A high-salt-resistant polymer oil stabilizer and water-controlling agent, its preparation method and application

Abstract

This invention discloses a high-salt-resistant polymer oil stabilizer and water control agent, its preparation method, and its application, belonging to the field of oil and gas production enhancement technology. This oil stabilizer and water control agent is prepared by low-temperature initiated copolymerization of acrylamide monomer, a salt-resistant monomer containing sulfonic acid groups, a cationic adsorbent monomer, and an acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer. By introducing the synergistic effect of the nonionic hydrophobic monomer and the sulfonic acid monomer, the product exhibits excellent high-salt and high-hardness resistance, maintaining good stability and oil-water selectivity under high salinity and high hardness conditions. Simultaneously, the addition of β-cyclodextrin as a quick-dissolving agent significantly improves the dissolution rate, meeting the requirements for on-site online preparation. This agent is suitable for fracturing, profile control, and water-enhancing operations in low-permeability, high-salt reservoirs, offering advantages such as long-term stability, convenient application, and low cost.

Description

Technical Field

[0001] This invention relates to the field of oil and gas production enhancement technology, specifically to a high-salt-resistant polymer oil stabilizer and water control agent, its preparation method, and its application. Background Technology

[0002] In the later stages of oilfield development, especially in low-permeability old oilfields with long-term water injection, problems such as rapid increase in water cut after fracturing, inefficient circulation of injected water, and low crude oil recovery rates are commonly faced. To achieve "stable oil production and controlled water," chemical methods often employ relative permeability regulators for selective water shut-off. These materials mainly include water-soluble polymers (such as partially hydrolyzed polyacrylamide), resin emulsions, and gels. Their mechanism of action largely relies on the adsorption of polymers on the rock surface and the difference in their conformation in different fluids, achieving efficient reduction of aqueous phase permeability while having minimal impact on the oil phase, exhibiting advantages such as low formation damage and good selectivity. However, existing technologies still have significant shortcomings: conventional polymers have limited temperature and salt resistance, especially in high salinity (>10×10⁻⁶). 4 mg / L) and high hardness (Ca 2+ >5000 mg / L, Mg 2+ In formations with concentrations >3000 mg / L, viscosity decreases and plugging failures are easily caused by ion shielding and cross-linking flocculation. Meanwhile, the long-term stability, erosion resistance, and injectability of the material still need improvement, limiting its long-term application in high-salt reservoirs. Therefore, developing a relative permeability improver that combines good salt and hardness resistance, long-term stability, rapid solubility, and excellent oil-water selectivity has become an urgent technical requirement for stabilizing production and controlling water in low-permeability, high-salt old oilfields.

[0003] Liang Haibin synthesized a novel relative permeability improver and a novel aluminum ion-based crosslinking agent. A novel relative permeability improver system was prepared using a solution blending method, exhibiting good oil-water selectivity and a maximum salt tolerance of 10000 mg / L (Liang Haibin. Research on Water-Controlled Fracturing Technology in High-Water-Cut Oil Layers in Low-Permeability Sandstone [D]. China University of Petroleum (Beijing), 2019. DOI:10.27643 / d.cnki.gsybu.2019.001061). Liu Jianxin studied a supramolecular cationic polymer relative permeability improver, which exhibits good injectability, water control selectivity, scour resistance, and salt tolerance (50000 mg / L). However, the cationic improver exhibits interaction with high-valence metal ions (Ca). 2+ / Mg 2+This may act as a "bridge" to strengthen crosslinking, leading to a decrease in viscosity or the risk of phase separation (Liu Jianxin. Research and Application of Relative Permeability Improvers [D]. China University of Petroleum, 2009). Patent CN120271749B, "A High-Efficiency Water-Controlling and Oil-Increasing Relative Permeability Improver and Its Preparation Method," describes a relative permeability improver copolymerized from acrylamide, sodium acrylate, 2-acrylamido-2-methacrylic acid, sulfonate-containing hydrophobic monomers, and cationic adsorption monomers. It has good injectability and oil-stabilizing and water-controlling properties, but does not mention its salt resistance, especially its resistance to high-salt, high-hardness formation water and its long-term scouring performance. Patent CN 119505075 B, "Relative Permeability Improver, Fracturing Fluid System Containing It, and Their Preparation Methods and Applications," describes a relative permeability improver copolymerized from acrylamide, 2-acrylamido-2-methacrylic acid AMPS, cationic hydrophobic monomers, and cationic hydrophobic monomers. It has good oil-stabilizing and water-controlling properties and long-term effectiveness, but does not mention its salt resistance and high-hardness resistance.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a high-salt-resistant polymer oil stabilizer and water control agent and its preparation method, so as to solve the technical problems of poor selectivity, insufficient long-term effectiveness, and low on-site preparation efficiency of existing water control materials in high-water-content, high-salt, and high-hardness reservoirs.

[0006] To achieve the above objectives, the present invention provides a high-salt-resistant polymer oil stabilizer and water control agent, the raw materials of which include: acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, cationic adsorbent monomer, acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer, low-temperature composite initiator, molecular weight regulator, quick-dissolving agent and water; wherein, the mass ratio of the acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, cationic adsorbent monomer and acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer is 1:(0.15~0.25):(0.02~0.05):(0.03~0.1):(0.005~0.02).

