Medicament filling method for controlling corrosion of steel pipeline in different life cycles

Abstract

The invention relates to an agent filling method for controlling corrosion of a steel pipeline in different life cycles, which comprises the following steps of: 1) dividing the agent filling method of the steel pipeline into four schemes according to the full life cycle of the operation of a pipe network, the two schemes are respectively a medicament filling scheme in a recovery period, a medicament filling scheme in a production period, a medicament filling scheme in a ball passing period and a medicament filling scheme in a shutdown period; and (2) in the four filling schemes, chemical agents are screened according to different operating environments and different corrosion factors of the steel pipeline, and the chemical agents comprise a corrosion inhibitor, a sterilizing agent and / or a scale inhibitor. According to the chemical filling method for controlling corrosion of the steel pipeline in different life cycles, the problem that chemical filling for controlling corrosion of the steel pipeline lacks pertinence and effectiveness is solved.

Description

Technical Field

[0001] This application belongs to the field of corrosion control of oil and gas field surface gathering and transportation systems. Specifically, this application relates to a method for injecting chemicals to control the corrosion of steel pipelines. Background Art

[0002] The composition of the medium transported by surface gathering and transportation steel pipelines is complex and the medium has strong corrosivity. The corrosion rate is as high as 1 mm / year. Without injecting chemicals, the steel pipeline will perforate after 5 years of operation. The main corrosion risks include carbon dioxide corrosion, hydrogen sulfide corrosion, under-deposit corrosion or sediment under-deposit corrosion, bacterial corrosion, oxygen corrosion, etc. Chemical injection is one of the economical and effective methods for controlling such corrosion. The chemical agents injected on-site form a comprehensive system. Various factors need to be comprehensively considered to determine the injection method so that the injected chemicals can control the corrosion. Otherwise, it will lead to aggravated internal corrosion of the steel pipeline. For example, after the chemical agent is changed or optimized, the compatibility of the chemical agents is poor; when a new formation is put into production, the water quality is incompatible, resulting in scale formation in the pipeline. At this time, the previous chemical agent should not be injected, but other scale inhibitors or scale and corrosion inhibitors or water should be adjusted after water quality analysis to avoid scale formation, thereby avoiding under-deposit corrosion; bacteria existing in the formation and bacteria introduced into the surface process during the pipeline commissioning and operation, such as sulfate-reducing bacteria, iron bacteria, and saprophytic bacteria, and at the same time, formation sand production or other organic or inorganic sediments provide a living place for the settlement of microorganisms, resulting in microbial corrosion on the inner wall of the steel pipeline. At this time, the previous anti-corrosion chemical agent is no longer effective for microbial corrosion; excessive oxygen is introduced into the pipeline during various operations. For example, after the produced water undergoes water treatment with aeration and sterilization and then returns to the formation without deoxygenation, it brings oxygen corrosion to the pipeline; the quality of the added corrosion inhibitor chemical agent itself is poor or the chemical agent is not screened specifically, resulting in little effect of the chemical agent; the increase in liquid flow rate causes erosion, and part of the corrosion inhibitor on the inner wall of the pipeline is washed away, making its internal adhesion uneven and causing local corrosion. Seriously corroded steel pipelines will directly perforate and crack, resulting in oil and gas leakage, causing environmental pollution, property losses, and even fire and explosion, with serious safety and environmental impacts.

[0003] The existing invention patent with the application number CN202210996515 discloses a method for controlling seawater corrosion during the laying of submarine pipelines. During the laying of submarine pipelines, a certain mass of anti-seawater corrosion chemicals is adhered to the inner wall of the pipeline at regular intervals by using an adhesive to achieve seawater corrosion control. The chemicals include bactericides, corrosion inhibitors, and deoxidizers. Each single chemical agent has an anti-corrosion control effect on the pipeline, but the injection plan at different times, the coupling relationship between the chemical agents, and the impact of the chemical agent coupling on the pipeline corrosion risk are not clear, and the safe control of the pipeline cannot be achieved.

