A method for preparing a hyperbranched polymer for drilling fluid and a drilling fluid

Abstract

This invention provides a method for preparing a hyperbranched polymer for drilling fluids, comprising: copolymerizing organic acid monomers, organic amide monomers, a first branching agent, a second branching agent, and a chain transfer agent under the action of a pH adjuster and a chain transfer agent to obtain a hyperbranched polymer for drilling fluids. The reversible addition-fragmentation chain transfer (RAFT) polymerization method provided by this invention employs a rapid polymerization process, using diene monomers, branching agents, and chain transfer agents to prepare a water-soluble, snowflake-like hyperbranched polymer filtration reducer with high polymerization rate and high conversion in an aqueous solution system. This double-layered branched structure exhibits good solubility, high rheological properties, non-crosslinking, and a large number of branched end groups. The resulting product has a narrow molecular weight distribution, good temperature resistance, and low viscosity effect. This invention also provides a drilling fluid.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, and particularly relates to a method for preparing hyperbranched polymers for drilling fluids and a drilling fluid thereof. Background Technology

[0002] With increasingly complex formations encountered during drilling, deep and ultra-deep wells are becoming more common. In China, deep and ultra-deep wells drilled in the Tarim Basin, Junggar Basin, Sichuan Basin, and Qaidam Basin have reached temperatures exceeding 170℃. These high-temperature conditions place more stringent demands on drilling fluid performance. Filtration reducers are one of the key agents for ensuring drilling fluid performance, and their performance is crucial to the quality of the drilling fluid. Currently, the polymer filtration reducers used in the field are linear polymers, exhibiting a large viscosity effect at the same molecular weight. This makes it difficult to increase the dosage in high-density drilling fluids, and the anti-fouling ability and high-temperature stability of the drilling fluid are difficult to control.

[0003] Traditional polymeric filtration loss reducers are generally based on one or more monomers selected from 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, acrylamide, N-vinylacetamide, N-vinylpyrrolidone, and disubstituted amides, and are produced via aqueous solution polymerization. These polymers are all linear polymers, and although they possess some high-temperature resistance, they suffer from high viscosity, easy chain breakage, and weak resistance to degradation. While traditional polymeric filtration loss reducers can generally meet the temperature resistance requirements of drilling fluids in the field, they still exhibit significant viscosity effects, poor anti-fouling ability, and poor long-term high-temperature stability of the drilling fluid, making it difficult to meet the rheological and filtration loss control requirements of drilling fluids under high-temperature (200℃) and high-salt (saturated brine) conditions. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for preparing hyperbranched polymers for drilling fluids and a drilling fluid thereof. The reversible addition-fracture chain transfer (RAFT) polymerization method provided by this invention employs a rapid polymerization process, using diene monomers, branching agents, and chain transfer agents to prepare a water-soluble snowflake-like hyperbranched polymer filtration reducer in an aqueous system with high polymerization rate and high conversion. The double-layer branched structure has good solubility, high rheological properties, and is non-crosslinked, while also having a large number of branched end groups. The resulting product has a narrow molecular weight distribution, good temperature resistance, and low viscosity effect, thus solving the technical problem of high viscosity effect, limited dosage of treatment agents, and difficulty in simultaneously achieving rheological properties and suspension stability in high-temperature and high-density drilling fluids.

[0005] This invention provides a method for preparing hyperbranched polymers for drilling fluids, comprising:

[0006] Organic acid monomers, organic amide monomers, a first branching agent, a second branching agent, and a chain transfer agent are copolymerized in water under the action of a pH adjuster and an initiator to obtain a hyperbranched polymer for drilling fluid.

[0007] Preferably, the organic acid monomer is selected from one or two of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 2-acryloyloxy-2-methylpropanesulfonic acid.

[0008] Preferably, the organic amide monomer is selected from one or two of acrylamide, N,N-dimethylacrylamide and N,N-diethylacrylamide.

