High environmental tolerance nanofluid oil displacement agent, and preparation method and application thereof

Abstract

The application discloses a kind of high environmental tolerance nanofluid oil displacement agent and its preparation method and application, it is related to oilfield additive technical field.The nanofluid oil displacement agent includes heavy alkyl benzene sulfonic acid sodium (HABS) modified molybdenum disulfide nanomaterial and heavy alkyl benzene sulfonic acid sodium (HABS) and rhamnolipid.The ultra-low interfacial tension surfactant complex system of the application can make oil-water interfacial tension reach 10 ‑3 mN / m order of magnitude at lower dosage, and can maintain excellent interfacial activity in high temperature (120 DEG C), high salt (120*10³ mg / L), high calcium ion (2000 mg / L) and wide pH range (2-12), suitable for common neutral and weak alkaline conditions of oilfield, suitable for various harsh reservoir conditions, and provides an effective technical solution for improving oil recovery.

Description

Technical Field

[0001] This invention relates to the field of oilfield additive preparation technology, specifically to a highly environmentally resistant nanofluid oil displacement agent, its preparation method, and its application. Background Technology

[0002] The research and application of nanomaterials in oil and gas exploration and development have attracted increasing attention, providing new avenues for improving the recovery rate of low-permeability reservoirs. Two-dimensional nanomaterials, exhibiting high interfacial activity through surface-to-surface contact, can autonomously adsorb and aggregate at the oil-water interface. With high specific surface area, low cost, and low toxicity, nanomaterials can easily penetrate reservoir micropores and nanopores, significantly improving recovery efficiency by adsorbing at the oil-water or rock-fluid interface, reducing interfacial tension, and altering wettability. Meanwhile, microbial enhanced oil recovery (MEOR) offers advantages such as high efficiency, biodegradability, and environmental friendliness. Its core principle is to utilize microorganisms and their metabolites (including biosurfactants, biopolymers, biogas, and biomass) to form stable oil-water emulsions, reducing interfacial tension and promoting the recovery of remaining oil.

[0003] Single biosurfactants or nanomaterials cannot achieve ultra-low interfacial tension (10). -3 The concentration of nanofluids is low (mN / m), and they have poor environmental tolerance. Nanofluid flooding is prone to problems such as nanomaterial agglomeration. Currently, multi-component compound systems are mainly used in oil recovery: Patent CN120682787A discloses a microemulsion nano-flooding agent composed of diphenyl ether gemini surfactants and nano-silica. This system is effective at 60 °C and has a salinity below 8 × 10⁻⁶ mN / m. 4While this method can stably disperse and effectively reduce interfacial tension under certain reservoir conditions (mg / L), its stability and oil displacement efficiency significantly decrease in deep, demanding reservoirs. Synthetic chemicals remaining in the reservoir (such as recalcitrant phenyl ether structures) may increase formation pollution and long-term environmental risks, making it difficult to meet the dual requirements of efficient extraction and green operations in such reservoirs. Patent CN120059708A discloses a multidimensional nanofluid oil displacement agent composed of cyclodextrin-modified magnetic carbon nanotubes, cellulose nanofibers, and molybdenum disulfide nanosheets. This system achieves ultra-low interfacial tension and improves oil recovery in indoor experiments at 80 °C. However, the multi-component, multi-step compounding and modification process involves chemical bonding processes such as silane coupling agents. In high-temperature, high-salinity environments, chemical bond hydrolysis or interfacial desorption may occur, leading to structural instability and performance degradation. The traditional synthetic surfactants and silane coupling agents used in the system are difficult to degrade in reservoirs, and long-term retention may exacerbate formation adsorption and environmental pollution risks. In addition, magnetic nano-Fe3O4 is prone to oxidation in high-salt environments, further affecting the migration and long-term effect of the oil displacement agent in micro- and nano-pore throats. Patent CN117343717A discloses an oil displacement agent prepared by stepwise grafting modification of molybdenum disulfide with alkylamines and alkylbenzene sulfonates. Although this scheme achieves basic amphiphilic modification of molybdenum disulfide, its interfacial tension can only reduce the oil-water interfacial tension from 35 mN / m to about 15 mN / m, which is difficult to achieve the ultra-low interfacial tension required for significantly reducing capillary resistance and efficiently driving residual oil. This approach mainly relies on traditional chemical modification methods. For harsh reservoirs with high temperature, high salinity, and low permeability, it lacks adaptive design and functional enhancement of materials under extreme reservoir conditions. As a result, it is difficult to meet the requirements of efficient and green exploitation of deep and complex reservoirs in terms of oil displacement efficiency, long-term stability, and environmental compatibility.

[0004] Therefore, it can be said that the oil displacement capability of nanofluids under high temperature and high salinity conditions and the environmental and economic efficiency of oil displacement agents are still challenges. Developing a new composite oil displacement system that achieves ultra-low oil-water interfacial tension and has environmental tolerance is of great significance for improving oil and gas recovery. Summary of the Invention

[0005] The purpose of this invention is to provide a highly environmentally resistant nanofluid oil displacement agent, and to provide a specific preparation method and application of the nanofluid oil displacement agent, so as to make up for the shortcomings of the prior art.

[0006] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows: A highly environmentally resistant nanofluid oil displacement agent comprising molybdenum disulfide nanomaterials modified with sodium heavy alkylbenzene sulfonate (HABS) and rhamnolipids.

[0007] In the nanofluid oil displacement agent: the mass percentage of molybdenum disulfide nanomaterial modified with sodium heavy alkylbenzene sulfonate in the final oil displacement agent is 0.01%-0.5%; the mass percentage of RL in the final oil displacement agent is 0.005%-0.1%; the mass percentage of HABS in the final oil displacement agent is 0.005%-0.1%; the mass ratio of RL to total HABS is 1:1; and the remaining solvent is water.

[0008] Furthermore, the HABS-modified molybdenum disulfide nanomaterial is specifically a molybdenum disulfide (MoS2) nanomaterial supported on sodium heavy alkylbenzene sulfonate (HABS). HABS is used to modify the surface of MoS2, and the steric hindrance and electrostatic repulsion of HABS significantly improve the dispersibility and stability of MoS2 nanosheets in solution. This nanomaterial self-assembles from a layered structure into a three-dimensional nanoflower-shaped structure, with the flower diameter concentrated between 350-600 nm. It exhibits a regular and uniform morphology and good dispersibility. Due to its ultrathin two-dimensional nanosheet morphology and nanoscale effect, it possesses excellent permeability and diffusion capabilities in the pores of ultra-low permeability reservoirs, with no risk of formation blockage and good injection performance.