[0004] The existing invention patent with the application number CN202210996517 discloses a method for seawater corrosion control before the commissioning of submarine pipelines. By pre-filming the inner wall of the pipeline with a liquid anti-seawater corrosion agent before laying the submarine pipeline, the multi-effect functions of sterilization, corrosion inhibition, and deoxygenation are achieved. For the pre-filming treatment of the agent, only the pre-filming thickness is determined, but the uniformity and coverage of the agent pre-filming are not verified. Moreover, only the agent during laying, installation, and before commissioning is considered, and there is no dosing plan for the entire life cycle of the pipeline, which cannot guarantee the effectiveness of the agent in protecting the pipeline.

[0005] Therefore, the reason for the increase in corrosion rate should not be simply attributed to the poor effect of the corrosion inhibitor. Based on a full analysis of the reasons and on the premise of ensuring the quality of the agent, the types of agents to be added and the dosing methods of the agents should be clarified during different periods of pipeline operation. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail in this article. This overview is not intended to limit the scope of protection of this application.

[0007] This application provides a dosing method for controlling the corrosion of steel pipelines during different life cycles. The dosing method for controlling the corrosion of steel pipelines during different life cycles provided by this application solves the problems of lack of pertinence and effectiveness in controlling the corrosion in the agent of steel pipelines.

[0008] This application provides a dosing method for controlling the corrosion of steel pipelines during different life cycles, including the following steps:

[0009] 1) According to the entire life cycle of the pipeline network operation, the dosing method of the steel pipeline is divided into four schemes, namely the dosing scheme during the resumption of production period, the dosing scheme during the production period, the dosing scheme during the pigging period, and the dosing scheme during the shutdown period;

[0010] 2) In the four dosing schemes, according to the different operating environments and different corrosion factors of the steel pipeline, chemical agents are screened, and the chemical agents include corrosion inhibitors, bactericides, and / or scale inhibitors.

[0011] In the embodiment of this application, during the dosing scheme during the resumption of production period, bactericides are used for sterilization and corrosion inhibitors are used for pre-filming.

[0012] In the embodiment of this application, during the dosing scheme during the resumption of production period, after the pipeline is put into production, bactericides are added for sterilization once at the wellhead, and the dosing time is 6 - 8 hours. The bactericides are added in an impact dosing manner; corrosion inhibitors are continuously added at the manifold. Preferably, a pre-filming concentration of 100 - 150 ppm of corrosion inhibitor is used for pre-filming with the corrosion inhibitor.

[0013] In the embodiments of the present application, in the injection plan during production, the situations where corrosion inhibitors need to be enabled for steel pipelines are as follows: the monitoring results show that the pipeline corrosion intensifies; the slow-release rate of the corrosion inhibitor is low; the operating state of the pipeline changes significantly.

[0014] In the embodiments of the present application, in the injection plan during production, the situations where scale inhibitors need to be enabled for steel pipelines are as follows: the fouling on coupon or pigging is serious; obvious calcium carbonate, barium sulfate, and strontium sulfate appear in the scale sample analysis; the compatibility between various chemicals after adding or replacing new chemicals; there are obvious changes in the working conditions of the steel pipeline or the fouling trend shows an increasing trend.

[0015] In the embodiments of the present application, in the injection plan during production, the situations where bactericides need to be enabled for steel pipelines are as follows: the bacterial count in the water samples at the inlet and outlet of the steel pipeline does not meet the standard; the H 2 S content at the outlet of the steel pipeline exceeds the standard or increases significantly, or the H 2 S concentration difference between the inlet and outlet of the steel pipeline is > 100 ppm for two consecutive times; the bactericide loses its effect or bacteria develop drug resistance.

[0016] In the embodiments of the present application, in the injection plan during pigging, the pigging operation of the steel pipeline is carried out in combination with inhibitor pre-filming and bactericide injection.

