Bentonite dispersity regulator for maintaining stable performance of high-density drilling fluid under CO2 pollution condition and application thereof

Abstract

The invention discloses a bentonite dispersity regulator for maintaining stable performance of a high-density drilling fluid under a CO2 pollution condition and application of the bentonite dispersity regulator, and belongs to the technical field of drilling engineering materials. A bionic layer-by-layer self-assembly method is adopted, functional components including a polymer containing a strong cation group, a small molecule polymer proppant and a polyanion stabilizer are sequentially added, a charge compensation-space support-electric double-layer repulsion triple synergistic structure is constructed on the surfaces of bentonite particles, and through the synergistic effect of the multiple components, the charge compensation-space support-electric double-layer repulsion effect is achieved. Even under the conditions that the CO2 concentration is high and the pH is obviously reduced, good bentonite dispersing performance can still be kept, particle flocculation and sedimentation are inhibited, the drilling fluid is suitable for a high-density drilling fluid system, the circulation period of the drilling fluid is prolonged, and the well wall stability is improved.

Description

Technical Field

[0001] This invention relates to the field of drilling engineering technology, and in particular to a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions and its application. Background Technology

[0002] In deep oil and gas exploration, water-based drilling fluids are widely used due to their excellent carrying capacity and environmental friendliness. However, in environments where CO2 gas intrudes into the formation, CO2 readily dissolves in the drilling fluid and reacts with water to form H2CO3, which further dissociates into H+. + and HCO3 - This acidification leads to a significant decrease in the pH of the drilling fluid system. Such acidification conditions disrupt the surface structure and charge balance of bentonite particles, causing deagglomeration of their interlayer structure, neutralization of surface charge, and a decrease in zeta potential. Consequently, it weakens the electrostatic repulsion between particles, inducing large-scale flocculation and sedimentation.

[0003] This phenomenon is particularly pronounced in high-density drilling fluid systems. Because high-density systems typically have a high solids content, interparticle interactions are enhanced, making the system more susceptible to disturbances in acidic environments. Decreased structural stability directly leads to problems such as deteriorated rheological properties (e.g., reduced shear thinning capacity, increased dynamic shear force), weakened carrying capacity, and increased fluid loss, thereby jeopardizing wellbore stability and operational safety.

[0004] Although inhibitors (such as potassium salts, organic amines, polymers, etc.) are often used in existing systems to control bentonite dispersion and hydration, these inhibitors often exhibit weak buffering capacity, poor stability, or insufficient acidification resistance under CO2 erosion, resulting in a significant decrease in their inhibitory performance and making it difficult to effectively control bentonite flocculation and mud instability.

[0005] Therefore, there is an urgent need to develop a bentonite dispersant that can maintain stability under CO2 pollution conditions. This dispersant should possess good acid resistance, sustainable buffering capacity, and particle surface adsorption capacity, effectively inhibiting structural damage and maintaining the colloidal stability and rheological properties of the slurry, thereby meeting the safety and stability requirements of drilling operations under CO2 pollution conditions in high-temperature and high-pressure formations. Summary of the Invention

[0006] This invention belongs to the field of drilling fluid chemical regulation technology, specifically relating to a bentonite dispersant suitable for CO2-polluted environments, its construction method, and its application. This invention discloses a bentonite dispersant for maintaining the stable performance of high-density drilling fluids under CO2-polluted conditions and its application. The invention employs a biomimetic layer-by-layer self-assembly method, sequentially adding functional components to construct a triple synergistic structure of charge compensation, spatial support, and electrostatic repulsion on the surface of bentonite particles. Through the synergistic effect of multiple components, even under conditions of high CO2 concentration and significant pH decrease, it can still maintain good bentonite dispersion performance, inhibit particle flocculation and sedimentation, adapt to high-density drilling fluid systems, extend the drilling fluid circulation cycle, and improve wellbore stability.

