Mesoporous nanofluid oil displacement system and preparation method and application thereof

Abstract

The application discloses a mesoporous nanofluid oil displacement system and a preparation method and application thereof. The oil displacement system comprises a graphene-silica hybrid mesoporous nanomaterial, a hydrophobic associating polymer and prepared water; wherein the graphene-silica hybrid mesoporous nanomaterial comprises a mesoporous silica substrate and a graphene layer in-situ grown on the surface and / or in the pores of the substrate by a chemical vapor deposition method. The oil displacement system has excellent interfacial activity, tackiness and microscopic oil displacement capacity, can effectively change rock wettability and expand swept volume, and has an oil displacement efficiency of more than 35% under high-temperature and high-salt reservoir conditions, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to a mesoporous nanofluid oil displacement system, its preparation method and application, belonging to the field of chemical oil displacement technology in oilfield development. Background Technology

[0002] With the continued growth of global energy demand and the general entry of onshore oilfields into the later stages of high water-cut development, the efficient development of reservoirs with complex conditions such as high temperature and high salinity has become crucial to ensuring energy security. Traditional chemical flooding technologies such as polymer flooding face technical bottlenecks in high-temperature and high-salinity environments, including thermal degradation of polymer molecular chains, low viscosity retention, and a sharp decline in oil displacement efficiency.

[0003] Nanomaterials, with their advantages of small size, large specific surface area, and high surface activity, offer new pathways for enhanced oil recovery (EOR) technologies. Among them, silica nanoparticles possess good surface modifiability and environmental compatibility, but their use alone suffers from problems such as easy aggregation and instability under high temperature and high salinity conditions, and limited functionality. Dendritic mesoporous nanomaterials, possessing both dendritic structure and mesoporous characteristics, have attracted widespread attention in the field of EOR in recent years. Graphene-based materials have also garnered significant attention in recent years due to their unique two-dimensional sheet structure and excellent mechanical properties. Combining graphene with silica can create hybrid nanomaterials with complementary properties. However, in current technologies, the application of graphene-silica hybrid materials in oil displacement is mostly concentrated on simple physical mixing or loading, failing to fully utilize the synergistic effect between the interfacial activity of graphene and the mesoporous structure of silica. Further research is needed on the long-term stability under extreme reservoir conditions, the regulation of interfacial activity, and the targeted driving mechanism for various residual oils (especially film-like and blind-end oils).

[0004] Therefore, developing a novel nanomaterial with an efficient synthesis route that can simultaneously achieve strong interfacial activity and excellent temperature and salt resistance, and constructing a synergistic oil displacement system with polymers, has important theoretical value and application prospects for overcoming the challenge of improving oil recovery in high-temperature and high-salinity reservoirs. Summary of the Invention

[0005] The purpose of this invention is to provide a mesoporous nanofluidic oil displacement system. A graphene-silica hybrid nanomaterial with a mesoporous structure and high interfacial activity was prepared by combining a bicontinuous microemulsion method with vapor deposition. This material combines the high interfacial activity of graphene with the structural stability of the silica mesoporous framework. When introduced into a polymer flooding system, it can simultaneously exert multiple synergistic effects as an "interfacial surfactant" (reducing interfacial tension and reversing wettability), a "physical crosslinking point" (enhancing the viscoelasticity of the polymer network), and a "microscopic carrier" (deeply penetrating blind-end pores for oil displacement), thereby achieving efficient oil displacement under extreme reservoir conditions.

[0006] The present invention first provides a graphene-silica hybrid mesoporous nanomaterial, comprising a mesoporous silica substrate and a graphene layer grown in situ on the surface and / or in the pores of the substrate by chemical vapor deposition. The specific surface area of ​​the graphene-silica hybrid mesoporous nanomaterial is higher than that of the mesoporous silica substrate. The surface roughness of the graphene-silica hybrid mesoporous nanomaterial is greater than that of the mesoporous silica substrate.

