A branched polymer viscosity reducer, its preparation method and application

Abstract

The present invention provides a branched polymer viscosity reducer and its preparation method and application. The raw materials for preparing the branched polymer viscosity reducer include an organic monomer, a chain transfer agent, an initiator and a solvent; the organic monomer includes 2-acrylamido-2-methyl-1-propane sulfonic acid, an organic acid, maleic anhydride and polyoxyethylene propylene glycol ether. The present invention designs the raw materials for preparing the polymer viscosity reducer to obtain a polymer viscosity reducer with a branched chain. The branched polymer viscosity reducer has a high viscosity reduction rate at room temperature and can still maintain a high viscosity reduction rate after aging at high temperature (240°C) for 16 hours. At the same time, the preparation method of the branched polymer viscosity reducer is simple, the reaction conditions are mild, the cost is low, and it is suitable for industrial production and use.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to a branched polymer viscosity reducer, its preparation method, and its application. Background Technology

[0002] With economic development and continuously rising energy demand, conventional oil and gas resources can no longer meet daily needs. Oil and gas exploration and development are moving towards deep and ultra-deep wells, requiring increasingly stringent geological conditions. Drilling fluids play a crucial role in ensuring safe and rapid drilling in deep and ultra-deep wells. High-density drilling fluids are commonly used in deep and ultra-deep well drilling; however, excessive density and excessive weighting agent dosage can thicken the drilling fluid, affecting its rheological properties. Some drilling fluid treatment agents are composed of high-molecular-weight polymers, and the interaction between these polymer molecules and clay can also form a spatial network structure, causing increased viscosity of the drilling fluid. In the high-temperature and high-salt environment of deep and ultra-deep wells, treatment agents are prone to cross-linking and clay consolidation, deteriorating the flow properties of the drilling fluid. These factors severely impact the efficiency of deep and ultra-deep well drilling projects. Therefore, developing viscosity reducers for high-temperature resistant drilling fluids is one of the major challenges currently facing deep and ultra-deep well drilling fluids.

[0003] Early drilling fluid viscosity reducers were mainly lignin-modified dispersible viscosity reducers, one representative of which was iron-chromium lignin sulfonate (FCLS). FCLS exhibited good temperature and salt resistance and some filtration loss reduction, but its viscosity increased and effectiveness decreased at high temperatures. Furthermore, FCLS suffered from high toxicity and severe pollution, making it unsuitable for today's increasingly stringent environmental regulations. Currently, one of the main polymer-based viscosity reducers is XY-27. Its mechanism of action involves preferential adsorption onto the surface of clay particles and the formation of a complex with a high-molecular-weight polymer coating agent, thereby hindering the formation of a network structure on the clay surface and reducing drilling fluid viscosity and shear. In common research, polymer-based viscosity reducers are predominantly copolymers based on monomers such as acrylic acid (AA), maleic anhydride (MA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0004] CN103305194A discloses a method for synthesizing a polymeric viscosity reducer. The method involves dissolving the reactants 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, and itaconic acid in water at a molar ratio of 1-6:1-5:1-2, adjusting the pH to 5, and heating the mixture to 40-80℃ for 2-16 hours to obtain a viscosity reducer product with a monomer content of 10%-40%. After aging at 180℃, the viscosity reduction rate of this product can reach 80%.

[0005] CN106479457A discloses a temperature- and salt-resistant viscosity reducer for drilling fluids, its preparation, and its uses. The preparation method includes: adding maleic anhydride and water to a reaction vessel, stirring to ensure complete dissolution, then heating, and simultaneously adding 2-acrylamide-2-methylpropanesulfonic acid, methacryloyloxyethyltrimethylammonium chloride, and an initiator while stirring at a uniform speed. After the reaction, the pH of the product is adjusted to 7-9 to obtain a light blue copolymer aqueous solution. The copolymer aqueous solution is then compounded with ethylenediaminetetraacetic acid to obtain the temperature- and salt-resistant viscosity reducer for drilling fluids. The viscosity reducer prepared by this method exhibits good viscosity-reducing effects in heavy salt cement slurries, with a temperature resistance reaching 220℃.

