A compound corrosion inhibitor for CO2 flooding produced fluid and its preparation method

Abstract

This invention discloses a compound corrosion inhibitor for CO2 flooded oil recovery fluid and its preparation method, comprising the following steps: Oleic acid and a catalyst are weighed and added to a reaction vessel; the temperature is raised in stages using a programmable electric heating mantle; a water-carrying agent is added dropwise at 80-100℃, and diethylenetriamine or triethylenetetramine is added dropwise at 110-130℃, controlling the reaction temperature and time; after water separation, the reaction is further carried out at 200-230℃; subsequently, the system is cooled to 60-70℃, and a quaternizing reagent is added to react, respectively preparing corrosion inhibitor E and corrosion inhibitor S; finally, corrosion inhibitor E and corrosion inhibitor S are compounded in a certain proportion to obtain the compound corrosion inhibitor for CO2 flooded oil recovery fluid. This preparation method is simple and easy to implement, reducing costs; when the prepared corrosion inhibitor is applied to CO2 flooded oil recovery fluid corrosion inhibition, it exhibits excellent corrosion inhibition effect, greatly reducing corrosion hazards in CO2 flooded oil recovery applications.

Description

Technical Field

[0001] This invention belongs to the field of corrosion inhibitor processing technology, specifically relating to a compound corrosion inhibitor for CO2 flooding produced fluid and its preparation method. Background Technology

[0002] CO2 enhanced oil recovery (EOR) technology encompasses reservoir engineering design, CO2 injection and production processes, dynamic monitoring and adjustment, and produced fluid treatment in oilfield development. It is considered one of the most promising methods for improving the recovery rate of low-permeability reservoirs. This technology not only reduces carbon dioxide emissions from industrial waste gases that severely impact the environment but also transforms carbon dioxide into an important resource for improving oilfield development and increasing crude oil recovery. However, the miscibility of CO2 with formation water can lead to corrosion of pipelines and mechanical equipment. CO2 dissolves in water to form carbonic acid, which has a strong corrosive effect on metals, especially in the presence of corrosive media such as H2O, HCl, organic acids, and H2S.

[0003] Current corrosion prevention measures include selecting corrosion-resistant alloy materials, applying cathodic protection, surface treatment of pipeline steel, and adding corrosion inhibitors. Among these measures, adding chemical corrosion inhibitors is an economical, effective, and versatile method for controlling corrosion and scaling, particularly suitable for use in oil and gas wells and gathering and transportation systems. Corrosion inhibitors typically contain heteroatoms such as N, O, and S, or heterocycles such as imidazoline and quinoline, exhibiting excellent corrosion inhibition effects. Imidazoline corrosion inhibitors are currently the most widely used commercial CO2 corrosion inhibitors, possessing good thermal stability and low toxicity, making them suitable for corrosive environments with high CO2 content; however, their corrosion inhibition effect is not ideal. Summary of the Invention

[0004] The purpose of this invention is to provide a compound corrosion inhibitor for CO2 flooding produced fluid and its preparation method. The preparation method is simple and easy to implement, and can reduce costs. When the prepared corrosion inhibitor is applied to CO2 flooding produced fluid, it can show excellent corrosion inhibition effect and greatly reduce the corrosion hazards in CO2 flooding applications.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] A method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid includes the following steps:

[0007] (1) Preparation of corrosion inhibitor E;

[0008] (1-1) Weigh a certain amount of oleic acid and catalyst and add them to the reaction vessel;

[0009] (1-2) A programmable electric heating mantle is used for heating. The first program is set to heat up for 1-2 hours, with the starting temperature set to 90℃ and the ending temperature set to 150℃; the second program is set to heat up for 3-4 hours, with the starting temperature set to 150℃ and the ending temperature set to 170℃; the third program is set to heat up for 1-1.5 hours, with the starting temperature set to 170℃ and the ending temperature set to 220℃; and the fourth program is set to maintain the temperature for 3-4 hours, with the starting temperature set to 220℃ and the ending temperature set to 220℃.

[0010] (1-3) When the electric heating mantle reaches 80-100℃, add the water-carrying agent dropwise into the reaction vessel;

[0011] (1-4) When the heating mantle is heated to 110-130℃, diethylenetriamine is added dropwise. After the addition is complete, the water in the reaction system is separated, and then the reaction is carried out at 200-230℃ for 3-4 hours.

