Environment-friendly salt-resistant temperature-resistant fluid loss additive for drilling fluid and preparation method thereof

Abstract

The application belongs to the technical field of oil exploitation, and particularly relates to an environment-friendly salt-resistant temperature-resistant fluid loss additive for drilling fluid and a preparation method thereof. The fluid loss additive is composed of the following components in mass: 20-30 parts of acrylic ester polymer, 100-120 parts of composite modified montmorillonite, 3-5 parts of isopropyl palmitate and 150-200 parts of water; the acrylic ester polymer is prepared by polymerization reaction of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone. The prepared fluid loss additive has good salt resistance, temperature resistance and excellent fluid loss effect.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluids and its preparation method. Background Technology

[0002] Currently, oil and gas exploration and development are continuously advancing towards deep wells, ultra-deep wells, horizontal wells with extended reach, and complex salt-gypsum formations. The temperature and salinity of the drilling environment are significantly increasing. Therefore, the rheological properties and suspension properties of drilling fluids directly determine drilling efficiency and safety. Cutting agents are key additives that ensure the core performance of drilling fluids, helping to carry cuttings and stabilize the wellbore by increasing the shear force of the drilling fluid. Drilling fluids can be divided into water-based drilling fluids and oil-based drilling fluids.

[0003] Water-based drilling fluids are commonly used in shallow wells, medium-deep wells, conventional vertical wells, and areas with high environmental protection requirements, such as farmland and water source protection areas. They are particularly suitable for formations with good stability, such as sandstone and carbonate rocks. However, water-based drilling fluids have limited resistance to temperature and salt, and are gradually failing to meet the performance requirements for dealing with complex downhole conditions. Compared with water-based drilling fluids, oil-based drilling fluids have advantages such as better anti-collapse effect and stronger anti-pollution ability, and can be used in complex working conditions such as deep / ultra-deep wells and high-salt calcium formations.

[0004] Chinese patent application CN111748326A discloses a cutting agent for biodiesel-based drilling fluid and its preparation method. The raw materials for the cutting agent include 100 to 200 parts of organic clay, 3 to 8 parts of polyamine, and 100 to 200 parts of water by weight. The core of this scheme is melamine-modified organic clay, which mainly relies on the hydrogen bonding between organic clay and melamine to form a loose network. This network has insufficient support and poor stability, and cannot effectively suspend barite and carry rock cuttings. It is prone to insufficient wellbore cleanliness and stuck pipe risk, and cannot cope with complex working conditions such as deep wells, high salt and calcium, and multiple base fluid types. Summary of the Invention

[0005] Existing cutting fluids have a loose network structure and poor support. To solve this problem, this invention provides an environmentally friendly salt-resistant and temperature-resistant cutting fluid for drilling fluids and its preparation method.

[0006] To achieve the objectives of this invention, the following technical solution is adopted:

[0007] In a first aspect, the present invention provides an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluids, comprising the following components in parts by weight:

[0008] 20-30 parts of acrylate polymer, 100-120 parts of composite modified montmorillonite, 3-5 parts of isopropyl palmitate, and 150-200 parts of water;

[0009] The acrylate polymer is prepared by polymerization of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone.

[0010] By adopting the above technical solution, the acrylate polymer molecular chains are adsorbed onto the surface of the composite modified montmorillonite sheets, which not only promotes the dispersion and expansion of the composite modified montmorillonite sheets, but also builds an organic network through the molecular chain entanglement structure; montmorillonite provides inorganic skeleton support, strengthens network rigidity, and improves the dynamic shear force of the system; isopropyl palmitate can promote better compatibility and combination between the acrylate polymer and the montmorillonite system, and improve the uniformity of the system.

[0011] The method for preparing the acrylate polymer includes the following steps:

[0012] (1a) Mix polyvinyl alcohol, sodium hydrogen phosphate and water evenly to obtain a dispersant solution; mix benzoyl peroxide and acetone evenly to obtain an initiator solution;

[0013] (1b) Styrene, methyl methacrylate and octadecyl acrylate are mixed evenly to obtain mixture 1; 2-acrylamide-2-methylpropanesulfonic acid is mixed evenly with water, the pH is adjusted to 7-8, N-vinylpyrrolidone and N,N'-methylenebisacrylamide are added and mixed evenly to obtain mixture 2.

[0014] (1c) Under anaerobic conditions, mix mixture 1, mixture 2 and dispersant solution evenly, add initiator solution, heat to 75-80℃ and react for 3-4 hours, then heat to 90-95℃ and react for 1-2 hours, cool, filter, wash, dry and sieve to obtain acrylate polymer.

