An environmentally friendly water-based drilling fluid system based on biomass nanomaterials, its preparation method and application

Abstract

This invention provides an environmentally friendly water-based drilling fluid system based on biomass nanomaterials, its preparation method, and its application, belonging to the field of oilfield drilling fluid technology. The environmentally friendly water-based drilling fluid system includes an environmentally friendly water-based drilling fluid composition and a pH adjuster. The environmentally friendly water-based drilling fluid composition comprises the following raw materials in parts by weight: 100 parts water, 4-6 parts bentonite, 1-2 parts high aspect ratio nanocellulose, 0.4-1.2 parts high surface positive charge chitin nanocrystals, 0.5-1.5 parts amphoteric lignin nanoparticles, 1-1.8 parts biodegradable filtration reducer, and 2-3 parts bio-based lubricant. The pH adjuster adjusts the pH of the biomass nanomaterial-based environmentally friendly water-based drilling fluid system to 8-10. The components used in the water-based drilling fluid system of this invention are safe, environmentally friendly, pollution-free, and easily biodegradable, effectively improving the overall performance of the system and suitable for environmentally friendly drilling operations in environmentally sensitive areas.

Description

Technical Field

[0001] This invention relates to an environmentally friendly water-based drilling fluid system based on biomass nanomaterials, its preparation method and application, belonging to the field of oilfield drilling fluid technology. Background Technology

[0002] Drilling fluid is hailed as the "blood" of drilling, playing an irreplaceable role in carrying cuttings, cooling drill bits, balancing formation pressure, and stabilizing the wellbore. With the continuous development of deep and ultra-deep formations and deep-sea oil and gas resources, drilling fluids not only need to possess excellent rheological properties, filtration control capabilities, and wellbore stability, but must also meet increasingly stringent environmental protection requirements.

[0003] Traditional water-based drilling fluids commonly use synthetic polymers, sulfonated asphalt, and chromium / zinc inorganic salts as treatment agents, which have the following drawbacks: First, they have a high environmental impact, as the polymer backbone is difficult to biodegrade, and the waste drilling fluid contains excessive levels of COD, BOD, and heavy metals, with treatment costs accounting for 8-15% of the total drilling cost; Second, they have poor biodegradability, as synthetic polymers have excessively long half-lives in the natural environment; Third, they have high ecotoxicity and are highly harmful to aquatic organisms.

[0004] Currently, there are numerous patent documents reporting on environmentally friendly drilling fluids. For example, Chinese patent document CN116554845A discloses an environmentally friendly drilling fluid prepared using nanocellulose. This drilling fluid system contains the following components: 4-6% bentonite-based slurry, 1-2% nanocellulose, 0.5-1.5% inhibitor, 0.1-0.5% thickener, 0.2-0.4% coating agent, 0.8-1.4% filtration loss reducer, 2-3% lubricant, 2-3% plugging and anti-collapse agent, 0.1-0.3% alkalinity adjuster, and the remainder is water. However, this environmentally friendly drilling fluid relies solely on nanocellulose, lacks a multi-component synergistic effect, and is only qualitatively described as "easily degradable" without quantitative analysis, making it difficult to meet increasingly stringent environmental regulations. Chinese patent document CN119463824A discloses a natural amphiphilic lignin nanoparticle emulsifier for oil-based drilling fluids. However, this system is limited to oil-based drilling fluids and relies on organic solvents (dioxane) to prepare nanoparticles. The lignin particles cannot offset the overall environmental disadvantages, and the organic solvent is difficult to recover. The residual solvent leads to a high degree of pollution. The process is complex and costly, making it difficult to carry out large-scale green production.

[0005] Therefore, it is urgent to develop a drilling fluid system that combines high performance and environmental protection. It is of great significance to achieve environmental protection throughout the entire chain from raw materials to waste degradation through innovative formulation and green preparation of biomass nanomaterials. Summary of the Invention

[0006] To address the shortcomings of existing technologies, particularly the high biotoxicity, poor degradation, and heavy metal pollution of current water-based drilling fluids, this invention provides an environmentally friendly water-based drilling fluid system based on biomass nanomaterials, its preparation method, and its applications. The water-based drilling fluid system of this invention is a green drilling fluid system that complies with ISO 14040 environmental management standards throughout its entire life cycle. The components used in this system are safe, environmentally friendly, and pollution-free. The composite biomass nanomaterials are widely available and, after modification, can form various high-performance derivatives. Drilling fluids obtained by compounding these with other components not only have no corrosive effect on the wellbore and are easily biodegradable, but also effectively improve the overall performance of the system (such as inhibition and lubrication), making it particularly suitable for environmentally friendly drilling operations in environmentally sensitive areas.

[0007] The technical solution of the present invention is as follows:

[0008] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials includes an environmentally friendly water-based drilling fluid composition and a pH adjuster;

[0009] The environmentally friendly water-based drilling fluid composition comprises the following raw materials in parts by weight: 100 parts water, 4-6 parts bentonite, 1-2 parts high aspect ratio nanocellulose (LRNCF), 0.4-1.2 parts high surface positive charge chitin nanocrystals (ChNCs), 0.5-1.5 parts amphoteric lignin nanoparticles (ALNP), 1-1.8 parts biodegradable filtration loss reducer, and 2-3 parts bio-based lubricant;

[0010] The pH adjuster is used to adjust the pH of the environmentally friendly water-based drilling fluid system based on biomass nanomaterials to 8-10.

[0011] According to a preferred embodiment of the present invention, the environmentally friendly water-based drilling fluid composition comprises the following raw materials in parts by weight: 100 parts water, 5 parts bentonite, 1.5 parts high aspect ratio nanocellulose, 0.8 parts high surface positive charge chitin nanocrystals, 1 part amphoteric lignin nanoparticles, 1.4 parts biodegradable filtration loss reducer, and 2.5 parts bio-based lubricant.

[0012] According to a preferred embodiment of the present invention, the bentonite is calcium-based or sodium-based bentonite.

[0013] According to a preferred embodiment of the present invention, the pH adjuster is an aqueous solution of potassium carbonate, wherein the mass fraction of the aqueous solution of potassium carbonate is 10-30%.

