Branched chain type polymer viscosity reducer as well as preparation method and application thereof

Abstract

The invention provides a branched chain type polymer viscosity reducer as well as a preparation method and application thereof. The branched chain type polymer viscosity reducer is prepared from the following raw materials: an organic monomer, a chain transfer agent, an initiator and a solvent, the organic monomer is prepared from 2-acrylamido-2-methyl-1-propanesulfonic acid, organic acid, maleic anhydride and allyl alcohol polyoxyethylene ether. The preparation raw materials of the polymer viscosity reducer are designed to obtain the polymer viscosity reducer with a branched chain, and the branched chain type polymer viscosity reducer has a higher viscosity reduction rate at room temperature, and can still maintain the higher viscosity reduction rate after being aged for 16 hours at a high temperature (240 DEG C); meanwhile, the branched chain type polymer viscosity reducer is simple in preparation method, mild in reaction condition, low in cost and suitable for industrial production and use.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemical industry, and in particular relates to a branched polymer viscosity reducer and a preparation method and application thereof. Background Art

[0002] With economic development, energy demand continues to rise, conventional oil and gas resources cannot meet daily needs, and oil and gas resource exploration and development are moving towards deep wells and ultra-deep wells, and the formation conditions that need to be overcome are becoming more and more harsh. Drilling fluid plays a very critical role in ensuring the safety and rapid drilling of deep and ultra-deep wells. In deep and ultra-deep well drilling, high-density drilling fluids are often used. However, if the density is too high and the weighting agent is added too much, it will thicken the drilling fluid and affect the rheological properties; some drilling fluid treatment agents are composed of high molecular weight polymers, and the interaction between such polymer molecules and clay will also form a spatial network structure, causing the viscosity of the drilling fluid to increase. The treatment agent is prone to cross-linking and clay consolidation in the high temperature and high salt environment of deep and ultra-deep wells, which deteriorates the flow properties of the drilling fluid; the above factors seriously affect the efficiency of deep and ultra-deep well drilling projects. Therefore, the development of viscosity reducers for high-temperature resistant drilling fluids is one of the major challenges currently facing deep and ultra-deep well drilling fluids.

[0003] In the early days, the viscosity reducers for drilling fluids were mainly dispersed viscosity reducers and lignin modified products. One of the representative products was iron chromium lignin sulfonate (FCLS), which has good temperature and salt resistance and certain filtration loss reduction effect, but increases viscosity and reduces efficiency at high temperatures. At the same time, FCLS has the disadvantages of high toxicity and serious pollution. It is no longer fully applicable today when environmental protection requirements are increasing. At present, one of the main products of polymer viscosity reducers is XY-27. The mechanism of action of this viscosity reducer is that on the one hand, it preferentially adsorbs on the surface of clay particles, and on the other hand, it forms a "complex" with high molecular weight polymer coating agents, thereby hindering the network structure formed by the coating agent on the clay surface, which plays a role in reducing the viscosity and cutting of drilling fluids. In common research, most of the polymer viscosity reducers are copolymer viscosity reducers 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 polymer viscosity reducer. The method comprises the following steps: dissolving reaction monomers 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 value to 5, heating the temperature to 40-80°C and reacting for 2-16 hours to obtain a viscosity reducer product having a monomer content of 10%-40%. The viscosity reduction rate of the product can reach 80% after aging at 180°C.

[0005] CN106479457A discloses a temperature-resistant and salt-resistant viscosity reducer for drilling fluid and its preparation and use. The preparation method comprises: adding maleic anhydride and water to a reactor, stirring to fully dissolve them, then heating, adding 2-acrylamide-2-methylpropanesulfonic acid, methacryloyloxyethyl trimethylammonium chloride and an initiator while stirring at a uniform speed, and after the reaction, adjusting the pH value of the product to 7-9 to obtain a light blue copolymer aqueous solution; compounding the copolymer aqueous solution with ethylenediaminetetraacetic acid to obtain a temperature-resistant and salt-resistant viscosity reducer for drilling fluid. The viscosity reducer prepared by the method has a good viscosity reduction effect in weighted brine mud, and the temperature resistance reaches 220°C.

