Preparation method and application of micro-nano motor for improving oil reservoir exploitation

Abstract

The invention relates to the technical field of micro-nano motors, in particular to a preparation method and application of a micro-nano motor for improving oil reservoir exploitation. Due to the wheel shape of the micro-nano motor and the hydrophobic modification effect, the micro-nano motor can move in a high-viscosity oil reservoir environment in oil reservoir exploitation. Under the action of a magnetic field, the micro-nano motor can controllably move in a complex three-dimensional core environment, and the size of the micro-nano motor can be reduced when the micro-nano motor encounters a narrower pore throat, so that the micro-nano motor can smoothly pass through the pore throat. When the micro-nano motor makes contact with crude oil drops, the micro-nano motor can carry the oil drops to move and carry the oil drops to a high-permeability area of the oil reservoir, and the motor carrying the oil drops is extracted to the ground along with displacement fluid, so that the recovery rate of the oil reservoir is increased. Meanwhile, the micro-nano motor can be recycled for multiple times.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano motors, and more specifically to a preparation method and application of a micro-nano motor for improving oil reservoir exploitation. Background Art

[0002] Onshore oil fields in China have gradually entered the middle and late stages of oil exploitation. Reservoir areas with relatively low exploitation difficulty, high porosity and permeability have basically been developed. However, a part of the remaining oil (>50%) in old oil fields is distributed in micro-nano pores of complex pore throats and fracture blind ends in the forms of clusters, membranes, blind ends, etc. Therefore, conventional oil production methods (water flooding, polymer flooding) face technical bottlenecks, and the exploitation efficiency of the remaining oil in old oil fields is low. Developing an efficient exploitation technology suitable for low-permeability and micro-nano pore reservoirs is of great significance for ensuring national energy security and promoting the sustainable development of oil exploitation.

[0003] A micro-nano robot is a micro-nano machine at the micro and nano scales that can convert external energies such as light energy, magnetic energy, electrical energy, chemical energy, etc. into its own mechanical energy of motion. Due to the advantages of small size, large thrust-to-weight ratio, good controllability, strong expandability, etc. of micro-nano machines, they have unparalleled superiority in improving the accuracy of oil reservoir detection and exploitation displacement efficiency, and will become the mainstream development technology for future remaining oil reservoir development. However, due to harsh working environments such as high adhesion force, small pore throat diameter, and complex three-dimensional micro-nano pore structures in low-permeability oil reservoirs, it brings great difficulties to the design and driving of micro-nano robots for remaining oil exploitation. Therefore, in order to improve the exploitation rate of remaining oil reservoirs, it is of great significance to prepare a micro-nano motor for improving oil reservoir exploitation. Summary of the Invention

[0004] The present invention provides a preparation method and application of a micro-nano motor for improving oil reservoir exploitation, aiming to improve oil reservoir exploitation.

[0005] The above object is achieved by the following technical solutions:

[0006] A micro-nano motor includes a micro-wheel formed by magnetic aggregation of superhydrophobic magnetic nanoparticles.

[0007] The superhydrophobic magnetic nanoparticles include magnetic nanoparticles 1 and a superhydrophobic layer 2 coated on the magnetic nanoparticles 1.

[0008] The overall contour shape of the micro-wheel is circular.

[0009] The diameter of the magnetic nanoparticles 1 is 100 nm - 800 nm.

[0010] A preparation method of a micro-nano motor:

[0011] Step 1: Put magnetic nanoparticles 1 into absolute ethanol. After mixing evenly, add dopamine hydrochloride and hydrochloric acid buffer solution with a pH value of 8 - 10. After mixing and reacting, wash it clean. The mass ratio of magnetic nanoparticles 1 to dopamine hydrochloride is 1:3 to 1:6, and the volume ratio of absolute ethanol to hydrochloric acid buffer solution is 1:0.5 to 1:1.5;

[0012] Step 2: Put the washed product into a mixed solution with a volume ratio of absolute ethanol to perfluorodecanethiol of 500:1 to 1500:1 for reaction, and then wash and dry it to obtain superhydrophobic magnetic nanoparticles formed by magnetic nanoparticles 1 as the core and a shell with a superhydrophobic layer 2;

[0013] Step 3: Under the action of a magnetic field, aggregate the superhydrophobic magnetic nanoparticles into dense micro - wheels to obtain a micro - nano motor 3.

[0014] The magnetic nanoparticles 1 are magnetite.

[0015] Dopamine hydrochloride and hydrochloric acid buffer solution are mixed by ultrasound for 3 - 6 hours.

[0016] The reaction time in the mixed solution is 20 - 30 hours.

[0017] The pH value of the hydrochloric acid buffer solution is 8.5, the mass ratio of magnetite nanoparticles to dopamine hydrochloride is 1:3.8, the volume ratio of absolute ethanol to hydrochloric acid buffer solution is 1:1, and the washed product is put into a mixed solution with a volume ratio of absolute ethanol to perfluorodecanethiol of 1000:1.