[0009] Preferably, the first branching agent is selected from one or both of pentaerythritol and bispentaerythritol.

[0010] Preferably, the second branching agent is selected from one or more of N,N-methylenebisacrylamide, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate.

[0011] Preferably, the chain transfer agent is selected from one or more of ethyl xanthoxyacetic acid, potassium xanthate, 4-cyanopentanoic acid dithiobenzoate and (3-benzyl mercaptothiocarbonylthio)propionic acid.

[0012] Preferably, the initiator is selected from one or more of potassium persulfate, ammonium persulfate, and hydrogen peroxide.

[0013] Preferably, the mass ratio of the organic acid monomer, the organic amide monomer, the first branching agent, the second branching agent, and the chain transfer agent is (42-57):(43-58):(0.1-0.2):(0.02-0.1):(0.4-1);

[0014] The initiator is 0.2% to 0.5% of the total mass of organic acid monomers and organic amide monomers.

[0015] Preferably, the temperature of the copolymerization reaction is 10–80°C.

[0016] This invention provides a drilling fluid comprising: a hyperbranched polymer for drilling fluid prepared by the method described above.

[0017] Compared with existing technologies, the hyperbranched polymer powder flow pattern regulator and filtration loss reducer prepared by this invention has good water solubility. It is prepared by a rapid aqueous solution polymerization method, which is easy to control, simple to operate, and produces stable product quality without environmental pollution. Because this invention uses reversible addition-fragmentation chain transfer polymerization (RAFT polymerization), a chain transfer agent with a high chain transfer constant is added to the traditional radical polymerization system to achieve the purpose of "living" polymerization. During the polymerization process, the primary free radicals generated by the decomposition of the initiator rapidly transfer to the RAFT chain transfer agent, generating star-shaped multifunctional free radicals. At the same time, linear macromolecular RAFT chain transfer agents are generated. The star-shaped multifunctional free radicals undergo a growth reaction to obtain star-shaped or snowflake-shaped hyperbranched polymers. This branched polymer has low viscosity effect and good temperature resistance. It can be used to adjust the rheology of high-temperature and high-density drilling fluids, meeting the performance requirements of high-temperature and high-density drilling fluids where rheology, suspension stability, and filtration loss are difficult to balance simultaneously. Experimental results show that when the hyperbranched polymer prepared in this invention is added at a concentration of 1.5%, the API filtration loss after aging in composite brine slurry at 150℃ for 16h is less than 15.0mL, and the apparent viscosity is 7.5~15mPa·s; after aging in saturated brine slurry at 200℃ for 16h, the API filtration loss is 15.0mL. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a method for preparing hyperbranched polymers for drilling fluids, comprising:

[0020] Organic acid monomers, organic amide monomers, a first branching agent, a second branching agent, and a chain transfer agent are copolymerized in water under the action of a pH adjuster and an initiator to obtain a hyperbranched polymer powder for drilling fluid.

[0021] In this invention, the preferred method for preparing the hyperbranched polymer powder for drilling fluid includes:

[0022] After mixing organic acid monomers, organic amide monomers, a first branching agent, a second branching agent, and a chain transfer agent, the pH value is adjusted, and an initiator is added under stirring. The copolymerization reaction is carried out in water to obtain a hyperbranched polymer powder for drilling fluid.

[0023] In this invention, the pH value is preferably 6 to 11, more preferably 7 to 10, and most preferably 8 to 9.

[0024] In this invention, the organic acid monomer is preferably selected from one or two of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and 2-acryloyloxy-2-methylpropanesulfonic acid;

[0025] In this invention, the organic amide monomer is preferably selected from one or two of acrylamide, N,N-dimethylacrylamide and N,N-diethylacrylamide.

[0026] In this invention, the first branching agent is preferably selected from one or both of pentaerythritol and bispentaerythritol.

[0027] In this invention, the second branching agent is preferably selected from one or more of N,N-methylenebisacrylamide, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate.

