A flushing fluid for shale reservoir wellbores and a method of making the same

Abstract

The present application relates to a kind of flushing fluid for shale reservoir well wall and its preparation method, the preparation method includes that organic amine and organic acid or its sodium salt are reacted to obtain carbon-based nanomaterial, carbon-based nanomaterial is mixed with sodium alpha-olefin sulfonate and ultrapure water, to obtain the flushing fluid for shale reservoir well wall.The flushing fluid for shale reservoir well wall prepared by the present application is a kind of nanofluid flushing fluid based on activated carbon point, can effectively strip the residual drilling fluid on the surface of well wall rock and improve well wall rock wettability, improve cementing quality, and can effectively improve the oil washing efficiency for residual drilling fluid, improve the cementing quality of well wall and cement sheath.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of shale oil development, in particular to a flushing fluid for shale reservoir well wall and a preparation method thereof, and especially to a flushing fluid suitable for removing residual oil-based drilling fluid from shale reservoir well wall and a preparation method thereof. BACKGROUND

[0002] With the development of global oil and gas resource exploration, such as deep water, deep land, unconventional resources, etc., the formation drilled in drilling engineering is more and more complex, and the drilling operation is more and more difficult. Oil-based drilling fluid has great advantages in some formations, especially in offshore environment and shale reservoirs, due to its high hole stability, good temperature stability, strong anti-pollution and good lubricity. The excellent shale inhibition, permeability and hole stability of oil-based drilling fluid help to achieve trouble-free and safe drilling operation. Therefore, oil-based drilling fluid is widely used in the drilling of shale oil and gas reservoirs, deep wells and other key or difficult wells.

[0003] However, the use of oil-based drilling fluid in the drilling process will seriously affect the subsequent well operation, such as cement quality or mud pollution. The organic components in the residual drilling fluid will adhere to the shale reservoir well wall, making the surface of the well wall rock become hydrophobic, which will affect the hydration and crystallization of the cement slurry minerals on the surface of the well wall in the subsequent cementing operation, thereby reducing the bonding strength between the cement sheath and the well wall and the cementing quality. How to effectively remove the residual drilling fluid from the shale reservoir well wall to improve the cementing quality is a difficult problem in shale oil exploitation. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a flushing fluid for shale reservoir well wall and a preparation method thereof. The flushing fluid for shale reservoir well wall provided by the present application is a nanofluid flushing fluid based on activated carbon dots, which can effectively strip the residual drilling fluid from the surface of the well wall rock and improve the wettability of the well wall rock, improve the cementing quality, and effectively improve the oil washing efficiency of the residual drilling fluid and the cementing quality of the well wall and the cement sheath.

[0005] In the first aspect, the present application provides a preparation method of a flushing fluid for shale reservoir well wall, which comprises reacting an organic amine and an organic acid or a sodium salt thereof to obtain a carbon-based nanomaterial, mixing the carbon-based nanomaterial with sodium alpha-olefin sulfonate and ultrapure water to obtain the flushing fluid for shale reservoir well wall.

[0006] The carbon-based nanomaterial prepared by the method of the present application has a spherical structure and an ultra-small nanoparticle size, and its structure is as follows:

[0007]

[0008] The flushing fluid for well wall prepared based on the carbon-based nanomaterial of the application is an active carbon dot nanofluid flushing fluid, and its structure is shown as follows:

[0009]

[0010] The flushing fluid for well wall of shale reservoir prepared by the application has good wetting regulation ability, can change the wettability of the rock surface, improve the oil film stripping capacity, and meanwhile, the hydrophilic functional groups on the surface of the nanoparticles can better cement with the well cement, thereby improving the cementing quality of the well cement interface.

[0011] As a preferred technical solution of the application, the organic amine is selected from any one or combination of at least two of urea, 1,3-propanediamine or 1,2-propanediamine.

[0012] As a preferred technical solution of the application, the organic amine is urea.

[0013] As a preferred technical solution of the application, the organic acid or sodium salt thereof is selected from any one or combination of at least two of citric acid, tartaric acid or L-ascorbic acid sodium.

