A carbon dioxide enhanced oil recovery agent, its preparation method and application

Abstract

This invention provides a carbon dioxide enhanced oil recovery (EOR) additive, its preparation method, and its application. The EOR additive, based on 1 part by weight of modified siloxane, comprises the following components: 1 part by weight of modified siloxane; 0.1-10 parts by weight of ester; 0.1-10 parts by weight of hydrocarbon amine; and 0-100 parts by weight of solvent. The modified siloxane has the structural formula shown in formula (I): wherein R1 is a C1-C8 alkyl group, preferably a C1-C4 alkyl group; R2 is H or a C1-C4 alkyl group, preferably H or a C1-C2 alkyl group; R3 is H or a C1-C20 alkyl group, preferably H or a C1-C4 alkyl group; m is an integer from 1 to 10, preferably an integer from 1 to 4; and n is an integer from 0 to 10, preferably an integer from 0 to 4. The CO2 EOR additive prepared by this invention can reduce the CO2 / oil miscibility pressure by more than 10%, thereby improving CO2 oil displacement efficiency.

Description

Technical Field

[0001] This invention relates to the field of oilfield production, and more specifically, to a carbon dioxide enhanced oil recovery agent, its preparation method, and its application. Background Technology

[0002] CCUS is a new development trend in CCS (Carbon Capture and Storage) technology. It involves purifying carbon dioxide emitted during production processes and then reusing it in new production processes, allowing for recycling rather than simple storage. Compared to CCS, CCUS can turn carbon dioxide into a resource, generating economic benefits and making it more practical. It can be divided into capture, transport, utilization, and storage stages. CO2 utilization refers to using the physical, chemical, or biological effects of CO2 to reduce CO2 emissions while simultaneously increasing energy production and efficiency, improving mineral resource extraction, converting and synthesizing chemicals, increasing the production and utilization of bio-agricultural products, and utilizing CO2 in consumer goods production. It is an emission reduction approach with incidental economic benefits.

[0003] Among numerous CO2 utilization projects, carbon dioxide enhanced oil recovery (CEOR) has become one of the important technologies for enhanced oil recovery. The United States is the country that first and most widely applied CEOR trials. Since 1970, the US has been using carbon dioxide injection into oil fields in Texas as a technique for enhanced oil recovery (EOR), injecting a total of 20-30 million tons of carbon dioxide annually. Approximately 3 million tons of this carbon dioxide comes from the tail gas of coal gasification plants and fertilizer plants, with the majority extracted from natural carbon dioxide gas reservoirs. This technology is still in use today. CO2-EOR miscible CEOR enhances oil recovery in the range of 4-12%. CO2-EOR immiscible CEOR projects are fewer and their benefits are relatively lower.

[0004] Although CO2-EOR miscible displacement efficiency is higher than that of immiscible displacement, the pressure in domestic oil reservoirs often cannot reach the miscibility pressure of CO2 / crude oil. Therefore, it is necessary to study a method to reduce the miscibility pressure of CO2 / crude oil and improve the efficiency of CO2 displacement. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a carbon dioxide enhanced oil recovery (EOR) additive, its preparation method, and its application. The carbon dioxide EOR additive prepared by this invention is used to reduce the miscibility pressure of CO2 / crude oil.

[0006] This invention prepares modified siloxanes. By optimizing the structure of traditional siloxanes, their high surface activity is retained. The introduction of EO / PO fragments can adjust the solubility of chemical agents in CO2, thereby assisting injection. On the other hand, the introduction of esters and hydrocarbon amines effectively enhances the interaction between CO2 and crude oil, thereby effectively reducing the mutual pressure between CO2 and crude oil and achieving miscible flooding.

[0007] This invention prepares a CO2 enhanced oil recovery (EOR) additive by compounding modified siloxanes, esters, and hydrocarbon amines. This enhances the interaction between CO2 and crude oil, thereby reducing the CO2 / oil miscibility pressure by more than 10%, ultimately achieving CO2 / crude oil miscibility flooding and improving CO2 flooding efficiency. Furthermore, the CO2 EOR additive of this invention shows no significant changes in its main structure after aging for 24 hours at 90°C and pH 4-7, exhibiting good acid resistance. Therefore, the CO2 EOR additive composition of this invention can adapt to actual operating conditions of CO2 huff and puff and CO2 flooding.