[0015] By adopting the above technical solution, the sulfonic acid groups of 2-acrylamido-2-methylpropanesulfonic acid in the acrylate polymer form a strong electrostatic repulsion effect, inhibiting the destruction of the molecular network by salt ions such as calcium and magnesium, thereby maintaining shear force; styrene and methyl methacrylate provide a rigid polymer backbone, increasing the glass transition temperature of the polymer, making it less prone to chain segment softening at high temperatures, thus maintaining structural integrity; the cyclic structure of N-vinylpyrrolidone has good rigidity and is resistant to hydrolysis, and together with 2-acrylamido-2-methylpropanesulfonic acid, it ensures the long-term stability of the acrylate polymer in high-temperature environments.

[0016] Furthermore, the ratio of polyvinyl alcohol, styrene, sodium hydrogen phosphate and water is (1.5-2)g∶(35-40)g∶(0.5-0.6)g∶(220-240)mL.

[0017] By adopting the above technical solution, polyvinyl alcohol is used as a dispersant and sodium hydrogen phosphate is used as a pH adjuster. By adjusting their dosage ratio, the dispersion effect is optimized, ensuring the stable progress of the polymerization reaction.

[0018] Furthermore, the amount of benzoyl peroxide used is 0.4%-0.6% of the total mass of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone; the ratio of benzoyl peroxide to acetone is 1g:(25-30)mL.

[0019] By adopting the above technical solution, benzoyl peroxide decomposes free radicals and initiates monomer copolymerization. At this dosage, the reactivity is matched with that of monomers such as styrene, which can provide sufficient free radicals, avoid insufficient or excessive initiation, and ensure the stability of the polymerization reaction rate.

[0020] Further, in step (1b), the amount of N,N'-methylenebisacrylamide used is 0.05%-0.15% of the total mass of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone.

[0021] By adopting the above technical solution, N,N'-methylenebisacrylamide is used as a crosslinking agent for the synthesis of acrylate polymers. A three-dimensional crosslinked network is constructed through the copolymerization reaction of the bisacrylamide groups with the double bonds of each monomer of styrene. The dosage of 0.05%-0.15% can control the degree of polymer crosslinking within the optimal range. This can enhance the molecular chain entanglement ability through the network structure and improve the dynamic shear force of the cutting agent. At the same time, it avoids the problem of loose network structure of acrylate polymers and reduced cutting effect caused by insufficient crosslinking.

[0022] Further, in step (1b), the mass ratio of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone is (35-40):(25-30):(10-15):(8-12):(5-8).

[0023] By adopting the above technical solutions, the aromatic ring structure of styrene endows the acrylate polymer with excellent rigidity and temperature resistance, while the ester group structure of methyl methacrylate enhances the compatibility of the acrylate polymer with the composite modified montmorillonite. The reasonable ratio of the two strengthens the synergistic effect of the sizing process. The sulfonic acid group of 2-acrylamido-2-methylpropanesulfonic acid has strong hydrophilicity and salt resistance. The amide group of N-vinylpyrrolidone can improve the water solubility and adsorption of the polymer. The precise ratio at this dosage can ensure salt resistance and dispersibility. The long-chain alkyl group of octadecyl acrylate can optimize lubrication and steric hindrance at this dosage. At this mass ratio, the copolymerization rate and reactivity of each monomer are highly synergistic, resulting in outstanding salt resistance and strong temperature stability.

[0024] The preparation method of the composite modified montmorillonite includes the following steps:

[0025] (2a) Montmorillonite, dioctadecyl dimethyl ammonium chloride and water were mixed at 65-80℃ for 3-5h, centrifuged, washed, dried and ground to obtain quaternary ammonium salt modified montmorillonite;

[0026] (2b) Mix 3-aminopropyltriethoxysilane with an aqueous ethanol solution until homogeneous, adjust the pH to 4-5, add lignocellulose, ultrasonically stir at 50-60℃ for 2-3 hours, wash, and dry to obtain modified lignocellulose;

[0027] (2c) Mix the modified lignocellulose, quaternary ammonium salt modified montmorillonite with water evenly, stir ultrasonically, filter, transfer to a vacuum drying oven and heat-treat at 90-100℃ for 2 hours, wash, dry, grind, and obtain composite modified montmorillonite.

