PH response type flow pattern regulator suitable for CO2 polluted drilling fluid as well as preparation method and application of pH response type flow pattern regulator

Abstract

The invention provides a pH response type flow pattern regulator suitable for CO2 polluted drilling fluid as well as a preparation method and application of the pH response type flow pattern regulator. The pH response type flow pattern regulator is prepared from the following raw materials in parts by mass: 5 to 10 parts of acrylic acid, 10 to 20 parts of a pH response monomer, 10 to 30 parts of 2-acrylamide-2-methylpropanesulfonic acid, 5 to 20 parts of N-vinyl pyrrolidone, 0.1 to 1 part of an initiator and 100 to 200 parts of water. The flow pattern regulator disclosed by the invention can sense the pH value change of a drilling fluid system caused by CO2 pollution through a pH sensitive group in a molecular structure, and adaptively adjust the interaction strength with clay particles, that is, when the acidity is enhanced, the adsorption capacity is enhanced through group protonation, the aggregated clay particles are effectively dispersed, and the viscosity and shear force of the drilling fluid are reduced; in the pH value rising stage, the stability of the system is maintained through charge density regulation and control, and meanwhile, the filter loss is reduced by improving the mud cake structure.

Description

A pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids, its preparation method and application Technical Field

[0001] This invention relates to a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids, its preparation method and application, belonging to the technical field of drilling fluid treatment agents. Background Technology

[0002] As oil and gas exploration and development continues to advance into deeper, ultra-deep, and unconventional formations, the complex geological environments encountered during drilling are becoming increasingly severe, with CO2 intrusion leading to drilling fluid contamination being a particularly prominent issue. In deep, ultra-deep wells and CO2-bearing reservoirs, CO2 in the formation continuously dissolves in water-based drilling fluids, triggering a series of chain reactions. On one hand, CO2 reacts with water in the drilling fluid to form carbonic acid, causing a decrease in the system's pH value, disrupting clay dispersibility, and leading to particle aggregation. On the other hand, the carbonate and bicarbonate ions produced by the dissociation of carbonic acid react with metal ions in the drilling fluid, further exacerbating the deterioration of rheological properties. Ultimately, this manifests as increased drilling fluid viscosity and shear stress, which in severe cases can cause downhole accidents such as stuck pipe and well kicks.

[0003] The rheological properties of drilling fluid are a core indicator for ensuring safe and efficient drilling, and their stability directly affects wellbore cleanliness, wellbore stability, and drilling fluid circulation efficiency. When CO2 pollution occurs, traditional drilling fluid treatment agents can reduce viscosity to some extent, but they lack the ability to respond to changes in pH value and are often unable to cope with this dynamically changing acidic environment.

[0004] Currently, although some scholars have proposed pH-responsive treatment agents, such as the Chinese patent document CN114075303A which discloses a drilling fluid for formation environment [H] + This invention relates to a responsive wellbore stabilizing agent, its preparation method, and its application. The agent is made from acrylic copolymers, polyesters, organic bases, iron salts, dispersants, and small-molecule organic acids. It achieves a plugging rate exceeding 95% under different temperature conditions, demonstrating excellent plugging ability. Chinese patent document CN113416527A discloses the synthesis of a temperature- and pH-responsive nanogel. This invention has a particle size distribution approximately between 40-120 nm, effectively plugging nanoscale pores in shale wellbores, thereby effectively stabilizing the wellbore and preventing collapse. However, research on rheological control technology for CO2-contaminated drilling fluids is currently relatively scarce.

[0005] Therefore, developing a pH-responsive flow modulator that can adaptively adjust its performance according to the degree of CO2 pollution (i.e., changes in the pH value of the system) has become a key requirement for solving the CO2 pollution problem in deep drilling. Summary of the Invention

[0006] To address the shortcomings of existing technologies, particularly the inability of existing drilling fluid treatment agents to cope with dynamic pH changes caused by CO2 pollution and to synergistically regulate rheological properties, this invention provides a pH-responsive flow modifier suitable for CO2-polluted drilling fluids, along with its preparation method and application. The pH-responsive flow modifier of this invention can sense changes in the pH value of the drilling fluid system caused by CO2 pollution through pH-sensitive groups in its molecular structure, adaptively adjusting the interaction strength with clay particles. Specifically, when acidity increases, it enhances adsorption capacity through protonation of the groups, effectively dispersing aggregated clay particles and reducing drilling fluid viscosity and shear force. During the pH recovery phase, it maintains system stability through charge density regulation while simultaneously improving the mud cake structure to reduce filtration loss.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A pH-responsive flow pattern modifier suitable for CO2-contaminated drilling fluids is prepared from the following raw materials in parts by weight: 5-10 parts acrylic acid (AA), 10-20 parts pH-responsive monomer, 10-30 parts 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 5-20 parts N-vinylpyrrolidone (NVP), 0.1-1 parts initiator, and 100-200 parts water.

