An integrated variable viscosity polymer viscosifier and a method of making the same

Abstract

The application provides an integrated variable viscosity polymer thickening agent and a preparation method thereof, and specifically comprises the following raw materials: acrylamide, N-benzyl-N-methyl acryloyl oxy-N, N-dimethylamino ammonium chloride, docosyl polyoxyethylene ether methacrylate, azobisdimethylamidinum hydrochloride and solvent deionized water. The thickening agent prepared by the application has good thickening effect, high temperature resistance, shear resistance, salt resistance, can be used as a drag reducing agent at low concentration and as a thickening agent at high concentration. The thickening agent prepared by the application can be operated under high temperature and high salinity conditions, has good compatibility with a formation, and has a large relative molecular mass, high cationic degree and good stability. The preparation equipment is simple, the price is relatively low, the operation is easy, the pollution is small, and the industrial production is easy.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemicals, and in particular to an integrated variable viscosity polymer thickener and its preparation method. Background Technology

[0002] With the continuous growth of global demand for oil and gas resources, oil and gas exploration and development technologies are constantly advancing to address the challenge of increasingly scarce high-porosity, high-permeability, high-quality oil and gas resources. In the long-term development process, most high-quality oil and gas fields have gradually entered the later stages of exploitation; therefore, the development of unconventional oil and gas reservoirs has become a current focus. These reservoirs often have complex formation environments and poor permeability, placing higher demands on exploration and development technologies. To improve formation permeability and increase oil and gas production, effective formation stimulation is particularly crucial. Among these methods, hydraulic fracturing, as an important means of low-permeability reservoir stimulation, has received widespread attention.

[0003] Hydraulic fracturing technology uses the high pressure generated by a fracturing truck to inject a high-viscosity fluid into the bottom of the well, causing the formation to fracture and form new fractures. These fractures are effectively supported by proppant, thereby significantly improving formation permeability and making it easier for oil and gas to seep into the wellbore, effectively increasing oil well production and reservoir utilization. In this process, fracturing fluid is a key component, mainly responsible for creating fractures and delivering proppant; its performance has a decisive impact on the fracturing effect.

[0004] Fracturing fluids are mainly classified into three categories: water-based, oil-based, and foam-based. Among them, water-based fracturing fluids are widely used in major oilfields due to their advantages such as high safety, low cost, and simple process. In water-based fracturing fluids, the thickener, as the main agent, plays a decisive role in the performance of the fracturing fluid system.

[0005] However, existing thickeners still have many shortcomings in application scenarios. Natural plant gum-based fracturing fluid systems leave a lot of residue after breaking up, causing significant damage to the original formation properties; clean fracturing fluid systems leave no residue after breaking up, but their poor temperature resistance and high cost limit their application; polymer-based fracturing fluid systems can be obtained through chemical or physical crosslinking, but chemical crosslinking reduces the system's shear resistance and results in high friction during pumping, affecting the construction effect. In contrast, supramolecular hydrophobic associating polymer fracturing fluid systems obtained through physical crosslinking have excellent shear recovery and viscoelastic properties and low residue content after breaking up, but further research and development are needed to optimize their performance and meet a wider range of fracturing construction needs.

[0006] In summary, while existing thickeners have certain advantages in application scenarios, they still have many shortcomings and deficiencies, such as excessive residue, poor temperature resistance, low shear resistance, and high friction. There is an urgent need to develop new thickeners to overcome these defects. Summary of the Invention

[0007] The purpose of this invention is to provide an integrated variable viscosity polymer thickener and its preparation method.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] This invention provides an integrated variable viscosity polymer thickener, the raw material components of which include:

[0010] Acrylamide (AM), N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride (MTC), docosyl polyoxyethylene ether methacrylate (BEM), azobisisobutyramidine hydrochloride, solvent.