[0008] One objective of this invention is to provide a carbon dioxide enhanced oil recovery (EOR) additive, comprising the following components based on 1 part by weight of modified siloxane:

[0009]

[0010] The hydrocarbon amine is preferably in the range of any two values ​​consisting of 0.1, 0.3, 0.5, 0.8, or 1 parts by weight or more, such as 0.1 to 0.5 parts by weight; the solvent is preferably in the range of any two values ​​consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by weight or more, such as 1 to 2 parts by weight; the hydrocarbon amine is more preferably an alkylamine.

[0011] The structural formula of the modified siloxane is shown in formula (I):

[0012]

[0013] Wherein, R1 is an alkyl group of C1 to C8, preferably an alkyl group of C1 to C4; R2 is an alkyl group of H or C1 to C4, preferably an alkyl group of H or C1 to C2; R3 is an alkyl group of H or C1 to C20, preferably an alkyl group of H or C1 to C4; m is an integer from 1 to 10, preferably an integer from 1 to 4; n is an integer from 0 to 10, preferably an integer from 0 to 4.

[0014] In a preferred embodiment of the present invention,

[0015] The modified siloxane is obtained by a preparation method comprising the following steps:

[0016] (1) Compound (II) reacts with halopropylene in the presence of base and catalyst I, and after post-treatment, compound (II) is obtained.

[0017] The structural formula of the compound of formula (II) is:

[0018] The structural formula of the compound of formula (II) is:

[0019] Wherein, R3 is H or a C1-C20 alkyl group, preferably H or a C1-C4 alkyl group; m is an integer from 1 to 10, preferably an integer from 1 to 4; n is an integer from 0 to 10, preferably an integer from 0 to 4;

[0020] (2) The obtained compound of formula (II) is reacted with an organosiloxane in the presence of catalyst II, and the modified siloxane is obtained after post-treatment II.

[0021] In a preferred embodiment of the present invention,

[0022] In step (1),

[0023] The halopropylene is at least one of allyl chloride, allyl bromopropene, and allyl iodopropene; and / or,

[0024] The base is at least one of inorganic bases and organic bases; and / or,

[0025] The catalyst I is a phase transfer catalyst, preferably an alkyl halide ammonium salt, more preferably at least one of tetrabutylammonium bromide and tetrabutylammonium iodide; and / or

[0026] The post-processing includes separation and purification steps.

[0027] In a preferred embodiment of the present invention,

[0028] In step (2),

[0029] The structural formula of the organosiloxane is shown in Formula (IV):

[0030]

[0031] Wherein, R1 is a C1-C8 alkyl group, preferably a C1-C4 alkyl group; R2 is H or a C1-C4 alkyl group, preferably H or a C1-C2 alkyl group; and / or,

[0032] Catalyst II is a noble metal catalyst, preferably a platinum catalyst, and more preferably chloroplatinic acid; and / or

[0033] The second post-processing step includes separation and purification steps.

[0034] In a preferred embodiment of the present invention,

[0035] In step (1),

[0036] The reaction is carried out under a protective gas atmosphere, wherein the protective gas is at least one selected from nitrogen and an inert gas; and / or,

[0037] The reaction temperature is 25–120°C, preferably 60–90°C; and / or,

[0038] The reaction time is 2–24 h, preferably 4–8 h; and / or,

[0039] The molar ratio of compound (II), halopropylene, base, and catalyst I is 1:(1-5):(1-10):(0.01-0.1), preferably 1:(1-2):(2-5):(0.05-0.1), and more preferably 1:(1.5-2):(4-5):(0.05-0.1).

[0040] In a preferred embodiment of the present invention,

[0041] In step (2),

[0042] First, the solution of compound (II) and catalyst II is mixed and activated by heating, and then an organosiloxane is added; preferably, the activation temperature is 50-70°C and the activation time is 20-40 min; and / or, the solvent in the solution of catalyst II is at least one selected from methanol, isopropanol, isobutanol, toluene, and benzene; and / or,

[0043] The reaction is carried out under a protective gas atmosphere, wherein the protective gas is at least one selected from nitrogen and an inert gas; and / or,

[0044] The reaction temperature is 25–150°C, preferably 80–120°C; and / or,

[0045] The reaction time is 2–24 h, preferably 6–12 h; and / or,

[0046] The molar ratio of compound (II) of formula, organosiloxane, and catalyst II is 1:(1-2):(0.0005-0.05), preferably 1:(1-2):(0.0005-0.01), and more preferably 1:(1.5-2):(0.0005-0.001).