[0009] According to a preferred embodiment of the present invention, the pH-responsive flow pattern modifier suitable for CO2-contaminated drilling fluid is prepared from the following raw materials in parts by weight: 6-8 parts acrylic acid (AA), 15-20 parts pH-responsive monomer, 15-30 parts 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 10-15 parts N-vinylpyrrolidone (NVP), 0.2-0.6 parts initiator, and 100-150 parts water.

[0010] Preferably, the pH-responsive flow pattern modifier suitable for CO2-contaminated drilling fluid is prepared from the following raw materials in parts by weight: 7.2 parts acrylic acid (AA), 18.5 parts pH-responsive monomer, 20.7 parts 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 11.14 parts N-vinylpyrrolidone (NVP), 0.5 parts initiator, and 120 parts water.

[0011] According to a preferred embodiment of the present invention, the pH-responsive monomer is ethyl 2-(diethylamino)methacrylate (DMAEMA) and / or ethyl 3-(N,N-dimethylamino)acrylate (DMAE).

[0012] According to a preferred embodiment of the present invention, the initiator is azobisisobutylamidine hydrochloride (AIBA).

[0013] The preparation method of the above-mentioned pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids includes the following steps:

[0014] Acrylic acid (AA), pH-responsive monomers, 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and N-vinylpyrrolidone (NVP) were dispersed in deionized water to obtain a monomer mixture. The pH of the monomer mixture was adjusted to 7-9, an initiator was added, and the reaction was carried out to obtain a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids.

[0015] According to a preferred embodiment of the present invention, a sodium hydroxide aqueous solution with a mass fraction of 20-30% is used to adjust the pH to 7-9.

[0016] According to a preferred embodiment of the present invention, the initiator is added to the system in the form of an aqueous initiator solution, wherein the mass ratio of the initiator to deionized water in the aqueous initiator solution is 0.1-1:15.

[0017] According to a preferred embodiment of the present invention, before adding the initiator, a protective gas is first introduced into the system to remove oxygen for 20-40 minutes, wherein the protective gas is nitrogen or argon.

[0018] According to a preferred embodiment of the present invention, the reaction temperature is 65-75°C, the reaction time is 3-5 hours, and the reaction is carried out under the protection of a protective gas and under stirring conditions, wherein the protective gas is nitrogen or argon.

[0019] According to the present invention, the above-mentioned pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids is applied as a flow pattern regulator to CO2-contaminated drilling fluids to reduce drilling fluid viscosity, shear stress and filtration loss.

[0020] The technical features and beneficial effects of this invention are as follows:

[0021] 1. The preparation process of this invention is simple. The raw materials used, such as acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone, are common varieties in the chemical industry, which are inexpensive and easy to obtain. The parameters such as temperature and time in the synthesis process are easy to control, and no complicated equipment is required. The resulting pH-responsive rheology modifier is safe and environmentally friendly, has no irritating odor, and has a low production cost, making it suitable for industrial production.

[0022] 2. The pH-responsive rheology modifier of this invention addresses the core problem of CO2-contaminated drilling fluids and has excellent rheological regulation capabilities. Its outstanding feature is its strong responsiveness to changes in pH value. When CO2 intrusion leads to increased acidity in the drilling fluid, the pH-sensitive groups in the pH-responsive monomer molecular structure will be protonated, enhancing the interaction with clay particles and effectively reducing the apparent viscosity (AV) and plastic viscosity (PV) of the drilling fluid. At the same time, it can improve the quality of the mud cake, reduce filtration loss, and significantly improve drilling efficiency under CO2 contamination conditions.

[0023] 3. The introduction of pH-responsive monomers in this invention is the key to achieving pH-responsive function: the tertiary amino group in its molecule can be protonated to form a cationic group in an acidic environment, which enhances the electrostatic adsorption with negatively charged clay particles and promotes particle dispersion; while when the pH value rises, the tertiary amino group is deprotonated, which can reduce the viscosity rebound caused by excessive adsorption and achieve dynamic control of drilling fluid rheology.

[0024] 4. The addition of N-vinylpyrrolidone in this invention can improve the stability of the drilling fluid system. The pyrrolidone ring it contains has strong polarity and hydrogen bonding, which can enhance the combination of molecular chains and water molecules, increase the hydration degree of clay particles, and inhibit shale hydration dispersion, thus helping to maintain wellbore stability.

