high and stable production. However, due to formation heterogeneity, this water usually preferentially enters high-permeability layers with low seepage resistance, while a large amount of residual oil remains in low-permeability layers awaiting further development. This results in premature water breakthrough in wells, a rapid increase in water cut in the produced fluid, and low recovery rates. Therefore, to control water production, reduce water cut, and activate the remaining oil in low-permeability layers or increase the development of low-permeability layers, it is necessary to selectively block high-permeability layers and adjust the uneven water absorption profile of the formation, allowing more water to infiltrate low-permeability layers and thus driving more oil production.

[0003] Existing oilfields have developed two main methods for profile control and water shut-off: mechanical profile control and water shut-off, and chemical profile control and water shut-off. Compared to the limitations of mechanical profile control and water shut-off, chemical profile control and water shut-off is the most widely used and applied technology in oilfield profile control and water shut-off.

[0004] Polymer microspheres are a type of chemical profile control and water shut-off agent that has been widely studied and applied in recent years. They are mainly composed of a high molecular polymer formed by the cross-linking of hydrophilic groups. The polymer microspheres are very small in size and can smoothly enter the formation with the solution. The microspheres continuously hydrate and expand in the formation until they expand to their maximum volume. Then, they block the formation pore throat by relying on bridging, thereby changing the direction of injected water. Ma Guoyan et al. (Ma Guoyan, Shen Yiding, Gao Ruimin et al. Application performance study of nano-micro-sized 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- and salt-resistant amphiphilic polyacrylamide microsphere. After fully swelling in simulated water at 70℃, the particle size of this microsphere can expand from 50nm to 634nm, with a water absorption expansion ratio of more than 2000. However, the excessive pursuit of maximizing the expansion performance of microspheres has led to the swollen microspheres being prone to shearing and breakage during their migration to deeper regions, which has severely affected the profile control effect of the microspheres.

[0005] Liu Yuli (Liu Yuli. Research on Temperature- and Salt-Resistant Composite Profile Control System [D]. Yangtze University, 2015.) added acrylic acid to acrylamide and toughened it with bentonite to obtain a temperature- and salt-resistant pre-crosslinked polymer microsphere profile control agent. The particles can expand 100 times in clean water, but in highly saline water (16 × 10⁻⁶), the expansion is less significant. 4 In mg / L), the expansion rate is only 15.8 times. This shows that conventional polymer microspheres have poor temperature and salt resistance. They will harden under high temperature and high mineralization conditions, resulting in poor deformability and making it impossible to perform profile control in deep strata.

[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 polymers are prone to chain breakage and degradation; (2) They absorb water and swell during injection into the formation, and cannot reach the deep part of the formation; (3) Due to the limited water absorption and swelling effect, polymer microspheres with smaller initial particle size are less likely to effectively block the pore throat than polymer microspheres with larger initial particle size, and polymer microspheres with smaller initial particle size are more likely to enter the low permeability layer and cause damage to it.

[0007] Therefore, developing a novel polymer microsphere that can penetrate deep strata, be uniformly distributed in high-permeability layers, and be resistant to temperature and salt is a pressing practical problem that needs to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a polymer microsphere profile control and water-blocking agent, its preparation method, and its application.

[0009] To achieve the above objectives, the present invention provides a method for preparing a polymer microsphere profile control and water-blocking agent, comprising the following steps:

[0010] S1: Molybdenum disulfide nanosheets are dispersed in water, a template carrier is added, and the mixture is heated and stirred to form a Pickering emulsion.

[0011] S2: The Pickering emulsion, polymer monomer A, RAFT reagent and initiator are subjected to a first polymerization reaction in a solvent to obtain hydrophilic polymer grafted copolymer nanosheets;

[0012] S3: The hydrophilic polymer grafted copolymer nanosheets, polymer monomer B, and initiator are subjected to a second polymerization reaction in a solvent to obtain single-sided polymer modified nanosheets.

[0013] S4: Remove the template carrier from the single-sided polymer-modified nanosheets, and then carry out a third reaction between the single-sided polymer-modified nanosheets and amino acids in water to obtain the polymer microsphere profile-modifying and water-blocking agent.

