A carbon dioxide flooding casing protection fluid and its preparation method and application

Abstract

The present invention belongs to the field of casing protection fluids for oil fields and discloses a carbon dioxide flooding casing protection fluid, its preparation method, and its application. The casing protection fluid is prepared by mixing the following raw materials: Agent A: 5-10 parts polyoxyethylene rosin amine, 5-15 parts rosin imidazoline, 5-10 parts oleic acid imidazoline, 10-15 parts amide imidazoline, 8-10 parts bisimidazoline corrosion inhibitor, 8-10 parts pulp waste liquid, and 30-59 parts water; and Casing Protection Fluid: 4-8 parts Agent A, 0.5-1.5 parts glycerol polyoxypropylene polyoxyethylene ether, 20-30 parts ethylene glycol, and 60.5-75.5 parts water. This fluid can significantly reduce the corrosion rate of carbon dioxide injection wells and reduces the cost by over 60% compared to oil-based casing protection fluids.

Description

Technical Field

[0001] The invention belongs to the field of casing protection fluids in oil fields, and relates to a carbon dioxide flooding casing protection fluid, a preparation method and an application thereof. Background Art

[0002] The application of CO2 injection and production technology, and the subsequent expansion of CCUS applications, presents several technical challenges that urgently need to be addressed. CO2, in humid underground environments and particularly at high temperatures, can cause severe corrosion to the casing of injection and production wells. This corrosion can lead to leaks and damage, severely impacting normal production. For corrosion protection in injection wells, a preferred approach is to inject a casing anti-corrosion fluid into the annulus to provide maximum protection against corrosion.

[0003] Currently, the commonly used casing protection fluid is oil-based casing protection fluid, which is composed of 4%-7% corrosion inhibitor, 1%-5% surfactant and 1%-3% scale inhibitor added to the oil base to form a casing protection fluid system. Since it is an oil-based system, the cost of the protection fluid is relatively high.

[0004] At the same time, in response to the mechanism of casing corrosion, the annular protection fluids used in various oil fields are composed of fungicides, deoxidizers, corrosion and scale inhibitors, density regulators, etc. Among them, corrosion and scale inhibitors have been widely studied and applied. For example, imidazoline derivatives, organophosphates, polycarboxylic acids and other corrosion and scale inhibitors are more commonly used. Density regulators can be divided into inorganic salt type and organic salt type. Although annular protection fluids using the above technologies can improve the water quality of the annular space and reduce the corrosiveness of annular water, the effect is not ideal in oil and gas wells that inject corrosive CO2 gas. Especially in high-pressure injection gas wells, leakage from the packer gap into the annular protection fluid can easily turn the protection fluid into an acidic liquid, accelerating the corrosion of the oil pipe and casing, causing serious damage to the casing and production tubing, and resulting in huge economic losses. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a carbon dioxide flooding casing protection fluid and its preparation method and application, which can greatly reduce the corrosion rate of carbon dioxide injection wells and reduce the cost by more than 60% compared with oil-based casing protection fluid.

[0006] The purpose of the present invention is to provide a carbon dioxide flooding casing protection fluid, which can not only effectively solve the problem of casing corrosion in CO2 flooding injection wells, but also achieve the purpose of low-cost corrosion prevention.

[0007] Another object of the present invention is to provide a method for preparing the casing protection liquid.

[0008] The present invention also aims to provide an application of carbon dioxide flooding casing protection fluid.

[0009] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0010] A carbon dioxide flooding casing protection fluid, wherein the mass ratio of each raw material component of the casing protection fluid is:

[0011]

[0012] The mass ratio of the raw material components of Agent A is:

[0013]

[0014] The polyoxyethylene rosin amine, rosin imidazoline, oleic acid imidazoline, amide imidazoline, bisimidazoline corrosion inhibitor, pulp waste liquid, glycerol polyoxypropylene polyoxyethylene ether and ethylene glycol are all commercially available industrial products. The pulp waste liquid in the present invention is a by-product of sulfite papermaking wood pulp.

[0015] Any commercially available product meeting the corresponding quality standards can be used in the present invention and achieve the purpose of the present invention.