[0014] As a preferred technical solution of the application, the organic acid or sodium salt thereof is citric acid.

[0015] The carbon-based nanomaterial prepared by the organic amine and the organic acid or sodium salt thereof has excellent interface regulation ability and wetting regulation ability, can effectively reduce the interfacial tension, improve the oil-water interface activity, and can improve the wettability of the shale surface to hydrophilicity.

[0016] As a preferred technical solution of the application, the reaction is carried out in solvent water, and the solvent water is ultrapure water.

[0017] Before the reaction of the organic amine and the organic acid or sodium salt thereof, high-purity nitrogen gas is introduced into the solvent water to remove impurity gas, the aeration time is 10-20 min, and the organic amine, the organic acid or sodium salt thereof is fully dissolved under stirring, and preferably the stirring rate is 4000-6000 r / min.

[0018] As a preferred technical solution of the application, the mass ratio of the organic amine, the organic acid or sodium salt thereof and the solvent water is (2-5):(2-7):(40-50), for example, 2:3:40, 3:4:40, 4:5:40, 5:6:40, 2:2:45, 3:4:50, etc.

[0019] As a preferred technical solution of the application, the pH during the reaction is 6-6.5.

[0020] As a preferred technical solution of the present application, the pH in the reaction is adjusted by using hydrochloric acid.

[0021] As a preferred technical solution of the present application, the temperature of the reaction is 180-220℃, for example, 190℃, 200℃, 210℃, etc.

[0022] The preparation method provided by the present application is that the organic amine, organic acid or sodium salt thereof is heated and decomposed under the temperature condition of the present application to form a new spherical structure with carbon atom as the center.

[0023] As a preferred technical solution of the present application, the reaction time is 6-10h, for example, 7h, 8h, 9h, etc.

[0024] When the reaction time is within the range of the present application, the carbon-based nanomaterial particles prepared have a smaller particle size.

[0025] As a preferred technical solution of the present application, the particle size of the carbon-based nanomaterial is 2-8nm, for example, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, etc., preferably 2-4nm.

[0026] As a preferred technical solution of the present application, the preparation method further comprises purifying, freezing and drying the organic amine and organic acid or sodium salt thereof after the reaction.

[0027] The present application first performs ultrasonic treatment on the crude product obtained by cooling the organic amine and organic acid or sodium salt thereof after the reaction for 20-30min, and then performs purification, freezing and drying.

[0028] As a preferred technical solution of the present application, the purification method comprises sequentially performing centrifugation and dialysis. The present application collects the supernatant after centrifugation of the obtained crude product, and then performs dialysis by using a dialysis bag.

[0029] As a preferred technical solution of the present application, the rotation speed of the centrifugation is 8000r / min.

[0030] As a preferred technical solution of the present application, the permeability of the dialysis is 1000Da.

[0031] As a preferred technical solution of the present application, the dialysis time is 48-72h, for example, 50h, 55h, 60h, 65h, 70h, etc.

[0032] As a preferred technical solution of the present application, the mass ratio of the carbon-based nanomaterial, sodium alpha-olefin sulfonate and ultrapure water is (1-1.5):(2-3):(995.5-997), for example, 1:2:997, 1:3:996, 1.5:2:996.5, 1.5:3:995.5, etc.

[0033] The mass of the carbon-based nanomaterial, sodium alpha-olefin sulfonate and ultrapure water in the present application is 1000 parts by weight.

[0034] As a preferred technical solution of the present application, the mixing is carried out under stirring, and preferably the stirring rate is 8000 r / min.

[0035] As a specific embodiment of the present application, the preparation method comprises:

[0036] (1) reacting organic amine, organic acid or its sodium salt in solvent water, with pH being 6-6.5, reaction temperature being 180-220 DEG C, reaction time being 6-10 h, to obtain a crude product, which is purified, frozen and dried to obtain a carbon-based nanomaterial, the mass ratio of the organic amine, organic acid or its sodium salt, solvent water being (2-5):(2-7):(40-50);

[0037] (2) mixing carbon-based nanomaterial, sodium alpha-olefin sulfonate and ultrapure water according to the mass ratio of (1-1.5):(2-3):(995.5-997) to obtain the flushing fluid for shale reservoir well wall.

