Environmentally friendly carbon dioxide thickener and preparation method thereof

Abstract

The present invention provides a method for preparing an environmentally friendly carbon dioxide thickener. The method comprises first mixing an acrylate compound, vinyltrimethoxysilane, an initiator, and an emulsifier, and then conducting a first polymerization reaction to obtain an intermediate. The intermediate, an aromatic diisocyanate, an organic solvent, and a catalyst are then mixed, followed by a second polymerization reaction. The mixture is then distilled and granulated to obtain the environmentally friendly carbon dioxide thickener. The environmentally friendly carbon dioxide thickener has an interwoven network structure, and the organic silicon segments and aromatic rings contained in the structure coordinately enhance the thickening effect of the thickener. Furthermore, the thickener contains no organic solvents, which facilitates storage, transportation, and environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield mining additives, and in particular to an environmentally friendly carbon dioxide thickener and a preparation method thereof. Background Art

[0002] With the deepening of oil and gas field exploration and development, low-permeability reservoirs are becoming an increasingly important component of the oil and gas industry. The rational and efficient development of low-permeability reservoirs has become increasingly important. Low-permeability reservoirs are characterized by low reservoir permeability and insufficient natural energy. Relying on natural energy for production leads to rapid depletion of elastic energy, quickly transitioning to the inefficient and long-term solution gas drive phase, resulting in rapid declines in well production and low development levels. To improve the development of low-permeability reservoirs, injecting fluids to replenish energy in the formation is a natural approach. Conventional waterflooding, however, struggles to meet the development needs of low-permeability reservoirs, often resulting in difficulties in injection and production. Consequently, gas injection has gradually become the primary method for developing tight oil reservoirs.

[0003] Carbon dioxide flooding technology has been used overseas for many years and has become a relatively mature oil recovery technique. It ensures high oil field recovery rates and is one of the technical components for effectively utilizing oilfield reserves. In the 1990s, my country began researching, developing, and piloting carbon dioxide flooding technology.

[0004] During CO2 flooding, pressurized CO2 is injected into the reservoir, reducing crude oil viscosity and water mobility. This improves the oil-to-water mobility ratio, expands the affected area, and increases flooding efficiency. Furthermore, it enables long-term CO2 storage. This not only achieves the social benefit of CO2 emissions reduction but also generates significant economic benefits. Therefore, exploring and developing field-specific CO2 flooding technologies to enhance residual oil recovery is of great practical significance.

[0005] However, CO2 gas crosstalk is one of the most serious problems in field applications. Reservoir permeability, planar heterogeneity, and fracture development all influence CO2 gas crosstalk. Once crosstalk occurs, CO2 can penetrate along the fractures, significantly reducing the volume swept by the gas and severely impacting oil recovery. Therefore, controlling and delaying CO2 gas crosstalk in fractures is a key area of CO2 flooding research. Current technologies for controlling CO2 gas crosstalk, in addition to improving reservoir conditions and sealing high-permeability layers, primarily involve adjusting CO2 viscosity, i.e., adding CO2 thickeners.

[0006] Currently, commonly used carbon dioxide thickeners are fluorine-containing compounds or polymers. However, fluorine-containing polymers have excellent thickening effects when used as thickeners, but they are prone to interacting with groundwater and remaining in reservoirs, polluting medium and high permeability reservoirs and water resources, and then circulating in the biosphere, thereby damaging the environment. They can also accumulate in the body and cause accumulation of substances in the biosphere, which can cause great damage to the formation, pollute groundwater resources, cause environmental pollution, have high biological toxicity, and fluorine-containing substances are expensive. Silicon-containing polymers are a type with relatively ideal cost-effectiveness, but they contain a large amount of organic solvents, which are not conducive to storage, transportation and environmental protection. Therefore, providing an environmentally friendly carbon dioxide thickener with excellent thickening effect is a problem that the existing technology urgently needs to solve. Summary of the Invention

[0007] The object of the present invention is to provide an environmentally friendly carbon dioxide thickener and a preparation method thereof. The carbon dioxide thickener prepared by the method provided by the present invention is green and environmentally friendly and has good thickening performance.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing an environmentally friendly carbon dioxide thickener, comprising the steps of:

[0010] (1) mixing an acrylate compound, vinyltrimethoxysilane, an initiator, and an emulsifier, and performing a first polymerization reaction to obtain an intermediate;

[0011] (2) mixing the intermediate obtained in step (1) with an aromatic diisocyanate, an organic solvent, and a catalyst, and performing a second polymerization reaction to obtain a polymer;

[0012] (3) The polymer obtained in step (2) is sequentially distilled and granulated to obtain an environmentally friendly carbon dioxide thickener.

