Shale gas water-based drilling fluid formula and preparation method

Abstract

The invention relates to the technical field of drilling fluid, in particular to a shale gas water-based drilling fluid formula and a preparation method. The shale gas water-based drilling fluid is prepared from the following raw materials: bentonite slurry, a fiber material, starch, white asphalt, a stabilizer, a lubricant, calcium carbonate, barite and water. In the preparation of the shale gas water-based drilling fluid, the raw material of the fiber material comprises ketoprofen, ketoprofen is taken as an organic acid, can be subjected to solvation after being mixed with methanol and is used for modifying the soybean protein isolate, methanol is taken as a solvent to help dispersion and reaction, and by utilizing the hydratability and viscidity of the soybean protein isolate, the drilling fluid can be used for preparing the shale gas water-based drilling fluid. The viscosity of the drilling fluid can be increased, the formation of a filter cake is assisted through crosslinking of protein chains, and the high length-diameter ratio and strength of the multi-walled carbon nanotubes are utilized, so that a network structure can be formed in the drilling fluid, the viscosity can be increased, meanwhile, pores of the filter cake are filled, the permeability is reduced, the filter loss is reduced, and the use performance of the drilling fluid is improved.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, specifically to a shale gas water-based drilling fluid formulation and preparation method. Background Technology

[0002] Drilling fluid is a key functional fluid in drilling operations. It is mainly divided into oil-based drilling fluid and water-based drilling fluid. Compared with oil-based drilling fluid, the core advantages of water-based drilling fluid are concentrated in three dimensions: environmental protection, cost-effectiveness, and operational safety. Its core functions are to cool and lubricate the drill bit and drill string, reduce wear, carry cuttings to the surface, clean the wellbore, balance formation pressure, prevent well collapse and blowout, and form a filter cake on the well wall to protect the stability of the well wall.

[0003] In existing technologies, shale gas water-based drilling fluids, after prolonged flow dilution, experience a decrease in viscosity and an increase in filtration loss, thus affecting their efficiency. Therefore, this invention provides a shale gas water-based drilling fluid formulation and preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a shale gas water-based drilling fluid formulation and preparation method. The shale gas water-based drilling fluid prepared by this invention not only has good filtration loss performance but also excellent viscosity performance, effectively improving the performance of the shale gas water-based drilling fluid.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a shale gas water-based drilling fluid formulation, comprising the following raw materials: bentonite slurry, fiber material, starch, white asphalt, stabilizer, lubricant, calcium carbonate, barite, and water, wherein the mass parts of each raw material are: 100 parts water, 2-4 parts bentonite slurry, 3-5 parts fiber material, 2-4 parts starch, 1-2 parts white asphalt, 0.6-1 part stabilizer, 1-2 parts lubricant, 2-4 parts calcium carbonate, and 4-6 parts barite;

[0007] The fiber material is prepared by the following method:

[0008] S1: Preparation of additives, the raw materials of which include ketoprofen, methanol, soy protein isolate, multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin.

[0009] S2: Preparation of the mixture, the raw materials of which include graphene, sodium hydroxide solution, lignite resin, and hydrophobic associative polymer, and the mass of the mixture is 20-30% of the mass of the additives;

[0010] S3: Mixing process, the additives and the mixture are mixed to obtain the fiber material.

[0011] Further, the method for preparing the additive is as follows: Ketoprofen and methanol are mixed, and the resulting product is treated in an ultrasonic oscillator for 20-30 minutes. The resulting product is then added to a mixer, where soy protein isolate is added. The mixer is set to 100-200 rpm and stirred for 10-20 minutes. The resulting product is then added to a centrifuge and centrifuged at 8000-10000 rpm for 6-10 minutes. The supernatant is discarded from the resulting product, yielding a solid. The solid is then placed in an oven. The material is dried in an oven at 60–80°C for 4–6 hours to obtain a coarse material. The coarse material is then added to a mixer, where multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin are added. The mixer is set to 300–500 rpm and stirred for 40–60 minutes. The resulting product is then sent to a vacuum degassing chamber and treated at -0.09–-0.1 MPa for 20–30 minutes to obtain an additive. The polyaniline is pretreated before the additive is prepared.