[0047] In a preferred embodiment of the present invention,

[0048] The ester is composed of one or more of formulas (IV) to (VII);

[0049]

[0050] Among them, R4, R5, R6, R7, R8, R9, R10 R 11 R 12 Each is independently selected from straight-chain or branched alkanes from C1 to C8;

[0051] Preferably, the ester is at least one selected from methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dimethyl oxalate, diethyl oxalate, dipropyl oxalate, methyl ethyl oxalate, dibutyl oxalate, dimethyl malonate, diethyl malonate, dipropyl malonate, dibutyl malonate, dimethyl succinate, diethyl succinate, dipropyl succinate, and dibutyl succinate.

[0052] In a preferred embodiment of the present invention,

[0053] The alkyl amine is at least one of the following amines with a total carbon number between 4 and 30: primary amines, secondary amines, and tertiary amines; including but not limited to straight-chain, branched, and cyclic hydrocarbons; preferably at least one of the following straight-chain or branched amines with a total carbon number between 4 and 16: primary amines, secondary amines, and tertiary amines; more preferably at least one of the following straight-chain or branched amines with a total carbon number between 4 and 14: primary amines and secondary amines; the alkyl amine is more preferably an alkylamine; and / or,

[0054] The solvent is at least one of C5-C20 straight-chain alkanes, toluene, xylene, and petroleum ether; preferably one or two, more preferably one or two of C5-C16 straight-chain alkanes, toluene, and petroleum ether.

[0055] The second objective of this invention is to provide a method for preparing a carbon dioxide enhanced oil recovery (EOR) additive, comprising the following steps:

[0056] The carbon dioxide flooding oil recovery additive is obtained by uniformly mixing the components, including modified siloxane, ester, hydrocarbon amine, and optional solvent, according to the stated weight proportions.

[0057] The third objective of this invention is to provide an application of a carbon dioxide enhanced oil recovery (EOR) additive in carbon dioxide flooding; preferably,

[0058] The carbon dioxide flooding oil recovery additive is injected together with carbon dioxide or dissolved in carbon dioxide before injection, and the injection amount of the carbon dioxide flooding oil recovery additive is 0.01 to 5 wt% of carbon dioxide.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] The CO2 oil recovery additive provided by this invention enhances the interaction between CO2 and crude oil, thereby reducing the miscibility pressure of CO2 / oil by more than 10%, ultimately achieving miscibility flooding of CO2 / crude oil and improving CO2 oil recovery efficiency.

[0061] The inventors believe that the above-mentioned technical effects are inseparable from the modified siloxanes in this invention. This invention optimizes the structure of traditional siloxanes, retains their high surface activity, and introduces EO / PO fragments to adjust the solubility of chemical agents in CO2, thereby assisting injection. On the other hand, the introduction of esters and hydrocarbon amines effectively enhances the interaction between CO2 and crude oil, thereby effectively reducing the mutual pressure between CO2 and crude oil and achieving miscible flooding. Attached Figure Description

[0062] Figure 1 CO2 phase experiment with Bao 1415 well (no chemical reagents above, composition 1 with 2% CO2 by mass below, blue indicates the corresponding experimental pressure). Detailed Implementation

[0063] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0064] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0065] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified were either readily available for purchase or prepared using methods disclosed in the prior art.

[0066] The raw materials used in the examples and comparative examples were all commercially available.

[0067] Test method:

[0068] H-NMR spectrum: Bruker 400MHz.

[0069] Surfactant interfacial tension testing: The interfacial tension of CO2 / crude oil or CO2 / crude oil / chemical agent was determined by pendant drop method using a Teclis interfacial rheometer.

[0070] Phase state experiment: The phase state changes of CO2 wettability modifier / CO2 / crude oil were studied in a supercritical visible volume system using imaging methods.

[0071] Example 1

[0072] Under N2 protection at room temperature, 200 mmol of bromopropene was slowly added dropwise to a mixture of vigorously stirred compound 1A (100 mmol), saturated KOH solution (containing 400 mmol of KOH), and tetrabutylammonium bromide (5 mmol). The mixture was then gradually heated to 80 °C and reacted for 8 h. After the reaction was complete, the mixture was cooled to room temperature, filtered, and the filtrate was washed with water, extracted with petroleum ether, and the upper organic phase was collected and dried over anhydrous MgSO4 for 24 h. The solvent and unreacted bromopropene were removed by vacuum distillation to obtain compound 1B.