[0006] Chen Juanjuan et al. synthesized a terpolymer viscosity reducer, MAA, by copolymerizing sodium styrene sulfonate (SSS), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), and maleic anhydride (MA) via ammonium sulfate initiation. The optimal viscosity-reducing effect was achieved at a reaction temperature of 85℃, a reaction time of 2 hours, and a monomer molar ratio of n(MA):n(SSS):n(AMPS) = 1:0.8:0.8. Adding 0.5% of the viscosity reducer to a freshwater-based slurry resulted in a viscosity reduction rate of 70.8% at room temperature and 42.8% after aging at 220℃. The salt resistance reached 30%, and the calcium resistance was 0.8%. The viscosity reduction rate was relatively low at room temperature and also low after high-temperature aging.

[0007] The aforementioned products and patents utilize preferred functional monomers to prepare linear polymers via free radical polymerization. However, linear polymers suffer from drawbacks such as strong thickening effects and easy chain breakage, and their temperature resistance cannot meet field requirements. Furthermore, the degree of polymerization in free radical polymerization is difficult to control, resulting in polymers with larger molecular weights and higher molecular weight distributions, which is detrimental to the viscosity reduction effect of drilling fluids.

[0008] Therefore, how to provide a viscosity reducer with good high-temperature resistance and a simple preparation method has become an urgent technical problem to be solved. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a branched polymer viscosity reducer, its preparation method, and its application. This invention designs the raw materials for preparing the polymer viscosity reducer to obtain a branched polymer viscosity reducer. This branched polymer viscosity reducer exhibits a high viscosity reduction rate at room temperature and maintains a high viscosity reduction rate even after aging at high temperature (240℃) for 16 hours. Furthermore, the preparation method of this branched polymer viscosity reducer is simple, the reaction conditions are mild, and the cost is low, making it suitable for industrial production and use.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a branched polymer viscosity reducer, wherein the raw materials for preparing the branched polymer viscosity reducer include organic monomers, chain transfer agents, initiators and solvents;

[0012] The organic monomers include 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), organic acids, maleic anhydride (MA), and propylene glycol polyoxyethylene ether (APEG).

[0013] In this invention, a branched polymer viscosity reducer is obtained by designing the raw materials for preparing the polymer viscosity reducer. This branched polymer viscosity reducer has a high viscosity reduction rate at room temperature and can still maintain a high viscosity reduction rate after aging at high temperature (240℃) for 16 hours. At the same time, the preparation method of this branched polymer viscosity reducer is simple, the reaction conditions are mild, and the cost is low, making it suitable for industrial production and use.

[0014] Furthermore, in this invention, by introducing a large number of carboxylic acid groups as hydration groups into the molecular chain of the branched polymer viscosity reducer using organic acids and maleic anhydrides, the adsorption and hydration properties of the branched polymer viscosity reducer can be improved. The use of 2-acrylamido-2-methyl-1-propanesulfonic acid can thicken the diffuse double layer and hydration film on the clay surface, effectively improving the temperature resistance of the polymer viscosity reducer. The propylene alcohol polyoxyethylene ether monomer has a long branched chain, large steric hindrance within the molecule, and strong rigidity. By using propylene alcohol polyoxyethylene ether, branched chains are introduced into the branched polymer viscosity reducer, improving its temperature resistance.

[0015] This invention utilizes the synergistic effect of 2-acrylamido-2-methyl-1-propanesulfonic acid and propylene alcohol polyoxyethylene ether to prepare a branched polymer viscosity reducer with good temperature resistance.

[0016] The polymerization method of the branched polymer viscosity reducer provided in this invention is reversible addition-fragmentation chain transfer polymerization (RAFT polymerization). A chain transfer agent with a high chain transfer constant is added to the traditional free radical polymerization system to achieve the purpose of "living" polymerization. During the polymerization process, the primary free radicals generated by the initiator can rapidly transfer to the RAFT chain transfer agent, effectively controlling the degree of polymerization reaction and obtaining a branched polymer viscosity reducer with low molecular weight and narrow molecular weight distribution.

[0017] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0018] As a preferred embodiment of the present invention, with the organic monomer having a mass percentage content of 100%, the chain transfer agent has a mass percentage content of 0.5-1%, for example, it can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%, etc.