[0009] Furthermore, the HABS-modified molybdenum disulfide nanomaterials are prepared through a one-step hydrothermal in-situ modification. Sodium heavy alkylbenzene sulfonate (HABS) acts as both a structure-directing agent and a surface modifier in the one-step hydrothermal reaction, reacting in situ with precursors such as sodium molybdate and thioacetamide in a reactor and self-assembling to obtain HABS-modified MoS2 nanosheets. In this process, the long alkyl chains of HABS act as hydrophobic "wedges" inserted into the interlayer space of MoS2, while the hydrophilic sulfonate heads face the aqueous phase, effectively increasing the interlayer spacing and overcoming interlayer van der Waals forces, thus promoting the exfoliation of multilayer MoS2 into ultrathin nanosheets. Simultaneously, HABS acts as a structure guide, resulting in a well-organized nanosphere structure with a particle size concentrated around 430 nm. A one-step method was used to synthesize, surface functionalize, and assemble MoS2 in the same reaction system. The resulting material has the interfacial activity of two-dimensional nanosheets and the large specific surface area and uniform surface of three-dimensional spherical structure. It also has abundant interfacial active sites and good dispersibility, which provides a structural basis for its compounding to achieve ultra-low interfacial tension.

[0010] The preparation method of the nanofluid oil displacement agent involves dispersing HABS-modified MoS2 in a rhamnolipin (RL) solution. Leveraging the excellent surface activity, biocompatibility, and salt and temperature resistance of rhamnolipin, a synergistic and stable system is formed, thereby constructing a nanofluid oil displacement agent that maintains good dispersibility, interfacial activity, and oil displacement efficiency even under high-temperature and high-salt reservoir conditions. The preparation method specifically includes the following steps: (1) Hydrothermal synthesis and in-situ modification: Molybdenum source, sulfur source and HABS (500 g / L HABS product) were dissolved in deionized water and stirred to form a homogeneous solution; the mixed solution was transferred to a high-pressure reactor and reacted at 160-200 °C for 20-40 hours; after the reaction, the product was centrifuged to obtain MoS2 nanosheet precipitate with HABS surface modification and supernatant containing HABS; (2) Biosurfactant compounding: Take 30 ml of the supernatant obtained in step (1), add 6-48 μL of RL (RL finished product 250 g / L), and sonicate (temperature: 25 ℃; time: 30 min; frequency: 40 kHz; power: 100 W) to obtain a mixed solution; (3) Nanofluid construction: The MoS2 nanosheet precipitate obtained in step (1) with a mass concentration of 0.01%-0.5% is added to the mixture obtained in step (2) and dispersed evenly by ultrasound (temperature: 25 ℃; time: 30 min; frequency: 40 kHz; power: 100 W) to obtain the nanofluid oil displacement agent.

[0011] Furthermore, in step (1), the molybdenum source is sodium molybdate dihydrate, and the sulfur source is thioacetamide; the ratio of sodium molybdate dihydrate to thioacetamide is 1:0.5-0.8 (mass ratio), and 30 mL of deionized water is added to 3-24 μL of HABS (HABS finished product 500 g / L).

[0012] Furthermore, in step (2), the mass percentage of RL in the final oil displacement agent is 0.005% - 0.1%, the mass percentage of HABS in the final oil displacement agent is 0.005% - 0.1%, and the mass ratio of RL to total HABS is 1:1.

[0013] The synergistic adsorption and alignment of the two components of the nanofluid oil displacement agent at the oil-water interface can significantly reduce the interfacial tension between the injected aqueous solution and the oil, preferably to 10. -3 It has a concentration on the order of mN / m and maintains stable interfacial activity under high temperature and high salinity reservoir conditions, exhibiting good formation adaptability and environmental compatibility.

[0014] Application of the nanofluid flooding agent in the exploitation of high-temperature and high-salinity oil reservoirs.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: (1) The ultra-low interfacial tension nanofluid oil displacement agent prepared in this invention achieves in-situ synthesis and simultaneous surface modification of MoS2 nanosheets via a one-step hydrothermal method using HABS. During the synthesis process, sodium heavy alkylbenzene sulfonate (HABS) acts not only as a surfactant but also as a key structure-directing agent. The long alkyl chains of HABS effectively suppress the random aggregation of nanosheets and improve nanodispersion stability through hydrophobic interactions and van der Waals forces. This unique multi-level structure of "two-dimensional ultrathin sheet layers constructing three-dimensional flower-shaped spheres" endows the material with a high specific surface area, abundant interfacial active sites, and increased porosity, laying a decisive structural foundation for achieving ultra-low interfacial tension and efficient oil displacement.

[0016] (2) This invention combines functionalized nanomaterials with biosurfactants, which helps reduce the cost pressure caused by excessive use of traditional biosurfactants and reduces the environmental risks that may be caused by single chemical surfactants. A low-cost, green, and efficient compound system was constructed by experimentally determining the synergistic concentration and ratio. This system achieves a highly efficient synergistic effect between the two surfactants and the nanomaterials, significantly reducing usage costs and improving economic benefits while maintaining environmental friendliness.

[0017] (3) The binary composite oil displacement system in this invention can achieve ultra-low interfacial tension without the need to add alkali, which can avoid problems such as scaling and pipeline corrosion caused by alkali.

[0018] (4) The nanofluid oil displacement agent prepared in this invention exhibits excellent environmental tolerance. Compared to the poor interfacial activity of rhamnolipin systems under harsh conditions when used alone, the introduction of functionalized molybdenum disulfide nanomaterials in combination with it significantly enhances the mechanical strength and thermodynamic stability of the interfacial film by virtue of its stable inorganic core and the unique three-dimensional nanoflower-like composite structure assembled from two-dimensional nanosheets. Through synergistic effects, this composite system can withstand high temperatures (120 ℃) ​​and high salt conditions (120 × 10⁻⁶ ℃). 3 Even at concentrations of mg / L and high calcium ions (2000 mg / L), it can still maintain a stable low interfacial tension (≤10 mg / L). -2 With a surface tension that remains stable between 27 and 29 mN / m, and excellent interfacial activity within a wide pH range (2-12), this oil displacement agent is suitable for common neutral and weakly alkaline conditions in oil fields and is applicable to a variety of harsh reservoir conditions.