[0011] The raw materials are calculated in parts by weight as follows:

[0012] Acrylamide (AM): 3-10 parts;

[0013] N-Benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride (MTC): 0.5~1 part;

[0014] Didodecyl polyoxyethylene ether methacrylate (BEM): 0.5~1 part;

[0015] Azobisisobutyramidine hydrochloride (V50): 0.05~0.3 parts;

[0016] Solvent: 60-90 parts.

[0017] The solvent is deionized water.

[0018] A method for preparing an integrated variable viscosity polymer thickener, comprising the following steps:

[0019] Step 1: Weigh the raw materials: acrylamide, N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, docosyl polyoxyethylene ether methacrylate, azobisisobutyramidine hydrochloride, and solvent;

[0020] Step 2: Mix acrylamide, N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, and docosyl polyoxyethylene ether methacrylate evenly in a solvent, pour into a reaction vessel, introduce nitrogen gas, and slowly heat after half an hour;

[0021] Step 3: After the above reaction stabilizes, azobisisobutyramidine hydrochloride is added dropwise to the above reaction solution at a uniform rate as an initiator. The reaction temperature is controlled, and the reaction continues for 4 to 9 hours after titration to obtain a colorless and transparent gel.

[0022] Step 4: Wash the above colorless and transparent gel with anhydrous ethanol, cut it into small pieces, and dry it to obtain a white powder, which is the thickener.

[0023] In step one, the mass fractions of each raw material are as described above.

[0024] In step three, the reaction temperature is 45~75℃.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The integrated variable viscosity polymer thickener of the present invention achieves significant performance improvements and a wide range of applications through a carefully designed monomer ratio and a unique polymerization process. This thickener not only significantly increases apparent viscosity but also significantly enhances temperature and shear resistance, while exhibiting excellent performance in anti-swelling, drag reduction, salt resistance, and sand suspension. These performance improvements are attributed to the introduction of N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride (MTC) and dodecyl polyoxyethylene ether methacrylate (BEM) monomers, which significantly optimize the microstructure and macroscopic properties of the thickener by forming a reversible physical cross-linking network and enhancing intermolecular forces.

[0027] 2. The thickener of this invention utilizes a reversible physical cross-linking network formed by hydrophobic associating polymers in water, effectively improving hydrodynamic volume and solution viscosity. Simultaneously, the addition of BEM not only enhances the interactions between polymer molecules, such as hydrogen bonds, hydrophobic association, and linear entanglement, but also significantly improves the water solubility of the thickener, making it easier to disperse and dissolve in water. These mechanistic advantages collectively contribute to the significant performance improvement of the thickener.

[0028] 3. The thickener of this invention also brings significant social benefits. By improving production efficiency and product quality, and reducing production costs and environmental pollution, it makes a positive contribution to the sustainable development of society. Attached Figure Description

[0029] Figure 1 This is the infrared spectrum of the thickener prepared in Example 1.

[0030] Figure 2 This is a temperature and shear resistance diagram of the thickener prepared in Example 1.

[0031] Figure 3 This is a drag reduction diagram of the thickener prepared in Example 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] This invention discloses an integrated variable viscosity polymer thickener and its preparation method.

[0034] 1. The raw materials include:

[0035] Acrylamide (AM) is the most important and simplest of the acrylamide family, with a wide range of applications, serving as a raw material for organic synthesis and polymer materials. Its polymers are water-soluble, making it suitable for producing flocculants in water treatment, particularly effective at flocculating proteins and starches in water. Besides flocculation, it also possesses excellent thickening, shear resistance, drag reduction, and dispersing properties. As a soil conditioner, it increases soil water permeability and moisture retention; as a paper filler, it increases paper strength, replacing starch and water-soluble ammonia resins; as a chemical grouting agent, it is used for leak sealing in civil engineering projects such as tunnel excavation, oil well drilling, mines, and dams; as a fiber modifier, it improves the physical properties of synthetic fibers; as a preservative, it can be used for corrosion protection of underground components; and it can also be used as an additive in the food industry, a dispersant for pigments, and a printing and dyeing paste. Combined with phenolic resin solutions, it can be used to make adhesives for glass fibers, and with rubber, it can be used to make pressure-sensitive adhesives. It can be polymerized with monomers such as vinyl acetate, styrene, vinyl chloride, and acrylonitrile to prepare a variety of synthetic materials. This product can also be used as a raw material for pharmaceuticals, pesticides, dyes, and coatings.