[0014] The mass ratio of molybdenum disulfide nanosheets to polymer monomer A, polymer monomer B, and amino acids 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 shut-off agent of this invention uses molybdenum disulfide nanosheets as the core structure. Polymers formed from polymer monomers A and B, along with amino acids, modify the surface of the nanosheets, improving the overall rigidity of the polymer microspheres. This increases their resistance to temperature and salinity, allowing them to penetrate deep formations and distribute uniformly in high-permeability layers, resulting in excellent profile control and water shut-off effects and improved oil recovery. This invention attaches amino acids and block copolymers to the surface of molybdenum disulfide nanosheets to form a novel polymer microsphere profile control and water shut-off agent. This agent expands slowly, allowing it to penetrate deep formations and exhibiting strong interaction with the rock surface. By reducing the radius of high-permeability pore throats, it lowers the permeability of high-permeability layers. Finally, due to the inclusion of nanomaterials, its sensitivity to temperature and salinity is reduced, exhibiting temperature and salinity resistance.

[0017] Current technological improvements to polymer microspheres focus on two directions: one is to increase salt-resistant and heat-resistant monomers to strengthen the rigidity of the polymer chain; the other is to prepare rigid microspheres by combining them with nanomaterials. However, polymer microspheres still have significant drawbacks. On the one hand, they cannot penetrate deep, low-permeability layers; on the other hand, after sealing high-permeability layers near the wellbore, fluids will bypass them, reducing the profile control effect.

[0018] The profile control and water shut-off agent prepared in this invention improves the wettability of high-permeability layers by introducing amino acids, increases the seepage resistance of high-permeability layers, and simultaneously reduces the pore throat radius of high-permeability layers. Unlike conventional polymer microsphere bridging and pore throat blocking, the polymer microsphere profile control and water shut-off agent of this invention is uniformly adsorbed on the pore throat surface, achieving a diameter reduction effect. This not only allows the polymer microspheres to penetrate deep formations but also uniformly modifies high-permeability layers, reducing the occurrence of flow around the pores.

[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 more combinations 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 more combinations 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 crystal form of 1T, 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 reagent is S,S-dibenzyl trithiocarbonate or 2-[(dodecylthioalkyl)thioacyl]thioalkylpropionic acid. RAFT is short for Reversible Addition-Fragmentation Chain Transfer Polymerization, a type of living / controlled radical polymerization (CRP), and can be understood as a polymer method. The RAFT reagent described in this invention is a small molecule organic compound that links hydrophilic and hydrophobic polymers.

[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 initiator added is 1-1.5% of the mass of polymer monomer A, and the amount of RAFT reagent added is 3-5% of the mass of 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 10-15h.

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

[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 as follows: dispersing the hydrophilic polymer grafted 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 20-40h.

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

[0037] According to a specific embodiment of the present invention, preferably, the preparation method of the polymer microsphere profile control and water-blocking agent further includes: using the product of any one of the steps S1-S4 of the detergent; wherein the detergent is a 10-20% (ethanol mass fraction) aqueous solution of ethanol.

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

[0039] S1: Molybdenum disulfide nanosheets were ultrasonically dispersed in water to obtain an aqueous solution of molybdenum disulfide. The temperature of the solution was then raised to 60-80℃, followed by the addition of molten paraffin. The solution was then stirred in a high-speed mixer at 5000-8000 rpm for 3-5 minutes to form a Pickering emulsion, which was then allowed to cool. After cooling to below 25℃, the solution was washed by centrifugation with a 10-20% ethanol aqueous solution, and the upper white emulsion was collected.

[0040] S2: Mix white emulsion, ethanol, polymer monomer A and RAFT reagent in a beaker, then add initiator, and react at 60-80℃ for 10-15h. After the reaction, wash the product with 10-20% ethanol aqueous solution to obtain hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets.

[0041] S3: Molybdenum disulfide nanosheets grafted and copolymerized with hydrophilic polymer obtained in S2, ethanol, initiator AIBN and polymer monomer B are mixed in a beaker and reacted at 60-80℃ for 10-15h. After the reaction is completed, the product is washed with 10-20% ethanol aqueous solution to obtain unilateral polymer modified molybdenum disulfide nanosheets.

