Amphiphilic Janus tungsten disulfide nano emulsifying tackifier as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil reservoir recovery efficiency improvement, and particularly discloses an amphiphilic Janus tungsten disulfide nano-emulsification tackifier and a preparation method and application thereof.The preparation method comprises the following steps that firstly, tungsten disulfide and a first oxidizing agent are added into a first solvent, and then tungsten disulfide with the surface modified with hydroxyl is obtained; thirdly, adding a second solvent and a first modifier, and then adding a first catalyst to obtain carboxyl modified tungsten disulfide; and finally, adding into a second solvent, and reacting with a second modifier and a third modifier to obtain the tackifying Janus tungsten disulfide nanosheet. The viscosity of the displacement front can be remarkably improved in the middle and later periods of oil reservoir development, the swept volume and the oil displacement efficiency are improved, the viscosity increasing rate of crude oil reaches 1192%, the excellent interfacial tension reducing capacity is achieved, the recovery efficiency is improved by more than 20%, and the recovery efficiency improving effect is remarkable.

Description

TECHNICAL FIELD

[0001] The application relates to the field of oil reservoir enhanced oil recovery, and in particular to a Janus tungsten disulfide nano-emulsified tackifier as well as a preparation method and application thereof. BACKGROUND

[0002] At present, most of the main oil fields in China have generally entered the late stage of high water cut development, but a considerable amount of crude oil remains in the formation in a complex form, and the remaining oil has great recoverable potential. Chemical flooding is one of the most mature enhanced oil recovery technologies at present. Conventional chemical flooding methods mainly include surfactant flooding, polymer flooding and alkali flooding. Although surfactant flooding can effectively reduce the interfacial tension, it has large adsorption loss and poor emulsion stability; polymer flooding can improve sweep efficiency, but has poor salt tolerance and temperature resistance and is prone to degradation; alkali flooding has low cost but is prone to fouling and formation damage. Therefore, an efficient recovery method is urgently needed to solve the problems of low sweep efficiency and difficult recovery of residual oil in the late stage of high water cut reservoir development.

[0003] As a newly emerging enhanced oil recovery technology in recent years, nano-fluid flooding has excellent potential for enhanced oil recovery due to its characteristics of reducing interfacial tension, adhering and peeling off crude oil, in-situ emulsification, increasing interfacial film strength, temperature resistance and salt tolerance. At the same time, by modifying the amphiphilic properties of nano materials, the interfacial activity of nano materials can be improved, so that the nano materials can spontaneously gather in the oil-water two-phase system under the action of shearing to form water-in-oil emulsion, thereby increasing the viscosity of the displacement front, reducing the mobility ratio, increasing the sweep efficiency, and adapting to more severe formation environments.

[0004] Therefore, in view of the problem of difficult recovery of crude oil in the middle and late stages of oil reservoir development, designing efficient tackifying nano materials is the key to improving the displacement efficiency of oil reservoirs. SUMMARY

[0005] The purpose of the application is to provide a Janus tungsten disulfide nano-emulsified tackifier as well as a preparation method and application thereof, which has a crude oil tackifying rate of 1192%, excellent interfacial tension reducing effect, and an enhanced oil recovery rate of more than 20%, and has a remarkable effect of improving the enhanced oil recovery rate.

[0006] To achieve the above-mentioned purpose, the application provides a preparation method of a Janus tungsten disulfide nano-emulsified tackifier, which comprises the following steps: S1, according to the proportion, tungsten disulfide and a first oxidizing agent are added to a first solvent, and then placed in an oil bath pot for heating, followed by filtration, washing and drying to obtain surface hydroxylated tungsten disulfide; S2, according to the proportion, the surface hydroxylated tungsten disulfide obtained in S1 and a first modifier are added to a second solvent, and then a first catalyst is added, heated and filtered to obtain carboxyl-modified tungsten disulfide; S3, the carboxyl modified tungsten disulfide obtained in S2, the first catalyst and the second modifier are added into a second solvent, then the third modifier is added into a third solvent, and the two solutions are mixed and heated to react and stir, washed, filtered, to obtain the Janus tungsten disulfide nano-tackifier.

[0007] Preferably, in S1, the concentration of the 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 0.4-0.6 mol / L sodium hydroxide solution.

