High-temperature and high-pressure filtrate reducer sulfonated asphalt for drilling fluid and preparation method of high-temperature and high-pressure filtrate reducer sulfonated asphalt

Abstract

The invention discloses high-temperature and high-pressure filtrate reducer sulfonated asphalt for drilling fluid and a preparation method of the high-temperature and high-pressure filtrate reducer sulfonated asphalt, and belongs to the technical field of filtrate reducers. A comb-shaped side chain is introduced into a benzene ring of SEBS, the benzene ring is endowed with a comb-shaped structure, the structure strongly interacts with sulfonated asphalt, asphalt dispersion is optimized, agglomeration is avoided, 5-(2-hydroxyethyl) uracil is introduced, the oleophylic and hydrophilic characteristics are balanced, the acting force between asphalt particles is reduced, the reaction efficiency and uniformity of asphalt and fuming sulfuric acid are improved, and the sulfonated asphalt is prepared. The dispersant promotes uniform dispersion of asphalt, accelerates sulfonation reaction and improves sulfonated asphalt quality. The surface activity of the modified SEBS and the sulfonated asphalt form a net structure, so that the water solubility of the asphalt is enhanced, the drilling fluid is convenient to blend, the liquid surface tension is reduced, and the bubble formation condition is destroyed. A quaternary ammonium salt group is introduced, a well wall is stabilized by utilizing an opposite attraction principle, clay hydrophobicity is promoted, hydration and expansion are inhibited, and collapse is prevented. The modified sulfonated asphalt is resistant to temperature and pressure, good in filtration resistance and stable in filtration control at high temperature and high pressure.

Description

Technical Field

[0001] The invention belongs to the technical field of fluid loss reducers, and in particular relates to a high-temperature and high-pressure fluid loss reducer sulfonated asphalt for drilling fluid and a preparation method thereof. Background Art

[0002] During the drilling process, the instability of the wellbore frequently occurs, which not only causes a series of complex underground conditions, such as formation collapse and diameter shrinkage, but may even induce serious engineering accidents, which greatly reduces the progress of the project and has a great negative impact on the economic benefits. The root cause of the instability of the wellbore lies in mechanical instability. Before drilling, the formation rock is in a state of stress balance. However, once the wellbore is formed, the original stress balance is broken, and the original pressure of the rock formation on the wellbore is replaced by the injection pressure of the drilling fluid, and the stress around the formation is redistributed. At this time, if the stress applied to the rock around the wellbore exceeds the strength of the rock itself, the brittle formation will collapse, and the plastic formation will shrink, which will lead to the instability of the wellbore. In addition, during drilling, the drilling fluid filtrate will penetrate into the formation, causing the formation pore pressure to increase, disrupting the rock stress distribution, and at the same time inducing hydration, causing the rock strength to decrease, further aggravating the instability of the wellbore. It can be seen that the key to achieving wellbore stability is to effectively prevent water from entering the formation and cut off the transmission of wellbore pressure to the formation.

[0003] In dealing with the problem of wellbore instability and ensuring the performance of drilling fluid, chemical inhibition, reasonable density and sealing are the main measures taken. Sulfonated asphalt is a commonly used and efficient fluid loss reducer in the field of drilling engineering, and it plays an important role. It uses natural asphalt as raw material. After sulfonation modification, strong polar groups such as sulfonic acid groups are introduced into the molecular structure. It has good water solubility and can be quickly and evenly dispersed in the drilling fluid system to help stabilize the wellbore. However, it should be noted that in specific environments such as high-temperature oil wells, some surfactants are prone to decomposition or deterioration, which will damage the stability of the mixed system of sulfonated asphalt and surfactants, making it difficult for sulfonated asphalt to fully exert its effectiveness. Summary of the invention

[0004] In view of the above situation, the present invention aims to overcome the defects of the prior art. The present invention improves the performance of sulfonated asphalt by modifying SEBS, effectively solves the problems such as well wall instability faced during drilling, and significantly improves the performance of drilling fluid.

