A new environmentally friendly nano shale inhibitor and its preparation method and application

Abstract

The present invention provides a novel environmentally friendly nano-shale inhibitor, and its preparation method and application. The present invention extracts chitin from shrimp shells through an environmentally friendly low eutectic solvent and uses TEMPO (2,2,6,6-tetramethylpiperidinyl oxide), sodium bromide, sodium hypochlorite, and sodium hydroxide to modify the chitin to obtain modified chitin nanofibrils. The preparation method of the present invention has a simple process, a fast reaction speed, stable product quality, and can be quickly dispersed in drilling fluid. The system has good inhibitory properties. Laboratory evaluation shows that its inhibitory effect is better than the KCl inhibitor commonly used on site. In addition, the inhibitor has a wide source of raw materials, strong temperature resistance, and is easy to prepare. It will not cause further damage to the formation and is a novel shale inhibitor with excellent environmental performance.

Description

Technical Field

[0001] The present invention belongs to the field of drilling fluid and oil and gas development, and specifically relates to a novel environmentally friendly nano shale inhibitor and a preparation method and application thereof. Background Art

[0002] Shale is currently the primary source of unconventional oil and gas. Since the United States leapt from an energy importer to an exporter through shale gas extraction, shale gas development has gradually attracted global attention. Especially in today's world, where energy demand is surging and environmental protection requirements are increasing, the clean and efficient extraction of shale gas has become a pressing issue. Shale is rich in clay. When drilling into shale formations, the clay rapidly hydrates, expands, or disperses upon contact with the water in the drilling fluid. This causes formation pressure to be transmitted through fractures into the formation, leading to formation collapse and wellbore instability. While oil-based drilling fluids can mitigate these issues when drilling shale formations, their high cost, resistance to degradation, and significant environmental hazards have significantly limited their use. Therefore, the development of high-performance water-based drilling fluids is crucial. Shale inhibitors, as an essential additive in water-based drilling fluids, have a wide range of applications.

[0003] There are many types of shale inhibitors in common use. According to the mechanism of action, they can be roughly divided into inorganic salts, polymers and nanomaterial inhibitors. The main function of inorganic salt shale inhibitors, such as KCl, is to +Metal cations such as potassium chloride (KCl) exchange with clay, allowing them to penetrate the clay crystal layers, creating close contact between the layers and reducing the ingress of water molecules, achieving effective inhibition. However, this approach also has significant drawbacks. Under high-temperature and high-pressure formation conditions, large amounts of KCl can produce harmful substances, seriously polluting the environment. Polymer-based shale inhibitors, on the other hand, utilize their long molecular chains to simultaneously adsorb onto the surfaces of multiple clay grains. This bridging effect inhibits crystal expansion, improves film formation efficiency, eliminates pressure transmission, stabilizes the wellbore, and reduces collapse. However, polymers often reduce mud permeability, impacting drilling fluid performance. Nanomaterials inherently possess excellent properties. Their small size, large specific surface area, and strong adsorption properties allow them to physically adsorb onto shale surfaces, plugging pores and reducing water intrusion. Extensive research on shale inhibitors has been conducted, but most have drawbacks such as environmental pollution, biotoxicity, and non-biodegradability. Numerous patents have also been published regarding environmentally friendly shale inhibitors. For example, Chinese patent document CN116515128A discloses a method for preparing an environmentally friendly shale inhibitor, comprising the following steps: S1: preparing cotton straw powder, adding an alkaline solution, heating in a water bath, filtering, adjusting the pH of the slurry to 4-5, adding ethanol for reaction, filtering again, and collecting the filtrate; S2: mixing [EMiM]CH3COO ionic liquid with the filtrate under a protective atmosphere and vacuum conditions, stirring and heating, filtering, and obtaining crude lignin from the filter residue; S3: extracting with tetrahydrofuran as a solvent to obtain refined lignin; S4: dissolving the refined lignin in water, adding a p-toluenesulfonic acid solution, heating in a water bath, adding dropwise a 2,3-epoxypropyltrimethylammonium chloride solution, and maintaining the temperature for reaction. After the reaction is completed, the mixture is centrifuged and separated, and the supernatant is freeze-dried to obtain the lignin. Chinese patent document CN113698510A discloses a modified chitosan as an environmentally friendly biomimetic shale inhibitor for water-based drilling fluids. The modified chitosan is attached with a modifying group having a structure represented by formula (1): -CH2-CH(OH)CH2-polyamine structure; the polyamine structure is provided by a polyamine compound. Although the shale inhibitor is made from natural polymers, it has been chemically modified, resulting in low environmental performance.

