Modified MOF (Metal Organic Framework) oil displacement agent as well as preparation method and application thereof

Abstract

The invention provides a modified MOF oil-displacing agent as well as a preparation method and application thereof. The modified MOF oil-displacing agent is an iron-based MOF material grafted and modified by using a zwitterionic surfactant. The preparation method comprises the following steps: dissolving an organic ligand, mixing the dissolved organic ligand with an iron source for reaction to prepare MOF crystals, and mixing a zwitterionic surfactant, an activating agent and the obtained MOF crystals for reaction. The thickness and the diameter of the modified MOF oil displacement agent provided by the invention have nanoscale sizes, and the modified MOF oil displacement agent can go deep into a low-permeability area containing more oil; the oil-water emulsifying agent has an oil-water emulsifying effect and interface inductivity, has a wedge-shaped permeation effect during migration in a micro-pore channel, has oil phase directionality, and can accurately and efficiently shovel off residual oil adhered to the inner wall of the pore channel; and the oil reservoir has strong adaptability, temperature resistance and hypersalinity resistance, and can be applied to harsh and complex oil reservoir conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction and relates to an oil displacing agent, in particular to a modified MOF oil displacing agent and a preparation method and application thereof. Background Art

[0002] Polymer flooding is a method that uses polymer solution as an oil displacement agent. It increases the viscosity of the displacement fluid to adjust the mobility ratio and expand the swept volume, thereby increasing the crude oil recovery rate. At present, polymer flooding technology has been widely used and has become the dominant technology for "tertiary oil recovery" in some oil fields, playing an important role in crude oil production. However, the long-term use of polymer flooding has continuously eroded the reservoir formation, resulting in increased reservoir heterogeneity, the formation of dominant channels, and high dispersion of residual oil after flooding. As a result, the subsequent recovery oil displacement agent cannot effectively reach the oil-bearing area, resulting in inefficient circulation of the agent. Therefore, the exploitation of oil reservoirs after polymer flooding requires new and efficient oil displacement agents to further improve the recovery rate.

[0003] CN110527503A discloses an anion-cation pair nanoemulsion oil-displacing agent for oil displacement in medium and low permeability reservoirs. The components of the oil-displacing agent include a dispersed phase, anion-cation system surfactants, zwitterionic surfactants, low-carbon alcohols and water. The average particle size of the oil-displacing agent emulsion is less than 100nm, has high surface activity, and its small size effect is more suitable for low-porosity and low-permeability formations.

[0004] CN110872505A discloses an organic porous nanoparticle / surfactant composite oil displacement system and a preparation method thereof. The composite oil displacement system comprises organic porous nanoparticles and a surfactant. The preparation method comprises preparing the surfactant into a solution, adding the organic porous nanoparticles therein and performing ultrasonic dispersion. The obtained oil displacement system can reduce the adsorption loss of the surfactant and enhance its oil displacement effect, is easy to pump, and the nanoparticles are not easy to block the formation.

[0005] CN116004213A discloses a surfactant / nanoparticle composite oil-displacing agent and its preparation method and application. The composite oil-displacing agent comprises a surfactant, nanoparticles and water, and the nanoparticles used are polyether organosilicon-modified silica particles. The composite oil-displacing agent can improve the interfacial activity of the system, wash crude oil from rock formation sand and effectively solubilize it, thereby improving the crude oil recovery rate.

[0006] CN113583647A discloses a surfactant-MOF composite material and a preparation method thereof. The surfactant is dissolved in a metal organic framework solution so that the metal organic framework embeds the surfactant, which can reduce the oil-water interfacial tension, emulsify the crude oil, change the rheology of the crude oil, and ultimately improve the efficiency of oil extraction.

[0007] The nanoscale oil displacement agents provided in the prior art are all prepared by mixing and compounding nanomaterials and surfactants to form a mixed oil displacement system. The mixed system has diverse components, difficult to control the size, poor stability, and the combined synergistic effect of nanomaterials and surfactants is very limited, making it difficult to further improve the oil displacement effect under harsh and complex reservoir conditions.