[0014] According to a preferred embodiment of the present invention, the high aspect ratio nanocellulose (LRNCF) has an aspect ratio ≥ 100:1 and a diameter of 10~50 nm; it is prepared from the following raw materials in parts by weight: 100 parts bleached softwood pulp, 0.1~0.5 parts 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO), 1~5 parts sodium bromide (NaBr), 5~15 parts sodium hypochlorite (NaClO) aqueous solution, 20~50 parts anhydrous ethanol, and 200 parts deionized water. 0~5000 parts; the concentration of the sodium hypochlorite (NaClO) aqueous solution is 5~15wt%; preferably, the high aspect ratio nanocellulose (LRNCF) is prepared from the following raw materials in parts by weight: 100 parts of bleached softwood pulp, 0.3 parts of 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO), 2 parts of sodium bromide (NaBr), 10 parts of sodium hypochlorite (NaClO) aqueous solution, 30 parts of anhydrous ethanol, and 3000 parts of deionized water.

[0015] According to a preferred embodiment of the present invention, the high aspect ratio nanocellulose (LRNCF) is prepared by the following method:

[0016] Bleached softwood pulp was dispersed in deionized water, and 2,2,6,6-tetramethylpiperidine-1-oxy free radical (TEMPO) and sodium bromide (NaBr) were added. Sodium hypochlorite (NaClO) aqueous solution was added dropwise, and the reaction was stirred. After the reaction was completed, anhydrous ethanol was added to terminate the reaction. After filtration and washing, the oxidation product was obtained. Then, the product was homogenized under high pressure to obtain an aqueous dispersion of nanocellulose. After centrifugation and freeze-drying, high aspect ratio nanocellulose (LRNCF) was obtained.

[0017] Preferably, in the preparation of high aspect ratio nanocellulose (LRNCF), a 0.5 mol / L NaOH solution is added dropwise simultaneously with the addition of sodium hypochlorite (NaClO) aqueous solution to maintain the pH of the reaction system at 10-10.5; the dropping rate of the sodium hypochlorite (NaClO) aqueous solution is 2-3 mL / min; after the sodium hypochlorite (NaClO) aqueous solution is completely added, the reaction is stirred for 2-4 hours, and during the stirring reaction, a 0.5 mol / L NaOH solution is added dropwise to maintain the pH of the reaction system at 10-10.5.

[0018] Preferably, in the preparation of high aspect ratio nanocellulose (LRNCF), the washing involves washing the filtered solid with deionized water until the filtrate is neutral, and the resulting precipitate is the oxidation product.

[0019] Preferably, in the preparation of high aspect ratio nanocellulose (LRNCF), the high-pressure homogenization step is as follows: the oxidation product is added to water and dispersed, the volume ratio of water to bleached softwood pulp is 50~100mL:1g, to obtain a dispersion, and then high-pressure homogenization is performed. The pressure of the high-pressure homogenization is 40~60MPa, the temperature of the high-pressure homogenization is 15~25℃, the number of high-pressure homogenizations is 3~5, and the time of each high-pressure homogenization is 3~5min.

[0020] Preferably, in the preparation of high aspect ratio nanocellulose (LRNCF), the centrifugation speed is 8000~12000 rpm, the centrifugation time is 5~10 minutes, and the upper suspension is collected; the freeze-drying is to freeze-dry the obtained suspension at -40~-30℃ for 24~48h.

[0021] According to a preferred embodiment of the present invention, the high surface positive charge chitin nanocrystals (ChNCs) are prepared from the following raw materials in parts by weight: 10 parts of deacetylated chitin nanocrystals, 20-40 parts of cationic monomer, 0.3-0.7 parts of initiator, and 500-1000 parts of deionized water; wherein the cationic monomer is dimethyl diallyl ammonium chloride (DMDAAC) and / or methacryloyloxyethyltrimethylammonium chloride (DMC); and the initiator is ammonium persulfate or potassium persulfate.

[0022] According to a preferred embodiment of the present invention, the deacetylated chitosan nanocrystals are commercially available or prepared according to existing technology. More preferably, the deacetylated chitosan nanocrystals are prepared according to the following method:

[0023] (1) Chitosan powder was added to hydrochloric acid aqueous solution for acid hydrolysis, and then centrifuged, washed and dried to obtain chitosan nanocrystals;

[0024] (2) Chitin nanocrystals were dispersed in water to obtain a suspension. NaOH aqueous solution was added to the obtained suspension for alkaline treatment. After the reaction was completed, ice water was immediately added to terminate the reaction. After centrifugation, washing and drying, deacetylated chitin nanocrystals were obtained.

[0025] Preferably, in step (1), the concentration of the hydrochloric acid aqueous solution is 2.5~3.5 mol / L, the volume ratio of the hydrochloric acid aqueous solution to the mass ratio of the chitin powder is 20~40 mL:1 g, the acid hydrolysis temperature is 80~95℃, and the acid hydrolysis time is 2~4 h; the centrifugation speed is 6000~9000 rpm, and the centrifugation time is 5~15 min; the washing involves washing the precipitate obtained by centrifugation with deionized water until the pH of the supernatant is neutral; and the drying involves drying at 50~60℃ to constant weight.

[0026] Preferably, in step (2), the concentration of chitin nanocrystals in the suspension is 1-2 wt%; the concentration of the NaOH aqueous solution is 30-40 wt%; the volume ratio of the NaOH aqueous solution to the mass of the chitin nanocrystals is 20-40 mL:1 g; the temperature of the alkali treatment is 75-85°C, and the time of the alkali treatment is 1-2 h; the temperature of the ice water is 0-4°C, and the volume ratio of the ice water to the mass of the chitin nanocrystals is 40-60 mL:1 g; the centrifugation speed is 6000-10000 rpm, and the centrifugation time is 10-30 min; the washing involves washing the precipitate obtained by centrifugation with deionized water until the pH of the supernatant is neutral; and the drying involves drying at 50-60°C to constant weight.

[0027] According to a preferred embodiment of the present invention, the high surface positive charge chitin nanocrystals are prepared by the following method: deacetylated chitin nanocrystals are added to deionized water, stirred evenly, and then cationic monomers and initiators are added to carry out a polymerization reaction; after the reaction is completed, the nanocrystals are centrifuged, washed, and freeze-dried to obtain high surface positive charge chitin nanocrystals (ChNCs).