[0007] Preferably, in the high-salt resistant polymer oil stabilizer and water control agent provided by the present invention, the salt-resistant monomer containing sulfonic acid groups is selected from at least one of sodium 2-acrylamido-2-methylpropanesulfonate, sodium ethylenebenzenesulfonate, sodium acrylamidebenzenesulfonate, and sodium 5-vinylnaphthalenesulfonate.

[0008] Preferably, in the high-salt-resistant polymer oil stabilizer and water control agent provided by the present invention, the cationic adsorption monomer is selected from trimethylallyl ammonium chloride or dimethyldiallyl ammonium chloride.

[0009] Preferably, in the high-salt resistant polymer oil stabilizer and water control agent provided by the present invention, the general structural formula of the acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer is shown in Formula 3.

[0010] Formula 3;

[0011] In Formula 3, the number of ethylene oxides m = 5~10; R1 is an alkyl group with a carbon chain length of 8 or 10; R2 is an alkyl group with a carbon chain length of 10 or 12.

[0012] Preferably, in the high-salt resistant polymer oil stabilizer and water control agent provided by the present invention, the quick-dissolving aid is β-cyclodextrin, and its dosage is 0.01% to 0.02% of the total mass of the five monomers.

[0013] Preferably, in the high-salt resistant polymer oil stabilizer and water control agent provided by the present invention, the molecular weight regulator is selected from at least one of sodium formate, n-butanethiol, sodium hypophosphite, and urea, and the dosage is 0.1% to 0.3% of the total mass of the five monomers.

[0014] Preferably, in the high-salt-resistant polymer oil stabilizer and water-controlling agent provided by the present invention, the low-temperature composite initiator includes:

[0015] Catalyst: Selected from manganese sulfate or cerium ammonium nitrate, the amount used is 0.001%~0.003% of the total mass of the five monomers;

[0016] Reducing agent: selected from sodium bisulfite or sodium sulfite, used in an amount of 0.005%~0.0125% of the total mass of the five monomers;

[0017] Oxidizing agent: selected from ammonium persulfate, sodium persulfate or hydrogen peroxide, and the amount used is 0.003% to 0.005% of the total mass of the five monomers.

[0018] This invention also provides a method for preparing the above-mentioned high-salt resistant polymer oil stabilizer and water control agent, comprising the following steps:

[0019] 1) Dissolve acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, cationic adsorption monomer, and acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer in water, adjust the pH to 7.0~8.5, and obtain a mixed solution with a total monomer concentration of 25%~30%;

[0020] 2) Cool the system temperature of the mixed solution to -5~0℃, add molecular weight regulator and quick-dissolving agent, stir with nitrogen gas, add low temperature composite initiator, and polymerize under adiabatic conditions for 3~6 hours to obtain the target polymer;

[0021] 3) The target polymer is dried, pulverized and sieved to obtain a high-salt resistant polymer oil stabilizer and water control agent with a viscosity-average molecular weight of 1 million to 3 million and a particle size of 100 to 140 mesh.

[0022] The high-salt-resistant polymer oil stabilizer and water control agent provided by this invention can be used for water control and production enhancement in oil fields.

[0023] The present invention also provides a method for improving the oil recovery rate of high-salt, high-hardness reservoirs by injecting the above-mentioned high-salt resistant polymer oil stabilizer and water control agent into the target formation.

[0024] This invention provides a high-salt-resistant polymer oil stabilizer and water control agent, which has the following advantages:

[0025] This invention constructs a multi-component copolymer system integrating sulfonic acid-based salt-resistant monomers, cationic adsorbent monomers, and nonionic hydrophobic monomers through precise molecular structure design. Its synergistic mechanism lies in the preferential anchoring of cationic monomers to the rock surface to regulate wettability. The key lies in the introduced Guerbert alcohol-based nonionic hydrophobic monomer, whose unique double-tailed chain structure significantly enhances the hydrophobic association strength, forming a denser and more stable dynamic physical cross-linking network in the aqueous phase. This results in a strong blocking effect on the aqueous phase while maintaining low resistance to the oil phase, achieving excellent oil-water selectivity. Furthermore, the nonionic design completely avoids interaction with high-valence cations (Ca) in the formation. 2+ / Mg 2+ The adverse ionic cross-linking reaction fundamentally solves the flocculation and failure problems caused by salt and hardness; while the strongly hydrated sulfonic acid groups further maintain the main chain extension through electrostatic repulsion. The two work together to ensure the structural stability and long-term plugging performance of the product in extreme formation environments with high salt and high hardness, breaking through the technical bottleneck of conventional ionic polymers being prone to deactivation in such reservoirs.

[0026] This invention achieves rapid dissolution of the product by introducing a β-cyclodextrin quick-dissolving agent and optimizing its molecular weight. Its unique inclusion effect prevents powder agglomeration, ensuring rapid dispersion and thickening even under complex brine conditions, fully meeting the immediate application requirements of online continuous preparation. This technology eliminates the need for traditional large-scale dispensing stations and lengthy curing processes, allowing for efficient preparation directly using skid-mounted equipment. This significantly shortens the operation cycle, reduces overall costs, and optimizes the construction process for cost reduction and efficiency improvement.

