High-temperature-resistant viscosity reducer for drilling fluid and preparation method of viscosity reducer
By preparing modified viscosity reducers such as seaweed polysaccharides and silica, the problem of increased viscosity of drilling fluid at high temperatures was solved, achieving high-temperature viscosity reduction effect of drilling fluid, which is suitable for water-based drilling fluids.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-03-27
AI Technical Summary
Existing drilling fluid viscosity reducers have poor viscosity reduction effects at high temperatures, which affects the progress of drilling projects. Furthermore, polymer-based viscosity reducers are expensive, while the effects of natural material-modified viscosity reducers are unstable.
Using raw materials such as seaweed polysaccharide, silica, cyclodextrin and ethylenediaminetetramethylenephosphonic acid, a high-temperature resistant viscosity reducer was prepared through sulfation, hydrothermal treatment and surface modification. It utilizes negative charge and electrostatic repulsion to prevent drilling fluid particles from agglomerating and form a protective film to isolate the particles.
It effectively reduces drilling fluid viscosity at high temperatures, maintains rheological properties, and improves drilling fluid fluidity, making it suitable for water-based drilling fluids.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of viscosity reducer technology, and in particular to a high-temperature resistant viscosity reducer for drilling fluids and its preparation method. Background Technology
[0002] Drilling fluid is the lifeblood of drilling, playing crucial roles in improving rheology, carrying cuttings, and stabilizing the wellbore during drilling operations. It is an indispensable part of oil and gas exploration and development, and is vital to the exploration process. In recent years, with the advancement of oilfield exploration and the continuous increase in drilling depth, the geological conditions encountered have become increasingly complex, with higher temperatures and pressures. High temperatures cause the clay particles in the drilling fluid to become finer and their content to increase, leading to poorer rheological properties and high-temperature thickening. This manifests in two forms: high-temperature viscosity increase and solidification. Viscosity increase leads to poor rheological properties, while solidification increases viscosity, severely impacting the progress of deep well drilling. Therefore, to maintain the rheological properties of drilling fluid, viscosity reducers need to be added to reduce viscosity and shear forces during drilling, thereby improving rheological properties. Thus, viscosity reducers have become an indispensable drilling fluid treatment agent. In recent years, polymer-based viscosity reducers and natural material-modified viscosity reducers have been the main types of viscosity reducers used. However, polymer-based viscosity reducers have complex manufacturing processes, low product yields, and high costs, which limits their application. Meanwhile, the viscosity-reducing effect of natural material-modified viscosity reducers is unstable, and their application in practice is limited.
[0003] Therefore, the present invention provides a high-temperature resistant viscosity reducer for drilling fluid and its preparation method, thereby improving the high-temperature resistance of the viscosity reducer and enhancing its viscosity-reducing effect on drilling fluid. Summary of the Invention
[0004] Therefore, the purpose of this invention is to provide a high-temperature resistant viscosity reducer for drilling fluids and its preparation method, thereby solving the problem that viscosity reducers have poor viscosity-reducing effects on drilling fluids at high temperatures.
[0005] The present invention solves the above-mentioned technical problems through the following technical means: A high-temperature resistant viscosity reducer for drilling fluids and its preparation method are disclosed. The raw materials for the viscosity reducer are as follows: seaweed polysaccharide, silica, concentrated sulfuric acid, cyclodextrin, ethylenediaminetetramethylenephosphonic acid, n-butanol, and ammonium sulfate.