[0042] S4: The emulsion of unilaterally polymer-modified molybdenum disulfide nanosheets was dispersed in cyclohexane, and then washed with cyclohexane and deionized water. The precipitate was collected as unilaterally polymer-modified molybdenum disulfide nanosheets. The unilaterally polymer-modified molybdenum disulfide nanosheets were dispersed in an aqueous solution of amino acids and stirred at 30-50℃ for 20-40 h. After the reaction was completed, the product was washed with a 10-20% ethanol aqueous solution to obtain a polymer microsphere profile control and water-blocking agent.

[0043] The present invention also provides a polymer microsphere profile control and water plugging agent obtained by the above-described method for preparing 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-blocking agent includes molybdenum disulfide nanosheets, one side of which is grafted with a hydrophilic polymer, the other end of which is connected with a modified polymer, and the other side of which is grafted with amino acids.

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

[0046] In the above applications, preferably, the concentration of the polymer microsphere profile control and water-blocking agent is 1000-5000 mg / L.

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

[0048] (1) In order to increase the interaction force between the nanomaterial and the rock surface and achieve uniform adsorption in the pores, this invention selects molybdenum disulfide nanomaterial as the core and modifies it with different functional groups on both sides to give it different functions. Since the core structure is molybdenum disulfide nanosheets and its surface is modified with polymer (polymer monomer A + polymer monomer B) and small molecule organic matter (amino acid), the overall rigidity of the polymer microspheres is improved, the tolerance to temperature and mineralization is increased, and the temperature and salt resistance of the polymer microspheres are enhanced.

[0049] (2) The novel polymer microspheres provided by this invention have different wettability on both sides. The side modified by small molecules (amino acids) is mainly hydrophilic. By increasing the number of polar functional groups, the interaction force 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 sheet-like nanomaterial, which has a larger contact area than spherical nanomaterials, highlighting the advantages of sheet-like nanomaterials as the core.

[0050] (3) This invention also uses a block polymer to modify the other side of molybdenum disulfide. The block polymer is composed of a hydrophilic polymer (polymerized from monomer A) and a lipophilic polymer (polymerized from monomer B), with the hydrophilic polymer attached to the surface of the molybdenum disulfide and the hydrophobic end extending outwards. Conventional polymer microspheres are primarily composed of hydrophilic polymers, with some hydrophobic or salt-resistant monomers added to increase the polymer's temperature and salt resistance. However, the addition of a small amount of monomer does not have a decisive impact on the overall polymer structure. Therefore, this invention uses a block polymer, which has higher strength than conventional polymers.

[0051] (4) The profile control mechanism of the polymer microsphere profile control and water shut-off agent of the present invention is that after the polymer microspheres enter the formation with the fluid, the strong hydrophilic side of the grafted amino acid will generate a strong van der Waals force with the rock surface, thereby adsorbing onto the rock surface. In this way, the 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 driving force to 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 permeability of the water phase in the deep layers.

[0052] (5) If the polymer microsphere profile control and water-blocking agent of the present invention encounters an oil-bearing layer, the structure of the polymer microsphere is similar to that of a surfactant, exhibiting amphiphilicity. The hydrophobic end (polymer) on one side of the nanosheet interacts with the crude oil, while the hydrophilic end (formed by amino acids) on the other side interacts with water, forming a stable emulsion to achieve the purpose of emulsification and oil displacement. This also prevents the polymer microsphere from entering the low-permeability layer before expanding, thus avoiding damage to the low-permeability layer. Attached Figure Description

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

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

[0055] Figure 3 The particle size distribution of the polymer microsphere profile-adjusting and water-blocking agent prepared in Example 1 (before water absorption and swelling);

[0056] Figure 4 Microscopic image of the polymer microsphere profile control and water-blocking agent prepared in Example 1 after being placed at 100°C for 7 days. Detailed Implementation

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

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

[0059] Example 1

[0060] This embodiment prepares a polymer microsphere profile control and water-blocking agent, such as... Figure 1 As shown, its preparation method includes the following steps:

[0061] (1) 1 g of 1T crystal molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution. Then the temperature was raised to 80 °C, and 10 g of molten paraffin was added. The mixture was then stirred in a high-speed mixer at 8000 rpm for 3 min to form a Pickering emulsion, and then allowed to cool. After cooling to below 25 °C, the mixture was washed by centrifugation with a 20% ethanol aqueous solution, and the upper white emulsion was collected.

