Amphiphilic Janus tungsten disulfide nano-emulsifying tackifier, and preparation method and application thereof

Abstract

This invention belongs to the field of enhanced oil recovery (EOR) technology, specifically disclosing an amphiphilic Janus tungsten disulfide nanoemulsion thickener, its preparation method, and its application. The method includes the following steps: First, tungsten disulfide and a first oxidant are added to a first solvent to obtain tungsten disulfide with surface-modified hydroxyl groups; second, a second solvent and a first modifier are added, followed by a first catalyst, to obtain carboxyl-modified tungsten disulfide; finally, it is added to a second solvent and reacted with a second and a third modifier to obtain thickened Janus tungsten disulfide nanosheets. This invention can significantly improve the viscosity of the displacement front in the mid-to-late stages of reservoir development, increase swept volume and oil displacement efficiency, achieve a crude oil viscosity increase of 1192%, possess excellent interfacial tension reduction capabilities, and improve oil recovery by more than 20%, demonstrating a significant enhanced oil recovery effect.

Description

Technical Field

[0001] This invention relates to the field of enhanced oil recovery technology, and in particular to a Janus tungsten disulfide nanoemulsified thickener, its preparation method, and its application. Background Technology

[0002] Currently, most of my country's major oilfields have entered the late stage of high water-cut development, but a considerable amount of crude oil remains in the formations in complex forms, indicating a huge potential for residual oil recovery. Chemical flooding is one of the most mature enhanced oil recovery technologies, and conventional chemical flooding methods mainly include surfactant flooding, polymer flooding, and alkaline flooding. While surfactant flooding can effectively reduce interfacial tension, it suffers from high adsorption losses and poor emulsion stability; polymer flooding can improve sweep efficiency, but it has poor salt and temperature resistance and is prone to degradation; alkaline flooding is low-cost but easily causes scaling and damages the formation. Therefore, there is an urgent need for an efficient extraction method to address the problems of low sweep efficiency and difficulty in recovering residual oil in high water-cut reservoirs during the late stage of development.

[0003] Nanofluid flooding, as an emerging enhanced oil recovery technology in recent years, has shown excellent potential for improving oil recovery due to its characteristics such as reducing interfacial tension, adhering to and stripping crude oil, in-situ emulsification, increasing interfacial film strength, and resistance to temperature and salt. Furthermore, by modifying nanomaterials with amphiphilic properties to impart interfacial activity, nanomaterials can spontaneously aggregate towards the oil-water two phases, forming water-in-oil emulsions under shear stress. This increases the viscosity of the displacement front, thereby reducing the mobility ratio and increasing sweep efficiency. Moreover, nanomaterials can adapt to more demanding formation environments.

[0004] Therefore, designing highly efficient viscosity-enhancing nanomaterials is key to improving reservoir displacement efficiency, addressing the challenges of crude oil extraction in the later stages of reservoir development. Summary of the Invention

[0005] The purpose of this invention is to provide a Janus tungsten disulfide nanoemulsifying thickener, its preparation method and application, which achieves a crude oil thickening rate of 1192% and has excellent interfacial tension reduction effect, increasing the recovery rate by more than 20%, with a significant effect on improving the recovery rate.

[0006] To achieve the above objectives, this invention provides a method for preparing Janus tungsten disulfide nanoemulsified thickener, comprising the following steps:

[0007] S1. Tungsten disulfide and the first oxidant are added to the first solvent in proportion, heated in an oil bath, and then filtered, washed and dried to obtain tungsten disulfide with surface hydroxylation treatment.

[0008] S2. According to the proportion, the surface-hydroxylated tungsten disulfide obtained in S1 and the first modifier are added to the second solvent, and then the first catalyst is added. After heating and filtration, carboxyl-modified tungsten disulfide is obtained.

[0009] S3. The carboxyl-modified tungsten disulfide obtained in S2, the first catalyst and the second modifier are added to the second solvent. Then the third modifier is added to the third solvent. The two solutions are mixed, heated and stirred, washed and filtered to obtain Janus tungsten disulfide nano-adhesive.