[0019] Preferably, the initiator has a mass percentage of 0.3-0.5% based on the organic monomer having a mass percentage of 100%, for example, it can be 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, or 0.5%, etc.

[0020] Preferably, the molar ratio of 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride, and propylene glycol polyoxyethylene ether is (2-3):(5-6):(2-3):(0.5-1), wherein the value of 2-3 can be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3, etc.; the value of 5-6 can be 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, or 6, etc.; and the value of 0.5-1 can be 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc.

[0021] In this invention, a high-performance branched polymer viscosity reducer was prepared by controlling the molar ratio of 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride, and propylene glycol polyoxyethylene ether within a specific range. If the amount of any component among 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride, and propylene glycol polyoxyethylene ether is outside the above range, the prepared branched polymer viscosity reducer exhibits low viscosity reduction rates at room temperature and after high-temperature aging.

[0022] As a preferred embodiment of the present invention, the organic acid includes any one or a combination of at least two of acrylic acid, methacrylic acid, and itaconic acid.

[0023] Preferably, the number average molecular weight of the propylene alcohol polyoxyethylene ether is ≤400, for example, it can be 200, 250, 300, 350 or 400.

[0024] Preferably, the propylene alcohol polyoxyethylene ether comprises APEG-300 or APEG-400.

[0025] As a preferred embodiment of the present invention, the chain transfer agent includes any one or a combination of at least two of ethyl xanthate, potassium xanthate, and butyl xanthate.

[0026] Preferably, the initiator comprises any one or a combination of at least two of potassium persulfate, azobisisobutyronitrile (AIBN), or benzoyl peroxide (BPO).

[0027] Preferably, the raw materials for preparing the branched polymer viscosity reducer also include a solvent.

[0028] Preferably, the solvent includes water.

[0029] Preferably, with the sum of the mass percentages of the solvent and the organic monomer being 100%, the mass percentage of the organic monomer is 10-30%, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, or 30%, etc.

[0030] In a second aspect, the present invention provides a method for preparing a branched polymer viscosity reducer as described in the first aspect, the method comprising the following steps:

[0031] After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), organic acid, maleic anhydride (MA) and solvent, the pH of the reaction system is adjusted to 7-9, and then propylene alcohol polyoxyethylene ether is added and mixed.

[0032] An initiator and a chain transfer agent are then added to the reaction system, and the reaction proceeds to obtain the branched polymer viscosity reducer.

[0033] The pH of the above-mentioned adjustment reaction system is 7-9, for example, it can be 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8 or 9, etc.

[0034] The branched polymer viscosity reducer provided in this invention is polymerized by reversible addition-fragmentation chain transfer polymerization (RAFT polymerization). A chain transfer agent with a high chain transfer constant is added to the traditional free radical polymerization system to achieve the purpose of "living" polymerization. During the polymerization process, the primary free radicals generated by the initiator can rapidly transfer to the RAFT chain transfer agent, effectively controlling the degree of polymerization reaction and obtaining polymers with low molecular weight and narrow molecular weight distribution. The preparation method is simple, the reaction conditions are mild, and it is suitable for industrial production.

[0035] As a preferred embodiment of the present invention, the base used to adjust the pH of the reaction system includes NaOH.

[0036] It should be noted that when using alkalis such as NaOH to adjust the pH of the reaction system in this invention, a corresponding alkali solution (such as NaOH solution) can be added to the reaction system to adjust the pH. Furthermore, this invention does not impose any special restrictions on the mass concentration of the alkali solution; it is sufficient that the pH of the reaction system can be adjusted to 7-9 after adding the alkali solution.

[0037] Preferably, the addition of the propylene alcohol polyoxyethylene ether further includes a post-treatment step, the post-treatment method comprising: introducing nitrogen gas to remove oxygen.

[0038] As a preferred embodiment of the present invention, when the initiator and chain transfer agent are added, the temperature of the reaction system is 40-50°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, etc.

[0039] Preferably, the reaction time is 2-3 hours, for example, 2 hours, 2.5 hours or 3 hours.

[0040] Preferably, the reaction further includes a post-processing step.

[0041] Preferably, the post-processing method includes: washing, drying, and pulverizing.

[0042] Preferably, the washing solvent includes ethanol.

