Application of hyperbranched zwitterionic polymer in high temperature and high salinity drilling fluid

Abstract

The application belongs to the technical field of oil field chemistry, and particularly relates to application of a hyperbranched zwitterionic polymer in a high-temperature and high-salt drilling fluid. The hyperbranched zwitterionic polymer is prepared by a Michael addition reaction of polyethyleneimine and a monomer containing a double bond and a sulfonic acid group which is neutralized by alkali; the polymer has a hyperbranched structure, and amine groups from the polyethyleneimine and sulfonic acid groups from the monomer form zwitterionic characteristics of an inner salt structure; the hyperbranched zwitterionic polymer is used as an inhibitor and viscosity reducer of the drilling fluid. In the hyperbranched zwitterionic polymer, the salt resistance and high-temperature stability of the polymer are enhanced by introducing the sulfonate group; the polymer is endowed with low viscosity and high adsorption capacity by the hyperbranched structure, and can effectively reduce the viscosity of the drilling fluid and inhibit clay hydration; the zwitterionic characteristics stabilize clay particles through electrostatic interaction, and optimize the rheological properties of the drilling fluid.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to the application of a hyperbranched zwitterionic polymer in high-temperature, high-salt drilling fluids. Background Technology

[0002] With the continuous deepening of oil exploration and development, drilling operations face increasingly complex downhole environments, especially deep wells, ultra-deep wells, and high-temperature, high-pressure (temperature ≥150℃, pressure ≥70 MPa) formations, which place higher demands on drilling fluid performance. As the "blood" of drilling engineering, the performance of drilling fluid directly affects drilling efficiency, wellbore stability, and reservoir protection. Among these, drilling fluid treatment agents, as core components for regulating drilling fluid performance, have become a research focus due to their temperature and salt resistance, inhibition properties, and rheological control capabilities. However, traditional treatment agents are prone to molecular chain breakage or functional group failure in high-temperature, high-salt environments, leading to a sharp decline in performance and making it difficult to meet the needs of complex formations. Therefore, developing novel treatment agents that combine temperature and salt resistance, strong inhibition properties, and effective regulation of drilling fluid rheological properties is of great significance.

[0003] Polymer-based treatment agents are widely used in drilling fluids due to their highly designable molecular structures and diverse functions. In existing technologies, polymer filtration loss reducers mainly improve temperature and salt resistance by introducing rigid backbones, large-volume side groups, or hydrolysis-resistant groups. For example, Chinese patent CN108219759A discloses a method for preparing a branched water-based drilling fluid filtration loss reducer. This method involves oxidizing polyethyleneimine with a cerium-containing compound to generate free radicals, which then initiate the polymerization of monomers such as acrylamide and vinylpyrrolidone to form a branched polymer. This polymer significantly improves the dispersion stability of clay particles due to its branched structure and the synergistic effect of multiple functional groups. However, its synthesis requires a redox initiation system, making the process relatively complex, and it demands high polymerization activity from the monomers. In addition, Chinese patent CN113122194A proposes a pH-responsive flow pattern regulator, which is prepared by the reaction of polyethyleneimine and methyl methacrylate. It can reversibly adjust the flow pattern of drilling fluid according to pH changes, but its function is mainly focused on flow pattern control, and its ability to inhibit clay hydration and improve salt tolerance is limited.

[0004] Against this backdrop, zwitterionic polymers have attracted widespread attention due to their unique molecular structure. Zwitterionic polymers carry both positive and negative charges, enabling them to bind tightly to clay particles through electrostatic interactions, effectively inhibiting clay hydration and swelling. Furthermore, their hydrophilic-hydrophobic balance can optimize the rheological properties of drilling fluids. However, existing zwitterionic polymers still have the following shortcomings: firstly, the synthesis process is complex, with cumbersome steps in the preparation and purification of functional monomers, increasing costs; secondly, the molecular weight is difficult to control precisely, leading to poor solubility and stability; and thirdly, in high-salt environments, the charge shielding effect of some zwitterionic polymers is significant, weakening their interaction with clay.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing conventional drilling fluid treatment agents (such as linear polymers or ordinary zwitterionic polymers), such as insufficient temperature and salt resistance, limited inhibition, and contradictory rheological regulation, by providing a hyperbranched zwitterionic polymer for use in high-temperature and high-salt drilling fluids.