[0062] (2) The white emulsion obtained in step (1), 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylthioalkyl)thioacryl]-thioalkylpropionic 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 20% ethanol aqueous solution to obtain hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets.

[0063] (3) Then, the hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets obtained in step (2), ethanol, 0.5g AIBN and 50g styrene were mixed in a beaker and reacted at 60°C for 12h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain a single-sided polymer modified molybdenum disulfide nanosheet emulsion.

[0064] (4) The unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) is dispersed in cyclohexane, washed with cyclohexane and deionized water, and the precipitate is collected as unilateral polymer-modified molybdenum disulfide nanosheets; the unilateral polymer-modified molybdenum disulfide nanosheets are dispersed in an aqueous solution, 15g of serine is added, and the mixture is stirred at 30°C for 20h. After the reaction is completed, the product is washed with 20% ethanol aqueous solution to obtain the polymer microsphere profile control and water-blocking agent.

[0065] To test the salt resistance of the polymer microsphere profile control and water-blocking agent (polymer microspheres) prepared in this embodiment, 0.1 g of the synthesized polymer microspheres were dispersed in 6.0 mL of 1 mol / L sodium chloride solution, and the water absorption ratio of the polymer microspheres at different times was measured. The experimental results are as follows. Figure 2 As shown, this polymer microsphere profile control and water-blocking agent exhibits high salt resistance.

[0066] This embodiment also measured the particle size distribution of the prepared polymer microsphere profile control and water-blocking agent under unexpanded conditions, and 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 them, microspheres with a particle size of 163 nm account for 3%, microspheres with a particle size of 177 nm account for 32%, microspheres with a particle size of 180 nm account for 43%, and microspheres with a particle size of 183 nm account for 22%.

[0067] The present invention also determined that the polymer microspheres of Example 1 had a particle size in the micrometer range after being placed at 100°C for 7 days. Figure 4 As shown, this property enables the polymer microsphere profile control and water shut-off agent to penetrate deeper into the formation, thereby achieving profile control and improving oil recovery.

[0068] Example 2

[0069] This embodiment provides a polymer microsphere profile control and water-blocking agent, the preparation method of which includes the following steps:

[0070] (1) 1 g of 1T crystal molybdenum disulfide (size 80 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution. Then the temperature was raised to 80 °C, and 12 g of molten paraffin was added. Then the mixture was stirred in a high-speed mixer at 8000 rpm for 3 min to form a Pickering emulsion. Then the mixture was allowed to cool. After cooling to below 25 °C, the mixture was washed by centrifugation 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. The mixture was reacted at 60 °C for 15 h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets.

[0072] (3) Then, the hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets obtained in step (2), ethanol, 1g AIBN and 100g vinyltriethoxysilane were mixed in a beaker and reacted at 60°C for 15h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain a single-sided polymer modified molybdenum disulfide nanosheet emulsion.

[0073] (4) The unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) is dispersed in cyclohexane, washed with cyclohexane and deionized water, and the precipitate is collected as unilateral polymer-modified molybdenum disulfide nanosheets; the unilateral polymer-modified molybdenum disulfide nanosheets are dispersed in an aqueous solution, 10g of cysteine ​​is added, and the mixture is stirred at 30°C for 30h. After the reaction is completed, the product is washed with 20% ethanol aqueous solution to obtain the polymer microsphere profile control and water-blocking agent.

[0074] Example 3

[0075] This embodiment provides a polymer microsphere profile control and water-blocking agent, including the following steps:

[0076] (1) 1 g of 1T molybdenum disulfide (100 nm in size) was ultrasonically dispersed in 100 g of water to obtain an aqueous solution of molybdenum disulfide. The temperature was then raised to 80 °C, and 10 g of molten paraffin was added. The mixture was then stirred in a high-speed mixer at 8000 rpm for 3 min to form a Pickering emulsion, and then allowed to cool. After cooling to below 25 °C, the upper white emulsion was collected after centrifugation and washing with a 20% aqueous ethanol solution.

[0077] (2) The 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-[(dodecylthioalkyl)thioacyl]-thioalkylpropionic 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 was completed, the product was washed with 20% ethanol aqueous solution to obtain hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets.