[0012] (1-5) Stop heating, wait for the temperature in the reaction system to drop to 60-70℃, add the quaternizing agent, and react at this temperature for 3-4 hours to obtain corrosion inhibitor E;

[0013] (2) Preparation of corrosion inhibitor S;

[0014] (2-1) Weigh a certain amount of oleic acid and catalyst and add them to the reaction vessel;

[0015] (2-2) A programmable electric heating mantle is used for heating. The first program is set to heat up for 1-2 hours, with the starting temperature set to 90℃ and the ending temperature set to 150℃; the second program is set to heat up for 3-4 hours, with the starting temperature set to 150℃ and the ending temperature set to 170℃; the third program is set to heat up for 1-1.5 hours, with the starting temperature set to 170℃ and the ending temperature set to 220℃; and the fourth program is set to heat up for 4-5 hours, with the starting temperature set to 220℃ and the ending temperature set to 220℃.

[0016] (2-3) When the electric heating mantle reaches 80-100℃, add the water-carrying agent dropwise into the reaction vessel;

[0017] (2-4) When the heating mantle is heated to 110-130℃, add triethylenetetramine dropwise. After the addition is complete, remove the water from the reaction system and then react at 200-230℃ for 4-5 hours.

[0018] (2-5) Stop heating, wait for the temperature in the reaction system to drop to 60-70℃, add the quaternizing agent, and react at this temperature for 4-5 hours to obtain corrosion inhibitor S;

[0019] (3) The corrosion inhibitor E prepared in step (1) is compounded with the corrosion inhibitor S prepared in step (2) to obtain a corrosion inhibitor for CO2 flooding produced fluid.

[0020] Preferably, in steps (1-1) and (2-1), the catalyst is boric acid, and the amount of catalyst used is 0.1-0.3 wt% of oleic acid.

[0021] Preferably, in steps (1-3) and (2-3), the water-carrying agent is xylene or toluene, and the amount of water-carrying agent added is 20%-30% of the total mass of oleic acid, catalyst and water-carrying agent.

[0022] Preferably, in steps (1-4), the molar ratio between diethylenetriamine and oleic acid is (1.1-1.2):1.

[0023] Preferably, in steps (2-4), the molar ratio between triethylenetetramine and oleic acid is 1:(1.8-2.0).

[0024] Preferably, in steps (1-5), the quaternizing agent is one of diethyl carbonate, dioctyl carbonate, benzyl chloride, dimethyl sulfate, and diethyl sulfate, and the molar ratio between the quaternizing agent and oleic acid is (0.9-1):1.

[0025] Preferably, in steps (2-5), the quaternizing agent is one of diethyl carbonate, dioctyl carbonate, benzyl chloride, dimethyl sulfate, and diethyl sulfate, and the molar ratio between the quaternizing agent and oleic acid is 1:(1.0-2.0).

[0026] Preferably, in step (3), the mass ratio between the corrosion inhibitor E prepared in step (1) and the corrosion inhibitor S prepared in step (2) is 1:(1-3).

[0027] To achieve the above-mentioned objectives, the present invention also provides a compound corrosion inhibitor for CO2 flooding produced fluid prepared by the above-mentioned preparation method.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The preparation process of this invention is simple and easy to implement, and the cost is low;

[0030] (2) The corrosion inhibitor prepared by the present invention has excellent corrosion inhibition effect. When applied to CO2 flooding produced fluid corrosion inhibition, it shows excellent corrosion inhibition effect with a corrosion inhibition rate of 91.21%. The corrosion rate after adding the corrosion inhibitor is 0.0149 mm / a, which is far lower than the industry standard of 0.076 mm / a. This greatly reduces the corrosion hazards in CO2 flooding applications and has broad economic and social benefits.

[0031] (3) The synthesis process of this invention is green and low in toxicity. The water-carrying agent can be recycled. The quaternization reagent used is low in toxicity, harmless and odorless. The resulting corrosion inhibitor has no special odor. Attached Figure Description

[0032] Figure 1 A diagram of the synthesis apparatus for preparing the corrosion inhibitor according to the present invention;

[0033] Figure 2 This is a diagram of the experimental setup for simulating actual CO2-driven oil transport according to the present invention;

[0034] Figure 3 This is a diagram of the electrochemical testing device of the Chenhua CHI 660E series electrochemical workstation of the present invention;

[0035] Figure 4 This is a graph showing the corrosion rate and corrosion inhibition rate in the weight loss method experiment involved in the embodiments of the present invention;

[0036] Figure 5 This is a Tafel polarization curve diagram involved in the embodiments of the present invention;

[0037] Figure 6 The Nyquist plot of the EIS test involved in the embodiments of the present invention;

[0038] Figure 7 This is the equivalent circuit diagram for Zsimpwin fitting involved in the embodiments of the present invention. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments.