[0007] To overcome the shortcomings of the prior art, the present invention provides the following technical solution:

[0008] The application of a hyperbranched zwitterionic polymer in high-temperature, high-salt drilling fluids, wherein the hyperbranched zwitterionic polymer is prepared by a Michael addition reaction of polyethyleneimine with a monomer containing double bonds and sulfonic acid groups that has been neutralized by alkali; the polymer has a hyperbranched structure, and the zwitterionic properties of the amino groups from polyethyleneimine and the sulfonic acid groups from the monomer forming an inner salt structure; the hyperbranched zwitterionic polymer is used as an inhibitor and viscosity reducer for drilling fluids.

[0009] Furthermore, the hyperbranched zwitterionic polymer is added to the drilling fluid at an amount of 0.1% to 5% of the total mass of the drilling fluid.

[0010] Furthermore, the applicable environment for the high-temperature, high-salt drilling fluid is a temperature ≥150℃ and a salinity ≥1×10⁻⁶. 4 mg / L.

[0011] Furthermore, the high-temperature, high-salt drilling fluid is a water-based drilling fluid, an oil-based drilling fluid, or a synthetic-based drilling fluid.

[0012] Furthermore, when the hyperbranched zwitterionic polymer is applied to high-temperature and high-salt drilling fluid, the viscosity reduction rate of the drilling fluid after hot rolling aging at 160°C for 16 hours is ≥20%, and the clay inhibition rate is ≥75%.

[0013] Furthermore, the molecular weight of the polyethyleneimine is 300–70,000 g / mol; and the molecule contains primary amine, secondary amine and tertiary amine; wherein the content of primary amine is 20–50%; the content of secondary amine is 30–50% and the content of tertiary amine is 20–35%.

[0014] Furthermore, the monomer containing double bonds and sulfonic acid groups is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium vinyl sulfonate, sodium styrene sulfonate, and sodium allyl sulfonate.

[0015] Furthermore, the mass ratio of the polyethyleneimine to the monomer containing double bonds and sulfonic acid groups is 1:(0.2-5).

[0016] Furthermore, the alkali is selected from at least one or a combination of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate.

[0017] Furthermore, the preparation method of the hyperbranched zwitterionic polymer adapted to the application includes the following steps:

[0018] S1. Under conditions of 0-5℃, the monomer containing double bonds and sulfonic acid groups is neutralized with alkali, and the pH is adjusted to 7-10 to obtain a neutralized monomer solution.

[0019] S2. Under conditions of 0 to 15°C, the monomer solution obtained in step S1 is slowly added dropwise to the aqueous solution of polyethyleneimine. After the addition is complete, the mixture is stirred for 0.5 to 4 hours.

[0020] S3. Then, the temperature is raised to 20~80℃ and the reaction continues for 0.5~12h. After the reaction is completed, a hyperbranched zwitterionic polymer solution is obtained.

[0021] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0022] ① In the application of the hyperbranched zwitterionic polymer provided by this invention in high-temperature and high-salt drilling fluids, the salt resistance and high-temperature stability of the polymer are enhanced by introducing sulfonate groups; the hyperbranched structure endows the polymer with low viscosity and high adsorption capacity, which can effectively reduce the viscosity of drilling fluid and inhibit clay hydration; the zwitterionic properties stabilize clay particles through electrostatic interaction and optimize the rheological properties of drilling fluid.

[0023] ② The application of the hyperbranched zwitterionic polymer provided by this invention in high-temperature and high-salt drilling fluids offers a new approach to the design of drilling fluid treatment agents. It is particularly suitable for drilling operations under harsh conditions such as high temperature and high salinity, and has broad application prospects. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0025] Figure 1 Infrared spectra of hyperbranched zwitterionic polymers for structural characterization;

[0026] Figure 2 Gel permeation chromatography (GPC) molecular weight and distribution of hyperbranched zwitterionic polymers. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. 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. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0028] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0029] This invention provides an application of a hyperbranched zwitterionic polymer in high-temperature, high-salt drilling fluids. The hyperbranched zwitterionic polymer is prepared by a Michael addition reaction of polyethyleneimine with a monomer containing double bonds and sulfonic acid groups that has been neutralized by alkali. The polymer has a hyperbranched structure, and the zwitterionic properties of the amino groups from polyethyleneimine and the sulfonic acid groups from the monomer forming an inner salt structure are described. The hyperbranched zwitterionic polymer is used as an inhibitor and viscosity reducer for drilling fluids.