[0028] In this invention, the chain transfer agent is preferably selected from one or more of ethyl xanthoxyacetic acid, potassium xanthate, 4-cyanopentanoic acid dithiobenzoate and (3-benzyl mercaptothiocarbonylthio)propionic acid.

[0029] In this invention, the initiator is preferably selected from one or more of potassium persulfate, ammonium persulfate and hydrogen peroxide.

[0030] In this invention, the pH adjuster is preferably selected from one or more of sodium hydroxide and potassium hydroxide.

[0031] In this invention, the preferred mass ratio of the organic acid monomer, organic amide monomer, first branching agent, second branching agent, and chain transfer agent is (42-57):(43-58):(0.1-0.2):(0.02-0.1):(0.4-1), more preferably (48-52):(48-52):(0.13-0.17):(0.04-0.06):(0.5-0.8), and most preferably 50:50:0.15:0.05:0.6.

[0032] In this invention, the mass of the initiator is preferably 0.2% to 0.5% of the total mass of organic acid monomers and organic amide monomers, more preferably 0.3% to 0.4%.

[0033] In this invention, the amount of pH adjuster is preferably such that the pH value of the copolymerization reaction system is 6-11, more preferably 7-10, and most preferably 8-9.

[0034] In this invention, the ratio of the mass of water to the total mass of organic acid monomers and organic amide monomers is preferably (24-30):(70-76), more preferably (24-26):(73-76), and most preferably 25:75.

[0035] In this invention, the temperature of the copolymerization reaction is preferably 10-80°C, more preferably 20-70°C, even more preferably 30-60°C, and most preferably 40-50°C.

[0036] In this invention, the copolymerization reaction time is preferably 5 to 60 minutes, more preferably 10 to 50 minutes, even more preferably 20 to 40 minutes, and most preferably 30 minutes.

[0037] In this invention, the polymerization reaction preferably further includes the following steps after completion:

[0038] The obtained reaction products are crushed and pulverized to obtain hyperbranched powdered polymer filtration loss reducer.

[0039] This invention provides a drilling fluid comprising: a hyperbranched polymer for drilling fluid prepared by the method described above.

[0040] The present invention does not impose any special restrictions on the composition of the drilling fluid. Those skilled in the art can formulate drilling fluids with suitable compositions according to actual needs. The hyperbranched powdered polymer used in the drilling fluid can be used as a drilling fluid filtration reducer.

[0041] In this invention, the mass content of the hyperbranched polymer powder for drilling fluid in the drilling fluid is preferably 1.5% to 2.5%, more preferably 1.8% to 2.2%, and most preferably 2%.

[0042] This invention provides a method for preparing hyperbranched polymer powder filtration reducer for drilling fluids using a reversible addition-fracture chain transfer (RAFT) polymerization method. During RAFT polymerization, a special chain transfer agent with a high chain transfer constant is used. This chain transfer agent undergoes reversible addition-fracture chain transfer with the growing free radicals, maintaining the activity of the free radicals and achieving controllable and "active" free radical polymerization. Under the action of the bibranching agent, a star-shaped or snowflake-shaped branched structure is achieved. Simultaneously, an aqueous solution rapid polymerization process is employed, which is simple to operate, has a high monomer conversion rate, and yields a low-molecular-weight, water-soluble hyperbranched polymer for drilling fluids with low viscosity effect, good temperature resistance, and strong filtration reduction capability.