[0005] In order to achieve the above object, the following technical scheme is adopted: The present invention provides a method for preparing sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid, and the preparation method comprises the following steps:

[0006] S1. Dissolve SEBS in toluene, then add a nitrate reagent and a Lewis acid catalyst, perform a nitration reaction at 50-80°C, then pour the reactant into 0°C ice water to precipitate the nitration product, and obtain the nitrated SEBS by filtering, washing and drying;

[0007] S2, dissolving 5-(2-hydroxyethyl)uracil in acetone, adding anhydrous potassium carbonate, heating to reflux, then adding 4-bromo-1-butylamine, continuing the reflux reaction for 3-5h, then adding nitrated SEBS and reflux reaction for 1-3h, then filtering, adding deionized water for extraction, collecting the organic phase after separation, and removing the solvent under reduced pressure to obtain a SEBS modified intermediate;

[0008] S3, after mixing the SEBS modified intermediate with quaternary ammonium bromide, adding the mixture into a mixed solution of acetonitrile and water in a volume ratio of 2:1, heating to reflux, then pouring the reactant into 0°C ice water, filtering out the precipitate, washing with deionized water, and drying to obtain modified SEBS;

[0009] S4. Crush the construction asphalt and road asphalt, mix them and add them to kerosene, heat them to 100°C and keep them warm for 1-3 hours, then cool them to room temperature, first add the modified SEBS, then add fuming sulfuric acid, react for 2-5 hours, then add 25% sodium hydroxide solution to adjust the pH to 8-9, then heat to 110°C to evaporate the water, dry the obtained solid in an oven at 115°C, and crush them to obtain the high temperature and high pressure fluid loss reducer sulfonated asphalt.

[0010] Furthermore, in step S1, the mass ratio of SEBS, toluene, nitrate reagent and Lewis acid catalyst is 1:10-15:0.2-0.5:0.01-0.05.

[0011] Furthermore, in step S2, the mass ratio of 5-(2-hydroxyethyl)uracil, anhydrous potassium carbonate, 4-bromo-1-butylamine and nitrated SEBS is 1:1.2-2.5:2-5:2-5.

[0012] Furthermore, in step S3, the mass ratio of the SEBS modified intermediate, the brominated quaternary ammonium salt and the mixed solution is 1:0.2-0.5:20-30.

[0013] Furthermore, the nitrate reagent is one of ethyl nitrate, propyl nitrate, n-butyl nitrate and isobutyl nitrate.

[0014] Furthermore, the Lewis acid catalyst is one of aluminum trichloride, boron trifluoride, ferric trichloride and titanium tetrachloride.

[0015] Furthermore, the brominated quaternary ammonium salt is one or a combination of 6-bromohexyltrimethylammonium bromide and 5-bromopentyltrimethylammonium bromide.

[0016] Furthermore, in step S4, the mass ratio of building asphalt, road asphalt, kerosene, modified SEBS and oleum is 1:2.5-4:10-20:5-8:0.01-0.1.

[0017] Furthermore, the needle penetration of the construction asphalt is 5-351 / 10mm, and the needle penetration of the road asphalt is 40-651 / 10mm.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention modifies SEBS by introducing a comb-shaped side chain on its benzene ring, thereby changing the chemical properties and spatial morphology of SEBS, and making SEBS have a comb-shaped structure. The comb-shaped structure can form a strong interaction with sulfonated asphalt, so that the dispersion state of asphalt in the solution is optimized and asphalt agglomeration is avoided. The functional group introduced by 5-(2-hydroxyethyl)uracil changes the surface properties of the SEBS modified intermediate, making it have a better balance of lipophilicity and hydrophilicity, reducing the interaction force between asphalt particles, so that the efficiency and uniformity of asphalt when reacting with fuming sulfuric acid are improved. As a high-efficiency dispersant, it promotes the uniform dispersion of asphalt, so that sulfuric acid molecules can fully and evenly contact with it, greatly improving the rate and degree of sulfonation reaction, promoting the generation of sulfonated asphalt, and thus improving the overall quality of sulfonated asphalt;