[0043] It should be noted that the present invention does not impose any special restrictions on the drying temperature and time, and all commonly used drying temperatures in the art are applicable; at the same time, the present invention does not impose any special restrictions on the particle size of the pulverized branched polymer viscosity reducer, and all commonly used particle size ranges in the art are applicable.

[0044] As a preferred embodiment of the present invention, the preparation method of the branched polymer viscosity reducer specifically includes the following steps:

[0045] After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), organic acid, maleic anhydride (MA) and solvent, the pH of the reaction system is adjusted to 7-9. Then, propylene glycol polyoxyethylene ether (APEG) is added and mixed, and nitrogen gas is introduced to remove oxygen.

[0046] Raise the temperature of the reaction system to 40-50℃, add an initiator and a chain transfer agent to the reaction system, react for 2-3 hours, then wash, dry, and pulverize to obtain the branched polymer viscosity reducer.

[0047] Thirdly, the present invention provides an application of the branched polymer viscosity reducer as described in the first aspect, wherein the branched polymer viscosity reducer is used to prepare water-based drilling fluid.

[0048] Preferably, the water-based drilling fluid is used for deep or ultra-deep well drilling.

[0049] As a preferred embodiment of the present invention, the mass concentration of the branched polymer viscosity reducer in the water-based drilling fluid is 0.2-0.5%, for example, it can be 0.2%, 0.22%, 0.25%, 0.27%, 0.3%, 0.33%, 0.36%, 0.39%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, or 0.5%.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) This invention designs the raw materials for preparing polymer viscosity reducers. By using 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride and propylene alcohol polyoxyethylene ether, a branched polymer viscosity reducer with a specific structure is obtained. This branched polymer viscosity reducer has a low weight-average molecular weight and a narrow molecular weight distribution (≤1.33). Adding 0.3% by mass of the branched polymer viscosity reducer sample to water-based drilling fluid can significantly reduce the viscosity of the drilling fluid at φ100. After aging at high temperature (240℃) for 16 hours, it can still maintain a high viscosity reduction rate. The viscosity reduction rate at room temperature is ≥72.9%, specifically 72.9~79.2%, and after aging at high temperature (240℃) for 16 hours, its viscosity reduction rate is ≥61.5%, specifically 61.5~76.9%.

[0052] (2) By further controlling the amount of each component in the organic monomer of the raw material for preparing the branched polymer viscosity reducer within a specific range, this invention can further improve the comprehensive performance of the branched polymer viscosity reducer. The prepared branched polymer viscosity reducer has a lower weight-average molecular weight and a narrower molecular weight distribution. Adding 0.3% by mass of the branched polymer viscosity reducer to the water-based drilling fluid can significantly reduce the viscosity of the drilling fluid at φ100, and it can still maintain a high viscosity reduction rate after aging at 240℃ for 16 hours. The viscosity reduction rate at room temperature is ≥75.0%, specifically 75.0% to 79.2%, and after aging at high temperature (240℃) for 16 hours, its viscosity reduction rate is ≥67.8%, specifically 67.8% to 76.9%.

[0053] (3) The preparation method of the branched polymer viscosity reducer provided by the present invention is simple, the reaction conditions are mild, the cost is low, and it is suitable for industrial production and use. Detailed Implementation

[0054] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0055] The sources of some components in the examples and comparative examples are as follows:

[0056] APEG-300: Purchased from Jiangsu Haian Petrochemical;

[0057] APEG-400: Purchased from Jiangsu Haian Petrochemical.

[0058] Example 1

[0059] This embodiment provides a branched polymer viscosity reducer and its preparation method. The raw materials for preparing the branched polymer viscosity reducer include the following components:

[0060] 2-Acrylamido-2-methyl-1-propanesulfonic acid (13g, 0.063mol), acrylic acid (11.3g, 0.157mol), maleic anhydride (6.2g, 0.063mol), APEG-300 (9.4g, 0.031mol), ethyl xanthate (300mg), potassium persulfate (150mg), and water (200mL);

[0061] The preparation method of the above-mentioned branched polymer viscosity reducer is as follows:

[0062] After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid, acrylic acid, maleic anhydride and water, the pH of the reaction system was adjusted to 7.5 using a 60% NaOH solution. Then, APEG-300 was added and mixed, and nitrogen gas was introduced to remove oxygen.

