Modified MOF oil displacement agent, preparation method and application thereof

Abstract

The application provides a modified MOF oil displacement agent and a preparation method and application thereof. The modified MOF oil displacement agent is an iron-based MOF material grafted by using a zwitterionic surfactant. The preparation method comprises the following steps: dissolving an organic ligand, mixing the organic ligand with an iron source to react, preparing MOF crystals, and mixing a zwitterionic surfactant, an activator and the obtained MOF crystals to react. The modified MOF oil displacement agent provided by the application has nanoscale size in thickness and diameter, can enter low-permeability areas with more oil, has oil-water emulsification effect and interface sensitivity, has a 'wedge-shaped penetration' effect when migrating in micropores, has oil phase directionality, can accurately and efficiently shovel off residual oil adhering to the inner wall of the pores, has strong adaptability to oil reservoirs, is resistant to temperature and high salinity, and can be applied to harsh and complex oil reservoir conditions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil exploitation, and relates to an oil displacement agent, in particular to a modified MOF oil displacement agent and a preparation method and application thereof. BACKGROUND

[0002] Polymer flooding is a method of using polymer solution as an oil displacement agent to adjust the mobility ratio by increasing the viscosity of the displacement fluid, expand the swept volume, and thus improve the oil recovery. At present, polymer flooding technology is widely used and has become the leading technology for "tertiary oil recovery" in some oil fields, and plays an important role in crude oil production. However, long-term use of polymer flooding causes continuous scouring of the reservoir formation, resulting in increased reservoir heterogeneity, formation of dominant channels, and high dispersibility of residual oil after oil displacement, which further makes it difficult for subsequent oil displacement agents to effectively reach the oil-bearing area, resulting in low-efficiency circulation of the agents. Therefore, new and efficient oil displacement agents are needed for the exploitation of oil reservoirs after polymer flooding to further improve the oil recovery.

[0003] CN110527503A discloses a cation-anion pair nanoemulsion oil displacement agent for middle-low permeability reservoirs, which comprises a dispersed phase, a cation-anion system surfactant, a zwitterionic surfactant, a low-carbon alcohol, and water. The average particle size of the oil displacement agent emulsion is less than 100 nm, and it has high surface activity, which is more suitable for low-porosity and low-permeability formations due to its small size effect.

[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 surfactants. The preparation method comprises preparing a surfactant solution and then adding organic porous nanoparticles to the solution and performing ultrasonic dispersion. The obtained oil displacement system can reduce the adsorption loss of surfactants and enhance the 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 displacement agent, a preparation method and application thereof. The composite oil displacement agent comprises surfactants, nanoparticles, and water, and the nanoparticles are polyether organosilicon modified silica particles. The composite oil displacement agent can improve the interfacial activity of the system, wash the crude oil from the rock and sand and effectively solubilize it, and thus improve the oil recovery.

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

[0007] The nanoscale oil displacement agents provided in the prior art all adopt nanomaterials and surfactants to form a mixed oil displacement system, which has many components, is difficult to control in size, has poor stability, and the combination of nanomaterials and surfactants has very limited synergistic effect, and it is difficult to further improve the oil displacement effect under harsh and complex reservoir conditions.

[0008] Therefore, in view of the deficiencies of the prior art, it is necessary to provide a modified MOF oil displacement agent and a preparation method and application thereof. SUMMARY

[0009] The purpose of the present application is to provide a modified MOF oil displacement agent and a preparation method and application thereof, which solves the problem that residual oil is dispersed and the oil displacement agent cannot reach the oil-containing area after polymer flooding.

[0010] To achieve this purpose, the present application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a modified MOF oil displacement agent, which is an iron-based MOF crystal material grafted with 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 displacement agent provided by the present application prepares an iron-based MOF two-dimensional nanosheet, and the organic framework of the iron-based MOF nanosheet is 5-amino-1,10-phenanthroline, which contains a -NH2 functional group in its molecular structure and can be grafted with a zwitterionic surfactant. The iron-based MOF two-dimensional nanosheet has a "wedge-shaped penetration" effect when it moves in the pore, which can shovel off the residual oil adhering to the inner wall of the pore. At the same time, the zwitterionic surfactant has oil-water amphiphilicity and can sense the change of interfacial energy and be oriented to the oil-water interface. The present application grafts the surfactant to the surface of the iron-based MOF two-dimensional nanosheet, so that the iron-based MOF two-dimensional nanosheet also has oil-water amphiphilicity and is oriented to the oil-water interface, realizing automatic oil seeking and playing a role in oil displacement together with the nanosheet, thereby solving the problem of low efficiency of the oil displacement agent.