[0013] Preferably, the acrylate compound in step (1) is at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate and 2-ethylhexyl acrylate.

[0014] Preferably, the initiator in step (1) is at least one of hydrogen peroxide, ammonium persulfate or potassium persulfate.

[0015] Preferably, the emulsifier in step (1) is at least one of polyoxyethylene ether, polyoxypropylene ether, ethylene oxide and polyvinyl alcohol.

[0016] Preferably, the temperature of the first polymerization reaction in step (1) is 80-100° C., and the time of the first polymerization reaction is 4-8 hours.

[0017] Preferably, the aromatic diisocyanate in step (2) is at least one of toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, diphenylmethane 4,4'-diisocyanate, diphenylmethane 2,4'-diisocyanate and diphenylmethane 2,2'-diisocyanate.

[0018] Preferably, the organic solvent in step (2) is at least one of toluene, cyclohexane, dimethyl ether, methyl formate, ethyl formate, acetone and methyl ethyl ketone.

[0019] Preferably, the catalyst in step (2) is at least one of dimethylamine, triethanolamine, imidazole, tributyltin and dibutyltin dilaurate.

[0020] Preferably, the temperature of the second polymerization reaction in step (2) is 80 to 120° C., and the time of the second polymerization reaction is 4 to 12 hours.

[0021] The present invention also provides an environmentally friendly carbon dioxide thickener prepared by the preparation method described in the above technical solution.

[0022] The present invention provides a method for preparing an environmentally friendly carbon dioxide thickener. First, an acrylic acid ester compound, vinyl trimethoxysilane, an initiator, and an emulsifier are mixed, and a first polymerization reaction is carried out to obtain an intermediate. Then, the intermediate, an aromatic diisocyanate, an organic solvent, and a catalyst are mixed, and a second polymerization reaction is carried out. Then, distillation and granulation are carried out in sequence to obtain an environmentally friendly carbon dioxide thickener. The preparation method provided by the present invention provides an environmentally friendly carbon dioxide thickener having an interwoven network structure, and the organic silicon segments and aromatic rings contained in its structure coordinately improve the thickening effect of the thickener, and do not contain organic solvents, which is beneficial for storage, transportation, and environmental protection. The results of the embodiment show that under the same pressure and temperature conditions, when 2wt% and 4wt% of the environmentally friendly carbon dioxide thickener are added, respectively, the carbon dioxide viscosity can reach 5.41mPa·s and 9.94mPa·s, which is much higher than the initial viscosity of carbon dioxide. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing an environmentally friendly carbon dioxide thickener, comprising the steps of:

[0024] (1) mixing an acrylate compound, vinyltrimethoxysilane, an initiator, and an emulsifier, and performing a first polymerization reaction to obtain an intermediate;

[0025] (2) mixing the intermediate obtained in step (1) with an aromatic diisocyanate, an organic solvent, and a catalyst, and performing a second polymerization reaction to obtain a polymer;

[0026] (3) The polymer obtained in step (1) is sequentially distilled and granulated to obtain an environmentally friendly carbon dioxide thickener.

[0027] In the present invention, an acrylate compound, vinyltrimethoxysilane, an initiator and an emulsifier are mixed and then subjected to a first polymerization reaction to obtain an intermediate.

[0028] In the present invention, the acrylic acid ester compound is preferably at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate and 2-ethylhexyl acrylate.

[0029] In the present invention, the initiator is preferably at least one of hydrogen peroxide, ammonium persulfate or potassium persulfate.

[0030] In the present invention, the emulsifier is at least one of polyoxyethylene ether, polyoxypropylene ether, ethylene oxide and polyvinyl alcohol.