[0007] This invention provides a bentonite dispersant for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions, comprising the following functional components by weight: 10-30 parts of a polyamine polymer containing strong cationic groups, 30-50 parts of a small molecule polymer proppant, and 20-40 parts of a polyanionic stabilizer.

[0008] Preferably, the bentonite stabilizer further comprises the following components in parts by weight: 1-3 parts complexing agent and 0.1-1 parts nonionic surfactant.

[0009] Preferably, the polyamine polymer containing strong cationic groups is either polydimethyldiallylammonium chloride or polyethyleneimine.

[0010] Preferably, the small molecule polymer support is any one of polyethylene glycol, polyoxyethylene, polyetheramine, or a flexible short-chain polymer containing ether bonds.

[0011] Preferably, the polyanionic stabilizer is a polymer containing a large number of anionic groups, wherein the anionic groups are –COO- groups or –SO3 groups. - Group.

[0012] Preferably, the complexing agent is EDTA or sodium citrate, and the nonionic surfactant is Tween-80 or Brij series.

[0013] This invention also provides the application of the aforementioned bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions. The bentonite dispersant regulator utilizes a biomimetic layer-by-layer self-assembly method to construct a triple synergistic structure on the surface of bentonite particles. The triple synergistic structure sequentially includes:

[0014] Charge compensation layer: a dense primary adsorption layer formed on the surface of bentonite by polyamine polymers containing strong cationic groups;

[0015] The space support layer, small molecule polymer proppant, due to its high hydration capacity, constructs a spatial steric structure through hydrogen bonds and flexible interspersed chain segments between bentonite sheets, providing physical support and hydration layer stability;

[0016] In addition, an electrically repulsive double layer is formed, with polyanionic polymers and charge compensation layer forming a stable electrically double layer structure, which forms an outer dispersion shell outside the bentonite sheets, improving the overall dispersibility and anti-settling ability of the system.

[0017] Preferably, it includes the following steps:

[0018] S1. The dispersed bentonite suspension is mixed with a polyamine polymer containing strong cationic groups and stirred in a weakly acidic environment, so that the polyamine polymer containing strong cationic groups is rapidly adsorbed onto the negatively charged bentonite sheet surface to form a dense primary adsorption layer; effectively improving the adhesion stability of bentonite particles under acidic conditions.

[0019] S2. Add a small molecule polymer proppant to the solution of S1 to form a spatial support layer;

[0020] S3. In the solution of S2, a polyanionic stabilizer is introduced under a neutral to slightly acidic environment to form an electrically repulsive bilayer.

[0021] S4. Add a complexing agent to the mixed solution of S3 to complex the metal ions in the solution and reduce the influence of metal ions on bentonite.

[0022] S5. Add a nonionic surfactant to the solution in S4 to reduce the interaction between particles, prevent the adhesion of polymer and bentonite particles, and ensure good dispersibility and flowability.

[0023] Preferably, in step S1, the concentration of the bentonite suspension is 4%, and the mixing ratio with the polyamine polymer containing strong cationic groups is 0.1% to 1%.

[0024] Preferably, in step S1, the pH value of the weakly acidic environment is 4.0–5.0, and the pH adjuster is dilute hydrochloric acid; in step S3, the pH value of the neutral to slightly acidic environment is 6.0–7.0, and the pH adjuster is phosphate hydrochloride buffer.

[0025] Therefore, this invention provides a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions and its application, which has the following beneficial effects:

[0026] (1) Strong resistance to CO2 pollution

[0027] This invention significantly improves the stability of the regulator in a CO2-acidified environment by introducing an amphoteric structure and a pH buffering mechanism. Even under conditions of high CO2 concentration and significant pH decrease, it still maintains good bentonite dispersion performance and inhibits particle flocculation and sedimentation.

[0028] (2) Multi-mechanism synergy ensures stability and significant dispersion effect.