[0007] The present invention also provides a method for preparing the graphene-silica hybrid mesoporous nanomaterial, comprising the following steps: Mesoporous silica substrates were prepared by a bicontinuous microemulsion method. The mesoporous silica substrate is placed in a reactor and heated under a reducing atmosphere. Then, a carbon source gas is introduced for chemical vapor deposition to grow the graphene layer in situ on the surface and / or in the pores of the mesoporous silica substrate, thereby obtaining the graphene-silica hybrid mesoporous nanomaterial. The chemical vapor deposition conditions are as follows: the mesoporous silica substrate is heated to 500-700°C in a hydrogen atmosphere and held at that temperature for 20-40 minutes; then acetylene gas is introduced for deposition; after deposition, the substrate is cooled to room temperature in a protective atmosphere.

[0008] Preferably, the bicontinuous microemulsion method includes the following steps: The template agent and catalyst were dissolved in water and stirred to form a transparent solution; then the silicon source and oil phase were added and stirred to form a microemulsion; then the co-solvent was added and stirred to stabilize the microemulsion; the temperature was raised to the reaction temperature and stirred to react; the reaction product was centrifuged, washed, dried and calcined to obtain the mesoporous silica substrate.

[0009] Preferably, the template agent is selected from one or more of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecylpyridine bromide, and hexadecylpyridine chloride, and is more preferably hexadecyltrimethylammonium bromide; the amount of the template agent is 2-6 wt.%, preferably 3-5 wt.%, and more preferably 4 wt.%. The catalyst is selected from one or more of ammonia, urea, methylamine, n-propylamine, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, ethanolamine, formamide, and acetamide, preferably urea; the amount of the catalyst is 2-5 wt.%, preferably 3-4 wt.%, more preferably 3.4 wt.%; The silicon source is tetraethyl orthosilicate (TEOS), and its dosage is 5-30 wt.%, preferably 10-25 wt.%, and more preferably 15 wt.%. The oil is relative to xylene; The co-solvent is selected from one or more of methanol, ethanol, ethylene glycol, isopropanol, n-butanol, n-pentanol, and octanol, preferably n-pentanol; the amount of the co-solvent is 3-8 wt.%, preferably 4-6 wt.%, and more preferably 5 wt.%. The reaction temperature is 70-80℃, preferably 72-78℃, and more preferably 75℃; The reaction time is 1-12 h, preferably 5-8 h, and more preferably 6 h; The stirring speed is 1000-3000 r / min, preferably 1500-2500 r / min, and more preferably 2000 r / min; The calcination temperature is 500-600℃, and the calcination time is 4-8 h.

[0010] Based on the graphene-silica hybrid mesoporous nanomaterial, the present invention further provides a mesoporous nanofluid oil displacement system, comprising the graphene-silica hybrid mesoporous nanomaterial, a hydrophobic associating polymer, and formulated water; In the mesoporous nanofluidic oil displacement system, the mass concentration of the graphene-silica hybrid mesoporous nanomaterial is 0.01%-0.2%, preferably 0.1%-0.15%, and more preferably 0.13%. And / or, the mass concentration of the hydrophobic associative polymer is 1000-2000 mg / L, preferably 1200-1800 mg / L, and more preferably 1500 mg / L.

[0011] The hydrophobic associative polymer is prepared by free radical polymerization of monomer raw materials including acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA) and hydrophobic monomers. Preferably, the molar ratio of the acrylamide, the 2-acrylamido-2-methylpropanesulfonic acid, and the acrylic acid is (80-90):(3-8):(5-15), more preferably 84.5:5:10; Preferably, the hydrophobic monomer accounts for 0.3%-1.0% of the total mass of the monomer raw materials, more preferably 0.5%; Preferably, the hydrophobic monomer is selected from acrylate hydrophobic monomers with a carbon chain length of C8-C18, and more preferably, it is methacryloyloxyethyltetradecyldimethylammonium chloride (C14MAC).

[0012] The present invention also provides a method for preparing the mesoporous nanofluidic oil displacement system, comprising the following steps: A monomeric raw material containing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and a hydrophobic monomer is dissolved in water and subjected to free radical polymerization under the action of an initiator to obtain a hydrophobic associative polymer. The graphene-silica hybrid mesoporous nanomaterial is dispersed in the prepared water and subjected to ultrasonic treatment to obtain a nano-suspension. The hydrophobic associative polymer is then added to the nano-suspension and stirred until completely dissolved to obtain the mesoporous nanofluid oil displacement system.