[0031] In the present invention, the mass ratio of the acrylate compound, vinyltrimethoxysilane, initiator, and emulsifier is preferably (1-40):(1-50):(0.002-0.3):(0.2-4), and more preferably (5-35):(4-45):(0.003-0.25):(0.25-3). The mass ratio of the acrylate compound, vinyltrimethoxysilane, initiator, and emulsifier is controlled within the above range to promote sufficient reaction of the components, thereby facilitating improved thickening performance of the subsequently prepared thickener.

[0032] The present invention has no particular limitation on the mixing method, and any mixing scheme well known in the art may be used.

[0033] In the present invention, the temperature of the first polymerization reaction is preferably 80-100°C, more preferably 85-95°C. In the present invention, the time of the first polymerization reaction is preferably 4-8 hours, more preferably 5-7 hours. In the present invention, the temperature and time of the first polymerization reaction are controlled within the above ranges to promote sufficient reaction of the components, thereby facilitating improved thickening performance of the subsequently prepared thickener.

[0034] After the first polymerization reaction is completed, the product of the first polymerization reaction is mixed with gasoline, and then filtered, extracted and dried in sequence to obtain an intermediate.

[0035] The volume of gasoline used in the present invention is not particularly limited, as long as the product of the first polymerization reaction is completely precipitated. The filtration method is not particularly limited, and any filtration method known in the art can be employed. In the present invention, the extraction reagent is preferably n-hexane, and the number of extractions is preferably 3 to 5. The drying method is not particularly limited, and any drying method known in the art can be employed.

[0036] After obtaining the intermediate, the present invention mixes the intermediate with an aromatic diisocyanate, an organic solvent and a catalyst, and then performs a second polymerization reaction to obtain a polymer;

[0037] In the present invention, the aromatic diisocyanate is preferably at least one of toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, diphenylmethane 4,4′-diisocyanate, diphenylmethane 2,4′-diisocyanate and diphenylmethane 2,2′-diisocyanate.

[0038] In the present invention, the organic solvent is preferably at least one of cyclohexane, dimethyl ether, methyl formate, ethyl formate, acetone and methyl ethyl ketone.

[0039] In the present invention, the catalyst is at least one of dimethylamine, triethanolamine, imidazole, tributyltin and dibutyltin dilaurate.

[0040] In the present invention, the mass ratio of the intermediate, aromatic diisocyanate, and catalyst is preferably (10-120):(3-50):(0.03-3), and more preferably (15-110):(4-46):(0.04-2.8). The present invention controls the mass ratio of the intermediate, aromatic diisocyanate, and catalyst within the above range to promote sufficient reaction of the components, thereby improving the thickening performance of the subsequently prepared thickener.

[0041] In the present invention, the temperature of the second polymerization reaction is preferably 80-120°C, more preferably 85-115°C; and the duration of the second polymerization reaction is preferably 4-12 hours, more preferably 5-11 hours. In the present invention, the temperature and duration of the second polymerization reaction are controlled within the above ranges to promote sufficient reaction of the components, thereby facilitating improved thickening properties of the subsequently prepared thickener.

[0042] After obtaining the polymer, the present invention sequentially distills and granulates the polymer to obtain an environmentally friendly carbon dioxide thickener.

[0043] The present invention does not specifically limit the distillation method; distillation protocols well known in the art may be employed. In the present invention, the particle size of the granulated particles is preferably 50 to 70 μm, more preferably 55 to 68 μm. The particle size of the granulated particles is controlled within this range to enable the environmentally friendly carbon dioxide thickener to fully exert its thickening effect during use.

[0044] The present invention also provides an environmentally friendly carbon dioxide thickener prepared by the preparation method described in the above technical solution.

[0045] The present invention provides a method for preparing an environmentally friendly carbon dioxide thickener. The method comprises first mixing an acrylate compound, vinyltrimethoxysilane, an initiator, and an emulsifier, followed by a first polymerization reaction to obtain an intermediate. The intermediate, an aromatic diisocyanate, an organic solvent, and a catalyst are then mixed, followed by a second polymerization reaction. The mixture is then distilled and granulated to obtain the environmentally friendly carbon dioxide thickener. The environmentally friendly carbon dioxide thickener prepared by the preparation method contains long organosilicon segments and aromatic rings, exhibits excellent thickening properties, and is free of organic solvents, facilitating storage, transportation, and environmental protection.