[0008] Therefore, in view of the shortcomings of the existing technology, it is necessary to provide a modified MOF oil displacement agent and a preparation method and application thereof. Summary of the invention

[0009] The purpose of the present invention is to provide a modified MOF oil-displacing agent and a preparation method and application thereof, in order to solve the problem that the residual oil has large dispersibility and the oil-displacing agent cannot reach the oil-containing area after polymer flooding.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a modified MOF oil-displacing agent, wherein the modified MOF oil-displacing agent is an iron-based MOF crystal material grafted and modified using a zwitterionic surfactant; the MOF crystal material is a single crystal;

[0012] The organic ligand of the iron-based MOF crystal material includes 5-amino-1,10-phenanthroline.

[0013] The oil-displacing agent provided by the present invention is used to prepare iron-based MOF two-dimensional nanosheets. The organic framework of the iron-based MOF nanosheets is 5-amino-1,10-phenanthroline, which contains -NH2 functional groups in its molecular structure and can be grafted with zwitterionic surfactants. The "wedge-shaped penetration" effect of the two-dimensional nanosheets when migrating in the pores can be used to scrape off the residual oil adhering to the inner wall of the pores. At the same time, the zwitterionic surfactants have oil-water amphiphilicity, can sense changes in interfacial energy, and are oriented to the oil-water interface. The surfactants are grafted onto the surface of the iron-based MOF two-dimensional nanosheets by the present invention, so that the iron-based MOF two-dimensional nanosheets also have oil-water amphiphilicity, are oriented to the oil-water interface, realize automatic oil seeking, and play an oil-displacing role together with the nanosheets, thereby solving the problem of low efficiency of the oil-displacing agent.

[0014] Preferably, the zwitterionic surfactant includes any one of dodecyl dimethyl betaine, lauramidopropyl betaine or cocoamidopropyl betaine, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of dodecyl dimethyl betaine and lauramidopropyl betaine, a combination of lauramidopropyl betaine and cocoamidopropyl betaine, a combination of dodecyl dimethyl betaine and cocoamidopropyl betaine, or a combination of dodecyl dimethyl betaine, lauramidopropyl betaine and cocoamidopropyl betaine.

[0015] In a second aspect, the present invention provides a method for preparing the modified MOF oil-displacing agent as described in the first aspect, the preparation method comprising the following steps:

[0016] (1) The organic ligand and the iron source are mixed and reacted to obtain a MOF solid compound, and then the MOF solid compound is diffused and crystallized to obtain a MOF crystal;

[0017] (2) Mixing a zwitterionic surfactant and an activator with the MOF crystals obtained in step (1) to react to obtain a modified MOF oil displacement agent.

[0018] The preparation method provided by the present invention first prepares a synthetic MOF crystal, and then adds an activator to participate in the reaction to achieve the grafting of a zwitterionic surfactant on the surface of the MOF crystal. The steps are simple and easy to implement.

[0019] The mixing and reaction in step (1) of the present invention is carried out in a solvent system, and the solvent includes but is not limited to methanol. Exemplarily, the mixing and reaction in step (1) includes dissolving the organic ligand in a solvent and then mixing it with the iron source; or, first mixing the organic ligand with the iron source and then dissolving it with a solvent.

[0020] Preferably, the organic ligand in step (1) comprises 5-amino-1,10-phenanthroline.

[0021] Preferably, the iron source in step (1) comprises FeCl3.

[0022] Preferably, the molar ratio of the organic ligand to the iron source in step (1) is (2.5-3.5):1, for example, it can be 2.5:1, 2.8:1, 3:1, 3.2:1 or 3.5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the reaction method in step (1) comprises a reflux reaction.

[0024] Preferably, the reaction temperature in step (1) is 60-70°C, for example, 60°C, 62°C, 64°C, 65°C, 66°C, 68°C or 70°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, after the reaction in step (1), the solvent is evaporated, a poor solvent is added to precipitate the solid, and the solid-liquid is separated.

[0026] Preferably, the poor solvent comprises anhydrous ether.

[0027] Preferably, the diffusion crystallization step in step (1) comprises dissolving the MOF solid compound and then crystallizing it using a poor solvent.

[0028] Preferably, the solvent used for dissolving includes N,N-dimethylformamide.

[0029] Preferably, the concentration of the dissolved solution is 0.10-0.20%, for example, it can be 0.10%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18% or 0.20%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the poor solvent comprises anhydrous ether.