[0010] Preferably, in S1, the concentration of tungsten disulfide is 0.12~0.15 mol / L; the concentration of the first oxidant is 0.06~0.08 mol / L; and the first solvent is a sodium hydroxide solution of 0.4~0.6 mol / L.

[0011] Preferably, S1 is as follows:

[0012] Tungsten disulfide and sodium persulfate were added to a sodium hydroxide solution and heated continuously at 30-40°C for 1 hour. After washing, filtering and drying, tungsten disulfide with surface hydroxylation treatment was obtained.

[0013] Preferably, in S2, the mass-to-volume ratio of the surface-hydroxylated tungsten disulfide, the first catalyst, the first modifier, and the second solvent is 1g: 2~3g: 1~1.2g: 30~40ml; the first catalyst is N,N'-dicyclohexylcarbodiimide, the first modifier is maleic acid, and the second solvent is dimethyl sulfoxide.

[0014] Preferably, S2 is as follows:

[0015] The surface-hydroxylated tungsten disulfide obtained in S1 is added to the second solvent, followed by the first catalyst. The reaction is carried out at 25-30°C for 12-14 hours, followed by washing, filtration, and drying to obtain carboxyl-modified tungsten disulfide. Preferably, in S3, the mass-to-volume ratio of the carboxyl-modified tungsten disulfide obtained in S2, the second modifier, and the first catalyst is 1 g: 2-2.2 g: 30-40 ml, and the mass-to-volume ratio of the third modifier to the third solvent is 2-2.3 g: 30-40 ml.

[0016] The second modifier is sodium aminosulfonate; the second solvent is dimethyl sulfoxide; the first catalyst is N,N'-dicyclohexylcarbodiimide; the third solvent is n-heptane; and the third modifier is stearylamine.

[0017] Preferably, S3 is as follows:

[0018] Carboxyl-modified tungsten disulfide obtained from S2 was added to 30-40 ml of dimethyl sulfoxide, followed by the addition of the first catalyst and the second modifier to prepare an aqueous solution. Then, 30-40 ml of a hydrophobic solution prepared from n-heptane and the third modifier was added. The mixture was stirred at 12000-13000 rpm / min for 10-15 min. The reaction was then carried out at 25-30℃ and 400-600 rpm for 24-30 h. After filtration, washing, and drying, Janus tungsten disulfide nano-adhesive was obtained.

[0019] Therefore, the present invention employs the above-mentioned amphiphilic Janus tungsten disulfide nanoemulsifying thickener, its preparation method, and its application, with the following beneficial effects:

[0020] Compared with existing technologies, the preparation method of this invention uses nano-tungsten disulfide as a substrate, introduces hydroxyl groups by partial defect treatment through oxidation, and asymmetrically modifies tungsten disulfide through interfacial self-assembly under high-speed stirring to introduce hydrophilic and hydrophobic active groups, so that tungsten disulfide has more prominent interfacial activity, reduces interfacial tension, improves emulsification and viscosity enhancement effect, and can effectively improve reservoir recovery.

[0021] Compared to existing nanomaterials that typically require compounding with surfactants to achieve significant thickening effects, the nanoemulsified thickener of this invention can achieve a thickening rate of 1192% without the addition of surfactants and can increase the recovery rate by more than 20%, demonstrating a significant effect on improving the recovery rate.

[0022] Compared to conventional surfactants, this invention features low dosage and high efficiency. Tungsten disulfide, as a natural tungsten spodumene, can also be artificially synthesized, making it widely available and environmentally friendly, and can be applied extensively in the field.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the synthesis of an amphiphilic Janus tungsten disulfide nanoemulsifying thickener, its preparation method, and application examples according to the present invention.

[0025] Figure 2 This is an FT-IR characteristic curve of an amphiphilic Janus tungsten disulfide nanoemulsifying thickener, its preparation method, and application examples according to the present invention;

[0026] Figure 3 This invention relates to an amphiphilic Janus tungsten disulfide nanoemulsifying thickener, its preparation method, and application examples, showing the thickening effects at different concentrations.