[0028] Preferably, in the preparation of chitin nanocrystals with high surface positive charge, the polymerization reaction temperature is 50~60℃, the polymerization reaction time is 3~5h, and the polymerization reaction is carried out under nitrogen protection.

[0029] Preferably, in the preparation of chitin nanocrystals with high surface positive charge, the centrifugation speed is 6000~10000 rpm and the centrifugation time is 10~30 min; the washing is performed by sequentially washing with a NaCl solution with a concentration of 1~3wt% and deionized water; the freeze-drying temperature is -50~-30℃ and the freeze-drying time is 24~48 h.

[0030] According to a preferred embodiment of the present invention, the amphoteric lignin nanoparticles (ALNP) are prepared from the following raw materials in parts by weight: 100 parts alkali lignin, 0.3-0.7 parts initiator, 20-30 parts dimethyl diallyl ammonium chloride (DMDAAC), 15-25 parts sodium p-styrene sulfonate (SSS), and 1500 parts deionized water; wherein the initiator is a redox initiator, wherein the oxidant is potassium persulfate, the reducing agent is sodium bisulfite, and the molar ratio of the oxidant to the reducing agent is 1:1;

[0031] Preferably, the amphoteric lignin nanoparticles (ALNP) are prepared from the following raw materials in parts by weight: 100 parts alkali lignin, 0.5 parts initiator, 25 parts dimethyl diallyl ammonium chloride (DMDAAC), 20 parts sodium p-styrene sulfonate (SSS), and 1500 parts deionized water.

[0032] Preferably, the amphoteric lignin nanoparticles (ALNP) are prepared according to the following method:

[0033] (I) Disperse alkali lignin in deionized water, adjust the pH of the system to 11-12 with a 5-15 wt% NaOH aqueous solution, and stir to dissolve; after purging with nitrogen to remove oxygen, add dimethyl diallyl ammonium chloride (DMDAAC) and an initiator, and react under nitrogen protection; then add sodium p-styrene sulfonate (SSS) and continue the reaction at a constant temperature;

[0034] (II) After the reaction is completed, the system is naturally cooled to room temperature. The pH of the system is adjusted to 6-6.5 to obtain the reaction solution. After dialysis and filtration, the amphoteric lignin dispersion is obtained. After ultrasonic treatment, the amphoteric lignin nanoparticles (ALNP) are obtained.

[0035] Preferably, in the preparation of amphoteric lignin nanoparticles (ALNP), in step (I), the time for nitrogen deoxygenation is 15~30 min.

[0036] Preferably, in the preparation of amphoteric lignin nanoparticles (ALNP), after adding dimethyl diallyl ammonium chloride (DMDAAC) and an initiator in step (I), the reaction temperature is 75~85℃ and the reaction time is 2~3h.

[0037] Preferably, in the preparation of amphoteric lignin nanoparticles (ALNP), the sodium p-styrene sulfonate mentioned in step (I) is added dropwise to the system in the form of an aqueous solution of sodium p-styrene sulfonate for 20-40 min, and the concentration of the aqueous solution of sodium p-styrene sulfonate is 20-40 wt%; the reaction time of adding sodium p-styrene sulfonate at a constant temperature is 2-4 h.

[0038] Preferably, in the preparation of amphoteric lignin nanoparticles (ALNP), in step (II), an aqueous HCl solution with a concentration of 0.1~0.2 mol / L is used to adjust the pH of the reaction solution to 6~6.5.

[0039] Preferably, in the preparation of amphoteric lignin nanoparticles (ALNP), the dialysis step in step (II) is as follows: the reaction solution is placed into a dialysis bag with a molecular weight cutoff of 8000~14000 Da, and dialyzed in deionized water. The deionized water is replaced every 4-8 hours until the pH of the dialysis solution is neutral, and the dispersion in the dialysis bag is obtained. Then, a 0.22 μm filter membrane is used to filter and remove large particulate impurities to obtain an amphoteric lignin dispersion.

[0040] Preferably, in the preparation of amphoteric lignin nanoparticles (ALNP), the conditions for ultrasonic treatment in step (II) are as follows: ultrasonic treatment at 200W and 20kHz for 10~20min in an ultrasonic cell disruptor; the freeze-drying temperature is -60~-40℃ and the freeze-drying time is 24~48h.

[0041] According to a preferred embodiment of the present invention, the degradable filtration loss reducing agent is carboxymethyl starch, a commercially available product commonly used in the art.

[0042] According to a preferred embodiment of the present invention, the bio-based lubricant is castor oil or methyl ricinoleate.

[0043] According to the present invention, the preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials includes the following steps:

[0044] (i) Add bentonite to water, stir evenly, and let stand to hydrate to obtain bentonite-based slurry;

[0045] (ii) Under stirring conditions, high aspect ratio nanocellulose (LRNCF), high surface positive charge chitin nanocrystals (ChNCs), amphoteric lignin nanoparticles (ALNP), biodegradable filtration loss reducer, and bio-based lubricant are added to the bentonite-based slurry and stirred evenly to obtain an environmentally friendly water-based drilling fluid composition.

[0046] (iii) Under stirring conditions, potassium carbonate aqueous solution is added dropwise to the environmentally friendly water-based drilling fluid composition obtained in step (ii) to adjust the pH to 8-10, thereby obtaining an environmentally friendly water-based drilling fluid system based on biomass nanomaterials.

[0047] According to a preferred embodiment of the present invention, the stirring speed in step (i) is 800~1200 rpm, the stirring time is 20~40 min, and the hydration time is 6~8 h.

[0048] According to a preferred embodiment of the present invention, in step (ii), after each component is added, the mixture is stirred for 15 to 30 minutes before adding the next component.

[0049] According to the present invention, the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is applied in environmentally sensitive drilling operations in environmentally sensitive areas, including but not limited to deep ocean water, polar regions, nature reserves, or inland water source protection areas.

[0050] The technical features and beneficial effects of this invention are as follows:

[0051] 1. This invention is the first to apply three types of biomass nanomaterials in a specific ratio to drilling fluid, achieving a balance between performance, environmental protection, and cost. The carbon emissions, COD, BOD, heavy metals, and petroleum loads throughout the entire process are reduced by more than 60% compared to traditional systems, establishing a green standard for the entire life cycle from raw material selection to waste disposal.