[0004] Therefore, there is an urgent need to develop an environmentally friendly nano-shale inhibitor that can effectively inhibit shale hydration expansion. Summary of the Invention

[0005] To address the shortcomings of existing technologies, particularly the environmentally inadequate biodegradability of existing shale inhibitors, their inability to meet environmental requirements while effectively inhibiting shale hydration expansion, the present invention provides a novel environmentally friendly nano-shale inhibitor, its preparation method, and its application. The shale inhibitor of the present invention exhibits excellent shale inhibition effectiveness, favorable environmental performance, and a certain degree of temperature resistance.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a novel environmentally friendly nano-shale inhibitor comprises the following steps:

[0008] (1) adding shrimp shell powder to a deep eutectic solvent (DESs) to react; after the reaction is completed, adding water, standing, filtering, centrifuging, washing, and drying the filtered solid to obtain an intermediate product I; mixing the intermediate product I with a hydrogen peroxide solution, performing a decolorization reaction, filtering, and drying to obtain chitin;

[0009] (2) adding 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and sodium bromide to water, then adding chitin, stirring evenly to obtain a mixed solution, adding sodium hypochlorite to the mixed solution, mixing evenly, and reacting, using a pH regulator to control the pH of the system to 10-11 during the reaction; after the reaction is completed, adding ethanol, standing for precipitation, filtering, and freeze-drying to obtain an intermediate product II;

[0010] (3) The intermediate product II is added to a sodium hydroxide aqueous solution to react. After the reaction is completed, water is added to dilute the reaction product. After filtering, washing, ultrasonic dispersion, and centrifugation, the supernatant is collected and freeze-dried to obtain a new environmentally friendly nano shale inhibitor.

[0011] According to the present invention, the shrimp shell powder in step (1) is obtained by grinding shrimp shells into powder and passing through a 200-mesh sieve.

[0012] According to the present invention, preferably, the deep eutectic solvent (DESs) in step (1) is obtained by mixing choline chloride and lactic acid at 100° C., and the mass ratio of choline chloride to lactic acid is 0.1-0.2:1; the mass ratio of the deep eutectic solvent (DESs) to shrimp shell powder is 1.5-4.5:1, and more preferably 1.9-3:1.

[0013] Preferably, according to the present invention, the reaction temperature in step (1) is 110-130° C., and the reaction time is 30-60 min; the reaction is carried out in a microwave hydrothermal parallel synthesizer with a power of 300-500 W.

[0014] Preferably, according to the present invention, the ratio of the added volume of water to the mass of the shrimp shell powder in step (1) is 10-30 mL:1 g, and the static sedimentation time is 20-40 min; the centrifugal washing is to add water to the solid for centrifugal washing, and the ratio of the volume of water added each time to the mass of the shrimp shell powder is 5-10 mL:1 g; the number of centrifugal washings is 5-10 times.

[0015] Preferably, according to the present invention, the mass fraction of the hydrogen peroxide solution in step (1) is 10-15%; and the mass ratio of the hydrogen peroxide solution to the intermediate product I is 20-40:1.

[0016] Preferably, according to the present invention, the temperature of the decolorization reaction in step (1) is 80-100° C., and the time of the decolorization reaction is 20-40 min; the decolorization reaction is carried out in a microwave hydrothermal parallel synthesizer with a microwave power of 300-500 W.