[0031] Preferably, the zwitterionic surfactant in step (2) comprises any one of dodecyl dimethyl betaine, lauramidopropyl betaine or cocoamidopropyl betaine, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of dodecyl dimethyl betaine and lauramidopropyl betaine, a combination of lauramidopropyl betaine and cocoamidopropyl betaine, a combination of dodecyl dimethyl betaine and cocoamidopropyl betaine, or a combination of dodecyl dimethyl betaine, lauramidopropyl betaine and cocoamidopropyl betaine.

[0032] Preferably, the activator in step (2) comprises 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and / or N-hydroxysuccinimide.

[0033] Preferably, the mass ratio of the zwitterionic surfactant to the MOF crystal is 1:(0.1-0.3), for example, it can be 1:0.1, 1:0.15, 1:0.2, 1:0.25 or 1:0.3, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the amount of the activator is 0.3-0.5wt% of the sum of the mass of the zwitterionic surfactant, MOF crystal and the activator, for example, it can be 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt% or 0.5wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In a third aspect, the present invention provides a use of the modified MOF oil-displacing agent as described in the first aspect, wherein the modified MOF oil-displacing agent is used for tertiary oil recovery.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The modified MOF oil-displacing agent provided by the present invention is a circular sheet with a regular shape, and a thickness and a diameter both of which are of nanometer size, and can penetrate into low-permeability areas with more oil; the MOF nanosheets are grafted with amphoteric surfactants, which have both oil-water emulsification effect and interface sensitivity, have a "wedge-shaped penetration" effect when migrating in micropores, and have oil phase orientation, and can accurately and efficiently remove residual oil adhering to the inner wall of the pores; it has strong adaptability to oil reservoirs, is resistant to temperature and high mineralization, and can be applied to harsh and complex oil reservoir conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the infrared spectrum of the MOF crystal and the modified MOF oil displacement agent provided in Example 1 of the present invention.

[0039] Figure 2 This is a transmission electron microscope image of the MOF crystal provided in Example 1 of the present invention.

[0040] Figure 3 This is a transmission electron microscope image of the MOF crystal provided in Example 1 of the present invention.

[0041] Figure 4 This is a transmission electron microscope image of the modified MOF oil-displacing agent provided in Example 1 of the present invention.

[0042] Figure 5 This is a transmission electron microscope image of the modified MOF oil-displacing agent provided in Example 1 of the present invention.

[0043] Figure 6 This is a physical picture of the modified MOF oil displacement agent provided in Example 1 of the present invention mixed with kerosene for emulsification. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0045] Example 1

[0046] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0047] (1) Add 25.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat and reflux at 65℃ for 2h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to wash away the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum oven for 2h, weigh it, take the purple-red solid compound, dissolve it in 50mL N,N-dimethylformamide to prepare a solution with a concentration of 0.10%, then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether, and MOF crystals can be obtained after 1 month;

[0048] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.2 g of MOF crystal, 0.2 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0049] Example 2

[0050] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0051] (1) Add 30.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat under reflux at 65℃ for 2h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to remove the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum oven for 2h, weigh it, take the purple-red solid compound, dissolve it in 50mL N,N-dimethylformamide to prepare a solution with a concentration of 0.12%, then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether. After 2 months, crystalline MOF can be obtained;

[0052] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.2 g of MOF crystal, 0.2 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0053] The modified MOF oil-displacing agent prepared in this example is the same as that in Example 1.

[0054] Example 3

[0055] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0056] (1) Add 35.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat under reflux at 65℃ for 2h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to remove the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum oven for 2h, weigh it, take the purple-red solid compound, dissolve it in 50mL N,N-dimethylformamide to prepare a solution with a concentration of 0.14%, then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether, and MOF crystals can be obtained after 1 month;

[0057] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.2 g of MOF crystal, 0.2 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the above solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0058] The modified MOF oil-displacing agent prepared in this example is the same as that in Example 1.

[0059] Example 4

[0060] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0061] (1) Add 35.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat and reflux at 65℃ for 2h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to remove the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum oven for 2h, weigh it, take the purple-red solid compound, dissolve it in 50mL N,N-dimethylformamide to prepare a solution with a concentration of 0.16%, then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether, and MOF crystals can be obtained in 2 months;

[0062] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.1 g of MOF crystal, 0.2 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the above solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0063] The modified MOF oil-displacing agent prepared in this example is the same as that in Example 1.