[0020] (2) The surface activity of modified SEBS forms a network structure with sulfonated asphalt, further increasing the water solubility of asphalt, greatly facilitating the preparation of drilling fluid, reducing the surface tension of the liquid, and destroying the conditions for bubble formation. It can quickly eliminate bubbles at the initial stage, thus ensuring the stability and safety of the drilling fluid throughout the process;

[0021] (3) By introducing quaternary ammonium salt groups on SEBS, based on the principle of opposite attraction between the negative charges of quaternary ammonium salts and formation clay, sulfonated asphalt can effectively ensure the stability of the wellbore, and promote the transformation of the wellbore clay from hydrophilic to hydrophobic, thereby inhibiting the hydration and expansion of the formation clay, preventing the risk of wellbore collapse, and promoting the sulfonated asphalt to penetrate deep into the wellbore cracks under pressure. The temperature and pressure resistance and anti-filtration performance of the modified sulfonated asphalt are improved, and the molecular structure is stable under high temperature and high pressure environment, which can continuously play a role in reducing filtration and control the filtration loss of drilling fluid at a low level. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The results of the high temperature fluid loss reduction performance analysis of sulfonated asphalt, a high temperature and high pressure fluid loss reducer for drilling fluid according to the present invention;

[0023] Figure 2 The foamability analysis results of sulfonated asphalt, a high-temperature and high-pressure fluid loss reducer for drilling fluid according to the present invention;

[0024] Figure 3 The wall-forming property analysis result of sulfonated asphalt, a high-temperature and high-pressure fluid loss reducer for drilling fluid according to the present invention.

[0025] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0028] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0029] Example 1

[0030] Preparation method of sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid

[0031] The preparation method comprises the following steps:

[0032] S1. Dissolve SEBS in toluene, then add a nitrate reagent and a Lewis acid catalyst, perform a nitration reaction at 50°C, then pour the reactant into 0°C ice water to precipitate the nitration product, and obtain the nitrated SEBS by filtering, washing and drying;

[0033] S2, dissolving 5-(2-hydroxyethyl)uracil in acetone, adding anhydrous potassium carbonate, heating to reflux, then adding 4-bromo-1-butylamine, continuing the reflux reaction for 3-5h, then adding nitrated SEBS and refluxing for 1h, then filtering, adding deionized water for extraction, collecting the organic phase after separation, and removing the solvent under reduced pressure to obtain a SEBS modified intermediate;

[0034] S3, after mixing the SEBS modified intermediate with quaternary ammonium bromide, adding the mixture into a mixed solution of acetonitrile and water in a volume ratio of 2:1, heating to reflux, then pouring the reactant into 0°C ice water, filtering out the precipitate, washing with deionized water, and drying to obtain modified SEBS;

[0035] S4. Crush the construction asphalt and road asphalt, mix them and add them to kerosene, heat them to 100°C and keep them warm for 1 hour, then cool them to room temperature, first add the modified SEBS, then add fuming sulfuric acid, react for 2 hours, then add 25% sodium hydroxide solution to adjust the pH to 8-9, then heat to 110°C to evaporate the water, dry the obtained solid in an oven at 115°C, and crush them to obtain the high-temperature and high-pressure fluid loss reducer sulfonated asphalt.