[0052] 2. In this invention, high aspect ratio nanocellulose can provide a highly elastic framework, chitin nanocrystals enhance the network and inhibit shale hydration by utilizing positive charge and hydrogen bonds, and amphoteric lignin nanoparticles form a dense adsorption and sealing layer in micro-nano pores. The three work together to improve the performance of the drilling fluid system. Attached Figure Description

[0053] Figure 1 Scanning electron microscope image of the high aspect ratio nanocellulose prepared for Example 1.

[0054] Figure 2 Scanning electron microscope image of chitin nanocrystals with high surface positive charge prepared for Example 2.

[0055] Figure 3 Scanning electron microscope image of the amphoteric lignin nanoparticles prepared for Preparation Example 3.

[0056] Figure 4 This is a physical image of the environmentally friendly water-based drilling fluid system based on biomass nanomaterials in Example 1. Detailed Implementation

[0057] The present invention will be further described below through specific embodiments, but is not limited thereto.

[0058] Unless otherwise specified, the experimental methods described in the examples are conventional methods; the reagents and materials used are commercially available unless otherwise specified.

[0059] Unless otherwise specified, the high aspect ratio nanocellulose (LRNCF), high surface positive charge chitin nanocrystals (ChNCs), and amphoteric lignin nanoparticles (ALNP) used in the examples and comparative examples were prepared according to the methods of Preparation Example 1, Preparation Example 2, and Preparation Example 3, respectively.

[0060] Unless otherwise specified, the term "parts" in the embodiments and comparative examples refers to parts by weight.

[0061] Preparation Example 1

[0062] The preparation of high aspect ratio nanocellulose (LRNCF) includes the following steps:

[0063] 100 parts of bleached softwood pulp were dispersed in 3000 parts of deionized water. 0.3 parts of 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and 2 parts of sodium bromide (NaBr) were added. 10 parts of sodium hypochlorite (NaClO) aqueous solution (concentration 10 wt%, dropping rate 3 mL / min) were slowly added dropwise. Simultaneously, 0.5 mol / L NaOH aqueous solution was added dropwise to maintain the pH of the system at 10–10.5. After the sodium hypochlorite (NaClO) aqueous solution was completely added, the reaction was stirred for 3 hours, with 0.5 mol / L NaOH continuously added dropwise during the stirring process. The pH of the system was maintained at 10-10.5 using NaOH aqueous solution. Then, 30 parts of anhydrous ethanol were added to terminate the reaction. The mixture was filtered, and the solid obtained by filtration was washed with deionized water until the filtrate was neutral. The precipitate obtained was the oxidation product. The oxidation product was added to water for dispersion. The volume ratio of water added to the mass of bleached softwood pulp was 60 mL: 1 g to obtain a dispersion. The dispersion was then homogenized under high pressure at 20℃ and 50 MPa four times (5 min each time) to obtain an aqueous dispersion of nanocellulose. The obtained aqueous dispersion of nanocellulose was centrifuged at 10000 rpm for 10 min to remove fibers with low aspect ratio and separate longer fibers. The upper suspension was collected and freeze-dried at -40℃ for 48 h to obtain high aspect ratio nanocellulose (LRNCF).

[0064] The scanning electron microscope image of the high aspect ratio nanocellulose prepared in this example is shown below. Figure 1 As shown, by Figure 1 It can be seen that the prepared nanocellulose has a significant high aspect ratio structure. The fibers are long strips and intertwined network structures. The fiber diameter is about 20~40nm, the length can reach several micrometers, and the aspect ratio is >100:1.

[0065] Preparation Example 2

[0066] A method for preparing chitin nanocrystals with high surface positive charge (ChNCs) includes the following steps:

[0067] (1) Chitosan powder was added to a 3 mol / L hydrochloric acid aqueous solution with a volume ratio of 30 mL to 1 g of chitosan powder. The solution was hydrolyzed at 90 °C for 2 hours. After cooling to room temperature, the resulting reaction solution was centrifuged at 8000 rpm for 10 min. The precipitate was washed with deionized water until the pH of the supernatant was neutral. Then it was dried at 50 °C to constant weight to obtain chitosan nanocrystals.

[0068] (2) Chitosan nanocrystals were added to water to obtain a suspension with a concentration of 2wt%. A NaOH aqueous solution with a concentration of 30wt% was added to the obtained suspension. The volume ratio of the NaOH aqueous solution to the mass of the chitosan nanocrystals was 30mL:1g. The solution was treated at 80℃ for 1h. After the alkaline treatment, the solution was immediately diluted with ice water (temperature 0-4℃) to terminate the reaction. The volume ratio of the ice water to the mass of the chitosan nanocrystals (ChNCs) was 50mL:1g. The resulting mixture was then centrifuged at 9000rpm for 15min. The precipitate obtained by centrifugation was washed with deionized water until the pH of the supernatant was neutral. The precipitate was then dried at 50℃ to constant weight to obtain deacetylated chitosan nanocrystals.

[0069] (3) Add 10 parts of deacetylated chitin nanocrystals to 500 parts of deionized water, stir evenly, then add 30 parts of cationic monomer dimethyl diallyl ammonium chloride (DMDAAC) and 0.5 parts of initiator ammonium persulfate, and carry out polymerization reaction at 60°C for 4 h under nitrogen protection. After the reaction is completed, centrifuge the obtained reaction solution at 9000 rpm for 15 min, discard the supernatant, wash the obtained precipitate with NaCl solution (concentration of 1 wt%) and deionized water in sequence, and freeze dry at -40°C for 48 h to obtain chitin nanocrystals with high surface positive charge (ChNCs).

[0070] The scanning electron microscope image of the highly surface-positively charged chitin nanocrystals prepared in this example is shown below. Figure 2 As shown, by Figure 2 It can be seen that the prepared chitin nanocrystals with high surface positive charge have a uniform rod-shaped structure with a length of about 100~300nm and a diameter of about 5~15nm.