[0030] In the aforementioned hyperbranched zwitterionic polymer, as a preferred embodiment, the amount of the hyperbranched zwitterionic polymer added to the drilling fluid is 0.1% to 5% of the total mass of the drilling fluid; the applicable environment for the high-temperature, high-salinity drilling fluid is a temperature ≥150℃ and a salinity ≥1×10⁻⁶. 4mg / L. Preferably, the high-temperature, high-salt drilling fluid is a water-based, oil-based, or synthetic-based drilling fluid. More preferably, after the hyperbranched zwitterionic polymer is applied to the high-temperature, high-salt drilling fluid, the viscosity reduction rate of the drilling fluid after hot rolling aging at 160°C for 16 hours is ≥20%, and the clay inhibition rate is ≥75%.

[0031] In the above applications, as a preferred embodiment, the molecular weight of the polyethyleneimine is 300–70,000 g / mol, preferably 500–30,000 g / mol. The polyethyleneimine contains primary, secondary, and tertiary amines; the primary amine content is 20–50%; the secondary amine content is 30–50%; and the tertiary amine content is 20–35%.

[0032] In the above applications, as a preferred embodiment, the monomer containing double bonds and sulfonic acid groups is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sodium vinyl sulfonate, sodium styrene sulfonate, and sodium allyl sulfonate. Preferably, the monomer containing double bonds and sulfonic acid groups is 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0033] In the above applications, as a preferred embodiment, the mass ratio of the polyethyleneimine to the monomer containing double bonds and sulfonic acid groups is 1:(0.2-5), preferably 1:(0.3-4).

[0034] In the above applications, as a preferred embodiment, the alkali is selected from at least one or a combination of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate.

[0035] Hyperbranched polymers, due to their highly branched three-dimensional structure and abundant terminal functional groups, exhibit excellent solubility, low viscosity, and high reactivity, making them a research hotspot in drilling fluid treatment agents. The hyperbranched structure enhances molecular rigidity and reduces chain coiling at high temperatures, thereby improving temperature resistance; simultaneously, its multifunctional characteristics provide more adsorption sites, enhancing the interaction with clay particles. Polyethyleneimine (PEI), a typical hyperbranched polymer, contains a large number of primary, secondary, and tertiary amine groups. Functional groups can be introduced through chemical modification to endow the polymer with specific properties. For example, introducing sulfonate groups into the PEI backbone can significantly improve its salt resistance and high-temperature stability, while zwitterionic design can further optimize its inhibition and rheological regulation capabilities.

[0036] Using polyethyleneimine (PEI) as a backbone, sulfonate groups of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are introduced into the PEI molecule via a Michael addition reaction, forming a zwitterionic polymer with a hyperbranched structure. Specifically, after neutralization with NaOH, the double bonds of AMPS undergo a Michael addition reaction with the amino groups of PEI, grafting sulfonate groups onto the PEI backbone. This design offers the following advantages: first, the introduction of sulfonate groups enhances the polymer's salt resistance and high-temperature stability; second, the hyperbranched structure endows the polymer with low viscosity and high adsorption capacity, effectively reducing drilling fluid viscosity and inhibiting clay hydration; and third, the zwitterionic properties stabilize clay particles through electrostatic interactions, optimizing the rheological properties of the drilling fluid.

[0037] In the above application, as a preferred embodiment, the preparation method of the hyperbranched zwitterionic polymer includes the following steps:

[0038] S1. Under conditions of 0-5℃, the monomer containing double bonds and sulfonic acid groups is neutralized with alkali, and the pH is adjusted to 7-10 to obtain a neutralized monomer solution.

[0039] S2. Under conditions of 0 to 15°C, the monomer solution obtained in step S1 is slowly added dropwise to the polyethyleneimine aqueous solution at a rate of 2 mL / min. After the addition is complete, the mixture is stirred and reacted for 0.5 to 4 hours.