[0014] Preferably, the zwitterionic surfactant includes any one or a combination of at least two of dodecyl dimethyl betaine, lauryl amidopropyl betaine or cocamidopropyl betaine, and a typical but non-limiting combination includes a combination of dodecyl dimethyl betaine and lauryl amidopropyl betaine, a combination of lauryl amidopropyl betaine and cocamidopropyl betaine, a combination of dodecyl dimethyl betaine and cocamidopropyl betaine, or a combination of dodecyl dimethyl betaine, lauryl amidopropyl betaine and cocamidopropyl betaine.

[0015] In a second aspect, the present application provides a preparation method of the modified MOF oil displacement agent according to the first aspect, the preparation method comprising the following steps:

[0016] (1) mixing and reacting an organic ligand with an iron source to obtain a MOF solid compound, and then diffusing and crystallizing the MOF solid compound to obtain a MOF crystal;

[0017] (2) mixing and reacting the zwitterionic surfactant, the activator and the MOF crystal obtained in step (1) to obtain the modified MOF oil displacement agent.

[0018] The preparation method provided by the present application first prepares a synthetic MOF crystal, and then participates in the reaction by adding an activator to graft a zwitterionic surfactant on the surface of the MOF crystal, which is simple and easy to implement.

[0019] The mixing and reaction in step (1) of the present application are carried out in a solvent system, which includes but is not limited to methanol. For example, the mixing and reaction in step (1) includes dissolving the organic ligand in the solvent and then mixing with the iron source; or, the organic ligand is mixed with the iron source first, and then the solvent is used for dissolution.

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

[0021] Preferably, the iron source in step (1) includes 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 values not listed in the value range are also applicable.

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

[0024] Preferably, the reaction temperature in step (1) is 60-70℃, for example, it can be 60℃, 62℃, 64℃, 65℃, 66℃, 68℃ or 70℃, but is not limited to the listed values, and other values not listed in the value 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 then solid-liquid separation is performed.

[0026] Preferably, the poor solvent includes anhydrous diethyl ether.

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

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

[0029] Preferably, the concentration of the solution obtained by the dissolving 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 values not listed in the value range are also applicable.

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

[0031] Preferably, the zwitterionic surfactant in step (2) comprises any one or a combination of at least two of dodecyl dimethyl betaine, lauryl amidopropyl betaine or cocamidopropyl betaine, and a typical but non-limiting combination comprises a combination of dodecyl dimethyl betaine and lauryl amidopropyl betaine, a combination of lauryl amidopropyl betaine and cocamidopropyl betaine, a combination of dodecyl dimethyl betaine and cocamidopropyl betaine, or a combination of dodecyl dimethyl betaine, lauryl amidopropyl betaine and cocamidopropyl betaine.

[0032] Preferably, the activating agent 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 crystals 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 values not listed in the value range are also applicable.

[0034] Preferably, the amount of the activating agent is 0.3-0.5wt% of the total mass of the zwitterionic surfactant, the MOF crystals and the activating agent, 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 values not listed in the value range are also applicable.

[0035] In a third aspect, the present application provides an application of the modified MOF oil displacement agent as described in the first aspect, wherein the modified MOF oil displacement agent is used for tertiary oil recovery.

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

[0037] The modified MOF oil displacement agent provided by the application is a circular sheet, has a regular shape, and has nanoscale thickness and diameter, and can penetrate into a low-permeability area with more oil; the MOF nanosheet is grafted with an amphoteric surfactant, has oil-water emulsification effect and interface sensitivity, has a "wedge-shaped penetration" effect when migrating in a micropore, and has oil phase directionality, and can accurately and efficiently shovel off residual oil adhering to the inner wall of the pore; the oil reservoir has strong adaptability, is resistant to temperature and high salinity, and can be applied to harsh and complex oil reservoir conditions. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is an infrared spectrum of the MOF crystal and the modified MOF oil displacement agent provided by the application.

