Pentapolymer and method for preparing same, fluid loss additive and water-based drilling fluid

Abstract

The application provides a five-membered random copolymer, a preparation method thereof, a fluid loss additive and a water-based drilling fluid. The five-membered random copolymer is formed by free radical copolymerization of 2-acrylamido-2-methyl-1-propane sulfonic acid, dimethyl diallyl ammonium chloride, N-vinyl caprolactam, N-alkenyl amide and an alkenyl heterocyclic compound. The application further provides a preparation method of the five-membered random copolymer, a fluid loss additive containing the five-membered random copolymer and a water-based drilling fluid containing the fluid loss additive. The five-membered random copolymer provided by the application has the characteristics of high-temperature resistance and salt resistance as the fluid loss additive, and has a low fluid loss amount in fresh water slurry or salt water.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and in particular to a five-component random copolymer, its preparation method, a filtration loss reducer, and a water-based drilling fluid. Background Technology

[0002] With economic development, the demand for oil and gas resources is becoming increasingly urgent, and oil and gas exploration is continuously expanding into deeper formations, requiring the overcoming of increasingly demanding formation conditions. Drilling fluids play a crucial role in ensuring safe and rapid drilling in deep and ultra-deep wells. However, the rheological and filtration properties of drilling fluids change significantly under high-temperature and high-salt conditions, leading to drastic thickening of the mud cake, increased permeability, and a significant impact on wellbore stability. Therefore, developing high-temperature and salt-resistant filtration reducers for drilling fluids is one of the challenges facing deep and ultra-deep well drilling fluids.

[0003] Traditional fluid loss reducers mainly consist of lignite-based, modified lignin-based, and resin-based agents. While these are widely available and inexpensive, they suffer from viscosity loss under high temperature and pressure conditions, leading to poor drilling fluid rheology. They are also prone to decomposition at higher formation temperatures and are easily converted into calcium. 2+ Mg 2+ Pollution and other issues create complex downhole conditions, limiting their practical application.

[0004] Currently, acrylamide-based filtration loss reducers are prone to polymer chain degradation and severe desorption problems at high temperatures, resulting in unsatisfactory filtration loss reduction performance under high-temperature conditions. Their temperature and salt resistance still cannot meet the actual needs of drilling fluids in deep and ultra-deep wells. Therefore, it is urgent to develop new polymer filtration loss reducers with better performance. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a five-component random copolymer, its preparation method, a filtration loss reducer, and a water-based drilling fluid. This five-component random copolymer, as a filtration loss reducer, exhibits high temperature and salt resistance, and demonstrates low filtration loss in both freshwater slurry and brine.

[0006] To achieve the above objectives, the present invention provides a five-component random copolymer, which is formed by free radical copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid, N-alkenylamide, dimethyldiallylammonium chloride, N-vinylcaprolactam and alkenyl heterocyclic compound; wherein the molar ratio of N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyldiallylammonium chloride, N-vinylcaprolactam and alkenyl heterocyclic compound is (6-8):(1.7-4):(0.5-2):(1-2):(1-2).

[0007] The side chains of the five-component random copolymer provided by this invention have sulfonic acid groups (which can be provided by 2-acrylamido-2-methyl-1-propanesulfonic acid), quaternary ammonium salt cationic groups (which can be provided by dimethyldiallylammonium chloride), and heterocyclic groups (which can be provided by alkenyl heterocyclic compounds). The sulfonic acid groups on the side chains of this polymer molecule can provide good hydration and are insensitive to cations, thus exhibiting good salt resistance and enhancing the dispersion stability of bentonite. The quaternary ammonium salt cationic groups on the side chains can generate strong adsorption with bentonite, enabling the polymer to adsorb with bentonite and, due to the anti-polyelectrolyte effect, making the polymer chains more extended and improving its salt resistance. The heterocyclic groups on the side chains not only enhance the adsorption capacity with bentonite but also, due to their greater steric hindrance, improve the polymer's temperature resistance. The N-alkenyl amide monomer has better resistance to high-temperature degradation than amide groups such as acrylamide, and even after decomposition, it can produce amine groups that adsorb with clay. Therefore, the five-component random copolymer in this invention, as an aqueous polymer, has the effect of resisting high temperature and high salt, which can improve the aggregation state of bentonite, making bentonite have better hydration and dispersion stability, and clay particles themselves have less aggregation, resulting in a denser filter cake and lower filtration loss.

[0008] In some specific implementations, the structure of the above-mentioned five-component random copolymer can be represented as follows:

[0009]

[0010] Wherein, R1 is H or an alkyl group having 1-8 carbon atoms, R2 is H or an alkyl group having 1-8 carbon atoms, and R3 is an aromatic heterocycle. m:n:p:q:r can be (6-8):(2-4):(0.5-2):(1-2):(1-2).

[0011] In the structure of the aforementioned five-component random copolymer, the dimethyl diallyl ammonium chloride can form a five-component structure through cyclization polymerization during the polymerization process. During polymerization, the allyl group in the dimethyl diallyl ammonium chloride can undergo chain transfer. By controlling the amount of dimethyl diallyl ammonium chloride monomer added, the monomer conversion rate and the molecular weight of the five-component random copolymer can be controlled.