[0019] (5) This invention employs a green synthesis process: the supernatant (containing residual surfactants) after synthesizing HABS-MoS2 nanosheets is recycled and reused as a dispersion medium in subsequent compounding systems. This design not only achieves waste liquid resource utilization and reduces emissions at the source, but more importantly, the residual HABS in the supernatant provides basic interfacial activity for the system, thereby significantly reducing the amount of RL used when compounded with RL. Both are derived from renewable raw materials, possess low toxicity and easy degradation characteristics, and are environmentally friendly nanofluid systems that meet the requirements of future tertiary oil recovery. Attached Figure Description

[0020] Figure 1 This is a comparison of the surface tension curves of HABS, RL and their compound systems as a function of concentration in Example 1.

[0021] Figure 2 Images are scanning electron microscope (SEM) images of MoS2 nanosheets and sodium heavy alkylbenzene sulfonate modified molybdenum disulfide (HABS-MoS2) nanomaterials; where a and b are SEM images of MoS2 nanosheets prepared in Example 2 at different magnifications; c and d are SEM images of sodium heavy alkylbenzene sulfonate modified molybdenum disulfide (HABS-MoS2) nanocomposite materials prepared in Example 3 at different magnifications, showing their nanoflower-like morphology.

[0022] Figure 3 The image shown is an EDS mapping image of HABS-MoS2 synthesized in Example 3.

[0023] Figure 4 The image shows a transmission electron microscope (TEM) image of the HABS-MoS2 nanocomposite material prepared in Example 3.

[0024] Figure 5 The infrared spectra of MoS2 and HABS-MoS2 prepared in Examples 2 and 3 are compared with those of HABS.

[0025] Figure 6 The images show a comparison of the XRD patterns of MoS2 and HABS-MoS2 prepared in Examples 2 and 3.

[0026] Figure 7 The attached figure shows a comparison of nitrogen adsorption and desorption of MoS2 and HABS-MoS2 prepared in Examples 2 and 3, with pore size distribution diagrams.

[0027] Figure 8 The nanoparticle size and dispersion stability of MoS2 and HABS-MoS2 prepared in Examples 2 and 3 are shown in the diagram.

[0028] Figure 9The figures show the interfacial tension variation curves between different solutions and simulated oil; where a represents the interfacial tension variation curves between simulated oil and different mass concentrations of HABS, RL, HABS+RL composite solutions (without HABS-MoS2 nanosheets), and HABS+RL composite solutions (containing HABS-MoS2 nanosheets); b represents the interfacial tension variation curves between simulated oil and different mass concentrations of HABS-MoS2 nanosheets after they are added to the composite fluid.

[0029] Figure 10 The first image shows a comparison of the interfacial tension between the nanofluid with the best performance in Example 4 and rhamnolipid under different salinity conditions; the second image shows a magnified view of the interfacial tension and surface tension test results of the nanofluid.

[0030] Figure 11 The first image shows a comparison of the interfacial tension between the nanofluid with the best performance in Example 4 and rhamnolipid under different calcium ion concentrations; the second image shows a magnified view of the interfacial tension and surface tension test results of the nanofluid.

[0031] Figure 12 The first image shows a comparison of the interfacial tension between the nanofluid with the best performance in Example 4 and rhamnolipid under different temperature conditions; the second image shows a magnified result of the interfacial tension and surface tension test of the nanofluid.

[0032] Figure 13 The first image shows a comparison of the interfacial tension between the nanofluid with the best performance in Example 4 and rhamnolipid under different pH conditions; the second image shows a magnified result of the interfacial tension and surface tension test of the nanofluid.

[0033] Figure 14 Figures show the contact angle test results after crude oil adsorption under different conditions; where a is the contact angle test after crude oil adsorption on the simulated oil reservoir rock surface, b is the RL at the same concentration, and c is the contact angle test figure of the quartz plate after being wetted by the nanofluid oil displacement agent in Example 4.

[0034] Figure 15 The following is a graph showing the oil washing performance test results for Example 4, where a represents the nanofluid oil displacement agent, b represents RL at the same concentration, c represents HABS-MoS2 dissolved in the supernatant, d represents HABS-MoS2 dissolved in simulated formation water, and e represents the oil washing performance test results for simulated formation water. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It is worth noting that the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0038] Example 1: The surface tension test in this embodiment was performed using a BZY-2 surface tension meter.

[0039] HABS solutions with concentrations of 100, 125, 150, 165, 175, 200, 225, 250, 325, 350, 400, 450, and 500 mg / L (20, 25, 30, 33, 35, 40, 45, 50, 65, 70, 80, 90, and 100 μL of 500 g / L finished HABS dissolved in 100 mL of deionized water), RL solutions with concentrations of 250 g / L finished rhamnolipid dissolved in 100 mL of deionized water, and their mixed solutions (fixed mass ratio of 1:1), were prepared. 500 g / L finished HABS solutions (10, 12.5, 15, and 16.5 μL of each solution) were also prepared. 17.5, 20, 22.5, 25, 32.5, 35, 40, 45, and 50 μL of glycolipin and 250 g / L of rhamnolipin product (corresponding to 20, 25, 30, 33, 35, 40, 45, 50, 65, 70, 80, 90, and 100 μL) were dissolved in 100 mL of deionized water to prepare single-component solutions of various concentrations. The surface tension of each solution as a function of concentration was measured using a surface tension meter (ring method), and logC-γ curves were plotted. The critical micelle concentration was determined by the inflection point.

[0040] like Figure 1 As shown, experiments revealed that the CMC of a single HABS solution was 325 mg / L, corresponding to a surface tension of 32.1 mN / m; the CMC of a single RL solution was 225 mg / L, corresponding to a surface tension (γ) of 30.13 mN / m. When the two were mixed at a mass ratio of 1:1 (corresponding to mole fractions α1=0.5915, α2=0.4085), the CMC of the mixed system significantly decreased to 200 mg / L, and the surface tension further decreased to 28.12 mN / m, exhibiting superior surface activity compared to either single component.