[0017] In the embodiments of the present application, in the injection plan during pigging, the implementation methods of the pigging operation of the steel pipeline in combination with inhibitor pre-filming and bactericide injection are as follows: ① Determine the pigging operation time of the steel pipeline; ② Inject bactericide by impact from the inlet of the steel pipeline after the last pig enters the steel pipeline during the pigging operation of the steel pipeline; ③ The inhibitor is pre-filmed continuously for 24 hours at a pre-filming concentration of 100 - 150 ppm.

[0018] In the embodiments of the present application, in the injection plan during the shutdown of the steel pipeline, corrosion inhibitors, bactericides, and scale inhibitors are injected into the inlet of the steel pipeline to carry out anti-corrosion treatment on the inner wall of the pipeline, and pipeline batch treatment agents or deoxidizers can be added according to the corrosion situation of the remaining liquid.

[0019] In the embodiments of the present application, the corrosion inhibitor is selected from adsorption film type corrosion inhibitors, such as imidazoline quaternary ammonium salts, tallow amine, cetylamine, and octadecylamine; the bactericide is selected from non-oxidizing bactericides, such as dodecyl dimethyl benzyl ammonium chloride, bisquaternary ammonium salts, organic bromides, glutaraldehyde, THPS, and organic guanidine types; the scale inhibitor is selected from organic phosphate scale inhibitors, such as polyol phosphate or polyoxyethylene phosphate.

[0020] In the embodiments of the present application, the injection sites of chemical agents include downhole of single wells, metering stations, valve group manifolds, gathering stations, etc.

[0021] The chemical agent injection method for controlling the corrosion of steel pipelines in different production periods provided by this application, as well as the triggering conditions for chemical agent evaluation and screening, solve the problem of lack of pertinence and effectiveness in the corrosion control of steel pipelines.

[0022] Other features and advantages of this application will be described in the following specification, and in part, will be obvious from the specification, or will be understood by implementing this application. Other advantages of this application can be realized and obtained through the solutions described in the specification. Detailed implementation manners

[0023] To make the objectives, technical solutions, and advantages of this application clearer and more understandable, the embodiments of this application will be described in detail below. It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined arbitrarily with each other.

[0024] The embodiment of this application provides a chemical agent injection method for controlling the corrosion of steel pipelines in different life cycles, including the following steps:

[0025] 1) According to the full life cycle of the pipeline network operation, the chemical agent injection method for steel pipelines is divided into four schemes, namely, the chemical agent injection scheme during the resumption of production period, the chemical agent injection scheme during the production period, the chemical agent injection scheme during the pigging period, and the chemical agent injection scheme during the shutdown period;

[0026] 2) Among the four injection schemes, according to the different operating environments and different corrosion factors of the steel pipelines, chemical agents are screened, and the chemical agents include corrosion inhibitors, bactericides, and / or scale inhibitors.

[0027] In the embodiment of this application, in the chemical agent injection scheme during the resumption of production period, bactericides are used for sterilization and corrosion inhibitors are used for pre-filming.

[0028] In the embodiment of this application, in the chemical agent injection scheme during the resumption of production period, after the pipeline is put into production, bactericides are injected once at the wellhead for sterilization, the injection time is 6 - 8 hours, the bactericides are injected in an impact injection manner, and the concentration of the bactericides is 20 - 60 mg / L; corrosion inhibitors are continuously injected at the manifold. Preferably, pre-filming of the corrosion inhibitors is carried out continuously for 24 hours at a pre-filming concentration of 100 - 150 ppm, where the injection concentrations of the corrosion inhibitors and bactericides are calculated according to the water volume.

[0029] In the embodiment of this application, in the injection scheme during the production period, the situations where corrosion inhibitors need to be enabled for steel pipelines are as follows: the monitoring results show that the pipeline corrosion intensifies; the slow release rate of the corrosion inhibitor is low; the pipeline operation state changes significantly.