[0016] According to some specific embodiments of the present invention, the casing protection liquid is prepared by mixing the following raw materials: Agent A: 5-10 parts of polyoxyethylene rosin amine, 5-15 parts of rosin imidazoline, 5-10 parts of oleic acid imidazoline, 10-15 parts of amide imidazoline, 8-10 parts of bisimidazoline corrosion inhibitor, 8-10 parts of pulp waste liquid, and 30-59 parts of water; Casing protection liquid: 4-8 parts of Agent A, 0.5-1.5 parts of glycerol polyoxypropylene polyoxyethylene ether, 20-30 parts of ethylene glycol, and 60.5-75.5 parts of water.

[0017] The casing protection fluid of the present invention has a good corrosion inhibition effect on metals in a carbon dioxide injection environment. In the indoor corrosion rate simulation experiment, the corrosion reaction time was 72h. The corrosion rate was 4.21mm / a before adding the casing protection fluid. After using the casing protection fluid, the corrosion rate was 0.026mm / a. After the casing protection fluid was injected into the field test well, carbon dioxide was injected. The test time was one month. After the test, the corrosion rate was measured to be only 0.002mm / a. It has been proved by indoor experiments and field tests that the casing protection fluid of the above invention has a good effect in preventing carbon dioxide corrosion. At present, more than 30 wells have been implemented on site. With the expansion of carbon flooding and carbon storage, the casing protection fluid has a good application prospect.

[0018] The present invention also provides a method for preparing the above-mentioned casing protection liquid, which comprises:

[0019] (1) Weigh 180 kg to 708 kg of water into a reactor and heat to 40°C while stirring;

[0020] (2) Weigh 30 kg to 120 kg of polyoxyethylene rosin amine into a reactor and stir for 5 minutes;

[0021] (3) Weigh 30 kg to 180 kg of rosin imidazoline into the reactor and stir for 5 minutes;

[0022] (4) Weigh 30 kg to 120 kg of imidazoline oleate into the reactor and stir for 5 minutes;

[0023] (5) Weigh 60 kg to 180 kg of amide imidazoline into the reactor and stir for 5 minutes;

[0024] (6) Weigh 48 kg to 120 kg of bisimidazoline corrosion inhibitor and add it to the reactor, stirring for 20 minutes;

[0025] (7) Weigh 48 kg to 120 kg of pulp waste liquid into the reactor and stir for 20 minutes;

[0026] (8) Stop heating and lower the temperature of the reactor to room temperature to obtain Agent A.

[0027] (9) Weigh 9075 kg - 11325 kg of water in 15m 3 In the mixing tank, add 75 kg - 225 kg of glycerol polyoxypropylene polyoxyethylene ether while stirring and stir for 15 minutes.

[0028] (10) Add 600 kg to 1200 kg of Agent A to the mixing tank, stirring for 15 minutes;

[0029] (11) Add 3000 kg to 4500 kg of ethylene glycol and stir for 20 minutes to obtain the casing protection liquid.

[0030] Preferably, in step (1), the reactor is heated to 40±1°C.

[0031] Preferably, in steps (1)-(7), the stirring speed is 45 rpm.

[0032] Preferably, in steps (9)-(11), the stirring speed is 60 rpm.

[0033] The present invention also provides the use of the aforementioned casing protection fluid in carbon dioxide injection wells. Specifically, the following steps are followed: the casing protection fluid is pumped into the wellbore using a pump truck, injected into the casing through the oil pipe, and then circulated until the returned fluid matches the injected fluid, at which point injection of the casing protection fluid is stopped. A ball-dropping downhole packer is then set, sealing the casing protection fluid within the oil-casing annulus to protect the casing from corrosion.

[0034] The beneficial effects of the present invention compared with the prior art are:

[0035] The present invention provides a CO2 flooding casing protection fluid, its preparation method, and its application. The casing protection fluid can be injected into the casing from the oil pipe and then circulated until the return fluid matches the injected fluid. A ball-dropping downhole packer is then set to seal the casing protection fluid within the oil-casing annulus, effectively and cost-effectively resolving corrosion issues in CO2 flooding injection wells and ensuring normal production. DETAILED DESCRIPTION

[0036] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0037] Example 1

[0038] 15 tons of casing protection fluid was synthesized using the following preparation method:

[0039] (1) Weigh 342 kg of water into a reactor and heat it to 40°C while stirring;

[0040] (2) Weigh 30 kg of polyoxyethylene rosin amine and add it to the reactor, stirring for 5 minutes;

[0041] (3) Weigh 30 kg of rosin imidazoline and add it to the reactor, stirring for 5 minutes;

[0042] (4) Weigh 30 kg of imidazoline oleate and add it to the reactor, stirring for 5 minutes;

[0043] (5) Weigh 60 kg of amide imidazoline into the reactor and stir for 5 minutes;

[0044] (6) Weigh 48 kg of bisimidazoline corrosion inhibitor and add it to the reactor, stirring for 20 minutes;

[0045] (7) Weigh 60 kg of pulp waste liquid into the reactor and stir for 20 minutes;

[0046] (8) Stop heating and lower the temperature of the reactor to room temperature to obtain Agent A.