[0029] The bentonite dispersant uses a triple stabilization mechanism of cationic polyamine adsorption, steric hindrance constructed by branched small molecules, and electrostatic repulsion enhanced by polyanions. This effectively constructs a composite dispersion structure of "adsorption layer – support layer – charge layer", enabling bentonite particles to remain stably suspended in the drilling fluid system for a long time.

[0030] (3) Adaptable to high-density drilling fluid systems

[0031] The regulator of this invention can be used in high solid content (density 1.8-2.4 g / cm³) 3 When applied under certain conditions, it effectively solves the problem of rapid particle aggregation caused by the reduction in the spacing between bentonite particles and the enhancement of electrostatic shielding, thereby extending the drilling fluid circulation cycle and improving wellbore stability.

[0032] (4) Good high-temperature stability

[0033] The polymer components selected in this invention have good thermal stability, the system can withstand temperatures above 150°C, are not easily degraded under deep well and ultra-deep well construction conditions, and have stable performance.

[0034] (5) Directly improves the macroscopic properties of drilling fluid

[0035] The bentonite dispersion stabilizer disclosed in this invention not only effectively controls the dispersion state of bentonite particles at the microscopic level, avoiding flocculation and sedimentation problems caused by CO2 pollution, but also significantly improves the macroscopic performance of drilling fluids, including rheological properties, filtration properties, lubrication properties, and suspension stability. Attached Figure Description

[0036] Figure 1 The particle size distribution of the mixture of regulator and bentonite slurry prepared in Example 1 of this invention before and after CO2 pollution is shown.

[0037] Figure 2 The particle size distribution of the mixture of regulator and bentonite slurry prepared in Example 2 of this invention before and after CO2 pollution is shown.

[0038] Figure 3 The particle size distribution of the mixture of regulator and bentonite slurry prepared in Example 3 of this invention before and after CO2 pollution is shown.

[0039] Figure 4The particle size distribution of the mixture of regulator and bentonite slurry prepared in Example 4 of this invention before and after CO2 pollution is shown.

[0040] Figure 5 The particle size distribution of the mixture of the regulator and bentonite slurry prepared in the comparative proportion of this invention before and after CO2 pollution is shown. Detailed Implementation

[0041] The present invention will be further described below through specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.

[0042] This invention discloses a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions. Its components, component weight ratios, and component functions are briefly described in Table 1 below:

[0043] Table 1. Component weight ratio and component function

[0044]

[0045]

[0046] Among them, the polyamine polymer containing strong cationic groups is either polydimethyldiallylammonium chloride or polyethyleneimine.

[0047] The small molecule polymer support is any one of polyethylene glycol, polyoxyethylene, polyetheramine, or a flexible short-chain polymer containing ether bonds.

[0048] Polyanionic stabilizers are polymers containing a large number of anionic groups, specifically –COO- or –SO3- groups. 2 - Groups, such as sodium polyacrylate (PAA), sodium polymaleate, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) copolymer, etc.

[0049] The complexing agent is EDTA or sodium citrate, and the nonionic surfactant is Tween-80 or Brij series. The complexing agent can effectively capture Ca in the system. 2+ / Mg 2+ Multivalent ions prevent the formation of ion bridges on the surface of bentonite particles, thereby inhibiting flocculation and maintaining the suspension stability of the mud. In addition, nonionic surfactants can significantly reduce the interfacial tension between the mud and the solid phase and form a dense coating layer on the surface of bentonite particles, enhancing wettability and hydrophilic / hydrophobic effects, effectively improving the dispersibility and rheological properties of bentonite.

[0050] This invention also provides the application of the aforementioned bentonite dispersant for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions. The bentonite dispersant constructs a triple synergistic structure of charge compensation, spatial support, and electric double-layer repulsion on the surface of bentonite particles using a biomimetic layer-by-layer self-assembly method, comprising the following steps:

[0051] First layer (cationic adsorption layer): The dispersed bentonite suspension is first mixed with a polyamine polymer containing strong cationic groups, and then stirred and adsorbed in a weakly acidic environment, so that the cationic polymer is quickly adsorbed on the negatively charged bentonite sheet surface to form a dense primary adsorption layer.