[0030] In the embodiments of the present application, in the injection plan during production, the situations where scale inhibitors need to be enabled for steel pipelines are as follows: severe fouling on coupon or pigging; obvious calcium carbonate, barium sulfate, and strontium sulfate in fouling sample analysis; compatibility between various chemicals after adding or replacing new chemicals; obvious changes in the operating conditions of steel pipelines or an increasing tendency of fouling.

[0031] In the embodiments of the present application, in the injection plan during production, the situations where bactericides need to be enabled for steel pipelines are as follows: the bacterial count in the water samples at the inlet and outlet of the steel pipeline does not meet the standard; the H 2 S content at the outlet of the steel pipeline exceeds the standard or increases significantly, or the H 2 S concentration difference between the inlet and outlet of the steel pipeline is >100 ppm for two consecutive times; the bactericide loses its effect or bacteria develop drug resistance.

[0032] In the embodiments of the present application, in the injection plan during production, if the on-site corrosion phenomenon is relatively serious, corrosion inhibitors are injected in a continuous injection manner at the wellhead or manifold, and the injection concentration is preferably 50 - 60 ppm; if the on-site fouling phenomenon is relatively serious, scale inhibitors are injected in a continuous injection manner at the wellhead or manifold, and the injection concentration is preferably 5 - 10 ppm.

[0033] In the embodiments of the present application, in the injection plan during production, bactericides are injected by the method of alternate shock injection at the wellhead or manifold. Preferably, the bactericides are injected once every 4 - 7 days, and the injection concentration is 200 - 300 ppm.

[0034] In the embodiments of the present application, in the injection plan during pigging, the pigging operation of the steel pipeline is carried out in combination with inhibitor pre-filming and bactericide injection.

[0035] In the embodiments of the present application, in the injection plan during pigging, the implementation method of combining the pigging operation of the steel pipeline with inhibitor pre-filming and bactericide injection is as follows: ① Determine the pigging operation time of the steel pipeline; ② After the last pig enters the steel pipeline during the pigging operation of the steel pipeline, bactericides are injected by shock injection from the inlet of the steel pipeline, and the shock injection concentration and injection time can be adjusted according to the actual pigging effect; ③ The inhibitor is pre-filmed continuously for 24 hours at a pre-filming concentration of 100 - 150 ppm. Preferably, the pre-filming concentration and pre-filming time of the inhibitor can be adjusted according to the actual effect, and then the chemical addition concentration can be reduced to the on-site injection concentration according to the on-site situation, and a wall thickness detection instrument is used to determine the uniformity and comprehensiveness of the inhibitor pre-filming.

[0036] In the embodiments of the present application, in the dosing scheme during the shutdown of the steel pipeline, corrosion inhibitors, bactericides, and scale inhibitors are injected into the inlet of the steel pipeline to perform anti-corrosion treatment on the remaining liquid in the pipeline, and a pipeline batch treatment agent or a deoxidizer can be added according to the pipeline corrosion situation.

[0037] In the embodiments of the present application, the corrosion inhibitor is selected from adsorption film type corrosion inhibitors, such as imidazoline quaternary ammonium salts, tallow amine, cetylamine, and octadecylamine; the bactericide is selected from non-oxidizing bactericides, such as dodecyl dimethyl benzyl ammonium chloride, bisquaternary ammonium salts, organic bromides, glutaraldehyde, THPS, and organic guanidine types; the scale inhibitor is selected from organic phosphate scale inhibitors, such as polyol phosphate esters and polyoxyethylene phosphate esters.

[0038] The sources of the materials used in Example 1 and the performance evaluation of the present application are as follows:

[0039] The bactericide is the bisquaternary ammonium salt bactericide 1227 from Zaozhuang Shibang Biotechnology Co., Ltd.

[0040] The corrosion inhibitor is the imidazoline quaternary ammonium salt from Hangzhou Kegang Environmental Protection Co., Ltd.

[0041] The scale inhibitor is the polyol phosphate ester PAPE from Hebei Longke Water Treatment Co., Ltd.