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] Example 1

[0048] Preparation method of environmentally friendly carbon dioxide thickener:

[0049] (1) Under stirring conditions, 10 parts by weight of n-butyl acrylate, 30 parts by weight of vinyltrimethoxysilane, 0.004 parts by weight of initiator potassium persulfate, and 0.5 parts by weight of emulsifier polyvinyl alcohol are mixed, and a first polymerization reaction is carried out at 95° C. for 5 hours. After the reaction is completed, the product of the first polymerization reaction is mixed with gasoline, and then filtered, extracted, and dried in sequence to obtain an intermediate;

[0050] The mass ratio of n-butyl acrylate, vinyltrimethoxysilane, initiator and emulsifier is 10:30:0.004:0.5;

[0051] (2) under stirring conditions, mixing 100 parts by weight of the intermediate obtained in step (1) with 30 parts by weight of toluene 2,4-diisocyanate, 110 parts by weight of acetone as an organic solvent, and 0.04 parts by weight of triethanolamine as a catalyst, and conducting a second polymerization reaction at 100° C. for 6 hours to obtain a polymer;

[0052] The mass ratio of the intermediate, toluene 2,4-diisocyanate and catalyst is 100:30:0.04;

[0053] (3) The polymer obtained in step (2) is subjected to vacuum distillation to remove the solvent, cooled to room temperature and subjected to shear granulation to obtain an environmentally friendly carbon dioxide thickener with a particle size of 55 μm.

[0054] Example 2

[0055] Preparation method of environmentally friendly carbon dioxide thickener:

[0056] (1) Under stirring conditions, 10 parts by weight of ethyl acrylate, 30 parts by weight of vinyltrimethoxysilane, 0.004 parts by weight of initiator potassium persulfate, and 0.5 parts by weight of emulsifier polyvinyl alcohol are mixed, and a first polymerization reaction is carried out at 95° C. for 5 hours. After the reaction is completed, the product of the first polymerization reaction is mixed with gasoline, and then filtered, extracted, and dried in sequence to obtain an intermediate;

[0057] The mass ratio of the ethyl acrylate, vinyltrimethoxysilane, initiator and emulsifier is 10:30:0.004:0.5;

[0058] (2) under stirring conditions, mixing 100 parts by weight of the intermediate obtained in step (1) with 30 parts by weight of toluene 2,4-diisocyanate, 110 parts by weight of acetone as an organic solvent, and 0.04 parts by weight of triethanolamine as a catalyst, and conducting a second polymerization reaction at 100° C. for 6 hours to obtain a polymer;

[0059] The mass ratio of the intermediate, toluene 2,4-diisocyanate and catalyst is 100:30:0.04;

[0060] (3) The polymer obtained in step (2) is subjected to vacuum distillation to remove the solvent, cooled to room temperature and subjected to shear granulation to obtain an environmentally friendly carbon dioxide thickener with a particle size of 55 μm.

[0061] Example 3

[0062] Preparation method of environmentally friendly carbon dioxide thickener:

[0063] (1) Under stirring conditions, 10 parts by weight of n-butyl acrylate, 30 parts by weight of vinyltrimethoxysilane, 0.004 parts by weight of initiator potassium persulfate, and 0.5 parts by weight of emulsifier polyvinyl alcohol are mixed, and a first polymerization reaction is carried out at 95° C. for 5 hours. After the reaction is completed, the product of the first polymerization reaction is mixed with gasoline, and then filtered, extracted, and dried in sequence to obtain an intermediate;

[0064] The mass ratio of n-butyl acrylate, vinyltrimethoxysilane, initiator and emulsifier is 10:30:0.004:0.5;

[0065] (2) under stirring conditions, mixing 110 parts by weight of the intermediate obtained in step (1) with 40 parts by weight of diphenylmethane 2,4'-diisocyanate, 120 parts by weight of acetone as an organic solvent, and 0.04 parts by weight of triethanolamine as a catalyst, and conducting a second polymerization reaction at 100° C. for 6 hours to obtain a polymer;

[0066] The mass ratio of the intermediate, diphenylmethane 2,4'-diisocyanate and catalyst is 110:40:0.04;

[0067] (3) The polymer obtained in step (2) is subjected to vacuum distillation to remove the solvent, cooled to room temperature and subjected to shear granulation to obtain an environmentally friendly carbon dioxide thickener with a particle size of 55 μm.