[0012] Furthermore, the mass ratio of ketoprofen to methanol is 1:(4-6), the mass of soy protein isolate is 40-60% of the mass of ketoprofen, the mass of multi-walled carbon nanotubes is 30-50% of the mass of the coarse material, and the mass ratio of multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin is 1:(0.2-0.4):(0.08-0.1):(0.1-0.2):(0.1-0.2):(0.2-0.3).

[0013] Further, the pretreatment method for polyaniline is as follows: 2-acrylamido-2-methylpropanesulfonic acid and graphene oxide dispersion are stirred in an ice-water bath for 20-30 minutes. The resulting product is added to a mixer, where polyaniline and ammonium persulfate are added. The mixer is set to 200-400 rpm and stirred for 20-30 minutes. Then, acetone is added to the mixer, and the mixer is set to 200-400 rpm and stirred for 10-20 minutes. The resulting product is added to a centrifuge, which is set to 8000-10000 rpm and centrifuged for 6-10 minutes. The supernatant is discarded from the resulting product to obtain a precipitate. The precipitate is rinsed with deionized water and then placed in an oven at 40-60°C for 6-8 hours to complete the pretreatment of polyaniline.

[0014] Furthermore, the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to graphene oxide dispersion is 1:(4-6), the mass of polyaniline is 20-40% of the mass of 2-acrylamido-2-methylpropanesulfonic acid, the mass of ammonium persulfate is 10-20% of the mass of polyaniline, and the mass of acetone is 40-60% of the mass of polyaniline.

[0015] Further, the method for preparing the mixture is as follows: graphene and sodium hydroxide solution are added to a reaction vessel, the reaction vessel is set to stir at 100-200 rpm for 20-30 min, lignite resin and hydrophobic associating polymer are added to the reaction vessel, the reaction vessel is set to a temperature of 80-90℃, the stirring speed is 200-300 rpm, the mixture is stirred at a constant temperature for 40-60 min, and then allowed to stand for 4-6 h to obtain the mixture.

[0016] Furthermore, the mass ratio of graphene to sodium hydroxide solution is 1:(6-8), the mass concentration of sodium hydroxide solution is 5-10%, the mass of lignite resin is 1.5-2 times the mass of graphene, and the mass of hydrophobic associative polymer is 6-10% of the mass of lignite resin.

[0017] Furthermore, the stabilizer is potassium chloride.

[0018] Furthermore, the lubricant is molybdenum disulfide.

[0019] Secondly, the present invention also provides a method for preparing shale gas water-based drilling fluid, comprising the following steps: weighing bentonite slurry, fiber material, starch, white asphalt, stabilizer, lubricant, calcium carbonate, barite, and water as needed and adding them to a mixer, setting the mixer to 400-600 rpm and stirring for 30-50 minutes to obtain shale gas water-based drilling fluid.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. In the preparation of shale gas water-based drilling fluid in this invention, the addition of fiber material, in which ketoprofen, as an organic acid, can undergo solvation after being mixed with methanol, is used to modify soy protein isolate. Methanol, as a solvent, helps with dispersion and reaction. Utilizing the hydration and viscosity of soy protein isolate, the viscosity of the drilling fluid can be increased, and the cross-linking of protein chains helps to form a filter cake. Utilizing the high aspect ratio and strength of multi-walled carbon nanotubes, a network structure can be formed in the drilling fluid, increasing viscosity, while filling the pores of the filter cake, reducing permeability, reducing filtration loss, and improving the performance of the drilling fluid.

[0022] 2. In this invention, after pretreatment, 2-acrylamide-2-methylpropanesulfonic acid is introduced into the polyaniline to introduce sulfonic acid groups, thereby improving the water solubility and thermal stability of the polyaniline. Graphene oxide can provide hydrophilicity and dispersibility, enhance the mechanical strength and dispersibility of the polyaniline, so that it can form a stable filter cake in the drilling fluid system, reduce filtration loss, and increase the viscosity performance of the drilling fluid.