[0028] By adopting the above technical solution, the interlayer spacing is expanded through quaternary ammonium salt intercalation; the alkoxy group of 3-aminopropyltriethoxysilane is hydrolyzed to generate silanol groups, which condense with the hydroxyl groups on the surface of lignocellulose, introducing amino functional groups and endowing lignocellulose with bridging activity; the long-chain organic structure of modified lignocellulose can fill the interlayer gaps of montmorillonite, forming a steric hindrance effect and preventing the layers from re-stacking and agglomerating; at the same time, the amino groups introduced by silane modification form electrostatic repulsion with the surface charge of montmorillonite, further inhibiting agglomeration.

[0029] Furthermore, in step (2a), the mass ratio of montmorillonite to dioctadecyldimethylammonium chloride is (4-6):1.

[0030] By adopting the above technical solution, when the mass ratio is (4-6):1, the amount of quaternary ammonium salt is highly matched with the interlayer cation exchange capacity of montmorillonite, and the interlayer spacing of montmorillonite is stably expanded, providing sufficient space for subsequent composite of modified lignocellulose and adsorption of acrylate polymers.

[0031] Furthermore, in step (2b), the amount of 3-aminopropyltriethoxysilane used is 3%-5% of the mass of lignocellulose.

[0032] By adopting the above technical solution, the silane grafting efficiency is optimal at this dosage.

[0033] Further, in step (2c), the mass ratio of modified lignocellulose to quaternary ammonium salt modified montmorillonite is 1:(3.5-5).

[0034] By adopting the above technical solution, at this dosage, the modified lignocellulose and quaternary ammonium salt modified montmorillonite exhibit optimal structural synergy, balancing dispersibility and network support capacity. Modified lignocellulose, being a long-chain organic component, primarily functions to bridge montmorillonite layers and inhibit aggregation. Excessive use can weaken the inorganic framework support of montmorillonite, resulting in insufficient rigidity of the three-dimensional network structure and a decrease in the dynamic shear force of the shearing agent. Insufficient dosage leads to insufficient amino and hydroxyl active sites provided by modified lignocellulose, weakening the hydrogen bonding / entanglement with the acrylate polymer and diminishing the synergistic shearing effect.

[0035] Secondly, the present invention also provides a method for preparing the above-mentioned environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluids, comprising the following steps:

[0036] The composite modified montmorillonite is mixed evenly with water, and then acrylate polymer and isopropyl palmitate are added in sequence. The mixture is then degassed under vacuum, dried, pulverized, and sieved to obtain an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid.

[0037] By adopting the above technical solution, the composite modified montmorillonite is first mixed with water, and water is used as a dispersion medium to fully disperse the composite modified montmorillonite. Then, acrylate polymer and isopropyl palmitate are added in sequence. The additives are added after the system is evenly dispersed, which can selectively reduce the friction between particles and avoid premature addition that may affect the swelling of montmorillonite and polymer adsorption. The preparation method is simple and the product performance is stable.

[0038] In summary, the beneficial effects of this invention are:

[0039] (1) In this invention, an acrylate polymer and a composite modified montmorillonite are combined to form a composite network structure, which synergistically enhances the dynamic shear force of the system; the long-chain fatty acid structure of isopropyl palmitate can selectively reduce the interparticle friction and the entanglement density between polymer molecules, thereby reducing the plastic viscosity.

[0040] (2) In the preparation of acrylate polymers, styrene and methyl methacrylate provide network backbone support, which can inhibit the thermal oxidative degradation of molecular chains at high temperature and ensure dynamic shear force; octadecyl acrylate adjusts the flexibility of molecular chains to avoid the network structure being too brittle and easily broken at high temperature; 2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone enhance water solubility and adsorption, so that the polymer can be dispersed quickly; at the same time, the sulfonic acid groups introduced by the 2-acrylamide-2-methylpropanesulfonic acid monomer can effectively inhibit the destruction of molecular network by salt ions such as calcium and magnesium;

[0041] (3) This invention utilizes quaternary ammonium salt and lignocellulose to modify montmorillonite, thereby enhancing the salt and temperature resistance of the composite modified montmorillonite and making it suitable for complex geological environments. The hydrophobicity of montmorillonite modified with quaternary ammonium salt is enhanced, reducing the inhibition of lamellar expansion by calcium, magnesium and other salt ions. The organic segments of lignocellulose can coat the surface of montmorillonite to form a salt-resistant barrier. The synergistic effect of quaternary ammonium salt and amino groups enhances interfacial bonding and improves the thermal stability of montmorillonite. Attached Figure Description

[0042] Figure 1 The XRD patterns of this invention are shown below; curve a is the XRD pattern of montmorillonite, curve b is the XRD pattern of quaternary ammonium salt modified montmorillonite, and curve c is the XRD pattern of composite modified montmorillonite. Detailed Implementation

[0043] The technical solution of the present invention will be explained in detail below with reference to several representative embodiments.