[0027] The oil stabilizing and water-controlling agent provided by this invention possesses excellent injectability and formation compatibility, and can be flexibly integrated into fracturing and production enhancement operations in low-permeability old oilfields. It can be used as a pre-flush fluid to adjust the fluid profile, can be compounded with fracturing fluid to form a long-term water-control barrier within the fracture, and can also be used as a displacement fluid to enhance near-wellbore water control. This deep integration with fracturing technology provides key material support for solving post-fracturing water channeling and extending the stable production cycle, and expands the effective technical approach for water control and oil enhancement in high-salinity reservoirs. Attached Figure Description

[0028] Figure 1 The infrared spectrum of the acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer of Formula 5 is shown.

[0029] Figure 2 The 1H NMR spectrum of the acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer of Formula 5 is shown. Detailed Implementation

[0030] 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.

[0031] Note: Unless otherwise specified, the experimental methods in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. The main sources of the experimental raw materials are as follows: acrylamide, sodium acrylate (Henan Boyuan), sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinylbenzenesulfonate (Shandong Aubote), and trimethylallyl ammonium chloride (Guangya Polymer).

[0032] This invention provides a high-salt-resistant polymer oil stabilizer and water control agent. The raw materials of the oil stabilizer and water control agent include: acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid groups, cationic adsorption monomer, acrylate-terminated Guerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer, low-temperature composite initiator, molecular weight regulator, quick-dissolving agent, and water. A method for preparing this oil stabilizer and water control agent is also provided, comprising the following steps:

[0033] (1) Weigh deionized water into a 2L beaker, and add acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, cationic adsorption monomer, and acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer in sequence according to the feeding ratio of each monomer. After stirring and dissolving evenly, add pH value adjuster to adjust the pH value to 7.0~8.5 to obtain a mixed solution with a total monomer mass concentration of 25%~30%.

[0034] (2) Reduce the temperature of the mixed solution to -5~0℃, add molecular weight regulator and quick-dissolving agent, and simultaneously introduce nitrogen gas and stir for 30~40min. Then add low temperature composite initiator and polymerize under adiabatic conditions for 3~6h. After the polymerization reaction is completed, cut, dry, crush and sieve in sequence to obtain high salt resistant oil stabilizer and water control agent.

[0035] (3) The viscosity-average molecular weight of the oil stabilizer and water control agent was tested and calculated according to the standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide" using an Ubbelohde viscometer (0.55 mm capillary inner diameter).

[0036] The mass ratio of the acrylamide monomer, sodium acrylate hydrophilic monomer, sulfonic acid-containing salt-resistant monomer, cationic adsorption monomer, and acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer is 1: (0.15~0.25): (0.02~0.05): (0.03~0.1): (0.005~0.02).

[0037] The sulfonic acid-containing salt-resistant monomer is selected from any one or more of sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinylbenzenesulfonate, sodium acrylamide-benzenesulfonate, and sodium 5-vinylnaphthalenesulfonate, with sodium 2-acrylamido-2-methylpropanesulfonate and sodium vinylbenzenesulfonate being preferred.

[0038] The cationic adsorbent monomer is selected from trimethylallylammonium chloride or dimethyldiallylammonium chloride. Trimethylallylammonium chloride is preferred.

[0039] The pH adjuster is any one or more of sodium hydroxide, sodium carbonate, or sodium bicarbonate.

[0040] The molecular weight regulator is any one or more of sodium formate, n-butanethiol, sodium hypophosphite, and urea; the dosage is 0.1% to 0.3% of the total mass of the five monomers. The optimal dosage is 0.15% to 0.25% of the total mass of the five monomers.

[0041] The instantaneous dissolving agent is any one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. β-cyclodextrin is preferred, and the amount added is 0.01% to 0.02% of the total mass of the five monomers.

[0042] The low-temperature composite initiator is composed of a catalyst, a reducing agent, and an oxidizing agent. The catalyst is any one or more of manganese sulfate and cerium ammonium nitrate, preferably manganese sulfate, added at a dosage of 0.001~0.003% of the total mass of the five monomers; the reducing agent is any one or more of sodium bisulfite and sodium sulfite, preferably sodium bisulfite, added at a dosage of 0.005~0.0125% of the total mass of the five monomers; the oxidizing agent is any one or more of ammonium persulfate, sodium persulfate, and hydrogen peroxide, preferably sodium persulfate, added at a dosage of 0.003~0.005% of the total mass of the five monomers.

[0043] The resulting high-salt resistant polymer oil stabilizer and water control agent has a viscosity-average molecular weight range of 1 million to 3 million and a particle size of 100 to 140 mesh.

[0044] The acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer can be prepared by the following method, which includes ethoxylation and acylation reactions, with the following specific steps:

[0045] 1) Ethoxylation reaction:

[0046] ① Add Gelbert alcohol to a high-pressure reactor, heat to 100~120℃, and dehydrate under reduced pressure for 1~2 hours to ensure that the moisture content is less than 0.1%.

[0047] ② Cool down to 60~80℃, add alkaline catalyst, and continue stirring for 0.5 hours to ensure uniform dispersion.

[0048] ③ After replacing the air in the reactor with nitrogen, slowly introduce metered ethylene oxide, controlling the reaction temperature at 120~140℃ and the pressure not exceeding 0.3 MPa. Continuously cool during the feeding process to maintain the temperature.

[0049] ④ After the ethylene oxide is added, continue stirring at 120~140℃ for 1~2 hours until the pressure no longer drops.