[0036] N-Benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride (MTC) is an organic compound. Due to the presence of double bonds and cationic quaternary ammonium groups in its molecule, it can copolymerize with many unsaturated monomers. The copolymers carry a positive charge in their aqueous solutions, forming cationic or zwitterionic polymers, which are important raw materials for oilfield chemicals. Because the copolymers exhibit good hydrolytic stability and temperature and salt resistance, copolymers of this product with other monomers can be used in temperature and salt resistant drilling fluid treatment agents, oil well cement additives, acid fracturing additives, and oil displacement agents.

[0037] To achieve the dual purpose of improving the crosslinking strength and increasing the solubility of the integrated variable viscosity polymer thickener, dodecyl polyoxyethylene ether methacrylate (BEM) is used. BEM is a polyether formed by the condensation of polyethylene glycol and stearyl alcohol. It has the characteristics of high stability, good water solubility, electrolyte resistance, easy biodegradability, low foaming, and high surface activity. It is widely used in the detergent industry, textile industry, paper industry, agriculture, oilfield industry, etc. Straight-chain alkanes are highly hydrophobic. The more oxygen on the hydrophilic group of the molecule, the easier it is to form more hydrogen bonds with water, and the better the water solubility. Due to the presence of alkane chains in dodecyl polyoxyethylene ether methacrylate, in aqueous solution, the hydrophobic part aggregates and associates through non-covalent bond interaction, which can form surfactant micelle structures. Therefore, the functional monomer has the following characteristics: (1) specific active acrylate groups with high polymerization activity; (2) the embedded oxyethylene segments increase the water solubility of BEM monomer; (3) C22 straight-chain alkanes easily form aggregates in water, showing strong association ability. It is expected to be used in the development of high molecular weight cationic polymer products with properties of temperature and pressure resistance, acid and alkali resistance, and salt resistance.

[0038] Azobisisobutyramidine hydrochloride (V50) does not induce decomposition, and the decomposition reaction is first-order. Changing the pH of the solution will slightly induce decomposition. It can be used alone, and polymerization can be initiated at relatively low temperatures with very low concentrations and minimal catalyst residue. Polymerization proceeds at a constant rate, almost 100% complete, with no change in pH. It can produce polymers with ultra-high molecular weight and excellent water solubility, and the product has a slight color change. It is relatively stable when stored at room temperature. The price is slightly higher, but the dosage is small and the effect is good.

[0039] The solvent, deionized water, was prepared in the laboratory.

[0040] 2. Mass ratio of each component

[0041] Acrylamide (AM): 3-10 parts;

[0042] N-Benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride (MTC): 0.5~1 part;

[0043] Didodecyl polyoxyethylene ether methacrylate (BEM): 0.5~1 part;

[0044] Azobisisobutyramidine hydrochloride (V50): 0.05~0.3 parts;

[0045] Solvent: Deionized water: 60-90 parts.

[0046] A method for preparing an integrated variable viscosity polymer thickener, comprising the following steps:

[0047] S1. Weigh out the following raw materials: Acrylamide (AM): 3-10 parts; N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride (MTC): 0.5-1 part; dodecyl polyoxyethylene ether methacrylate (BEM): 0.5-1 part; azobisisobutyramidine hydrochloride (V50): 0.05-0.3 parts; solvent deionized water: 60-90 parts.

[0048] S2. Mix the prepared acrylamide, N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride and docosyl polyoxyethylene ether methacrylate in deionized water until well mixed, pour into a reaction vessel, introduce nitrogen gas, and heat slowly for half an hour.