[0040] S3. Then, the temperature is raised to 20~80℃ and the reaction continues for 0.5~12h. After the reaction is completed, a hyperbranched zwitterionic polymer solution is obtained.

[0041] The equations for the above synthesis steps are shown below:

[0042] ;

[0043] Monomer neutralization: Monomers containing double bonds and sulfonic acid groups (such as 2-acrylamido-2-methylpropanesulfonic acid, AMPS) are neutralized with alkali (NaOH / KOH) to pH 7-10 to form active anionic monomers;

[0044] Michael addition reaction: The neutralized monomer was added dropwise to an aqueous solution of polyethyleneimine (PEI) at low temperature (0–15°C), and the temperature was raised to 20–80°C and the reaction continued for 0.5–12 hours to complete the construction of the hyperbranched structure. The structural characteristics of the hyperbranched zwitterionic polymer are shown in the attached figure. Figure 1 , 2 As shown.

[0045] Hyperbranched framework: With PEI as the core, a three-dimensional network structure is formed through the branching reaction of polyamine groups (primary amines and secondary amines), which endows the polymer with the characteristics of "low viscosity and high adsorption".

[0046] Amphoteric properties: The grafted sulfonic acid group forms an inner salt structure with the amine group of PEI, containing both positively charged amine groups (-NH2, -NH-) and negatively charged sodium sulfonate (-SO3Na), which stabilizes clay particles and regulates drilling fluid rheology through electrostatic interaction.

[0047] Functional group distribution: The terminal sodium sulfonate groups (-SO3Na) and amine groups enhance the "temperature resistance and salt resistance" (sulfonates are resistant to hydrolysis and salt precipitation), solving the high-temperature failure problem of traditional treatment agents.

[0048] In the above application, as a preferred embodiment, in step S2, the mass concentration of the polyethyleneimine aqueous solution is 40%; the polyethyleneimine aqueous solution uses deionized water as a solvent.

[0049] In the above application, as a preferred embodiment, in step S2, the reaction temperature of the stirring reaction is preferably 0-5°C, and the reaction time is preferably 0.5-2 hours; in step S3, the reaction temperature is preferably 30-60°C, and the reaction time is preferably 0.5-6 hours.

[0050] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0051] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are conventional methods, and the materials used are commercially available unless otherwise specified.

[0052] All reagents below should be used in the form they were received in:

[0053] Polyethyleneimine was purchased from Nippon Shokubai, product numbers SP003, SP006, SP012, SP018, SP200, HM2000, and P1050. Sodium hydroxide, potassium hydroxide, and 2-acrylamide-2-methylpropanesulfonic acid were all ordered from Sigma-Aldrich.

[0054] Comparative Example 1: Dissolve 20g of SP006 in 30g of deionized water and stir well.

[0055] Comparative Example 2: Dissolve 20g of SP018 in 30g of deionized water and stir well.

[0056] Comparative Example 3: Dissolve 40g of SP1050 in 10g of deionized water and stir well.

[0057] Example 1: 21 g of NaOH and 94.7 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 108.8 g of AMPS was dissolved in 100 g of deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 20 g of SP003 and 30 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to a polyethyleneimine solution. After the addition was complete, stirring was continued at room temperature for 3 hours. A hyperbranched zwitterionic product 1 with an active ingredient mass fraction of 40% was obtained.

[0058] Example 2: 21 g of NaOH and 94.7 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 108.8 g of AMPS was dissolved in 100 g of deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of SP003 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, stirring was continued at room temperature for 5 hours. A hyperbranched zwitterionic product 2 with an active ingredient mass fraction of 40% was obtained.

[0059] Example 3: 8.4 g of NaOH and 27.9 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 43.5 g of AMPS was dissolved in 50 g of deionized water and slowly added dropwise to the NaOH aqueous solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of SP003 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, stirring was continued at room temperature for 8 hours. A hyperbranched zwitterionic product 3 with an active ingredient mass fraction of 40% was obtained.

[0060] Example 4: 17.6 g of NaOH and 26.5 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 91.4 g of AMPS was dissolved in 137.1 g of deionized water and slowly added dropwise to the NaOH aqueous solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of SP006 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, stirring was continued at room temperature for 2 hours. A hyperbranched zwitterionic product 4 with an active ingredient mass fraction of 40% was obtained.