[0042] Example 1

[0043] The comprehensive dosing method of the medicaments in the embodiments of the present application is divided into four schemes according to the whole life cycle of the pipeline network operation, namely the dosing scheme during the resumption of production, the dosing scheme during production, the dosing scheme during pigging, and the dosing scheme during shutdown.

[0044] (1) Dosing scheme during the resumption of production

[0045] After the steel pipeline is restarted after special situations such as production stoppage and major repairs, it is necessary to use a bactericide for sterilization and a corrosion inhibitor for pre-filming. According to the results of medicament screening, after the pipeline is put into production, the bactericide can be injected once at the wellhead at the concentration recommended by the medicament supplier for about 6 hours. The bactericide is injected in an impact dosing manner, and the concentration and dosing time of the bactericide can be adjusted according to the actual effect.

[0046] The corrosion inhibitor is continuously injected at the manifold in a continuous dosing manner, and the corrosion inhibitor is pre-filmed continuously for 24 hours according to the pre-filming concentration (100 - 150 ppm) recommended by the medicament supplier. Subsequently, according to the on-site situation, the dosing concentration can be reduced to the on-site dosing concentration. The dosing concentrations of the corrosion inhibitor and the bactericide are calculated according to the water volume.

[0047] (2) Dosing scheme during production

[0048] The injection plan during the production period needs to be adjusted in combination with actual monitoring data.

[0049] If the on-site corrosion phenomenon is relatively serious, corrosion inhibitors can be injected continuously at the wellhead or manifold. The injection concentration is preferably about 50 ppm. In case of special working conditions, the injection concentration provided by the chemical agent supplier under special working conditions shall be followed for injection.

[0050] If the on-site scaling phenomenon is relatively serious, scale inhibitors can be injected continuously at the wellhead or manifold. The injection concentration is preferably about 5 ppm. In case of special working conditions, the injection concentration provided by the chemical agent supplier under special working conditions shall be followed for injection.

[0051] According to the actual situation, the method of alternative shock injection can be adopted at the wellhead or manifold for injection. Bactericides are injected once every 4 - 7 days, and the injection concentration of bactericides is 300 ppm. In case of special working conditions, the injection concentration provided by the chemical agent supplier under special working conditions shall be followed for injection; secondly, the shock injection frequency can be adjusted according to the results of bacteria monitoring.

[0052] (3) Injection plan during pigging

[0053] The pigging operation of steel pipelines needs to be implemented in combination with inhibitor pre-filming and bactericide injection. The implementation method is as follows: ① Determine the pigging operation time of steel pipelines; ② After the last pig enters the steel pipeline during the pigging operation of steel pipelines, bactericides are shock-injected from the inlet of the steel pipeline at the concentration recommended by the chemical agent supplier. The shock injection concentration and injection time can be adjusted according to the actual pigging effect; ③ The inhibitor is pre-filmed continuously for 24 hours at the pre-filming concentration (100 - 150 ppm) recommended by the chemical agent supplier. The inhibitor pre-filming concentration and pre-filming time can be adjusted according to the actual effect. Subsequently, according to the on-site situation, the chemical agent addition concentration can be reduced to the on-site injection concentration, and a wall thickness detection instrument is used to determine the uniformity and comprehensiveness of inhibitor pre-filming.

[0054] (4) Injection plan during the shutdown of steel pipelines

[0055] When the steel pipeline is shut down or out of production, chemical agents need to be injected into the inlet of the steel pipeline to perform anti-corrosion treatment on the remaining liquid in the pipeline. The chemical agents can be pipeline batch treatment agents or corrosion inhibitors, bactericides, scale inhibitors, deoxidizers, etc. The injection time shall ensure that the chemical agents can act on the entire steel pipeline at least. The injection concentration and injection time of the chemical agents can be adjusted according to the actual effect.