[0027] Figure 4This is an experimental result diagram showing the improved oil recovery of an amphiphilic Janus tungsten disulfide nanoemulsion thickener, its preparation method, and application examples according to the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0030] Example 1: As Figure 1 As shown, a method for preparing viscous (amphiphilic) Janus nano-tungsten disulfide is as follows:

[0031] Prepare 30 ml of 0.5 mol / L sodium hydroxide solution for later use. Add 1 g of tungsten disulfide and 0.5 g of sodium persulfate in sequence. React at a constant temperature of 35 °C for 1 hour. After the reaction is completed, filter the solid product and wash it repeatedly with deionized water to obtain tungsten disulfide with surface hydroxylation treatment.

[0032] Prepare 30 ml of dimethyl sulfoxide as a solvent, add 1 g of maleic acid and 1 g of surface-hydroxylated tungsten disulfide in sequence, and add 2.6 g of N,N'-dicyclohexylcarbodiimide as a catalyst. The reaction is carried out at 25 °C for 12 h. After the reaction is completed, the solid product obtained by filtration is repeatedly washed with deionized water to obtain carboxyl-modified tungsten disulfide.

[0033] 1g of carboxyl-modified tungsten disulfide, 2g of N,N'-dicyclohexylcarbodiimide, and 2g of sodium aminosulfonate were added to 30ml of dimethyl sulfoxide to prepare a hydrophilic solution for later use. 2g of stearylamine was added to 30ml of n-heptane to prepare a hydrophobic solution for later use. The hydrophilic and hydrophobic solutions were mixed and added to the solution, and the mixture was stirred at 12000-13000rpm for 10 minutes. The mixture was then stirred and reacted at 25℃ and 400-600r / min for 24 hours. After filtration, washing, and drying, the amphiphilic Janus tungsten disulfide nano-adhesive was obtained.

[0034] Test

[0035] (1) FT-IR test

[0036] The functional group composition of nano-tungsten disulfide, carboxyl-modified tungsten disulfide prepared in Example 1, and amphiphilic Janus tungsten disulfide was analyzed by FT-IR. The results are as follows: Figure 2 As shown.

[0037] Depend on Figure 2 It can be known that 720cm -1 This is the in-plane rocking vibration peak of long-chain alkanes; 1187 cm⁻¹-1 The characteristic peak of the stretching vibration of CN; 1242 cm⁻¹ -1 The characteristic peak of the stretching vibration of S=O; 1574 cm⁻¹ -1 and 1627cm -1 The peaks at 2852 cm⁻¹ are characteristic peaks of the stretching vibrations of the carboxyl and carbonyl groups, respectively; -1 It is the characteristic peak of the symmetric stretching vibration of CH in the methylene group; 3033 cm⁻¹ -1 It is the stretching vibration peak of C=CH in alkenes connected to carbon-carbon double bonds; 3327 cm⁻¹ -1 This is the stretching vibration peak of NH. 1574 cm⁻¹ -1 1627cm -1 2852cm -1 And 3033cm -1 The peak at 3327 cm⁻¹ represents the successful grafting of maleic acid onto the surface of tungsten disulfide, compared to maleic acid-modified tungsten disulfide. -1 The peak value increases at this point because the formation of the amide bond causes the NH bond to stretch and vibrate at this location, resulting in a larger and broader peak value. This, combined with the stretching vibration peak of the carbonyl group, further confirms the formation of the amide bond. (1242 cm⁻¹) -1 The peak at 730 cm⁻¹ indicates successful grafting of aminosulfonic acid; -1 The peak indicates successful grafting of long-chain alkanes. In conclusion, the amphiphilic Janus tungsten disulfide nano-adhesive was successfully synthesized.

[0038] Emulsification and thickening test

[0039] Janus tungsten disulfide nano-thickening agent of different concentrations (100~2000 mg / L) was prepared and stirred for 1.5 h in a water bath equipped with a magnetic stirrer at 80℃ and a water-to-oil volume ratio of 6:4. The viscosity of the emulsion was then measured using a Brookifield DV-Ⅲ viscometer. The experimental results are as follows: Figure 3 As shown in the figure. The calculation method for emulsion viscosity is shown in Formula 1 (the crude oil viscosity at 80℃ is 13.7 mPa·s).