[0039] Figure 2 is a transmission electron microscope image of the MOF crystal provided by the application.

[0040] Figure 3 is a transmission electron microscope image of the MOF crystal provided by the application.

[0041] Figure 4 is a transmission electron microscope image of the modified MOF oil displacement agent provided by the application.

[0042] Figure 5 is a transmission electron microscope image of the modified MOF oil displacement agent provided by the application.

[0043] Figure 6 is a physical picture of the modified MOF oil displacement agent mixed with kerosene for emulsification provided by the application. DETAILED DESCRIPTION

[0044] The technical solutions of the application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application, and should not be regarded as specific limitations on the application.

[0045] Embodiment 1

[0046] The embodiment provides a modified MOF oil displacement agent, and a preparation method of the modified MOF oil displacement agent includes the following steps:

[0047] (1) In a 250 mL flask, add 25.0 mmol 5-amino-1,10-phenanthroline, 150 mL methanol, stir to dissolve, add 10.0 mmol FeCl3·6H2O, heat to reflux at 65°C for 2 h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30 mL, add 30 mL anhydrous ether, ultrasonic at room temperature for 2 min, stand for 10 min, make the solid dissolve, pour off the solvent, then add 50 mL chloroform, ultrasonic at room temperature for 2 min, filter and wash twice, wash off the residual reactants, get purple red solid compound, then dry in vacuum drying oven for 2 h, weigh, take the purple red solid compound, dissolve in 50 mL N,N-dimethylformamide, prepare a solution with a concentration of 0.10%, then pour the solution into 5 clean 50 mL test tubes evenly, put into a jar and diffuse crystallization with ether, MOF crystals can be obtained after 1 month;

[0048] (2) Take 100 mL deionized water in a beaker, dissolve dodecyl dimethyl betaine to prepare a solution with a concentration of 1%, then add 0.2 g MOF crystals, 0.2 g N-hydroxysuccinimide, 0.2 g 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, magnetically stir for 4 h, react at room temperature, after the reaction is completed, add 200 mL anhydrous ethanol to the solution to make the unreacted dodecyl dimethyl betaine precipitate, then filter, collect the filtrate, and rotary evaporate the solvent to obtain a modified MOF oil displacement agent.

[0049] Example 2

[0050] The present embodiment provides a modified MOF oil displacement agent, and a preparation method of the modified MOF oil displacement agent comprises the following steps:

[0051] (1) In a 250 mL flask, add 25.0 mmol 5-amino-1,10-phenanthroline, 150 mL methanol, stir to dissolve, add 10.0 mmol FeCl3·6H2O, heat to reflux at 65°C for 2 h, then cool to room temperature, rotary evaporate the solvent, concentrate to 30 mL, add 30 mL anhydrous ether, ultrasonic at room temperature for 2 min, stand for 10 min, make the solid dissolve, pour off the solvent, then add 50 mL chloroform, ultrasonic at room temperature for 2 min, filter and wash twice, wash off the residual reactants, get purple red solid compound, then dry in vacuum drying oven for 2 h, weigh, take the purple red solid compound, dissolve in 50 mL N,N-dimethylformamide, prepare a solution with a concentration of 0.10%, then pour the solution into 5 clean 50 mL test tubes evenly, put into a jar and diffuse crystallization with ether, MOF crystals can be obtained after 1 month;

[0052] (2) Take 100 mL of deionized water in a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, then add 0.2 g of MOF crystals, 0.2 g of N-hydroxysuccinimide, 0.2 g of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride, and stir magnetically for 4 h, allowing it to react at room temperature. After the reaction is complete, 200 mL of anhydrous ethanol is added to the solution to precipitate the unreacted dodecyl dimethyl betaine, then suction filtration is performed, the filtrate is collected, and the solvent is removed by rotary evaporation to obtain the modified MOF oil displacement agent.