[0044] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0045] Preparation Example 1

[0046] The preparation method of the acrylate polymer in this example includes the following specific steps:

[0047] (1a) Mix 1.5g polyvinyl alcohol, 0.55g sodium hydrogen phosphate and 230mL deionized water, heat to 80℃ and stir for 20min to obtain a dispersant solution; mix 0.38g benzoyl peroxide and 10mL acetone and stir for 10min to obtain an initiator solution;

[0048] (1b) Mix 36g styrene, 30g methyl methacrylate and 12g octadecyl acrylate and stir for 20min to obtain mixture 1; mix 10g 2-acrylamide-2-methylpropanesulfonic acid with 30mL water and stir for 10min, adjust pH to 8, add 6g N-vinylpyrrolidone and 0.11g N,N'-methylenebisacrylamide and stir for 15min to obtain mixture 2;

[0049] (1c) Under nitrogen conditions, mix liquid 1, mix liquid 2 and dispersant solution, stir for 30 min, add initiator solution, heat to 80℃ and react for 3 h, heat to 95℃ and react for 1 h, after the reaction is completed, cool to room temperature, filter, wash 3 times with distilled water and 3 times with anhydrous ethanol, dry the obtained solid under vacuum at 65℃ for 12 h, grind, pass through 100 mesh sieve to obtain acrylate polymer.

[0050] Preparation Example 2

[0051] The preparation method of the acrylate polymer in this example includes the following specific steps:

[0052] (1a) Mix 2g of polyvinyl alcohol, 0.6g of sodium hydrogen phosphate and 240mL of deionized water, heat to 80℃ and stir for 20min to obtain a dispersant solution; mix 0.45g of benzoyl peroxide and 13mL of acetone and stir for 10min to obtain an initiator solution;

[0053] (1b) Mix 38g styrene, 28g methyl methacrylate and 10g octadecyl acrylate and stir for 20min to obtain mixture 1; mix 8g 2-acrylamide-2-methylpropanesulfonic acid with 30mL water and stir for 10min, adjust pH to 8, add 5g N-vinylpyrrolidone and 0.13g N,N'-methylenebisacrylamide and stir for 15min to obtain mixture 2;

[0054] (1c) Under nitrogen conditions, mix liquid 1, mix liquid 2 and dispersant solution, stir for 30 min, add initiator solution, heat to 75℃ and react for 4 h, heat to 95℃ and react for 2 h, after the reaction is completed, cool to room temperature, filter, wash 3 times with distilled water and 3 times with anhydrous ethanol, dry the obtained solid under vacuum at 65℃ for 12 h, grind, pass through 100 mesh sieve to obtain acrylate polymer.

[0055] Preparation Example 3

[0056] The preparation method of the acrylate polymer in this example includes the following specific steps:

[0057] (1a) Mix 1.6g polyvinyl alcohol, 0.5g sodium hydrogen phosphate and 220mL deionized water, heat to 80℃ and stir for 20min to obtain a dispersant solution; mix 0.56g benzoyl peroxide and 14mL acetone and stir for 10min to obtain an initiator solution;

[0058] (1b) Mix 35g styrene, 25g methyl methacrylate and 15g octadecyl acrylate and stir for 20min to obtain mixture 1; mix 12g 2-acrylamide-2-methylpropanesulfonic acid with 30mL water and stir for 10min, adjust pH to 7, add 8g N-vinylpyrrolidone and 0.05g N,N'-methylenebisacrylamide and stir for 15min to obtain mixture 2;

[0059] (1c) Under nitrogen conditions, mix liquid 1, mix liquid 2 and dispersant solution, stir for 30 min, add initiator solution, heat to 75℃ and react for 3 h, heat to 90℃ and react for 2 h, after the reaction is completed, cool to room temperature, filter, wash 3 times with distilled water and 3 times with anhydrous ethanol, dry the obtained solid under vacuum at 65℃ for 12 h, grind, pass through 100 mesh sieve to obtain acrylate polymer.