[0040] (1)

[0041] In the formula, η is the crude oil viscosity increase rate, % (μ). o Crude oil viscosity, mPa·s, μ e ν is the emulsion viscosity, mPa·s.

[0042] Depend on Figure 3It was found that as the concentration of Janus tungsten disulfide nano-thickening agent increased, the viscosity of the formed emulsion first increased and then decreased, reaching a maximum of 177 mPa·s at 1800 mg / L, with a thickening rate of 1192%, demonstrating that the developed Janus nano-tungsten disulfide possesses excellent thickening effects. At lower concentrations, the concentration of Janus nano-tungsten disulfide thickening agent adsorbed at the oil-water interface is low, resulting in limited effect in reducing interfacial tension and a weak interfacial barrier effect. At this point, the emulsion stability is poor, and the emulsion viscosity is low. When the concentration reaches the critical micelle concentration, the adsorption of Janus nano-tungsten disulfide thickening agent at the interface becomes saturated. Tungsten disulfide in the dispersed phase attracts tungsten disulfide at the interface, leading to adsorption instability at the interface and thus reducing emulsion stability. Therefore, the optimal concentration of 1800 mg / L was selected.

[0043] Enhanced oil recovery test

[0044] Janus amphiphilic nano-tungsten disulfide prepared in Example 1 with a concentration of 1800 mg / L and the remainder being water, was used to prepare a Janus nano-tungsten disulfide thickener. A core displacement experiment was conducted using a core with a water permeability of 1500 mD. The specific steps were as follows: First, the core was evacuated and saturated with simulated formation water. At 80°C, crude oil was used to saturate the water-saturated core at a rate of 0.1 ml / min until no more water was discharged from the end of the core holder. The valves at the front and rear ends of the core holder were closed, and the core was aged in an 80°C oven for 24 hours. Then, simulated formation water was injected at a rate of 0.5 ml / min until the water cut at the outlet reached 98%. Next, 0.6 PV of Janus nano-tungsten disulfide high-efficiency thickener was injected at a rate of 0.5 ml / min, followed by water injection at a flow rate of 0.5 ml / min until the water cut at the outlet of the core holder reached 98%, at which point injection was stopped.

[0045] Throughout the process, the injection end pressure, water cut, and cumulative recovery rate were recorded at every 0.05 PV injection volume, and the water cut, recovery rate, and injection end pressure curves were plotted. The water cut calculation formula is shown in Equation (2), and the recovery rate calculation formula is shown in Equation (3).

[0046] (2)

[0047] In the formula, f Moisture content; V 1 The water content in the collected fluid, in ml; V t The total volume of the collected fluid is in ml.

[0048] (3)

[0049] In the formula,E For recovery rate; V c The total volume of oil recovered is expressed in ml. V n Let be the volume of oil in the rock pores, in ml.

[0050] Results of experiments to improve oil recovery rate, such as Figure 4 As shown, when waterflooding begins, a two-phase flow of oil and water is formed. At this time, the oil saturation is high, the waterflooding resistance is large, and the displacement pressure differential gradually increases. Simultaneously, as waterflooding progresses, crude oil is continuously extracted from the core, and the recovery rate gradually increases. With the increase in injection volume, water gradually emerges at the core outlet, and the water cut gradually increases until a dominant waterflooding channel is fully formed in the core. At this point, the pressure gradually stabilizes, the recovery rate reaches a plateau, and the water cut reaches 98%. Although a large amount of residual oil remains in the core, it is difficult to extract. When high-efficiency nanofluidization begins, the initial displacement characteristics still maintain the characteristics of waterflooding; this stage is the pressure response stage. As displacement proceeds, the nanofluid gradually emulsifies with the residual oil in situ, forming a water-in-oil emulsion that blocks the dominant flow channel. At this time, a large amount of nanofluid enters the unseeded area, further forming a water-in-oil emulsion, manifested as a sharp increase in pressure, accompanied by a decrease in water cut and a second increase in recovery rate. After the secondary waterflooding begins, the injected water continues to displace along the blocked channels, carrying the formed emulsion out of the core. At this point, the recovery rate gradually increases, the water cut gradually increases, and the displacement pressure gradually decreases due to the decrease in oil phase saturation. The final recovery rate is 52.8%, with the high-efficiency nanofluid enhancing the recovery rate by 27.8%. The amphiphilic Janus tungsten disulfide nanoemulsion thickener exhibits excellent enhanced oil recovery capabilities.