[0043] Example 1

[0044] Add 35g of water to a reaction flask equipped with a stirrer, then add 8g of acidic monomers acrylic acid and 34g of 2-acrylamido-2-methylpropanesulfonic acid. Stir until completely dissolved, then adjust the pH to 9.5 with a 40% sodium hydroxide solution. Add 58g of acrylamide, 0.1g of pentaerythritol, 0.02g of N,N-methylenebisacrylamide, and 0.4g of ethyl xanthoxyacetic acid and stir until dissolved. Transfer the reaction mixture of the above monomers to a polypropylene plastic container, add 0.2g of ammonium persulfate while stirring, stir evenly, and let the reaction stand for 20 minutes. The polymerization initiation temperature is 20℃. A large amount of vapor is released during the polymerization process. Finally, a porous elastomer is obtained. The obtained porous elastomer is crushed and pulverized to obtain a low molecular weight hyperbranched polymer flow pattern regulator and filtration loss reducer.

[0045] The product prepared in Example 1 was prepared into an aqueous solution with a mass concentration of 1%, and the preparation method was in accordance with the method in 4.8 of Q / SH10250523-2008. The apparent viscosity of the 1% aqueous solution was 15 mPa·s.

[0046] Example 2

[0047] Add 30g of water to a reaction flask equipped with a stirrer, then add 8g of acidic monomers acrylic acid and 34g of 2-acrylamido-2-methylpropanesulfonic acid. Stir until completely dissolved, then adjust the pH to 9.0 with a 40% sodium hydroxide solution. Next, add 58g of acrylamide, 0.2g of pentaerythritol, 0.1g of N,N-methylenebisacrylamide, and 1g of ethyl xanthoxyacetic acid and stir until dissolved. Transfer the reaction mixture of the above monomers to a polypropylene plastic container, add 0.5g of ammonium persulfate while stirring, stir evenly, and let stand for 30 minutes. The polymerization initiation temperature is 25℃. A large amount of vapor is released during the polymerization process. Finally, a porous elastomer is obtained. The obtained porous elastomer is crushed and pulverized to obtain a hyperbranched polymer powder flow modifier and filtration loss reducer.

[0048] The product prepared in Example 2 was prepared into an aqueous solution with a mass concentration of 1%, and the preparation method was in accordance with the method in 4.8 of Q / SH10250523-2008. The apparent viscosity of the 1% aqueous solution was 8.5 mPa·s.

[0049] Example 3

[0050] Add 38g of water to a reaction flask equipped with a stirrer, then add 11g of acidic monomers acrylic acid and 46g of 2-acrylamido-2-methylpropanesulfonic acid. Stir until completely dissolved, then adjust the pH to 10.0 with a 40% sodium hydroxide solution. Then add 43g of acrylamide, 0.15g of pentaerythritol, 0.04g of N,N-methylenebisacrylamide, and 0.5g of ethyl xanthoxyacetic acid and stir until dissolved. Transfer the reaction mixture of the above monomers to a polypropylene plastic container, add 0.3g of ammonium persulfate while stirring, stir evenly, and let stand for 30 minutes. The initial temperature of the polymerization reaction is 30℃. Finally, a porous elastomer is obtained. The obtained porous elastomer is crushed and pulverized to obtain a hyperbranched polymer powder flow modifier and filtration loss reducer.

[0051] The product prepared in Example 3 was prepared into an aqueous solution with a mass concentration of 1%, and the preparation method was in accordance with the method in 4.8 of Q / SH10250523-2008. The apparent viscosity of the 1% aqueous solution was 11 mPa·s.

[0052] Example 4

[0053] Add 32g of water to a reaction flask equipped with a stirrer, then add 8g of acidic monomers acrylic acid and 34g of 2-acrylamido-2-methylpropanesulfonic acid. Stir until completely dissolved, then adjust the pH to 10.0 with a 40% sodium hydroxide solution. Next, add 58g of acrylamide, 0.2g of dipentaerythritol, 0.1g of N,N-methylenebisacrylamide, and 1g of ethyl xanthoxyacetic acid and stir until dissolved. Transfer the reaction mixture of the above monomers to a polypropylene plastic container, add 0.5g of ammonium persulfate while stirring, stir evenly, and let stand for 20 minutes. The initial temperature of the polymerization reaction is 25℃. Finally, a porous elastomer is obtained. The obtained porous elastomer is crushed and pulverized to obtain a hyperbranched polymer powder flow pattern regulator and filtration loss reducer.