[0050] ⑤ Cool the reaction mixture to below 80°C, add an acidic substance to neutralize the catalyst to pH 6-7. Then remove low-boiling substances by vacuum distillation to obtain the Gerbert alcohol polyoxyethylene ether intermediate, the reaction formula of which is shown in Formula 1 below.

[0051] Formula 1;

[0052] The Gerbert alcohol is any one of 2-butyloctol, 2-hexyldecol, 2-octyldodecylol, 2-decyltetradecylol, and 2-dodecylhexadecylol. 2-octyldodecylol and 2-decyltetradecylol are preferred.

[0053] The alkaline catalyst is any one or more of potassium hydroxide, sodium hydroxide, and sodium methoxide. Sodium methoxide is preferred, and the amount added is 0.5% to 1% of the mass of Gelbert alcohol, with an optimal concentration of 0.8%.

[0054] The molar ratio of Gerbert alcohol to ethylene oxide is 5~15:1, and the optimal molar ratio is 5~10:1.

[0055] The acidic substances are phosphoric acid and acetic acid. Phosphoric acid is preferred.

[0056] 2) Acylation reaction:

[0057] ① Add Guerbert alcohol polyoxyethylene ether intermediate and dichloromethane to a dry three-necked flask, along with the acid-binding agent triethylamine and a small amount of polymerization inhibitor. Assemble the apparatus with a thermometer, dropping funnel, and reflux condenser, with the condenser connected to the drying tube. Cool to 0-5°C in an ice-water bath under nitrogen protection.

[0058] ② After diluting acryloyl chloride with an appropriate amount of dichloromethane, slowly add it dropwise to the reaction solution, controlling the dropping rate so that the temperature does not exceed 10℃.

[0059] ③ After the addition is complete, gradually raise the temperature to room temperature (20~25℃) and continue stirring for 6~8 hours.

[0060] ④ After the reaction is complete, wash the reaction solution 2-3 times with ice water to remove triethylamine hydrochloride and excess acryloyl chloride. Dry the organic phase with anhydrous sodium sulfate, filter, and then remove the solvent by rotary evaporation.

[0061] ⑤ The crude product is recrystallized (e.g., with ethanol) to obtain the target monomer, which is an acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer. Its reaction formula is shown in Formula 2 below.

[0062] Formula 2;

[0063] In the acylation reaction, the molar ratio of Gerbert alcohol polyoxyethylene ether intermediate, triethylamine, and acryloyl chloride is 1:1.5:1.2; the polymerization inhibitor is hydroquinone, and the dosage is 200 ppm.

[0064] It can be seen that the acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer has the structural formula shown in Formula 3: Formula 3;

[0065] In Formula 3, the number of ethylene oxides m = 5~10; R1 is an alkyl group with a carbon chain length of 8 or 10; R2 is an alkyl group with a carbon chain length of 10 or 12. The optimal acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer structure is shown in Formula 4-7 below: Equation 4;

[0066] Formula 5;

[0067] Formula 6;

[0068] Formula 7;

[0069] The acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer of Formula 5 was determined by infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The results are shown in the figure below. Figure 1 and Figure 2 As shown. Figure 1 As shown, in the infrared spectrum at 3449 cm⁻¹ -1 A relatively broad absorption peak appears at 3081 cm⁻¹, which is attributed to the OH stretching vibration in trace amounts of moisture or impurities; -1 A distinct =CH stretching vibration absorption is observed at 2849 cm⁻¹, indicating the presence of a carbon-carbon double bond in the molecule; -1 With 2924cm -1 The strong absorption peak at 1699 cm⁻¹ is due to the asymmetric and symmetric stretching vibrations of CH in -CH₂- and -CH₃, indicating the presence of a long alkyl carbon chain in the structure; -1 The strong peak at 1462 cm⁻¹ is due to the C=O stretching vibration, a typical characteristic of ester groups; -1 With 1361cm -1 The absorption corresponds to the CH bending vibrations of -CH2- and -CH3, further confirming the presence of alkyl chains; 1212 cm⁻¹ -1 and 1098cm -1 The two absorptions are attributed to the COC stretching vibration, primarily originating from the CO bond in the ester group, but may also reflect the vibrational characteristics of the ether bond; 950 cm⁻¹ -1 The nearby absorption can be attributed to the out-of-plane bending vibration of =CH, consistent with the olefin structure, possibly indicating a trans configuration of the double bond; below 1000 cm⁻¹ -1 Area (e.g., 688cm) -1 526cm -1 The absorption peaks observed (e.g., alkyl chain skeletal vibrations, CH out-of-plane bending, or fingerprint region coupled vibrations) mostly indicate molecular structure identification. For example... Figure 2As shown, the peak at δ 0.85–0.90 (triple, 3H) is located at the highest field and is a typical signal of a terminal methyl (-CH3) proton. The splitting pattern of the triplet indicates that it is adjacent to a methylene (-CH2-) group. The strong absorption peak at δ 1.25 is attributed to the superposition signal of multiple methylene (-CH2-) protons in a long-chain alkyl group. The peak at δ 1.50–1.60 (multiplex, 2H) is the β-methylene (-CH2-) proton peak separated from the epoxide ring by one carbon. Due to the influence of the adjacent functional group, it is slightly less shielded than the methylene peak at δ 1.25. The peaks at δ 3.20–3.50 and δ 3.50–3.80 are characteristic peaks of two non-isotropic protons on the ethylene oxide ring (-O-CH-). Due to ring strain and their connection to oxygen atoms, they appear in the mid-to-low field and split into doublets due to coupling. The peak at δ 5.40–5.50 is also significant. (Multiple peaks, 2H) This peak appears at the lowest field and is a characteristic signal of the double-bonded olefin hydrogen (=CH-). Its precise chemical shift is related to the substitution mode of the double bond, while the splitting mode of the multiple peaks originates from the coupling between olefin hydrogens.