[0060] Preparation Example 4

[0061] The preparation method of the acrylate polymer in this example includes the following specific steps:

[0062] (1a) Mix 1.8g polyvinyl alcohol, 0.6g sodium hydrogen phosphate and 240mL deionized water, heat to 80℃ and stir for 20min to obtain a dispersant solution; mix 0.46g benzoyl peroxide and 14mL acetone and stir for 10min to obtain an initiator solution;

[0063] (1b) Mix 40g styrene, 26g methyl methacrylate and 10g octadecyl acrylate and stir for 20min to obtain mixture 1; mix 8g 2-acrylamide-2-methylpropanesulfonic acid with 30mL water and stir for 10min, adjust pH to 7, add 8g N-vinylpyrrolidone and 0.07g N,N'-methylenebisacrylamide and stir for 15min to obtain mixture 2;

[0064] (1c) Under nitrogen conditions, mix liquid 1, mix liquid 2 and dispersant solution, stir for 30 min, add initiator solution, heat to 75℃ and react for 4 h, heat to 90℃ and react for 1 h, after the reaction is completed, cool to room temperature, filter, wash 3 times with distilled water and 3 times with anhydrous ethanol, dry the obtained solid under vacuum at 65℃ for 12 h, grind, pass through 100 mesh sieve to obtain acrylate polymer.

[0065] Preparation Example 5

[0066] The preparation method of this example of composite modified montmorillonite includes the following specific steps:

[0067] (2a) Add 50g of montmorillonite to 500mL of deionized water, stir for 30min, and adjust the pH to 8 to obtain dispersion 1; add 12.5g of dioctadecyldimethylammonium chloride to 200mL of deionized water, heat to 60℃ and stir for 1h to obtain a solution; slowly pour dispersion 1 into the solution, heat to 75℃ and stir for 5h at a stirring speed of 250rpm; transfer the reaction solution to a centrifuge tube, centrifuge at 5000rpm for 10min, discard the supernatant, collect the precipitate, and wash the precipitate repeatedly with deionized water until Cl is undetectable in the washing solution. -After the silver nitrate solution showed no white precipitate, it was washed twice with anhydrous ethanol, transferred to a vacuum drying oven and dried at 80°C for 12 hours, ground, and passed through a 200-mesh sieve to obtain quaternary ammonium salt modified montmorillonite.

[0068] (2b) 0.3 g of 3-aminopropyltriethoxysilane was added to a mixed solution of anhydrous ethanol and water, the pH was adjusted to 5, 10 g of lignocellulose was added, and the mixture was heated to 60 °C and ultrasonically stirred for 2 h. After the reaction was completed, the mixture was washed 3 times with anhydrous ethanol and transferred to a vacuum drying oven and dried at 60 °C for 12 h to obtain modified lignocellulose.

[0069] (2c) Add 17.5g of quaternary ammonium salt modified montmorillonite to 400mL of deionized water and ultrasonically disperse for 30min to obtain dispersion 2; add 5g of modified lignocellulose to dispersion 2, ultrasonically stir for 1h at room temperature, filter, transfer to a vacuum drying oven and heat-treat at 90℃ for 2h, wash 3 times with deionized water, transfer to a vacuum drying oven and dry at 60℃ for 12h, grind, and pass through a 200-mesh sieve to obtain composite modified montmorillonite.

[0070] XRD tests were performed on the montmorillonite, quaternary ammonium salt modified montmorillonite, and composite modified montmorillonite prepared in Preparation Example 5: Cu target, scanning range of 2θ = 1°-10°, scanning rate of 1° / min, and interlayer spacing calculated according to nλ = 2dsinθ (where n is 1 and λCu = 0.154 nm).

[0071] Figure 1 These are the XRD patterns of the present invention; wherein, curve a is the XRD pattern of montmorillonite, curve b is the XRD pattern of quaternary ammonium salt modified montmorillonite, and curve c is the XRD pattern of composite modified montmorillonite; from Figure 1 The interlayer spacing of montmorillonite, quaternary ammonium salt modified montmorillonite, and composite modified montmorillonite was calculated to be da=1.25nm, db=2.24nm, and dc=2.56nm, respectively, indicating that the interlayer spacing of modified montmorillonite increased.

[0072] Preparation Example 6

[0073] The preparation method of this example of composite modified montmorillonite includes the following specific steps:

[0074] (2a) Add 50g of montmorillonite to 500mL of deionized water, stir for 30min, adjust pH to 7 to obtain dispersion 1; add 10g of dioctadecyldimethylammonium chloride to 200mL of deionized water, heat to 60℃ and stir for 1h to obtain solution; slowly pour dispersion 1 into solution, heat to 65℃ and stir for 4h at a stirring speed of 250rpm; transfer the reaction solution to a centrifuge tube, centrifuge at 5000rpm for 10min, discard the supernatant, collect the precipitate, wash the precipitate repeatedly with deionized water until Cl- is not detected in the washing solution, i.e., there is no white precipitate in the silver nitrate solution, then wash twice with anhydrous ethanol, transfer to a vacuum drying oven and dry at 80℃ for 12h, grind, pass through a 200-mesh sieve to obtain quaternary ammonium salt modified montmorillonite;