[0013] Preferably, the total mass fraction of monomers in the monomer raw material is 20-35%, more preferably 25-30%, and even more preferably 27%. Preferably, the initiator is azobisisobutyramidine hydrochloride, with a mass fraction of 0.01-0.05%, more preferably 0.02-0.04%, and even more preferably 0.03%. The free radical polymerization reaction is carried out at 5-30°C, preferably 10-20°C, and more preferably 15°C; The free radical polymerization reaction takes 2-6 hours, preferably 3-5 hours, and more preferably 4 hours.

[0014] The graphene-silica hybrid mesoporous nanomaterial and mesoporous nanofluid oil displacement system of the present invention can be used in the field of chemical oil displacement in oilfields, especially in enhancing oil recovery in high-temperature and high-salinity reservoirs. A water flooding step can be performed before, after or simultaneously with the injection of the mesoporous nanofluid oil displacement system.

[0015] Technical features and beneficial effects of the present invention: 1. The mesoporous nanomaterials of this invention have controllable particle size, uniform particle size distribution, excellent monodispersity, and high specific surface area. The surface exhibits a mesoporous structure coated with graphene sheets, with radially ordered distribution of mesopores. The pore size ranges from 2 to 8 nm, the pore entrances are open and their diameter is larger than the average pore size, and the pore connectivity and permeability are good, providing ample space for functional purposes.

[0016] 2. Graphene is grown in situ through vapor deposition and chemically bonded to the mesoporous framework of silica. This not only inhibits the stacking of graphene sheets but also avoids the collapse of silica mesopores. Compared with single mesoporous silica, the specific surface area of ​​the hybrid material is increased, the surface roughness is significantly increased, and the structural stability in high temperature and high salt environment is greatly enhanced, making it less prone to agglomeration and deactivation.

[0017] 3. The material combines the high interfacial activity of graphene with the abundant active sites of silica. Numerous silanol functional groups and oxygen-containing functional groups on the surface form strong hydrogen bonds and hydrophobic interactions with the amide and sulfonic acid groups of the polymer PCAS, significantly enhancing the polymer's three-dimensional network structure. This increases the apparent viscosity of the composite system from 30.1 mPa·s to 45.6 mPa·s, effectively adapting it to high-temperature and high-salinity oil reservoir environments.

[0018] 4. The material's high specific surface area and special surface structure significantly enhance the rock surface's adsorption capacity, enabling oil-wet rocks to quickly reverse into strongly water-wet rocks, with the contact angle between the core and crude oil reaching up to 121°. It significantly weakens oil-rock adhesion and efficiently removes film-like residual oil.

[0019] 5. The mesoporous nanofluid flooding system has both excellent oil washing efficiency and sweep capacity. Core displacement experiments show that its oil displacement efficiency can reach 35.1%, which is 24.4 percentage points higher than that of unhybridized mesoporous nanomaterial flooding. It can effectively activate the residual oil in the blind end pores and significantly expand the sweep volume of the flooding system, providing an efficient technical solution for improving the recovery rate of high-temperature and high-salinity oil reservoirs. Attached Figure Description

[0020] Figure 1 The contact angle of the core samples after treatment with the nanofluid oil displacement agent in Examples 1-6 and Comparative Example 3 of this invention. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0022] Example 1: Preparation of the mesoporous nanofluidic oil displacement system is as follows: 4 g of hexadecyltrimethylammonium bromide and 3.4 g of urea were added to 100 mL of deionized water and placed in a three-necked flask. The mixture was stirred at room temperature for 30 minutes to form a transparent liquid. Then, 15 mL of tetraethyl orthosilicate and 100 mL of p-xylene were mixed and added dropwise to the flask. The mixture was stirred at 2000 r / min for 30 minutes. 5 mL of n-pentanol was added dropwise, and the mixture was stirred for 30 minutes to stabilize the microemulsion. The temperature was raised to 75 °C and stirred for 6 hours. After cooling, the product was centrifuged for 15 minutes, washed 3-5 times alternately with water and ethanol, dried under vacuum, and then heated to 550 °C and held for 6 hours to obtain pure mesoporous silica (DMS). The DMS was then placed in a tube furnace and heated to 600 °C under H2 and held for 30 minutes. Acetylene was introduced, and the mixture was cooled to room temperature under N2 protection to obtain graphene-silica hybrid mesoporous nanomaterials (FMSTNs).