[0073] Under N2 protection, a certain amount of compound 1B (100 mmol) and an isopropanol solution of chloroplatinic acid (containing 0.05 mmol of chloroplatinic acid) were added to a dry three-necked flask. The mixture was stirred and heated to 60 °C for 30 min to activate it. Then, compound 1C (150 mmol) was added dropwise, and the temperature was slowly raised to 120 °C for 8 h. After the reaction was completed, the reaction solution was washed with water to remove chloroplatinic acid and isopropanol. The organic phase was extracted with petroleum ether and dried with anhydrous MgSO4 for 12 h. The petroleum ether was then removed by vacuum distillation to obtain modified siloxane GY1.

[0074] The structural formula of modified siloxane GY1 is:

[0075]

[0076] Test results: 1 ¹H NMR (400MHz, CDCl₃, ppm): δ=3.51-3.65(m, 9H), 3.34-3.36(m, 6H), 1.47-1.51(m, 6H), 1.30-1.32(d, 3H), 0.90-0.96(t, 3H), 0.61-0.66(t, 2H), 0.21(s, 18H), 0.16(s, 3H); The structure of the obtained modified siloxane GY₁ was confirmed.

[0077] Example 2

[0078] The wetting modifier was prepared according to the method of Example 1, except that compound 2A was used instead of compound 1A in Example 1 to obtain modified siloxane GY2.

[0079] The structural formula of modified siloxane GY2 is:

[0080]

[0081] Test results: 1¹H NMR (400MHz, CDCl₃, ppm): δ=3.52-3.67(m, 20H), 3.34-3.36(m, 12H), 1.48-1.51(m, 6H), 1.30-1.32(d, 12H), 0.90-0.96(t, 3H), 0.60-0.66(m, 2H), 0.22(s, 18H), 0.15(s, 3H); The structure of the obtained modified siloxane GY₂ was confirmed.

[0082] The compounds used in Examples 1-3 and Comparative Example 1 are shown in Table 1:

[0083] Table 1. Structures of some compounds in Examples 1-3 and Comparative Example 1

[0084]

[0085] The structural formulas of compounds 1A and 2A are as follows: R3, m, and n are shown in Table 1;

[0086] Compound 1C R1 and R2 are shown in Table 1;

[0087] Examples 3-8

[0088] Preparation of CO2 oil recovery additives:

[0089] The modified siloxanes GY1 and GY2 prepared in Examples 1 and 2 were formulated with esters, hydrocarbon amines, and solvents according to the raw materials and mass fractions shown in Table 2. Examples are numbered 3 to 8, and carbon dioxide oil recovery additive compositions 1 to 6 are obtained respectively.

[0090] Comparative Examples 1-2

[0091] The modified siloxane GY1 prepared in Example 1 was mixed with esters, hydrocarbon amines, and solvents according to the raw materials and mass proportions shown in Table 2, and these were numbered Comparative Examples 1 and 2, respectively, to obtain carbon dioxide oil recovery additive compositions 7 and 8. Among these, composition 7, compared to Example 3, did not contain N,N-dimethyl-n-octylamine; composition 8, compared to Example 3, did not contain diethyl oxalate; except for the above differences, all other conditions for Comparative Examples 1 and 2 were the same as those for Example 3.

[0092] Comparative Example 3

[0093] The difference from Example 3 is that the modified siloxane is different. The modified siloxane GY1 is replaced by CO2 wettability regulator R1 prepared in Example 1 of Chinese Invention Patent CN117986284A (invention title: "A CO2 wettability regulator and its preparation method and method for regulating reservoir wettability").

[0094] Except for the differences mentioned above, the amount of ester, hydrocarbon amine, solvent and other conditions in Comparative Example 3 were the same as in Example 3, resulting in Composition 9.

[0095] Table 2 Composition of CO2 Oil Enhancement Additives

[0096]

[0097] Test Example 1

[0098] Surfactant interfacial tension test:

[0099] The interfacial tension between CO2 and crude oil (1-10 mPa·s) from the Henan Bao 1415 well under formation conditions (15 MPa, 95 °C) was measured using a Teclis interfacial rheometer. The amounts of the compositions were 0.1%, 1%, and 2% of the mass of CO2, respectively. The data are shown in Table 3.

[0100] Table 3 CO2 Oil Enhancement Additives: CO2 / Oil Interfacial Tension

[0101]

[0102] As shown in Table 3, injecting CO2 oil recovery additives can effectively reduce the interfacial tension between CO2 and crude oil in the Henan Bao 1414 well, which helps to reduce the miscibility pressure between CO2 and crude oil.