[0012] The N-alkenylamide monomer used in this invention has good chemical stability. Even when dehydrogenated at high temperatures, it retains the amine group to generate adsorption force on clay. It can also avoid the problem that traditional acrylamide and N-substituted alkanes hydrolyze into carboxylic acids at high temperatures, causing polymer precipitation and coagulation, which in turn affects their filtration performance.

[0013] Specifically, the structural formula of the N-alkenylamide can be:

[0014]

[0015] Wherein, R1 is H or an alkyl group having 1-8 carbon atoms, and R2 is H or an alkyl group having 1-8 carbon atoms. Preferably, R1 is H or a methyl group, and R2 is H or a methyl group.

[0016] In the above-mentioned five-component random copolymer, the N-alkenylamide includes one or more of N-vinylformamide (CAS: 13162-05-5), N-vinylacetamide, and N-methyl-N-vinylacetamide.

[0017] The rigid ring structure in the alkenyl heterocyclic compound monomer used in this invention improves the temperature resistance of the polymer molecular chain. At the same time, the nitrogen-containing heterocycle can enhance the adsorption interaction between the polymer and clay, thereby effectively forming a hydration layer on the clay surface, giving the clay particles good dispersion stability and showing low filtration loss in both fresh and salt water.

[0018] In the aforementioned five-component random copolymer, the alkenyl heterocyclic compound includes one or more combinations of N-vinylimidazole, vinylpyridine, N-vinylcarbazole, and 4-methyl-5-vinylthiazole, for example, a combination of vinylimidazole and vinylcaprolactam. In some specific embodiments, the alkenyl heterocyclic compound may include one or more combinations of N-vinylimidazole, N-vinylcarbazole, and vinylpyridine.

[0019] The structural formula of N-vinylimidazol is:

[0020] The structural formula of vinylpyridine is:

[0021] The structural formula of N-vinylcarbazole is:

[0022] The structural formula of 4-methyl-5-vinylthiazole is:

[0023] In the above-mentioned five-component random copolymer, the molar ratio of N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyl diallyl ammonium chloride, N-vinylcaprolactam and alkenyl heterocyclic compound is (6-8):(1.7-4):(0.5-2):(1-2):(1-2), and may further be (6-8):(2-4):(0.5-2):(1-2):(1-2). This invention, by controlling the ratio of N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyldiallyl ammonium chloride, N-vinylcaprolactam, and alkenyl heterocyclic compounds, ensures a high monomer conversion rate (up to 95% or more) during the synthesis of the five-component random copolymer, allowing for sufficient reaction between monomers and maintaining the initial monomer molar ratio, thereby obtaining a five-component random copolymer with a high molecular weight. Furthermore, drilling fluids made from the five-component random copolymer obtained within the above-mentioned ratio range exhibit better performance indicators, and the functions of each monomer are fully utilized. In some specific embodiments, the above-mentioned five-component random copolymer can be formed by free radical copolymerization of one of N-vinylimidazolium, N-vinylcarbazole, and vinylpyridine with 2-acrylamido-2-methyl-1-propanesulfonic acid, N-methyl-N-vinylacetamide, dimethyldiallyl ammonium chloride, and N-vinylcaprolactam.

[0024] In some specific embodiments, the N-alkenylamide in the monomer can be 6-8 parts in molar fractions, for example, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, etc., and a range with any two of the above specific values ​​as endpoints;

[0025] The 2-acrylamido-2-methyl-1-propanesulfonic acid can be 1.7-4 parts, for example, 1.7 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, etc., and a range with any two of the above specific values ​​as endpoints;

[0026] The dimethyl diallyl ammonium chloride can be 0.5-2 parts, for example 0.5-1 part, or specific values ​​such as 0.5 parts, 1 part, 1.5 parts, 2 parts, etc., and a range with any two of the above specific values ​​as endpoints;

[0027] The N-vinylcaprolactam can be 1-2 parts, for example, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts, etc., and a range with any two of the above specific values ​​as endpoints;

[0028] The alkenyl heterocyclic compound can be 1-2 parts, for example, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts, etc., and a range with any two of the above specific values ​​as endpoints.

[0029] In the aforementioned pentagonal random copolymer, the weight-average molecular weight is 247 kDa-366 kDa. In some specific embodiments, the weight-average molecular weight of the pentagonal random copolymer can be a specific value such as 247 kDa, 250 kDa, 260 kDa, 270 kDa, 280 kDa, 290 kDa, 300 kDa, 310 kDa, 320 kDa, 330 kDa, 340 kDa, 350 kDa, 360 kDa, 366 kDa, or a range with any two of the above specific values ​​as endpoints.

[0030] The present invention also provides a method for preparing the above-mentioned five-component random copolymer, comprising:

[0031] The monomer is mixed with water to form a reaction solution, and an initiator is added in an oxygen-free protective atmosphere to carry out a free radical copolymerization reaction to obtain a five-member random copolymer.