[0006] Furthermore, the preparation method of the viscosity reducer is as follows: (1) After mixing concentrated sulfuric acid and n-butanol evenly, add ammonium sulfate and stir at 200-300 r / min for 5-10 min. Add seaweed polysaccharide and react at 50-60℃ for 3-4 h. Then adjust the solution to neutral with 1 mol / L sodium hydroxide solution and centrifuge at 3500-4000 r / min for 10-15 min. Dialyze with a dialysis bag with a molecular weight cutoff of 3500 Da and freeze dry to obtain sulfated seaweed polysaccharide. (2) Add sulfated seaweed polysaccharide to water, stir evenly, and treat at 110-130℃ for 20-30 min to obtain the treated sulfated seaweed polysaccharide solution; (3) Add sodium dodecyl sulfate to water, heat to 80-90℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add silicon dioxide to sodium dodecyl sulfate solution, let stand for 2-3 hours, filter and dry at 40-50℃ for 2-3 hours to obtain modified silicon dioxide; (4) Add cyclodextrin and ethylenediaminetetramethylenephosphonic acid to water and stir until uniform to obtain a mixed solution. Then mix the mixed solution, sulfated seaweed polysaccharide solution and modified silica until uniform to obtain a viscosity reducer.
[0007] Seaweed polysaccharides are modified by introducing negatively charged sulfate ions to obtain negatively charged sulfated seaweed polysaccharides. When sulfated seaweed polysaccharides come into contact with clay particles in drilling fluid, they adhere to the surface of the clay particles, forming a protective layer that prevents the clay particles from agglomerating. Simultaneously, the negative charge density on the surface of the clay particles is increased, enhancing the electrostatic repulsion between them and making it difficult for them to aggregate. This breaks down the network structure formed by the clay particles, releasing the free water bound between them, thereby reducing the viscosity of the drilling fluid. Ammonium sulfate can provide additional sulfate ions to react with the hydroxyl groups on the polysaccharide molecules in an esterification reaction, thereby increasing the degree of sulfation and neutralizing excess hydrogen ions to neutralize acidity, making the reaction milder and protecting the structure of the seaweed polysaccharides. However, seaweed polysaccharides themselves have high viscosity, and adding too much can increase the viscosity of the drilling fluid. Therefore, high-temperature treatment of sulfated seaweed polysaccharides breaks the chemical bonds between the sulfated seaweed polysaccharide molecules, reducing entanglement and aggregation between molecular chains, thereby lowering the viscosity of the sulfated seaweed polysaccharide solution. Thus, the viscosity of the treated sodium alginate solution is reduced, and its addition to the drilling fluid will not affect the viscosity of the drilling fluid. Silica is also added to the viscosity reducer, dispersed in the drilling fluid, and spaced between clay particles to prevent particle aggregation, thereby reducing the viscosity of the drilling fluid. However, untreated silica is highly hydrophobic and prone to self-aggregation, which may exacerbate the increase in drilling fluid viscosity. Therefore, sodium dodecyl sulfate is used to treat the silica. The sulfate groups of sodium dodecyl sulfate adsorb onto the silica surface, making it negatively charged. The electrostatic repulsion between silica particles prevents silica aggregation, promotes silica dispersion in the drilling fluid, and further reduces the viscosity of the drilling fluid. The viscosity reducer also includes ethylenediaminetetramethylenephosphonic acid (EDTA). The phosphate ions of EDTA can complex with metal ions on the surface of clay particles in the drilling fluid to form a protective film, preventing phase contact between clay particles and inhibiting particle aggregation, thereby reducing the viscosity of the drilling fluid. Furthermore, the cyclodextrin in the viscosity reducer can encapsulate particles in the drilling fluid, preventing particle aggregation and improving mud dispersibility, thus achieving a viscosity-reducing effect.
[0008] Furthermore, in step (1) of the viscosity reducer preparation method, the mass ratio of seaweed polysaccharide, concentrated sulfuric acid, n-butanol, and ammonium sulfate is (1-1.2):(15-20):(5-6):(0.2-0.3).
[0009] Furthermore, in step (3) of the viscosity reducer preparation method, the mass ratio of sodium dodecyl sulfate to silicon dioxide is (2-3):(5-6).
[0010] Furthermore, in step (4) of the viscosity reducer preparation method, the mass ratio of cyclodextrin, ethylenediaminetetramethylenephosphonic acid, and water is (1-1.5):(2-3):(50-60).