[0038] In the second aspect, the present application provides a flushing fluid for shale reservoir well wall prepared by the preparation method of the first aspect.

[0039] After drilling with an oil-based drilling fluid, flushing the well wall with the flushing fluid for shale reservoir well wall provided by the present application can effectively strip the residual drilling fluid on the surface of the well wall rock and improve the wettability of the well wall rock, improve the cementing quality, and effectively improve the oil washing efficiency of the residual drilling fluid and improve the cementing quality of the well wall and the cement sheath.

[0040] Compared with the prior art, the technical solution provided by the embodiments of the present application has the following advantages:

[0041] The flushing fluid for shale reservoir well wall prepared by the present application is a nanofluid flushing fluid based on activated carbon dots, which can effectively strip the residual drilling fluid on the surface of the well wall rock and improve the wettability of the well wall rock, improve the cementing quality, and effectively improve the oil washing efficiency of the residual drilling fluid and improve the cementing quality of the well wall and the cement sheath. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings, which are incorporated into and constitute a part of the specification, illustrate preferred embodiments of the present application and, together with the description, serve to explain the principles of the application.

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0044] Figure 1 XPS photoelectron characterization results of the carbon-based nanomaterial prepared in Example 1 of the present application;

[0045] Figure 2 FT-IR graph of the carbon-based nanomaterial prepared in Example 1 of the present application;

[0046] Figure 3 HRTEM characterization results of the carbon-based nanomaterial prepared in Example 1 of the present application;

[0047] Figure 4 Interface tension test results of carbon-based nanofluid dispersions with different concentrations of the present application;

[0048] Figure 5 Wetting regulation ability test results of carbon-based nanofluid dispersions with different concentrations of the present application. DETAILED DESCRIPTION

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0050] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced without the specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the present application.

[0051] Example 1

[0052] The present embodiment provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, and the preparation method comprises the following steps:

[0053] (1) Dissolve 4 g of urea in 40 g of solvent water, and pass high-purity nitrogen gas for 10-20 min to remove dissolved impurity gas; magnetically stir at a speed of 5000 r / min, add 4 g of citric acid, stir uniformly, and then add hydrochloric acid to adjust the pH to 6.0-6.5;

[0054] The mixture was transferred to a high-pressure reactor and reacted at 200°C for 8 hours. After natural cooling, the product solution was sonicated for 25 minutes and then centrifuged at 8000 r / min for 120 minutes. The supernatant was dialyzed for 48 hours using a dialysis bag with a permeability of 1000 Da and then freeze-dried to obtain carbon-based nanomaterials.

[0055] (2) Dissolve the carbon-based nanomaterials obtained in step (1) in ultrapure water, and introduce high-purity nitrogen gas for 10-20 min to remove dissolved impurity gases; stir magnetically at 8000 r / min, and add sodium α-olefin sulfonate under stirring until fully dissolved to obtain the flushing fluid for the shale reservoir well wall, wherein the mass ratio of the carbon-based nanomaterials, sodium α-olefin sulfonate and ultrapure water is 1:2:997.

[0056] Example 2

[0057] This embodiment provides a flushing fluid for shale reservoir wellbore and its preparation method. The preparation method is the same as that in Example 1, except that the reaction time in step (1) is 6 hours.

[0058] Example 3

[0059] This embodiment provides a flushing fluid for shale reservoir wellbore and its preparation method. The preparation method is the same as that in Example 1, except that the reaction temperature in step (1) is 180°C.

[0060] Example 4

[0061] This embodiment provides a flushing fluid for shale reservoir wellbore and its preparation method. The preparation method is the same as that in Example 1. The difference from Example 1 is that the amount of urea used in step (1) is 5g.

[0062] Example 5

[0063] This embodiment provides a flushing fluid for shale reservoir wellbore and its preparation method. The preparation method is the same as that in Example 1, except that the amount of citric acid used in step (1) is 6g.