[0056] In the injection plan (2) during the production period, in order to ensure the effectiveness of the chemical agents, the types of chemical agents and the effects of the chemical agents need to be clarified. The chemical agents and triggering conditions are screened as follows:

[0057] In the dosing plan (2) during production, the cases where corrosion inhibitors need to be enabled for steel pipelines are as follows:

[0058] 1. Screen and evaluate corrosion inhibitors within 1 month under the following conditions:

[0059] ① The results of daily corrosion monitoring (such as coupon, probe, etc.) of the steel pipeline show that corrosion has intensified (the average corrosion rate of on-site coupon ≥ 0.250 mm / a or the maximum pitting rate ≥ 0.380 mm / a for 1 time, or the average corrosion rate ≥ 0.125 mm / a for 2 consecutive times, or the maximum pitting rate ≥ 0.21 mm / a for 2 consecutive times);

[0060] ② When the third-party evaluation of the corrosion inhibitor effect shows that the corrosion inhibition efficiency < 85%, and the average corrosion rate > 0.076 mm / a or the maximum pitting rate ≥ 0.13 mm / a after dosing the agent;

[0061] ③ After a significant change in the pipeline operation status, beyond the applicable working conditions of the in-use agent, it will lead to a decrease in the effectiveness of the agent and the inability to achieve the expected anti-corrosion effect. Including but not limited to:

[0062] a) The average water content is less than 30%;

[0063] b) The corrosive indicators in the medium components, such as CO 2 、H 2 S, sulfate-reducing bacteria SRB, saprophytic bacteria TGB, iron bacteria FB, etc. have changed significantly;

[0064] c) Substances with adsorption, precipitation, or substances that significantly change the fluid properties are brought in by the new well or workover fluid, such as pH value, Ca 2+ etc.;

[0065] d) Other possible special working condition fluctuations, etc.

[0066] ④ The internal inspection results of the steel pipeline show that corrosion has intensified, and after expert review, it is recommended to evaluate or screen the agent.

[0067] 2. Before replacing the agent, conduct a third-party evaluation of the new agent, and have the third party confirm the compatibility of the agent.

[0068] 3. When there are obvious changes in the working conditions of the steel pipeline or the corrosion monitoring data shows an increasing trend, conduct an evaluation of the corrosion inhibitor effect, and adjust and optimize the dosing of the corrosion inhibitor based on the evaluation effect.

[0069] In the dosing plan (2) during production, the cases where scale inhibitors need to be enabled for steel pipelines are as follows:

[0070] 1. When the surface of the coupon is severely fouled at the time of removal, a large amount of scale is removed during pigging, and the water quality changes significantly, etc., scale inhibitors should be added when the above factors occur; or when scale inhibitors are added but the effect of the scale inhibitor is not obvious, the dosing process should be optimized, and when it still does not meet the standard after optimizing the dosing process, a type change evaluation should be carried out. The scale inhibition efficiency of the scale inhibitor depends on the screening method, and the scale inhibition rate should be determined according to the actual situation (at least meeting the SY / T5673 standard).

[0071] 2. Obvious CaCO 3 such as in the scale sample analysis.

[0072] 3. Before adding or replacing the scale inhibitor, a third-party evaluation should be carried out on the new chemical agent, and the third party should confirm the compatibility of the chemical agent.

[0073] 4. When there are obvious changes in the operating conditions of the steel pipeline or the scaling trend shows an increasing trend, the effect of the scale inhibitor should be evaluated, and the dosing of the scale inhibitor should be adjusted and optimized according to the evaluation effect.

[0074] During the production period, in the dosing plan (2), the situations where bactericides need to be used in the steel pipeline are as follows:

[0075] 1. For the water samples at the inlet and outlet of the steel pipeline, the requirements are SRB ≤ 25 cells / mL, TGB ≤ 1000 cells / mL, and FB ≤ 1000 cells / mL. When these requirements are not met, optimization should be carried out. When it still does not meet the standard after optimization, a type change evaluation of the bactericide should be carried out.

[0076] 2. When the H 2 S content at the outlet of the steel pipeline increases significantly or the H 2 S concentration difference between the inlet and outlet of the steel pipeline is > 100 ppm for two consecutive times, the SRB detection at the outlet should be carried out, the quality inspection of the chemical agent should be carried out, and the preparation for the chemical agent evaluation should be started.