[0023] 3. In this invention, the addition of graphene to the mixture enables the formation of a dense structure in the drilling fluid by utilizing its high specific surface area, further reducing filtration loss. Lignite resin and hydrophobic associating polymers form a three-dimensional network in water through the association of hydrophobic groups, increasing the viscosity of the drilling fluid and improving the shear dilution of the drilling fluid. At the same time, the water-based drilling fluid proposed in this application uses the addition of natural recycled materials (soy protein isolate), which has the advantages of low cost and environmental protection, and can meet the drilling needs and applications. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0026] Example 1:

[0027] Raw material preparation: 100 parts water, 2 parts bentonite slurry, 3 parts fiber material, 2 parts starch, 1 part white asphalt, 0.6 parts stabilizer, 1 part lubricant, 2 parts calcium carbonate, 4 parts barite;

[0028] Potassium chloride was selected as the stabilizer, and molybdenum disulfide was selected as the lubricant.

[0029] Fiber material preparation:

[0030] S1: Preparation of additives, the raw materials of which include ketoprofen, methanol, soy protein isolate, multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin.

[0031] The method for preparing the additives is as follows: Ketoprofen and methanol are mixed, and the resulting product is treated in an ultrasonic oscillator for 20 minutes. The resulting product is then added to a mixer, where soy protein isolate is added. The mixer is set to 100 rpm and stirred for 10 minutes. The resulting product is then added to a centrifuge and centrifuged at 8000 rpm for 6 minutes. The supernatant is discarded from the resulting product, and the solid is obtained. The solid is then placed in an oven and dried at 60°C for 4 hours to obtain a coarse material. The coarse material is then added to a mixer, where multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, and carbon black are added. Epoxy resin was mixed at 300 rpm for 40 minutes using a mixer. The resulting product was then placed in a vacuum degassing chamber and treated at -0.09 MPa for 20 minutes to obtain the additive. Polyaniline was pretreated before the additive was prepared. The mass ratio of ketoprofen to methanol was 1:4, the mass of soy protein isolate was 40% of the mass of ketoprofen, and the mass of multi-walled carbon nanotubes was 30% of the mass of the coarse material. The mass ratio of multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin was 1:0.2:0.08:0.1:0.1:0.2.

[0032] The pretreatment method for polyaniline is as follows: A dispersion of 2-acrylamido-2-methylpropanesulfonic acid and graphene oxide is stirred in an ice-water bath for 20 minutes. The resulting product is added to a mixer, where polyaniline and ammonium persulfate are added. The mixer is set to 200 rpm and stirred for 20 minutes. Then, acetone is added to the mixer, and the mixer is set to 200 rpm and stirred for 10 minutes. The resulting product is then added to a centrifuge and centrifuged at 8000 rpm for 6 minutes. The supernatant was discarded from the obtained product, and the precipitate was obtained. The precipitate was washed with deionized water and then sent to an oven to dry at 40°C for 6 hours to complete the pretreatment of polyaniline. The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to graphene oxide dispersion was 1:4. The mass of polyaniline was 20% of the mass of 2-acrylamido-2-methylpropanesulfonic acid, the mass of ammonium persulfate was 10% of the mass of polyaniline, and the mass of acetone was 40% of the mass of polyaniline.

[0033] S2: Preparation of the mixture, the raw materials of which include graphene, sodium hydroxide solution, lignite resin, and hydrophobic associative polymer, and the mass of the mixture is 30% of the mass of the additives;

[0034] The method for preparing the mixture is as follows: graphene and sodium hydroxide solution are added to a reaction vessel, and the reaction vessel is stirred at 200 rpm for 30 min. Then, lignite resin and hydrophobic associating polymer are added to the reaction vessel. The reaction vessel is set to a temperature of 90℃, the stirring speed is 200-300 rpm, and the mixture is stirred at a constant temperature for 60 min. After standing for 6 h, the mixture is obtained. The mass ratio of graphene to sodium hydroxide solution is 1:6, the mass concentration of sodium hydroxide solution is 5%, the mass of lignite resin is 1.5 times the mass of graphene, and the mass of hydrophobic associating polymer is 6% of the mass of lignite resin.