[0103] Compared with compositions 7-8, which have the same siloxane structure, compositions 1 and 7-8 respectively have eliminated esters and amines. The ability of both to reduce the CO2 / oil interfacial tension is weakened, indicating that the compound ester and amine have a significant enhancing effect on oil recovery additives.

[0104] Comparing composition 1 and composition 9, with different siloxane structures, composition 9 has a weaker ability to reduce the interfacial tension of CO2 / oil, and its performance is significantly reduced.

[0105] When the amount of composition 1 prepared in Example 3 is 0.1% to 2% of the mass of CO2, the interfacial tension is 1.98 to 2.75 mN / m, which maintains a low interfacial tension and is conducive to crude oil extraction.

[0106] Test Example 2

[0107] CO2 and crude oil phase experiment

[0108] The phase changes of CO2 and crude oil were observed using a high-temperature, high-pressure, variable-volume sight glass autoclave.

[0109] Experimental method: First, a certain amount of crude oil was injected into the reactor, and then CO2 was injected. By controlling the injection pressure, the mass ratio of crude oil to CO2 was kept constant. Then, by reducing the volume of the reactor, the pressure inside the reactor was continuously increased, and the two-phase changes of CO2 and crude oil were observed during the process.

[0110] Experimental conditions: crude oil from Bao 1415 well, temperature 40℃, CO2 to crude oil mass ratio 4:1.

[0111] The experimental results are shown in Figure 1 Even with pressure rising to 22 MPa, no miscibility between Baolang 1415 and CO2 was observed. The formation pressure in Baolang 1415 well is generally between 18-22 MPa, meaning direct CO2 injection cannot achieve miscibility or near-miscibility flooding. Adding 2% of composition 1 resulted in near-miscibility at 17.91 MPa and complete miscibility at 21.88 MPa, indicating that the chemical additive effectively reduced the miscibility pressure, achieving miscibility flooding under formation conditions. Furthermore, with the chemical additive throughout the process, low pressure helps crude oil swell and flow out from pores, while high pressure enhances extraction. Even if miscibility cannot be achieved underground due to varying formation conditions, CO2 oil recovery efficiency can still be effectively improved.

[0112] The CO2 enhanced oil recovery additives prepared in Examples 3-8 strengthen the interaction between CO2 and crude oil, thereby reducing the CO2 / oil miscibility pressure by more than 10%, ultimately achieving CO2 / crude oil miscibility flooding and improving CO2 flooding efficiency. This demonstrates that the modified siloxanes prepared in Examples 1-2 retain their high interfacial activity. The introduction of EO / PO fragments can regulate the solubility of chemical agents in CO2, thus assisting injection. On the other hand, the introduction of esters and hydrocarbon amines effectively enhances the interaction between CO2 and crude oil, thereby effectively reducing the mutual pressure between CO2 and crude oil and achieving miscibility flooding.

Claims

1. A carbon dioxide enhanced oil recovery (EOR) additive, comprising, by weight 1 part modified siloxane, the following components: The structural formula of the modified siloxane is shown in formula (I): in, R1 is an alkyl group of C1 to C8, preferably an alkyl group of C1 to C4; R2 is an alkyl group of H or C1 to C4, preferably an alkyl group of H or C1 to C2; R3 is an alkyl group of H or C1 to C20, preferably an alkyl group of H or C1 to C4; m is an integer from 1 to 10, preferably an integer from 1 to 4; n is an integer from 0 to 10, preferably an integer from 0 to 4.

2. The carbon dioxide enhanced oil recovery agent as described in claim 1, characterized in that: The modified siloxane is obtained by a preparation method comprising the following steps: (1) Compound (II) reacts with halopropylene in the presence of base and catalyst I, and after post-treatment, compound (II) is obtained. The structural formula of the compound of formula (II) is: The structural formula of the compound of formula (II) is: Wherein, R3 is H or a C1-C20 alkyl group, preferably H or a C1-C4 alkyl group; m is an integer from 1 to 10, preferably an integer from 1 to 4; n is an integer from 0 to 10, preferably an integer from 0 to 4; (2) The obtained compound of formula (II) was reacted with an organosiloxane in the presence of catalyst II. The modified siloxane was obtained after post-processing.