[0032] The monomers include N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyldiallylammonium chloride, N-vinylcaprolactam and alkenyl heterocyclic compounds;

[0033] The free radical copolymerization reaction temperature is greater than 70℃ and less than or equal to 90℃, and the free radical copolymerization reaction time is 2-10h.

[0034] In some specific embodiments, the preparation method may employ solution polymerization. The mass of the monomer may be 20%-40% of the mass of the reaction solution.

[0035] In the above preparation method, the initiator may include one of potassium persulfate, ammonium persulfate, ammonium persulfate / sodium bisulfite, azobisisobutyronitrile, azobisisobutyronitrile, azobisisobutyramidoline hydrochloride, and 2,2-azobis(2-methylpropanediamine) hydrochloride. In some specific embodiments, the initiator may include azobisisobutyronitrile or azobisisobutyramidoline hydrochloride.

[0036] In the above preparation method, the mass of the initiator is generally controlled to be 0.1%-1% of the total monomer mass. Specifically, the mass of the initiator can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 1.0% of the total monomer mass, or a range with any two of the above specific values ​​as endpoints. In some specific embodiments, the mass of the initiator can be 0.7%-0.85%.

[0037] In the above preparation method, the pH value of the reaction solution is 6-9. In some specific embodiments, the pH value of the reaction solution can be adjusted using an acid-base adjuster such as sodium hydroxide.

[0038] In the above preparation method, all monomers can be added simultaneously, and then the pH of the system can be adjusted; alternatively, a portion of the monomers can be added first, the pH adjusted, and then the remaining monomers added. This invention does not impose any special restrictions on the order of monomer addition and pH adjustment, as long as the pH of the reaction system remains consistent.

[0039] In the above preparation method, the free radical copolymerization reaction temperature is generally greater than 70℃ and less than or equal to 90℃, for example, greater than 70℃ and less than or equal to 75℃, 75℃-90℃, etc. Specifically, the reaction temperature can be specific values ​​such as 70.1℃, 71℃, 72℃, 73℃, 74℃, 75℃, 80℃, 85℃, 90℃, etc., or a range with any two of the above specific values ​​as endpoints.

[0040] In the above preparation method, the free radical copolymerization reaction time is generally 2h-10h, for example 6h-8h. Specifically, the reaction time can be specific values ​​such as 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, and any two of the above specific values ​​as endpoints.

[0041] According to a specific embodiment of the present invention, the preparation method of the above-mentioned five-component random copolymer may specifically include:

[0042] N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyldiallylammonium chloride, N-vinylcaprolactam, and alkenyl heterocyclic compound were mixed in a molar ratio of (6-8):(2-4):(0.5-2):(1-2):(1-2) to form a reaction solution. In an oxygen-free protective atmosphere, an initiator was added to the reaction solution and a free radical copolymerization reaction was carried out at a temperature greater than 70°C and less than or equal to 90°C for 2-10 hours to obtain a five-component random copolymer.

[0043] In some specific embodiments, the oxygen-free protective atmosphere includes nitrogen and / or argon.

[0044] The present invention also provides a filtration loss reducing agent comprising or made from the above-mentioned five-component random copolymer. The filtration loss reducing agent made from the five-component random copolymer provided by the present invention has high temperature resistance (withstanding temperatures up to 200°C) and salt resistance, and can improve the density of the filter cake and reduce filtration loss, making it a novel high-temperature and salt-resistant polymer filtration loss reducing agent.

[0045] This invention also provides a water-based drilling fluid comprising the aforementioned filtration loss reducer. The five-component random copolymer in the aforementioned filtration loss reducer has a strong adsorption effect on components such as clay in the drilling fluid, which can improve the aggregation state and hydration dispersion stability of clay, thereby reducing filtration loss. In some specific embodiments, the water-based drilling fluid includes clay, which may be bentonite, such as sodium bentonite.

[0046] The beneficial effects of this invention include:

[0047] 1. This invention uses N-alkenylamide monomers to synthesize five-component random copolymers. The good chemical stability of N-alkenylamide monomers allows the five-component random copolymers to retain the amine groups to adsorb clays such as bentonite even after degradation at high temperatures. Moreover, it avoids the problem of traditional acrylamides and N-substituted alkanes hydrolyzing into carboxylic acids at high temperatures, which leads to polymer precipitation and coagulation, thus affecting their filtration performance.

[0048] 2. This invention uses alkenyl heterocyclic compound monomers to synthesize five-membered random copolymers. The large rigid ring structure in alkenyl heterocyclic compounds can be used to improve the temperature resistance of polymer molecular chains. At the same time, nitrogen-containing heterocycles can enhance the adsorption interaction between polymer and clay, thereby effectively forming a hydration layer on the clay surface, giving the clay particles good dispersion stability and showing low filtration loss in both fresh and salt water.