[0011] Furthermore, in step (4) of the viscosity reducer preparation method, the mass ratio of the mixed solution, the sulfated seaweed polysaccharide solution, and the modified silica is (10-12):(10-15):(2-3).
[0012] Furthermore, the method of using the viscosity reducer is as follows: add the viscosity reducer directly to the drilling fluid, and make the concentration of the viscosity reducer in the drilling fluid 0.3-0.5%.
[0013] Furthermore, the viscosity reducer is suitable for water-based drilling fluids. Beneficial effects
[0014] The viscosity reducer prepared in this invention, when added to drilling fluid, can effectively disperse particles in the drilling fluid and prevent particle aggregation, thereby reducing the viscosity of the drilling fluid. Furthermore, the viscosity reducer prepared in this invention has strong high-temperature resistance and can effectively act on the drilling fluid in high-temperature environments, maintaining the viscosity of the drilling fluid under long-term high-temperature conditions. Detailed Implementation
[0015] The present invention will be described in detail below with reference to specific embodiments: Example
[0016] Drilling fluid preparation: (1) Mix 15g of concentrated sulfuric acid and 5g of n-butanol evenly, add 0.2g of ammonium sulfate, stir at 200r / min for 5min, add 1g of seaweed polysaccharide, react at 50℃ for 3h, then adjust the solution to neutral with 1mol / L sodium hydroxide solution, centrifuge at 3500r / min for 10min, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, freeze dry to obtain sulfated seaweed polysaccharide; (2) After mixing sulfated seaweed polysaccharide with water at a mass ratio of 1:50 and stirring evenly, the mixture was treated at 110℃ for 20 min to obtain the treated sulfated seaweed polysaccharide solution. (3) Add 2g of sodium dodecyl sulfate to 20g of water, heat to 80℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add 5g of silicon dioxide with a particle size of 20nm to sodium dodecyl sulfate solution, let stand for 2h, filter and dry at 40℃ for 2h to obtain modified silicon dioxide. (4) Add 1g of cyclodextrin and 2g of ethylenediaminetetramethylenephosphonic acid to 50g of water and stir until a mixed solution is obtained. Then mix the mixed solution, sulfated seaweed polysaccharide solution and modified silica in a mass ratio of 10:10:2 to obtain a viscosity reducer. Example
[0017] Drilling fluid preparation: (1) After mixing 18g of concentrated sulfuric acid and 5.5g of n-butanol evenly, add 0.25g of ammonium sulfate and stir at 250r / min for 7min. Add 1.1g of seaweed polysaccharide and react at 55℃ for 3.5h. Then adjust the solution to neutral with 1mol / L sodium hydroxide solution. Centrifuge at 3800r / min for 12min, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, freeze dry, and obtain sulfated seaweed polysaccharide. (2) After mixing sulfated seaweed polysaccharide with water at a mass ratio of 1:50 and stirring evenly, the mixture was treated at 120℃ for 25 min to obtain the treated sulfated seaweed polysaccharide solution. (3) Add 2.5g sodium dodecyl sulfate to 25g water, heat to 85℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add 5.5g silicon dioxide with a particle size of 30nm to sodium dodecyl sulfate solution, let stand for 2.5h, filter and dry at 45℃ for 2.5h to obtain modified silicon dioxide; (4) Add 1.25g cyclodextrin and 2.5g ethylenediaminetetramethylenephosphonic acid to 55g water and stir until uniform to obtain a mixed solution. Then mix the mixed solution, sulfated seaweed polysaccharide solution and modified silica in a mass ratio of 11:12:2.5 to obtain a viscosity reducer. Example
[0018] Drilling fluid preparation: (1) After mixing 20g of concentrated sulfuric acid and 6g of n-butanol evenly, add 0.3g of ammonium sulfate, stir at 300r / min for 10min, add 1.2g of seaweed polysaccharide, react at 60℃ for 4h, then adjust the solution to neutral with 1mol / L sodium hydroxide solution, centrifuge at 4000r / min for 15min, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, freeze dry to obtain sulfated seaweed polysaccharide; (2) After mixing sulfated seaweed polysaccharide with water at a mass ratio of 1:50 and stirring evenly, the mixture was treated at 130℃ for 30 min to obtain the treated sulfated seaweed polysaccharide solution. (3) Add 3g sodium dodecyl sulfate to 30g water, heat to 90℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add 6g silicon dioxide with a particle size of 50nm to sodium dodecyl sulfate solution, let stand for 3h, filter and dry at 50℃ for 3h to obtain modified silicon dioxide. (4) Add 1.5g cyclodextrin and 3g ethylenediaminetetramethylenephosphonic acid to 60g water and stir until uniform to obtain a mixed solution. Then mix the mixed solution, sulfated seaweed polysaccharide solution and modified silica in a mass ratio of 12:15:3 to obtain a viscosity reducer.