[0064] Example 6

[0065] This embodiment provides a flushing fluid for shale reservoir wellbore and its preparation method. The preparation method is the same as that in Example 1. The difference from Example 1 is that the mass ratio of carbon-based nanomaterials, sodium α-olefin sulfonate and ultrapure water in step (2) is 1:3:996.

[0066] Example 7

[0067] The present example provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, wherein the preparation method is the same as that of Example 1, and the difference from Example 1 is that citric acid is replaced by tartaric acid in step (1).

[0068] Example 8

[0069] The present example provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, wherein the preparation method is the same as that of Example 1, and the difference from Example 1 is that the reaction time is 10h in step (1).

[0070] Example 9

[0071] The present example provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, wherein the preparation method is the same as that of Example 1, and the difference from Example 1 is that the reaction temperature is 220℃ in step (1).

[0072] Comparative Example 1

[0073] The present comparative example provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, wherein the preparation method is the same as that of Example 1, and the difference from Example 1 is that the reaction time is 3h in step (1).

[0074] Comparative Example 2

[0075] The present comparative example provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, wherein the preparation method is the same as that of Example 1, and the difference from Example 1 is that the reaction temperature is 140℃ in step (1).

[0076] Comparative Examples 3-4

[0077] The present comparative example provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, wherein the preparation method is the same as that of Example 1, and the difference from Example 1 is that the amount of urea is 1g (Comparative Example 3) or 7g (Comparative Example 4) in step (1).

[0078] Comparative Examples 5-6

[0079] The present comparative example provides a flushing fluid for shale reservoir wellbore and a preparation method thereof, wherein the preparation method is the same as that of Example 1, and the difference from Example 1 is that the amount of citric acid is 1g (Comparative Example 5) or 8g (Comparative Example 6) in step (1).

[0080] Comparative Examples 7-8

[0081] The comparative example provides a flushing fluid for shale reservoir well wall and a preparation method thereof, the preparation method is the same as that of Example 1, and the difference from Example 1 is that the mass ratio of the carbon-based nanomaterial, sodium a-olefin sulfonate and ultrapure water in step (2) is 1:5:994 (comparative example 7) or 3:2:995 (comparative example 8).

[0082] Comparative example 9

[0083] The comparative example provides a flushing fluid for shale reservoir well wall and a preparation method thereof, the preparation method is the same as that of Example 1, and the difference from Example 1 is that the carbon-based nanomaterial, sodium a-olefin sulfonate and ultrapure water in step (2) are not added.

[0084] Comparative example 10

[0085] The comparative example provides a flushing fluid for shale reservoir well wall and a preparation method thereof, the preparation method is the same as that of Example 1, and the difference from Example 1 is that the carbon-based nanomaterial, sodium a-olefin sulfonate and ultrapure water in step (2) are not added.

[0086] Performance test 1

[0087] The carbon-based nanomaterials prepared in Examples 1-9 and Comparative Examples 1-10 are characterized by using an XPS photoelectron spectrometer, and the results show that the carbon-based nanomaterials contain C, N, O and H elements;

[0088] The XPS photoelectron characterization results of the carbon-based nanomaterial prepared in Example 1 are shown in Figure 1 .

[0089] Performance test 2

[0090] The carbon-based nanomaterials prepared in Examples 1-9 and Comparative Examples 1-10 are characterized by using an FT-IT infrared spectrometer, and the results show that the carbon-based nanomaterials contain carboxyl and amino groups;

[0091] The FT-IR graph of the carbon-based nanomaterial prepared in Example 1 is shown in Figure 2 .

[0092] Performance test 3

[0093] The carbon-based nanomaterials prepared in Examples 1-9 and Comparative Examples 1-10 are observed by using an HRTEM high-power lens electron microscope, and the results show that the carbon-based nanomaterials have a spherical structure;

[0094] The HRTEM characterization results of the carbon-based nanomaterial prepared in Example 1 are shown in Figure 3 .