[0052] The second layer (supporting molecular intercalation): A highly hydrophilic small molecule polymer support is introduced into the system. It is used to construct a steric structure through hydrogen bonds and flexible intercalation of chain segments between bentonite sheets, which plays a role in physical support and stabilization of the hydration layer.

[0053] The third layer (electrically stabilizing layer): Finally, a polyanionic polymer is introduced, which forms a stable electrical bilayer structure with the cationic layer under neutral to slightly acidic conditions. At the same time, it forms an outer dispersion shell outside the sheet, improving the overall dispersibility and anti-settling ability of the system.

[0054] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0055] Example 1

[0056] This embodiment provides a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions and its application, including the following steps:

[0057] S1. Mix 400 mL of dispersed 4% bentonite suspension with 20 parts of polydimethyldiallylammonium chloride, add dilute hydrochloric acid to adjust the pH, and stir in a weakly acidic environment of pH=4.5 to allow the polyamine polymer containing strong cationic groups to be rapidly adsorbed onto the negatively charged bentonite sheet surface to form a dense primary adsorption layer.

[0058] S2. Add 35 parts of polyethylene glycol to the solution of S1. Due to its high hydrophilicity, it constructs a spatial steric structure through hydrogen bonds and flexible interpenetration of chain segments between bentonite sheets, playing a role in physical support and stabilizing the hydration layer, thus forming a spatial support layer.

[0059] S3. Add phosphate hydrochloride buffer to adjust the pH, and introduce 30 parts of sodium polyacrylate in a neutral to slightly acidic environment of pH=6.0 to form an electrical double repulsion layer, thereby obtaining bentonite molecules bound to the bentonite dispersibility regulator.

[0060] S4. Add 1 part of complexing agent EDTA to the mixed solution of S3 to complex the metal ions in the solution and reduce the influence of metal ions on bentonite.

[0061] S5. Add 0.5 parts of nonionic surfactant Tween-80 to the solution in S4 to reduce the interaction between particles, prevent the adhesion of polymer and bentonite particles, and ensure good dispersibility and flowability.

[0062] Example 2

[0063] This embodiment provides a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions and its application, including the following steps:

[0064] S1. Mix 400 mL of dispersed 4% bentonite suspension with 25 parts of polydimethyldiallylammonium chloride, add dilute hydrochloric acid to adjust the pH, and stir in a weakly acidic environment of pH=4.8 to allow the polyamine polymer containing strong cationic groups to be rapidly adsorbed onto the negatively charged bentonite sheet surface to form a dense primary adsorption layer.

[0065] S2. Add 40 parts of polyethylene glycol to the solution of S1. Due to its high hydrophilicity, it constructs a spatial steric structure through hydrogen bonds and flexible interpenetration of chain segments between bentonite sheets, playing a role in physical support and stabilizing the hydration layer, thus forming a spatial support layer.

[0066] S3. Add phosphate hydrochloride buffer to adjust the pH, and introduce 35 parts of sodium polyacrylate in a neutral to slightly acidic environment of pH=6.2 to form an electrical double repulsion layer, thereby obtaining bentonite molecules bound to the bentonite dispersibility regulator.

[0067] S4. Add 2 parts of sodium citrate, a complexing agent, to the mixed solution of S3 to complex the metal ions in the solution and reduce the influence of metal ions on bentonite.

[0068] S5. Add 0.8 parts of the nonionic surfactant Tween-80 to the solution in S4 to reduce the interaction between particles, prevent the adhesion of polymer and bentonite particles, and ensure good dispersibility and flowability.