[0071] Preparation Example 3

[0072] A method for preparing amphoteric lignin nanoparticles (ALNP) includes the following steps:

[0073] (1) Disperse 100 parts of alkali lignin in 1500 parts of deionized water, adjust the pH of the system to 12.0 with 10wt% NaOH aqueous solution, stir for 30 min to completely dissolve the alkali lignin; after purging with nitrogen for 20 min to remove oxygen, add 0.5 parts of initiator (potassium persulfate and sodium bisulfite mixed in a molar ratio of 1:1) and 25 parts of dimethyl diallyl ammonium chloride (DMDAAC), and react at 80℃ for 2 h under nitrogen protection; then add sodium p-styrene sulfonate (SSS) aqueous solution (20 parts of sodium p-styrene sulfonate (SSS) added to 46.7 parts of water), and continue to react at 80℃ for 3 h under nitrogen protection; after the reaction is completed, cool naturally to room temperature, add 0.1mol / L HCl aqueous solution to adjust the pH to 6.5, and obtain the reaction solution.

[0074] (2) The reaction solution was placed in a dialysis bag with a molecular weight cutoff of 8000~14000 Da and dialyzed in deionized water for 48 hours. The deionized water was replaced every 6 hours until the pH of the dialysate was neutral. The dispersion in the dialysis bag was filtered with a 0.22 μm filter membrane to remove large particulate impurities and obtain amphoteric lignin dispersion. The obtained amphoteric lignin dispersion was ultrasonically treated with an ultrasonic cell disruptor at 200W and 20kHz for 10 min and then freeze-dried at -50℃ for 48 h to obtain amphoteric lignin nanoparticles (ALNP).

[0075] The scanning electron microscope image of the highly surface-positively charged chitin nanocrystals prepared in this example is shown below. Figure 3 As shown, by Figure 3 It can be seen that the prepared amphoteric lignin nanoparticles are spherical nanoparticles with a particle size between 30-50 nm and have good dispersibility.

[0076] Preparation Example 4

[0077] The preparation method of chitin nanocrystals with high surface positive charge (ChNCs) is as described in Preparation Example 2, except that in step (3), the cationic monomer is replaced with methacryloyloxyethyltrimethylammonium chloride (DMC).

[0078] Example 1

[0079] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials includes an environmentally friendly water-based drilling fluid composition and a pH adjuster;

[0080] The environmentally friendly water-based drilling fluid composition includes the following raw materials in parts by weight: 100 parts water, 5 parts bentonite, 1.5 parts high aspect ratio nanocellulose (LRNCF), 0.8 parts high surface positive charge chitin nanocrystals (ChNCs), 1 part amphoteric lignin nanoparticles (ALNP), 1.4 parts biodegradable filtration loss reducer, and 2.5 parts bio-based lubricant; an appropriate amount of pH adjuster to make the pH of the environmentally friendly water-based drilling fluid system based on biomass nanomaterials 9.5.

[0081] The bentonite is calcium-based bentonite; the biodegradable filtration loss reducer is carboxymethyl starch; the bio-based lubricant is methyl castor oil; and the pH adjuster is a 20% potassium carbonate aqueous solution.

[0082] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials includes the following steps:

[0083] (1) First, add bentonite to water and use a high-speed mixer (1000r / min) to initially stir for 30 minutes to make the bentonite particles evenly dispersed; after stopping the stirring, let the dispersion stand for hydration for 8 hours to obtain bentonite slurry;

[0084] (2) Transfer the bentonite-based slurry to a high-speed shear mixing device, turn on the mixer and adjust the speed to 10,000 rpm. Under the mixing condition of 10,000 rpm, add high aspect ratio nanocellulose (LRNCF), high surface positive charge chitin nanocrystals (ChNCs), amphoteric lignin nanoparticles (ALNP), biodegradable filtration loss reducer and bio-based lubricant in sequence. After each component is added, stir for 15 min before adding the next component. After all raw materials are added, keep stirring at 10,000 rpm for 25 min. Then add pH adjuster dropwise and use a pH meter to monitor the pH value of the system in real time to make the pH of the system uniform and stable to 9.5, thus obtaining an environmentally friendly water-based drilling fluid system based on biomass nanomaterials.

[0085] Example 2

[0086] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 1 part of high aspect ratio nanocellulose (LRNCF), 0.4 parts of high surface positive charge chitin nanocrystals (ChNCs), and 0.5 parts of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0087] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0088] Example 3

[0089] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 1 part of high aspect ratio nanocellulose (LRNCF), 0.8 parts of high surface positive charge chitin nanocrystals (ChNCs), and 1 part of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0090] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0091] Example 4

[0092] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 1 part of high aspect ratio nanocellulose (LRNCF), 1.2 parts of high surface positive charge chitin nanocrystals (ChNCs), and 1.5 parts of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0093] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0094] Example 5

[0095] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 1.5 parts of high aspect ratio nanocellulose (LRNCF), 0.4 parts of high surface positive charge chitin nanocrystals (ChNCs), and 1 part of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0096] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0097] Example 6

[0098] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 1.5 parts of high aspect ratio nanocellulose (LRNCF), 1.2 parts of high surface positive charge chitin nanocrystals (ChNCs), and 1.5 parts of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0099] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0100] Example 7

[0101] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 2 parts of high aspect ratio nanocellulose (LRNCF), 0.4 parts of high surface positive charge chitin nanocrystals (ChNCs), and 1.5 parts of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0102] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0103] Example 8

[0104] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 2 parts of high aspect ratio nanocellulose (LRNCF), 0.8 parts of high surface positive charge chitin nanocrystals (ChNCs), and 0.5 parts of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0105] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0106] Example 9

[0107] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that: 2 parts of high aspect ratio nanocellulose (LRNCF), 1.2 parts of high surface positive charge chitin nanocrystals (ChNCs), and 1 part of amphoteric lignin nanoparticles (ALNP) are used, and the composition of other raw materials is the same as in Example 1.

[0108] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0109] Example 10

[0110] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that the high surface positive charge chitin nanocrystals (ChNCs) used are those prepared in Preparation Example 4.

[0111] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0112] Example 11

[0113] An environmentally friendly water-based drilling fluid system based on biomass nanomaterials is described in Example 1, except that the bio-based lubricant is castor oil.

[0114] The preparation method of the above-mentioned environmentally friendly water-based drilling fluid system based on biomass nanomaterials is as described in Example 1.