[0019] Comparative Example 1: This comparative example is compared with Example 1, the only difference being the preparation of the viscosity reducer; specifically, no seaweed polysaccharide is added. The specific method is as follows: (1) Add 2g of sodium dodecyl sulfate to 20g of water, heat to 80℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add 5g of silicon dioxide with a particle size of 20nm to sodium dodecyl sulfate solution, let stand for 2h, filter and dry at 40℃ for 2h to obtain modified silicon dioxide. (2) Add 1g of cyclodextrin and 2g of ethylenediaminetetramethylenephosphonic acid to 50g of water and stir until a mixed solution is obtained. Then mix the mixed solution and modified silica in a mass ratio of 10:2 to obtain a viscosity reducer.
[0020] Comparative Example 2: This comparative example is compared with Example 1, the only difference being the preparation of the viscosity reducer. Specifically, the seaweed polysaccharide is not modified by sulfation. The specific method is as follows: (1) Mix seaweed polysaccharide and water at a mass ratio of 1:50, stir evenly, and then treat at 110℃ for 20 min to obtain seaweed polysaccharide solution; (2) Add 2g of sodium dodecyl sulfate to 20g of water, heat to 80℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add 5g of silicon dioxide with a particle size of 20nm to sodium dodecyl sulfate solution, let stand for 2h, filter and dry at 40℃ for 2h to obtain modified silicon dioxide. (3) Add 1g of cyclodextrin and 2g of ethylenediaminetetramethylenephosphonic acid to 50g of water and stir until a mixed solution is obtained. Then mix the mixed solution, seaweed polysaccharide solution and modified silica in a mass ratio of 10:10:2 to obtain a viscosity reducer.
[0021] Comparative Example 3: This comparative example is compared with Example 1, the only difference being the preparation of the viscosity reducer. Specifically, no modification of silica is performed, i.e., sodium dodecyl sulfate is not added. The specific method is as follows: (1) Mix 15g of concentrated sulfuric acid and 5g of n-butanol evenly, add 0.2g of ammonium sulfate, stir at 200r / min for 5min, add 1g of seaweed polysaccharide, react at 50℃ for 3h, then adjust the solution to neutral with 1mol / L sodium hydroxide solution, centrifuge at 3500r / min for 10min, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, freeze dry to obtain sulfated seaweed polysaccharide; (2) After mixing sulfated seaweed polysaccharide with water at a mass ratio of 1:50 and stirring evenly, the mixture was treated at 110℃ for 20 min to obtain the treated sulfated seaweed polysaccharide solution. (4) Add 1g of cyclodextrin and 2g of ethylenediaminetetramethylenephosphonic acid to 50g of water and stir until a mixed solution is obtained. Then mix the mixed solution, sulfated seaweed polysaccharide solution and silica in a mass ratio of 10:10:2 to obtain a viscosity reducer.