[0095] The particle sizes of the carbon-based nanomaterials prepared in Examples 1-9 and Comparative Examples 1-10 are shown in Table 1:

[0096] Table 1

[0097]

[0098]

[0099] It can be found from Table 1 that the particle size of the carbon-based nanomaterial prepared by the application is between 2-8 nm, and is optimally between 2-4 nm, having an ultra-small particle size.

[0100] Performance test 4

[0101] The interface regulation ability of the carbon-based nanomaterial prepared in Example 1 was tested.

[0102] Simulated oil composition: white oil and kerosene were configured according to a mass ratio of 2:1, the viscosity of the simulated oil was 6.18 mPa·s, and the density was 0.78 g / cm 3 .

[0103] The carbon-based nanomaterial prepared in Example 1 was diluted with water to obtain carbon-based nanofluid dispersions with different concentrations, and the interface tension between the simulated oil and the carbon-based nanofluid dispersions with different concentrations was tested, and the results are shown in Table 2 and Figure 4 . Figure 4 Table 2 shows the interface tension test results of carbon-based nanofluid dispersions with different concentrations.

[0104] Table 2

[0105]

[0106] It can be known from Table 2 and Figure 4 that the carbon-based nanofluid dispersion prepared based on the carbon-based nanomaterial of the application can effectively reduce the interface tension and improve the oil-water interface activity.

[0107] Performance test 5

[0108] The wetting regulation ability of the carbon-based nanomaterial prepared in Example 1 was tested.

[0109] The carbon-based nanomaterial prepared in Example 1 was diluted with water to obtain carbon-based nanofluid dispersions with different concentrations.

[0110] Simulated oil composition: white oil and kerosene were configured according to a mass ratio of 2:1, the viscosity of the simulated oil was 6.18 mPa·s, and the density was 0.78 g / cm3 .

[0111] Test method:

[0112] (1) The shale core was treated into a shale sheet with a thickness of 5 mm and was placed in simulated oil for static immersion for 24 h to change the wettability of the core surface;

[0113] (2) The shale sheet was taken out and was immersed in a dispersion liquid with different concentrations for 24 h.

[0114] (3) The shale sheet was taken out, and a contact angle measuring instrument was used to measure the water wetting angle of the shale sheet.

[0115] The results are shown in Table 3 and Figure 5 , Figure 5 which are the wettability regulation ability test results of carbon-based nanofluid dispersion liquids with different concentrations.

[0116] Table 3

[0117] Concentration / wt% 0 0.01 0.05 0.1 0.2 0.5 1.0 Contact angle / ° 141 109 89 68 59 44 36

[0118] As can be seen from Table 3 and Figure 5 , the carbon-based nanofluid dispersion liquid prepared based on the carbon-based nanomaterials of the application has good wettability regulation ability and can change the wettability of the shale surface from oil-wet to water-wet.

[0119] Performance test 6

[0120] The oil film removal ability of the flushing liquid for a shale reservoir well wall prepared by Examples 1-9 and Comparative Examples 1-10 was tested.

[0121] A six-speed rotational viscometer was used to evaluate the oil film removal ability of the flushing liquid for a well wall, and the experimental steps were as follows: ① The mass of the rotor was weighed and recorded as M1. Then the rotor was immersed in a certain height of synthetic base drilling fluid, and the mass of the rotor was weighed again and recorded as M2. ② 300 mL of the liquid to be tested (the well wall flushing liquid prepared by Examples 1-9 and Comparative Examples 1-10) or ultrapure water (blank example) was added to the rotating cup. ③ Rotate at 300 r / min for 30 min. After the experiment, the rotor was taken out and weighed, and the mass was recorded as M3. The experimental results are shown in Table 4.

[0122] The removal efficiency of the synthetic base drilling fluid was calculated according to the following formula:

[0123]

[0124] In the formula, η is the removal efficiency of the synthetic base drilling fluid, %;

[0125] M1: rotor weight, g;

[0126] M2: total mass of the rotor and the drilling fluid, g;

[0127] M3: the total mass of the residual synthetic base drilling fluid added to the rotating drum after the cleaning is completed, g.

[0128] Table 4

[0129]

[0130]

[0131] As shown in Table 4, the flushing fluid for shale reservoir well walls prepared by the present application has excellent oil film removal capacity, and the removal efficiency can be up to 85% or more.