[0049] 3. The five-component random copolymer provided by this invention can be used as a high-temperature and salt-resistant filtration loss reducer, and still exhibits good filtration loss reduction capabilities under high-temperature and high-salt conditions. Specifically, water-based drilling fluids containing this filtration loss reducer can maintain low filtration loss in both freshwater and brine slurries after aging at 200°C for 16 hours, with a filtration loss reduction effect superior to commercial samples such as Driscal D and Dristemp. The five-component random copolymer filtration loss reducer provided by this invention can be applied to water-based drilling fluids and is suitable for deep formation oil and gas extraction operations. Attached Figure Description

[0050] Figure 1 The 1H NMR spectrum of the five-component random copolymer and its raw material monomers in Example 1 is shown.

[0051] Figure 2The 1H NMR spectra of the five-membered random copolymers of Examples 1 to 5 are shown.

[0052] Figure 3 The NMR spectra of the copolymers of Comparative Examples 1 to 6 are shown. Detailed Implementation

[0053] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0054] In the following examples and comparative examples, the weight-average molecular weight and molecular weight distribution of the polymers were measured using a Waters 1525 gel permeation chromatograph equipped with a CoMetre 6000LDI pump, a Shodex SB-804HQ column, and a Schambeck SFD GmbH RI2000 differential detector. The polymer samples were prepared as 2 mg / mL solutions.

[0055] In the following examples and comparative examples, the monomer conversion rate is calculated by precipitating and washing the polymer solution obtained from the reaction with acetone, then drying the solid sample to obtain the solid sample. The ratio of the weight of the solid sample to the mass of the monomer in the reaction solution is the monomer conversion rate.

[0056] Example 1

[0057] This embodiment provides a five-component random copolymer, which is prepared from five raw materials: N-methyl-N-vinylacetamide (VMA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC), N-vinylcaprolactam (NVCL), and N-vinylimidazolium (VIM), as well as sodium hydroxide solution and azobisisobutyronitrile. The preparation method is as follows:

[0058] 1. Add 6.21g of 2-acrylamido-2-methyl-1-propanesulfonic acid to 48mL of deionized water, adjust the pH to 7 with 30% NaOH solution, then transfer to a 250mL three-necked flask, add 8.91g of N-methyl-N-vinylacetamide, 2.43g of dimethyldiallylammonium chloride aqueous solution (solute mass is 60% of solution mass), 1.41g of N-vinylimidazolium and 2.1g of N-vinylcaprolactam, and stir thoroughly to obtain a homogeneous reaction solution.

[0059] 2. Sufficient nitrogen gas was introduced into the reaction solution to purge oxygen. A thermometer was added, and the mixture was heated to 75°C while stirring. At this point, 157.5 mg of azobisisobutyronitrile (AIBN) was added, and the reaction was continued with stirring for 6 hours. After the reaction was complete, a pale yellow, viscous five-component random copolymer was obtained. After precipitation and washing in an appropriate amount of acetone, the copolymer was dried in a vacuum drying oven at 60°C and ground to obtain the final copolymer product. This copolymer can be used as a novel high-temperature and salt-resistant polymer filtration loss reducer. The polymer weight-average molecular weight was 247 kDa (GPC, H2O), and the monomer conversion rate was 95.6%.

[0060] The 1H NMR spectra of the polymer and monomer prepared in Example 1 are compared as follows: Figure 1 As shown, M1, M2, M3, M4, and M5 correspond to the 1H NMR spectra of monomers VMA, AMPS, DMDAAC, NVCL, and VIM, respectively. By comparing the olefinic hydrogen peaks of the monomer double bonds, it can be seen that the peak at a chemical shift of 5.5–6.0 ppm is the olefinic hydrogen of the DMDAAC monomer, and the peak at 6.9–7.4 ppm is the olefinic hydrogen peak of VMA. No olefinic hydrogen peaks appeared in the spectrum of Example 1, indicating that the monomer reaction was complete.

[0061] Example 2

[0062] This embodiment provides a five-component random copolymer, which is prepared from five raw materials: N-vinylacetamide (VMA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC), N-vinylcaprolactam (NVCL), and N-vinylimidazolium (VIM), as well as sodium hydroxide solution and azobisisobutyronitrile. The preparation method is as follows:

[0063] 1. Add 6.21g of 2-acrylamido-2-methyl-1-propanesulfonic acid to 48mL of deionized water, adjust the pH to 7 with 30% NaOH solution, then transfer to a 250mL three-necked flask, add 11.88g of N-methyl-N-vinylacetamide, 2.43g of dimethyl diallyl ammonium chloride (60% aqueous solution), 1.41g of N-vinylimidazolium and 2.1g of N-vinylcaprolactam, and stir thoroughly to obtain a homogeneous reaction solution.

[0064] 2. Sufficient nitrogen gas is introduced into the reaction solution to purge oxygen. The mixture is heated to 75°C while stirring. At this point, 180 mg of azobisisobutyronitrile (AIBN) is added, and the reaction is continued with stirring for 6 hours. After the reaction is complete, a pale yellow, viscous five-component random copolymer is obtained. After precipitation and washing in an appropriate amount of acetone, the copolymer is dried in a vacuum drying oven at 60°C and then ground to obtain the final copolymer product. This copolymer can be used as a novel high-temperature and salt-resistant polymer filtration loss reducer. The polymer's weight-average molecular weight is 287 kDa (GPC, H2O), and the monomer conversion rate is approximately 100%.