[0018] The micro - nano motor is applied to improve oil reservoir exploitation. Under the action of a magnetic field, the micro - nano motor 3 moves in the three - dimensional core 8 environment. When it encounters a pore throat 6, the micro - nano motor 3 can become a micro - wheel micro - nano motor 5 with a smaller diameter and thus smoothly pass through the pore throat 6. When the micro - nano motor 3 comes into contact with crude oil droplets 7, it will carry the droplets and move, and carry the droplets to the high - permeability area of the oil reservoir. The micro - nano motor 3 carrying the droplets is produced to the ground by the displacement fluid from the production well 10.

[0019] The beneficial effects of the preparation method and application of a micro - nano motor for improving oil reservoir exploitation in the present invention are as follows:

[0020] Superhydrophobic magnetite nanoparticles aggregated by magnetic force to form micro-nano motors can move flexibly in the highly viscous reservoir environment. To prepare such micro-nano motors, a suspension is obtained by mixing superhydrophobic magnetite nanoparticles with deionized water. The suspension is then mixed with a displacement fluid and injected into the formation reservoir from an injection well. Under the action of a magnetic field, the superhydrophobic magnetite nanoparticles aggregate into micro-nano motors. The manufacturing cost is reasonable and it has practical production value. Due to the wheel-like shape of the micro-nano motors and the effect of hydrophobic modification, the micro-nano motors can move in the highly viscous reservoir environment during oil reservoir exploitation. Under the action of a magnetic field, the micro-nano motors can move controllably in a complex three-dimensional core environment. When encountering narrower pore throats, the micro-nano motors can reduce their size and pass through smoothly. When the micro-nano motors come into contact with crude oil droplets, they will carry the droplets and move them to the high-permeability area of the reservoir. The motors carrying the droplets are produced to the ground with the displacement fluid, thereby increasing the oil recovery rate of the reservoir. At the same time, these micro-nano motors can be recycled and reused multiple times. Brief Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the structure of superhydrophobic magnetite nanoparticles;

[0022] Figure 2 It is a schematic diagram of the micro-nano motor;

[0023] Figure 3 It is a schematic diagram of the movement of the micro-nano motor in a three-dimensional core environment;

[0024] Figure 4 It is a schematic diagram of the application of the micro-nano motor in oil production engineering.

[0025] In the figure: 1, magnetite; 2, superhydrophobic layer; 3, micro-nano motor; 4, large-sized micro-nano motor; 5, small-sized micro-nano motor; 6, pore throat; 7, crude oil droplet; 8, three-dimensional core; 9, injection well; 10, production well; 11, target reservoir area. Detailed Description of the Invention

[0026] Example 1 of a preparation method of a micro-nano motor for improving oil reservoir exploitation:

[0027] (1) Put magnetite nanoparticles with a diameter of 100 nm - 800 nm into absolute ethanol, ultrasonically mix evenly, then add a hydrochloric acid buffer solution with a pH value of 8.5 and dopamine hydrochloride, and ultrasonically mix and react for 5 hours. After the reaction, wash it clean. The mass ratio of magnetite nanoparticles to dopamine hydrochloride is 1:3.8, and the volume ratio of absolute ethanol to hydrochloric acid buffer solution is 1:1.

[0028] (2) Place the washed product into a mixed solution of absolute ethanol and perfluorodecanethiol with a volume ratio of 1000:1 and react for 24 hours. After the reaction, wash and dry to obtain superhydrophobic iron oxide nanoparticles with a core of iron oxide nanoparticles and a shell of a superhydrophobic layer 2.

[0029] (3) Under the action of a magnetic field, aggregate the superhydrophobic iron oxide nanoparticles into dense micro-wheels to obtain a micro-nano motor 3 for improving oil reservoir exploitation.

[0030] Example 2:

[0031] Based on Example 1, when the iron oxide nanoparticles are replaced with magnetic nanoparticles such as iron oxide, due to the differences in the hysteresis loop, especially the saturation magnetization intensity, it is difficult to aggregate into dense micro-wheels under the action of a uniform rotating magnetic field, and the effect is poor.

[0032] Example 3:

[0033] Based on Example 1, when the pH value of the hydrochloric acid buffer solution is 6.8, it affects the aggregation reaction of dopamine hydrochloride and reduces the hydrophobic ability of the micro-nano motor 3.

[0034] Example 4:

[0035] Based on Example 1, when the mass ratio of iron oxide nanoparticles to dopamine hydrochloride is 1:7, the thickness of the superhydrophobic layer is increased, thereby reducing the saturation magnetization intensity of the superhydrophobic magnetic nanoparticles and affecting the ability to aggregate into dense micro-wheels under the action of a uniform rotating magnetic field.

[0036] Example 5:

[0037] Based on Example 1, when the volume ratio of the absolute ethanol to the hydrochloric acid buffer solution is 1:2, the dispersibility of the magnetic nanoparticles during the reaction will be reduced, and magnetic nanoparticles with poor monodispersity will be obtained, affecting the ability to aggregate into dense micro-wheels under the action of a uniform rotating magnetic field.