[0051] Therefore, the present invention uses the above-mentioned amphiphilic Janus tungsten disulfide nanoemulsifying thickener, which achieves a thickening rate of 1192%, and has excellent effects in reducing interfacial tension and emulsifying and thickening, thereby increasing the recovery rate by more than 25%, and the effect of improving the recovery rate is significant.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an amphiphilic Janus tungsten disulfide nanoemulsion thickener, characterized in that, Includes the following steps: S1. Tungsten disulfide and sodium persulfate (the first oxidant) are added to sodium hydroxide solution (the first solvent) in proportion, heated and stirred, and then filtered, washed and dried to obtain tungsten disulfide with surface hydroxylation treatment. S2. According to the proportion, the surface-hydroxylated tungsten disulfide obtained in S1 and the first modifier maleic acid are added to the second solvent dimethyl sulfoxide, and then the first catalyst N,N'-dicyclohexylcarbodiimide is added. After heating and filtration, carboxyl-modified tungsten disulfide is obtained. S3. The carboxyl-modified tungsten disulfide obtained in S2 is added to a mixed solvent of the third solvent n-heptane and the second solvent dimethyl sulfoxide. Under the action of the first catalyst N,N'-dicyclohexylcarbodiimide, it reacts with the second modifier sodium aminosulfonate and the third modifier stearylamine. The mixture is heated and stirred, washed and filtered to obtain Janus tungsten disulfide nanoemulsifying thickener.

2. The method for preparing an amphiphilic Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, In S1, the concentration of tungsten disulfide is 0.13 mol / L.

3. The method for preparing an amphiphilic Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, S1 specifically refers to: Tungsten disulfide and sodium persulfate were added to the first solvent and placed in an oil bath. The mixture was reacted at a constant temperature of 35°C for 1 hour. After washing, filtering and drying, tungsten disulfide with surface hydroxylation treatment was obtained.

4. The method for preparing an amphiphilic Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, In S2, the mass-volume ratio of the surface-hydroxylated tungsten disulfide, the first catalyst, the first modifier, and the second solvent is 1g: 2.6g: 1g: 30ml.

5. The method for preparing an amphiphilic Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, S2 specifically refers to: The surface-hydroxylated tungsten disulfide obtained from S1 and the first modifier were added to the second solvent, followed by the first catalyst. The mixture was heated at 25°C for 12 hours, and then washed, filtered, and dried to obtain carboxyl-modified tungsten disulfide.

6. The method for preparing an amphiphilic Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, In S3, the mass-volume ratio of the carboxyl-modified tungsten disulfide obtained in S2, the second modifier, and the second solvent is 1g:2g:30ml, and the mass-volume ratio of the third modifier to the third solvent is 2g:30ml.

7. The method for preparing an amphiphilic Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, S3 specifically refers to: Carboxyl-modified tungsten disulfide obtained from S2 was added to 30 ml of a second solvent, then a first catalyst was added, followed by a second modifier to prepare a hydrophilic solution. Subsequently, 30 ml of a third solvent and a third modifier were added to prepare a hydrophobic solution. The mixture was stirred at 12000~13000 rpm / min for 10 min, and then stirred at 25℃ and 400~600 r / min for 24 h. After filtration, washing, and drying, Janus tungsten disulfide nano-adhesive was obtained.

8. The application of the thickener prepared by the method of preparing amphiphilic Janus tungsten disulfide nanoemulsifying thickener according to claim 7 in emulsification and thickening to improve oil recovery.

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