[0022] Comparative Example 4: This comparative example is compared with Example 1, the only difference being the preparation of the viscosity reducer; specifically, silica is not added. The specific method is as follows: (1) Mix 15g of concentrated sulfuric acid and 5g of n-butanol evenly, add 0.2g of ammonium sulfate, stir at 200r / min for 5min, add 1g of seaweed polysaccharide, react at 50℃ for 3h, then adjust the solution to neutral with 1mol / L sodium hydroxide solution, centrifuge at 3500r / min for 10min, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, freeze dry to obtain sulfated seaweed polysaccharide; (2) After mixing sulfated seaweed polysaccharide with water at a mass ratio of 1:50 and stirring evenly, the mixture was treated at 110℃ for 20 min to obtain the treated sulfated seaweed polysaccharide solution. (3) Add 1g of cyclodextrin and 2g of ethylenediaminetetramethylenephosphonic acid to 50g of water and stir until a mixed solution is obtained. Then mix the mixed solution and the sulfated seaweed polysaccharide solution in a mass ratio of 1:1 to obtain a viscosity reducer.
[0023] Comparative Example 5: This comparative example is compared with Example 1, the only difference being the preparation of the viscosity reducer; specifically, ethylenediaminetetramethylenephosphonic acid is not added. The specific method is as follows: (1) Mix 15g of concentrated sulfuric acid and 5g of n-butanol evenly, add 0.2g of ammonium sulfate, stir at 200r / min for 5min, add 1g of seaweed polysaccharide, react at 50℃ for 3h, then adjust the solution to neutral with 1mol / L sodium hydroxide solution, centrifuge at 3500r / min for 10min, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, freeze dry to obtain sulfated seaweed polysaccharide; (2) After mixing sulfated seaweed polysaccharide with water at a mass ratio of 1:50 and stirring evenly, the mixture was treated at 110℃ for 20 min to obtain the treated sulfated seaweed polysaccharide solution. (3) Add 2g of sodium dodecyl sulfate to 20g of water, heat to 80℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add 5g of silicon dioxide with a particle size of 20nm to sodium dodecyl sulfate solution, let stand for 2h, filter and dry at 40℃ for 2h to obtain modified silicon dioxide. (4) Add 1g of cyclodextrin to 50g of water and stir until homogeneous to obtain a cyclodextrin solution. Then mix the cyclodextrin solution, sulfated seaweed polysaccharide solution and modified silica in a mass ratio of 10:10:2 to obtain a viscosity reducer.
[0024] Comparative Example 6: This comparative example is compared with Example 1, the only difference being the preparation of the viscosity reducer. Specifically, the sulfated seaweed polysaccharide is not subjected to hydrothermal treatment. The specific method is as follows: (1) Mix 15g of concentrated sulfuric acid and 5g of n-butanol evenly, add 0.2g of ammonium sulfate, stir at 200r / min for 5min, add 1g of seaweed polysaccharide, react at 50℃ for 3h, then adjust the solution to neutral with 1mol / L sodium hydroxide solution, centrifuge at 3500r / min for 10min, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, freeze dry to obtain sulfated seaweed polysaccharide; (2) The sulfated seaweed polysaccharide and water were mixed evenly at a mass ratio of 1:50 to obtain a sulfated seaweed polysaccharide solution; (3) Add 2g of sodium dodecyl sulfate to 20g of water, heat to 80℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add 5g of silicon dioxide with a particle size of 20nm to sodium dodecyl sulfate solution, let stand for 2h, filter and dry at 40℃ for 2h to obtain modified silicon dioxide. (4) Add 1g of cyclodextrin and 2g of ethylenediaminetetramethylenephosphonic acid to 50g of water and stir until a mixed solution is obtained. Then mix the mixed solution, sulfated seaweed polysaccharide solution and modified silica in a mass ratio of 10:10:2 to obtain a viscosity reducer.
[0025] experiment: Preparation of drilling fluid-based slurry: Add 2.5g of anhydrous sodium carbonate and 50g of bentonite to 500mL of water, stir at high speed for 20min, and let it cure at room temperature for 24h to obtain drilling fluid-based slurry.