[0070] The oil stabilizer and water control agent provided by this invention can be prepared through the following examples:

[0071] Example 1

[0072] 1) Weigh 1125.0 g of deionized water into a 2 L beaker, and add 311.2 g of acrylamide, 46.7 g of sodium acrylate, 6.2 g of sodium 2-acrylamido-2-methylpropanesulfonate, 9.3 g of trimethylallyl ammonium chloride, and 5.6 g of acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer (m=5, R1=8, R2=10) in sequence while stirring. After stirring and dissolving evenly, add sodium carbonate to adjust the pH to 7.0 to obtain a mixed solution with a total monomer mass concentration of 25%.

[0073] 2) Lower the temperature of the mixed solution to 0℃, add 0.56 g of sodium formate molecular weight regulator and 37.5 mg of β-cyclodextrin quick-dissolving agent, and simultaneously introduce nitrogen gas and stir for 30 min. Then add low-temperature composite initiator (3.75 mg manganese sulfate, 22.5 mg sodium bisulfite, and 11.3 mg sodium persulfate). Polymerize under adiabatic conditions for 4 h. After the polymerization reaction is completed, cut, dry, pulverize, and sieve the product in sequence to obtain a high-salt resistant oil stabilizer and water control agent with a dry powder particle size of 100~140 mesh.

[0074] The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 2.75 million Daltons by using an Ubbelohde viscometer (0.55 mm capillary inner diameter) in accordance with standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0075] Example 2

[0076] 1) Weigh 1080.0 g of deionized water into a 2 L beaker, and add 330.7 g of acrylamide, 82.7 g of sodium acrylate, 9.9 g of sodium 2-acrylamido-2-methylpropanesulfonate, 13.2 g of trimethylallyl ammonium chloride, and 6.6 g of acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer (m=7, R1=8, R2=10) in sequence while stirring. After stirring and dissolving evenly, add sodium bicarbonate to adjust the pH to 7.5 to obtain a mixed solution with a total monomer mass concentration of 28%.

[0077] 2) Lower the temperature of the mixed solution to -3℃, add 0.76 g of n-butanethiol for molecular weight adjustment and 63.0 mg of β-cyclodextrin quick-dissolving agent, and simultaneously purge with nitrogen and stir for 30 min. Then add low-temperature composite initiator (8.4 mg manganese sulfate, 31.5 mg sodium bisulfite, and 14.7 mg sodium persulfate). Polymerize under adiabatic conditions for 5 h. After the polymerization reaction is completed, cut, dry, pulverize, and sieve the product in sequence to obtain a high-salt resistant oil stabilizer and water control agent with a dry powder particle size of 100~140 mesh.

[0078] The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 2.37 million Daltons by using an Ubbelohde viscometer (0.55 mm capillary inner diameter) in accordance with standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0079] Example 3

[0080] 1) Weigh 1125.0 g of deionized water into a 2 L beaker, and add 288.5 g of acrylamide, 57.7 g of sodium acrylate, 9.9 g of sodium ethylenebenzenesulfonate, 13.2 g of trimethylallyl ammonium chloride, and 1.4 g of acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer (m=8, R1=10, R2=12) in sequence while stirring. After stirring and dissolving evenly, add sodium hydroxide to adjust the pH to 8.0 to obtain a mixed solution with a total monomer mass concentration of 25%.

[0081] 2) Lower the temperature of the mixed solution to -5℃, add 0.75 g sodium formate and 0.25 g urea molecular weight regulator, 75.0 mg β-cyclodextrin quick-dissolving agent, and simultaneously purge with nitrogen and stir for 40 min. Then add low-temperature composite initiator (10.5 mg manganese sulfate, 37.5 mg sodium bisulfite, and 18.8 mg sodium persulfate). Polymerize under adiabatic conditions for 5 h. After the polymerization reaction is completed, cut, dry, pulverize, and sieve the product in sequence to obtain a high-salt resistant oil stabilizer and water control agent with a dry powder particle size of 100~140 mesh.

[0082] The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 2.05 million Daltons by using an Ubbelohde viscometer (0.55 mm capillary inner diameter) in accordance with standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0083] Example 4

[0084] 1) Weigh 1050.0 g of deionized water into a 2 L beaker, and add 338.3 g of acrylamide, 74.4 g of sodium acrylate, 13.5 g of sodium ethylenebenzenesulfonate, 20.3 g of trimethylallyl ammonium chloride, and 3.4 g of acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer (m=10, R1=10, R2=12) in sequence while stirring. After stirring and dissolving evenly, add sodium carbonate to adjust the pH to 8.5 to obtain a mixed solution with a total monomer mass concentration of 30%.