[0078] (3) Then, the hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets obtained in step (2), ethanol, 1g AIBN and 100g styrene were mixed in a beaker and reacted at 60°C for 15h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain a single-sided polymer modified molybdenum disulfide nanosheet emulsion.

[0079] (4) The unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) is dispersed in cyclohexane, washed with cyclohexane and deionized water, and the precipitate is collected as unilateral polymer-modified molybdenum disulfide nanosheets; the unilateral polymer-modified molybdenum disulfide nanosheets are dispersed in an aqueous solution, 10g of glycine is added, and the mixture is stirred at 30°C for 20h. After the reaction is completed, the product is washed with 20% ethanol aqueous solution to obtain the polymer microsphere profile control and water-blocking agent.

[0080] Example 4

[0081] This embodiment prepares a polymer microsphere profile control and water-blocking agent, and the preparation method includes the following steps:

[0082] (1) 1 g of 1T crystal molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution. Then the temperature was raised to 80 °C, and 10 g of molten paraffin was added. Then the mixture was stirred in a high-speed mixer at 5000 rpm for 5 min to form a Pickering emulsion. Then the mixture was allowed to cool. After cooling to below 25 °C, the mixture was washed by centrifugation 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-[(dodecylthioalkyl)thioacryl]-thioalkylpropionic acid reagent were mixed in a beaker, and then 0.75 g of AIBN was added. The mixture was reacted at 80 °C for 10 h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets.

[0084] (3) Then, the hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets obtained in step (2), ethanol, 0.5g AIBN, 20g styrene and 10g 4-vinylpyridine were mixed in a beaker and reacted at 80°C for 12h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain a single-sided polymer modified molybdenum disulfide nanosheet emulsion.

[0085] (4) The unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) is dispersed in cyclohexane, washed with cyclohexane and deionized water, and the precipitate is collected as unilateral polymer-modified molybdenum disulfide nanosheets; the unilateral polymer-modified molybdenum disulfide nanosheets are dispersed in an aqueous solution, 5g of serine is added, and the mixture is stirred at 30°C for 20h. After the reaction is completed, the product is washed with 20% ethanol aqueous solution to obtain the polymer microsphere profile control and water-blocking agent.

[0086] Example 5

[0087] This embodiment prepares a polymer microsphere profile control and water-blocking agent, and the preparation method includes the following steps:

[0088] (1) 1 g of 1T molybdenum disulfide (size 80 nm) was ultrasonically dispersed in 100 g of water to obtain an aqueous solution of molybdenum disulfide. Then the temperature was raised to 80 °C, and 10 g of molten paraffin was added. The mixture was then stirred in a high-speed mixer at 5000 rpm for 3 min to form a Pickering emulsion, and then allowed to cool. After cooling to below 25 °C, the mixture was washed by centrifugation with a 20% ethanol aqueous solution, and the upper white emulsion was collected.

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

[0090] (3) Then, the hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets obtained in step (2), ethanol, 0.2g AIBN and 40g styrene were mixed in a beaker and reacted at 80°C for 10h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain a single-sided polymer modified molybdenum disulfide nanosheet emulsion.

[0091] (4) The unilateral polymer-modified molybdenum disulfide nanosheet emulsion obtained in step (3) is dispersed in cyclohexane, washed with cyclohexane and deionized water, and the precipitate is collected as unilateral polymer-modified molybdenum disulfide nanosheets; the unilateral polymer-modified molybdenum disulfide nanosheets are dispersed in an aqueous solution, 5g of glycine is added, and the mixture is stirred at 30°C for 20h. After the reaction is completed, the product is washed with 20% ethanol aqueous solution to obtain the polymer microsphere profile control and water-blocking agent.

[0092] Comparative Example 1

[0093] This comparative example provides a profile control and water-blocking agent, the preparation method of which is as follows:

[0094] (1) Mix 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylthioalkyl)thioacyl]-thioalkylpropionic acid reagent in a beaker, then add 0.75 g of AIBN and react at 60 °C for 10 h. After the reaction is complete, wash the product with 20% ethanol aqueous solution to obtain the hydrophilic polymer.