[0025] 5. The rheology modifier of the present invention contains a variety of functional groups such as carboxyl groups and sulfonic acid groups in its molecular chain. It can regulate the degree of stretching of the viscosity reducer molecular chain through appropriate electrostatic repulsion, avoid excessive entanglement of the molecular chain, and at the same time help regulate the charge distribution on the surface of clay particles, further inhibiting agglomeration.

[0026] 6. The rheology modifier of the present invention can react with CO2 and HCO3 produced by CO2 dissolving in water. - CO3 2- Ions form competitive adsorption, which reduces the damage to clay dispersion caused by CO2 and acid radical ions by occupying active sites on the surface of clay particles, ensuring that the drilling fluid can maintain stable rheological properties even in polluted environments; at the same time, the polar groups in the molecular chain have good thermal stability, and can maintain pH response performance and regulation effect under high temperature drilling conditions.

[0027] 7. The raw material composition and preparation method of the present invention work together to form a synergistic effect: the ratio of each monomer and the control of reaction conditions directly affect the distribution of pH-sensitive groups and functional groups in the molecular chain, thereby determining the response sensitivity and regulation efficiency of the regulator; any substitution of raw materials or unsuitable process parameters will lead to a decrease in pH response performance or a weakening of rheological regulation effect, making it impossible to achieve efficient treatment of CO2-contaminated drilling fluid. Detailed Implementation

[0028] The present invention will be further described below through specific embodiments, but is not limited thereto.

[0029] Unless otherwise specified, the experimental methods described in the examples are conventional methods; the reagents and materials used are commercially available unless otherwise specified.

[0030] Example 1

[0031] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids includes the following steps:

[0032] (1) 7.2g acrylic acid, 20.7g 2-acrylamide-2-methylpropanesulfonic acid, 11.14g N-vinylpyrrolidone, 18.5g ethyl 3-(N,N-dimethylamino)acrylate and 120g deionized water were added to a three-bottom round-mouth flask and stirred to obtain a monomer mixture.

[0033] (2) Add 20% sodium hydroxide aqueous solution to the above monomer mixture to adjust the pH of the system to 8; then heat to 70°C in a water bath, purge with nitrogen for 30 min, and then add an initiator aqueous solution (the initiator aqueous solution is obtained by mixing 0.5 g azobisisobutylamidine hydrochloride and 15 g deionized water evenly), with a dropping rate of 1 drop / s; after the dropping is completed, stir and react for 4 h at 70°C under nitrogen protection. After the reaction is completed, the product obtained is a pH-responsive flow modulator suitable for CO2-polluted drilling fluid.

[0034] Example 2

[0035] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that the amount of ethyl 3-(N,N-dimethylamino)acrylate used in step (1) is 20g; the other steps and conditions are the same as in Example 1.

[0036] Example 3

[0037] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that the amount of 2-acrylamide-2-methylpropanesulfonic acid used in step (1) is 25g; the other steps and conditions are the same as in Example 1.

[0038] Example 4

[0039] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluid is described in Example 1, except that: the amount of N-vinylpyrrolidone used in step (1) is 15g; other steps and conditions are the same as in Example 1.

[0040] Example 5

[0041] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that the amount of acrylic acid used in step (1) is 10g; the other steps and conditions are the same as in Example 1.

[0042] Example 6

[0043] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that: the amount of azobisisobutylamidine hydrochloride used in step (2) is 0.1g; other steps and conditions are the same as in Example 1.

[0044] Example 7

[0045] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids includes the following steps:

[0046] (1) Add 5g acrylic acid, 10g 2-acrylamide-2-methylpropanesulfonic acid, 5g N-vinylpyrrolidone, 10g ethyl 3-(N,N-dimethylamino)acrylate and 120g deionized water to a three-bottom round-mouth flask and stir to obtain a monomer mixture.

[0047] (2) Add 20% sodium hydroxide aqueous solution to the above monomer mixture to adjust the pH of the system to 8; then heat to 70°C in a water bath, purge with nitrogen for 30 min, and then add an initiator aqueous solution (the initiator aqueous solution is obtained by mixing 0.5 g azobisisobutylamidine hydrochloride and 15 g deionized water evenly), with a dropping rate of 1 drop / s; after the dropping is completed, stir and react for 4 h at 70°C under nitrogen protection. After the reaction is completed, the product obtained is a pH-responsive flow modulator suitable for CO2-polluted drilling fluid.