[0085] 2) Lower the temperature of the mixed solution to 0℃, add 0.85 g sodium formate and 0.3 g urea molecular weight regulator, 90.0 mg β-cyclodextrin quick-dissolving agent, and simultaneously purge with nitrogen and stir for 40 min. Then add low-temperature composite initiator (13.5 mg manganese sulfate, 54 mg sodium bisulfite, and 22.5 mg sodium persulfate). Polymerize under adiabatic conditions for 6 h. After the polymerization reaction is completed, cut, dry, pulverize, and sieve the product in sequence to obtain a high-salt resistant oil stabilizer and water control agent with a dry powder particle size of 100~140 mesh.

[0086] The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 1.56 million Daltons by using an Ubbelohde viscometer (0.55 mm capillary inner diameter) in accordance with standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0087] Example 5

[0088] 1) Weigh 1095.0 g of deionized water into a 2 L beaker, and add 302.2 g of acrylamide, 54.4 g of sodium acrylate, 15.1 g of sodium 2-acrylamido-2-methylpropanesulfonate, 30.2 g of trimethylallyl ammonium chloride, and 4.5 g of acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer (m=8, R1=10, R2=12) in sequence while stirring. After stirring and dissolving evenly, add sodium bicarbonate to adjust the pH to 8.0 to obtain a mixed solution with a total monomer mass concentration of 27%.

[0089] 2) Lower the temperature of the mixed solution to -2℃, add 0.65 g of sodium formate molecular weight regulator and 72.9 mg of β-cyclodextrin quick-dissolving agent, and simultaneously purge with nitrogen and stir for 30 min. Then add low-temperature composite initiator (8.1 mg manganese sulfate, 34.4 mg sodium bisulfite, and 18.2 mg sodium persulfate). Polymerize under adiabatic conditions for 4 h. After the polymerization reaction is completed, cut, dry, pulverize, and sieve the product in sequence to obtain a high-salt resistant oil stabilizer and water control agent with a dry powder particle size of 100~140 mesh.

[0090] The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 2.83 million Daltons by using an Ubbelohde viscometer (0.55 mm capillary inner diameter) in accordance with standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0091] Comparative Example 1

[0092] The method of Example 5 was followed, except that the system did not contain the cationic monomer trimethylallyl ammonium chloride, and the molecular weight regulator was 1.25 g of sodium formate. Everything else remained unchanged from Example 5, and the target product was obtained. The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 2.98 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0093] Comparative Example 2

[0094] The method of Example 5 was followed, except that the system did not contain acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomers (m=8, R1=10, R2=12), while other aspects remained unchanged from Example 5, to obtain the target product. The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 2.72 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0095] Comparative Example 3

[0096] The method of Example 5 was followed, except that the system did not contain the cationic monomer trimethylallyl ammonium chloride and the acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer (m=8, R1=10, R2=12). The molecular weight regulator was 1.30 g of sodium formate. Everything else remained unchanged from Example 5, and the target product was obtained. The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 2.88 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to standard GB / T 12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0097] Comparative Example 4

[0098] The method of Example 5 was followed, except that the molecular weight regulator in the system was 0.1 g sodium formate, while other aspects remained unchanged from Example 5, to obtain the target product. The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 4.52 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to standard GB / T12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0099] Comparative Example 5

[0100] The method of Example 5 was followed, except that the molecular weight regulator in the system was 3.0 g of sodium formate, while other aspects remained unchanged from Example 5, to obtain the target product. The viscosity-average molecular weight of the oil stabilizer and water control agent was determined to be 860,000 Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to standard GB / T12002.10-1992 "Determination of Molecular Weight of Polyacrylamide".

[0101] Comparative Example 6

[0102] The method of Example 5 was followed, except that the system did not contain β-cyclodextrin, and everything else remained the same as in Example 5, to obtain the target product.

[0103] Performance testing:

[0104] (1) Solubility test

[0105] The water used for on-site preparation is generally clean water or wastewater, with a mineralization of around 30,000 mg / L. This experiment followed the salt ratios (mass ratio of NaCl:MgCl2·6H2O:CaCl2≈20:1:1) in the standard brine formulation described in standard SY / T 6576-2016 "Evaluation Method for Polymers Used to Enhance Oil Recovery" to prepare simulated brine solutions with different mineralizations (5000 mg / L, 10000 mg / L, 30000 mg / L). Using these simulated brine solutions, oil-stabilizing and water-controlling agents were prepared. Referring to the viscosity-increasing rate test method described in industry standard SY / T7627-2021 "Technical Requirements for Water-Based Fracturing Fluids," the viscosity-increasing rate was tested in different simulated brine solutions to evaluate its on-site applicability. The results are shown in Table 1.

[0106] Table 1. Test results of the solubility of oil stabilizer and water control agent

[0107] ;

[0108] As shown in Table 1, the oil-stabilizing and water-controlling agents prepared in Examples 1-5 of this invention exhibited a viscosity-increasing rate exceeding 83.5% after dissolving in saline solutions of varying mineralization (up to 30,000 mg / L) for 3 minutes. In tap water, the rate reached over 90%, meeting the requirements for on-site online mixing (viscosity-increasing rate > 80%). This indicates that the agent possesses excellent dissolution speed and salt resistance. Notably, the viscosity-increasing rate of Comparative Example 6 (without β-cyclodextrin quick-dissolving agent) decreased significantly (to a minimum of only 16.7%), demonstrating that the addition of the quick-dissolving agent is crucial for improving the polymer's dissolution and viscosity-increasing behavior under high-salt conditions, contributing to rapid formulation and on-site applicability.