[0036] In the step S1, the mass ratio of SEBS, toluene, nitrate reagent and Lewis acid catalyst is 1:10:0.2:0.01; in the step S2, the mass ratio of 5-(2-hydroxyethyl)uracil, anhydrous potassium carbonate, 4-bromo-1-butylamine and nitrated SEBS is 1:1.2:2:2; in the step S3, the mass ratio of SEBS modified intermediate, quaternary ammonium bromide and mixed solution is 1:0.2:20; the nitrate reagent is ethyl nitrate; the Lewis acid catalyst is aluminum trichloride; the quaternary ammonium bromide is 6-bromohexyltrimethylammonium bromide; in the step S4, the mass ratio of building asphalt, road asphalt, kerosene, modified SEBS and fuming sulfuric acid is 1:2.5:10:5:0.01; the needle penetration of the building asphalt is 5-351 / 10mm, and the needle penetration of the road asphalt is 40-651 / 10mm.

[0037] Example 2

[0038] Preparation method of sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid

[0039] The preparation method comprises the following steps:

[0040] S1. Dissolve SEBS in toluene, then add a nitrate reagent and a Lewis acid catalyst, perform a nitration reaction at 80°C, then pour the reactant into 0°C ice water to precipitate the nitration product, and obtain the nitrated SEBS by filtering, washing and drying;

[0041] S2, dissolving 5-(2-hydroxyethyl)uracil in acetone, adding anhydrous potassium carbonate, heating to reflux, then adding 4-bromo-1-butylamine, continuing the reflux reaction for 5 hours, then adding nitrated SEBS and reflux reaction for 3 hours, then filtering, adding deionized water for extraction, collecting the organic phase after separation, and removing the solvent under reduced pressure to obtain a SEBS modified intermediate;

[0042] S3, after mixing the SEBS modified intermediate with quaternary ammonium bromide, adding the mixture into a mixed solution of acetonitrile and water in a volume ratio of 2:1, heating to reflux, then pouring the reactant into 0°C ice water, filtering out the precipitate, washing with deionized water, and drying to obtain modified SEBS;

[0043] S4. Crush the construction asphalt and road asphalt, mix them and add them to kerosene, heat them to 100°C and keep them warm for 3 hours, then cool them to room temperature, first add the modified SEBS, then add fuming sulfuric acid, react for 5 hours, then add 25% sodium hydroxide solution to adjust the pH to 8-9, then heat to 110°C to evaporate the water, dry the obtained solid in an oven at 115°C, and crush it to obtain the high-temperature and high-pressure fluid loss reducer sulfonated asphalt.

[0044] In the step S1, the mass ratio of SEBS, toluene, nitrate reagent and Lewis acid catalyst is 1:15:0.5:0.05; in the step S2, the mass ratio of 5-(2-hydroxyethyl)uracil, anhydrous potassium carbonate, 4-bromo-1-butylamine and nitrated SEBS is 1:2.5:5:5; in the step S3, the mass ratio of SEBS modified intermediate, quaternary ammonium bromide and mixed solution is 1:0.5:30; the nitrate reagent is propyl nitrate; the Lewis acid catalyst is boron trifluoride; the quaternary ammonium bromide is 5-bromopentyltrimethylammonium bromide; in the step S4, the mass ratio of building asphalt, road asphalt, kerosene, modified SEBS and fuming sulfuric acid is 1:4:20:8:0.1; the needle penetration of the building asphalt is 5-351 / 10mm, and the needle penetration of the road asphalt is 40-651 / 10mm.

[0045] Example 3

[0046] Preparation method of sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid

[0047] The preparation method comprises the following steps:

[0048] S1. Dissolve SEBS in toluene, then add a nitrate reagent and a Lewis acid catalyst, perform a nitration reaction at 60°C, then pour the reactant into 0°C ice water to precipitate the nitration product, and obtain the nitrated SEBS by filtering, washing and drying;

[0049] S2, dissolving 5-(2-hydroxyethyl)uracil in acetone, adding anhydrous potassium carbonate, heating to reflux, then adding 4-bromo-1-butylamine, continuing the reflux reaction for 4 hours, then adding nitrated SEBS and refluxing for 2 hours, then filtering, adding deionized water for extraction, collecting the organic phase after separation, and removing the solvent under reduced pressure to obtain a SEBS modified intermediate;