[0040] Example

[0041] like Figure 1 As shown, a method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid includes the following steps:

[0042] (1) Preparation of corrosion inhibitor E;

[0043] (1-1) Weigh 28g of oleic acid (0.1mol) and 0.06g of boric acid and add them to a 250ml three-necked flask;

[0044] (1-2) Edit the programmable electric heating mantle, set the first program, the program heats up for 1-2 hours, the starting temperature is set to 90℃ and the ending temperature is set to 150℃, set the second program, the program heats up for 3-4 hours, the starting temperature is set to 150℃ and the ending temperature is set to 170℃, set the third program, the program heats up for 1-1.5 hours, the starting temperature is set to 170℃ and the ending temperature is set to 220℃, set the fourth program, the program holds the temperature for 3-4 hours, the starting temperature is set to 220℃ and the ending temperature is set to 220℃;

[0045] (1-3) When the electric heating mantle is heated to 90°C, add 10 ml of xylene to the three-necked flask using a constant pressure dropping funnel;

[0046] (1-4) When the electric heating mantle is heated to 120℃, 13ml (0.12mol) of diethylenetriamine is added dropwise using a constant pressure dropping funnel. After the constant pressure dropping funnel has finished adding the solution, a water separator is installed to continuously separate the water in the reaction system. Then the reaction is carried out at 220℃ for 3 hours.

[0047] (1-5) Stop heating and wait for the temperature in the reaction system to drop to 60℃. Add 12ml of diethyl carbonate (0.1mol) and react at this temperature for 3h to obtain corrosion inhibitor E;

[0048] (2) Preparation of corrosion inhibitor S;

[0049] (2-1) Weigh 53g of oleic acid (0.19mol) and 0.1g of boric acid and add them to a 250ml three-necked flask;

[0050] (2-2) Edit the programmable electric heating mantle, set the first program, the program heats up for 1-2 hours, the starting temperature is set to 90℃ and the ending temperature is set to 150℃; set the second program, the program heats up for 3-4 hours, the starting temperature is set to 150℃ and the ending temperature is set to 170℃; set the third program, the program heats up for 1-1.5 hours, the starting temperature is set to 170℃ and the ending temperature is set to 220℃; set the fourth program, the program heats up for 4-5 hours, the starting temperature is set to 220℃ and the ending temperature is set to 220℃.

[0051] (2-3) When the electric heating mantle reaches 90°C, add 20 ml of xylene to the three-necked flask using a constant pressure dropping funnel;

[0052] (2-4) When the electric heating mantle is heated to 120℃, 15ml (0.1mol) of triethylenetetramine is added dropwise using a constant pressure dropping funnel. After the constant pressure dropping funnel is finished, a water separator is installed to continuously separate the water in the reaction system. Then the reaction is carried out at 220℃ for 4h.

[0053] (2-5) Stop heating and wait for the temperature in the reaction system to drop to 60℃. Add 60ml of dioctyl carbonate (0.19mol) and react at this temperature for 4h to obtain corrosion inhibitor S;

[0054] (3) Take out 1g of corrosion inhibitor E prepared in step (1) and 2g of corrosion inhibitor S prepared in step (2) and put them into a small beaker, sonicate and stir for 3 minutes to obtain corrosion inhibitor T, i.e. corrosion inhibitor for CO2 flooding produced fluid.

[0055] like Figure 2As shown, corrosion inhibitors E, S, and T obtained in the above steps were added to an experimental device simulating actual CO2-driven oil transport for dynamic strip weight loss experiments (the strip weight loss experiment was conducted in a 0.54 MPa CO2 gas environment and at 35°C in 80% water content crude oil produced fluid using the full immersion strip weight loss method; the strips were HG5-1526-1983 standard type III 40*13*2mm carbon steel with a surface area of ​​12 cm²). 2 Meanwhile, a commonly used commercial corrosion inhibitor, Quaternary Ammonium Salt 27 (Oleic Imidazoline Methyl Sulfate Ammonium) (99%) (hereinafter referred to as Corrosion Inhibitor J), was subjected to the same weight loss method experiment to compare its corrosion inhibition performance.