[0023] Weigh 27 g of AM, AMPS, AA (molar ratio 84.5:5:10), and 0.5% methacryloyloxyethyltetradecyl dimethylammonium chloride, dissolve in deionized water, and place in a three-necked flask. Place the three-necked flask in a water bath and purge with N2. After heating the water bath to 15 °C, add 0.03% of the initiator azobisisobutyramidine hydrochloride. Seal the three-necked flask and react for 4 hours. After the reaction is complete, remove the resulting transparent colloid, cut it into small pieces, and soak it in anhydrous ethanol to dehydrate and precipitate. Dry the solid precipitate and granulate to obtain the polymer product PCAS.

[0024] The obtained functionalized graphene-silica hybrid mesoporous nanomaterials (FMSTNs) were added to deionized water and ultrasonically dispersed for 45 minutes to prepare a nano-suspension with a mass concentration of 0.13 wt.%. Then, the obtained polymer PCAS was added to the suspension and stirred until completely dissolved to obtain a 1500 mg / L graphene-silica hybrid mesoporous nanofluidic oil displacement system.

[0025] Example 2 As described in Example 1, except that the amount of template agent used is 3%.

[0026] Example 3 As described in Example 1, the different reaction time is 5 hours.

[0027] Example 4 As described in Example 1, except that the catalyst used is ethylenediamine.

[0028] Example 5 As described in Example 1, except that the co-solvent used is n-butanol.

[0029] Example 6 As described in Example 1, except that the amount of co-solvent used is 6%.

[0030] Example 7 As described in Example 1, except that the amount of tetraethyl orthosilicate used is 20%.

[0031] Example 8 As described in Example 1, except that the stirring speed used was 2500 r / min.

[0032] Comparative Example 1 As described in Example 1, the difference is that no graphene-silica hybrid nanomaterials are added to the oil displacement system, and only a 1500 mg / L polymer PCAS solution is prepared.

[0033] Comparative Example 2 Han Jia et al., in their paper "Han Jia, Juan He, Yingbiao Xu, et al. Synthesis of hybriddendritic mesoporous silica titanium nanoparticles to stabilize Pickering emulsions for enhanced oil recovery[J]. Colloids and Surfaces A:Physicochemical and Engineering Aspects, 2021, 628, 127237," successfully prepared hybrid dendritic mesoporous silica titanium nanoparticles and investigated their potential applications for stabilizing Pickering emulsions. The tertiary oil recovery rate was increased by 14.05%.

[0034] Comparative Example 3 As described in Example 1, the difference is that hybrid nanomaterials are not used in the oil displacement system; only a solution of unhybridized mesoporous nanomaterials is used.

[0035] Examples 1-6, Comparative Experiment 3: Contact Angle Comparison of Mesoporous Nanomaterials Contact angle analysis was performed on the graphene-silica hybrid mesoporous nanomaterials in the examples, using a mineralization of 2.0 × 10⁻⁶. 5 Add mg / L of mineralized water to the nanofluid oil displacement agents synthesized in Examples 1-6 and Comparative Example 3 of this invention, respectively. After aging at 130°C for 9 hours, the contact angles were measured using a contact angle meter at 20°C. The experimental results are as follows: Figure 1 As shown.

[0036] As can be seen from the figure, after 9 hours, the contact angles of the core samples treated with the nanofluid oil displacement agent in Examples 1-6 and Comparative Example 3 were all between 80-130°. The core sample treated with the oil displacement system provided in Example 1 had the largest contact angle, at 121°. This is mainly because the graphene-silica hybrid mesoporous nanomaterial has a higher specific surface area, pore volume, and surface roughness of 1124.43 μm. 2 / g, 1.904 cm 3 / g and 29.3μm (Table 1), thus significantly increasing the contact angle of the oil phase in the core.