[0008] Preferably, S1 is specifically: The tungsten disulfide and sodium persulfate are added into a sodium hydroxide solution, and continuously heated at 30-40℃ for 1h, and after washing, filtering and drying, the surface hydroxylated tungsten disulfide is obtained.

[0009] Preferably, in S2, the mass-volume ratio of the surface hydroxylated tungsten disulfide, the first catalyst, the first modifier and the second solvent is 1g: 2-3g: 1-1.2g: 30-40ml; the first catalyst is N,N'-dicyclohexyl carbodiimide, the first modifier is maleic acid, and the second solvent is dimethyl sulfoxide.

[0010] Preferably, S2 is specifically: The surface hydroxylated tungsten disulfide obtained in S1 is added into a second solvent, and then a first catalyst is added, and reacted at 25-30℃ for 12-14h, and then washed, filtered and dried, to obtain the carboxyl modified tungsten disulfide. Preferably, in S3, the mass-volume ratio of the carboxyl modified tungsten disulfide obtained in S2, the second modifier and the first catalyst is 1g: 2-2.2g: 30-40ml, and the mass-volume ratio of the third modifier and the third solvent is 2-2.3g: 30-40ml; The second modifier is sodium sulfamate; the second solvent is dimethyl sulfoxide, the first catalyst is N,N'-dicyclohexyl carbodiimide, the third solvent is n-heptane, and the third modifier is stearylamine.

[0011] Preferably, S3 is specifically: The carboxyl modified tungsten disulfide obtained in S2 is added into 30-40ml of dimethyl sulfoxide, then a first catalyst is added, and then a second modifier is added to prepare a hydrophilic solution, and then 30-40ml of n-heptane and a third modifier are added to prepare a hydrophobic solution, and stirred at 12000-13000 rpm / min for 10-15min. Then, under the conditions of 25-30℃ and 400-600r / min, the mixture is stirred to react for 24-30h, and after filtering, washing and drying, the Janus tungsten disulfide nano-tackifier is obtained.

[0012] Therefore, the application adopts the above-mentioned amphiphilic Janus tungsten disulfide nano-emulsifying tackifier, and its preparation method and application have the following beneficial effects: Compared with the prior art, the preparation method of the application uses nano-tungsten disulfide as a substrate, introduces hydroxyl groups through partial defect treatment by oxidation, and introduces hydrophilic and hydrophobic active groups through interface self-assembly under high-speed stirring to asymmetrically modify the tungsten disulfide, so that the tungsten disulfide has more outstanding interfacial activity, reduces the interfacial tension, improves the emulsifying and tackifying effect, and can effectively improve the oil reservoir recovery rate.

[0013] Compared with the prior art, the nano-emulsifying tackifier of the application can achieve a tackifying rate of 1192% without adding a surfactant, and can improve the recovery rate by more than 20%, which has a significant effect on improving the recovery rate.

[0014] Compared with conventional surfactants, the application has the characteristics of small dosage and high efficiency, and tungsten disulfide, as a natural tungsten ore, can also be artificially synthesized, has the characteristics of wide source and environmental friendliness, and can be widely used in the field.

[0015] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a synthesis schematic diagram of an embodiment of the application of the amphiphilic Janus tungsten disulfide nano-emulsifying tackifier and its preparation method and application; Figure 2 is an FT-IR characteristic curve diagram of an embodiment of the application of the amphiphilic Janus tungsten disulfide nano-emulsifying tackifier and its preparation method and application; Figure 3 is a tackifying effect diagram of different concentrations of an embodiment of the application of the amphiphilic Janus tungsten disulfide nano-emulsifying tackifier and its preparation method and application; Figure 4 is an experimental result diagram of improving the recovery rate of an embodiment of the application of the amphiphilic Janus tungsten disulfide nano-emulsifying tackifier and its preparation method and application. DETAILED DESCRIPTION

[0017] The technical solutions of the application will be further described in detail below with reference to the drawings and examples.

[0018] Unless otherwise defined, the technical terms or scientific terms used in the application should be understood as the usual meaning understood by a person skilled in the art in the field to which the application belongs.

[0019] Example 1: as Figure 1As shown, a method for preparing viscous (amphiphilic) Janus nano-tungsten disulfide is as follows: 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.

[0020] 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.

[0021] 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.

[0022] Test (1) FT-IR test 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.

[0023] 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.

[0024] Emulsification and thickening test 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. The calculation method for emulsion viscosity enhancement is shown in Formula 1 (the crude oil viscosity at 80℃ is 13.7 mPa·s); (1) 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.