[0056] Furthermore, the corrosive solution after the weight loss method experiment was subjected to polarization curve testing and EIS testing using a Chenhua CHI 660E series electrochemical workstation with a standard three-electrode electrolytic cell. A platinum wire electrode (Shanghai Chenhua, model CHI115) was used as the auxiliary electrode, an Ag / AgCl electrode (Shanghai Chenhua, model CHI111) as the reference electrode, and a carbon steel electrode (Shanghai Leton, model 3mm) as the working electrode. Figure 3 As shown.

[0057] Blank experiment: Perform the same weight loss experiment using the above apparatus without adding any reagents.

[0058] Specific implementation:

[0059] The weight loss method calculates the corrosion rate by measuring the change in mass of the specimen before and after the corrosion process over a certain period. The rate of corrosion is used to determine the corrosion inhibition effect of the corrosion inhibitor on the metal in that environment. If both the metal and corrosion products dissolve into the corrosive medium, resulting in a decrease in the weight of the specimen after corrosion, the weight loss method is generally used. When the corrosion products have a clear composition and adhere firmly to the metal surface, resulting in an increase in the weight of the specimen after corrosion, the weight gain method is used. Because the weight loss method has many advantages, such as simple operation, intuitive results, and high reliability, it is currently considered the most basic method for evaluating the performance of corrosion inhibitors.

[0060] Metal corrosion is an electrochemical reaction and possesses electrochemical properties; therefore, electrochemical studies can indirectly measure the corrosion rate of metals. Commonly used electrochemical methods include the Tafel extrapolation method based on potentiodynamic polarization curves and the electrochemical impedance spectroscopy (EIS).

[0061] 1. Tafel extrapolation method for potentiodynamic polarization curves

[0062] The self-corrosion potential and self-corrosion current can be found in the potentiodynamic polarization curve. Changes in the self-corrosion current provide clear indications of changes in the corrosion rate. Generally, the smaller the self-corrosion current, the lower the corrosion rate of the metal, and the better the effect of the corrosion inhibitor. Simultaneously, it is necessary to study the changes in the self-corrosion potential to determine the mechanism of action of the corrosion inhibitor.

[0063] 2. AC impedance method

[0064] Electrochemical impedance spectroscopy (EIS) involves converting an AC signal into a small-amplitude sine wave and using the changes in this wave to affect the electrode. After stabilization, the system's response is observed, thus measuring the impedance value of the corrosion system. Different impedance measurement methods yield different curves, such as the Nyquist plot. Using Zsimpwin 3.10 software to design an equivalent circuit and analyze the Nyquist plot, the corresponding equivalent circuit is determined. Based on this equivalent circuit model, the corrosion inhibition effect can be inferred.

[0065] Procedure for the weightlessness experiment:

[0066] (1) Select type III 40*13*2mm with a surface area of ​​12cm², conforming to HG5-1526-1983 standard. 2 Carbon steel (purchasing professional corrosion-resistant pads eliminates the need for special treatments such as degreasing) was used as the experimental pads. The pads were soaked and washed three times in anhydrous ethanol, then dried with degreased cotton, dried with cold air, weighed, and recorded for future use.

[0067] (2) Weigh 20g of crude oil and 80g of oil recovery fluid, heat and dissolve to prepare corrosion solution, prepare 4 groups. No reagents are added to the first group, 0.1g of quaternary ammonium salt-27 (99%) (hereinafter referred to as corrosion inhibitor J) is added to the second group, 0.1g of corrosion inhibitor E is added to the third group, 0.1g of corrosion inhibitor S is added to the fourth group, and 0.1g of corrosion inhibitor T is added to the fifth group.

[0068] (3) Add the corrosive liquid to the Shanghai Yanzheng reactor (Micro-Reactor reactor, YZPR-100(M)), set the temperature to 35℃, the rotation speed to 200RPM, the reaction time to 168h, and introduce 0.54Mpa CO2. Add CO2 every 24h to keep the pressure inside the reactor at 0.54Mpa.

[0069] (4) Take 100ml of 15% hydrochloric acid, add 5g of hexamethylenetetramine, and add water to 1000ml to prepare pickling solution.

[0070] (5) After the reaction is complete, remove the plate, wash away the crude oil on the surface with heavy oil cleaning agent (professional cleaning agent purchased online: surface activator), wash away the corrosion products with acid washing solution, rinse the sample with clean water, soak and wash three times in acetone and anhydrous ethanol, wipe dry with degreased cotton, blow dry with cold air, weigh and record for future use.