[0115] Comparative Example 1

[0116] A water-based drilling fluid system is described in Example 1, except that high aspect ratio nanocellulose (LRNCF), high surface positive charge chitin nanocrystals (ChNCs), and amphoteric lignin nanoparticles (ALNP) are not added, while the other raw material composition is the same as in Example 1.

[0117] The preparation method of the above water-based drilling fluid system is the same as that in Example 1, except that the steps of adding high aspect ratio nanocellulose (LRNCF), high surface positive charge chitin nanocrystals (ChNCs) and amphoteric lignin nanoparticles (ALNP) are omitted.

[0118] Comparative Example 2

[0119] A water-based drilling fluid system is described in Example 1, except that high surface positive charge chitin nanocrystals (ChNCs) and amphoteric lignin nanoparticles (ALNPs) are not added, while the other raw material composition is the same as in Example 1.

[0120] The preparation method of the above water-based drilling fluid system is the same as that in Example 1, except that the steps of adding chitin nanocrystals with high surface positive charge (ChNCs) and amphoteric lignin nanoparticles (ALNP) are omitted.

[0121] Comparative Example 3

[0122] A water-based drilling fluid system is described in Example 1, except that high aspect ratio nanocellulose (LRNCF) and amphoteric lignin nanoparticles (ALNP) are not added, while the other raw material composition is the same as in Example 1.

[0123] The preparation method of the above water-based drilling fluid system is the same as that in Example 1, except that the steps of adding high aspect ratio nanocellulose (LRNCF) and amphoteric lignin nanoparticles (ALNP) are omitted.

[0124] Comparative Example 4

[0125] A water-based drilling fluid system is described in Example 1, except that high aspect ratio nanocellulose (LRNCF) and high surface positive charge chitin nanocrystals (ChNCs) are not added, while the other raw material composition is the same as in Example 1.

[0126] The preparation method of the above water-based drilling fluid system is the same as that in Example 1, except that the steps of adding high aspect ratio nanocellulose (LRNCF) and high surface positive charge chitin nanocrystals (ChNCs) are omitted.

[0127] Comparative Example 5

[0128] A water-based drilling fluid system is described in Example 1, except that amphoteric lignin nanoparticles (ALNP) are not added, while the other raw material composition is the same as in Example 1.

[0129] The preparation method of the above water-based drilling fluid system is the same as that in Example 1, except that the step of adding amphoteric lignin nanoparticles (ALNP) is omitted.

[0130] Comparative Example 6

[0131] A water-based drilling fluid system is described in Example 1, except that high surface positive charge chitin nanocrystals (ChNCs) are not added, while the other raw material composition is the same as in Example 1.

[0132] The preparation method of the above water-based drilling fluid system is the same as that in Example 1, except that the step of adding chitosan nanocrystals (ChNCs) with high surface positive charge is omitted.

[0133] Comparative Example 7

[0134] A water-based drilling fluid system is described in Example 1, except that high aspect ratio nanocellulose (LRNCF) is not added, while the other raw material composition is the same as in Example 1.

[0135] The preparation method of the above water-based drilling fluid system is the same as that in Example 1, except that the step of adding high aspect ratio nanocellulose (LRNCF) is omitted.

[0136] Comparative Example 8

[0137] A water-based drilling fluid system is described in Example 1, except that ordinary cellulose (20~50μm, aspect ratio <10:1) is used instead of high aspect ratio nanocellulose (LRNCF).

[0138] Comparative Example 9

[0139] A water-based drilling fluid system is described in Example 1, except that deacetylated ChNCs (obtained according to steps (1)-(2)) of Preparation Example 2) are used instead of chitin nanocrystals with high surface positive charge (ChNCs).

[0140] Comparative Example 10

[0141] A water-based drilling fluid system is described in Example 1, except that unmodified alkali lignin nanoparticles are used instead of amphoteric lignin nanoparticles (ALNP).

[0142] Experimental Example 1

[0143] The performance of the water-based drilling fluid systems prepared in the examples and comparative examples was evaluated as follows. All samples were tested after being hot-rolled and aged at 150°C for 16 hours.

[0144] (1) Rheological filtration performance evaluation: According to GB / T16783.1-2014 standard, the API filtration loss after aging was measured using a medium-pressure filtration loss meter; the apparent viscosity (AV), plastic viscosity (PV) and dynamic shear force (YP) after aging were measured using a six-speed rotational viscometer, and the results are shown in Table 1.

[0145] Table 1 Test Results

[0146]

[0147] As can be seen from the data in Table 1, compared with Comparative Example 1, after aging at 150℃ for 16h, the API filtration loss of Example 1 decreased sharply from 12.5mL to 4.2mL. At the same time, the rheological parameters such as AV, PV, and YP were significantly improved, indicating that the composite biomass nanomaterial of the present invention can effectively construct a stable spatial network structure and has excellent debris carrying and suspension capabilities.

[0148] (2) The linear expansion rate of drilling fluid on natural sodium montmorillonite tablets was measured using an NP-01 shale expansion instrument at 25℃ and 3MPa. The lower the expansion rate, the stronger the ability to inhibit shale hydration. The results are shown in Table 2.

[0149] Table 2 Test Results

[0150]

[0151] As shown in Table 2, the linear expansion rate of Example 1 was only 12.4%, which was 56% lower than that of Comparative Example 1 (28.7%). This indicates that the high aspect ratio nanocellulose, high surface positive charge chitin nanocrystals and amphoteric lignin nanoparticles work synergistically to form a dense adsorption-coating layer on the shale surface, effectively inhibiting water intrusion and significantly reducing shale hydration expansion.

[0152] (3) Biotoxicity

[0153] In accordance with the requirements of the "Evaluation Method for Environmental Protection Technology of Water-Soluble Oilfield Chemicals" (SY / T6788-2010), the biotoxicity of the prepared environmentally friendly drilling fluid was tested, and its half-maximal effective concentration (EC50) was determined using the luminescent bacteria method. 50 The higher the value, the lower the toxicity, as shown in Table 3.