[0064] Example 5

[0065] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0066] (1) Add 35.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat under reflux at 65℃ for 2h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to remove the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum oven for 2h, weigh it, take the purple-red solid compound, dissolve it in 50mL N,N-dimethylformamide to prepare a solution with a concentration of 0.18%, then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether, and MOF crystals can be obtained in 2 months;

[0067] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.2 g of MOF crystal, 0.2 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the above solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0068] The modified MOF oil-displacing agent prepared in this example is the same as that in Example 1.

[0069] Example 6

[0070] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0071] (1) Add 35.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat and reflux at 65℃ for 2h. Then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to wash away the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum oven for 2h, weigh it, take the purple-red solid compound, dissolve it with 50mL N,N-dimethylformamide, and prepare a solution with a concentration of 0.20%. Then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether. MOF crystals can be obtained in 2 months;

[0072] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.3 g of MOF crystal, 0.2 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the above solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0073] The modified MOF oil-displacing agent prepared in this example is the same as that in Example 1.

[0074] Example 7

[0075] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0076] (1) Add 35.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat and reflux at 60℃ for 2h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to wash away the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum drying oven for 2h, weigh it, take the purple-red solid compound, dissolve it in 50mL N,N-dimethylformamide to prepare a solution with a concentration of 0.10%, then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether, and MOF crystals can be obtained after 1 month;

[0077] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.3 g of MOF crystal, 0.1 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0078] The modified MOF oil-displacing agent prepared in this example is the same as that in Example 1.

[0079] Example 8

[0080] This embodiment provides a modified MOF oil-displacing agent, and the preparation method of the modified MOF oil-displacing agent comprises the following steps:

[0081] (1) Add 35.0mmol 5-amino-1,10-phenanthroline and 150mL methanol to a 250mL flask, stir to dissolve, add 10.0mmol FeCl3·6H2O, heat and reflux at 70℃ for 2h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30mL, add 30mL anhydrous ether, ultrasonicate at room temperature for 2min, let stand for 10min to allow the solid to fully precipitate, pour off the solvent, then add 50mL chloroform, ultrasonicate at room temperature for 2min, filter and wash twice to wash away the residual reactants to obtain a purple-red solid compound, then dry it in a vacuum oven for 2h, weigh it, take the purple-red solid compound, dissolve it in 50mL N,N-dimethylformamide to prepare a solution with a concentration of 0.10%, then pour the solution evenly into 5 50mL clean test tubes, put them into a wide-mouth bottle and diffuse and crystallize with ether, and MOF crystals can be obtained after 1 month;

[0082] (2) 100 mL of deionized water was taken into a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, and then 0.3 g of MOF crystal, 0.3 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and magnetic stirring was performed for 4 h to react at room temperature. After the reaction was completed, 200 mL of anhydrous ethanol was added to the solution to precipitate the unreacted dodecyl dimethyl betaine, and then the solution was filtered, the filtrate was collected, and the solvent was removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0083] The modified MOF oil-displacing agent prepared in this example is the same as that in Example 1.

[0084] Example 9

[0085] This embodiment provides a modified MOF oil displacement agent. Compared with Example 1, the zwitterionic surfactant is replaced with octadecyl amide propyl betaine, and the rest is the same as Example 1.

[0086] In this embodiment, octadecyl amide betaine is used as a zwitterionic surfactant. The hydrophobic chain of octadecyl amide betaine is relatively long and its water solubility is relatively poor. After being grafted and modified with MOF crystals, it will affect the water solubility of the oil-displacing agent and thus reduce its use effect. At the same time, the cost of using octadecyl amide betaine is relatively high, which increases the industrial cost of the oil-displacing agent and its application value is relatively low.

[0087] The preferred zwitterionic surfactant of the present invention has a better oil displacement effect, is a common industrial product, is cheap, and has high application value.

[0088] Comparative Example 1

[0089] This comparative example provides a modified MOF oil-displacing agent. Compared with Example 1, the diffusion crystallization of the MOF solid compound is not performed in the control step (1), and the rest is the same as Example 1.