[0071] The data processing method is as follows:

[0072]

[0073] Where: V—corrosion rate, mm / a;

[0074] m0 — Mass of the coupon before corrosion, in grams;

[0075] m — the mass of the corroded plate, in grams;

[0076] s — Total surface area of ​​the hanging plate, cm² 2 ;

[0077] t — corrosion time of the plate, in hours;

[0078] ρ—Density of the specimen; for carbon steel, it is generally taken as 7.85 g / cm³. 3 ;

[0079]

[0080] In the formula: η—corrosion inhibition rate, %

[0081] V0 — Average corrosion rate of the blank corrosion solution, mm / a;

[0082] V i —The average corrosion rate in the corrosion solution after the addition of corrosion inhibitor, mm / a;

[0083] Results of the weightlessness experiment are as follows Figure 4 As shown.

[0084] As shown in the figure, the corrosion inhibition effect is T > S > J > E. The corrosion inhibition rate of T is as high as 91.21%. After adding T, the corrosion rate is 0.0149 mm / a, which is lower than the industry standard of 0.076 mm / a.

[0085] Electrochemical testing:

[0086] The corrosive solution after the weight loss method experiment was subjected to polarization curve testing and EIS testing using a Chenhua CHI 660E series electrochemical workstation with a standard three-electrode electrolytic cell. A platinum wire electrode (Shanghai Chenhua, model CHI115) was used as the auxiliary electrode, an Ag / Agcl electrode (Shanghai Chenhua, model CHI111) was used as the reference electrode, and a carbon steel electrode (Shanghai Leton, model 3mm) was used as the working electrode. The potential range for measuring the potentiodynamic polarization curve was set to -700mV to +100mV relative to the self-corrosion potential, and the potential scan rate for the polarization curve test was 0.5mV / s. The EIS measurement was performed under OCP, with an experimental test frequency range of 1000KHz-10mHz and an excitation signal of ±10mV AC amplitude. The corrosion rate V was obtained by extrapolation of the polarization curve test, and the corrosion inhibition rate was obtained by formula (2). The EIS test used Zsimpwin 3.10 software to fit the electrochemical measurement system to a corresponding equivalent circuit that is easy to analyze. The corrosion inhibition rate was obtained by the following formula (3):

[0087]

[0088] Where: η—corrosion inhibition rate, %;

[0089] R ct —Electrochemical impedance value in the corrosion solution after adding corrosion inhibitor, Ω·cm 2 ;

[0090] R ct0 —Electrochemical impedance spectroscopy of the system with blank sample, in Ω·cm 2 ;

[0091] Equivalent circuit diagram as follows Figure 7 As shown, Figure 7 middle:

[0092] RL – Ohmic resistance of the solution;

[0093] W1—Permeation and diffusion resistance of crude oil molecules;

[0094] CPE—Constant Phase Angle Element;

[0095] CPE1—Capacitance of film adsorbed by particles such as corrosion inhibitors and corrosion products;

[0096] Rf—Resistance of the film adsorbed by particles such as corrosion inhibitors and corrosion products;

[0097] CPE2 — Electric double-layer capacitor;

[0098] Rct – Ohmic resistance for charge transfer.

[0099] Polarization curve test data table:

[0100]

[0101] The Tafel polarization curve obtained from the test is shown below. Figure 5 As shown.

[0102] Based on the data above, after adding corrosion inhibitors E, J, S, and T, E... corr Increasing the corrosion potential shifts positively. All corrosion inhibitors are cationic. The corrosion inhibition effect is: Inhibitor T > Inhibitor S > Inhibitor J > Inhibitor E.

[0103] EIS Test Data Sheet:

[0104]

[0105] The Nyquist plot obtained from the EIS test is shown below. Figure 6 As shown.

[0106] Based on the data above, after adding corrosion inhibitors E, J, S, and T, R... ct All values ​​increased compared to the control group, for R ct Corrosion inhibitor T > Corrosion inhibitor S > Corrosion inhibitor J > Corrosion inhibitor E, Corrosion inhibition effect: Corrosion inhibitor T > Corrosion inhibitor S > Corrosion inhibitor J > Corrosion inhibitor E.

[0107] In summary, the corrosion inhibitor T prepared in this invention has excellent corrosion inhibition effect. When applied to CO2 flooding produced fluid corrosion inhibition, it exhibits excellent corrosion inhibition effect with a corrosion inhibition rate as high as 91.21%. After adding corrosion inhibitor T, the corrosion rate is 0.0149 mm / a, which is lower than the industry standard of 0.076 mm / a. This greatly reduces the corrosion hazards in CO2 flooding applications and has significant economic and social benefits.