[0095] (2) Then the product from the previous step, ethanol, 0.5g AIBN and 50g styrene are mixed in a beaker and reacted at 60°C for 12h. After the reaction is completed, the product is washed with 20% ethanol aqueous solution to obtain the block polymer, which is the profile control and water shut-off agent of this embodiment.

[0096] Comparative Example 2

[0097] This comparative example provides a profile control and water-blocking agent, the preparation method of which is as follows:

[0098] (1) 1 g of 1T crystal molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution. Then the temperature was raised to 80 °C, and 10 g of molten paraffin was added. The mixture was then stirred in a high-speed mixer at 8000 rpm for 3 min to form a Pickering emulsion, and then allowed to cool. After cooling to below 25 °C, the mixture was washed by centrifugation with a 20% ethanol aqueous solution, and the upper white emulsion was collected.

[0099] (2) Mix the upper white emulsion, 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylthioalkyl)thioacyl]-thioalkylpropionic acid reagent in a beaker, then add 0.75 g of AIBN, and react at 60 °C for 10 h. After the reaction is complete, wash the product with 20% ethanol aqueous solution to obtain hydrophilic polymer graft copolymerized molybdenum disulfide nanosheets.

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

[0101] Comparative Example 3

[0102] This comparative example provides a profile control and water-blocking agent, the preparation method of which is as follows:

[0103] (1) 1 g of 1T crystal molybdenum disulfide (size 150 nm) was ultrasonically dispersed in 100 g of water to obtain a molybdenum disulfide aqueous solution. Then the temperature was raised to 80 °C, and 10 g of molten paraffin was added. The mixture was then stirred in a high-speed mixer at 8000 rpm for 3 min to form a Pickering emulsion, and then allowed to cool. After cooling to below 25 °C, the mixture was washed by centrifugation with a 20% ethanol aqueous solution, and the upper white emulsion was collected.

[0104] (2) Mix the upper white emulsion, 200 mL of ethanol, 50 g of acrylamide and 2.5 g of 2-[(dodecylthioalkyl)thioacyl]-thioalkylpropionic acid reagent in a beaker, then add 0.75 g of AIBN, and react at 60 °C for 10 h. After the reaction is complete, wash the product with 20% ethanol aqueous solution to obtain a hydrophilic polymer graft copolymerized molybdenum disulfide nanosheet emulsion.

[0105] (3) The emulsion of molybdenum disulfide nanosheets grafted with hydrophilic polymer was dispersed in cyclohexane, and then washed with cyclohexane and deionized water. The precipitate was collected as unilateral polymer-modified molybdenum disulfide nanosheets. The unilateral polymer-modified molybdenum disulfide nanosheets were dispersed in an aqueous solution, 15g of serine was added, and the mixture was stirred at 30℃ for 20h. After the reaction was completed, the product was washed with 20% ethanol aqueous solution to obtain the profile control and water-blocking agent.

[0106] Experimental Example 1

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

[0108] An experiment was conducted to investigate the effect of microsphere-assisted oil displacement using a one-dimensional core-based displacement device. This device consists of a horizontal flow pump, an intermediate container (for holding experimental fluids such as oil, water, and displacement agents), and a core holder with pressure measurement points. The experimental procedures are as follows:

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

[0110] ② Saturated water stage: The core was saturated with water using a constant flow pump at a rate of 10 mL / min. The wet weight of the core was measured and the pore volume PV was calculated based on the mass difference before and after saturation.

[0111] ③ Saturated oil stage: The core was saturated with oil using a constant flow pump at a rate of 10 mL / min. The volume of water produced was recorded during the process, and the oil saturation So was calculated.

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

[0113] ⑤ Microsphere displacement stage: 0.3 PV microspheres were displaced using a constant flow pump at a rate of 0.3 mL / min. Pressure change data were recorded and water content was calculated during the process. After injecting the microspheres, the mixture was left to stand for 1 day.

[0114] ⑥ Subsequent water drive stage: 2PV water drive operation was carried out in the core after microspheres were injected and left to stand for 1 day using a constant flow pump at a constant rate of 2 mL / min. Pressure change data were recorded, and the change in water cut and the increase in recovery rate were calculated.

[0115] The results are shown in Table 1.

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

[0117]

[0118] The experimental results show that the polymer microsphere profile control and water shut-off agent of the present invention has a significant water shut-off effect, and the recovery rate can generally be increased by more than 10%.