[0035] S3: Mixing process, the additives and the mixture are mixed to obtain the fiber material;

[0036] Preparation of finished product: Weigh out bentonite slurry, fiber material, starch, white asphalt, stabilizer, lubricant, calcium carbonate, barite and water as needed and add them to the mixer. Set the mixer to 400 rpm and stir for 30 minutes to obtain shale gas water-based drilling fluid.

[0037] Example 2:

[0038] Raw material preparation: 100 parts water, 3 parts bentonite slurry, 4 parts fiber material, 3 parts starch, 1.5 parts white asphalt, 0.8 parts stabilizer, 1.5 parts lubricant, 3 parts calcium carbonate, 5 parts barite;

[0039] Potassium chloride was selected as the stabilizer, and molybdenum disulfide was selected as the lubricant.

[0040] Fiber material preparation:

[0041] S1: Preparation of additives, the raw materials of which include ketoprofen, methanol, soy protein isolate, multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin.

[0042] The method for preparing the additives is as follows: Ketoprofen and methanol are mixed, and the resulting product is treated in an ultrasonic oscillator for 25 minutes. The resulting product is then added to a mixer, where soy protein isolate is added. The mixer is set to 150 rpm and stirred for 15 minutes. The resulting product is then added to a centrifuge and centrifuged at 9000 rpm for 8 minutes. The supernatant is discarded from the resulting product, and the solid is obtained. The solid is then placed in an oven and dried at 70℃ for 5 hours to obtain coarse material. The coarse material is added to a mixer, where multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and cyclic compounds are added. The epoxy resin was mixed at 400 rpm for 50 min using a mixer. The resulting product was then placed in a vacuum degassing chamber and treated at -0.095 MPa for 25 min to obtain the additive. Polyaniline was pretreated before the additive was prepared. The mass ratio of ketoprofen to methanol was 1:5, the mass of soy protein isolate was 50% of the mass of ketoprofen, and the mass of multi-walled carbon nanotubes was 40% of the mass of the coarse material. The mass ratio of multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin was 1:0.3:0.09:0.15:0.15:0.25.

[0043] The pretreatment method for polyaniline is as follows: A dispersion of 2-acrylamido-2-methylpropanesulfonic acid and graphene oxide is stirred in an ice-water bath for 25 min. The resulting product is added to a mixer, where polyaniline and ammonium persulfate are added. The mixer is set to 300 rpm and stirred for 25 min. Then, acetone is added to the mixer, and the mixer is set to 300 rpm and stirred for 15 min. The resulting product is then added to a centrifuge and centrifuged at 9000 rpm for 8 min. The supernatant was discarded from the obtained product, and the precipitate was obtained. The precipitate was washed with deionized water and then placed in an oven at 50°C for 7 hours to complete the pretreatment of polyaniline. The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to graphene oxide dispersion was 1:5, the mass of polyaniline was 30% of the mass of 2-acrylamido-2-methylpropanesulfonic acid, the mass of ammonium persulfate was 15% of the mass of polyaniline, and the mass of acetone was 50% of the mass of polyaniline.

[0044] S2: Preparation of the mixture, the raw materials of which include graphene, sodium hydroxide solution, lignite resin, and hydrophobic associative polymer, and the mass of the mixture is 25% of the mass of the additives;

[0045] The method for preparing the mixture is as follows: graphene and sodium hydroxide solution are added to a reaction vessel, and the reaction vessel is stirred at 150 rpm for 25 min. Then, lignite resin and hydrophobic associating polymer are added to the reaction vessel. The reaction vessel is set to a temperature of 85℃, the stirring speed is 250 rpm, and the mixture is stirred at a constant temperature for 50 min. After standing for 5 h, the mixture is obtained. The mass ratio of graphene to sodium hydroxide solution is 1:7, the mass concentration of sodium hydroxide solution is 7%, the mass of lignite resin is 1.7 times the mass of graphene, and the mass of hydrophobic associating polymer is 8% of the mass of lignite resin.

[0046] S3: Mixing process, the additives and the mixture are mixed to obtain the fiber material;

[0047] Preparation of finished product: Weigh out bentonite slurry, fiber material, starch, white asphalt, stabilizer, lubricant, calcium carbonate, barite and water as needed and add them to the mixer. Set the mixer to 500 rpm and stir for 40 minutes to obtain shale gas water-based drilling fluid.