[0047] (9) Weigh 11325 kg of water in 15m 3 In the mixing tank, add 75 kg of glycerol polyoxypropylene polyoxyethylene ether while stirring and stir for 15 minutes.

[0048] (10) Add 600 kg of Agent A to the mixing tank while stirring for 15 minutes;

[0049] (11) Add 3000 kg of ethylene glycol and stir for 20 minutes to obtain the casing protection liquid.

[0050] In step (1), the reactor temperature is raised to 40±1°C;

[0051] In steps (1)-(7), the stirring speed is 45 rpm.

[0052] In steps (9)-(11), the stirring speed is 60 rpm.

[0053] Evaluation of the effect of the casing protection liquid prepared in Example 1:

[0054] Indoor evaluation experimental steps:

[0055] Before the experiment, wipe the corrosion coupons with filter paper, then place them in a container filled with petroleum ether or acetone with a boiling range of 60℃-90℃, remove the grease on the surface of the coupons with absorbent cotton, and then soak them in anhydrous ethanol for about 5 minutes for further degreasing and dehydration. After taking out the coupons, place them on filter paper, blow dry with cold air, and then wrap them with filter paper. Store them in a desiccator and measure the size and weigh them after leaving them for 1 hour, with an accuracy of 0.1mg.

[0056] Based on the reactor volume, simulated water was placed in the reactor. Nitrogen was first passed through the simulated water for 0.5 hours to remove oxygen from the simulated water. The treated N80 corrosion coupon was then added. The reactor lid was sealed, and the CO2 pressure required for the experiment was set according to the actual site conditions. The reactor was then kept at the actual site temperature for a static corrosion evaluation experiment lasting 72 hours. Three parallel experiments were performed for each group of experiments, and the average value of the parallel experiments was taken as the measurement result.

[0057] Remove the coupons that have completed the test cycle. Observe and record the surface corrosion status and corrosion product adhesion. Immediately rinse the test medium with clean water and dry the coupons with filter paper. Place the coupons in a container containing petroleum ether or acetone with a boiling range of 60°C-90°C. Gently wipe with absorbent cotton. Then soak in anhydrous ethanol for 5 minutes for further degreasing and dehydration. Remove the coupons and soak them in an acid cleaning solution prepared according to Appendix A of SY / T5273-2000 for 5 minutes. Simultaneously, use tweezers to gently wipe the corrosion products on the coupon surface. Remove the coupons from the cleaning solution, rinse with tap water to remove any residual acid on the surface, and immediately immerse them in a sodium hydroxide solution (60g / L). After 30 seconds, rinse with tap water, and then soak in anhydrous ethanol for approximately 5 minutes, washing and dehydrating twice. Take out the hanging piece and place it on filter paper, blow it dry with cold air, then wrap the hanging piece with filter paper, store it in a desiccator, and weigh it after leaving it for 1 hour, with an accuracy of 0.1 mg.

[0058] Indoor evaluation test results:

[0059] The corrosion rate is calculated as follows:

[0060]

[0061] Where: r corr ——Uniform corrosion rate, mm / a; m——Mass of coupon before test, g; m t ——The mass of the coupon after the test, g; S1——The total area of ​​the coupon, cm 2 ;ρ——density of the coupon material, g / cm 3 ; t——test time, h.

[0062] The specific experimental results are shown in Table 1:

[0063] Table 1. Anticorrosion performance evaluation table

[0064] Evaluation Project Evaluation results Corrosion rate (blank) 4.212mm / a Corrosion rate (casing protection fluid) 0.035mm / a

[0065] On-site evaluation:

[0066] Coupons with a one-month corrosion cycle were retrieved from the well. The post-field corrosion treatment and corrosion rate calculation procedures were the same as those used in the laboratory experiment. After the casing protection fluid was injected into the field test well, the corrosion rate of the corrosion coupons was measured to be only 0.002 mm / a.