[0069] Example 3

[0070] This embodiment provides a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions and its application, including the following steps:

[0071] S1. Mix 400 mL of dispersed 4% bentonite suspension with 30 parts of polydimethyldiallylammonium chloride, add dilute hydrochloric acid to adjust the pH, and stir in a weakly acidic environment of pH=4.7 to allow the polyamine polymer containing strong cationic groups to be rapidly adsorbed onto the negatively charged bentonite sheet surface, forming a dense primary adsorption layer.

[0072] S2. Add 30 parts of polyethylene glycol to the solution of S1. Due to its high hydrophilicity, it constructs a spatial steric structure through hydrogen bonds and flexible interpenetration of chain segments between bentonite sheets, playing a role in physical support and stabilizing the hydration layer, thus forming a spatial support layer.

[0073] S3. Add phosphate hydrochloride buffer to adjust the pH, and introduce 25 parts of sodium polyacrylate in a neutral to slightly acidic environment of pH=6.0 to form an electrical double repulsion layer, thereby obtaining bentonite molecules bound to the bentonite dispersibility regulator.

[0074] S4. Add 1.5 parts of complexing agent EDTA to the mixed solution of S3 to complex the metal ions in the solution and reduce the influence of metal ions on bentonite.

[0075] S5. Add 0.6 parts of nonionic surfactant Tween-80 to the solution in S4 to reduce the interaction between particles, prevent the adhesion of polymer and bentonite particles, and ensure good dispersibility and flowability.

[0076] Example 4

[0077] This embodiment provides a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions and its application, including the following steps:

[0078] S1. Mix 400 mL of dispersed 4% bentonite suspension with 30 parts of polyethyleneimine, add dilute hydrochloric acid to adjust the pH, and stir in a weakly acidic environment of pH=4.6 to allow the polyamine polymer containing strong cationic groups to be rapidly adsorbed onto the negatively charged bentonite sheet surface, forming a dense primary adsorption layer.

[0079] S2. Add 30 parts of polyoxyethylene to the solution of S1. Due to its high hydrophilicity, it constructs a spatial steric structure through hydrogen bonds and flexible interpenetration of chain segments between bentonite sheets, playing a role in physical support and stabilizing the hydration layer, thus forming a spatial support layer.

[0080] S3. Add phosphate hydrochloride buffer to adjust the pH, and introduce 20 parts of sodium polyacrylate in a neutral to slightly acidic environment of pH=6.3 to form an electrical double repulsion layer, thereby obtaining bentonite molecules that are combined with the bentonite dispersibility regulator.

[0081] S4. Add 2 parts of complexing agent EDTA to the mixed solution of S3 to complex the metal ions in the solution and reduce the influence of metal ions on bentonite.

[0082] S5. Add 1 part of nonionic surfactant Tween-80 to the solution in S4 to reduce the interaction between particles, prevent the adhesion of polymer and bentonite particles, and ensure good dispersibility and flowability.

[0083] Comparative Example

[0084] The dispersant used was commercially available lignin sulfonate, which was mixed with 400 mL of dispersed 4% bentonite suspension.

[0085] Application examples

[0086] The bentonite dispersant-bentonite slurry-colloidal systems prepared in Examples 1–4 and the comparative samples were contaminated at 150°C and 1 MPa CO2 pressure for 4 hours. After contamination, the pH of the system decreased to approximately 6.0. Performance evaluations were performed on the samples before and after contamination, including: rheological and filtration performance testing, suspension stability testing, particle size distribution analysis, and zeta potential measurement.

[0087] 1. Rheological property testing

[0088] The rheological properties of the modifier-bentonite slurry mixtures obtained in Examples 1-4 and the comparative examples were tested using a six-speed viscometer (1103 rotational viscometer, Qingdao Chuangmeng Instrument Co., Ltd.), and the results are shown in Table 2.

[0089] Table 2. Rheological properties of bentonite slurry with different modifiers before and after CO2 pollution.