[0026] Selection of viscosity reducer: Experimental group 1 used the viscosity reducer prepared in Example 1, control groups 1-6 used the viscosity reducers prepared in Comparative Examples 1-6, and the blank group did not add any viscosity reducer. The performance of the prepared drilling fluid was determined according to GB / T29170-2012 "Laboratory Testing of Drilling Fluids for Petroleum and Natural Gas Industry". Apparent viscosity (AV) = 1 / 2 × Φ600; Plastic viscosity (PV) = Φ600 - Φ300; Dynamic shear force (YP) = 0.4788 × (Φ300 - PV).
[0027] Wherein, Φ600 is the reading at 600 revolutions and Φ300 is the reading at 300 revolutions.
[0028] Viscosity reduction rate at room temperature: A viscosity reducer was added to the drilling fluid base fluid at a concentration of 0.3% of the drilling fluid. After stirring for 5 minutes, the reading was immediately measured using a six-speed rotational viscometer and the viscosity reduction rate was calculated. The results are shown in Table 1.
[0029] Viscosity reduction rate at 260℃: A viscosity reducer was added to the drilling fluid base fluid at a concentration of 0.3% of the drilling fluid. After rolling aging at 260℃ for 16 hours, the fluid was cooled, opened, and stirred for 10 minutes. The readings were immediately measured using a six-speed rotational viscometer, and the viscosity reduction rate was calculated. The results are shown in Table 1.
[0030] Viscosity reduction rate (%) = (Φ100)0 - (Φ100)1 / (Φ100)0 × 100%.
[0031] Wherein, (Φ100)0 is the reading of the drilling fluid base slurry without viscosity reducer at a rotation speed of 100 rpm; (Φ100)1 is the reading of the base slurry with viscosity reducer added at a rotation speed of 100 rpm.
[0032] Table 1
[0033] Analysis of Table 1 yields the following results: 1. Compared to experimental group 1, control group 1, without the addition of seaweed polysaccharides, showed a poorer viscosity-reducing effect on the drilling fluid. This is because seaweed polysaccharides can adsorb onto the surface of particles in the drilling fluid to form a protective layer, thus preventing particle aggregation. Therefore, control group 1, without seaweed polysaccharides, had a lower viscosity-reducing rate. Compared to experimental group 1, control group 2, without sulfation modification of seaweed polysaccharides, also showed a poorer viscosity-reducing effect on the drilling fluid. This is because sulfated seaweed polysaccharides carry a negative charge, which can cause negative charge repulsion between particles in the drilling fluid, thereby inhibiting particle aggregation. Therefore, control group 2 had a lower viscosity-reducing rate. Control group 6 did not undergo hydrothermal treatment of sulfated seaweed polysaccharides. Seaweed polysaccharides themselves have a certain degree of viscosity; adding them to the drilling fluid increases the viscosity, resulting in a poor viscosity-reducing effect at room temperature. At high temperatures, seaweed polysaccharides also undergo a certain degree of molecular chain breakage, improving the viscosity-reducing effect. Therefore, directly adding seaweed polysaccharides without further processing will actually increase viscosity to some extent and reduce the viscosity-reducing effect.
[0034] 2. Compared to experimental group 1, control group 3 did not modify silica (i.e., sodium dodecyl sulfate was not added). Silica is prone to agglomeration, resulting in poor dispersibility in the drilling fluid and a weaker isolating effect, leading to increased drilling fluid viscosity. Compared to experimental group 1, control group 4 did not add silica. Particles in the drilling fluid tended to agglomerate, resulting in a poor viscosity-reducing effect of the viscosity reducer and a lower viscosity reduction rate.