[0048] Example 3:

[0049] Raw material preparation: 100 parts water, 4 parts bentonite slurry, 5 parts fiber material, 4 parts starch, 2 parts white asphalt, 1 part stabilizer, 2 parts lubricant, 4 parts calcium carbonate, 6 parts barite;

[0050] Potassium chloride was selected as the stabilizer, and molybdenum disulfide was selected as the lubricant.

[0051] Fiber material preparation:

[0052] S1: Preparation of additives, the raw materials of which include ketoprofen, methanol, soy protein isolate, multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin.

[0053] The method for preparing the additive is as follows: Ketoprofen and methanol are mixed, and the resulting product is treated in an ultrasonic oscillator for 30 minutes. The resulting product is then added to a mixer, where soy protein isolate is added. The mixer is set to 200 rpm and stirred for 20 minutes. The resulting product is then added to a centrifuge and centrifuged at 10,000 rpm for 10 minutes. The supernatant is discarded from the resulting product, and the solid is obtained. The solid is then placed in an oven and dried at 80°C for 6 hours to obtain a coarse material. The coarse material is then added to a mixer, where multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, and nano-silica are added. Carbon black and epoxy resin were mixed in a mixer at 500 rpm for 60 min. The resulting product was then placed in a vacuum degassing chamber and treated at -0.1 MPa for 30 min to obtain the additive. Polyaniline was pretreated before the additive was prepared. The mass ratio of ketoprofen to methanol was 1:6, the mass of soy protein isolate was 60% of the mass of ketoprofen, and the mass of multi-walled carbon nanotubes was 50% of the mass of the coarse material. The mass ratio of multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin was 1:0.4:0.1:0.2:0.2:0.3.

[0054] The pretreatment method for polyaniline is as follows: A dispersion of 2-acrylamido-2-methylpropanesulfonic acid and graphene oxide is stirred in an ice-water bath for 30 minutes. The resulting product is added to a mixer, where polyaniline and ammonium persulfate are added. The mixer is set to 400 rpm and stirred for 30 minutes. Then, acetone is added to the mixer, and the mixer is set to 400 rpm and stirred for 20 minutes. The resulting product is then added to a centrifuge and centrifuged at 10,000 rpm for 10 minutes. n. The supernatant of the obtained product is discarded, and the precipitate is obtained. The precipitate is washed with deionized water and then sent to an oven to dry at 60°C for 8 hours to complete the pretreatment of polyaniline. The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to graphene oxide dispersion is 1:6. The mass of polyaniline is 40% of the mass of 2-acrylamido-2-methylpropanesulfonic acid, the mass of ammonium persulfate is 20% of the mass of polyaniline, and the mass of acetone is 60% of the mass of polyaniline.

[0055] S2: Preparation of the mixture, the raw materials of which include graphene, sodium hydroxide solution, lignite resin, and hydrophobic associative polymer, and the mass of the mixture is 30% of the mass of the additives;

[0056] The method for preparing the mixture is as follows: graphene and sodium hydroxide solution are added to a reaction vessel, and the reaction vessel is stirred at 200 rpm for 30 min. Then, lignite resin and hydrophobic associating polymer are added to the reaction vessel. The reaction vessel is set to a temperature of 90℃, the stirring speed is 300 rpm, and the mixture is stirred at a constant temperature for 60 min. After standing for 6 h, the mixture is obtained. The mass ratio of graphene to sodium hydroxide solution is 1:8, the mass concentration of sodium hydroxide solution is 10%, the mass of lignite resin is twice the mass of graphene, and the mass of hydrophobic associating polymer is 10% of the mass of lignite resin.

[0057] S3: Mixing process, the additives and the mixture are mixed to obtain the fiber material;

[0058] Preparation of finished product: Weigh out bentonite slurry, fiber material, starch, white asphalt, stabilizer, lubricant, calcium carbonate, barite and water as needed and add them to the mixer. Set the mixer to 600 rpm and stir for 50 minutes to obtain shale gas water-based drilling fluid.