[0063] After raising the temperature of the reaction system to 45°C, ethyl xanthate and potassium persulfate were added to the reaction system. After stirring continuously for 3 hours, the mixture was thoroughly washed with anhydrous ethanol, dried, and pulverized to obtain the branched polymer viscosity reducer.

[0064] Example 2

[0065] This embodiment provides a branched polymer viscosity reducer and its preparation method. The raw materials for preparing the branched polymer viscosity reducer include the following components:

[0066] 2-Acrylamido-2-methyl-1-propanesulfonic acid (18.6 g, 0.09 mol), methacrylic acid (15.4 g, 0.179 mol), maleic anhydride (8.8 g, 0.09 mol), APEG-400 (7.2 g, 0.018 mol), potassium xanthate (250 mg), azobisisobutyronitrile (200 mg), and water (200 mL);

[0067] The preparation method of the above-mentioned branched polymer viscosity reducer is as follows:

[0068] After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid, methacrylic acid, maleic anhydride and water, the pH of the reaction system was adjusted to 8 using a 60% NaOH solution. Then, APEG-400 was added and mixed, and nitrogen gas was introduced to remove oxygen.

[0069] After raising the temperature of the reaction system to 40°C, potassium xanthate and azobisisobutyronitrile were added to the reaction system. After stirring the reaction continuously for 3 hours, the system was thoroughly washed with anhydrous ethanol, dried, and pulverized to obtain the branched polymer viscosity reducer.

[0070] Example 3

[0071] This embodiment provides a branched polymer viscosity reducer and its preparation method. The raw materials for preparing the branched polymer viscosity reducer include the following components:

[0072] 2-Acrylamido-2-methyl-1-propanesulfonic acid (13g, 0.063mol), acrylic acid (13.6g, 0.189mol), maleic anhydride (9.2g, 0.094mol), APEG-300 (6.6g, 0.022mol), ethyl xanthate (340mg), potassium persulfate (130mg), and water (200mL);

[0073] The preparation method of the above-mentioned branched polymer viscosity reducer is as follows:

[0074] After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid, acrylic acid, maleic anhydride and water, the pH of the reaction system was adjusted to 7 using a 60% NaOH solution. Then APEG-300 was added and mixed, and nitrogen gas was introduced to remove oxygen.

[0075] After raising the temperature of the reaction system to 50°C, ethyl xanthate and potassium persulfate were added to the reaction system. After stirring continuously for 2 hours, the mixture was thoroughly washed with anhydrous ethanol, dried, and pulverized to obtain the branched polymer viscosity reducer.

[0076] Example 4

[0077] This embodiment provides a branched polymer viscosity reducer and its preparation method. The raw materials for preparing the branched polymer viscosity reducer include the following components:

[0078] 2-Acrylamido-2-methyl-1-propanesulfonic acid (18.6 g, 0.09 mol), acrylic acid (10.8 g, 0.15 mol), maleic anhydride (5.9 g, 0.06 mol), APEG-400 (12 g, 0.03 mol), ethyl xanthate (470 mg), potassium persulfate (235 mg), and water (200 mL);

[0079] The preparation method of the above-mentioned branched polymer viscosity reducer is as follows:

[0080] After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid, acrylic acid, maleic anhydride and water, the pH of the reaction system was adjusted to 7.5 using a 60% NaOH solution. Then, APEG-300 was added and mixed, and nitrogen gas was introduced to remove oxygen.

[0081] After raising the temperature of the reaction system to 45°C, ethyl xanthate and potassium persulfate were added to the reaction system. After stirring continuously for 3 hours, the mixture was thoroughly washed with anhydrous ethanol, dried, and pulverized to obtain the branched polymer viscosity reducer.