[0065] Example 3

[0066] This embodiment provides a five-component random copolymer, which is prepared from five raw materials: N-methyl-N-vinylacetamide (VMA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC), N-vinylcaprolactam (NVCL), and N-vinylcarbazole, as well as sodium hydroxide solution and azobisisobutyronitrile. The preparation method is as follows:

[0067] 1. Add 12.42 g of 2-acrylamido-2-methyl-1-propanesulfonic acid to 69 mL of deionized water, adjust the pH to 7 with 30% NaOH solution, then transfer to a 250 mL three-necked flask, add 8.91 g of N-methyl-N-vinylacetamide, 2.43 g of dimethyl diallyl ammonium chloride (60% aqueous solution), 2.89 g of N-vinylcarbazole and 2.1 g of N-vinylcaprolactam, and stir thoroughly to obtain a homogeneous reaction solution.

[0068] 2. Sufficient nitrogen gas was introduced into the reaction solution to purge oxygen. The mixture was heated to 75°C while stirring. At this point, 228 mg of azobisisobutyronitrile (AIBN) was added, and the reaction was continued with stirring for 6 hours. After the reaction was complete, a pale yellow, viscous five-component random copolymer was obtained. After precipitation and washing in an appropriate amount of acetone, the copolymer was dried in a vacuum drying oven at 60°C and then ground to obtain the final copolymer product. This copolymer can be used as a novel high-temperature and salt-resistant polymer for reducing filtration loss. The polymer has a weight-average molecular weight of 366 kDa (GPC, H2O) and a monomer conversion rate of approximately 100%.

[0069] Example 4

[0070] This embodiment provides a five-component random copolymer, which is prepared from five raw materials: N-methyl-N-vinylacetamide (VMA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC), N-vinylcaprolactam (NVCL), and N-vinylimidazolium (VIM), as well as sodium hydroxide solution and azobisisobutyronitrile. The preparation method is as follows:

[0071] 1. Add 12.42 g of 2-acrylamido-2-methyl-1-propanesulfonic acid to 69 mL of deionized water, adjust the pH to 7 with 30% NaOH solution, then transfer to a 250 mL three-necked flask, add 11.88 g of N-methyl-N-vinylacetamide, 2.43 g of dimethyl diallyl ammonium chloride (60% aqueous solution), 1.41 g of N-vinylimidazolium and 2.1 g of N-vinylcaprolactam, and stir thoroughly to obtain a homogeneous reaction solution.

[0072] 2. Sufficient nitrogen gas was introduced into the reaction solution to purge oxygen. A thermometer was added, and the mixture was heated to 75°C while stirring. At this point, 226.8 mg of azobisisobutyronitrile (AIBN) was added, and the reaction was continued with stirring for 6 hours. After the reaction was complete, a pale yellow, viscous five-component random copolymer was obtained. After precipitation and washing in an appropriate amount of acetone, the copolymer was dried in a vacuum drying oven at 60°C and ground to obtain the final copolymer product. This copolymer can be used as a novel high-temperature and salt-resistant polymer filtration loss reducer. The polymer weight-average molecular weight is 352 kDa (GPC, H2O), and the monomer conversion rate is approximately 100%.

[0073] Example 5

[0074] This embodiment provides a five-component random copolymer, which is prepared from five raw materials: N-methyl-N-vinylacetamide (VMA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC), N-vinylcaprolactam (NVCL), vinylpyridine, sodium hydroxide solution, and azobisisobutyronitrile. The preparation method is as follows:

[0075] 1. Add 9.33g of 2-acrylamido-2-methyl-1-propanesulfonic acid to 66mL of deionized water, adjust the pH to 7 with 30% NaOH solution, then transfer to a 250mL three-necked flask, add 11.88g of N-methyl-N-vinylacetamide, 3.66g of dimethyl diallyl ammonium chloride (60% aqueous solution), 1.57g of vinylpyridine and 2.1g of N-vinylcaprolactam, and stir thoroughly to obtain a homogeneous reaction solution.

[0076] 2. Sufficient nitrogen gas was introduced into the reaction solution to purge oxygen. A thermometer was added, and the mixture was heated to 75°C while stirring. At this point, 213 mg of azobisisobutyronitrile (AIBN) was added, and the reaction was continued with stirring for 6 hours. After the reaction was complete, a pale yellow, viscous five-component random copolymer was obtained. After precipitation and washing in an appropriate amount of acetone, the copolymer was dried in a vacuum drying oven at 60°C and ground to obtain the final copolymer product. This copolymer can be used as a novel high-temperature and salt-resistant polymer filtration loss reducer. The polymer weight-average molecular weight is 318 kDa (GPC, H2O), and the monomer conversion rate is approximately 99.4%.

[0077] Figure 2 The NMR spectra of the copolymer products prepared in Examples 1 to 5 are shown. Quantitative analysis using DMF internal standard indicates that the monomer reaction in Examples 1 to 5 was complete and the conversion rate was high.