[0006] Chen Juanjuan et al. obtained the terpolymer viscosity reducer MAA by copolymerization of sodium styrene sulfonate (SSS), 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and maleic anhydride (MA) initiated by ammonium sulfate. The best viscosity reduction effect was achieved when the reaction temperature was 85°C, the reaction time was 2h, and the monomer molar ratio was n(MA):n(SSS):n(AMPS)=1:0.8:0.8. When 0.5% viscosity reducer was added to the fresh water base slurry, the viscosity reduction rate at room temperature was 70.8%, and the viscosity reduction rate after aging at 220°C was 42.8%. The salt resistance was 30%, and the calcium resistance was 0.8%. The viscosity reduction rate at room temperature was low, and the viscosity reduction rate after high temperature aging was also low.

[0007] The above products and patents are mostly prepared linear polymers through free radical polymerization of preferred functional monomers. However, linear polymers have disadvantages such as strong viscosity-increasing effect and easy molecular chain breaking, and the temperature resistance cannot meet the on-site requirements; at the same time, the degree of polymerization of free radical polymerization is difficult to control, and the molecular weight of the obtained polymer is relatively large and the molecular weight distribution is high, which is not conducive to the viscosity reduction effect of drilling fluid.

[0008] Therefore, how to provide a viscosity reducer with good high temperature resistance and simple preparation method has become a technical problem that needs to be solved urgently. Summary of the invention

[0009] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a branched polymer viscosity reducer and a preparation method and application thereof. The present invention designs the raw materials for preparing the polymer viscosity reducer to obtain a polymer viscosity reducer with branches, which 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.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[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 an organic monomer, a chain transfer agent, an initiator and a solvent;

[0012] The organic monomers include 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), organic acid, maleic anhydride (MA) and acryl alcohol polyoxyethylene ether (APEG).

[0013] In the present invention, the raw materials for preparing the polymer viscosity reducer are designed to obtain a polymer viscosity reducer with branches. 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.

[0014] Furthermore, in the present invention, a large number of carboxylic acid groups are introduced as hydration groups in the molecular chain of the branched polymer viscosity reducer by organic acid and maleic anhydride, so that the adsorption and hydration performance of the branched polymer viscosity reducer can be improved; by using 2-acrylamide-2-methyl-1-propane sulfonic acid, the diffuse double layer and hydration film on the clay surface can be thickened to effectively improve the temperature resistance of the polymer viscosity reducer; the allyl alcohol polyoxyethylene ether monomer has a relatively long side chain, a large intramolecular steric hindrance, and a relatively strong rigidity. By using allyl alcohol polyoxyethylene ether, a branch chain is introduced into the branched polymer viscosity reducer, thereby improving the temperature resistance of the branched polymer viscosity reducer.

[0015] The invention prepares a branched polymer viscosity reducer with good temperature resistance through the synergistic effect of 2-acrylamide-2-methyl-1-propane sulfonic acid and propenyl alcohol polyoxyethylene ether.

[0016] The polymerization method of the branched polymer viscosity reducer provided in the present invention is a reversible addition fragmentation chain transfer polymerization (RAFT polymerization). A chain transfer agent with a high chain transfer constant is added to a 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 quickly undergo chain transfer to the RAFT chain transfer agent, effectively controlling the degree of polymerization reaction, and obtaining a branched polymer viscosity reducer with a low molecular weight and a 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. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0018] As a preferred technical solution of the present invention, based on the mass percentage of the organic monomer as 100%, the mass percentage of the chain transfer agent is 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, based on the mass percentage of the organic monomer as 100%, the mass percentage of the initiator is 0.3-0.5%, 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-propane sulfonic acid, organic acid, maleic anhydride and propenyl alcohol 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 the present invention, by controlling the molar ratio of 2-acrylamide-2-methyl-1-propane sulfonic acid, organic acid, maleic anhydride and polyoxyethylene propylene glycol ether within a specific range, a branched polymer viscosity reducer with excellent performance is prepared. If the amount of any component among 2-acrylamide-2-methyl-1-propane sulfonic acid, organic acid, maleic anhydride and polyoxyethylene propylene glycol ether is not within the above range, the viscosity reduction rate of the prepared branched polymer viscosity reducer at room temperature and after high temperature aging are both low.

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

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

[0024] Preferably, the polyoxyethylene propylene glycol ether includes APEG-300 or APEG-400.

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

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

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

[0028] Preferably, the solvent comprises water.

[0029] Preferably, taking the sum of the mass percentages of the solvent and the organic monomer as 100%, the mass percentage of the organic monomer is 10-30%, for example, 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 the branched polymer viscosity reducer as described in the first aspect, the preparation method comprising the following steps:

[0031] After mixing 2-acrylamide-2-methyl-1-propane sulfonic acid (AMPS), an organic acid, maleic anhydride (MA) and a solvent, adjusting the pH of the reaction system to 7-9, and then adding propylene alcohol polyoxyethylene ether thereto and mixing;

[0032] Then, an initiator and a chain transfer agent are added to the reaction system to react and obtain the branched polymer viscosity reducer.