[0050] S3, after mixing the SEBS modified intermediate with quaternary ammonium bromide, adding the mixture into a mixed solution of acetonitrile and water in a volume ratio of 2:1, heating to reflux, then pouring the reactant into 0°C ice water, filtering out the precipitate, washing with deionized water, and drying to obtain modified SEBS;

[0051] S4. Crush the construction asphalt and road asphalt, mix them and add them to kerosene, heat them to 100°C and keep them warm for 2 hours, then cool them to room temperature, first add the modified SEBS, then add fuming sulfuric acid, react for 2-5 hours, then add 25% sodium hydroxide solution to adjust the pH to 8-9, then heat to 110°C to evaporate the water, dry the obtained solid in an oven at 115°C, and crush it to obtain the high-temperature and high-pressure fluid loss reducer sulfonated asphalt.

[0052] The mass ratio of SEBS, toluene, nitrate reagent and Lewis acid catalyst in step S1 is 1:12:0.3:0.02; the mass ratio of 5-(2-hydroxyethyl)uracil, anhydrous potassium carbonate, 4-bromo-1-butylamine and nitrated SEBS in step S2 is 1:1.5:3:2.5; the mass ratio of SEBS modified intermediate, quaternary ammonium bromide and mixed solution in step S3 is 1:0.35:25; the nitrate reagent is nitrate. The invention relates to a method for preparing an aqueous solution of quaternary ammonium bromide, wherein the quaternary ammonium bromide is prepared by mixing 6-bromohexyltrimethylammonium bromide and 5-bromopentyltrimethylammonium bromide in a mass ratio of 2:1; the mass ratio of the building asphalt, road asphalt, kerosene, modified SEBS and fuming sulfuric acid in the step S4 is 1:3:15:6:0.05; the needle penetration of the building asphalt is 5-351 / 10mm, and the needle penetration of the road asphalt is 40-651 / 10mm.

[0053] Example 4

[0054] Preparation method of sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid

[0055] The nitrate reagent in this embodiment is isobutyl nitrate; the Lewis acid catalyst is ferric chloride, and the rest is the same as in Example 3.

[0056] Comparative Example 1

[0057] In this comparative example, an equal amount of unmodified SEBS was used instead of modified SEBS to prepare sulfonated asphalt, and the rest was the same as Example 4.

[0058] Comparative Example 2

[0059] In this comparative example, an equal amount of commonly used surfactant lignin sulfonate was used instead of modified SEBS to prepare sulfonated asphalt, and the rest was the same as Example 4.

[0060] Results Analysis

[0061] Test Example 1

[0062] Analysis of high temperature filtration loss reduction performance

[0063] 40 g of sodium bentonite was added to 1 L of distilled water, stirred evenly at high speed, and then allowed to stand for 24 h. Then, 5 g of sodium carbonate was added and stirred at high speed to obtain a base slurry. 20 g of the sulfonated asphalt prepared in each embodiment and comparative example was added to the base slurry. A 20% sodium hydroxide solution was added to adjust the pH to 10. The filtration loss of the sulfonated asphalt at 150 ° C and 3.45 MPa was tested according to the method in SY / T 5621-93. The sulfonated asphalt prepared in each embodiment and comparative example was aged for 8 h at a temperature of 200 ° C, and then the filtration loss after aging was tested. The results are shown in FIG. Figure 1 .

[0064] The test results show obvious differences. Under the simulated downhole high temperature and high pressure environment of 150°C and 3.45MPa, the filtration loss of sulfonated asphalt prepared in Examples 1-4 is significantly lower than that of Comparative Examples 1 and 2. This is because the present invention modifies SEBS. SEBS is first dissolved in toluene, and a nitrate reagent and a Lewis acid catalyst are added to catalyze the nitration reaction at 50-80°C, so that the SEBS benzene ring is introduced into a comb-like side chain to form a comb-shaped structure. This structure interacts strongly with the sulfonated asphalt molecules, optimizes the dispersion state of asphalt in the solution, and avoids agglomeration. In addition, the introduced 5-(2-hydroxyethyl) uracil changes the surface properties of the SEBS modified intermediate, balances the lipophilicity and hydrophilicity, reduces the interaction between asphalt particles, allows asphalt to be fully and evenly contacted with fuming sulfuric acid, increases the rate and degree of sulfonation reaction, and improves the overall quality of sulfonated asphalt, so that it can better block the drilling fluid filtrate from penetrating into the formation and effectively control the filtration loss.