[0119] Compared to the examples, Comparative Example 1 did not include molybdenum disulfide nanosheets, resulting in a block copolymer polymer. Due to the self-assembly characteristics of polymers, it is not easy to form a blockage. Comparative Example 2 did not include amino acids; only the unilaterally polymer-modified molybdenum disulfide nanosheets were effective. Due to the weak interaction with the rock surface, it was difficult to achieve an adsorption and retention effect, and it could only play a role in expansion and blockage. Comparative Example 3 did not involve block copolymerization; only acrylamide (polymer monomer A) was homopolymerized. Its effect was similar to conventional water-blocking microspheres, mainly by absorbing water and expanding to block the pore throat. Since the wettability of the pore throat was not changed, its effect was worse than that of the examples of the present invention.

Claims

1. A method for preparing a polymer microsphere profile control and water-blocking agent, comprising the following steps: S1: Molybdenum disulfide nanosheets are dispersed in water, a template carrier is added, and the mixture is heated and stirred to form a Pickering emulsion; the template carrier is paraffin. S2: The Pickering emulsion, polymer monomer A, RAFT reagent and initiator are subjected to a first polymerization reaction in a solvent to obtain hydrophilic polymer grafted copolymer nanosheets; S3: The hydrophilic polymer grafted copolymer nanosheets, polymer monomer B, and initiator are subjected to a second polymerization reaction in a solvent to obtain single-sided polymer modified nanosheets. S4: Remove the template carrier from the single-sided polymer-modified nanosheets, and then carry out a third reaction between the single-sided polymer-modified nanosheets and amino acids in water to obtain the polymer microsphere profile-modifying and water-blocking agent. in, The mass ratio of molybdenum disulfide nanosheets to polymer monomer A, polymer monomer B, and amino acids is 1:30-100:30-100:5-15; polymer monomer A is selected from one or more of acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid; polymer monomer B is selected from one or more of styrene, 4-vinylpyridine, and vinyltriethoxysilane.

2. The preparation method of the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The molybdenum disulfide nanosheets are selected from molybdenum disulfide nanosheets with a crystal form of 1T and a size of 80-150 nm.

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

4. The preparation method of the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The initiator is azobisisobutyronitrile.

5. The preparation method of the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The RAFT reagent is S,S-dibenzyl trithiocarbonate or 2-[(dodecylthioalkyl)thioacyl]-thioalkylpropionic acid.

6. The preparation method of the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, In S2, the temperature of the first polymerization reaction is 60-80℃ and the time is 10-15h.

7. The preparation method of the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, In S2, the amount of initiator added is 1-1.5% of the mass of polymer monomer A, and the amount of RAFT reagent added is 3-5% of the mass of polymer monomer A.

8. The preparation method of the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, In S3, the temperature of the second polymerization reaction is 60-80℃, and the reaction time is 10-15h.

9. The preparation method of the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, In S3, the amount of initiator added is 0.5-1% of the mass of polymer monomer B.

10. The method for preparing the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The solvent used in S2 and S3 is ethanol.

11. The method for preparing the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The mass ratio of molybdenum disulfide nanosheets, paraffin wax, and water in S1 is 1:10-12:100-110.

12. The method for preparing the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The heating temperature in S1 is 60-80℃, and the added template carrier is molten paraffin.

13. The method for preparing the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The method for removing the template carrier in S4 is as follows: the hydrophilic polymer grafted copolymer nanosheets are dispersed in cyclohexane, and then washed with cyclohexane and deionized water.

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

15. The method for preparing the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, In S4, the amino acid is selected from one or more combinations of glycine, alanine, serine, and cysteine.

16. The method for preparing the polymer microsphere profile control and water-blocking agent according to claim 1, wherein, The preparation method of the polymer microsphere profile control and water-blocking agent further includes: washing the product of any step S1-S4 with a detergent; the detergent is a 10%-20% aqueous ethanol solution.

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

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

19. The application of the polymer microsphere profile control and water shut-off agent according to claim 17 or 18 in profile control and water shut-off.

20. The application according to claim 19, wherein, The concentration of the polymer microsphere profile control and water-blocking agent is 1000-5000 mg / L.

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