[0033] The pH of the reaction system is adjusted to 7-9, for example, 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8 or 9.

[0034] The polymerization method of the branched polymer viscosity reducer provided in the present invention is a reversible addition fragmentation chain transfer polymerization (RAFT polymerization). A chain transfer agent with a high chain transfer constant is added to a 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 quickly undergo chain transfer to the RAFT chain transfer agent, effectively controlling the degree of polymerization reaction to obtain a polymer with a low molecular weight and a 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 technical solution of the present invention, the base used to adjust the pH of the reaction system includes NaOH.

[0036] It should be noted that when a base such as NaOH is used to adjust the pH of the reaction system in the present invention, a corresponding alkaline solution (such as NaOH solution) can be added to the reaction system to adjust the pH of the reaction system, and the present invention does not have any special restrictions on the mass concentration of the alkaline solution. It only needs to add the alkaline solution to adjust the pH of the reaction system to 7-9.

[0037] Preferably, after adding the propylene alcohol polyoxyethylene ether and mixing, a post-treatment step is also included, and the post-treatment method includes: introducing nitrogen to deoxygenate.

[0038] As a preferred technical solution of the present invention, when the initiator and the 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 h, for example, 2 h, 2.5 h or 3 h.

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

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

[0042] Preferably, the washing solvent comprises ethanol.

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

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

[0045] After 2-acrylamide-2-methyl-1-propane sulfonic acid (AMPS), an organic acid, maleic anhydride (MA) and a solvent are mixed, the pH of the reaction system is adjusted to 7-9, and then propylene glycol polyoxyethylene ether (APEG) is added thereto and mixed, and nitrogen is introduced to deoxygenate;

[0046] The temperature of the reaction system is raised to 40-50° C., an initiator and a chain transfer agent are added to the reaction system, and after reacting for 2-3 hours, the reaction system is washed, dried, and crushed to obtain the branched polymer viscosity reducer.

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

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

[0049] As a preferred technical solution 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) The present invention designs the raw materials for preparing the polymer viscosity reducer, and obtains a branched polymer viscosity reducer with a specific structure by using 2-acrylamide-2-methyl-1-propane sulfonic acid, organic acid, maleic anhydride and polyoxyethylene propene ether. The branched polymer viscosity reducer has a lower weight average molecular weight and a narrower molecular weight distribution (≤1.33). The addition of a branched polymer viscosity reducer sample with a mass concentration of 0.3% into a water-based drilling fluid can significantly reduce the drilling fluid φ100 viscosity, and can still maintain a high viscosity reduction rate after aging at a high temperature of 240°C for 16 hours. The viscosity reduction rate at room temperature is ≥72.9%, specifically 72.9-79.2%, and after aging at a high temperature (240°C) for 16 hours, the viscosity reduction rate is ≥61.5%, specifically 61.5-76.9%.

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

[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 DESCRIPTION

[0054] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] The sources of some components in the embodiments 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 a preparation method thereof. The raw materials for preparing the branched polymer viscosity reducer include the following components:

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

[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% mass concentration NaOH solution, and then APEG-300 was added thereto and mixed, and nitrogen was introduced to deoxygenate;

[0063] After the temperature of the reaction system was raised to 45° C., ethyl xanthate and potassium persulfate were added to the reaction system, and the reaction was continued with stirring for 3 hours, and then the system was fully washed with anhydrous ethanol, dried, and crushed to obtain the branched polymer viscosity reducer.

[0064] Example 2

[0065] This embodiment provides a branched polymer viscosity reducer and a preparation method thereof. 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-propane sulfonic acid, methacrylic acid, maleic anhydride and water, the pH of the reaction system was adjusted to 8 using a 60% mass concentration NaOH solution, and then APEG-400 was added thereto and mixed, and nitrogen was introduced to deoxygenate;

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

[0070] Example 3

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

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

[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% mass concentration NaOH solution, and then APEG-300 was added thereto and mixed, and nitrogen was introduced to deoxygenate;

[0075] After the temperature of the reaction system was raised to 50° C., ethyl xanthate and potassium persulfate were added to the reaction system, and the reaction was continued with stirring for 2 hours, and then the system was fully washed with anhydrous ethanol, dried, and crushed to obtain the branched polymer viscosity reducer.