[0041] Calculations using the Clint equation show that the ideal critical micelle concentration (CMC*) for this composite system is 275.1 mg / L, and the ideal surface tension (γ*) is 31.14 mN / m. The measured CMC value (200 mg / L) is significantly lower than the CMC*, and the measured surface tension at the CMC* concentration is 28.56 mN / m, also significantly lower than γ*. This phenomenon is consistent with the Rubingh theory and the Motomura approximation model. Calculations show that the micelle interaction parameter β is negative (β≈-1.27), confirming a strong negative synergistic effect (i.e., positive synergistic effect) between HABS and RL molecules during micelleification, which is the theoretical basis for its performance improvement.

[0042] To verify the superiority of the formulation ratio described in this invention, comparative experiments were conducted. When HABS and RL were mixed at a mass ratio of 1:2, the surface tension of the system at the theoretical CMC* concentration (275.1 mg / L) was 31.2 mN / m; when HABS and RL were mixed at a mass ratio of 2:1, the surface tension of the system at the theoretical CMC* concentration (275.1 mg / L) was 32.3 mN / m, both higher than the ideal mixed surface tension γ* (31.14 mN / m). This further confirms that a 1:1 mass ratio is the optimized formulation for achieving the lowest CMC and surface tension. From the above results, it can be concluded that a 1:1 mass ratio of HABS and RL can produce a synergistic effect of "1+1>2", significantly reducing the CMC and surface tension of the system.

[0043] This embodiment demonstrates a significant synergistic effect between HABS and RL, and provides a key concentration baseline for the subsequent construction of nanofluids.

[0044] Example 2: This embodiment prepares MoS2 nanosheets via a one-step hydrothermal method: (1) Dissolve 0.6 g sodium molybdate dihydrate (Na2MoO4·2H2O) and 0.38 g thioacetamide (CH3CSNH2) in 120 mL of deionized water and stir magnetically for 30 minutes to form a homogeneous precursor solution.

[0045] (2) Transfer the above solution to a 200 mL polytetrafluoroethylene-lined high-pressure reactor and place it in a high-temperature oven at 180 °C for 30 hours.

[0046] (3) After the reaction is completed, the product is naturally cooled, washed with distilled water and ethanol, and centrifuged three times (10000 rpm, 5 min). The black precipitate (i.e. MoS2) is dried in a vacuum oven at 60 °C for 12 h to obtain the black material, i.e. MoS2.

[0047] Example 3: This embodiment prepares sodium heavy alkylbenzenesulfonate modified molybdenum disulfide nanosheets (HABS-MoS2) via a one-step hydrothermal method: (1) Add 0.6 g of sodium molybdate dihydrate (Na2MoO4·2H2O), 0.38 g of thioacetamide (CH3CSNH2), and 48 μL of sodium heavy alkylbenzene sulfonate (HABS) solution with a concentration of 500 g / L to 120 mL of deionized water. Place the mixture on a magnetic stirrer and stir continuously at room temperature for 30 minutes to ensure that all raw materials are fully dissolved and mixed evenly, so as to obtain a homogeneous and stable precursor solution. (2) Transfer the above solution to a 200 mL high-pressure reactor lined with polytetrafluoroethylene and place it in a high-temperature oven at 180 °C for 30 hours.

[0048] (3) After the reaction is completed, the product is cooled naturally and centrifuged (10,000 rpm, 5 min) to separate the black precipitate (i.e. HABS-MoS2) and the brownish-yellow supernatant, which are collected separately for later use.

[0049] (4) The black precipitate was washed with distilled water and ethanol and centrifuged three times (10,000 rpm, 5 min). It was then dried in a vacuum oven at 60 °C for 12 h to obtain the black material, namely HABS-MoS2.

[0050] The properties of MoS2 and HABS-MoS2 prepared in Examples 2 and 3 were tested and analyzed below: I. Morphological and structural characterization experiments and analysis Example 2: Morphology and structural characterization of molybdenum disulfide nanosheets (MoS2): The microstructure of the samples was observed using a scanning electron microscope (SEM, ZEISS Sigma 300, Germany) and its matching energy dispersive spectroscopy (EDS, Oxford Instruments X-Max 80), and the elemental composition was analyzed using elemental mapping. The morphology and structure were observed and confirmed using a transmission electron microscope (TEM, FEI Talos F200X G2, USA), and the crystal structure and quality were analyzed. Figure 2 (Part A, Part B) Figure 2 (Parts c and d) are SEM images of MoS2 synthesized in Example 2 and SEM images of HABS-MoS2 synthesized in Example 3, respectively. Figure 3 The image shown is an EDS mapping image of HABS-MoS2 synthesized in Example 3. Figure 4 The image shows a TEM image of HABS-MoS2 synthesized in Example 3.

[0051] like Figure 2As shown in Figure a: at low magnification, MoS2 exhibits an irregular structure, with severe particle aggregation and uneven particle size; as... Figure 2 As shown in b: At high magnification, MoS2 exhibits a lamellar structure, but the lamellars are tightly packed, lacking a regular macroscopic morphology and showing poor overall dispersion. This indicates that the growth process of pure MoS2 at 180 ℃ for 30 h lacks guidance, easily leading to aggregation and disordered morphology. Figure 2 As shown in Figure c: at low magnification, HABS-MoS2 forms a uniform nanofloral structure, with a uniform distribution and no obvious agglomeration. Figure 2 As shown in d: at high magnification, the three-dimensional nanoflower structure of HABS-MoS2 is clearly observed to be assembled from ultrathin sheets.

[0052] like Figure 4 As shown in image a (low magnification), the material exists as dispersed, sheet-like aggregates, with no dense stacking between the layers. Figure 4 As shown in b (medium magnification morphology image), ultrathin nanosheets with wrinkles and curled edges can be observed, which are typical characteristics of two-dimensional layered materials. Figure 4 As shown in c (high-resolution lattice diagram), the image shows clear lattice fringes. The interplanar spacing is measured to be approximately 0.95 nm, which is higher than the (002) interplanar spacing of 0.65 nm in the 2H phase of molybdenum disulfide. This indicates that sodium heavy alkylbenzene sulfonate molecules have successfully inserted into the interlayer of molybdenum disulfide, increasing its interlayer spacing.