[0082] Examples 5-9

[0083] Examples 5-9 each provide a branched polymer viscosity reducer and its preparation method, differing from Example 1 only in the composition of the raw materials used in the preparation of the branched polymer viscosity reducer:

[0084] In Example 5: 2-Acrylamido-2-methyl-1-propanesulfonic acid (20.7 g, 0.100 mol), acrylic acid (15.8 g, 0.220 mol), maleic anhydride (9.8 g, 0.100 mol), APEG-300 (9.6 g, 0.032 mol), ethyl xanthate (390 mg), potassium persulfate (220 mg), and water (200 mL);

[0085] In Example 6: 2-Acrylamido-2-methyl-1-propanesulfonic acid (16.6 g, 0.080 mol), acrylic acid (15.8 g, 0.220 mol), maleic anhydride (9.8 g, 0.100 mol), APEG-300 (9.6 g, 0.032 mol), ethyl xanthate (362 mg), potassium persulfate (202 mg), and water (185 mL);

[0086] In Example 7: 2-Acrylamido-2-methyl-1-propanesulfonic acid (24.8 g, 0.120 mol), acrylic acid (15.8 g, 0.220 mol), maleic anhydride (9.8 g, 0.100 mol), APEG-300 (9.6 g, 0.032 mol), ethyl xanthate (420 mg), potassium persulfate (234 mg), and water (215 mL);

[0087] In the examples: 2-Acrylamido-2-methyl-1-propanesulfonic acid (12.4 g, 0.060 mol), acrylic acid (15.8 g, 0.220 mol), maleic anhydride (9.8 g, 0.100 mol), APEG-300 (9.6 g, 0.032 mol), ethyl xanthate (333 mg), potassium persulfate (185 mg), and water (170 mL);

[0088] In Example 9: 2-Acrylamido-2-methyl-1-propanesulfonic acid (33.2 g, 0.160 mol), acrylic acid (15.8 g, 0.220 mol), maleic anhydride (9.8 g, 0.100 mol), APEG-300 (9.6 g, 0.032 mol), ethyl xanthate (480 mg), potassium persulfate (268 mg), and water (245 mL);

[0089] The preparation method of the branched polymer viscosity reducer is described in Example 1.

[0090] Examples 10-13

[0091] Examples 10-13 each provide a branched polymer viscosity reducer and its preparation method, differing from Example 5 only in the amount of ethyl xanthate in the raw materials for preparing the branched polymer viscosity reducer:

[0092] In Example 10: the amount of ethyl xanthate was 280 mg;

[0093] In Example 11: the amount of ethyl xanthate was 559 mg;

[0094] In Example 12: the amount of ethyl xanthate was 220 mg;

[0095] In Example 13: the amount of ethyl xanthate was 727 mg;

[0096] Other conditions are the same as in Example 5.

[0097] Comparative Examples 1-5

[0098] Comparative Examples 1-5 each provide a branched polymer viscosity reducer and its preparation method, differing from Example 5 only in the composition of the raw materials used in the preparation of the branched polymer viscosity reducer:

[0099] In Comparative Example 1: 2-Acrylamido-2-methyl-1-propanesulfonic acid was not used; the amount of ethyl xanthate was 246 mg; and the amount of potassium persulfate was 137 mg.

[0100] In Comparative Example 2: no acrylic acid was used, the amount of ethyl xanthate was 280 mg, and the amount of potassium persulfate was 156 mg.

[0101] In Comparative Example 3: Maleic anhydride was not used; the amount of ethyl xanthate was 323 mg; and the amount of potassium persulfate was 180 mg.

[0102] In Comparative Example 4: APEG-300 was not used, the amount of ethyl xanthate was 324 mg, and the amount of potassium persulfate was 180 mg;

[0103] Comparative Example 5: Ethyl xanthate was not used;

[0104] The dosage of other components and the preparation method of the branched polymer viscosity reducer are the same as in Example 5.

[0105] Comparative Example 6

[0106] This comparative example provides a viscosity reducer, XY-27, purchased from Zhengzhou Jingyuan Slurry Materials.

[0107] The performance of the viscosity reducers provided in the above embodiments and comparative examples was characterized using the following specific test methods:

[0108] The temperature-resistant viscosity-reducing performance of the viscosity reducers provided in the above embodiments and comparative examples in bentonite slurries was evaluated. After aging at 240°C for 16 hours, the rheological properties of each slurry were measured using a six-speed viscometer according to the specifications in "SYT 5695-2017 Viscosity Reducers for Drilling Fluids: Amphoteric Polymers". The composition of the experimental slurries is as follows:

[0109] Basic formula: Take 400mL of distilled water and add 24g of bentonite, 0.8g of anhydrous sodium carbonate, and 0.4g of polyacrylamide (purchased from Aladdin, non-ionic polyacrylamide, P108471) quantitatively while stirring continuously. Stir at high speed (11000rpm) for 20min, stopping at least twice during the process to scrape off the clay adhering to the container wall. Cure in a sealed container for 24h to obtain the base slurry.