[0017] According to the preferred embodiment of the present invention, the drying temperature in step (1) is 60-90° C., and the drying time is 10-12 h.

[0018] According to the preferred embodiment of the present invention, the mass ratio of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) to chitin in step (2) is 0.1-0.2:10.

[0019] Preferably, according to the present invention, the mass ratio of sodium bromide to chitin in step (2) is 0.5 to 2:10.

[0020] Preferably, according to the present invention, the ratio of the volume of water to the mass of chitosan in step (2) is 100-200 mL:1 g.

[0021] Preferably, according to the present invention, the mass ratio of sodium hypochlorite to chitosan in step (2) is 10 to 18:1.

[0022] According to the preferred embodiment of the present invention, the pH regulator in step (2) is a 0.5% by mass sodium hydroxide aqueous solution and a 0.5% by mass dilute hydrochloric acid aqueous solution.

[0023] Preferably, according to the present invention, in step (2), a pH regulator is continuously added during the reaction to adjust the pH of the system to 10-11, and the reaction is stopped after the pH of the system does not change within 10-15 minutes.

[0024] According to the preferred embodiment of the present invention, the volume ratio of ethanol to chitin in step (2) is 1-2.5 mL:1 g; after adding ethanol, stirring for 30 minutes and then standing to precipitate, the precipitation time is 60-120 minutes, and the supernatant is removed and filtered.

[0025] According to the preferred embodiment of the present invention, the freeze-drying temperature in step (2) is -25°C to -15°C; and the freeze-drying time is 20 to 30 hours.

[0026] Preferably, according to the present invention, the mass fraction of the sodium hydroxide aqueous solution in step (3) is 15-40%; and the ratio of the volume of the sodium hydroxide aqueous solution to the mass of the intermediate product II is 10-30 mL:1 g.

[0027] According to the preferred embodiment of the present invention, the reaction temperature in step (3) is 80-100° C.; and the reaction time is 0.5-1.5 h.

[0028] Preferably, according to the present invention, the ratio of the added volume of water to the mass of the intermediate product II in step (3) is 80-150 mL:1 g.

[0029] Preferably, according to the present invention, the washing in step (3) is to wash the filtered solid until the filtrate is neutral; the ultrasonic dispersion step is to add water to the washed solid, and ultrasonically treat for 20 to 40 minutes, wherein the ratio of the volume of water added during the ultrasonic process to the mass of the intermediate product II is 40 to 60 mL: 1 g; the freeze-drying temperature is -25°C to -15°C; and the freeze-drying time is 20 to 30 hours.

[0030] A new environmentally friendly nano shale inhibitor is prepared by the above preparation method.

[0031] According to the present invention, the above-mentioned new environmentally friendly nano shale inhibitor is used in deep well shale formation drilling; preferably, the specific application method is to add the obtained new environmentally friendly nano shale inhibitor to the drilling fluid, and the mass fraction of the inhibitor in the drilling fluid is 1-2%.

[0032] The technical features and beneficial effects of the present invention are as follows:

[0033] 1. The preparation of the novel environmentally friendly nano-shale inhibitor of the present invention is first carried out by extracting chitin with a low eutectic solvent composed of choline chloride and lactic acid, and then modifying the chitin with TEMPO (2,2,6,6-tetramethylpiperidinyl oxide), sodium bromide, sodium hypochlorite, and sodium hydroxide. The resulting nano-chitosan fibril inhibitor has good inhibitory and dispersibility under high temperature conditions, and can play a significant inhibitory role in mud shale formations. At the macro level, on the one hand, the nano-chitosan fibrils can effectively surround the surface of the clay particles to form a nano-film, inhibiting the water absorption and expansion of the clay. On the other hand, the nano-fibrils can block the micro-nano cracks in the shale formation and reduce the well wall collapse caused by water entering the formation. At the micro level, the nano-fibrils themselves also carry NH2 + Cations and COO- anions, the former can combine with negatively charged clay particles, making the nanoparticles better wrapped around the clay particles, while NH2 + Cations can also be inserted into the clay layers, preventing water molecules from entering the clay and further inhibiting the hydration expansion of the clay.