[0054] The product prepared in Example 4 was prepared into an aqueous solution with a mass concentration of 1%, and the preparation method was in accordance with the method in 4.8 of Q / SH10250523-2008. The apparent viscosity of the 1% aqueous solution was 7.5 mPa·s.

[0055] Example 5

[0056] Add 30g of water to a reaction flask equipped with a stirrer, then add 8g of acidic monomers acrylic acid and 34g of 2-acrylamido-2-methylpropanesulfonic acid. Stir until completely dissolved, then adjust the pH to 11.0 with a 40% sodium hydroxide solution. Next, add 58g of acrylamide, 0.2g of dipentaerythritol, 0.1g of N,N-methylenebisacrylamide, and 1g of 4-cyanopentanoic acid dithiobenzoate and stir until dissolved. Transfer the reaction mixture of the above monomers to a polypropylene plastic container, add 0.5g of ammonium persulfate while stirring, stir evenly, and let stand for 20 minutes. The initial temperature of the polymerization reaction is 30℃. Finally, a porous elastomer is obtained. The obtained porous elastomer is crushed and pulverized to obtain a hyperbranched polymer powder flow pattern regulator and filtration loss reducer.

[0057] The product prepared in Example 5 was prepared into an aqueous solution with a mass concentration of 1%; the preparation method was in accordance with the method in 4.8 of Q / SH10250523-2008, and the apparent viscosity of the 1% aqueous solution was 12 mPa·s.

[0058] Performance testing

[0059] Evaluation of the temperature resistance and filtration loss reduction effect of the products prepared in the examples:

[0060] 1. Preparation of composite saline slurry

[0061] The preparation of composite brine slurry is based on the standard Q / SH1025 0523-2008 General Technical Conditions for Synthetic Polymers in Drilling Fluids. Measure 350 mL of distilled water into a cup, add 15.75 g of sodium chloride, 1.75 g of anhydrous calcium chloride, and 4.6 g of magnesium chloride. After they dissolve, add 52.5 g of calcium bentonite and 3.15 g of anhydrous sodium carbonate. Stir at high speed for 20 min, stopping at least twice during this period to scrape off the clay adhering to the wall of the container. Cure in a sealed container at 24℃±3℃ for 24 h to obtain the composite brine-based slurry.

[0062] 2. Preparation of saturated brine slurry

[0063] Measure 400 mL of distilled water into a cup, add 16 g of bentonite and 0.48 g of anhydrous sodium carbonate, stir at high speed for 20 min, stopping at least twice during the process to scrape off the clay adhering to the wall of the container, and cure in a sealed container at 24℃±3℃ for 24 h for later use to obtain the base slurry.

[0064] Add 16g of sodium chloride to the cured 4% base slurry, stir at high speed for 20 minutes, stopping at least twice during the process to scrape off the clay adhering to the wall of the container, and cure in a sealed container at 24℃±3℃ for 24 hours to obtain saturated brine base slurry.

[0065] Performance testing

[0066] (1) Filtration loss reduction performance

[0067] The product prepared in Example 4 was added to the cured composite brine slurry and saturated brine slurry, and stirred at high speed for 5 min. After aging at 150℃ / 16h and 200℃ / 16h respectively, the apparent viscosity of the drilling fluid was determined according to the provisions of 6.3 in GB / T16783.1-2006, and the room temperature medium pressure filtration loss of the drilling fluid was determined according to the provisions of 7.2. The temperature was 24℃±3℃ and the pressure was 690KPa. The test results are shown in Table 1.