[0059] Comparative Example 1:

[0060] The difference between this comparative example and Example 1 is that the polyaniline was not pretreated in this comparative example.

[0061] Comparative Example 2:

[0062] The difference between this comparative example and Example 1 is that this comparative example does not contain any mixture.

[0063] Comparative Example 3:

[0064] The difference between this comparative example and Example 1 is that this comparative example does not contain fiber material.

[0065] Performance testing: The performance of the shale gas water-based drilling fluids prepared in Examples 1, 2, 3, 1, 2, and 3 (Comparative Examples) was tested, and the test data are recorded in the table below:

[0066] Table 1

[0067] Testing items Filtration loss (ml) Apparent viscosity (mPa·s) Plastic viscosity (mPa·s) Example 1 2.8 46.7 32.5 Example 2 2.9 45.3 31.1 Example 3 3.1 45.8 31.4 Comparative Example 1 7.2 42.6 28.9 Comparative Example 2 8.5 41.5 26.7 Comparative Example 3 9.8 39.2 25.6

[0068] It is evident that the filtration loss and viscosity performance of the shale gas water-based drilling fluids prepared in Comparative Examples 1, 2, and 3 are all lower than those in Examples 1, 2, and 3. This indicates that in the preparation of shale gas water-based drilling fluids, ketoprofen, as an organic acid, can undergo solvation when mixed with methanol to modify soy protein isolate. Methanol, as a solvent, aids in dispersion and reaction. Utilizing the hydration and viscosity of soy protein isolate, the viscosity of the drilling fluid can be increased, and the cross-linking of protein chains helps form a filter cake. The high aspect ratio and strength of multi-walled carbon nanotubes can form a network structure in the drilling fluid, increasing viscosity while simultaneously filling the pores of the filter cake, reducing permeability, decreasing filtration loss, and improving drilling performance. Regarding the performance of the drilling fluid, after pretreatment, 2-acrylamide-2-methylpropanesulfonic acid introduces sulfonic acid groups, improving the water solubility and thermal stability of polyaniline. Graphene oxide provides hydrophilicity and dispersibility, enhancing the mechanical strength and dispersibility of polyaniline, enabling it to form a stable filter cake in the drilling fluid system, reducing filtration loss, and increasing the viscosity of the drilling fluid. The addition of graphene to the mixture allows it to form a dense structure in the drilling fluid using its high specific surface area, further reducing filtration loss. Lignite resin and hydrophobic associating polymers form a three-dimensional network in water through the association of hydrophobic groups, increasing the viscosity of the drilling fluid and improving its shear dilution.

[0069] By comparing and analyzing the relevant data in the table, it can be seen that the shale gas water-based drilling fluid prepared by this invention not only has good filtration loss performance but also excellent viscosity properties. This indicates that the shale gas water-based drilling fluid formulation provided by this invention has a broader market prospect and is more suitable for widespread application.

[0070] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0071] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A shale gas water-based drilling fluid formulation, characterized in that: Including the following raw materials: Bentonite slurry, fiber material, starch, white asphalt, stabilizer, lubricant, calcium carbonate, barite, and water; the mass parts of each raw material are: 100 parts water, 2-4 parts bentonite slurry, 3-5 parts fiber material, 2-4 parts starch, 1-2 parts white asphalt, 0.6-1 part stabilizer, 1-2 parts lubricant, 2-4 parts calcium carbonate, and 4-6 parts barite; The fiber material is prepared by the following method: S1: Preparation of additives, the raw materials of which include ketoprofen, methanol, soy protein isolate, multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin. S2: Preparation of the mixture, the raw materials of which include graphene, sodium hydroxide solution, lignite resin, and hydrophobic associative polymer, and the mass of the mixture is 20-30% of the mass of the additives; S3: Mixing process, the additives and the mixture are mixed to obtain the fiber material.