[0154] Table 3 Test Results

[0155]

[0156] The data in Table 3 shows that the EC in Example 1 50 The concentration of EC 38,600 mg / L is significantly higher than the regulatory threshold for "non-toxic" (≥25,000 mg / L), primarily because all components are renewable biomass or biodegradable materials, free of heavy metals and sulfonating agents. Comparative Example 1, as a traditional system containing no nanomaterials, has an EC 100%. 50 The lowest value (1850 mg / L) confirms its high biotoxicity. Although Comparative Examples 2-7 added some biomass nanomaterials, their EC50 values ​​were low due to the lack of a complete synergistic system. 50 The value only increased slightly, far lower than in the example. This is because the core advantage of the present invention lies in the stable network structure constructed by the three components synergistically. This structure can effectively adsorb, encapsulate, and stabilize trace amounts of toxic substances (e.g., heavy metal ions that may be present in bentonite) in drilling fluid, preventing them from dissolving and causing harm to organisms.

[0157] (4) Biodegradability

[0158] The biodegradability of aged drilling fluid was evaluated according to the standards "Determination of Five-Day Biochemical Oxygen Demand (BOD5) in Water Quality - Dilution and Inoculation Method" (HJ 505-2009) and "Determination of Chemical Oxygen Demand in Water Quality - Dichromate Method" (HJ 828-2017). The five-day biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) were measured, and the BOD5 / COD ratio was calculated. A ratio closer to 1 indicates better biodegradability. The results are shown in Table 4.

[0159] Table 4 Test Results

[0160]

[0161] Table 4 shows that Example 1 exhibits good biodegradability. Comparative Examples 2-7 also used some biomass nanomaterials, but due to the lack of a complete composite system, these materials could not maintain optimal dispersion and stability in drilling fluid, and may aggregate, leading to a reduction in their biodegradable active surface area and thus affecting degradation efficiency. This system has significant environmental advantages and regulatory compliance in environmentally sensitive areas such as polar regions and marine protected areas.

Claims

1. An environmentally friendly water-based drilling fluid system based on biomass nanomaterials, characterized in that, Includes environmentally friendly water-based drilling fluid compositions and pH adjusters; The environmentally friendly water-based drilling fluid composition comprises the following raw materials in parts by weight: 100 parts water, 4-6 parts bentonite, 1-2 parts high aspect ratio nanocellulose, 0.4-1.2 parts high surface positive charge chitin nanocrystals, 0.5-1.5 parts amphoteric lignin nanoparticles, 1-1.8 parts biodegradable filtration reducer, and 2-3 parts bio-based lubricant; the pH adjuster is used to adjust the pH of the environmentally friendly water-based drilling fluid system based on biomass nanomaterials to 8-10; the pH adjuster is an aqueous solution of potassium carbonate. The high aspect ratio nanocellulose has an aspect ratio ≥100:1 and a diameter of 10~50nm; it is prepared from the following raw materials in parts by weight: 100 parts bleached softwood pulp, 0.1~0.5 parts 2,2,6,6-tetramethylpiperidine-1-oxy radical, 1~5 parts sodium bromide, 5~15 parts sodium hypochlorite aqueous solution, 20~50 parts anhydrous ethanol, and 2000~5000 parts deionized water; the concentration of the sodium hypochlorite aqueous solution is 5~15wt%. The high surface positive charge chitin nanocrystals are prepared from the following raw materials in parts by weight: 10 parts deacetylated chitin nanocrystals, 20-40 parts cationic monomer, 0.3-0.7 parts initiator, and 500-1000 parts deionized water; the cationic monomer is dimethyl diallyl ammonium chloride and / or methacryloyloxyethyltrimethylammonium chloride; the initiator is ammonium persulfate or potassium persulfate; The deacetylated chitin nanocrystals were prepared according to the following method: (1) Chitosan powder was added to hydrochloric acid aqueous solution for acid hydrolysis, and then centrifuged, washed and dried to obtain chitosan nanocrystals; (2) Chitin nanocrystals were dispersed in water to obtain a suspension. NaOH aqueous solution was added to the obtained suspension for alkaline treatment. After the reaction was completed, ice water was immediately added to terminate the reaction. After centrifugation, washing and drying, deacetylated chitin nanocrystals were obtained. In step (1), the concentration of the hydrochloric acid aqueous solution is 2.5~3.5 mol / L, the volume ratio of the hydrochloric acid aqueous solution to the mass ratio of chitosan powder is 20~40 mL:1 g, the acid hydrolysis temperature is 80~95℃, and the acid hydrolysis time is 2~4 h; the centrifugation speed is 6000~9000 rpm, and the centrifugation time is 5~15 min; the washing involves washing the precipitate obtained by centrifugation with deionized water until the pH of the supernatant is neutral; and the drying involves drying at 50~60℃ to constant weight. In step (2), the concentration of chitin nanocrystals in the suspension is 1-2 wt%; the concentration of the NaOH aqueous solution is 30-40 wt%; the volume ratio of the NaOH aqueous solution to the mass of the chitin nanocrystals is 20-40 mL:1 g; the temperature of the alkali treatment is 75-85℃, and the time of the alkali treatment is 1-2 h; the temperature of the ice water is 0-4℃, and the volume ratio of the ice water to the mass of the chitin nanocrystals is 40-60 mL:1 g; the centrifugation speed is 6000-10000 rpm, and the centrifugation time is 10-30 min; the washing involves washing the precipitate obtained by centrifugation with deionized water until the pH of the supernatant is neutral; and the drying involves drying at 50-60℃ to constant weight. The amphoteric lignin nanoparticles are prepared from the following raw materials in parts by weight: 100 parts alkali lignin, 0.3-0.7 parts initiator, 20-30 parts dimethyl diallyl ammonium chloride, 15-25 parts sodium p-styrene sulfonate, and 1500 parts deionized water; the initiator is a redox initiator, wherein the oxidant is potassium persulfate, the reducing agent is sodium bisulfite, and the molar ratio of oxidant to reducing agent is 1:1; The biodegradable filtration loss reducer is carboxymethyl starch; the bio-based lubricant is castor oil or methyl ricinoleate.

2. The environmentally friendly water-based drilling fluid system based on biomass nanomaterials according to claim 1, characterized in that, The bentonite is calcium-based or sodium-based bentonite; the mass fraction of the potassium carbonate aqueous solution is 10-30%.