[0076] Example 4

[0077] This embodiment provides a branched polymer viscosity reducer and a preparation method thereof. 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% mass concentration NaOH solution, and then APEG-300 was added thereto and mixed, and nitrogen was introduced to deoxygenate;

[0081] After the temperature of the reaction system was raised to 45° C., ethyl xanthate and potassium persulfate were added to the reaction system, and the reaction was continued with stirring for 3 hours, and then the system was fully washed with anhydrous ethanol, dried, and crushed to obtain the branched polymer viscosity reducer.

[0082] Example 5-Example 9

[0083] Examples 5 to 9 respectively provide a branched polymer viscosity reducer and a preparation method thereof, which differ from Example 1 only in that the raw material compositions of the branched polymer viscosity reducer are different:

[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 embodiment: 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 shown in Example 1.

[0090] Example 10-Example 13

[0091] Examples 10 to 13 respectively provide a branched polymer viscosity reducer and a preparation method thereof, which differ from Example 5 only in that the amount of ethyl xanthate in the raw materials for preparing the branched polymer viscosity reducer is different:

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

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

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

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

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

[0097] Comparative Example 1-Comparative Example 5

[0098] Comparative Examples 1 to 5 respectively provide a branched polymer viscosity reducer and a preparation method thereof, which differ from Example 5 only in that the raw material compositions of the branched polymer viscosity reducer are different:

[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: acrylic acid was not used, the amount of ethyl xanthate was 280 mg, and the amount of potassium persulfate was 156 mg;

[0101] In Comparative Example 3: no maleic anhydride was 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] In Comparative Example 5: ethyl xanthate was not used;

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

[0105] Comparative Example 6

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

[0107] The performance of the viscosity reducers provided in the above examples and comparative examples was characterized, and the specific test method was as follows:

[0108] The temperature resistance and viscosity reduction performance of the viscosity reducers provided in the above embodiments and comparative examples in bentonite slurry were evaluated. After aging at 240°C for 16 hours, the rheological properties of each slurry were measured using a six-speed viscometer in accordance with the provisions of "SYT 5695-2017 Zwitterionic Polymers for Drilling Fluid Viscosity Reducers". The composition of the experimental slurry is as follows:

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

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

[0111] The basic formula and experimental formula systems were aged at 240℃ for 16h before and after. The viscosity was tested under the conditions of , and the viscosity reduction rate was calculated;

[0112] The evaluation results are shown in Table 1. The viscosity reduction rate was tested according to the provisions of "SYT 5695-2017 Zwitterionic polymers for viscosity reducers for drilling fluids";

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

[0114] Molecular weight distribution index: The molecular weight distribution index was measured 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] It can be seen from the above content that the present invention designs the raw materials for preparing the polymer viscosity reducer, and obtains a branched polymer viscosity reducer with a specific structure by using 2-acrylamide-2-methyl-1-propane sulfonic acid, organic acid, maleic anhydride and propenyl alcohol polyoxyethylene ether. The branched polymer viscosity reducer has a lower weight average molecular weight and a narrower molecular weight distribution (≤1.33); adding a branched polymer viscosity reducer sample with a mass concentration of 0.3% to the water-based drilling fluid can significantly reduce the drilling fluid φ100 viscosity, and can still maintain a high viscosity reduction rate after aging at a high temperature of 240°C for 16 hours, the viscosity reduction rate at room temperature is ≥72.9%, specifically 72.9-79.2%, and after aging at a high temperature (240°C) 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 the present invention is simple, the reaction conditions are mild, the cost is low, and it is suitable for industrial production and use.

[0120] It can be seen from the contents of Examples 5 to 9 that the present invention can further improve the comprehensive performance of the branched polymer viscosity reducer by controlling the amount of each component in the raw material organic monomer for the preparation of the branched polymer viscosity reducer within a specific range, and the prepared branched polymer viscosity reducer has a lower weight-average molecular weight and a narrower molecular weight distribution; adding a branched polymer viscosity reducer sample with a mass concentration of 0.3% to the water-based drilling fluid can significantly reduce the drilling fluid φ100 viscosity, and can still maintain a high viscosity reduction rate after aging at high temperature 240°C 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°C) for 16 hours, the viscosity reduction rate is ≥67.8%, specifically 67.8~76.9%.

[0121] It can be seen from the contents of Examples 5 and 10-13 that the present invention can further improve the comprehensive performance of the branched polymer viscosity reducer by controlling the amount of the chain transfer agent within a specific range.