[0061] Example 5: 10.6 g of NaOH and 15.9 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 54.8 g of AMPS was dissolved in 82.2 g of deionized water and slowly added dropwise to the NaOH aqueous solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of SP012 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, stirring was continued in the ice-water bath for 40 minutes. o Continue stirring at C for 1 hour. A hyperbranched zwitterionic product 5 with an active ingredient mass fraction of 40% is obtained.

[0062] Example 6: 28.2 g of NaOH and 42.3 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 146.2 g of AMPS was dissolved in 219.3 g of deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of SP018 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, stirring was continued in the ice-water bath for 60 minutes. o Continue stirring at C for 2 hours. Obtain hyperbranched zwitterionic product 6 with an active ingredient mass fraction of 40%.

[0063] Example 7: 7.1 g of NaOH and 10.6 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 36.6 g of AMPS was dissolved in 54.8 g of deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of SP200 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, the solution was stirred at 80°C. oContinue stirring at C for 5 hours. A hyperbranched zwitterionic product with an active ingredient mass fraction of 40% is obtained.

[0064] Example 8: 6.9 g of NaOH and 10.4 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 35.9 g of AMPS was dissolved in 53.8 g of deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of HM2000 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, the solution was stirred at 80°C. o Continue stirring at C for 8 hours. Obtain hyperbranched zwitterionic product 8 with an active ingredient mass fraction of 40%.

[0065] Example 9: 17.3 g of NaOH and 26 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 89.6 g of AMPS was dissolved in 134.5 g of deionized water and slowly added dropwise to the NaOH aqueous solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of HM2000 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. o Continue stirring at C for 10 hours. A hyperbranched zwitterionic product 9 with an effective ingredient mass fraction of 40% is obtained.

[0066] Example 10: 27.7 g of NaOH and 41.5 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 143.4 g of AMPS was dissolved in 215.1 g of deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of HM2000 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, the solution was stirred at 80°C. o Continue stirring at C for 2 hours. Obtain hyperbranched zwitterionic product 10 with an active ingredient mass fraction of 40%.

[0067] Example 11: 10.4 g NaOH and 15.6 g deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 53.8 g AMPS was dissolved in 80.7 g deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g P1050 and 60 g deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. o Continue stirring at C for 6 hours. Obtain hyperbranched zwitterionic product 11 with an active ingredient mass fraction of 40%.

[0068] Example 12: 24.2 g of NaOH and 36.3 g of deionized water were added to a 500 ml three-necked flask placed in an ice-water bath and stirred until completely dissolved. 125.5 g of AMPS was dissolved in 188.2 g of deionized water and slowly added dropwise to the NaOH solution. After the addition was complete, stirring was continued in the ice-water bath for 30 minutes. 40 g of P1050 and 60 g of deionized water were added to a 500 ml three-necked flask and stirred until completely dissolved. The neutralized AMPS solution was slowly added dropwise to the polyethyleneimine solution. After the addition was complete, the solution was stirred at 80°C. o Continue stirring at C for 12 hours. This yields a hyperbranched zwitterionic product 12 with an active ingredient mass fraction of 40%.

[0069] Performance testing

[0070] The basic formulation of the drilling fluid is as follows: 300ml 1~3% soil slurry + 0.5~2% caustic soda + 0.5~2% filtration loss reducer + 1~5% sulfonated lignite + 1~5% sulfonated phenolic resin + 0.5~2% lubricant + 7% KCl + 900g barite; density 2.35 g / cm³ 3 .

[0071] Preparation of drilling fluid containing hyperbranched zwitterionic product: 8 grams of the hyperbranched zwitterionic product solution were added to the above drilling fluid, and the mixture was rapidly stirred until a homogeneous dispersion was formed. The drilling fluid was then subjected to a temperature of 160°C. o The hot rolling aging process was carried out at C for 16 hours, and the viscosity before and after hot rolling aging was tested respectively.

[0072] The viscosity reading at 100 rpm was measured using a six-speed viscometer, and the viscosity reduction rate was calculated using the following formula:

[0073] ;

[0074] in This is the reading of the barite dispersion at 100 rpm without any sample added. The reading of the barite dispersion at 100 rpm after the sample was added.