[0048] Example 8

[0049] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids includes the following steps:

[0050] (1) Add 10g of acrylic acid, 30g of 2-acrylamide-2-methylpropanesulfonic acid, 20g of N-vinylpyrrolidone, 20g of ethyl 3-(N,N-dimethylamino)acrylate and 120g of deionized water to a three-bottom round-mouth flask and stir to obtain a monomer mixture.

[0051] (2) Add 20% sodium hydroxide aqueous solution to the above monomer mixture to adjust the pH of the system to 8; then heat to 70°C in a water bath, purge with nitrogen for 30 min, and then add an initiator aqueous solution (the initiator aqueous solution is obtained by mixing 0.5 g azobisisobutylamidine hydrochloride and 15 g deionized water evenly), with a dropping rate of 1 drop / s; after the dropping is completed, stir and react for 4 h at 70°C under nitrogen protection. After the reaction is completed, the product obtained is a pH-responsive flow modulator suitable for CO2-polluted drilling fluid.

[0052] Example 9

[0053] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that 2-(diethylamino)methacrylate (DMAEMA) is used instead of 3-(N,N-dimethylamino)acrylate in step (1).

[0054] Example 10

[0055] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 2, except that 2-(diethylamino)methacrylate (DMAEMA) is used instead of 3-(N,N-dimethylamino)acrylate in step (1).

[0056] Comparative Example 1

[0057] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that 2-acrylamide-2-methylpropanesulfonic acid is replaced with maleic anhydride in step (1); the other steps and conditions are the same as in Example 1.

[0058] Comparative Example 2

[0059] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that 2-acrylamide-2-methylpropanesulfonic acid is not added in step (1).

[0060] Comparative Example 3

[0061] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that in step (1), ethyl 3-(N,N-dimethylamino)acrylate is replaced with dimethyldiallylammonium chloride; other steps and conditions are the same as in Example 1.

[0062] Comparative Example 4

[0063] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluids, as described in Example 1, except that in step (1), ethyl 3-(N,N-dimethylamino)acrylate is replaced with N-(3-aminopropyl)methacrylamide; other steps and conditions are the same as in Example 1.

[0064] Comparative Example 5

[0065] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that ethyl 3-(N,N-dimethylamino)acrylate is not added in step (1).

[0066] Comparative Example 6

[0067] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluid is described in Example 1, except that N-vinylpyrrolidone is replaced with sodium p-styrene sulfonate in step (1); the other steps and conditions are the same as in Example 1.

[0068] Comparative Example 7

[0069] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluid is described in Example 1, except that N-vinylpyrrolidone is not added in step (1).

[0070] Comparative Example 8

[0071] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that in step (2), azobisisobutylamidine hydrochloride is replaced with ammonium persulfate; other steps and conditions are the same as in Example 1.

[0072] Comparative Example 9

[0073] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is described in Example 1, except that the reaction time in step (2) is 6 hours; other steps and conditions are the same as in Example 1.

[0074] Comparative Example 10

[0075] A method for preparing a pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluid is as described in Example 1, except that: pH is not adjusted in step (2); other steps and conditions are the same as in Example 1.

[0076] Experimental Example 1

[0077] The rheology, filtration loss, and dispersibility of the flow modifiers prepared in the examples and comparative examples were tested.

[0078] (1) Sample preparation:

[0079] Preparation of the base slurry: First, add 520g of bentonite and 18.2g of sodium carbonate to 13000mL of water, and then stir for 24h to obtain the drilling fluid base slurry.

[0080] Preparation of CO2-contaminated base slurry: The flow pattern modifiers prepared in the above examples and comparative examples were added to the prepared base slurry at a rate of 1 wt%. The slurry was then placed in an aging tank and CO2 gas (5 MPa, 1 h) was introduced into the aging tank to obtain CO2-contaminated base slurry containing the flow pattern modifier. CO2-contaminated base slurry without the added flow pattern modifier was used as a comparison.

[0081] Preparation of base slurries with different pH values: 10 wt% hydrochloric acid solution or 30 wt% sodium hydroxide solution was added to the prepared base slurry to adjust the pH to 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5 and 14 respectively. Then the flow pattern regulator prepared in Example 1 was added at a rate of 1 wt%.

[0082] (2) Test method:

[0083] The rheological parameters (AV, PV, and YP) of the samples before and after aging were measured using a ZNN-D6B electronic six-speed rotational viscometer; the FL of the samples before and after aging was determined using a ZNSJ-5A medium-pressure filtration loss meter at 0.69 MPa. API Filtration loss; aging conditions were aging at 200℃ for 16 hours.