2. The shale gas water-based drilling fluid formulation according to claim 1, characterized in that, The method for preparing the additive is as follows: After mixing ketoprofen and methanol, the resulting product was treated in an ultrasonic oscillator for 20–30 min. The product was then added to a mixer, where soy protein isolate was added. The mixer was set to 100–200 rpm and stirred for 10–20 min. The resulting product was then centrifuged at 8000–10000 rpm for 6–10 min. The supernatant was discarded, yielding a solid. This solid was then placed in an oven at 60–80 °C. The material is dried at ℃ for 4-6 hours to obtain coarse material. The coarse material is added to a mixer, where multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano-silica, carbon black, and epoxy resin are added. The mixer is set to 300-500 rpm and stirred for 40-60 minutes. The resulting product is sent to a vacuum degassing chamber and treated at -0.09--0.1 MPa for 20-30 minutes to obtain the additive. Polyaniline is pretreated before the preparation of the additive.

3. The shale gas water-based drilling fluid formulation according to claim 2, characterized in that, The mass ratio of ketoprofen to methanol is 1:(4-6), the mass of soy protein isolate is 40-60% of the mass of ketoprofen, the mass of multi-walled carbon nanotubes is 30-50% of the mass of coarse material, and the mass ratio of multi-walled carbon nanotubes, polyaniline, N-methylpyrrolidone, nano silica, carbon black, and epoxy resin is 1:(0.2-0.4):(0.08-0.1):(0.1-0.2):(0.1-0.2):(0.2-0.3).

4. The shale gas water-based drilling fluid formulation according to claim 2, characterized in that, The pretreatment method for polyaniline is as follows: 2-acrylamido-2-methylpropanesulfonic acid and graphene oxide dispersion are stirred in an ice-water bath for 20-30 minutes. The resulting product is added to a mixer, where polyaniline and ammonium persulfate are added. The mixer is set to 200-400 rpm and stirred for 20-30 minutes. Then, acetone is added to the mixer, and the mixer is set to 200-400 rpm and stirred for 10-20 minutes. The resulting product is added to a centrifuge and centrifuged at 8000-10000 rpm for 6-10 minutes. The supernatant is discarded from the resulting product, and the precipitate is obtained. The precipitate is washed with deionized water and then sent to an oven. The oven is set to 40-60℃ and dried for 6-8 hours to complete the pretreatment of polyaniline.

5. The shale gas water-based drilling fluid formulation according to claim 4, characterized in that, The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to graphene oxide dispersion is 1:(4-6), the mass of polyaniline is 20-40% of the mass of 2-acrylamido-2-methylpropanesulfonic acid, the mass of ammonium persulfate is 10-20% of the mass of polyaniline, and the mass of acetone is 40-60% of the mass of polyaniline.

6. The shale gas water-based drilling fluid formulation according to claim 1, characterized in that, The method for preparing the mixture is as follows: graphene and sodium hydroxide solution are added to a reaction vessel, the reaction vessel is set to stir at 100-200 rpm for 20-30 min, lignite resin and hydrophobic associating polymer are added to the reaction vessel, the reaction vessel is set to temperature of 80-90℃, the stirring speed is 200-300 rpm, the mixture is stirred at a constant temperature for 40-60 min, and then allowed to stand for 4-6 h to obtain the mixture.

7. The shale gas water-based drilling fluid formulation according to claim 6, characterized in that, The mass ratio of graphene to sodium hydroxide solution is 1:(6-8), the mass concentration of sodium hydroxide solution is 5-10%, the mass of lignite resin is 1.5-2 times the mass of graphene, and the mass of hydrophobic associative polymer is 6-10% of the mass of lignite resin.

8. The shale gas water-based drilling fluid formulation according to claim 1, characterized in that, The stabilizer is potassium chloride.

9. The shale gas water-based drilling fluid formulation according to claim 1, characterized in that, The lubricant used is molybdenum disulfide.

10. A method for preparing a shale gas water-based drilling fluid, characterized in that, The shale gas water-based drilling fluid formulation as described in any one of claims 1 to 9 was used; the preparation method includes the following steps: weighing bentonite slurry, fiber material, starch, white asphalt, stabilizer, lubricant, calcium carbonate, barite, and water as needed and adding them to a mixer, setting the mixer to 400-600 rpm and stirring for 30-50 minutes to obtain the shale gas water-based drilling fluid.