[0110] Experimental formulation: Take 400 mL of cured base slurry, add 1.2 g of the prepared viscosity reducer, stir at low speed for 10 min, and then stir at high speed for 5 min.

[0111] The basic and experimental formulations were aged at 240℃ for 16 hours before and after aging. Viscosity was tested under the specified conditions, and the viscosity reduction rate was calculated; among which,

[0112] The evaluation results are shown in Table 1. The viscosity reduction rate was tested according to the specifications of "SYT 5695-2017 Amphoteric Polymers for Viscosity Reducers in Drilling Fluids".

[0113] Weight-average molecular weight: determined by gel permeation chromatography (Tosoh HLC-8420GPC) at room temperature;

[0114] Molecular weight distribution index: The molecular weight distribution index was determined by gel permeation chromatography (Tosoh HLC-8420GPC) at room temperature.

[0115] The above performance test structure is shown in Table 1 below:

[0116] Table 1

[0117]

[0118]

[0119] As can be seen from the above, this invention designs the raw materials for preparing the polymer viscosity reducer. By using 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride, and propylene alcohol polyoxyethylene ether, a branched polymer viscosity reducer with a specific structure is obtained. This branched polymer viscosity reducer has a low weight-average molecular weight and a narrow molecular weight distribution (≤1.33). Adding 0.3% by mass of the branched polymer viscosity reducer sample to water-based drilling fluid can significantly reduce the viscosity of the drilling fluid at φ100. Even after aging at 240℃ for 16 hours, it can still maintain a high viscosity reduction rate. The viscosity reduction rate at room temperature is ≥72.9%, specifically 72.9-79.2%, and after aging at high temperature (240℃) for 16 hours, its viscosity reduction rate is ≥61.5%, specifically 61.5-76.9%. At the same time, the preparation method of the branched polymer viscosity reducer provided by this invention is simple, the reaction conditions are mild, and the cost is low, making it suitable for industrial production and use.

[0120] As can be seen from Examples 5-9, by controlling the amount of each component in the organic monomer of the raw material for preparing the branched polymer viscosity reducer within a specific range, the present invention can further improve the comprehensive performance of the branched polymer viscosity reducer. The prepared branched polymer viscosity reducer has a low weight-average molecular weight and a narrow molecular weight distribution. Adding 0.3% by mass of the branched polymer viscosity reducer sample to the water-based drilling fluid can significantly reduce the viscosity of the drilling fluid at φ100, and it can still maintain a high viscosity reduction rate after aging at 240℃ for 16 hours. The viscosity reduction rate at room temperature is ≥75.0%, specifically 75.0-79.2%, and after aging at high temperature (240℃) for 16 hours, its viscosity reduction rate is ≥67.8%, specifically 67.8-76.9%.

[0121] As can be seen from Examples 5 and 10-13, the present invention can further improve the overall performance of branched polymer viscosity reducers by controlling the amount of chain transfer agent within a specific range.

[0122] As can be seen from Examples 1-13 and Comparative Examples 1-5, the present invention has prepared a high-performance branched polymer viscosity reducer by designing the raw materials for preparing the polymer viscosity reducer.

[0123] As can be seen from Examples 1-13 and Comparative Example 6, the branched polymer viscosity reducer provided by the present invention has superior high-temperature resistance.

[0124] In summary, this invention, through the design of raw materials for preparing polymer viscosity reducers, and by using 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acids, maleic anhydride, and propylene alcohol polyoxyethylene ether, yields a branched polymer viscosity reducer with a specific structure. This branched polymer viscosity reducer exhibits a low weight-average molecular weight, a narrow molecular weight distribution, and good high-temperature resistance. Furthermore, the preparation method of the branched polymer viscosity reducer provided by this invention is simple, the reaction conditions are mild, and the cost is low, making it suitable for industrial production and use.