[0037] Table 1 Properties of Nanomaterials

[0038] Example 1: Evaluation experiment on the viscosity-enhancing properties of the oil displacement system in Comparative Example 3 The apparent viscosity of the oil displacement system under different conditions was determined using a rotational viscometer at a rotor speed of 6 rpm. Table 1 shows the apparent viscosity of the oil displacement system at 25 °C.

[0039] Table 1 shows that the graphene-silica hybrid mesoporous nanomaterials prepared in this invention can increase the apparent viscosity of the system. Graphene is grown in situ via vapor deposition and chemically bonded to the silica mesoporous framework, which both inhibits graphene sheet stacking and avoids silica mesoporous collapse. The material combines the high interfacial activity of graphene with the abundant active sites of silica. Numerous silanol functional groups and oxygen-containing functional groups on the surface form strong hydrogen bonds and hydrophobic interactions with the amide and sulfonic acid groups of the polymer PCAS, significantly strengthening the polymer's three-dimensional network structure. This results in an increase in the apparent viscosity of the system from 30.1 mPa·s to 45.6 mPa·s.

[0040] Table 2 Apparent viscosity of the oil displacement system (25 °C)

[0041] Displacement experiments of core samples from oil displacement systems in Examples 1, 7, 8, and Comparative Examples 1-3. Using a single-core displacement experimental setup, oil-water displacement was performed on the core until oil was observed at the core outlet. The oil volume was 0.5 mL. min -1 At the injection rate, the core was first water-flooded until the produced fluid water cut reached over 95%, then a 0.5 PV graphene-silica hybrid mesoporous nanofluid flooding system was injected, and finally subsequent water flooding was performed until the water cut reached over 95%. The core displacement experiment results of the flooding systems in Examples 1, 7, 8, and Comparative Example 3 are shown in Table 2.

[0042] Compared with Example 7 (21.6%), Example 8 (13.6%), Comparative Example 1 (7.5%), Comparative Example 2 (14.05%), and Comparative Example 3 (10.7%), the graphene-silica hybrid mesoporous nanofluidic oil displacement system in Example 1 significantly improved the oil recovery rate, reaching 35.1%. This is mainly attributed to the change in the wettability of the rock surface by the nanomaterials and the control of the mobility ratio by the composite system. With the reversal of the wettability of the rock surface, the oil washing efficiency was improved. With the increase of the water-oil mobility ratio, the swept volume was expanded, resulting in a significant increase in the tertiary recovery rate.

[0043] Table 3. Core displacement test results of oil displacement systems in Examples 1, 7, 8, and Comparative Example 3.

[0044] In summary, this invention provides a high-performance, multifunctional mesoporous nanofluid flooding system, offering an innovative technical solution for the efficient development of complex high-temperature and high-salinity reservoirs.

Claims

1. A graphene-silica hybrid mesoporous nanomaterial, comprising a mesoporous silica substrate and a graphene layer grown in situ on the surface and / or within the pores of the substrate by chemical vapor deposition. The mesoporous silica substrate is dendritic mesoporous silica, with its mesopores arranged radially in an ordered manner and a pore size of 2-8 nm. The specific surface area of ​​the graphene-silica hybrid mesoporous nanomaterial is higher than that of the mesoporous silica substrate. The surface roughness of the graphene-silica hybrid mesoporous nanomaterial is greater than that of the mesoporous silica substrate.

2. The preparation method of the graphene-silica hybrid mesoporous nanomaterial according to claim 1, comprising the following steps: Mesoporous silica substrates were prepared by a bicontinuous microemulsion method. The mesoporous silica substrate is placed in a reactor and heated under a reducing atmosphere. Then, a carbon source gas is introduced for chemical vapor deposition to grow the graphene layer in situ on the surface and / or in the pores of the mesoporous silica substrate, thereby obtaining the graphene-silica hybrid mesoporous nanomaterial. The chemical vapor deposition conditions are as follows: the mesoporous silica substrate is heated to 500-700°C in a hydrogen atmosphere and held at that temperature for 20-40 minutes; then acetylene gas is introduced for deposition; after deposition, the substrate is cooled to room temperature in a protective atmosphere.