[0075] (2b) 0.5 g of 3-aminopropyltriethoxysilane was added to a mixed solution of anhydrous ethanol and water, the pH was adjusted to 5, 10 g of lignocellulose was added, and the mixture was heated to 55 °C and ultrasonically stirred for 2 h. After the reaction was completed, the mixture was washed 3 times with anhydrous ethanol and transferred to a vacuum drying oven and dried at 60 °C for 12 h to obtain modified lignocellulose.

[0076] (2c) Add 22.5g of quaternary ammonium salt modified montmorillonite to 400mL of deionized water and ultrasonically disperse for 30min to obtain dispersion 2; add 5g of modified lignocellulose to dispersion 2, ultrasonically stir for 1h at room temperature, filter, transfer to a vacuum drying oven and heat-treat at 100℃ for 2h, wash 3 times with deionized water, transfer to a vacuum drying oven and dry at 60℃ for 12h, grind, and pass through a 200-mesh sieve to obtain composite modified montmorillonite.

[0077] Preparation Example 7

[0078] The preparation method of this example of composite modified montmorillonite includes the following specific steps:

[0079] (2a) Add 50g of montmorillonite to 500mL of deionized water, stir for 30min, adjust pH to 7 to obtain dispersion 1; add 8.5g of dioctadecyl dimethyl ammonium chloride to 200mL of deionized water, heat to 60℃ and stir for 1h to obtain solution; slowly pour dispersion 1 into solution, heat to 70℃ and stir for 3h at a stirring speed of 250rpm; transfer the reaction solution to a centrifuge tube, centrifuge at 5000rpm for 10min, discard the supernatant, collect the precipitate, wash the precipitate repeatedly with deionized water until Cl- is not detected in the washing solution, i.e. there is no white precipitate in the silver nitrate solution, then wash twice with anhydrous ethanol, transfer to a vacuum drying oven and dry at 80℃ for 12h, grind, pass through a 200-mesh sieve to obtain quaternary ammonium salt modified montmorillonite;

[0080] (2b) 0.35 g of 3-aminopropyltriethoxysilane was added to a mixed solution of anhydrous ethanol and water, the pH was adjusted to 4, 10 g of lignocellulose was added, and the mixture was heated to 55 °C and ultrasonically stirred for 3 h. After the reaction was completed, the mixture was washed 3 times with anhydrous ethanol and transferred to a vacuum drying oven and dried at 60 °C for 12 h to obtain modified lignocellulose.

[0081] (2c) Add 25g of quaternary ammonium salt modified montmorillonite to 400mL of deionized water and ultrasonically disperse for 30min to obtain dispersion 2; add 5g of modified lignocellulose to dispersion 2, ultrasonically stir for 1h at room temperature, filter, transfer to a vacuum drying oven and heat-treat at 95℃ for 2h, wash 3 times with deionized water, transfer to a vacuum drying oven and dry at 60℃ for 12h, grind, and pass through a 200-mesh sieve to obtain composite modified montmorillonite.

[0082] Example 1

[0083] An environmentally friendly, salt-resistant, and temperature-resistant cutting agent for drilling fluid, as described in this embodiment, is composed of the following components by mass:

[0084] 25g acrylate polymer, 100g composite modified montmorillonite, 5g isopropyl palmitate, 180g water;

[0085] The acrylate polymer was prepared by the preparation method of Preparation Example 1; the composite modified montmorillonite was prepared by the preparation method of Preparation Example 6.

[0086] The preparation method of an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to this embodiment includes the following specific steps:

[0087] Add water to the dispersion vessel, turn on the stirrer at 500 r / min, add the composite modified montmorillonite to the vessel, turn on the high-speed shear dispersion head, and shear disperse for 60 min; turn off the high-speed shear dispersion head, keep stirring in the vessel, add the acrylate polymer, turn on the shear dispersion head and disperse for 30 min; add isopropyl palmitate, turn off the shear dispersion head, and keep stirring; turn on the vacuum system, reduce the pressure to remove air bubbles from the system, turn off the vacuum, dry at 100℃ for 24 h, pulverize, and sieve to obtain an environmentally friendly salt-resistant and heat-resistant cutting agent for drilling fluid.