3. The environmentally friendly water-based drilling fluid system based on biomass nanomaterials according to claim 1, characterized in that, The high aspect ratio nanocellulose was prepared according to the following method: Bleached softwood pulp was dispersed in deionized water, and 2,2,6,6-tetramethylpiperidine-1-oxy free radicals and sodium bromide were added. Sodium hypochlorite aqueous solution was added dropwise, and the reaction was stirred. After the reaction was completed, anhydrous ethanol was added to terminate the reaction. After filtration and washing, the oxidation product was obtained. Then, the product was homogenized under high pressure to obtain an aqueous dispersion of nanocellulose. After centrifugation and freeze-drying, high aspect ratio nanocellulose was obtained.

4. The environmentally friendly water-based drilling fluid system based on biomass nanomaterials according to claim 3, characterized in that, In the preparation of high aspect ratio nanocellulose, a 0.5 mol / L NaOH solution was added dropwise simultaneously with the addition of sodium hypochlorite aqueous solution to maintain the pH of the reaction system at 10-10.5; the dropping rate of the sodium hypochlorite aqueous solution was 2-3 mL / min; after the sodium hypochlorite aqueous solution was completely added, the reaction was stirred for 2-4 h, and during the stirring reaction, a 0.5 mol / L NaOH solution was added dropwise to maintain the pH of the reaction system at 10-10.

5. The washing process involves washing the filtered solid with deionized water until the filtrate is neutral, and the resulting precipitate is the oxidation product. The high-pressure homogenization step is as follows: the oxidation product is added to water and dispersed. The volume ratio of water to bleached softwood pulp is 50~100mL:1g to obtain a dispersion. Then, high-pressure homogenization is performed. The pressure of high-pressure homogenization is 40~60MPa, the temperature of high-pressure homogenization is 15~25℃, the number of high-pressure homogenizations is 3~5, and the time of each high-pressure homogenization is 3~5min. The centrifugation speed is 8000~12000 rpm, the centrifugation time is 5~10 minutes, and the upper suspension is collected; the freeze drying is to freeze dry the obtained suspension at -40~-30℃ for 24~48h.

5. The environmentally friendly water-based drilling fluid system based on biomass nanomaterials according to claim 1, characterized in that, The high surface positive charge chitin nanocrystals were prepared by the following method: deacetylated chitin nanocrystals were added to deionized water, stirred evenly, and then cationic monomers and initiators were added to carry out a polymerization reaction; after the reaction was completed, the high surface positive charge chitin nanocrystals were obtained by centrifugation, washing, and freeze-drying. The polymerization reaction is carried out at a temperature of 50-60°C for 3-5 hours under nitrogen protection. The centrifugation speed is 6000-10000 rpm for 10-30 minutes. The washing process involves sequentially washing with a 1-3 wt% NaCl solution and then with deionized water. The freeze-drying temperature is -50 to -30°C for 24-48 hours.

6. The environmentally friendly water-based drilling fluid system based on biomass nanomaterials according to claim 1, characterized in that, The amphoteric lignin nanoparticles were prepared according to the following method: (I) Disperse alkali lignin in deionized water, adjust the pH of the system to 11-12 with a 5-15 wt% NaOH aqueous solution, and stir to dissolve; after purging with nitrogen to remove oxygen, add dimethyl diallyl ammonium chloride and an initiator, and react under nitrogen protection; then add sodium p-styrene sulfonate and continue the reaction at a constant temperature. (II) After the reaction is completed, the system is naturally cooled to room temperature. The pH of the system is adjusted to 6-6.5 to obtain the reaction solution. After dialysis and filtration, the amphoteric lignin dispersion is obtained. After ultrasonic treatment, the amphoteric lignin nanoparticles are obtained by freeze drying.

7. The environmentally friendly water-based drilling fluid system based on biomass nanomaterials according to claim 6, characterized in that, In the preparation of amphoteric lignin nanoparticles, in step (I), the time for nitrogen deoxygenation is 15-30 min; after adding dimethyl diallyl ammonium chloride and the initiator, the reaction temperature is 75-85℃ and the reaction time is 2-3 h; the sodium p-styrene sulfonate is added dropwise to the system in the form of an aqueous solution of sodium p-styrene sulfonate, the dropwise addition time is 20-40 min, and the concentration of the aqueous solution of sodium p-styrene sulfonate is 20-40 wt%; the time for isothermal reaction after adding sodium p-styrene sulfonate is 2-4 h. In step (II), the pH of the reaction solution is adjusted to 6-6.5 using an aqueous HCl solution with a concentration of 0.1-0.2 mol / L. The dialysis step is as follows: the reaction solution is placed in a dialysis bag with a molecular weight cutoff of 8000-14000 Da, and dialyzed in deionized water. The deionized water is replaced every 4-8 hours until the pH of the dialysate is neutral, and the dispersion in the dialysis bag is obtained. Then, it is filtered using a 0.22 μm filter membrane to obtain an amphoteric lignin dispersion. The conditions for the ultrasonic treatment are: ultrasonic treatment at 200W and 20kHz for 10-20 min in an ultrasonic cell disruptor. The freeze-drying temperature is -60 to -40℃, and the freeze-drying time is 24-48 h.

8. The method for preparing the environmentally friendly water-based drilling fluid system based on biomass nanomaterials as described in any one of claims 1-7, characterized in that, The steps include the following: (i) Add bentonite to water, stir evenly, and let stand to hydrate, to obtain bentonite-based slurry; (ii) Under stirring conditions, high aspect ratio nanocellulose, high surface positive charge chitin nanocrystals, amphoteric lignin nanoparticles, biodegradable filtration loss reducer, and bio-based lubricant are added to bentonite-based slurry and stirred evenly to obtain an environmentally friendly water-based drilling fluid composition. (iii) Under stirring conditions, potassium carbonate aqueous solution is added dropwise to the environmentally friendly water-based drilling fluid composition obtained in step (ii) to adjust the pH to 8-10, thereby obtaining an environmentally friendly water-based drilling fluid system based on biomass nanomaterials; The stirring speed in step (i) is 800~1200 rpm, and the stirring time is 20~40 min; the hydration time is 6~8 h; In step (ii), after each component is added, stir for 15-30 minutes before adding the next component.

9. The application of the environmentally friendly water-based drilling fluid system based on biomass nanomaterials as described in any one of claims 1-7 in environmentally sensitive drilling operations, characterized in that, The environmentally sensitive areas include deep ocean waters, polar regions, nature reserves, or inland water source protection areas.

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