Claims

1. A method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid, characterized in that, Includes the following steps: (1) Preparation of corrosion inhibitor E; (1-1) Weigh oleic acid and catalyst and add them to the reaction vessel; the catalyst is boric acid, and the amount of catalyst is 0.1-0.3 wt% of oleic acid; (1-2) A programmable electric heating mantle is used for heating. The first program is set to heat up for 1-2 hours, with the starting temperature set to 90℃ and the ending temperature set to 150℃; the second program is set to heat up for 3-4 hours, with the starting temperature set to 150℃ and the ending temperature set to 170℃; the third program is set to heat up for 1-1.5 hours, with the starting temperature set to 170℃ and the ending temperature set to 220℃; and the fourth program is set to maintain the temperature for 3-4 hours, with the starting temperature set to 220℃ and the ending temperature set to 220℃. (1-3) When the electric heating mantle is heated to 80-100℃, add the water-carrying agent dropwise into the reaction vessel; (1-4) When the heating mantle is heated to 110-130℃, diethylenetriamine is added dropwise. After the addition is complete, the water in the reaction system is separated, and then the reaction is carried out at 200-230℃ for 3-4 hours. (1-5) Stop heating, wait for the temperature in the reaction system to drop to 60-70℃, add the quaternizing agent, and react at this temperature for 3-4 hours to obtain corrosion inhibitor E; (2) Preparation of corrosion inhibitor S; (2-1) Weigh oleic acid and catalyst and add them to the reaction vessel; the catalyst is boric acid, and the amount of catalyst is 0.1-0.3 wt% of oleic acid; (2-2) A programmable electric heating mantle is used for heating. The first program is set to heat up for 1-2 hours, with the starting temperature set to 90℃ and the ending temperature set to 150℃; the second program is set to heat up for 3-4 hours, with the starting temperature set to 150℃ and the ending temperature set to 170℃; the third program is set to heat up for 1-1.5 hours, with the starting temperature set to 170℃ and the ending temperature set to 220℃; and the fourth program is set to maintain the temperature for 4-5 hours, with the starting temperature set to 220℃ and the ending temperature set to 220℃. (2-3) When the electric heating mantle reaches 80-100℃, add the water-carrying agent dropwise into the reaction vessel; (2-4) When the heating mantle is heated to 110-130℃, triethylenetetramine is added dropwise. After the addition is complete, the water in the reaction system is removed, and then the reaction is carried out at 200-230℃ for 4-5 hours. (2-5) Stop heating, wait for the temperature in the reaction system to drop to 60-70℃, add the quaternizing agent, and react at this temperature for 4-5 hours to obtain corrosion inhibitor S; (3) The corrosion inhibitor E prepared in step (1) is combined with the corrosion inhibitor S prepared in step (2) to obtain a corrosion inhibitor for CO2 flooding produced fluid.

2. The method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid according to claim 1, characterized in that, In steps (1-3) and (2-3), the water-carrying agent is xylene or toluene, and the amount of water-carrying agent added is 20%-30% of the total mass of oleic acid, catalyst and water-carrying agent.

3. The method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid according to claim 1, characterized in that, In steps (1-4), the molar ratio between diethylenetriamine and oleic acid is (1.1-1.2):

1.

4. The method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid according to claim 1, characterized in that, In steps (2-4), the molar ratio between triethylenetetramine and oleic acid is 1:(1.8-2.0).

5. The method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid according to claim 1, characterized in that, In steps (1-5), the quaternizing agent is one of diethyl carbonate, dioctyl carbonate, benzyl chloride, dimethyl sulfate, or diethyl sulfate, and the molar ratio between the quaternizing agent and oleic acid is (0.9-1):

1.

6. The method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid according to claim 1, characterized in that, In steps (2-5), the quaternizing agent is one of diethyl carbonate, dioctyl carbonate, benzyl chloride, dimethyl sulfate, or diethyl sulfate, and the molar ratio between the quaternizing agent and oleic acid is 1:(1.0-2.0).

7. The method for preparing a compound corrosion inhibitor for CO2 flooding produced fluid according to claim 1, characterized in that, In step (3), the mass ratio between the corrosion inhibitor E prepared in step (1) and the corrosion inhibitor S prepared in step (2) is 1:(1-3).

8. A compound corrosion inhibitor for CO2 flooding produced fluid prepared by any one of the preparation methods described in claims 1-7.

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