[0078] Comparative Example 1

[0079] This comparative example provides a method for preparing a polymer using precipitation polymerization. The specific process is as follows:

[0080] In a 100 mL three-necked round-bottom flask, 47 mL of tert-butanol was added, and the temperature was raised to 40 °C. AMPS (4.1 g, 19.8 mmol) was added to the tert-butanol; the AMPS remained suspended and insoluble. Triethylamine, in an equimolar amount of AMPS, was then added, and the AMPS gradually dissolved. After the solution became clear, the pH was adjusted to approximately 8.0 with a 30 wt% NaOH aqueous solution. Subsequently, the remaining four monomers were added in a monomer molar ratio of VMA:AMPS:DMDAAC:NVCL:VIM = 6:2:2:1:1. Argon gas was then introduced to purge oxygen (for 30 min), and the temperature was raised to 60 °C. Azobisisobutyronitrile (AIBN) was added as the initiator (0.9% of the total monomer mass). After stirring for 2 h, the solution began to thicken. The temperature was raised to 69 °C, and the reaction was continued for another 2 h. Then, the temperature was raised to 75 °C, and the reaction was continued for 2 h before the reaction was stopped. The crude product of the reaction is a pale yellow viscous liquid. The final product is obtained by washing, drying and grinding.

[0081] Comparative Example 2

[0082] This comparative example provides a method for preparing a polymer using solution polymerization, the specific process of which is as follows:

[0083] 4.1 g of monomer AMPS was dissolved in a three-necked flask containing 64 mL of water, and the pH was adjusted to approximately 8 using a 30 wt% NaOH aqueous solution. The remaining four monomers were added in a monomer molar ratio of VMA:AMPS:DMDAAC:NVCL:VIM = 6:2:2:1:1, along with chain transfer agent ethanol (approximately 10% of the water content). Argon gas was introduced to purge oxygen (for 30 min), and the temperature was raised to 70 °C. Azobisisobutyronitrile (AIBN) initiator was then added, with the initiator mass being 0.75% of the total monomer mass. The reaction was continued for 2 h to terminate the reaction. After the reaction, the crude product was a pale yellow viscous liquid, which was washed, dried, and ground to obtain the final product.

[0084] Comparative Example 3

[0085] This comparative example provides a method for preparing a polymer, the method comprising:

[0086] Add 10 mL of water to a 100 mL three-necked flask, and dissolve the monomer AMPS in a beaker containing 8 mL of water. Adjust the pH of the AMPS aqueous solution to approximately 8 using a 30% wt NaOH aqueous solution. Add the remaining four monomers to the beaker according to the monomer molar ratio VMA:AMPS:DMDAAC:NVCL:VIM = 6:2:2:1:1. Purge oxygen with argon gas (30 min), raise the temperature in the three-necked flask to 100 °C, add 3 mL of the monomer mixture solution first, then slowly add the remaining monomer solutions and the initiator azobisisobutyrazoline hydrochloride VA-044 dropwise to the three-necked flask simultaneously. The entire mixture should be added over approximately 1 hour. The initiator should account for 1.5% of the total monomer mass. Continue the reaction for 5 hours to complete the reaction. After the reaction, the crude product is a pale yellow viscous liquid. Wash, dry, and grind to obtain the final product.

[0087] Comparative Example 4

[0088] This comparative example provides a method for preparing a polymer, the method comprising:

[0089] Dissolve 2.07 g of monomer AMPS in a three-necked flask containing 35 mL of water. Adjust the pH to approximately 8 using a 30 wt% NaOH aqueous solution. Add the remaining four monomers according to the monomer molar ratio VMA:AMPS:DMDAAC:NVCL:VIM = 6:2:2:1:1. Purge oxygen with argon gas for 30 min. Raise the temperature to 60 °C and add the initiator azobisisobutyrazoline hydrochloride VA-044, with the initiator mass being 1.5% of the total monomer mass. Continue the reaction for 4 h to terminate the reaction. After the reaction is complete, the crude product is a pale yellow viscous liquid. Wash, dry, and grind to obtain the final product.

[0090] Comparative Example 5

[0091] This comparative example provides a method for preparing a polymer, the method comprising:

[0092] Dissolve 2.07 g of AMPS monomer in a three-necked flask containing an appropriate amount of water, and adjust the pH to approximately 8 with a 30 wt% NaOH aqueous solution. Add the remaining four monomers according to the monomer molar ratio VMA:AMPS:DMDAAC:NVCL:VIM = 6:2:2:1:1. Purge oxygen with argon gas (30 min), raise the temperature to 60 °C, and add the initiator azobisisobutyrazoline hydrochloride VA-044. The initiator mass is 0.75% of the total monomer mass. Continue the reaction for 10 h to terminate the reaction. After the reaction, the crude product is a pale yellow viscous liquid, which is washed, dried, and ground to obtain the final product.