[0053] II. Infrared property testing The molecular structure and chemical composition of the material—functional groups and chemical bonds—were determined using a Fourier transform infrared spectroscopy (FTIR) instrument (model IR Spirit). Figure 5 Infrared spectroscopy images of MoS2 prepared in Example 2 and HABS-MoS2 and HABS prepared in Example 3. Figure 5 In the middle, 3000 cm -1 Nearby: CH stretching vibration of alkyl chains (corresponding to the same region peak of red HABS); 1000 cm⁻¹ -1 Nearby: sulfonate group (-SO3) - The S=O stretching vibration (the core characteristic peak of the red HABS). 500 cm⁻¹ -1 The nearby fluctuations (corresponding to the low wavenumber characteristic peaks of MoS2, i.e., Mo-S stretching vibrations) confirmed that the nanoparticles simultaneously contained MoS2 and HABS, indicating successful HABS-MoS2 modification.

[0054] III. XRD Test The crystal structure information of the material was determined using an X-ray diffractometer (XRD) (Rigaku-2038, Japan). Figure 6 The XRD patterns are of MoS2 prepared in Example 2 and HABS-MoS2 prepared in Example 3. Figure 6 The presence of clear (002), (100), and (110) characteristic diffraction peaks indicates good crystal order and layered structure both before and after modification. The characteristic peaks corresponding to MoS2 show weakened intensity and broadened peak shape. This is because after HABS loading, its molecules intercalate into the MoS2 layers, interfering with the crystal stacking of MoS2, leading to reduced crystallinity and decreased order. The (002) peak shifts towards the lower 2θ direction, indicating that HABS intercalation increases the interlayer spacing of MoS2, further confirming the successful modification of MoS2.

[0055] IV. Nitrogen Adsorption and Desorption Experiments of MoS2 and HABS-MoS2 The specific surface area and pore structure of porous materials were determined using a fully automated specific surface area and porosity analyzer (BET) (model Micromeritics ASAP 2460). Figure 7 The nitrogen adsorption isotherms of MoS2 prepared in Example 2 and HABS-MoS2 prepared in Example 3, and the inset is a pore size distribution diagram. Figure 7 Both MoS2 and HABS-MoS2 nanosheets exhibited type IV adsorption-desorption isotherms and possessed an H3 hysteresis loop. The BET surface area of ​​HABS-MoS2 was 60.347 m². 2 / g, much higher than MoS2 (27.452 m 2 / g). The high surface area of ​​the ultrathin nanosheet morphology leads to a higher number of accessible active sites. This indicates that the HABS-MoS2 ultrathin nanosheets have abundant edges and active unsaturated sulfur atoms, which can significantly enhance interfacial interactions.

[0056] V. Experiments on nanoparticle size and dispersion stability of MoS2 and HABS-MoS2 The nanoparticle size and dispersion stability of MoS2 and HABS-MoS2 were determined using a nanoparticle size and ZETA potential analyzer (model Malvern Zetasizer Nano ZS90). Figure 8The nanoparticle size distributions of MoS2 prepared in Example 2 and HABS-MoS2 prepared in Example 3 are shown. Dynamic light scattering (DLS) analysis revealed that the PDI (polydispersity index) of HABS-MoS2 was 0.195, superior to the 0.249 of MoS2, where 0.1 ≤ PDI ≤ 0.25, indicating a narrower size distribution and better dispersibility after loading. This demonstrates that HABS effectively prevents the disordered and severe aggregation of nanospheres through electrostatic repulsion and steric hindrance, maintaining a relatively uniform and stable state in solution. The average hydration kinetic diameter of HABS-MoS2 in the composite solution was 292.4 nm, while that of MoS2 was 407.1 nm. The long alkyl chains of HABS act as "wedges" inserted into the interlayer of MoS2, overcoming van der Waals forces and promoting its exfoliation into thinner nanosheets. These thinner nanosheets further assemble into smaller, more loosely structured nanospheres, thus exhibiting smaller nanodiameters.

[0057] According to SEM images, HABS-MoS2 exhibits a regular flower-like structure with a diameter concentrated around 430 nm. DLS testing shows that the average hydration kinetic diameter of HABS-MoS2 in aqueous solution is 292.4 nm. The particle size measured by DLS is smaller than that observed by SEM, mainly due to: (1) DLS measures the hydrodynamic diameter of particles in solution, and its three-dimensional structure may be more compact; (2) DLS signals are more sensitive to small-sized components; (3) SEM and TEM reflect the true morphology of the sample, and their observation range is very small, while DLS testing is the calculated average particle size. These results confirm that HABS-MoS2 nanoflowers have good dispersibility and small hydrodynamic size in solution.

[0058] Example 4: In this embodiment, the above-mentioned functionalized nanomaterials are compounded with a biosurfactant system to screen the optimal dosage of HABS and RL, and based on this, a total compound system is constructed to test its core oil displacement performance.

[0059] Construction and testing of ultra-low interfacial tension nanofluid oil displacement agents: (1) Nanofluid construction: A series of HABS / RL composite nanofluids were prepared using a variable control method. The specific steps are as follows: 0.6 g of sodium molybdate dihydrate (Na2MoO4・2H2O) and 0.38 g of thioacetamide (CH3CSNH2) were added to 120 mL of deionized water in volumes of 12 μL, 24 μL, 36 μL, 48 μL, 60 μL, 72 μL, 84 μL and 96 μL of sodium heavy alkylbenzene sulfonate (HABS) solution (concentration 500 g / L). The mixture was magnetically stirred at room temperature for 30 minutes to ensure that all components were fully dissolved and mixed evenly, thus obtaining a series of homogeneous precursor solutions.

[0060] The above precursor solution was subjected to a hydrothermal reaction (the steps were the same as in Example 3 - the reaction was carried out in a high-temperature oven at 180 °C for 30 hours). After the reaction was completed, the reaction solution was taken out and, without centrifugation, rhamnolipin (RL) solution (concentration of 250 g / L) was directly added to 120 ml of the solution. According to the total surfactant concentration required by the system, 24 μL, 48 μL, 72 μL, 96 μL, 120 μL, 144 μL, 168 μL, and 192 μL of rhamnolipin solution were added respectively, so that the ratio of the added rhamnolipin to the total mass of sodium heavy alkylbenzene sulfonate initially added to the system was 1:1. Continue stirring until the system is homogeneous, and finally obtain a series of compound nanofluids with total surfactant (HABS+RL) concentrations of 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 700 mg / L and 800 mg / L (hereinafter referred to as "total compound system").