3. The carbon dioxide enhanced oil recovery agent as described in claim 2, characterized in that: In step (1), The halopropylene is at least one of allyl chloride, allyl bromopropene, and allyl iodopropene; and / or, The base is at least one of inorganic bases and organic bases; and / or, The catalyst I is a phase transfer catalyst, preferably an alkyl halide ammonium salt, more preferably at least one of tetrabutylammonium bromide and tetrabutylammonium iodide; and / or The post-processing includes separation and purification steps.

4. The carbon dioxide enhanced oil recovery agent as described in claim 2, characterized in that: In step (2), The structural formula of the organosiloxane is shown in Formula (IV): Wherein, R1 is a C1-C8 alkyl group, preferably a C1-C4 alkyl group; R2 is H or a C1-C4 alkyl group, preferably H or a C1-C2 alkyl group; and / or, Catalyst II is a noble metal catalyst, preferably a platinum catalyst, and more preferably chloroplatinic acid; and / or The second post-processing step includes separation and purification steps.

5. The carbon dioxide enhanced oil recovery agent as described in claim 2, characterized in that: In step (1), The reaction is carried out under a protective gas atmosphere, wherein the protective gas is at least one selected from nitrogen and an inert gas; and / or, The reaction temperature is 25–120°C, preferably 60–90°C; and / or, The reaction time is 2–24 h, preferably 4–8 h; and / or, The molar ratio of compound (II), halopropylene, base, and catalyst I is 1:(1-5):(1-10):(0.01-0.1), preferably 1:(1-2):(2-5):(0.05-0.1), and more preferably 1:(1.5-2):(4-5):(0.05-0.1).

6. The carbon dioxide enhanced oil recovery agent as described in claim 2, characterized in that: In step (2), First, the solution of compound (II) and catalyst II is mixed and activated by heating, and then an organosiloxane is added; preferably, the activation temperature is 50-70°C and the activation time is 20-40 min; and / or, the solvent in the solution of catalyst II is at least one selected from methanol, isopropanol, isobutanol, toluene, and benzene; and / or, The reaction is carried out under a protective gas atmosphere, wherein the protective gas is at least one selected from nitrogen and an inert gas; and / or, The reaction temperature is 25–150°C, preferably 80–120°C; and / or, The reaction time is 2–24 h, preferably 6–12 h; and / or, The molar ratio of compound (II) of formula, organosiloxane, and catalyst II is 1:(1-2):(0.0005-0.05), preferably 1:(1-2):(0.0005-0.01), and more preferably 1:(1.5-2):(0.0005-0.001).

7. The carbon dioxide enhanced oil recovery agent as described in claim 1, characterized in that: The ester is composed of one or more of formulas (IV) to (VII); Among them, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 Each is independently selected from straight-chain or branched alkanes from C1 to C8; Preferably, the ester is at least one selected from methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, sec-butyl acetate, tert-butyl acetate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dimethyl oxalate, diethyl oxalate, dipropyl oxalate, methyl ethyl oxalate, dibutyl oxalate, dimethyl malonate, diethyl malonate, dipropyl malonate, dibutyl malonate, dimethyl succinate, diethyl succinate, dipropyl succinate, and dibutyl succinate.

8. The carbon dioxide enhanced oil recovery agent as described in claim 1, characterized in that: The alkyl amine is at least one of the following amines with a total carbon number between 4 and 30: primary amine, secondary amine, tertiary amine; preferably at least one of the following straight-chain or branched amines with a total carbon number between 4 and 16: primary amine, secondary amine, tertiary amine; more preferably at least one of the following straight-chain or branched amines with a total carbon number between 4 and 14: primary amine, secondary amine; and / or, The solvent is at least one of C5-C20 straight-chain alkanes, toluene, xylene, and petroleum ether; preferably one or two, more preferably one or two of C5-C16 straight-chain alkanes, toluene, and petroleum ether.

9. A method for preparing a carbon dioxide enhanced oil recovery (EOR) additive as described in any one of claims 1 to 8, comprising the following steps: The carbon dioxide oil recovery additive is obtained by uniformly mixing the components, including modified siloxane, ester, hydrocarbon amine, and optional solvent, according to the stated weight proportions.

10. The application of a carbon dioxide enhanced oil recovery agent as described in any one of claims 1 to 8 in carbon dioxide flooding; preferably, The carbon dioxide oil recovery additive is injected together with carbon dioxide or dissolved in carbon dioxide before injection, and the injection amount of the carbon dioxide oil recovery additive is 0.01 to 5 wt% of carbon dioxide.

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