[0049] S3. After the above reaction stabilizes, add 0.05 to 0.3 parts of azobisisobutyramidine hydrochloride as an initiator dropwise to the above reaction solution at a uniform rate. Control the reaction temperature at 45 to 75°C. After titration, continue the reaction for 4 to 9 hours to obtain a colorless and transparent gel.

[0050] S4. The above-mentioned colorless and transparent gel-like substance is washed with anhydrous ethanol, cut into small pieces, and dried to obtain a white powder, which is the target thickener of the present invention.

[0051] The mechanism of the thickener provided by this invention is as follows: (1) Compared with HPAM, branched hydrophobic associative polymers (with a small number of hydrophobic groups in the polymer backbone) can rapidly form a reversible physical cross-linking network in water, exhibiting more complex rheological properties and responses to external stimuli. They have great application potential in drug delivery, shape memory materials, drag reduction agents, and thickeners for hydraulic fracturing in oil fields. The intermolecular forces of hydrophobic groups increase with the increase of the number of hydrophobic groups and the length of the hydrophobic carbon chain. The existence of hydrophobic microregions in polymers is often confirmed by fluorescent probe method. Hydrophobic monomers are generally difficult to dissolve in water. As the number of hydrophobic groups and the length of the hydrophobic carbon chain in the polymer increase, the solubility of the polymer will also decrease. Dodecyl polyoxyethylene ether methacrylate has the characteristics of solubilization, reducing surface tension, and spontaneous aggregation into associative micelles in water. Introducing dodecyl polyoxyethylene ether methacrylate into HPAM synthesizes an amphiphilic soluble polymer. The hydrophobic carbon chain C22 can form a reversible physical crosslinking network through association, increasing the polymer's hydrodynamic volume and the viscosity of the polymer solution. The oxyethylene segment is a strongly polar, hydrophilic, flexible segment, and the synthesized materials typically exhibit excellent flexibility, water retention, tensile strength, swelling capacity, and environmental stability. In this case, the thickener contains active acrylate groups, exhibiting high polymerization activity, which is beneficial for synthesizing polymers with small size and multi-block sequence structures.

[0052] This invention uses aqueous solution free radical polymerization to synthesize an amphiphilic functional monomer modified hydrophobic associative polymer thickener. The entanglement of polymer chains is the theoretical basis of polymer solution rheology. Different flexible segments in a polymer result in different molecular structures and linear entanglement forms. With the increase of ethylene oxide chains, some intermolecular forces may be generated in the polymer aqueous solution, specifically: (1) the hydrogen bonds formed between water and amide groups will enhance the solubility of the polymer and the binding force between chains; (2) the hydrogen bonds between water and ethylene oxide segments will strengthen the binding force between polymer chains; (3) C22 has strong hydrophobicity and can form hydrophobic associative micelles under the "entropy-driven" effect, increasing the intermolecular binding force; (4) the repulsion between the hydrophobic chain and the hydrophilic ethylene oxide segments enhances the hydrophobicity of the hydrophobic chain and increases the hydrophobic association strength; (5) due to the presence of hydrogen bonds, the hydrophobic associative structure further increases the linear entanglement between ethylene oxide segments. Therefore, with the increase of oxyethylene segments, the interaction force between polymer molecules increases, the self-assembly behavior of polymers and the density of interpenetrating space network structure are enhanced, which have different effects on the macroscopic properties of polymers. In water, polymers can spontaneously aggregate to form dynamic and reversible physical cross-linked associated structures through an "entropy-driven process", increasing the hydrodynamic volume of polymers and forming a dense three-dimensional spatial network structure; (6) In polymer solutions, hydrophobic association, hydrogen bonds, van der Waals forces and other forces coexist synergistically. There are both hydrophobic association and linear entanglement cross-linked network structures between polymers. The strong interlacing structure and high interfacial adhesion force cause the polymer to dissipate more energy during external shear deformation, and the polymer exhibits higher toughness and stability. With the increase of polymer concentration, the interaction force between polymers is enhanced, the force of the multi-bridged supramolecular structure formed by linear entanglement and hydrophobic association is enhanced, and the polymer solution exhibits more complex fluid properties and response to external stimuli, making the polymer more environmentally adaptable.