[0084] The test results are shown in Table 1-3.

[0085] Table 1. Rheological and filtration properties of the base slurry with added flow conditioner at room temperature.

[0086]

[0087] Table 2. Rheological and filtration properties of flow pattern regulators under aging conditions at 200℃

[0088]

[0089] Table 3. Rheological and filtration properties of Example 1 slurries at different pH levels (room temperature)

[0090]

[0091] As can be seen from the data in Tables 1-3, the pH-responsive rheology modifier prepared by this invention can effectively reduce the viscosity of the base slurry and decrease filtration loss in a CO2-polluted environment. Furthermore, it maintains stable regulatory performance even after high-temperature aging, demonstrating excellent resistance to CO2 pollution and temperature resistance. Moreover, it maintains its expected effect under different pH conditions.

[0092] In summary, this invention is a pH-responsive rheology modifier for CO2-contaminated drilling fluids, which can meet the rheological control requirements of drilling fluids under different CO2 contamination levels and medium-to-high temperature well conditions, providing reliable technical support for safe and efficient drilling in acidic gas reservoirs.

[0093] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, such as adjusting the ratio of each monomer, optimizing the reaction temperature and time, etc. These simple modifications all fall within the protection scope of the present invention.

[0094] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids, characterized in that, It is prepared from the following raw materials in parts by weight: 5-10 parts acrylic acid, 10-20 parts pH-responsive monomer, 10-30 parts 2-acrylamide-2-methylpropanesulfonic acid, 5-20 parts N-vinylpyrrolidone, 0.1-1 parts initiator, and 100-200 parts water.

2. The pH-responsive flow pattern regulator for CO2-contaminated drilling fluids according to claim 1, characterized in that, The pH-responsive flow pattern modifier suitable for CO2-contaminated drilling fluid is prepared from the following raw materials in parts by weight: 6-8 parts acrylic acid, 15-20 parts pH-responsive monomer, 15-30 parts 2-acrylamide-2-methylpropanesulfonic acid, 10-15 parts N-vinylpyrrolidone, 0.2-0.6 parts initiator, and 100-150 parts water.

3. The pH-responsive flow pattern regulator for CO2-contaminated drilling fluids according to claim 1, characterized in that, The pH-responsive flow pattern modifier suitable for CO2-contaminated drilling fluids is prepared from the following raw materials in parts by weight: 7.2 parts acrylic acid, 18.5 parts pH-responsive monomer, 20.7 parts 2-acrylamide-2-methylpropanesulfonic acid, 11.14 parts N-vinylpyrrolidone, 0.5 parts initiator, and 120 parts water.

4. The pH-responsive flow pattern regulator for CO2-contaminated drilling fluids according to claim 1, characterized in that, The pH-responsive monomer is ethyl 2-(diethylamino)methacrylate and / or ethyl 3-(N,N-dimethylamino)acrylate.

5. The pH-responsive flow pattern regulator for CO2-contaminated drilling fluids according to claim 1, characterized in that, The initiator is azobisisobutylamidine hydrochloride.

6. The method for preparing the pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids according to any one of claims 1-5, characterized in that, The steps include: dispersing acrylic acid, pH-responsive monomer, 2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone in deionized water to obtain a monomer mixture; adjusting the pH of the monomer mixture to 7-9, adding an initiator, and reacting to obtain a pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids.

7. The preparation method of the pH-responsive flow pattern regulator suitable for CO2-polluted drilling fluids according to claim 6, characterized in that, Adjust the pH to 7-9 using a 20-30% sodium hydroxide aqueous solution.

8. The method for preparing the pH-responsive flow pattern regulator for CO2-contaminated drilling fluids according to claim 6, characterized in that, The initiator is added to the system in the form of an aqueous initiator solution, wherein the mass ratio of initiator to deionized water in the aqueous initiator solution is 0.1-1:15; before adding the initiator, a protective gas is introduced into the system to remove oxygen for 20-40 minutes, wherein the protective gas is nitrogen or argon.

9. The method for preparing the pH-responsive flow pattern regulator suitable for CO2-contaminated drilling fluids according to claim 6, characterized in that, The reaction is carried out at a temperature of 65-75℃ for 3-5 hours under the protection of a protective gas and with stirring. The protective gas is nitrogen or argon.

10. The application of the pH-responsive flow pattern regulator for CO2-contaminated drilling fluids according to any one of claims 1-5, characterized in that, As a flow pattern modifier, it is used in CO2-contaminated drilling fluids to reduce drilling fluid viscosity, shear stress, and filtration loss.

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