[0025] Depend on Figure 3 It 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.

[0026] Enhanced oil recovery test 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.

[0027] Throughout the process, the injection end pressure, water cut, and cumulative recovery rate were recorded at every 0.05 PV injection volume, and curves of water cut, recovery rate, and injection end pressure were plotted. The formula for calculating water cut is shown in Equation (2), and the formula for calculating recovery rate is shown in Equation (3). (2) 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. (3) 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.

[0028] Results of experiments to improve oil recovery rate, such as Figure 4As 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 those 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 secondary 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.

[0029] 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.

[0030] 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 viscosifier, characterized in that, The method comprises the following steps: S1, proportionally adding tungsten disulfide and a first oxidizing agent sodium persulfate into a first solvent sodium hydroxide solution, heating and stirring, and then filtering, washing and drying to obtain surface hydroxylated tungsten disulfide; S2, proportionally adding the surface hydroxylated tungsten disulfide obtained in S1 and a first modifier maleic acid into a second solvent dimethyl sulfoxide, and then adding a first catalyst N,N'-dicyclohexyl carbodiimide, heating and filtering to obtain carboxyl modified tungsten disulfide; S3, adding the carboxyl modified tungsten disulfide obtained in S2 into a third solvent mixed solvent of n-heptane and dimethyl sulfoxide, and then reacting with a second modifier sodium sulfamate and a third modifier stearylamine under the action of the first catalyst N,N'-dicyclohexyl carbodiimide, heating and stirring, washing and filtering to obtain Janus tungsten disulfide nano emulsifying tackifier.

2. The method for preparing Janus tungsten disulfide nano-emulsifying tackifier according to claim 1, characterized in that, In S1, the concentration of the tungsten disulfide is 0.13 mol / L; The first solvent is a 0.5 mol / L sodium hydroxide solution; The first oxidizing agent is 0.07 mol / L sodium persulfate.

3. The method for preparing a Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, In S1, the tungsten disulfide and sodium persulfate are added into the first solvent, placed in an oil bath, reacted at a constant temperature of 35℃ for 1 hour, washed, filtered and dried to obtain surface hydroxylated tungsten disulfide. 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; 4. The preparation method of the Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, The first catalyst is N,N'-dicyclohexyl carbodiimide; The first modifier is maleic acid; The second solvent is dimethyl sulfoxide. In S2, the surface hydroxylated tungsten disulfide obtained in S1 is added into the second solvent and the first catalyst, and then the first modifier is added, and the mixture is continuously heated at 25℃ for 12h, and then washed, filtered and dried to obtain carboxyl modified tungsten disulfide.

5. The method of claim 1, wherein the Janus tungsten disulfide nanoemulsion viscosifier is prepared by the steps of: a) mixing a Janus tungsten disulfide nanoemulsion with a base to form a mixture; b) adding a salt to the mixture; and c) adding a surfactant to the mixture. In S3, the mass-volume ratio of the carboxyl modified tungsten disulfide obtained in S2, the second modifier and the first catalyst is 1g:2g:30ml, and the mass-volume ratio of the third modifier and the third solvent is 2g:30ml; The second modifier is sodium sulfamate; 6. The method of claim 1, wherein the Janus tungsten disulfide nanoemulsion viscosifier is prepared by the steps of: a) mixing a Janus tungsten disulfide nanoemulsion with a base to form a mixture; b) adding a salt to the mixture; and c) adding a surfactant to the mixture. The third modifier is stearylamine; The second solvent is dimethyl sulfoxide; The third solvent is 30ml n-heptane. In S3, the carboxyl modified tungsten disulfide obtained in S2 is added into 30ml of the second solvent, and then the first catalyst and the second modifier are added to prepare a hydrophilic solution, and then 30ml of a hydrophobic solution prepared from the third solvent and the third modifier is added, and the mixture is stirred at 12000-13000 rpm / min for 10min, and then stirred at 25℃ and 400-600r / min for 24h, and then filtered, washed and dried to obtain Janus tungsten disulfide nano tackifier.

8. Application of the Janus tungsten disulfide nano emulsifying tackifier in emulsifying tackifying enhanced oil recovery according to claim 7.

7. The method for preparing a Janus tungsten disulfide nanoemulsion thickener according to claim 1, characterized in that, ​ ​ ​

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