[0088] Example 2

[0089] An environmentally friendly, salt-resistant, and temperature-resistant cutting agent for drilling fluid, as described in this embodiment, is composed of the following components by mass:

[0090] 30g acrylate polymer, 110g composite modified montmorillonite, 4g isopropyl palmitate, 150g water;

[0091] The acrylate polymer was prepared by the preparation method of Preparation Example 1; the composite modified montmorillonite was prepared by the preparation method of Preparation Example 5.

[0092] The preparation method of an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid in this embodiment is the same as that in Embodiment 1.

[0093] Example 3

[0094] An environmentally friendly, salt-resistant, and temperature-resistant cutting agent for drilling fluid, as described in this embodiment, is composed of the following components by mass:

[0095] 30g acrylate polymer, 120g composite modified montmorillonite, 3g isopropyl palmitate, 200g water;

[0096] The acrylate polymer was prepared by the preparation method of Preparation Example 3; the composite modified montmorillonite was prepared by the preparation method of Preparation Example 6.

[0097] The preparation method of an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid in this embodiment is the same as that in Embodiment 1.

[0098] Example 4

[0099] An environmentally friendly, salt-resistant, and temperature-resistant cutting agent for drilling fluid, as described in this embodiment, is composed of the following components by mass:

[0100] 22g acrylate polymer, 115g composite modified montmorillonite, 3g isopropyl palmitate, 160g water;

[0101] The acrylate polymer was prepared by the preparation method of Preparation Example 2; the composite modified montmorillonite was prepared by the preparation method of Preparation Example 7.

[0102] The preparation method of an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid in this embodiment is the same as that in Embodiment 1.

[0103] Comparative Example 1

[0104] The difference from Example 1 is that the acrylate polymer in this comparative example was prepared by polymerization of styrene, methyl methacrylate, octadecyl acrylate and N-vinylpyrrolidone, while the rest is the same as in Example 1.

[0105] Comparative Example 2

[0106] The difference from Example 1 is that the acrylate polymer in this comparative example was obtained by copolymerizing styrene and methyl methacrylate in a mass ratio of 1:1, while all other aspects are the same as in Example 1.

[0107] Comparative Example 3

[0108] The difference from Example 1 is that the composite modified montmorillonite in this comparative example is obtained only through step (2a), and the rest is the same as in Example 1.

[0109] Comparative Example 4

[0110] The difference from Example 1 is that this comparative example uses an equal amount of montmorillonite instead of composite modified montmorillonite, while everything else is the same as in Example 1.

[0111] Comparative Example 5

[0112] The difference from Example 1 is that the amount of acrylate polymer used in this comparative example is 45g.

[0113] Related performance tests

[0114] Basic pulp formula: 80g5 # White oil + 2.5g primary emulsifier + 1.5g secondary emulsifier + 2g calcium oxide + 2g organic clay + 4g high-temperature filtration loss reducer + 20mL 30% calcium chloride aqueous solution + barite.

[0115] Experimental slurry preparation and testing: 2 wt% of the environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid prepared in Examples 1-4 and Comparative Examples 1-5 were added to the prepared base slurry. The mixture was stirred at high speed for 20 min, and the temperature resistance, salt resistance, plastic viscosity and cutting effect were tested. The test results are shown in Table 1.

[0116] Table 1 Test Results

[0117]

[0118] Comparing Comparative Example 1 with Example 1, it can be seen that the dynamic shear force retention rate in the high-salt-calcium environment is only 72.4%, which is significantly lower than that in Example 1. This proves that the sulfonic acid group of the 2-acrylamide-2-methylpropanesulfonic acid monomer is the key to the system's resistance to salt-calcium contamination. After its absence, the salt-calcium ions easily destroy the polymer-montmorillonite composite network, leading to a decrease in shearing performance.

[0119] Comparing Comparative Example 2 with Example 1, it can be seen that the dynamic shear force of this comparative example is only 22.7 Pa, which cannot effectively carry the weighting agent; the aging retention rate at 150℃ is 78.4%, and the salt resistance retention rate is 65.8%, which proves that the binary monomer lacks functional groups (2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone) and cannot be adapted to high salt and calcium working conditions.

[0120] Comparing Comparative Example 3 with Example 1, it can be seen that the dynamic shear force is lower than that of Example 1, and the temperature resistance and salt resistance retention rates are both <90%. This proves that the single quaternary ammonium salt modified montmorillonite lacks the bridging effect of lignocellulose, the lamellars are prone to agglomeration, and the ability to synergistically build a network with the polymer is weakened, resulting in a decrease in shearing effect and stability.