[0090] In this comparative example, the MOF solid compound is not subjected to diffusion crystallization, and the obtained product is an amorphous (non-crystalline) powder without a regular circular flaky nanosheet microstructure. The functional group active sites of the randomly arranged MOF solid compound cannot be fully exposed to the outer surface, and effective grafting modification cannot be achieved, and thus the product does not have directional oil recovery performance.

[0091] The infrared spectra of the modified MOF oil-displacing agent (denoted as MOF-BS12) prepared in Example 1 of the present invention and the MOF crystal (denoted as MOF) prepared in step (1) were measured. Figure 1 As shown, it can be seen that the infrared spectrum of MOF is at 3400cm -1 The absorption peak that appears near is the characteristic absorption peak of -NH2, at 1600cm -1 The absorption peaks near the conjugated benzene ring are C=C characteristic peaks, and the absorption peaks at 700cm -1 The Fe-N absorption peak near the 2900cm-1 peak indicates that the product synthesized in step (1) is a MOF crystal with iron ion as the central ion and 5-amino-1,10-phenanthroline as the ligand. The modified MOF oil displacement agent is dodecyl dimethyl betaine grafted on the MOF crystal. The infrared spectrum shows that the MOF crystal has a Fe-N absorption peak at 2900cm-1. -1 There is an obvious absorption peak of alkyl carbon chain near 1650cm -1 A sharp and strong -C=O absorption peak appeared nearby, overlapping the original C=C peak, indicating that dodecyl dimethyl betaine was successfully introduced into the MOF crystal.

[0092] The transmission electron microscope image of the MOF crystal (denoted as MOF) prepared in step (1) of Example 1 of the present invention is as follows: Figure 2 and Figure 3 As shown, the transmission electron microscopy image of the modified MOF oil displacement agent (denoted as MOF-BS12) prepared in Example 1 is as follows Figure 4 and Figure 5 As shown in the transmission electron microscope image, it can be seen that the microscopic morphology of the MOF crystal is a round flake with a size distribution between 100-200nm. The darker black part in the image is the superposition of multiple layers of nano-discs. There is a layer of wrapping on the surface of MOF-BS12, indicating that dodecyl dimethyl betaine is connected to the MOF surface to form an irregular coating film.

[0093] The MOF crystal prepared in step (1) of Example 1 of the present invention is prepared into a MOF solution with a mass fraction of 0.1%, mixed with kerosene, emulsified and allowed to stand for 12 hours. Figure 6As shown in the tube a in the middle, the modified MOF oil displacement agent prepared in Example 1 was prepared into solutions with mass fractions of 0.02%, 0.04%, 0.06%, 0.08% and 0.1%, respectively. The obtained solutions were mixed with kerosene for emulsification and allowed to stand for 12 hours. The substances were respectively as shown in Figure 6 As shown in tubes b, c, d, e and f in the figure, it can be seen that the color distribution of the lower layer of tube a is uniform, there is no enrichment phenomenon and no emulsified layer, and the lower layers of tubes b, c, d, e and f all show color depth changes, the closer to the upper oil phase, the darker the color, enrichment phenomenon and stable emulsified layer appear, indicating that the ungrafted MOF does not have oil-water interface orientation and emulsification, while the grafted MOF-BS12 has oil-water interface enrichment effect and emulsification effect, indicating that the modified MOF oil-displacing agent prepared by the present invention has oil phase orientation, and when the mass concentration of the modified MOF oil-displacing agent is 0.04%, the emulsified layer height is the highest and has obvious orientation effect.

[0094] The modified MOF oil displacement agents prepared in Examples 1-8 of the present invention and Comparative Example 1 were prepared into solutions with a mass fraction of 0.1%, mixed with kerosene, emulsified and allowed to stand for 12 hours. The emulsification conditions are listed in Table 1.