[0034] 2. The deep eutectic solvents (DESs) used in the present invention can be reused after treatment, which improves the utilization rate of the agent. The nano-chitosan fibrils can be well dispersed in the drilling fluid, the system is stable, and the rheological properties of the drilling fluid can be improved; it can resist high temperatures of 150°C while playing an excellent inhibitory role.

[0035] 3. The present invention modifies chitin without grafting its surface, which greatly improves its ability to inhibit shale hydration and expansion, and has excellent environmental performance compared to other shale inhibitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the linear expansion height change of sodium bentonite in different shale inhibitor solutions in the test example.

[0037] Figure 2 is the rolling recovery rate of shale cuttings treated with different shale inhibitors in the test case. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to specific examples so that those skilled in the art can better understand the present invention and implement it, but the examples are not intended to limit the present invention.

[0039] Unless otherwise specified, the materials used in the examples can be obtained from commercial sources.

[0040] Example 1

[0041] A method for preparing a novel environmentally friendly nano-shale inhibitor comprises the following steps:

[0042] (1) Weigh 25 g of choline chloride and 170 g of lactic acid, mix them, and place them in a microwave hydrothermal parallel synthesizer. React at 100 °C and 500 W for 10 min to obtain deep eutectic solvents (DESs).

[0043] (2) Grind the shrimp shells into powder and pass them through a 200-mesh sieve (pore size 74 μm). Weigh 100 g of the shrimp shell powder, mix it with 195 g of the DESs obtained in step (1), and place it in a microwave hydrothermal parallel synthesizer. React for 40 min at 120° C. and 500 W. After the reaction is completed, add 2000 mL of water to the resulting reaction solution for dilution, let it settle for 30 min, remove the supernatant, filter, and add water to the precipitate obtained by filtration and centrifuge and wash it 6 times (the mass ratio of the volume of water added each time to the shrimp shell powder is 10 mL:1 g). Wash away excess DESs, and dry the remaining solid at 90° C. for 10 h to obtain intermediate product I.

[0044] (3) 11.5 g of intermediate product I was mixed evenly with 345 g of a 10% hydrogen peroxide solution, placed in a microwave hydrothermal parallel synthesizer, decolorized for 30 min at a temperature of 90°C and a power of 500 W, filtered, and the filtered solid was dried at 90°C for 10 h to obtain chitin.

[0045] (4) Weigh 0.15 g of TEMPO and 1 g of sodium bromide and add them to 1000 mL of water. Stir until the solid particles are fully dissolved, then add 10 g of chitin to obtain a mixed solution. Weigh 150 g of sodium hypochlorite and add it to the mixed solution. Mix thoroughly, add 0.5% by mass of sodium hydroxide aqueous solution and 0.5% by mass of dilute hydrochloric acid aqueous solution to adjust the pH of the system to 10.5. During the reaction, continue to add 0.5% by mass of sodium hydroxide aqueous solution and 0.5% by mass of dilute hydrochloric acid aqueous solution to control the pH of the system to 10.5. After the pH value of the system does not change for 15 minutes, stop the reaction. Add 20 mL of anhydrous ethanol to the reaction solution, stir for 30 minutes, let it settle for 100 minutes, remove the supernatant and filter, and freeze-dry the filtered solid at -20°C for 24 hours to obtain intermediate product II.