[0093] Comparative Example 6

[0094] This comparative example provides a method for preparing a polymer, the method comprising:

[0095] Dissolve 2.07 g of monomer AMPS in a three-necked flask containing an appropriate amount of water, and adjust the pH to approximately 8 using a 30 wt% NaOH aqueous solution. Add the remaining four monomers according to the monomer molar ratio VMA:AMPS:DMDAAC:NVCL:VIM = 6:2:2:1:1. Purge oxygen with argon gas (30 min), raise the temperature to 50 °C, and add initiator VA-044. The initiator mass is 0.75% of the total monomer mass. Continue the reaction for 10 h to complete the reaction. After the reaction is complete, a pale yellow viscous liquid is obtained. Wash, dry, and grind to obtain the final product.

[0096] Comparison of the 1H NMR spectra of the polymers and monomers prepared in Comparative Examples 1-6 Figure 3 As shown, there is a significant olefin absorption peak of the monomer in the range of 5.0-8.0 ppm, indicating a low monomer conversion rate.

[0097] The molecular weights and monomer conversion rates of the copolymers of Examples 1 to 5 and the final products of Comparative Examples 1 to 6 are shown in Table 1:

[0098] Table 1

[0099] . Mw / kDa PDI Monomer conversion rate Comparative Example 1 79 2.122 55.3％ Comparative Example 2 178 2.781 64.0％ Comparative Example 3 96 2.569 68.5％ Comparative Example 4 195 3.141 70.0％ Comparative Example 5 319 2.287 77.6％ Comparative Example 6 327 2.979 61.3％ Example 1 247 3.768 95.6％ Example 2 287 3.679 100％ Example 3 366 3.528 100％ Example 4 352 4.130 100％ Example 5 318 4.720 99.4％

[0100] As can be seen from the results in Table 1, compared with precipitation polymerization, solution polymerization in this invention is more conducive to obtaining copolymers with higher monomer conversion rates and higher molecular weights. Based on this, by controlling parameters such as reaction temperature and initiator dosage, this invention can further improve the monomer conversion rate of the copolymerization reaction and the molecular weight of the resulting copolymers.

[0101] Test Example 1

[0102] This test example provides an evaluation of the rheological properties and filtration loss reduction properties of the prepared aqueous pentagonal random copolymer based on the above examples.

[0103] 1. Testing in freshwater experimental slurry

[0104] The temperature-resistant filtration loss reduction properties of the five-component random copolymers prepared in Examples 1, 2, 3, 4, and 5 as filtration loss reducing agents in bentonite slurries were evaluated. After aging at 200°C for 16 hours, the pressure filtration loss in each slurry was determined using a Qingdao Tongchun SD4 four-unit fluid loss meter according to the specifications in GB / T16783.1-2014 Drilling Fluid Field Testing. The composition of the slurries was evaluated as follows:

[0105] Freshwater experimental slurry: 4% bentonite + 2% filtration loss reducer (pentametric random copolymer)

[0106] Freshwater-based slurry: Add 400mL of tap water to a high-speed stirring cup, add 16g of bentonite in a measured amount while stirring continuously, stir for 20min, stopping at least twice during the process to scrape off the clay (bentonite) adhering to the container wall, and cure in a sealed container for 24h.

[0107] Preparation of polymer drilling fluid system: Weigh the polymer to be tested quantitatively, mix and dissolve the polymer with 400 mL of the above-mentioned fresh water-based slurry, stir at high speed for 20 min, and let stand for 24 h to obtain a polymer drilling fluid system of a certain concentration (mass volume concentration).

[0108] Table 2 shows the performance test results of the novel high-temperature and salt-resistant polymer filtration loss reducer in freshwater slurry, using the drilling fluid field test procedure of GB / T16783.1-2014. AV is apparent viscosity, PV is plastic viscosity, YP is dynamic shear force, and FL... API This refers to the filtration loss under medium pressure at room temperature.

[0109] Table 2

[0110]

[0111] As shown in Table 2 above, adding 2% of the prepared filtrate loss reducer to the freshwater experimental slurry significantly increased the apparent viscosity and plastic viscosity. Furthermore, after aging at 200℃ for 16 hours, it still maintained a certain viscosity, indicating that the polymer has a good viscosity-enhancing effect and good temperature resistance. The FL after high-temperature aging... API It can reach 7.2 mL, which has a good effect on reducing filtration loss.

[0112] 2. Testing in saline slurry

[0113] Comparative sample 1 is a temperature-resistant polymer filtration reducer, Driscal D, from Chevron Phillips Chemical Company LP Drilling Specialties Company LLC;

[0114] Comparative sample 2 is Dristemp, a temperature-resistant polymer filtration reducer from Chevron Phillips Chemical Company LP Drilling Specialties Company LLC.