[0067] Example 2:

[0068] 15 tons of casing protection fluid was synthesized using the following preparation method:

[0069] (1) Weigh 360 kg of water into a reactor and heat it to 40°C while stirring;

[0070] (2) Weigh 120 kg of polyoxyethylene rosin amine and add it to the reactor, stirring for 5 minutes;

[0071] (3) Weigh 180 kg of rosin imidazoline into the reactor and stir for 5 minutes;

[0072] (4) Weigh 120 kg of imidazoline oleate and add it to the reactor, stirring for 5 minutes;

[0073] (5) Weigh 180 kg of amide imidazoline into the reactor and stir for 5 minutes;

[0074] (6) Weigh 120 kg of bisimidazoline corrosion inhibitor and add it to the reactor, stirring for 20 minutes;

[0075] (7) Weigh 120 kg of pulp waste liquid into the reactor and stir for 20 minutes;

[0076] (8) Stop heating and lower the temperature of the reactor to room temperature to obtain Agent A.

[0077] (9) Weigh 9075 kg of water in 15m 3 In the mixing tank, add 225 kg of glycerol polyoxypropylene polyoxyethylene ether while stirring and stir for 15 minutes.

[0078] (10) Add 1200 kg of Agent A to the mixing tank while stirring for 15 minutes;

[0079] (11) Add 4500 kg of ethylene glycol and stir for 20 minutes to obtain the casing protection liquid.

[0080] In step (1), the reactor temperature is raised to 40±1°C;

[0081] In steps (1)-(7), the stirring speed is 45 rpm.

[0082] In steps (9)-(11), the stirring speed is 60 rpm.

[0083] Evaluation of the effect of the casing protection liquid prepared in Example 2:

[0084] Indoor evaluation experimental steps:

[0085] Before the experiment, wipe the corrosion coupons with filter paper, then place them in a container filled with petroleum ether or acetone with a boiling range of 60℃-90℃, remove the grease on the surface of the coupons with absorbent cotton, and then soak them in anhydrous ethanol for about 5 minutes for further degreasing and dehydration. After taking out the coupons, place them on filter paper, blow dry with cold air, and then wrap them with filter paper. Store them in a desiccator and measure the size and weigh them after leaving them for 1 hour, with an accuracy of 0.1mg.

[0086] Based on the reactor volume, simulated water was placed in the reactor. Nitrogen was first passed through the simulated water for 0.5 hours to remove oxygen from the simulated water. The treated N80 corrosion coupon was then added. The reactor lid was sealed, and the CO2 pressure required for the experiment was set according to the actual site conditions. The reactor was then kept at the actual site temperature for a static corrosion evaluation experiment lasting 72 hours. Three parallel experiments were performed for each group of experiments, and the average value of the parallel experiments was taken as the measurement result.

[0087] Remove the coupons that have completed the test cycle. Observe and record the surface corrosion status and corrosion product adhesion. Immediately rinse the test medium with clean water and dry the coupons with filter paper. Place the coupons in a container containing petroleum ether or acetone with a boiling range of 60°C-90°C. Gently wipe with absorbent cotton. Then soak in anhydrous ethanol for 5 minutes for further degreasing and dehydration. Remove the coupons and soak them in an acid cleaning solution prepared according to Appendix A of SY / T5273-2000 for 5 minutes. Simultaneously, use tweezers to gently wipe the corrosion products on the coupon surface. Remove the coupons from the cleaning solution, rinse with tap water to remove any residual acid on the surface, and immediately immerse them in a sodium hydroxide solution (60g / L). After 30 seconds, rinse with tap water, and then soak in anhydrous ethanol for approximately 5 minutes, washing and dehydrating twice. Take out the hanging piece and place it on filter paper, blow it dry with cold air, then wrap the hanging piece with filter paper, store it in a desiccator, and weigh it after leaving it for 1 hour, with an accuracy of 0.1 mg.

[0088] Indoor evaluation test results:

[0089] The corrosion rate is calculated as follows:

[0090]

[0091] Where: r corr ——Uniform corrosion rate, mm / a; m——Mass of coupon before test, g; m t ——The mass of the coupon after the test, g; S1——The total area of ​​the coupon, cm 2 ;ρ——density of the coupon material, g / cm 3 ; t——test time, h.