[0075] Preparation of freshwater bentonite slurry: Add 350 mL of distilled water, 1.0 g of sodium bicarbonate, 0.35 g of sodium carbonate, 10 g of drilling fluid test reference soil, and 24.5 g of drilling fluid evaluation soil to two high-speed mixing cups respectively. Mix at high speed for 20 min, stopping twice during the mixing process to scrape off the clay adhering to the cup walls. Seal and cure both cups at room temperature for 24 h, then stir at high speed for 5 min. The Φ of the base slurry... 600 If the reading is ≤16, otherwise adjust the amount of the two types of soil proportionally until the requirement is met.

[0076] Take two portions of base pulp and add 4g of hyperbranched zwitterionic product solution to each while stirring with a glass rod. Stir at high speed for 20 min and cure in a sealed container at room temperature for 24 h. Take the cured sample pulp and stir on a high-speed mixer for 5 min. Test its viscosity at six speeds according to GB / T16783.1. Calculate the pulping inhibition rate using the following formula:

[0077] ;

[0078] The data is shown in Table 1 below:

[0079] Table 1

[0080] ;

[0081] As can be seen from the table above, the pulping inhibition rate of this hyperbranched zwitterionic polymer is comparable to that of its precursor, polyethyleneimine. However, the viscosity of the drilling fluid can be significantly reduced by introducing sulfonate groups through the Michael addition reaction.

[0082] The foregoing has described and evaluated some embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, still fall within the protection scope of the present invention.

Claims

1. The application of a hyperbranched zwitterionic polymer in high-temperature, high-salinity drilling fluids, characterized in that, The hyperbranched zwitterionic polymer is prepared by Michael addition reaction of polyethyleneimine with a monomer containing double bonds and sulfonic acid groups after alkali neutralization. The polymer has a hyperbranched structure, exhibiting zwitterionic properties where the amino groups from polyethyleneimine and the sulfonic acid groups from the monomer form an inner salt structure. The hyperbranched zwitterionic polymer is used as an inhibitor and viscosity reducer in drilling fluids. The applicable environment for the high-temperature, high-salt drilling fluid is a temperature ≥150℃ and a salinity ≥1×10⁻⁶. 4 mg / L.

2. The application according to claim 1, characterized in that, The hyperbranched zwitterionic polymer is added to the drilling fluid at a rate of 0.1% to 5% of the total mass of the drilling fluid.

3. The application according to claim 1, characterized in that, The high-temperature, high-salt drilling fluid is a water-based drilling fluid, an oil-based drilling fluid, or a synthetic-based drilling fluid.

4. The application according to claim 1, characterized in that, When the hyperbranched zwitterionic polymer is applied to high-temperature and high-salt drilling fluid, the viscosity reduction rate of the drilling fluid after hot rolling aging at 160℃ for 16 hours is ≥20%, and the inhibition rate of clay slurry formation is ≥75%.

5. The application according to claim 1, characterized in that, The polyethyleneimine has a molecular weight of 300–70,000 g / mol and contains primary, secondary, and tertiary amines; wherein the primary amine content is 20–50%, the secondary amine content is 30–50%, and the tertiary amine content is 20–35%.

6. The application according to claim 1, characterized in that, The monomer containing double bonds and sulfonic acid groups is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium vinyl sulfonate, sodium styrene sulfonate, and sodium allyl sulfonate.

7. The application according to claim 1, characterized in that, The mass ratio of the polyethyleneimine to the monomer containing double bonds and sulfonic acid groups is 1:(0.2-5).

8. The application according to claim 1, characterized in that, The alkali is selected from at least one or a combination of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate.

9. The application according to claim 1, characterized in that, The preparation method of the hyperbranched zwitterionic polymer adapted to the aforementioned application includes the following steps: S1. Under conditions of 0-5℃, the monomer containing double bonds and sulfonic acid groups is neutralized with alkali, and the pH is adjusted to 7-10 to obtain a neutralized monomer solution. S2. Under conditions of 0 to 15°C, the monomer solution obtained in step S1 is slowly added dropwise to the aqueous solution of polyethyleneimine. After the addition is complete, the mixture is stirred and reacted for 0.5 to 4 hours. S3. Then, the temperature is raised to 20~80℃ and the reaction continues for 0.5~12h. After the reaction is completed, a hyperbranched zwitterionic polymer solution is obtained.

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