[0115] The temperature resistance and filtration loss reduction performance of the filtration loss reducing agents in Examples 1, 2, 3, 4, 5, and Comparative Samples 1 and 2 in bentonite slurry were evaluated. After aging at 200℃ for 16 hours, the pressure filtration loss in each slurry was determined using a Qingdao Tongchun SD4 four-unit fluid loss meter according to the specifications in GB / T16783.1-2014 Drilling Fluid Field Testing. The composition of the slurry was evaluated as follows:

[0116] Saltwater test slurry: 4% bentonite + 2% filtration loss reducer + 15% NaCl

[0117] Freshwater-based slurry: Add 400mL of tap water to a high-speed stirring cup, add 16g of bentonite in a measured amount while stirring continuously, stir for 20min, stopping at least twice during the process to scrape off the clay (bentonite) adhering to the container wall, and cure in a sealed container for 24h.

[0118] Preparation of brine slurry for polymer drilling fluid system: Weigh the prepared polymer quantitatively, mix and dissolve the polymer with 400 mL of the above-mentioned fresh water-based slurry, add 15% NaCl, stir at high speed for 20 min, and let stand for 24 h to obtain a polymer brine slurry drilling fluid system with a certain concentration (mass volume concentration).

[0119] The evaluation results are shown in Table 3, based on GB / T16783.1-2014 Drilling Fluid Field Testing Procedures.

[0120] Table 3 shows the performance test results of the novel high-temperature and salt-resistant polymer filtration loss reducer and comparative samples in brine slurry. AV is apparent viscosity, PV is plastic viscosity, YP is dynamic shear force, and FL is... API -API is the filtering rate.

[0121] Table 3

[0122]

[0123]

[0124] The test results in Table 3 show that, compared with Comparative Sample 1 and Comparative Sample 2, the brine test slurry prepared using the high-temperature and salt-water resistant polymer of this invention exhibits better filtration loss reduction performance. After hot rolling aging at 200℃ for 16 hours, the lowest filtration loss at room temperature under medium pressure is 9.0 mL, demonstrating superior temperature and salt resistance compared to Driscal D and Dristemp. The high-temperature and salt-water resistant polymer of this invention has a lower molecular weight, resulting in lower values ​​for rheological parameters such as apparent viscosity, plastic viscosity, and dynamic shear force in the prepared freshwater and brine test slurries. Furthermore, the changes in rheological parameters before and after hot rolling aging at 200℃ for 16 hours are minimal, indicating better high-temperature stability.

[0125] The test results above show that the high-temperature and salt-water resistant polymer of this embodiment has good rheological properties and filtration loss reduction effect in both fresh water and saturated 15% salt water drilling fluid. Its performance remains stable after being hot-rolled at 200°C for 16 hours, which is significantly better than similar filtration reducer products.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a five-component random copolymer, wherein the preparation method employs solution polymerization, comprising: The monomer is mixed with water to form a reaction solution, and an initiator is added in an oxygen-free protective atmosphere to carry out a free radical copolymerization reaction to obtain a five-member random copolymer. The monomers include N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyldiallylammonium chloride, N-vinylcaprolactam and alkenyl heterocyclic compounds; The free radical copolymerization reaction temperature is greater than 70℃ and less than or equal to 90℃, and the free radical copolymerization reaction time is 2-10h; the mass of the initiator is 0.7%-1% of the total mass of the monomers. The five-component random copolymer is formed by free radical copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyl diallyl ammonium chloride, N-vinylcaprolactam, N-alkenylamide and alkenyl heterocyclic compound; the molar ratio of N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyl diallyl ammonium chloride, N-vinylcaprolactam and alkenyl heterocyclic compound is (6-8):(1.7-4):(0.5-2):(1-2):(1-2).

2. The preparation method according to claim 1, wherein, The free radical copolymerization reaction temperature is 75℃-90℃.

3. The preparation method according to claim 1, wherein, The initiator includes one of potassium persulfate, ammonium persulfate, a combination of ammonium persulfate and sodium bisulfite, azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutyrazoline hydrochloride, and 2,2-azobis(2-methylpropanediamine) hydrochloride.

4. The preparation method according to claim 3, wherein, The initiator includes azobisisobutyronitrile or azobisisobutyrazole hydrochloride.

5. The preparation method according to claim 1, wherein, The pH value of the reaction solution is 6-9.

6. The preparation method according to claim 1, wherein, The N-alkenylamide includes one or more of N-vinylformamide, N-vinylacetamide, and N-methyl-N-vinylacetamide.

7. The preparation method according to claim 1, wherein, The alkenyl heterocyclic compound includes one or more combinations of N-vinylimidazolium, vinylpyridine, N-vinylcarbazole, and 4-methyl-5-vinylthiazole.

8. The preparation method according to claim 1, wherein, The molar ratio of the N-alkenylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyldiallylammonium chloride, N-vinylcaprolactam and alkenyl heterocyclic compound is (6-8):(2-4):(0.5-2):(1-2):(1-2).

9. The preparation method according to claim 1, wherein, The weight-average molecular weight of the pentagonal random copolymer is 247 kDa-366 kDa.

10. A five-component random copolymer, which is prepared by the method for preparing the five-component random copolymer according to any one of claims 1-9.

11. A filtration loss reducing agent comprising or made from the five-component random copolymer of claim 10.

12. A water-based drilling fluid comprising the filtration loss reducer as described in claim 11.

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