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

[0054] Example 3

[0055] This example provides a modified MOF oil displacement agent, and a preparation method thereof includes the following steps:

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

[0057] (2) Take 100 mL of deionized water in a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, then add 0.2 g of MOF crystals, 0.2 g of N-hydroxysuccinimide, 0.2 g of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride, and stir magnetically for 4 h, allowing it to react at room temperature. After the reaction is complete, 200 mL of anhydrous ethanol is added to the solution to precipitate the unreacted dodecyl dimethyl betaine, then suction filtration is performed, the filtrate is collected, and the solvent is removed by rotary evaporation to obtain the modified MOF oil displacement agent.

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

[0059] Example 4

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

[0061] (1) 35.0 mmol of 5-amino-1,10-phenanthroline, 150 mL of methanol, stirring to dissolve, 10.0 mmol of FeCl3·6H2O, heating refluxing at 65 DEG C for 2 h, then cooling to room temperature, rotary evaporation of solvent, concentrated to 30 mL, 30 mL of anhydrous ether, room temperature ultrasonic 2 min, standing for 10 min, the solid was analyzed and discharged, then 50 mL of chloroform was added, room temperature ultrasonic 2 min, suction filtration and washing twice, and the residual reactants were washed to obtain a purple red solid compound, then vacuum drying box drying for 2 h, weighing, taking the purple red solid compound, dissolving in 50 mL of N,N-dimethylformamide to prepare a solution with a concentration of 0.16%, then the solution was evenly poured into 5 clean 50 mL test tubes, and was placed in a jar to diffuse and crystallize with ether, and MOF crystals can be obtained in 2 months;

[0062] (2) 100 mL of deionized water was taken in a beaker, and dodecyl dimethyl betaine was dissolved to prepare a solution with a concentration of 1%, then 0.1 g of MOF crystals, 0.2 g of N-hydroxysuccinimide and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride were added, magnetic stirring was conducted for 4 h, reaction was carried out at room temperature, after the reaction was completed, 200 mL of anhydrous ethanol was added to the above solution to precipitate unreacted dodecyl dimethyl betaine, then suction filtration was conducted, 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 displacement agent prepared in the embodiment is same as that in embodiment 1.

[0064] Embodiment 5

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

[0066] (1) In a 250 mL flask, 35.0 mmol of 5-amino-1,10-phenanthroline, 150 mL of methanol were added, stirred to dissolve, 10.0 mmol of FeCl3·6H2O was added, heated to reflux at 65°C for 2 h, then cooled to room temperature, rotary evaporation of solvent, concentrated to 30 mL, 30 mL of anhydrous ether was added, ultrasonic for 2 min at room temperature, stand for 10 min, make the solid analysis, pour off the solvent, then add 50 mL of chloroform, ultrasonic for 2 min at room temperature, filter and wash twice, wash off the residual reactants, get purple red solid compound, then dry in vacuum drying oven for 2 h, weigh, take the purple red solid compound, dissolve in 50 mL of N,N-dimethylformamide to prepare a solution with a concentration of 0.18%, then pour the solution into 5 clean 50 mL test tubes, put into a jar to diffuse and crystallize with ether, MOF crystals can be obtained in 2 months;

[0067] (2) In a beaker, 100 mL of deionized water was dissolved with dodecyl dimethyl betaine to prepare a solution with a concentration of 1%, then 0.2 g of MOF crystals, 0.2 g of N-hydroxysuccinimide, and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, stirred magnetically for 4 h, reacted 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, then filtered, collected the filtrate, and rotary evaporated to remove the solvent to obtain a modified MOF oil displacement agent.

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

[0069] Example 6

[0070] The modified MOF oil displacement agent prepared in this example is the same as that in Example 1.

[0071] (1) In a 250 mL flask, 35.0 mmol of 5-amino-1,10-phenanthroline, 150 mL of methanol were added, stirred to dissolve, 10.0 mmol of FeCl3·6H2O was added, heated to reflux at 65°C for 2 h, then cooled to room temperature, rotary evaporation of solvent, concentrated to 30 mL, 30 mL of anhydrous ether was added, ultrasonic for 2 min at room temperature, stand for 10 min, make the solid analysis, pour off the solvent, then add 50 mL of chloroform, ultrasonic for 2 min at room temperature, filter and wash twice, wash off the residual reactants, get purple red solid compound, then dry in vacuum drying oven for 2 h, weigh, take the purple red solid compound, dissolve in 50 mL of N,N-dimethylformamide to prepare a solution with a concentration of 0.18%, then pour the solution into 5 clean 50 mL test tubes, put into a jar to diffuse and crystallize with ether, MOF crystals can be obtained in 2 months;