[0092] The specific experimental results are shown in Table 2:

[0093] Table 2. Anticorrosion performance evaluation table

[0094] Evaluation Project Evaluation results Corrosion rate (blank) 3.962mm / a Corrosion rate (casing protection fluid) 0.026mm / a

[0095] On-site evaluation:

[0096] Coupons with a one-month corrosion cycle were retrieved from the well. The post-field corrosion treatment and corrosion rate calculation procedures were the same as those used in the laboratory experiment. After the casing protection fluid was injected into the field test well, the corrosion rate of the corrosion coupons was measured to be only 0.001 mm / a.

[0097] Example 3:

[0098] 15 tons of casing protection fluid was synthesized using the following preparation method:

[0099] (1) Weigh 684 kg of water into a reactor and heat it to 40°C while stirring.

[0100] (2) Weigh 60 kg of polyoxyethylene rosin amine and add it to the reactor, stirring for 5 minutes;

[0101] (3) Weigh 60 kg of rosin imidazoline and add it to the reactor, stirring for 5 minutes;

[0102] (4) Weigh 60 kg of imidazoline oleate into the reactor and stir for 5 minutes;

[0103] (5) Weigh 120 kg of amide imidazoline and add it to the reactor, stirring for 5 minutes;

[0104] (6) Weigh 96 kg of bisimidazoline corrosion inhibitor and add it to the reactor, stirring for 20 minutes;

[0105] (7) Weigh 120 kg of pulp waste liquid into the reactor and stir for 20 minutes;

[0106] (8) Stop heating and lower the temperature of the reactor to room temperature to obtain Agent A.

[0107] (9) Weigh 9075 kg of water in 15m 3 In the mixing tank, add 225 kg of glycerol polyoxypropylene polyoxyethylene ether while stirring and stir for 15 minutes.

[0108] (10) Add 1200 kg of Agent A to the mixing tank while stirring for 15 minutes;

[0109] (11) Add 4500 kg of ethylene glycol and stir for 20 minutes to obtain the casing protection liquid.

[0110] In step (1), the reactor temperature is raised to 40±1°C;

[0111] In steps (1)-(7), the stirring speed is 45 rpm.

[0112] In steps (9)-(11), the stirring speed is 60 rpm.

[0113] Evaluation of the effect of the casing protection liquid prepared in Example 3:

[0114] Indoor evaluation experimental steps:

[0115] Before the experiment, wipe the corrosion coupons with filter paper, then place them in a container filled with petroleum ether or acetone with a boiling range of 60℃-90℃, remove the grease on the surface of the coupons with absorbent cotton, and then soak them in anhydrous ethanol for about 5 minutes for further degreasing and dehydration. After taking out the coupons, place them on filter paper, blow dry with cold air, and then wrap them with filter paper. Store them in a desiccator and measure the size and weigh them after leaving them for 1 hour, with an accuracy of 0.1mg.

[0116] Based on the reactor volume, simulated water was placed in the reactor. Nitrogen was first passed through the simulated water for 0.5 hours to remove oxygen from the simulated water. The treated N80 corrosion coupon was then added. The reactor lid was sealed, and the CO2 pressure required for the experiment was set according to the actual site conditions. The reactor was then kept at the actual site temperature for a static corrosion evaluation experiment lasting 72 hours. Three parallel experiments were performed for each group of experiments, and the average value of the parallel experiments was taken as the measurement result.

[0117] Remove the coupons that have completed the test cycle. Observe and record the surface corrosion status and corrosion product adhesion. Immediately rinse the test medium with clean water and dry the coupons with filter paper. Place the coupons in a container containing petroleum ether or acetone with a boiling range of 60°C-90°C. Gently wipe with absorbent cotton. Then soak in anhydrous ethanol for 5 minutes for further degreasing and dehydration. Remove the coupons and soak them in an acid cleaning solution prepared according to Appendix A of SY / T5273-2000 for 5 minutes. Simultaneously, use tweezers to gently wipe the corrosion products on the coupon surface. Remove the coupons from the cleaning solution, rinse with tap water to remove any residual acid on the surface, and immediately immerse them in a sodium hydroxide solution (60g / L). After 30 seconds, rinse with tap water, and then soak in anhydrous ethanol for approximately 5 minutes, washing and dehydrating twice. Take out the hanging piece and place it on filter paper, blow it dry with cold air, then wrap the hanging piece with filter paper, store it in a desiccator, and weigh it after leaving it for 1 hour, with an accuracy of 0.1 mg.

[0118] Indoor evaluation test results:

[0119] The corrosion rate is calculated as follows:

[0120]

[0121] Where: r corr ——Uniform corrosion rate, mm / a; m——Mass of coupon before test, g; m t ——The mass of the coupon after the test, g; S1——The total area of ​​the coupon, cm 2 ;ρ——density of the coupon material, g / cm 3 ; t——test time, h.