[0053] The present invention will be described in detail below through embodiments:

[0054] Example 1

[0055] 1. Add 8 parts acrylamide, 1 part dodecyl polyoxyethylene ether methacrylate, 1 part N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, and 89.95 parts deionized water to a reaction vessel, and purge with nitrogen for half an hour to remove oxygen. Then raise the temperature to 55°C, add 0.05 parts of initiator azobisisobutyramidine hydrochloride, and react for 6 hours to obtain a colorless and transparent gel, which is the target thickener.

[0056] 2. Take 2g of the target thickener and dissolve it in 400g of experimental water. After complete dissolution, measure its viscosity using a six-speed viscometer. The apparent viscosity of a 0.5% mass fraction is 150 mPa·s. It has a good thickening effect.

[0057] Example 2

[0058] 1. Add 9 parts acrylamide, 0.5 parts dodecyl polyoxyethylene ether methacrylate, 0.5 parts N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, and 99.8 parts deionized water to a reaction vessel, and purge with nitrogen for half an hour to remove oxygen. Then raise the temperature to 55°C, add 0.2 parts of initiator azobisisobutyramidine hydrochloride, and react for 6 hours to obtain a colorless and transparent gel, which is the target thickener.

[0059] 2. Take 2g of the target thickener and dissolve it in 400g of experimental water. After complete dissolution, measure its viscosity using a six-speed viscometer. The apparent viscosity of a 0.5% mass fraction is 130 mPa·s. It has a good thickening effect.

[0060] Example 3

[0061] 1. Add 8 parts acrylamide, 1 part docosyl polyoxyethylene ether methacrylate, 1 part N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, and 89.7 parts deionized water to a reaction vessel, and purge with nitrogen for half an hour to remove oxygen. Then raise the temperature to 55°C, add 0.3 parts of initiator azobisisobutyramidine hydrochloride, and react for 6 hours to obtain a colorless and transparent gel, which is the target thickener.

[0062] 2. Take 2g of the target thickener and dissolve it in 400g of experimental water. After complete dissolution, measure its viscosity using a six-speed viscometer. The apparent viscosity of a 0.5% mass fraction is 140 mPa·s. It has a good thickening effect.

[0063] Figure 1 This is the infrared spectrum of the thickener prepared in Example 1.

[0064] from Figure 1 It can be seen from this that 3466 cm -1 and 3188 cm -1 The absorption peak at 2922 cm⁻¹ represents the NH stretching vibration in acrylamide; the absorption peak of the CH stretching vibration in the methylene group of the hydrophobic monomer dodecyl polyoxyethylene ether methacrylate is located at 2922 cm⁻¹. -1 and 2860 cm -1 The C=O stretching vibration of the methylene group of dodecyl polyoxyethylene ether methacrylate at 1670 cm⁻¹ -1 Absorption peaks are present; the rigid monomer N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride has an absorption peak at 1452 cm⁻¹. -1 There is an absorption peak on the benzene ring skeleton.

[0065] Compared to HPAM, the hydrophobic associative polymer in this invention can rapidly form a reversible physical cross-linked network in water. This network structure not only increases the hydrodynamic volume of the polymer but also increases the viscosity of the polymer solution, resulting in more complex rheological properties and responsiveness to external stimuli in applications. In the thickener of this invention, the embedding of BEM increases the number of oxyethylene segments, thereby enhancing the intermolecular interactions of the polymer molecules. These forces include hydrogen bonding, hydrophobic association, and linear entanglement, which work synergistically to enable the polymer to spontaneously aggregate in water to form a dynamic, reversible physical cross-linked associative structure. This structure not only improves the stability and toughness of the polymer but also enhances its environmental adaptability. The oxyethylene segments in BEM are highly polar hydrophilic flexible segments, and their addition significantly improves the water solubility of the thickener. This makes the thickener easier to disperse and dissolve in water, thereby improving its efficiency and convenience of use.