[0125] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A branched polymer viscosity reducer, characterized in that, The raw materials for preparing the branched polymer viscosity reducer include organic monomers, chain transfer agents, and initiators; The organic monomers include 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acids, maleic anhydride, and propylene alcohol polyoxyethylene ether; The molar ratio of 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride and propylene alcohol polyoxyethylene ether is (2-3):(5-6):(2-3):(0.5-1); The organic acid includes any one or a combination of at least two of acrylic acid, methacrylic acid, and itaconic acid.

2. The branched polymer viscosity reducer according to claim 1, characterized in that, With the organic monomer comprising 100% by mass, the chain transfer agent comprises 0.5-1% by mass.

3. The branched polymer viscosity reducer according to claim 1, characterized in that, With the organic monomer comprising 100% by mass, the initiator comprises 0.3-0.5% by mass.

4. The branched polymer viscosity reducer according to claim 1, characterized in that, The number average molecular weight of the propylene alcohol polyoxyethylene ether is ≤400.

5. The branched polymer viscosity reducer according to claim 1, characterized in that, The propylene alcohol polyoxyethylene ether includes APEG-300 or APEG-400.

6. The branched polymer viscosity reducer according to claim 1, characterized in that, The chain transfer agent includes any one or a combination of at least two of ethyl xanthate, potassium xanthate, and butyl xanthate.

7. The branched polymer viscosity reducer according to claim 1, characterized in that, The initiator includes any one or a combination of at least two of potassium persulfate, azobisisobutyronitrile, or benzoyl peroxide.

8. The branched polymer viscosity reducer according to claim 1, characterized in that, The raw materials for preparing the branched polymer viscosity reducer also include solvents.

9. The branched polymer viscosity reducer according to claim 8, characterized in that, The solvent includes water.

10. The branched polymer viscosity reducer according to claim 8, characterized in that, With the sum of the mass percentages of the solvent and the organic monomer being 100%, the mass percentage of the organic monomer is 10-30%.

11. A method for preparing a branched polymer viscosity reducer as described in any one of claims 1-10, characterized in that, The preparation method includes the following steps: After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride and solvent, the pH of the reaction system is adjusted to 7-9, and then propylene alcohol polyoxyethylene ether is added and mixed. An initiator and a chain transfer agent are then added to the reaction system, and the reaction proceeds to obtain the branched polymer viscosity reducer.

12. The preparation method according to claim 11, characterized in that, The base used to adjust the pH of the reaction system includes NaOH.

13. The preparation method according to claim 11, characterized in that, The process of adding the propylene alcohol polyoxyethylene ether to the mixture also includes a post-treatment step, the post-treatment method of which includes: introducing nitrogen gas to remove oxygen.

14. The preparation method according to claim 11, characterized in that, When the initiator and chain transfer agent are added, the temperature of the reaction system is 40-50℃.

15. The preparation method according to claim 11, characterized in that, The reaction time is 2-3 hours.

16. The preparation method according to claim 11, characterized in that, The reaction also includes a post-processing step.

17. The preparation method according to claim 16, characterized in that, The post-processing methods include: washing, drying, and pulverizing.

18. The preparation method according to claim 17, characterized in that, The washing solvent includes ethanol.

19. The preparation method according to claim 11, characterized in that, The preparation method of the branched polymer viscosity reducer specifically includes the following steps: After mixing 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride and solvent, the pH of the reaction system is adjusted to 7-9, and then propylene alcohol polyoxyethylene ether is added and mixed, and nitrogen gas is introduced to remove oxygen. Raise the temperature of the reaction system to 40-50℃, add an initiator and a chain transfer agent to the reaction system, react for 2-3 hours, then wash, dry, and pulverize to obtain the branched polymer viscosity reducer.

20. The application of a branched polymer viscosity reducer as described in any one of claims 1-10, characterized in that, The branched polymer viscosity reducer is used to prepare water-based drilling fluid.

21. The application according to claim 20, characterized in that, The water-based drilling fluid is used for deep or ultra-deep well drilling.

22. The application according to claim 20, characterized in that, The mass concentration of the branched polymer viscosity reducer in the water-based drilling fluid is 0.2-0.5%.

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