[0090]

[0091]

[0092] As shown in Table 2, the dispersant of this invention exhibits excellent viscosity adjustment and filtration performance. Even with a significant decrease in pH value before and after contamination, the rheological parameters remain relatively unchanged, the mud viscosity retention rate is above 90%, and the shear recovery is good. In particular, the changes in Φ600 / Φ300 and Φ200 / Φ100 are small, indicating that the dispersant still plays a crucial role in improving the fluidity of the drilling fluid.

[0093] 2. Filtration performance test

[0094] The rheological properties of the modifier-bentonite slurry mixtures obtained in Examples 1-4 and the comparative example were measured using an API filtration loss meter (SD4 multi-stage medium-pressure filtration loss meter, Qingdao Haitongda Special Instrument Factory) for 30 minutes. The filtration loss performance parameters are shown in Table 3.

[0095] Table 3. Filtration performance of bentonite slurry with different modifiers before and after CO2 pollution.

[0096]

[0097]

[0098] Compared with the comparative example, when the filtration loss increased from 15 mL to 25 mL after contamination, the filtration loss of the dispersant in this invention did not change significantly after contamination. The bentonite slurry maintained good dispersibility and colloidal stability, with a reasonable particle size distribution and dense sludge cake. This fully demonstrates that the regulator used has excellent anti-interference ability under CO2 pollution conditions, effectively inhibiting the destruction of bentonite structure and flocculation behavior.

[0099] 3. Suspension stability test

[0100] The suspension stability of the mixtures of regulators and bentonite slurry obtained in Examples 1-4 and the comparative example was tested using a centrifuge (LC-05A type centrifuge, Jiangsu Zhengji Instrument Co., Ltd.). Constant-speed centrifugation was used, with the following parameters set: rotor speed 1000 r / min, centrifugation time 10 min. The results are shown in Table 4.

[0101] Table 4. Suspension stability of bentonite slurry with different modifiers before and after CO2 pollution.

[0102]

[0103]

[0104] As can be seen from Table 4, compared with the comparative example where the solid-liquid separation rate increased slightly from 17% to 34%, the regulator of the present invention has a better effect on the stability of bentonite particle dispersion, and no obvious sedimentation occurred. The regulator inhibited particle flocculation and sedimentation.

[0105] 4. Particle size distribution test

[0106] The particle size distribution of the modifier-bentonite slurry mixtures obtained in Examples 1-5 and the comparative example before and after CO2 pollution was determined using a Mastersize laser particle size analyzer. Figure 1-5 As shown.

[0107] Depend on Figure 1-5It can be seen that the particle size distribution of the regulator of the present invention did not change much before and after CO2 pollution when mixed with bentonite. The particle size distribution curve did not show a rightward shift trend, indicating that the bentonite particles did not aggregate and had good dispersibility.

[0108] 5. Zeta potential test

[0109] The Zeta potentials of the modifier-bentonite slurry mixtures obtained in Examples 1-4 and the comparative example before and after CO2 pollution were measured using a Zetasizer NanoZ nanoparticle size potentiostat. The results are shown in Table 5 below:

[0110] Table 5. Zeta potentials of bentonite slurries with different modifiers before and after CO2 pollution.

[0111]

[0112]

[0113] As can be seen from Table 5, compared with the comparative example, the negative charge decreased slightly when the Zeta potential of Examples 1-4 increased from -44mV to -29mV. However, due to the effect of the regulator, the electrostatic repulsion decreased slightly, and no aggregation or flocculation occurred. The overall dispersion was good.

[0114] Therefore, this invention discloses a bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions and its application. It adopts a biomimetic layer-by-layer self-assembly method, and by adding functional components in sequence, a triple synergistic structure of charge compensation, spatial support and electric double-layer repulsion is constructed on the surface of bentonite particles. Through the synergistic effect of multiple components, even under conditions of high CO2 concentration and significant pH decrease, it can still maintain good bentonite dispersion performance, inhibit particle flocculation and sedimentation, adapt to high-density drilling fluid systems, prolong the drilling fluid circulation cycle and improve wellbore stability.