[0072] (2) Take 100 mL of deionized water in a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, then add 0.3 g of MOF crystals, 0.2 g of N-hydroxysuccinimide, 0.2 g of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride, and stir magnetically for 4 h, react at room temperature, after the reaction is completed, add 200 mL of anhydrous ethanol to the above solution to precipitate the unreacted dodecyl dimethyl betaine, then filter, collect the filtrate, and rotary evaporate to remove the solvent to obtain the modified MOF oil displacement agent.

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

[0074] Example 7

[0075] This example provides a modified MOF oil displacement agent, and the preparation method thereof comprises the following steps:

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

[0077] (2) Take 100 mL of deionized water in a beaker to dissolve dodecyl dimethyl betaine to prepare a 1% solution, then add 0.3 g of MOF crystals, 0.2 g of N-hydroxysuccinimide, 0.2 g of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride, and stir magnetically for 4 h, react at room temperature, after the reaction is completed, add 200 mL of anhydrous ethanol to the above solution to precipitate the unreacted dodecyl dimethyl betaine, then filter, collect the filtrate, and rotary evaporate to remove the solvent to obtain the modified MOF oil displacement agent.

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

[0079] Example 8

[0080] The embodiment provides a modified MOF oil displacement agent, and a preparation method of the modified MOF oil displacement agent comprises the following steps.

[0081] (1) 35.0 mmol of 5-amino-1,10-phenanthroline, 150 mL of methanol, stirring to dissolve, 10.0 mmol of FeCl3·6H2O, heating to reflux at 70 DEG C for 2 h, then cooling to room temperature, rotary evaporation of solvent, concentration to 30 mL, 30 mL of anhydrous ether, ultrasonic treatment at room temperature for 2 min, standing for 10 min, allowing the solid to be analyzed, pouring off the solvent, then adding 50 mL of chloroform, ultrasonic treatment at room temperature for 2 min, suction filtration and washing twice, washing off the residual reactants, obtaining a purple red solid compound, then drying in a vacuum drying box for 2 h, weighing, taking the purple red solid compound, dissolving in 50 mL of N,N-dimethylformamide to prepare a solution with a concentration of 0.10%, then evenly pouring the solution into 5 clean 50 mL test tubes, placing in a jar and diffusing and crystallizing with ether, and MOF crystals can be obtained after one month;

[0082] (2) 100 mL of deionized water is taken in a beaker, and dodecyl dimethyl betaine is dissolved to prepare a solution with a concentration of 1%, then 0.3 g of MOF crystals, 0.3 g of N-hydroxysuccinimide and 0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride are added, magnetic stirring is carried out for 4 h, and reaction is carried out at room temperature; after the reaction is completed, 200 mL of anhydrous ethanol is added to the solution to make unreacted dodecyl dimethyl betaine precipitate, then suction filtration is carried out, the filtrate is collected, and the solvent is removed by rotary evaporation to obtain a modified MOF oil displacement agent.

[0083] The modified MOF oil displacement agent prepared in the embodiment is the same as that in Embodiment 1.

[0084] Embodiment 9

[0085] The embodiment provides a modified MOF oil displacement agent, and compared with Embodiment 1, the zwitterionic surfactant is replaced by octadecanamide propyl betaine, and the rest is the same as that in Embodiment 1.

[0086] In the embodiment, octadecanamide propyl betaine is used as the zwitterionic surfactant, the hydrophobic chain of the octadecanamide propyl betaine is long, the water solubility is poor, the water solubility of the modified MOF crystal is affected after grafting modification, and then the use effect of the oil displacement agent is reduced, meanwhile, the cost of using the octadecanamide propyl betaine is high, the industrial cost of the oil displacement agent is increased, and the application value is low.

[0087] The oil displacement effect of the oil displacement agent using the preferred zwitterionic surfactant is good, the zwitterionic surfactant is a common industrial product, the price is cheap, and the application value is high.