[0132] Performance test 7

[0133] The effect of the flushing fluid for shale reservoir well walls prepared by Examples 1-9 and Comparative Examples 1-10 on the cementing quality of the second interface was tested.

[0134] Preparation of the cementing slurry: cement and water were mixed in a mass ratio of 100:40 and stirred uniformly to obtain the cementing slurry.

[0135] Experimental procedure: ① The steel casing was placed in the synthetic base drilling fluid at the same height for a certain period of time. ② The casing was taken out and flushed with different flushing fluids for well walls (the flushing fluids for well walls prepared by Examples 1-9 and Comparative Examples 1-10) or ultrapure water (blank example) for 30 min. ③ The flushed casing was placed in a mold, the cementing slurry was poured, and then placed in a constant temperature water bath at 80℃ for curing. ④ The second interface cementing strength was tested on the 3rd, 7th, 14th, and 28th day of the curing process. The results are shown in Table 5.

[0136] Table 5

[0137]

[0138]

[0139] As shown in Table 5, the flushing fluid for shale reservoir well walls prepared by the present application can effectively improve the second interface cementing strength, and the second interface cementing strength is improved by 200% or more after 28 days of curing.

[0140] It has to be noted that, in the present document, the terms "first", "second", etc. merely serve the purpose of distinguishing between two entities or operations, without necessarily requiring or implying any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "containing" or any other transitional term, do not exclude other matters besides the one(s) named, nor do they preclude the presence or addition of one or more other elements or interventions. Without more limitations, an element defined by the phrase "comprising a... " does not exclude the presence of additional identical elements in the process, method, article, or apparatus including the one(s) defined by the phrase "comprising a... ".

[0141] The foregoing is considered as illustrative only of the principles of the application. Numerous modifications and changes will readily occur to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Accordingly, the scope of the application is intended to be defined only as set forth in the claims.

Claims

1. A method for preparing a flushing fluid for use in shale reservoir wellbores, characterized by, The preparation method comprises the following steps: reacting an organic amine and an organic acid or a sodium salt thereof to obtain a carbon-based nanomaterial, and mixing the carbon-based nanomaterial, sodium α-olefin sulfonate and ultrapure water to obtain the flushing fluid for a shale reservoir well wall. The organic amine is selected from any one or a combination of at least two of urea, 1,3-propanediamine or 1,2-propanediamine. The organic acid or the sodium salt thereof is selected from any one or a combination of at least two of citric acid or tartaric acid.

2. The production method according to claim 1, characterized by, The organic amine is urea.

3. The production method according to claim 1 or 2, characterized by, The organic acid or the sodium salt thereof is citric acid.

4. The production method according to claim 1 or 2, characterized by, The reaction is carried out in solvent water.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the organic amine, the organic acid or the sodium salt thereof and the solvent water is (2-5):(2-7):(40-50).

6. The production method according to claim 1 or 2, characterized by, The pH during the reaction is 6-6.

5.

7. The production method according to claim 6, wherein The pH during the reaction is adjusted by using hydrochloric acid.

8. The production method according to claim 1 or 2, characterized by, The temperature of the reaction is 180-220 DEG C. The time of the reaction is 6-10 h.

9. The production method according to claim 1 or 2, characterized by, The preparation method further comprises purifying, freezing and drying the carbon-based nanomaterial after the reaction of the organic amine and the organic acid or the sodium salt thereof.

10. The method of claim 9, wherein, The purification method comprises sequentially performing centrifugation and dialysis.

11. The method of claim 10, wherein, The rotation speed of the centrifugation is 8000 r / min. The permeation rate of the dialysis is 1000 Da. The time of the dialysis is 48-72 h.

12. The production method according to claim 1 or 2, characterized by, The mass ratio of the carbon-based nanomaterial, sodium α-olefin sulfonate and ultrapure water is (1-1.5):(2-3):(995.5-997).

13. The flushing fluid for a shale reservoir well wall prepared by the preparation method in any one of claims 1-12.

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