[0046] (5) 1 g of intermediate product II was added to 25 mL of a 33% NaOH aqueous solution and reacted at 90°C for 1 hour under nitrogen protection. The experiment was stopped immediately after the reaction was completed. 100 mL of water was immediately added to the reaction product to dilute it and naturally cooled to room temperature. After filtration, the resulting precipitate was washed with water until the filtrate was neutral, dispersed in 50 mL of water, and ultrasonically treated for 30 minutes. After centrifugation, the supernatant was obtained and freeze-dried at -20°C for 24 hours to obtain a new environmentally friendly nano shale inhibitor, which was recorded as A1.

[0047] Example 2

[0048] A method for preparing a novel environmentally friendly nano-shale inhibitor is as described in Example 1, except that the mass fraction of the NaOH aqueous solution in step (5) is 15%. The obtained novel environmentally friendly nano-shale inhibitor is denoted as A2.

[0049] Comparative Example 1

[0050] A method for preparing an environmentally friendly shale inhibitor is as described in Example 1, except that the modification in steps (4) to (5) is not performed. The obtained inhibitor is recorded as B1.

[0051] Comparative Example 2

[0052] A method for preparing an environmentally friendly shale inhibitor comprises the following steps:

[0053] Steps (1)-(3) are the same as steps (1)-(3) in the embodiment;

[0054] (4) Weigh 10 g of chitosan and mix it with 300 g of 3 mol / L hydrochloric acid solution, put it into a microwave hydrothermal parallel synthesizer, and stir and heat it at 100 ° C and a power of 500 W for 30 minutes. After the reaction is completed, stop the experiment immediately, add 1000 mL of water to the reaction product immediately to dilute it and naturally cool it to room temperature. After filtering, wash the resulting precipitate with distilled water until the filtrate is neutral; disperse it in 500 mL of water, ultrasonically treat it for 30 minutes, and obtain the supernatant after centrifugation. The obtained supernatant is freeze-dried at -20 ° C for 24 hours to obtain an environmentally friendly nano shale inhibitor, which is recorded as B2.

[0055] Comparative Example 3

[0056] A method for preparing an environmentally friendly shale inhibitor is as described in Example 1, except that the modification in step (5) is not performed. The obtained inhibitor is recorded as B3.

[0057] Comparative Example 4

[0058] A method for preparing an environmentally friendly shale inhibitor is as described in Example 1, except that the reaction temperature in step (5) is 60° C. The obtained environmentally friendly nano shale inhibitor is denoted as B4.

[0059] Comparative Example 5

[0060] A method for preparing an environmentally friendly shale inhibitor is as described in Example 1, except that the reaction temperature in step (5) is 120° C. The obtained environmentally friendly nano shale inhibitor is denoted as B5.

[0061] Test example

[0062] The inhibitors prepared in the above examples and comparative examples were respectively prepared into suspensions with a mass fraction of 2%, and the performance was evaluated with a 2% mass fraction potassium chloride solution using the following experimental method:

[0063] 1. Linear expansion test

[0064] Take 10g of sodium bentonite, put it into a pressing instrument and press it under a pressure of 10MPa for 5min to make a mud block, and put it into beakers filled with pure water, 2% potassium chloride solution, 2% B1 suspension, 2% B2 suspension, 2% B3 suspension, 2% B4 suspension, 2% B5 suspension, 2% A1 suspension and 2% A2 suspension respectively, and install it on the linear dilatometer, set the running time to 16h, and test the expansion height of the bentonite core by the shale linear dilatometer. The smaller the linear expansion height of the bentonite block, the stronger the inhibitory effect of the inhibitor. Figure 1 Schematic diagram of the linear expansion height change of each mud block within 16 hours.

[0065] 2. Rolling recycling experiment

[0066] Shale cuttings with a particle size of 6 to 10 mesh were screened out and placed in reactors containing pure water, 2% potassium chloride solution, 2% B1 suspension, 2% B2 suspension, 2% B3 suspension, 2% B4 suspension, 2% B5 suspension, 2% A1 suspension and 2% A2 suspension, and rolled and heated at 150°C in a roller heating furnace for 16 hours. The remaining shale cuttings in the reactor were then filtered with a 40-mesh sieve, washed with water, placed in an oven and dried for 24 hours, and then weighed. The weight of the cuttings before rolling heating is recorded as W1, and the weight of the cuttings after rolling heating is recorded as W2. The shale rolling recovery rate R is calculated according to the following formula. The shale rolling recovery rate is:

[0067] R=W2 / W1*100%

[0068] Figure 2 Rolling recovery rates of shale cuttings treated with different shale inhibitors.