3. The preparation method according to claim 2, characterized in that: The bicontinuous microemulsion method includes the following steps: The template agent and catalyst were dissolved in water and stirred to form a transparent solution; then the silicon source and oil phase were added and stirred to form a microemulsion; then the co-solvent was added and stirred to stabilize the microemulsion; the temperature was raised to the reaction temperature and stirred to react; the reaction product was centrifuged, washed, dried and calcined to obtain the mesoporous silica substrate.

4. The preparation method according to claim 3, characterized in that: The template agent is selected from one or more of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecylpyridine bromide, and hexadecylpyridine chloride; the amount of the template agent used is 2-6%; The catalyst is selected from one or more of ammonia, urea, methylamine, n-propylamine, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, ethanolamine, formamide, and acetamide; the amount of the catalyst used is 2-5%. The silicon source is tetraethyl orthosilicate, and its dosage is 5-30%. The oil phase is p-xylene; The co-solvent is selected from one or more of methanol, ethanol, ethylene glycol, isopropanol, n-butanol, n-pentanol, and octanol; the amount of the co-solvent is 3-8%. The reaction temperature is 70-80℃; The reaction time is 1-12 h.

5. A mesoporous nanofluidic oil displacement system, comprising the graphene-silica hybrid mesoporous nanomaterial of claim 1, a hydrophobic associative polymer, and formulated water; In the mesoporous nanofluidic oil displacement system, the mass concentration of the graphene-silica hybrid mesoporous nanomaterial is 0.01%-0.2%; And / or, the mass concentration of the hydrophobic associative polymer is 1000-2000 mg / L.

6. The mesoporous nanofluidic oil displacement system according to claim 5, characterized in that: The hydrophobic associative polymer is prepared by free radical polymerization of monomer raw materials including acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and hydrophobic monomers. Preferably, the molar ratio of the acrylamide, the 2-acrylamido-2-methylpropanesulfonic acid, and the acrylic acid is (80-90):(3-8):(5-15); Preferably, the hydrophobic monomer accounts for 0.3%-1.0% of the total mass of the monomer raw materials; Preferably, the hydrophobic monomer is selected from acrylate hydrophobic monomers with a carbon chain length of C8-C18.

7. A method for preparing the mesoporous nanofluidic oil displacement system according to claim 5 or 6, comprising the following steps: A monomeric raw material comprising acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and a hydrophobic monomer is dissolved in water and subjected to free radical polymerization under the action of an initiator to obtain a hydrophobic associative polymer; the graphene-silica hybrid mesoporous nanomaterial described in claim 1 is dispersed in prepared water and subjected to ultrasonic treatment to obtain a nano-suspension; the hydrophobic associative polymer is then added to the nano-suspension and stirred until completely dissolved to obtain the mesoporous nanofluid oil displacement system.

8. The preparation method according to claim 7, characterized in that: The total mass fraction of the monomer in the monomer raw material is 20-35%, preferably 25-30%, and more preferably 27%; The initiator is azobisisobutyramidine hydrochloride, with a mass fraction of 0.01-0.05%; The free radical polymerization reaction was carried out at 5-30°C; The free radical polymerization reaction takes 2-6 hours.

9. The application of the graphene-silica hybrid mesoporous nanomaterial of claim 1 and the mesoporous nanofluid flooding system of claim 5 or 6 in the field of chemical flooding in oilfields, especially in enhancing oil recovery in high-temperature and high-salinity reservoirs.

10. A method for enhancing oil recovery, comprising injecting the mesoporous nanofluidic flooding system of claim 5 or 6 into a target oil reservoir formation; Preferably, the target reservoir is a high-temperature, high-salinity reservoir; Preferably, the injection method includes performing a water-drive step before, after, or simultaneously with the injection of the mesoporous nanofluid oil displacement system.

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