[0088] Comparative Example 1

[0089] This comparative example provides a modified MOF oil displacement agent. Compared with Example 1, step (1) is controlled to not involve the diffusion crystallization of MOF solid compounds, while the rest is the same as in Example 1.

[0090] In this comparative example, the MOF solid compound was not subjected to diffusion crystallization, and the resulting product was an amorphous powder that did not have the microstructure of regular circular sheet-like nanosheets. The functional group active sites of the randomly ordered MOF solid compound could not be fully exposed on the outer surface, and effective grafting modification could not be achieved. Therefore, it did not have directional oil displacement performance.

[0091] The infrared spectra of the modified MOF oil displacement agent (denoted as MOF-BS12) prepared in Example 1 of this invention and the MOF crystals (denoted as MOF) prepared in step (1) were measured, as follows: Figure 1 As shown, the infrared spectrum of MOF is at 3400 cm⁻¹ -1 The absorption peak appearing nearby is a characteristic absorption peak of -NH2, at 1600 cm⁻¹. -1 The nearby absorption peaks are characteristic of the C=C ring of the conjugated benzene ring, and the peak at 700 cm⁻¹ is also characteristic. -1 The nearby Fe-N absorption peak indicates that the product synthesized in step (1) is a MOF crystal with iron ions as the central ion and 5-amino-1,10-phenanthroline as the ligand. The modified MOF oil displacement agent is a dodecyl dimethyl betaine grafted onto the MOF crystal. As can be seen from the infrared spectrum, at 2900 cm⁻¹ -1 A distinct absorption peak for the alkyl carbon chain appeared nearby, at 1650 cm⁻¹. -1 The presence of a sharp and strong -C=O absorption peak overlapping the original C=C peak indicates that dodecyl dimethyl betaine was successfully introduced into the MOF crystal.

[0092] The transmission electron microscope (TEM) image of the MOF crystal (denoted as MOF) prepared in step (1) of Example 1 of this invention is shown below. Figure 2 and Figure 3 As shown, the transmission electron microscope (TEM) 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, the microstructure of the MOF crystal is a circular flake with a size distribution between 100-200 nm. The darker black areas in the image are the superposition of multiple nano-discs. The surface of MOF-BS12 is coated with a layer, indicating that dodecyl dimethyl betaine is incorporated into the MOF surface to form an irregular coating film.

[0093] The MOF crystals prepared in step (1) of Example 1 of this invention were prepared as a 0.1% (w / w) MOF solution, mixed and emulsified with kerosene, and allowed to stand for 12 hours. The actual product is as follows: Figure 6As shown in the a tube in the figure, the modified MOF oil displacement agent prepared in Example 1 is formulated into a solution with a mass fraction of 0.02%, 0.04%, 0.06%, 0.08% and 0.1% respectively, the obtained solution is mixed with kerosene to be emulsified and left for 12 hours, and the actual objects are as shown in the b tube, the c tube, the d tube, the e tube and the f tube in the figure. Figure 6 As can be seen from the figure, the color distribution of the lower layer of the a tube is uniform, no enrichment phenomenon and no emulsion layer, the lower layers of the b tube, the c tube, the d tube, the e tube and the f tube all have color depth changes, the color is deeper closer to the upper oil phase, an enrichment phenomenon and a stable emulsion layer appear, which indicates that the MOF without graft modification does not have oil-water interface directionality and emulsification, and the MOF-BS12 with graft modification has oil-water interface enrichment effect and emulsification effect, which indicates that the modified MOF oil displacement agent prepared in the application has oil phase directionality, and when the mass concentration of the modified MOF oil displacement agent is 0.04%, the emulsion layer has the highest height and obvious directional effect.

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

[0095] Table 1

[0096] Oil displacement agent mass concentration (%) Emulsified 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] As can be seen from Table 1, the modified MOF oil displacement agents prepared in Examples 1-8 all have good emulsification effect, when the mass concentration is 0.1%, the emulsion layer height can reach more than 4.9 cm, and the emulsion stability time is more than 3.9 h, which indicates that the modified MOF oil displacement agents prepared in Examples 1-8 all realize grafting of amphoteric surface active agent on the MOF crystal material, and have good oil displacement effect; compared with Example 1, the emulsification effect of the modified MOF oil displacement agent prepared in Comparative Example 1 is quite different, the amphoteric surface active agent is difficult to be successfully grafted on the surface of the MOF solid compound, and cannot achieve effective oil displacement effect.