[0069] 3. Drilling fluid compatibility test

[0070] 36g of bentonite and 2.7g of sodium carbonate were added to 900mL of water and stirred for 24 hours to prepare a drilling fluid base slurry. 6g of potassium chloride was added to 300mL of the base slurry, and 6g of the new environmentally friendly nano-shale inhibitor A1 was added to another 300mL of the base slurry. The remaining 300mL of the base slurry served as a control group. The rheological and fluid loss properties of the three cups of base slurry were measured using a six-speed rotational viscometer and an API medium-pressure fluid loss tester. The three cups of base slurry were then placed in an aging tank and subjected to rolling aging at 150°C in a roller heating furnace for 16 hours. After the base slurry in the aging tank cooled to room temperature, the rheological and fluid loss properties of the base slurry were measured again. The results are shown in Table 1.

[0071] Table 1

[0072]

[0073] Experimental results demonstrate that the new environmentally friendly nano-shale inhibitor significantly reduces the linear expansion height of bentonite blocks, outperforming potassium chloride shale inhibitors at the same concentration and exhibiting excellent compatibility with drilling fluids. Furthermore, the inhibitor has a wide range of raw material sources, is simple to prepare, is biodegradable, and is environmentally friendly and pollution-free. Compared to potassium chloride, it exhibits superior inhibitory and heat resistance, withstanding temperatures up to 150°C. This meets environmental requirements for mining and has broad application prospects in green oilfield construction. Furthermore, compared to unmodified chitin, the new environmentally friendly shale inhibitor of the present invention significantly improves its ability to inhibit the hydration expansion of clay minerals. Furthermore, the final alkali treatment step is crucial to the performance of the shale inhibitor; inappropriate alkali concentration and treatment temperature can reduce its performance.

[0074] In summary, the novel environmentally friendly nano-shale inhibitor of the present invention can effectively inhibit the hydration expansion of clay minerals and meet the requirements of deep well shale formation drilling.

[0075] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0076] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for preparing a novel environmentally friendly nano-shale inhibitor, comprising the following steps: (1) adding shrimp shell powder to a low eutectic solvent for reaction; after the reaction is completed, adding water, allowing to stand, filtering, centrifuging and washing the filtered solid, and drying to obtain an intermediate product I; mixing the intermediate product I with a hydrogen peroxide solution, performing a decolorization reaction, filtering, and drying to obtain chitin; The deep eutectic solvent is obtained by mixing choline chloride and lactic acid at 100° C., wherein the mass ratio of choline chloride to lactic acid is 0.1-0.2:1; and the mass ratio of the deep eutectic solvent to shrimp shell powder is 1.5-4.5:

1. (2) 2,2,6,6-tetramethylpiperidinyl oxide and sodium bromide are added to water, and then chitin is added and stirred evenly to obtain a mixed solution. Sodium hypochlorite is added to the mixed solution, mixed evenly, and reacted. During the reaction, a pH regulator is used to control the pH of the system to 10-11. After the reaction is completed, ethanol is added, and the mixture is allowed to stand for precipitation, filtered, and freeze-dried to obtain an intermediate product II. (3) The intermediate product II is added to a sodium hydroxide aqueous solution to react. After the reaction is completed, water is added to dilute the reaction product. After filtering, washing, ultrasonic dispersion, and centrifugation, the supernatant is collected and freeze-dried to obtain a new environmentally friendly nano shale inhibitor.