[0121] As can be seen from the comparison between Comparative Example 4 and Example 1, the montmorillonite that has not been modified in any way is too hydrophilic and cannot be dispersed in the oil-based system. It cannot provide skeleton support and will also destroy the emulsion stability, resulting in a significant reduction in performance.

[0122] As can be seen from the comparison between Comparative Example 5 and Example 1, although the cutting performance of the cutting agent in this comparative example is close to that of Example 1, the polymer content is increased by 50%, the viscosity increases, the pumping resistance of the drilling fluid increases, and there is a risk of the drilling fluid rheology becoming uncontrollable. The overall performance is not as good as that of Example 1.

[0123] The cutting agent prepared by this invention has stable performance, excellent salt resistance and temperature resistance, and high dynamic cutting force. It can effectively solve the problems of insufficient cutting performance of drilling fluid in deep well high temperature and high salt and calcium formations and the sedimentation of weighting agents.

[0124] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. An environmentally friendly, salt-resistant, and temperature-resistant cutting agent for drilling fluids, characterized in that, It consists of components of the following mass: 20-30 parts of acrylate polymer, 100-120 parts of composite modified montmorillonite, 3-5 parts of isopropyl palmitate, and 150-200 parts of water; The method for preparing the acrylate polymer includes the following steps: (1a) Mix polyvinyl alcohol, sodium hydrogen phosphate and water evenly to obtain a dispersant solution; mix benzoyl peroxide and acetone evenly to obtain an initiator solution; (1b) Styrene, methyl methacrylate and octadecyl acrylate are mixed evenly to obtain mixture 1; 2-acrylamide-2-methylpropanesulfonic acid is mixed evenly with water, the pH is adjusted to 7-8, N-vinylpyrrolidone and N,N'-methylenebisacrylamide are added and mixed evenly to obtain mixture 2; wherein, the mass ratio of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid and N-vinylpyrrolidone is (35-40):(25-30):(10-15):(8-12):(5-8); (1c) Under anaerobic conditions, mix mixture 1, mixture 2 and dispersant solution evenly, add initiator solution, heat to 75-80℃ and react for 3-4 hours, then heat to 90-95℃ and react for 1-2 hours, cool, filter, wash, dry and sieve to obtain acrylate polymer. The preparation method of the composite modified montmorillonite includes the following steps: (2a) Montmorillonite, dioctadecyl dimethyl ammonium chloride and water were mixed at 65-80℃ for 3-5h, centrifuged, washed, dried and ground to obtain quaternary ammonium salt modified montmorillonite; (2b) Mix 3-aminopropyltriethoxysilane with an aqueous ethanol solution until homogeneous, adjust the pH to 4-5, add lignocellulose, ultrasonically stir at 50-60℃ for 2-3 hours, wash, and dry to obtain modified lignocellulose; (2c) Mix the modified lignocellulose, quaternary ammonium salt modified montmorillonite with water evenly, stir ultrasonically, filter, transfer to a vacuum drying oven and heat-treat at 90-100℃ for 2 hours, wash, dry, grind, and obtain composite modified montmorillonite.

2. The environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to claim 1, characterized in that, The ratio of polyvinyl alcohol, styrene, sodium hydrogen phosphate and water is (1.5-2)g∶(35-40)g∶(0.5-0.6)g∶(220-240)mL.

3. The environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to claim 1, characterized in that, The amount of benzoyl peroxide used is 0.4%-0.6% of the total mass of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone; the ratio of benzoyl peroxide to acetone is 1g:(25-30)mL.

4. The environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to claim 1, characterized in that, In step (1b), the amount of N,N'-methylenebisacrylamide used is 0.05%-0.15% of the total mass of styrene, methyl methacrylate, octadecyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone.

5. The environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to claim 1, characterized in that, In step (2a), the mass ratio of montmorillonite to dioctadecyldimethylammonium chloride is (4-6):

1.

6. The environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to claim 1, characterized in that, In step (2b), the amount of 3-aminopropyltriethoxysilane used is 3%-5% of the mass of lignocellulose.

7. The environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to claim 1, characterized in that, In step (2c), the mass ratio of modified lignocellulose to quaternary ammonium salt modified montmorillonite is 1:(3.5-5).

8. A method for preparing an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid according to any one of claims 1-7, characterized in that, The composite modified montmorillonite is mixed evenly with water, and then acrylate polymer and isopropyl palmitate are added in sequence. The mixture is then degassed under vacuum, dried, pulverized, and sieved to obtain an environmentally friendly salt-resistant and temperature-resistant cutting agent for drilling fluid.

Images