[0066] This invention successfully prepared an integrated variable viscosity polymer thickener by introducing two innovative monomers: N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride (MTC) and dodecyl polyoxyethylene ether methacrylate (BEM). This thickener not only achieves significant performance improvements but also demonstrates broad potential and value in practical applications.

[0067] 1. Significantly Improved Apparent Viscosity: The thickener of this invention significantly improves the apparent viscosity of the polymer through the synergistic effect of MTC and BEM. This allows the thickener to more effectively increase the viscosity of liquids in applications, meeting the requirements of specific processes for high-viscosity liquids.

[0068] 2. Enhanced Temperature and Shear Resistance: Traditional thickeners often experience performance degradation under high temperature or high shear stress conditions. However, this invention, through optimized monomer ratios and polymerization processes, enables the thickener to exhibit excellent temperature and shear resistance. This ensures the stability and durability of the thickener under high temperature or high shear stress environments. Figure 2 This is a temperature and shear resistance graph of the thickener prepared in Example 1. The shear rate was fixed at 170 s⁻¹. -1 When the temperature rises to 120 °C, the apparent viscosity of the 0.5% (w / w) HLCW thickener aqueous solution is 57.36 mPa·s. After shearing for 1.5 h, the residual viscosity of the HLCW thickener aqueous solution is 78.96 mPa·s.

[0069] 3. Optimized anti-swelling, drag reduction, salt resistance, and sand-suspending properties: The thickener of this invention exhibits excellent performance in anti-swelling, drag reduction, salt resistance, and sand-suspending properties. These improvements are attributed to the addition of MTC and BEM, which effectively control liquid flowability by improving the polymer's microstructure and intermolecular forces. Figure 3This is a drag reduction graph of the thickener prepared in Example 1. When the mass fraction of the thickener is 0.0125%, the drag reduction rate is 73.56%. As the concentration of the thickener gradually increases, the drag reduction effect decreases.

[0070] The preferred embodiments of the present invention have been described in detail above, and are only for the purpose of helping to understand the present invention, and are not intended to limit the present invention. Any partial modifications or substitutions made by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of the present invention.

Claims

1. A method for preparing an integrated variable viscosity polymer thickener, characterized in that, The method includes the following steps: Step 1: Weigh the raw materials: acrylamide, N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, docosyl polyoxyethylene ether methacrylate, azobisisobutyramidine hydrochloride, and solvent; Step 2: Mix acrylamide, N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, and docosyl polyoxyethylene ether methacrylate evenly in a solvent, pour into a reaction vessel, introduce nitrogen gas, and slowly heat after half an hour; Step 3: After the above reaction stabilizes, azobisisobutyramidine hydrochloride is added dropwise to the above reaction solution at a uniform rate as an initiator. The reaction temperature is controlled, and the reaction continues for 4 to 9 hours after titration to obtain a colorless and transparent gel. Step 4: Wash the above colorless and transparent gel with anhydrous ethanol, cut it into small pieces, and dry it to obtain a white powder, which is the thickener; The raw material components of the thickener include: Acrylamide, N-benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride, docosyl polyoxyethylene ether methacrylate, azobisisobutyramidine hydrochloride, solvent; The solvent is deionized water; In step one, the raw materials are calculated by mass as follows: Acrylamide: 3-10 parts; N-Benzyl-N-methacryloyloxy-N,N-dimethylaminoammonium chloride: 0.5~1 part; Dodecyl polyoxyethylene ether methacrylate: 0.5~1 part; Azobisisobutyramidine hydrochloride: 0.05~0.3 parts; Solvent: 60-90 parts.

2. The method for preparing an integrated variable viscosity polymer thickener according to claim 1, characterized in that, In step three, the reaction temperature is 45~75℃.

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