[0065] When the temperature was raised to 200°C and the mixture was aged for 8 hours, the filter loss of Examples 1-4 increased, but the increase was very small. This is due to the good heat and pressure resistance of the modified sulfonated asphalt, the stable molecular structure, and the continuous effect of reducing filter loss. Comparative Example 1 uses unmodified SEBS, which cannot finely disperse the asphalt, the sulfonation effect is poor, the quality of the generated sulfonated asphalt is poor, and it is difficult to block the penetration of the filtrate. The filter loss increases significantly after aging. Comparative Example 2 uses lignin sulfonate instead of modified SEBS. It is difficult for it to cooperate with sulfonated asphalt to build a stable structure and cannot withstand the impact of high temperature and high pressure. The filter loss increases sharply after aging.

[0066] Test Example 2

[0067] Foaming performance analysis

[0068] Take 300 mL of the base slurry prepared in Example 1, add 6 g of the sulfonated asphalt prepared in each example and comparative example, stir at high speed for 20 min, cure at room temperature for 1 h, and then stir at high speed for 5 min. The foaming performance of the sulfonated asphalt is tested by the method in Q / SY TZ 0017-2000. The results are shown in Table 1. Figure 2 .

[0069] Figure 2 The results show that the foaming rates of Examples 1-4 are much lower than those of Comparative Examples 1 and 2. The reason is that the modified SEBS of the present invention has surface activity, which forms a network structure with sulfonated asphalt, improves the water solubility of asphalt, and makes the drilling fluid flow more smoothly. At the same time, the network structure reduces the surface tension of the liquid, destroys the conditions for bubble formation, and can quickly eliminate bubbles at the initial stage of bubble initiation, ensuring the stability and safety of the drilling fluid during recycling. Comparative Examples 1 and 2 lack this modified structure that inhibits the generation of bubbles. Under the same experimental operation, bubbles are easily generated, and the foaming phenomenon is serious, affecting the fluidity of the drilling fluid.

[0070] Test Example 3

[0071] Wall-building analysis

[0072] The mud cake was prepared by using a GGSD71 high temperature and high pressure dynamic dehydration instrument according to the proportion of Experimental Example 1, and the cross section of the mud cake was observed by a Quauta200 scanning electron microscope. Figure 3 .

[0073] The mud cakes of Comparative Examples 1 and 2 have loose surfaces, large pores, and cracks in the cross section, while the mud cakes of Example 4 have a smooth, dense surface and no cracks.

[0074] The mud cakes of Comparative Examples 1 and 2 have loose surfaces, large pores and disorderly distribution. These pores constitute channels for drilling fluid loss, seriously weakening the ability of the mud cake to block filtrate penetration. There are many cracks in the cross section, which destroy the integrity of the mud cake structure and reduce its stability. As a result, the mud cake is easily broken in actual applications and is difficult to provide reliable support and protection for the well wall.

[0075] The mud cake of Example 4 has excellent performance and a smooth surface, which reduces the friction resistance between the mud cake and the external environment, and at the same time reduces the probability of drilling fluid adhesion on its surface, which is conducive to maintaining its own structural stability. The mud cake of Example 4 has small pores and can effectively block the infiltration of drilling fluid filtrate, effectively ensuring the stability of the environment around the well wall, and there are no cracks in the cross section, indicating that the mud cake has strong integrity and continuity, and can continue to provide stable and lasting protection for the well wall in the complex and changeable high-pressure environment underground, effectively preventing the risk of well wall collapse.