[0068] Example 4

[0069] Preparation method of environmentally friendly carbon dioxide thickener:

[0070] (1) Under stirring conditions, 10 parts by weight of ethyl acrylate, 30 parts by weight of vinyltrimethoxysilane, 0.004 parts by weight of initiator potassium persulfate, and 0.5 parts by weight of emulsifier polyvinyl alcohol are mixed, and a first polymerization reaction is carried out at 95° C. for 5 hours. After the reaction is completed, the product of the first polymerization reaction is mixed with gasoline, and then filtered, extracted, and dried in sequence to obtain an intermediate;

[0071] The mass ratio of the ethyl acrylate, vinyltrimethoxysilane, initiator and emulsifier is 10:30:0.004:0.5;

[0072] (2) under stirring conditions, mixing 110 parts by weight of the intermediate obtained in step (1) with 40 parts by weight of diphenylmethane 2,4'-diisocyanate, 110 parts by weight of acetone as an organic solvent, and 0.04 parts by weight of triethanolamine as a catalyst, and conducting a second polymerization reaction at 100° C. for 6 hours to obtain a polymer;

[0073] The mass ratio of the intermediate, diphenylmethane 2,4'-diisocyanate and catalyst is 110:40:0.04;

[0074] (3) The polymer obtained in step (2) is subjected to vacuum distillation to remove the solvent, cooled to room temperature and subjected to shear granulation to obtain an environmentally friendly carbon dioxide thickener with a particle size of 55 μm.

[0075] The environmentally friendly carbon dioxide thickeners prepared in Examples 1 to 4 were mixed with carbon dioxide, with the addition amounts of the carbon dioxide thickeners being 2 wt % and 4 wt %, respectively. The viscosity-increasing effect of the carbon dioxide thickeners was tested using a falling ball viscometer at 35° C. and 10 MPa. The specific results are shown in Table 1.

[0076] Table 1 Test conditions and effects of carbon dioxide thickener

[0077]

[0078] In summary, under certain pressure and temperature conditions, the viscosity of the carbon dioxide prepared by adding 2wt% and 4wt% of an environmentally friendly carbon dioxide thickener can reach 5.41mPa·s and 9.94mPa·s, respectively, significantly exceeding the initial viscosity of the carbon dioxide. The environmentally friendly carbon dioxide thickener prepared by the preparation method provided herein contains long organosilicon chains and aromatic rings, exhibiting excellent thickening properties and being free of organic solvents, thus facilitating storage, transportation, and environmental protection.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly carbon dioxide thickener, comprising the steps of: (1) mixing an acrylate compound, vinyltrimethoxysilane, an initiator, and an emulsifier, and performing a first polymerization reaction to obtain an intermediate; In step (1), the acrylate compound is at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate and 2-ethylhexyl acrylate; In step (1), the initiator is at least one of hydrogen peroxide, ammonium persulfate or potassium persulfate; In the step (1), the emulsifier is at least one of polyoxyethylene ether, polyoxypropylene ether, ethylene oxide and polyvinyl alcohol; The mass ratio of the acrylic acid ester compound, vinyltrimethoxysilane, initiator and emulsifier is (5-35): (4-45): (0.003-0.25): (0.25-3); The temperature of the first polymerization reaction in step (1) is 80-100° C., and the time of the first polymerization reaction is 4-8 hours; (2) mixing the intermediate obtained in step (1) with an aromatic diisocyanate, an organic solvent, and a catalyst, and performing a second polymerization reaction to obtain a polymer; In the step (2), the aromatic diisocyanate is toluene 2,4-diisocyanate; The organic solvent in step (2) is at least one of cyclohexane, dimethyl ether, methyl formate, ethyl formate, acetone and methyl ethyl ketone; The catalyst in step (2) is at least one of dimethylamine, triethanolamine, imidazole, tributyltin and dibutyltin dilaurate; The mass ratio of the intermediate, toluene 2,4-diisocyanate and catalyst is 100:30:0.04; The temperature of the second polymerization reaction in step (2) is 80 to 120° C., and the time of the second polymerization reaction is 4 to 12 hours; (3) The polymer obtained in step (2) is sequentially distilled and granulated to obtain an environmentally friendly carbon dioxide thickener.

2. The environmentally friendly carbon dioxide thickener prepared by the preparation method according to claim 1.

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