[0098] In summary, the modified MOF oil displacement agent provided in the application is a circular sheet with regular shape, nanoscale thickness and diameter, which can penetrate into the low-permeability area with more oil; the MOF nanosheet is grafted with amphoteric surface active agent, has oil-water emulsification effect and interface sensitivity, has a “wedge-shaped penetration” effect when migrating in the micropore, has oil phase directionality, can accurately and efficiently shovel off the residual oil adhering to the inner wall of the pore, has strong oil reservoir adaptability, is resistant to temperature and high salinity, and can be applied to harsh and complex oil reservoir conditions.

[0099] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

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 with a zwitterionic surfactant; the MOF crystal material is a single crystal; the organic ligand of the iron-based MOF crystal material comprises 5-amino-1,10-phenanthroline; and the zwitterionic surfactant comprises any one or a combination of at least two of dodecyl dimethyl betaine, lauryl amidopropyl betaine or cocamidopropyl betaine. The modified MOF oil displacement agent is prepared by the following method: (1) mixing and reacting an organic ligand and an iron source to obtain a MOF solid compound, and then diffusing and crystallizing the MOF solid compound to obtain a MOF crystal; (2) mixing and reacting a zwitterionic surfactant, an activating agent and the MOF crystal obtained in step (1) to obtain the modified MOF oil displacement agent; wherein the mass ratio of the zwitterionic surfactant to the MOF crystal is 1:(0.1-0.3), and the activating agent comprises 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and / or N-hydroxysuccinimide.

2. A method of preparing a modified MOF oil displacement agent as claimed in claim 1, characterized by, The preparation method comprises the following steps: (1) mixing and reacting an organic ligand and an iron source to obtain a MOF solid compound, and then diffusing and crystallizing the MOF solid compound to obtain a MOF crystal; (2) mixing and reacting a zwitterionic surfactant, an activating agent and the MOF crystal obtained in step (1) to obtain the modified MOF oil displacement agent.

3. The preparation method according to claim 2, characterized in that, The organic ligand in step (1) comprises 5-amino-1,10-phenanthroline.

4. The production method according to claim 2, characterized by, The iron source in step (1) comprises FeCl3.

5. The preparation method according to claim 2, characterized in that, The molar ratio of the organic ligand to the iron source in step (1) is (2.5-3.5):

1.

6. The method of claim 2, wherein, The method of the reaction in step (1) comprises refluxing.

7. The preparation method according to claim 2, characterized in that, The temperature of the reaction in step (1) is 60-70°C.

8. The preparation method according to claim 2, characterized in that, After the reaction in step (1), the steps of sequentially evaporating the solvent, adding a poor solvent to precipitate the solid and separating the solid and liquid are performed.

9. The preparation method according to claim 8, characterized in that, The poor solvent comprises anhydrous ether.

10. The method of claim 2, wherein, The step of diffusing and crystallizing in step (1) comprises dissolving the MOF solid compound and then crystallizing using a poor solvent.

11. The method of claim 10, wherein, The solvent used for dissolving comprises N,N-dimethylformamide.

12. The method of claim 10, wherein, The concentration of the solution obtained by dissolving is 0.10-0.20%.

13. The preparation method according to claim 10, characterized in that, The poor solvent comprises anhydrous ether.

14. The method of claim 2, wherein, The zwitterionic surfactant in step (2) comprises any one or a combination of at least two of dodecyl dimethyl betaine, lauryl amidopropyl betaine or cocamidopropyl betaine.

15. The preparation method according to claim 2, characterized in that, The activating agent in step (2) comprises 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and / or N-hydroxysuccinimide.

16. The method of claim 2, wherein, The mass ratio of the zwitterionic surfactant to the MOF crystal is 1:(0.1-0.3).

17. The method of claim 2, wherein, The amount of the activating agent is 0.3-0.5 wt% of the sum of the mass of the zwitterionic surfactant, the MOF crystal and the activating agent.

18. Use of the modified MOF oil displacement agent according to claim 1 for tertiary oil recovery.

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