[0115] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and does not limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bentonite dispersant for maintaining the stable performance of high-density drilling fluids under CO2 pollution conditions, characterized in that, The bentonite dispersibility modifier comprises the following functional components in parts by weight: 10-30 parts of polyamine polymer containing strong cationic groups, 30-50 parts of small molecule polymer support, and 20-40 parts of polyanionic stabilizer.

2. The bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions according to claim 1, characterized in that, The bentonite stabilizer also includes the following components in parts by weight: 1-3 parts complexing agent and 0.1-1 parts nonionic surfactant.

3. The bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions according to claim 1, characterized in that, The polyamine polymer containing strong cationic groups is either polydimethyldiallylammonium chloride or polyethyleneimine.

4. The bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions according to claim 1, characterized in that, The small molecule polymer support is any one of polyethylene glycol, polyoxyethylene, polyetheramine, or a flexible short-chain polymer containing ether bonds.

5. A bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions, as described in claim 1, is characterized in that... The polyanionic stabilizer is a polymer containing anionic groups, wherein the anionic groups are carboxylate ions or sulfite groups.

6. A bentonite dispersant regulator for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions, as described in claim 2, is characterized in that... The complexing agent is EDTA or sodium citrate, and the nonionic surfactant is Tween-80 or Brij series.

7. The application of a bentonite dispersant as described in any one of claims 1-6 for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions, characterized in that... The bentonite dispersant regulator constructs a triple synergistic structure on the surface of bentonite particles using a biomimetic layer-by-layer self-assembly method. The triple synergistic structure comprises, in sequence: Charge compensation layer: a dense primary adsorption layer formed on the surface of bentonite by polyamine polymers containing strong cationic groups; The spatial support layer consists of a small molecule polymer proppant that flexibly intersects between bentonite sheets through hydrogen bonds and chain segments to construct a spatial steric structure, providing physical support and hydration layer stability. In addition, an electrically repulsive double layer is formed, with polyanionic polymers and charge compensation layer forming a stable electrically double layer structure, which forms an outer dispersion shell outside the bentonite sheets, improving the overall dispersibility and anti-settling ability of the system.

8. The application of the bentonite dispersant regulator according to claim 7 for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions, characterized in that, Specifically, the following steps are included: S1. The dispersed bentonite suspension is mixed with a polyamine polymer containing strong cationic groups and stirred in a weakly acidic environment so that the polyamine polymer containing strong cationic groups is rapidly adsorbed onto the negatively charged bentonite sheet surface to form a dense primary adsorption layer. S2. Add a small molecule polymer proppant to the solution of S1 to form a spatial support layer; S3. In the solution of S2, a polyanionic stabilizer is introduced under a neutral to slightly acidic environment to form an electrically repulsive bilayer. S4. Add a complexing agent to the mixed solution of S3 to complex the metal ions in the solution and reduce the influence of metal ions on bentonite. S5. Add a nonionic surfactant to the solution in S4 to reduce the interaction between particles, prevent the adhesion of polymer and bentonite particles, and ensure good dispersibility and flowability.

9. The application of the bentonite dispersant regulator according to claim 8 for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions, characterized in that, In step S1, the concentration of the bentonite suspension is 4%, and the mixing ratio with the polyamine polymer containing strong cationic groups is 0.1% to 1%.

10. The application of the bentonite dispersant regulator according to claim 8 for maintaining the stability of high-density drilling fluid performance under CO2 pollution conditions, characterized in that, In step S1, the pH range of the weakly acidic environment is 4.0 to 5.0, and the pH adjuster is dilute hydrochloric acid; in step S3, the pH range of the neutral to slightly acidic environment is 6.0 to 7.0, and the pH adjuster is phosphate buffer.

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