[0038] A method for improving oil reservoir exploitation:

[0039] A suspension and a displacement fluid are prepared by mixing superhydrophobic iron tetroxide nanoparticles with deionized water. The displacement fluid is a fluid used to drive crude oil from a reservoir to a production well, such as ordinary water flooding, polymer flooding, etc. After mixing, it is injected into the formation reservoir 11 from the injection well 9. Under the action of a magnetic field, the superhydrophobic iron tetroxide nanoparticles aggregate into microwheels, i.e., the micro-nano motor 3 is obtained. The size of the micro-nano motor 3 can be increased as needed to aggregate into a large-size micro-nano motor 4. Under the action of a magnetic field, the large-size micro-nano motor 4 can achieve controllable motions such as climbing over obstacles, adjusting the motion direction, and climbing slopes in a complex three-dimensional core 8 environment. When encountering a narrower pore throat 6, the uniform rotating magnetic field can be changed to a direct current magnetic field. Under the action of the direct current magnetic field, the large-size micro-nano motor 4 will be broken up from the dense microwheels into superhydrophobic magnetic nanoparticles. Then, the direct current magnetic field is changed to a rotating magnetic field, and at the same time, the magnetic field intensity and frequency of the rotating magnetic field are changed. The superhydrophobic iron tetroxide nanoparticles can aggregate into small-size micro-nano motors 5 with a smaller diameter and thus pass through smoothly. When the micro-nano motor 3 comes into contact with the crude oil droplet 7, it will carry the oil droplet and move, and carry the oil droplet to the high-permeability area of the reservoir. The micro-nano motor carrying the oil droplet is produced to the ground from the production well 10 along with the displacement fluid. The produced fluid is subjected to solid-liquid centrifugal separation, and the separated liquid is separated by electromagnetic water-oil separation to obtain crude oil. The separated micro-nano motor 3 can be reused.

Claims

1. A micro-nano motor, comprising a micro-wheel formed by the magnetic aggregation of superhydrophobic magnetic nanoparticles.

2. The micro-nano motor according to claim 1, wherein the superhydrophobic magnetic nanoparticles comprise magnetic nanoparticles 1 and a superhydrophobic layer 2 coated on the magnetic nanoparticles 1.

3. The micro-nano motor according to claim 1 or 2, wherein the overall contour shape of the micro-wheel is circular.

4. The micro-nano motor for improving oil reservoir exploitation according to claim 1, wherein the diameter of the magnetic nanoparticles 1 is 100 nm - 800 nm.

5. A preparation method of a micro-nano motor, characterized in that: Step 1: Put the magnetic nanoparticles 1 into absolute ethanol, mix evenly, then add dopamine hydrochloride and a hydrochloric acid buffer solution with a pH value of 8 - 10, mix and react, and then wash clean. The mass ratio of the magnetic nanoparticles 1 to dopamine hydrochloride is 1:3 to 1:6, and the volume ratio of absolute ethanol to the hydrochloric acid buffer solution is 1:0.5 to 1:1.5; Step 2: Put the washed product into a mixed solution with a volume ratio of absolute ethanol to perfluorodecanethiol of 500:1 to 1500:1, react and then wash and dry to obtain superhydrophobic magnetic nanoparticles formed by using the magnetic nanoparticles 1 as the core and a shell with a superhydrophobic layer 2; Step 3: Under the action of a magnetic field, aggregate the superhydrophobic magnetic nanoparticles into a dense micro-wheel to obtain the micro-nano motor 3.

6. The preparation method of the micro-nano motor according to claim 5, wherein the magnetic nanoparticles 1 are magnetite.

7. The preparation method of the micro-nano motor according to claim 5, wherein dopamine hydrochloride and the hydrochloric acid buffer solution are ultrasonically mixed for 3 - 6 hours.

8. The preparation method of the micro-nano motor according to claim 5, wherein the reaction time in the mixed solution is 20 - 30 hours.

9. The preparation method of the micro-nano motor according to claim 5, wherein the pH value of the hydrochloric acid buffer solution is 8.5, the mass ratio of the magnetite nanoparticles to dopamine hydrochloride is 1:3.8, the volume ratio of absolute ethanol to the hydrochloric acid buffer solution is 1:1, and the washed product is put into a mixed solution with a volume ratio of absolute ethanol to perfluorodecanethiol of 1000:

1.

10. The micro-nano motor according to claim 1, characterized in that, Applied to improve oil reservoir exploitation, under the action of a magnetic field, the micro-nano motor 3 moves in the three-dimensional core 8 environment. When encountering the pore throat 6, the micro-nano motor 3 can become a micro-wheel micro-nano motor 5 with a smaller diameter and thus smoothly pass through the pore throat 6. When the micro-nano motor 3 contacts the crude oil droplet 7, it will carry the oil droplet and move, and carry the oil droplet to the high-permeability area of the oil reservoir. The micro-nano motor 3 carrying the oil droplet is produced to the ground by the production well 10 along with the displacement fluid.

Images