[0068] Table 1 Evaluation results of filtration loss reduction performance of the snowflake-shaped hyperbranched polymer prepared in Example 4

[0069] formula Polymer addition AV / mPa·s PV / mPa·s YP / Pa FL / mL pH Composite brine slurry 1.5％ 3.0 3.0 0 10.0 7.0 Saturated brine slurry 2.0％ 12.0 9.0 3.0 12.6 7.0

[0070] The results showed that with the increase of hyperbranched polymer dosage, the apparent viscosity gradually increased and the API filtration loss gradually decreased. When the hyperbranched polymer dosage was 1.5%, the apparent viscosity of the composite brine slurry after aging at 150℃ for 16h was 3.0 mPa·s and the API filtration loss was 10.0 mL. When the dosage in the saturated brine slurry was 2.0%, the apparent viscosity after aging at 200℃ for 16h was 12.0 mPa·s and the API filtration loss was 12.6 mL. This indicates that the hyperbranched polymer has good temperature resistance, salt resistance, and filtration loss reduction capabilities, while also exhibiting a low viscosity effect, demonstrating the technical advantages of the hyperbranched polymer.

[0071] The performance of the products prepared in Examples 1 to 5 was tested according to the method described in the above technical solution, and the test results are shown in Table 2.

[0072] Table 2 Performance test results of the snowflake-shaped hyperbranched polymer powder prepared in the examples

[0073]

[0074] Snowflake-like hyperbranched polymers exhibit lower viscosity effects and better temperature and salt resistance. Under the condition of comparable filtration loss in composite brine slurry, they show better filtration loss reduction performance after aging at 200℃ / 16h in saturated brine slurry, with API filtration loss controlled at 15mL.

[0075] This invention provides a method for preparing hyperbranched polymer powder filtration reducer for drilling fluids using a reversible addition-fracture chain transfer (RAFT) polymerization method. During RAFT polymerization, a special chain transfer agent with a high chain transfer constant is used. This chain transfer agent undergoes reversible addition-fracture chain transfer with the growing free radicals, maintaining the activity of the free radicals and achieving controllable and "active" free radical polymerization. Under the action of the bibranching agent, a star-shaped or snowflake-shaped branched structure is achieved. Simultaneously, an aqueous solution rapid polymerization process is employed, which is simple to operate, has a high monomer conversion rate, and yields a low-molecular-weight, water-soluble hyperbranched polymer for drilling fluids with low viscosity effect, good temperature resistance, and strong filtration reduction capability.

[0076] While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be readily understood by those skilled in the art that various changes may be made to suit particular circumstances, materials, compositions, substances, methods, or processes to the objectives, spirit, and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A method for preparing a hyperbranched polymer for drilling fluids, comprising: Organic acid monomers, organic amide monomers, a first branching agent, a second branching agent, and a chain transfer agent are copolymerized in water under the action of a pH adjuster and an initiator to obtain a hyperbranched polymer for drilling fluid. The organic acid monomer is selected from one or two of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 2-acryloyloxy-2-methylpropanesulfonic acid; the organic amide monomer is selected from one or two of acrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide; the first branching agent is selected from one or two of bispentaerythritol and pentaerythritol; the second branching agent is selected from one or more of N,N-methylenebisacrylamide, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate. The chain transfer agent is selected from one or more of ethyl xanthoxyacetic acid, potassium xanthate, 4-cyanopentanoic acid dithiobenzoate, and (3-benzyl mercaptothiocarbonylthio)propionic acid; the initiator is selected from one or more of potassium persulfate, ammonium persulfate, and hydrogen peroxide; the copolymerization temperature is 10~80℃; and the copolymerization time is 5~60 minutes.

2. The method according to claim 1, characterized in that, The mass ratio of the organic acid monomer, the organic amide monomer, the first branching agent, the second branching agent, and the chain transfer agent is (42~57):(43~58):(0.1~0.2):(0.02~0.1):(0.4~1). The initiator is 0.2% to 0.5% of the total mass of organic acid monomers and organic amide monomers.

3. A drilling fluid, comprising: The hyperbranched polymer for drilling fluid prepared by the method of claim 1.

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