[0076] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0077] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid, characterized in that: The following steps are involved: S1. Dissolve SEBS in toluene, then add a nitrate reagent and a Lewis acid catalyst, perform a nitration reaction at 50-80°C, then pour the reactant into 0°C ice water to precipitate the nitration product, and obtain the nitrated SEBS by filtering, washing and drying; S2, dissolving 5-(2-hydroxyethyl)uracil in acetone, adding anhydrous potassium carbonate, heating to reflux, then adding 4-bromo-1-butylamine, continuing the reflux reaction for 3-5h, then adding nitrated SEBS and reflux reaction for 1-3h, then filtering, adding deionized water for extraction, collecting the organic phase after separation, and removing the solvent under reduced pressure to obtain a SEBS modified intermediate; S3, after mixing the SEBS modified intermediate with quaternary ammonium bromide, adding the mixture into a mixed solution of acetonitrile and water in a volume ratio of 2:1, heating to reflux, then pouring the reactant into 0°C ice water, filtering out the precipitate, washing with deionized water, and drying to obtain modified SEBS; S4. Crush the construction asphalt and road asphalt, mix them and add them to kerosene, heat them to 100°C and keep them warm for 1-3 hours, then cool them to room temperature, first add the modified SEBS, then add fuming sulfuric acid, react for 2-5 hours, then add 25% sodium hydroxide solution to adjust the pH to 8-9, then heat to 110°C to evaporate the water, dry the obtained solid in an oven at 115°C, and crush them to obtain the high temperature and high pressure fluid loss reducer sulfonated asphalt.

2. The method for preparing the high-temperature and high-pressure fluid loss reducer sulfonated asphalt for drilling fluid according to claim 1, characterized in that: In the step S1, the mass ratio of SEBS, toluene, nitrate reagent and Lewis acid catalyst is 1:10-15:0.2-0.5:0.01-0.

05.

3. The method for preparing the high-temperature and high-pressure fluid loss reducer sulfonated asphalt for drilling fluid according to claim 2, characterized in that: In the step S2, the mass ratio of 5-(2-hydroxyethyl)uracil, anhydrous potassium carbonate, 4-bromo-1-butylamine and nitrated SEBS is 1:1.2-2.5:2-5:2-5.

4. The method for preparing the high-temperature and high-pressure fluid loss reducer sulfonated asphalt for drilling fluid according to claim 3, characterized in that: In the step S3, the mass ratio of the SEBS modified intermediate, the brominated quaternary ammonium salt and the mixed solution is 1:0.2-0.5:20-30.

5. The method for preparing the high-temperature and high-pressure fluid loss reducer sulfonated asphalt for drilling fluid according to claim 4, characterized in that: The nitrate reagent is one of ethyl nitrate, propyl nitrate, n-butyl nitrate and isobutyl nitrate.

6. The method for preparing sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid according to claim 5, characterized in that: The Lewis acid catalyst is one of aluminum trichloride, boron trifluoride, ferric trichloride and titanium tetrachloride.

7. The method for preparing sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid according to claim 6, characterized in that: The brominated quaternary ammonium salt is one or a combination of 6-bromohexyltrimethylammonium bromide and 5-bromopentyltrimethylammonium bromide.

8. The method for preparing sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid according to claim 7, characterized in that: In the step S4, the mass ratio of building asphalt, road asphalt, kerosene, modified SEBS and oleum is 1:2.5-4:10-20:5-8:0.01-0.

1.

9. The method for preparing sulfonated asphalt as a high-temperature and high-pressure fluid loss reducer for drilling fluid according to claim 7, characterized in that: The needle penetration of the construction asphalt is 5-351 / 10mm, and the needle penetration of the road asphalt is 40-651 / 10mm.

10. A high-temperature and high-pressure fluid loss reducer sulfonated asphalt for drilling fluid, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

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