[0061] like Figure 9 As shown in Figure a, the interfacial tension between the total surfactant system and the simulated oil was measured. The results showed that the interfacial tension first decreased and then increased with increasing total concentration, reaching its lowest level (0.0076 mN / m) at 400 mg / L. At this concentration, the total surfactant system contained 48 μL of HABS (including free HABS in the supernatant and HABS loaded with MoS2), 96 μL of HABS-MoS2 that had not been centrifuged and dissolved in the solution. The above study determined that the system's interfacial performance was optimal at a total surfactant concentration of 400 mg / L. However, at this concentration, nanoparticles were not separated by centrifugation, and excessive addition of nanoparticles could easily antagonize the surfactant, leading to a decrease in the interfacial control effect. Further optimization is needed to determine the extent of the reduction in interfacial tension and the required concentration of nanoparticles to achieve ultra-low oil-water interfacial tension.

[0062] Preparation of the compound base solution: 30 mL of supernatant (0.6 g Na₂MoO₄·2H₂O, 0.38 g CH₃CSNH₂, 48 μL, 500 g / L HABS, dissolved in 120 mL deionized water, reacted in a high-temperature oven at 180 °C for 30 hours) was measured. To continue the validated optimized concentration design, RL was added to maintain the mass ratio of the added RL to the initial feed (48 μL, 500 g / L) of total HABS at 1:1 (i.e., adding 96 μL of RL solution with a concentration of 250 g / L). At this point, the RL mass concentration was 0.02 wt%.

[0063] Construction of a series of nanofluids: Centrifuged and dried HABS-MoS2 nanoparticles were added to the above-mentioned compound base solution, and their mass fractions in the final system were controlled to be 0 wt% (control), 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, and 0.4 wt%. After uniform dispersion by ultrasound (temperature: 25 ℃; time: 30 min; frequency: 40 kHz; power: 100 W), a series of nanofluids were obtained for subsequent performance evaluation.

[0064] (2) Interfacial tension performance test: The interfacial tension test in this embodiment was performed using a TX500C rotating drop interfacial tension meter.

[0065] Using a rotating drop interfacial tensiometer, at 80 °C, No. 0 diesel oil (viscosity 2.9598 mPa·s at 80 °C) was used as a simulated oil to test the interfacial tension between various nanofluids and the simulated oil. For example... Figure 9 As shown: Without the addition of nanosheets, the interfacial tension of the compound surfactant system is approximately 0.78 mN / m; when 0.1 wt% HABS-MoS2 is added, the interfacial tension drops to a minimum value of 2.4 × 10⁻⁶ within three minutes. -3 The interfacial tension remained stable for two hours without fluctuation, with a reduction of over 99.9%, achieving ultra-low interfacial tension.

[0066] Example 5: This embodiment aims to verify the adaptability of the constructed nanofluid under harsh reservoir conditions.

[0067] I. Environmental tolerance test of nanofluid displacement agent: Based on the performance test results of Example 4, the nanofluid with the best interfacial tension was selected as the test object. The fluid contained 30 ml of supernatant, 0.02 wt% RL and 0.1 wt% HABS-MoS2 nanomaterials.

[0068] like Figure 10As shown, the salt tolerance test procedure is as follows: Take a sample of the compound displacement agent with a fixed formulation, add NaCl, and prepare a series of samples with salinity (calculated as NaCl) increasing in gradients of 0, 20,000, 40,000, 60,000, 80,000, 100,000, and 120,000 mg / L; stir evenly using a magnetic stirrer (model HMS-203D, speed 550 rpm); use a rotating drop interfacial tensiometer (80 ℃, 8000 rpm) to measure the equilibrium interfacial tension between each sample and the simulated oil, and simultaneously use a surface tensiometer to measure the surface tension of the solution. This is used to evaluate the salt tolerance of the displacement agent formulation.

[0069] like Figure 11 As shown in the figure, the calcium ion resistance test steps are as follows: Take the compound oil displacement agent sample with a fixed formulation, add CaCl2, and prepare Ca... 2+ Samples with concentrations of 0, 500, 1000, 1500, and 2000 mg / L were stirred uniformly using a magnetic stirrer (HMS-203D) at 550 rpm. The equilibrium interfacial tension between each sample and the simulated oil was measured using a rotating drop interfacial tensiometer (80 ℃, 8000 rpm), and the surface tension of the solution was measured using a surface tensiometer. This was used to evaluate the calcium resistance of the oil displacement agent formulation.

[0070] like Figure 12 As shown in the figure, the temperature resistance test procedure is as follows: Samples of the compounded oil displacement agent with a fixed formulation were taken and sealed in 25 mL high-pressure reactors lined with polytetrafluoroethylene. The samples were placed in a high-temperature oven, and six different treatment temperatures were set: 60 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, and 120 ℃. The samples were kept at each target temperature for 24 hours. After treatment, the equilibrium interfacial tension between each sample and the simulated oil was measured using a rotating drop interfacial tensiometer (80 ℃, 8000 rpm), and the surface tension of the solution was measured using a surface tensiometer. This was used to evaluate the thermal stability of the oil displacement agent formulation.

[0071] like Figure 13As shown in the figure, the pH resistance test procedure is as follows: A fixed-formulation oil displacement agent sample was taken and its pH value was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 respectively using 1 mol / L HCl and 1 mol / L NaOH solutions, monitored by a pH meter (FiveEasy Plus FE28), thus preparing a series of pH samples. Each sample was thoroughly stirred using a magnetic stirrer (HMS-203D, 550 rpm), and the equilibrium interfacial tension between it and the simulated oil was measured using a rotating drop interfacial tensiometer (80 ℃, 8000 rpm). Simultaneously, the surface tension of the solution was measured using a surface tensiometer to comprehensively evaluate the pH resistance of the oil displacement agent.

[0072] II. Environmental tolerance test of rhamnolipid solution: A 400 mg / L rhamnolipid solution was used as the test subject.

[0073] like Figure 10 As shown, a 400 mg / L rhamnolipid solution was taken, and NaCl was added to prepare a series of samples with salinity (calculated as NaCl) increasing in a gradient of 0, 20,000, 40,000, 60,000, 80,000, 100,000, and 120,000 mg / L. The samples were stirred evenly using a magnetic stirrer (model HMS-203D, speed 550 rpm). The equilibrium interfacial tension between each sample and the simulated oil was measured using a rotating drop interfacial tensiometer (80 ℃, 8000 rpm).