[0109] (2) Evaluation of oil stabilization and water control performance

[0110] The oil-stabilizing and water-controlling properties of the oil-stabilizing and water-controlling agent include its ability to improve the relative permeability of oil and water, its oil-water phase selectivity, and its long-term resistance to erosion. Experimental conditions: A 0.05% oil-stabilizing and water-controlling agent solution was prepared using tap water, and the simulated formation salinity was 15 × 10⁻⁶. 4 mg / L (calcium ions 5000 mg / L, magnesium ions 3000 mg / L), temperature 70℃.

[0111] The oil-water circulation displacement experiment using a single core was employed to evaluate the oil stabilization and water control performance. The specific experimental steps are as follows:

[0112] ① Vacuum the core, saturate it with water, and measure the pore volume and absolute permeability of the water phase;

[0113] ② Inject the oil phase into the core at a constant flow rate using a constant flow pump until the core ejector fluid no longer contains brine, simulating a formation containing bound water. When the pressure difference between the two ends of the core is constant, record the pressure difference and calculate the permeability at the oil end. K ob ;

[0114] ③ Inject water into the core at a constant flow rate using a constant flow pump until the core ejecta contains no oil, simulating a formation containing residual oil. When the pressure difference between the two ends of the core is constant, record the pressure difference and calculate the permeability at the water phase endpoint. K wa ;

[0115] ④ The core was injected with 2PV of oil-stabilizing and water-controlling agent in reverse and kept at a constant temperature in a constant temperature chamber for 24 hours.

[0116] ⑤ Repeat steps ② and ③ to obtain the water phase permeability after sealing. K wb and oil phase permeability K ob ;

[0117] ⑥ Calculate the residual resistance coefficient of the aqueous phase ( RRFw1 ), oil phase residual drag coefficient ( RRF o1 ) and the selectivity index (denoted as d 1 );

[0118] ⑦ Simulated formation brine was injected into the core at a constant flow rate, with an injection volume of 100 PV.

[0119] ⑧ After the injection of simulated formation brine is completed, simulated crude oil is injected into the core at a constant flow rate, and the oil phase permeability under the bound water saturation level after the cumulative injection of simulated formation brine in step ⑦ is measured. K oc ;

[0120] ⑨ Simulated brine is injected into the core at a constant flow rate, and the water phase permeability is measured at the residual oil saturation level after the cumulative injection of simulated formation brine in step ⑦. K wc ;

[0121] ⑩ Calculate the residual resistance coefficient of the aqueous phase ( RRF w2 ), oil phase residual drag coefficient ( RRF o2 ) and the selectivity index (denoted as d 2 );

[0122] Referring to the literature (Liu Jianxin, Research and Application of Relative Permeability Improvers, China University of Petroleum, 2009, Master's Thesis), the residual resistance coefficient ( RRF ) and selectivity index ( d This method is used to evaluate the plugging ability and oil-water selectivity of oil stabilizers and water control agents. Generally, the selectivity index... d The value represents the degree to which the permeability of the aqueous and oil phases decreases at different proportions, taking into account both the extent of the decrease in aqueous phase permeability and the extent of the decrease in oil phase permeability. Its value ranges from 0 to 1. d The larger the value, the better the selectivity of oil and water control.

[0123] The residual resistance coefficient is defined as the ratio of core permeability before and after water control treatment, and is a dimensionless number. The residual resistance coefficient reflects the change in core permeability before and after water control, characterizing the ability of oil-stabilizing and water-controlling agents to reduce the permeability of porous media. It is an important indicator of the ability of constant-volume oil-stabilizing and water-controlling agents to plug porous media. Typically, the residual resistance coefficient values ​​for the oil phase and water phase differ, and the magnitude of this difference characterizes the selectivity of the oil-stabilizing and water-controlling agent. Residual resistance coefficient ( RRF ) and selectivity index ( d The calculation formula is shown in equation 8-13 below: (8);

[0124] (9);

[0125] (10);

[0126] (11);

[0127] (12);

[0128] (13);

[0129] In Equation 8-13, RRF w1 、RRF o1 These represent the residual drag coefficients of the aqueous phase and the oil phase, respectively. K wa 、K oa These represent the permeability of the aqueous and oil phases before plugging, respectively, in μm. 2 ; K wb 、K ob The permeability of the aqueous and oil phases after plugging are shown in μm, respectively. 2 ; d 1 It is a selective index, used as an evaluation indicator for the effect of stabilizing oil and controlling water. RRF w2 、RRF o2 These represent the residual resistance coefficients of the aqueous and oil phases after 100PV of flushing; K wc 、K oc The permeability of the aqueous and oil phases, respectively, after flushing with 100 PV of sealant, is shown in μm. 2 ; d 2 It is a selective index, serving as an indicator of the long-term effectiveness of scouring.

[0130] The selectivity and long-lasting scouring resistance of the obtained oil stabilizer and water control agent in improving oil-water interpenetration were measured and evaluated. The results are shown in Tables 2 and 3.