2. The preparation method of the novel environmentally friendly nano shale inhibitor according to claim 1 is characterized in that: The mass ratio of the low eutectic solvent to the shrimp shell powder in step (1) is 1.9-3:

1.

3. The preparation method of the novel environmentally friendly nano shale inhibitor according to claim 1 is characterized in that: The reaction temperature in step (1) is 110-130° C., and the reaction time is 30-60 min. The reaction is carried out in a microwave hydrothermal parallel synthesizer at a power of 300-500 W. The ratio of the added volume of water to the mass of the shrimp shell powder is 10-30 mL:1 g, and the static sedimentation time is 20-40 min; the centrifugal washing is to add water to the solid for centrifugal washing, and the ratio of the volume of water added each time to the mass of the shrimp shell powder is 5-10 mL:1 g; the number of centrifugal washings is 5-10 times.

4. The method for preparing the novel environmentally friendly nano shale inhibitor according to claim 1, characterized in that: The mass fraction of the hydrogen peroxide solution in step (1) is 10-15%; the mass ratio of the hydrogen peroxide solution to the intermediate product I is 20-40:1; The decolorization reaction temperature is 80-100° C., and the decolorization reaction time is 20-40 min. The decolorization reaction is carried out in a microwave hydrothermal parallel synthesizer with a microwave power of 300-500 W. The drying temperature is 60-90° C., and the drying time is 10-12 hours.

5. The preparation method of the novel environmentally friendly nano shale inhibitor according to claim 1 is characterized in that: The mass ratio of the 2,2,6,6-tetramethylpiperidinyl oxide to chitin in step (2) is 0.1-0.2:10; the mass ratio of the sodium bromide to chitin is 0.5-2:10; the volume ratio of the water to the mass ratio of the chitin is 100-200 mL:1 g; and the mass ratio of the sodium hypochlorite to chitin is 10-18:

1.

6. The method for preparing the novel environmentally friendly nano shale inhibitor according to claim 1, characterized in that: The pH regulator in step (2) is a 0.5% by mass sodium hydroxide aqueous solution and a 0.5% by mass dilute hydrochloric acid aqueous solution; During the reaction, pH regulator was continuously added to adjust the pH of the system to 10-11. When the pH of the system did not change within 10-15 minutes, the reaction was stopped. The volume ratio of the ethanol to the mass of the chitin is 1-2.5 mL:1 g; after adding the ethanol, stirring for 30 minutes and then standing to settle for 60-120 minutes, removing the supernatant and filtering; The freeze-drying temperature is -25°C to -15°C; the freeze-drying time is 20 to 30 hours.

7. The method for preparing the novel environmentally friendly nano shale inhibitor according to claim 1, characterized in that: The mass fraction of the sodium hydroxide aqueous solution in step (3) is 15-40%; the ratio of the volume of the sodium hydroxide aqueous solution to the mass of the intermediate product II is 10-30 mL:1 g.

8. The method for preparing the novel environmentally friendly nano shale inhibitor according to claim 1, characterized in that: The reaction temperature in step (3) is 80-100°C; the reaction time is 0.5-1.5h; The ratio of the added volume of water to the mass of the intermediate product II is 80-150 mL:1 g; The washing step comprises washing the filtered solid until the filtrate is neutral; the ultrasonic dispersion step comprises adding water to the washed solid and ultrasonically treating for 20 to 40 minutes, wherein the ratio of the volume of water added during the ultrasonic process to the mass of the intermediate product II is 40 to 60 mL:1 g; the freeze-drying temperature is -25°C to -15°C; and the freeze-drying time is 20 to 30 hours.

9. A new environmentally friendly nano shale inhibitor, characterized by: The preparation method according to claim 1 is used for preparation.

10. Use of the novel environmentally friendly nano-shale inhibitor according to claim 9 in deep well shale formation drilling, characterized in that: The obtained new environmentally friendly nano shale inhibitor is added to the drilling fluid, and the mass fraction of the inhibitor in the drilling fluid is 1-2%.

Images