[0074] like Figure 11 As shown, a 400 mg / L rhamnolipid solution was taken, and CaCl2 was added to prepare Ca... 2+ Samples with concentrations of 0, 500, 1000, 1500, and 2000 mg / L were stirred uniformly using a magnetic stirrer (HMS-203D) at 550 rpm. The equilibrium interfacial tension between each sample and the simulated oil was measured using a rotating drop interfacial tensiometer (80 ℃, 8000 rpm).

[0075] like Figure 12 As shown, 400 mg / L rhamnolipid solution was taken and sealed in a 25 mL polytetrafluoroethylene-lined high-pressure reactor. The samples were placed in a high-temperature oven and six different treatment temperatures were set: 60 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, and 120 ℃. The samples were kept at each target temperature for 24 hours. After treatment, the equilibrium interfacial tension between each sample and the simulated oil was measured using a rotating drop interfacial tensiometer (80 ℃, 8000 rpm).

[0076] like Figure 13As shown, a 400 mg / L rhamnolipid solution was prepared, and its pH was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 respectively using 1 mol / L HCl and 1 mol / L NaOH solutions, monitored by a pH meter (FiveEasy Plus FE28), thus preparing a series of pH samples. Each sample was thoroughly stirred with a magnetic stirrer (HMS-203D, 550 rpm), and the equilibrium interfacial tension between the sample and the simulated oil was measured using a rotating drop interfacial tensiometer (80 ℃, 8000 rpm). Figure 10-13 Within the wide range of salinity conditions described above, the surface tension of the nanofluid remained stable between 27 and 29 mN / m, and its interfacial tension with the simulated oil also remained at 10 mN / m. -2 The concentration was in the lower order of mN / m, without a significant increase, which was significantly better than 400 mg / L rhamnolipid solution (interfacial tension was generally in the range of 10). 0 10 -1 The nanofluid exhibits an interfacial tension of 0.0024 mN / m in common oil reservoirs (pH=6-8), and maintains excellent levels of 0.13 mN / m and 0.037 mN / m under strong acid (pH=2) and strong alkali (pH=12) conditions, respectively. This indicates that its active components can be effectively adsorbed at the oil-water interface in various acidic and alkaline environments. In contrast, rhamnolipids exhibit high interfacial tension in the neutral region (pH=6-8), meaning their activity is weak under most real oil reservoir conditions. This is due to the characteristics of its carboxylate head group: it protonates and loses activity under acidic conditions, has the lowest solubility and activity near neutral, and recovers somewhat under alkaline conditions but easily forms soap scum.

[0077] The compound solution contains HABS (sulfonate), whose head group is less sensitive to pH than that of carboxylate. At the same time, HABS-MoS2 nanosheets act as a stable support, protecting the rhamnolipids in the compound solution and enabling them to maintain their conformation and function under a wide range of pH and mineralization conditions.

[0078] The nanofluid oil displacement agent prepared in this invention exhibits excellent resistance to salt, temperature, and acids and alkalis. Real oil reservoirs have diverse pH conditions, often existing in neutral and weakly alkaline environments. This oil displacement agent formulation eliminates the need for cumbersome pH adjustment pretreatment for specific reservoirs and is applicable to various reservoirs with different salinity and high temperatures, demonstrating wider applicability and higher reliability. This indicates its good application potential and stability in complex and harsh real-world oil reservoir environments.

[0079] Example 6: Contact angle test of a highly environmentally resistant nanofluid oil displacement agent: Two clean quartz plates (square, 25 mm long * 25 mm wide * 1 mm thick) were immersed in a crude oil and kerosene mixture (viscosity 2.37 mPa·s at 60 °C) at a mass ratio of 1:3 at 60 °C. They were then aged in a high-temperature oven at 60 °C for 48 h to simulate the state of the oil reservoir rock surface after adsorption of crude oil. After removal, the surface was wiped clean with lens paper to remove free oil stains, and the contact angle with water was measured to be 74.7°. Figure 14 a) to form a weakly hydrophilic reference surface.

[0080] The aged quartz plate was immersed in the comparative sample (400 mg / L rhamnolipin solution) and statically placed at 60 °C for 24 hours. After removal, the surface was wiped clean with lens paper to remove free solution, and after drying, its contact angle with water was measured to be 76°. Figure 14 (b) This data indicates that the wettability of the rock surface did not change substantially after the comparative sample treatment.

[0081] Another aged quartz plate was immersed in the compound oil displacement agent described in this invention (containing 30 ml of supernatant, 0.02 wt% RL and 0.1 wt% HABS-MoS2 nanomaterials) and statically placed at 60 °C for 24 hours. After removal, the surface was wiped clean with lens paper to remove free solution, and after drying, its contact angle with water was measured to be 34.8°. Figure 14 c).

[0082] Under identical simulated reservoir conditions and processing procedures, the compound displacement agent provided by this invention can efficiently reduce the contact angle of the aged crude oil rock surface from 74.7° to 34.8°, achieving a clear reversal to a strongly hydrophilic state; while the conventional rhamnolipid solution in contrast does not exhibit this significant effect (contact angle 76°). This property indicates that the displacement agent of this invention can effectively alter the wettability of reservoir rocks, facilitating the driving of crude oil in pores and providing a key mechanism for improving oil recovery.