[0035] 3. Compared with experimental group 1, control group 5 did not add ethylenediaminetetramethylenephosphonic acid, and the viscosity reduction rate of the viscosity reducer was lower. This is because ethylenediaminetetramethylenephosphonic acid can form a protective film on the surface of clay particles, thereby preventing phase contact between clay particles and inhibiting the agglomeration of clay particles. However, control group 5 did not add ethylenediaminetetramethylenephosphonic acid, and the clay particles were more likely to agglomerate, resulting in an increase in viscosity.
[0036] 4. Compared with experimental group 1, the control group did not add viscosity reducer, while the drilling fluid with the viscosity reducer prepared in experimental group 1 showed a decrease in apparent viscosity and shear force. This indicates that the viscosity reducer can effectively reduce the viscosity of the drilling fluid and maintain its rheological properties.
[0037] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.
Claims
1. A high-temperature resistant viscosity reducer for drilling fluids, characterized in that, The raw materials for the viscosity reducer are as follows: seaweed polysaccharide, silicon dioxide, concentrated sulfuric acid, cyclodextrin, ethylenediaminetetramethylenephosphonic acid, n-butanol, and ammonium sulfate.
2. The method for preparing a high-temperature resistant drilling fluid viscosity reducer according to claim 1, characterized in that, The viscosity reducer is prepared as follows: (1) After mixing concentrated sulfuric acid and n-butanol evenly, add ammonium sulfate and stir evenly at a speed of 200-300 r / min. Add seaweed polysaccharide and react at 50-60℃ for 3-4 h. Then adjust the solution to neutral with 1 mol / L sodium hydroxide solution and centrifuge at 3500-4000 r / min for 10-15 min to obtain sulfated seaweed polysaccharide. (2) Add sulfated seaweed polysaccharide to water, stir evenly, and treat at 110-130℃ for 20-30 min to obtain the treated sulfated seaweed polysaccharide solution; (3) Add sodium dodecyl sulfate to water, heat to 80-90℃, stir until completely dissolved to obtain sodium dodecyl sulfate solution, then add silicon dioxide to sodium dodecyl sulfate solution, let stand for 2-3 hours, filter and dry at 40-50℃ for 2-3 hours to obtain modified silicon dioxide; (4) Add cyclodextrin and ethylenediaminetetramethylenephosphonic acid to water and stir until uniform to obtain a mixed solution. Then mix the mixed solution, sulfated seaweed polysaccharide solution and modified silica until uniform to obtain a viscosity reducer.
3. The method for preparing a high-temperature resistant drilling fluid viscosity reducer according to claim 2, characterized in that, In step (1) of the method for preparing the viscosity reducer, the mass ratio of seaweed polysaccharide, concentrated sulfuric acid, n-butanol, and ammonium sulfate is (1-1.2):(15-20):(5-6):(0.2-0.3).
4. The method for preparing a high-temperature resistant drilling fluid viscosity reducer according to claim 3, characterized in that, In step (3) of the viscosity reducer preparation method, the mass ratio of sodium dodecyl sulfate to silicon dioxide is (2-3):(5-6).
5. The high-temperature resistant drilling fluid viscosity reducer and its preparation method according to claim 4, characterized in that, In step (4) of the viscosity reducer preparation method, the mass ratio of cyclodextrin, ethylenediaminetetramethylenephosphonic acid, and water is (1-1.5):(2-3):(50-60).
6. The method for preparing a high-temperature resistant drilling fluid viscosity reducer according to claim 5, characterized in that, In step (4) of the viscosity reducer preparation method, the mass ratio of the mixed solution, the sulfated seaweed polysaccharide solution, and the modified silica is (10-12):(10-15):(2-3).
7. The method for preparing a high-temperature resistant drilling fluid viscosity reducer according to claim 6, characterized in that, The method of using the viscosity reducer is as follows: add the viscosity reducer directly to the drilling fluid, and make the concentration of the viscosity reducer in the drilling fluid 0.3-0.5%.
8. A high-temperature resistant viscosity reducer for drilling fluid according to any one of claims 1-7, characterized in that, The viscosity reducer is suitable for water-based drilling fluids.