[0131] Table 2 Evaluation results of the oil-water phase penetration improvement ability and selectivity of the oil stabilizer and water control agent

[0132] ;

[0133] As can be seen from the test results in Table 2, the oil-stabilizing and water-controlling agents prepared in Examples 1-5 of this invention have a residual resistance coefficient in the aqueous phase ( ). RRF w1The oil phase residual drag coefficient is between 10.42 and 12.70. RRF o1 The selectivity index ranges from 1.16 to 1.30. d 1 The value was 0.68–0.78, indicating that this oil-water stabilizer significantly reduced the permeability of the aqueous phase while having little impact on the oil phase, demonstrating good oil-water selectivity. In contrast, Comparative Examples 1-5 (which lacked cationic monomers, hydrophobic monomers, or both, or had inappropriate molecular weight regulators, respectively) d 1 The values ​​are generally below 0.34, and even close to 0.01, indicating that the synergistic effect of the cationic adsorbent monomer and the nonionic hydrophobic monomer in this invention is crucial for achieving selective blocking.

[0134] Table 3 Evaluation results of the long-term erosion resistance of oil stabilizers and water control agents.

[0135] ;

[0136] As shown in Table 3, the oil-stabilizing and water-controlling agents prepared in Examples 1-5 of this invention, after being flushed by 100PV of high-salinity formation water, have a low residual resistance coefficient in the aqueous phase ( ). RRF w2 The residual drag coefficient of the oil phase remains at 9.60–11.40. RRF o2 The selectivity index is 1.21–1.35. d 2 The value remained between 0.65 and 0.74, compared to the initial value. d 1 The limited decrease compared to the control of water and oil indicates that this oil stabilizer and water control agent exhibits good erosion resistance and long-term stability under high-salt, high-hardness formation water conditions. In contrast, the control agents in proportions 1-5... d 2 The selectivity was mostly below 0.20, and the selectivity decreased significantly after rinsing, which further confirms the contribution of the hydrophobic association structure and ionic monomer synergy in maintaining the long-term oil-water regulation capability in this invention.

[0137] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A high-salt-resistant polymer oil stabilizer and water-controlling agent, characterized in that, Its raw materials include: acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, cationic adsorption monomer, acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer, low-temperature composite initiator, molecular weight regulator, quick-dissolving agent and water; wherein, the mass ratio of the acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, cationic adsorption monomer and acrylate-terminated Goerbert alcohol polyoxyethylene ether nonionic hydrophobic monomer is 1:(0.15~0.25):(0.02~0.05):(0.03~0.1):(0.005~0.02); The salt-resistant monomer containing sulfonic acid groups is selected from at least one of sodium 2-acrylamido-2-methylpropanesulfonate, sodium vinylbenzenesulfonate, sodium acrylamidebenzenesulfonate, and sodium 5-vinylnaphthalenesulfonate. The cationic adsorption monomer is selected from trimethylallylammonium chloride or dimethyldiallylammonium chloride; The general structural formula of the acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer is shown in Formula 3: Formula 3 In Formula 3, the number of ethylene oxides m = 5~10; R1 is an alkyl group with a carbon chain length of 8 or 10; R2 is an alkyl group with a carbon chain length of 10 or 12. The instant dissolving agent is β-cyclodextrin.

2. The high-salt-resistant polymer oil stabilizer and water-controlling agent according to claim 1, characterized in that, The amount of the quick-dissolving agent is 0.01% to 0.02% of the total mass of the five monomers.

3. The high-salt-resistant polymer oil stabilizer and water-controlling agent according to claim 1, characterized in that, The molecular weight regulator is selected from at least one of sodium formate, n-butanethiol, sodium hypophosphite, and urea, and is used in an amount of 0.1% to 0.3% of the total mass of the five monomers.

4. The high-salt-resistant polymer oil stabilizer and water-controlling agent according to claim 1, characterized in that, The low-temperature composite initiator includes: Catalyst: Selected from manganese sulfate or cerium ammonium nitrate, the amount used is 0.001%~0.003% of the total mass of the five monomers; Reducing agent: selected from sodium bisulfite or sodium sulfite, used in an amount of 0.005%~0.0125% of the total mass of the five monomers; Oxidizing agent: selected from ammonium persulfate, sodium persulfate or hydrogen peroxide, and the amount used is 0.003% to 0.005% of the total mass of the five monomers.

5. The preparation method of the high-salt-resistant polymer oil stabilizer and water-controlling agent according to any one of claims 1 to 4, characterized in that, Includes the following steps: 1) Dissolve acrylamide monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, cationic adsorption monomer, and acrylate-terminated Gelbert alcohol polyoxyethylene ether nonionic hydrophobic monomer in water, adjust the pH to 7.0~8.5, and obtain a mixed solution with a total monomer concentration of 25%~30%; 2) Cool the system temperature of the mixed solution to -5~0℃, add molecular weight regulator and quick-dissolving agent, stir with nitrogen gas, add low temperature composite initiator, and polymerize under adiabatic conditions for 3~6 hours to obtain the target polymer; 3) The target polymer is dried, pulverized and sieved to obtain a high-salt resistant polymer oil stabilizer and water control agent with a viscosity-average molecular weight of 1 million to 3 million and a particle size of 100 to 140 mesh.

6. The application of the high-salt-resistant polymer oil stabilizer and water control agent as described in any one of claims 1 to 4 in oilfield water control and production enhancement.

7. A method for improving the oil recovery rate of high-salinity, high-hardness reservoirs, characterized in that, This includes injecting the high-salt-resistant polymer oil stabilizer and water control agent as described in any one of claims 1 to 4 into the target formation.

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