[0083] Example 7: Oil washing performance test of a highly environmentally resistant nanofluid oil displacement agent: Crude oil (viscosity 90.27 mPa·s at 60 ℃) was mixed with quartz sand of different mesh sizes at a mass ratio of 1:5 and aged in a high-temperature oven at 60 ℃ for 48 h. The mixture was then placed in a wash bottle, and the density of the crude oil (0.855 g / cm³) was measured. The aged oil sand (dry weight approximately 15.0 g) was placed in the wash bottle, and 30 mL of a compound solution (containing 30 mL of supernatant, 0.02 wt% RL, and 0.1 wt% HABS-MoS2 nanomaterials) was added. The mixture was shaken at 90 rpm and 60 ℃ for 2 h. The wash bottle was then removed, and the appropriate concentration of the compound solution was added to the top mark. The mixture was shaken well and then placed in a 60 ℃ incubator for another 2 h of incubation. Figure 15 As shown, the volume of washed oil was recorded. A control group was also set up, consisting of a 400 mg / L RL solution, 0.1 wt% HABS-MoS2 dissolved in the supernatant, and 0.1 wt% HABS-MoS2 dissolved in simulated formation water (mineralization: 4454.51 mg / L). The mass of aged oil sands and the volume of washed oil were recorded in the simulated formation water. Compared with the control group (RL washing efficiency was 22.23%), the volume of washed oil was recorded. Figure 15 b) The oil washing efficiency of HABS-MoS2 dissolved in the supernatant is 56.43% ( Figure 15 c), the oil washing efficiency of HABS-MoS2 dissolved in simulated formation water was 6.84% ( Figure 15 d). The simulated formation water washing oil efficiency was 5.13% ( Figure 15 e) Compared to the experimental group (washing efficiency 82.76%), Figure 15 a) The oil washing efficiency was significantly improved. The results indicate that the compound solution has excellent oil washing performance and shows promise for improving oil recovery.

[0084] In summary, this invention provides a nanofluid oil displacement agent with both ultra-low interfacial tension and high environmental tolerance, prepared through a one-step hydrothermal in-situ modification. Its innovation lies in utilizing HABS as both a morphology-directing agent and a surface modifier during synthesis to successfully prepare HABS-MoS2 nanoflora with regular morphology, large specific surface area, uniform size, and good dispersibility. Furthermore, it is compounded with the green biosurfactant rhamnolipid (RL), leveraging their significant molecular synergistic effect to construct a stable nanofluid system. This oil displacement agent can stably reduce the oil-water interfacial tension to 10. -3 The value is on the order of mN / m, and it is also suitable for high temperature (120 ℃) ​​and high salinity (120×10⁻⁶ mN / m). 3This oil displacement agent remains stable even at concentrations of mg / L and high calcium ions (2000 mg / L), and maintains excellent interfacial activity over a wide pH range (2-12), making it suitable for common neutral and weakly alkaline conditions in oilfields. It is applicable to various harsh reservoir conditions. The process described in this invention is simple and efficient, achieving simultaneous synthesis, modification, and functionalization, providing a reliable technical solution for the efficient development of harsh reservoirs such as high-temperature and high-salinity reservoirs.

[0085] The preferred embodiments of the present invention have been described in detail above, and are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A highly environmentally resistant nanofluid oil displacement agent, characterized in that, The nanofluid oil displacement agent comprises molybdenum disulfide nanomaterials modified with sodium heavy alkylbenzene sulfonate (HABS), sodium heavy alkylbenzene sulfonate (HABS), and rhamnolipid.

2. The nanofluid oil displacement agent as described in claim 1, characterized in that, In the nanofluid oil displacement agent: the mass percentage of molybdenum disulfide nanomaterial modified with sodium heavy alkylbenzene sulfonate in the final oil displacement agent is 0.01%-0.5%; the mass percentage of RL in the final oil displacement agent is 0.005%-0.1%; the mass percentage of HABS in the final oil displacement agent is 0.005%-0.1%; and the remaining solvent is water.

3. The nanofluid oil displacement agent as described in claim 2, characterized in that, The mass ratio of RL to total HABS is 1:

1.

4. The nanofluid oil displacement agent as described in claim 1, characterized in that, The HABS-modified molybdenum disulfide nanomaterial is specifically molybdenum disulfide (MoS2) nanomaterial supported by sodium heavy alkylbenzene sulfonate HABS. HABS is used to modify the surface of MoS2, and the steric hindrance and electrostatic repulsion of HABS are used to improve the dispersibility and stability of MoS2 nanosheets in solution. The nanomaterial is formed by the self-assembly of a layered structure into a three-dimensional nanoflower-shaped structure, with the diameter of the flower-shaped structure concentrated between 350-600 nm. It has a regular and uniform morphology and good dispersibility.

5. The nanofluid oil displacement agent as described in claim 1, characterized in that, The HABS-modified molybdenum disulfide nanomaterials were prepared by in-situ modification via a one-step hydrothermal method. Sodium heavy alkylbenzene sulfonate (HABS) acted simultaneously as a structure directing agent and surface modifier in the one-step hydrothermal reaction, reacting in-situ with precursors such as sodium molybdate and thioacetamide in a reactor and self-assembling to obtain HABS-loaded and modified MoS2 nanosheets.

6. The preparation method of the nanofluid oil displacement agent according to claim 1, characterized in that, HABS-modified MoS2 was dispersed in a rhamnolipid RL solution to form a synergistic stable system, thereby constructing a nanofluid oil displacement agent that still has good dispersibility, interfacial activity and oil displacement efficiency under high temperature and high salinity reservoir conditions.

7. The preparation method of the nanofluid oil displacement agent according to claim 6, characterized in that, The preparation method specifically includes the following steps: (1) Hydrothermal synthesis and in-situ modification: Molybdenum source, sulfur source and HABS were dissolved in deionized water and stirred to form a homogeneous solution; the mixed solution was transferred to a high-pressure reactor and reacted at 160-200 °C for 20-40 hours; after the reaction, the product was centrifuged to obtain MoS2 nanosheet precipitate with HABS modified surface and supernatant containing HABS; (2) Biosurfactant compounding: Take the supernatant obtained in step (1), add RL to it, and mix it evenly by ultrasonication to obtain a mixture; (3) Nanofluid construction: The MoS2 nanosheet precipitate obtained in step (1) with a mass concentration of 0.01%-0.5% is added to the mixture obtained in step (2) and dispersed evenly by ultrasonication to obtain the nanofluid oil displacement agent.

8. The preparation method of the nanofluid oil displacement agent according to claim 7, characterized in that, In step (1), the molybdenum source is sodium molybdate dihydrate, and the sulfur source is thioacetamide; the mass ratio of sodium molybdate dihydrate to thioacetamide is 1:0.5-0.

8.

9. The preparation method of the nanofluid oil displacement agent according to claim 7, characterized in that, In step (2), the mass percentage of RL in the final oil displacement agent is 0.005% - 0.1%, the mass percentage of HABS in the final oil displacement agent is 0.005% - 0.1%, and the mass ratio of RL to total HABS is 1:

1.

10. The application of the nanofluid flooding agent according to claim 1 in the exploitation of high-temperature and high-salinity oil reservoirs.

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