[0122] It can be seen from the contents of Examples 1-13 and Comparative Examples 1-5 that the present invention prepares a branched polymer viscosity reducer with excellent performance by designing the raw materials for preparing the polymer viscosity reducer.

[0123] It can be seen from the contents of Examples 1-13 and Comparative Example 6 that the branched polymer viscosity reducer provided by the present invention has more excellent high temperature resistance.

[0124] In summary, the present invention designs the raw materials for preparing the polymer viscosity reducer, and obtains a branched polymer viscosity reducer with a specific structure by using 2-acrylamide-2-methyl-1-propane sulfonic acid, an organic acid, maleic anhydride and propenyl alcohol polyoxyethylene ether. The branched polymer viscosity reducer has a lower weight-average molecular weight, a narrower molecular weight distribution and better high temperature resistance. At the same time, 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.

[0125] The applicant declares that the present invention illustrates the detailed process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present 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-acrylamide-2-methyl-1-propane sulfonic acid, organic acid, maleic anhydride and polyoxyethylene propylene alcohol ether.

2. The branched polymer viscosity reducer according to claim 1, characterized in that: Based on the mass percentage of the organic monomer as 100%, the mass percentage of the chain transfer agent is 0.5-1%; Preferably, based on the mass percentage of the organic monomer being 100%, the mass percentage of the initiator is 0.3-0.5%; Preferably, the molar ratio of the 2-acrylamide-2-methyl-1-propane sulfonic acid, the organic acid, maleic anhydride and the acryl alcohol polyoxyethylene ether is (2-3): (5-6): (2-3): (0.5-1).

3. The branched polymer viscosity reducer according to claim 1 or 2, characterized in that: The organic acid includes any one of acrylic acid, methacrylic acid, and itaconic acid, or a combination of at least two thereof; Preferably, the number average molecular weight of the polyoxyethylene propylene alcohol ether is ≤400; Preferably, the polyoxyethylene propylene glycol ether includes APEG-300 or APEG-400.

4. The branched polymer viscosity reducer according to any one of claims 1 to 3, characterized in that: The chain transfer agent includes any one of ethyl xanthate, potassium xanthate, and potassium butyl xanthate, or a combination of at least two thereof; Preferably, the initiator comprises any one of potassium persulfate, azobisisobutyronitrile or dibenzoyl peroxide, or a combination of at least two thereof; Preferably, the raw materials for preparing the branched polymer viscosity reducer further include a solvent; Preferably, the solvent comprises water; Preferably, based on 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%.

5. A method for preparing a branched polymer viscosity reducer as claimed in any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: After mixing 2-acrylamide-2-methyl-1-propane sulfonic acid, an organic acid, maleic anhydride and a solvent, adjusting the pH of the reaction system to 7-9, and then adding propylene alcohol polyoxyethylene ether thereto and mixing; Then, an initiator and a chain transfer agent are added to the reaction system to react and obtain the branched polymer viscosity reducer.

6. The preparation method according to claim 5, characterized in that: The base used to adjust the pH of the reaction system includes NaOH; Preferably, after adding the propylene alcohol polyoxyethylene ether and mixing, a post-treatment step is also included, and the post-treatment method includes: introducing nitrogen to deoxygenate.

7. The preparation method according to claim 5 or 6, characterized in that: When the initiator and chain transfer agent are added, the temperature of the reaction system is 40-50°C; Preferably, the reaction time is 2-3h; Preferably, the reaction further includes a post-treatment step; Preferably, the post-treatment method includes: washing, drying, and crushing; Preferably, the washing solvent comprises ethanol.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The preparation method of the branched polymer viscosity reducer specifically comprises the following steps: After mixing 2-acrylamide-2-methyl-1-propane sulfonic acid, an organic acid, maleic anhydride and a solvent, adjusting the pH of the reaction system to 7-9, then adding propylene alcohol polyoxyethylene ether thereto, mixing, and introducing nitrogen to deoxygenate; The temperature of the reaction system is raised to 40-50° C., an initiator and a chain transfer agent are added to the reaction system, and after reacting for 2-3 hours, the reaction system is washed, dried, and crushed to obtain the branched polymer viscosity reducer.

9. A use of the branched polymer viscosity reducer according to any one of claims 1 to 5, characterized in that: The branched polymer viscosity reducer is used to prepare water-based drilling fluid; Preferably, the water-based drilling fluid is used for deep well or ultra-deep well drilling.

10. The use according to claim 9, characterized in that: The mass concentration of the branched polymer viscosity reducer in the water-based drilling fluid is 0.2-0.5%.

Images