[0122] The specific experimental results are shown in Table 2:

[0123] Table 3. Anticorrosion performance evaluation table

[0124]

[0125]

[0126] On-site evaluation:

[0127] Coupons with a one-month corrosion cycle were retrieved from the well. The post-field corrosion treatment and corrosion rate calculation procedures were the same as those used in the laboratory experiment. After the casing protection fluid was injected into the field test well, the corrosion rate of the corrosion coupons was measured to be only 0.001 mm / a.

[0128] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A carbon dioxide flooding casing protection fluid, characterized in that: The mass ratio of each raw material component of the casing protection liquid is: 4-8 portions of A dose 0.5-1.5 parts of glycerol polyoxypropylene polyoxyethylene ether 20-30 parts of ethylene glycol 60.5-75.5 parts of water; The mass ratio of the raw material components of Agent A is: 5-10 parts of polyoxyethylene rosin amine 5-15 parts of rosin imidazoline 5-10 parts of oleic acid imidazoline 10-15 parts of amide imidazoline 8-10 parts of bisimidazoline corrosion inhibitor 8-10 parts of pulp waste liquid 30-59 parts water.

2. The method for preparing a carbon dioxide flooding casing protection fluid according to claim 1, wherein: Among them A The preparation method of the agent comprises: (1) Weigh water into the reactor and heat it to 40°C while stirring; (2) Weigh polyoxyethylene rosin amine and add it to the reactor, stirring for 5 minutes; (3) Weigh rosin imidazoline and add it into the reactor, stirring for 5 minutes; (4) Weigh oleic acid imidazoline and add it to the reactor, stirring for 5 minutes; (5) Weigh amide imidazoline and add it into the reactor, stirring for 5 minutes; (6) Weigh the bisimidazoline corrosion inhibitor and add it to the reactor, stirring for 20 minutes; (7) Weigh the pulp waste liquid and add it into the reactor, stirring for 20 minutes; (8) Stop heating and lower the temperature of the reactor to room temperature to obtain Agent A.

3. The method for preparing a carbon dioxide flooding casing protection fluid according to claim 1, wherein: The details are as follows: (1) Weigh 180 kg to 708 kg of water into a reactor and heat it to 40°C while stirring; (2) Weigh 30 kg to 120 kg of polyoxyethylene rosin amine and add it to the reactor, stirring for 5 minutes; (3) Weigh 30 kg to 180 kg of rosin imidazoline and add it to the reactor, stirring for 5 minutes; (4) Weigh 30 kg to 120 kg of imidazoline oleate into the reactor and stir for 5 minutes; (5) Weigh 60 kg to 180 kg of amide imidazoline into the reactor and stir for 5 minutes; (6) Weigh 48 kg to 120 kg of bisimidazoline corrosion inhibitor and add it to the reactor, stirring for 20 minutes; (7) Weigh 48 kg to 120 kg of pulp waste liquid into the reactor and stir for 20 minutes; (8) Stop heating and lower the temperature of the reactor to room temperature to obtain Agent A; (9) Weigh 9075 kg - 11325 kg of water in 15m 3 In a mixing tank, add 75 kg to 225 kg of glycerol polyoxypropylene polyoxyethylene ether while stirring and stir for 15 minutes; (10) Add 600 kg - 1200 kg of Agent A into the mixing tank, stirring for 15 minutes; (11) Add 3000 kg to 4500 kg of ethylene glycol and stir for 20 minutes to obtain the casing protection liquid.

4. The preparation method according to claim 2, wherein: The specific preparation is as follows: (a) Weigh water at 15m 3 In a mixing tank, add glycerol polyoxypropylene polyoxyethylene ether while stirring and stir for 15 minutes; (b) Add Agent A to the mixing tank while stirring for 15 minutes; (c) Add ethylene glycol and stir for 20 minutes to obtain a casing protection solution.

5. The preparation method according to claim 4, characterized in that: In step (1), the reactor is heated to 40±1°C.

6. The preparation method according to claim 5, characterized in that: In steps (1) to (7), the stirring speed is 45 rpm.

7. The preparation method according to claim 6, characterized in that: In steps (a) to (c), the stirring speed is 60 rpm.

8. Use of the casing protection fluid according to claim 1 in a carbon dioxide injection well.

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