[0095] Table 1

[0096] Oil displacement agent mass concentration (%) Emulsion layer height (cm) Emulsion stability time (h) Example 1 0.1％ 5.2 4.2 Example 2 0.1％ 5.1 4.0 Example 3 0.1％ 5.2 4.1 Example 4 0.1％ 5.7 4.6 Example 5 0.1％ 5.0 4.2 Example 6 0.1％ 4.9 3.9 Example 7 0.1％ 5.0 4.1 Example 8 0.1％ 5.0 4.0 Comparative Example 1 0.1％ 1.2 0.3

[0097] It can be seen from Table 1 that the modified MOF oil-displacing agents prepared in Examples 1-8 of the present invention all have good emulsifying effects. When the mass concentration is 0.1%, the height of the emulsified layer can reach more than 4.9 cm, and the emulsion stability time is more than 3.9 h, indicating that the modified MOF oil-displacing agents prepared in Examples 1-8 all achieve the grafting of amphoteric surfactants on MOF crystal materials and have good oil-displacing effects. Compared with Example 1, the emulsifying effect of the modified MOF oil-displacing agent prepared in Comparative Example 1 is quite different, and it is difficult to successfully graft zwitterionic surfactants on the surface of MOF solid compounds, and an effective oil-displacing effect cannot be achieved.

[0098] In summary, the modified MOF oil-displacing agent provided by the present invention is a circular sheet with a regular shape, and its thickness and diameter are both nanometer-sized, so it can penetrate into the low-permeability area with more oil; the MOF nanosheet is grafted with an amphoteric surfactant, which has both oil-water emulsification effect and interface sensitivity, has a "wedge-shaped penetration" effect when migrating in the micropores, and has oil phase orientation, which can accurately and efficiently remove the residual oil adhering to the inner wall of the pore; it has strong adaptability to oil reservoirs, is resistant to temperature and high mineralization, and can be applied to harsh and complex oil reservoir conditions.

[0099] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A modified MOF oil displacement agent, characterized in that: The modified MOF oil displacement agent is an iron-based MOF crystal material grafted and modified by a zwitterionic surfactant; the MOF crystal material is a single crystal; The organic ligand of the iron-based MOF crystal material includes 5-amino-1,10-phenanthroline.

2. The modified MOF oil-displacing agent according to claim 1, characterized in that, The zwitterionic surfactant includes any one of dodecyl dimethyl betaine, lauryl amide propyl betaine or cocamidopropyl betaine, or a combination of at least two thereof.

3. A method for preparing the modified MOF oil-displacing agent according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) The organic ligand and the iron source are mixed and reacted to obtain a MOF solid compound, and then the MOF solid compound is diffused and crystallized to obtain a MOF crystal; (2) Mixing a zwitterionic surfactant and an activator with the MOF crystals obtained in step (1) to react to obtain a modified MOF oil displacement agent.

4. The preparation method according to claim 3, characterized in that: The organic ligand in step (1) includes 5-amino-1,10-phenanthroline; Preferably, the iron source in step (1) comprises FeCl3; Preferably, the molar ratio of the organic ligand to the iron source in step (1) is (2.5-3.5):

1.

5. The preparation method according to claim 3 or 4, characterized in that: The reaction method of step (1) includes reflux reaction; Preferably, the reaction temperature in step (1) is 60-70°C.

6. The preparation method according to any one of claims 3 to 5, characterized in that: After the reaction in step (1), the solvent is evaporated, a poor solvent is added to precipitate the solid, and the solid-liquid is separated; Preferably, the poor solvent comprises anhydrous ether.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The diffusion crystallization step in step (1) comprises dissolving the MOF solid compound and then crystallizing it using a poor solvent; Preferably, the solvent used for dissolving includes N,N-dimethylformamide; Preferably, the concentration of the solution obtained by dissolving is 0.10-0.20%; Preferably, the poor solvent comprises anhydrous ether.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The zwitterionic surfactant in step (2) includes any one of dodecyl dimethyl betaine, lauryl amide propyl betaine or cocoamidopropyl betaine, or a combination of at least two thereof.

9. The preparation method according to any one of claims 3 to 8, characterized in that: The activator in step (2) includes 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and / or N-hydroxysuccinimide; Preferably, the mass ratio of the zwitterionic surfactant to the MOF crystal is 1:(0.1-0.3); Preferably, the amount of the activator is 0.3-0.5 wt % of the sum of the mass of the zwitterionic surfactant, the MOF crystal and the activator.

10. Use of the modified MOF oil-displacing agent according to claim 1 or 2, wherein the modified MOF oil-displacing agent is used for tertiary oil recovery.

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