[0077] 3. When the bactericide loses its effect or the bacteria develop drug resistance, such as when the number of bacteria at the outlet of the steel pipeline two days after injecting the bactericide does not decrease compared with the day before injecting the bactericide, a chemical agent evaluation should be carried out.

[0078] Performance evaluation

[0079] The anti-corrosion and anti-scaling performance tests and microbial culture tests are carried out on the pipelines of the four dosing plans, and the evaluation tests on the slow-release, bactericidal, and scale inhibition effects are carried out to evaluate the application effect of the chemical agent.

[0080] The pipeline material is carbon steel, the outer diameter of the pipe is 159 mm, the wall thickness is 5 mm, the pipe length is 3.5 km, and the conveying medium is oil, gas, and water.

[0081] During the production period, when it is detected that the hydrogen sulfide concentration at the pipeline outlet increases significantly and the back pressure increases, after detection, it is determined that there are bacterial corrosion and scaling phenomena in the pipeline, and it is controlled by injecting anti-corrosion and anti-scaling chemical agents. The specific steps are as follows:

[0082] Among them, the added agent for resisting fluid corrosion and scaling is a mixed agent of bactericide, corrosion inhibitor and scale inhibitor, and the agent concentration is 60 ppm.

[0083] Anticorrosion and antiscaling performance test:

[0084] Take the fluid medium inside the pipe, separate the water sample, simply called produced water, conduct corrosion evaluation tests, scaling trend calculations, and microbial culture tests. Add it to the produced water at a concentration of 60 ppm, and conduct slow-release, bactericidal, and scale inhibition effect evaluation tests respectively to evaluate the injection effect of the agent.

[0085] The corrosion evaluation test refers to GB / T 19291-2003, the test period is 5 days. After the test is completed, remove the corrosion products according to the recommended method of GB / T-2015, and use the weight loss method to calculate the average corrosion rate after adding the agent.

[0086] The microbial culture test refers to SY / T 0532-2012, and the extinction dilution method is used to measure the concentrations of sulfate-reducing bacteria, saprophytic bacteria and iron bacteria in the produced water.

[0087] The scaling trend refers to SY / T 0600, and calculate the scaling trends of calcium carbonate, calcium sulfate and barium sulfate in the produced water.

[0088] Before adding the agent to the produced water, the corrosion rate is determined to be 0.2932 mm / a by the weight loss method. After adding the agent, the corrosion rate of carbon steel is 0.0433 mm / a, and the slow-release efficiency is 85.2%.

[0089] Before adding the agent to the produced water, the concentration of microbial sulfate-reducing bacteria is 1100 per mL. After adding the agent, no sulfate-reducing bacteria are detected.

[0090] Before adding the agent to the produced water, there are scaling trends of calcium carbonate and calcium sulfate. After adding the agent, there is no scaling trend.

[0091] Although the embodiments disclosed in this application are as above, the content described is only the embodiments adopted for the convenience of understanding this application, and is not used to limit this application. Any person skilled in the art within the scope of this application, without departing from the spirit and scope disclosed in this application, can make any modifications and changes in the form and details of the implementation, but the scope of patent protection of this application shall still be subject to the scope defined by the appended claims.

Claims

1. A method for injecting chemicals to control corrosion of steel pipelines in different life cycles, characterized in that, it includes the following steps: 1) According to the entire life cycle of pipeline network operation, the chemical injection methods for steel pipelines are divided into four schemes, namely, chemical injection scheme during resumption of production, chemical injection scheme during production, chemical injection scheme during pigging, and chemical injection scheme during shutdown. 2) Among the four injection schemes, chemical agents are screened according to different operating environments and different corrosion factors of the steel pipelines. The chemical agents include corrosion inhibitors, bactericides, and / or scale inhibitors.

2. The method according to claim 1, wherein, in the chemical injection scheme during resumption of production, bactericides are used for sterilization and corrosion inhibitors are used for pre-filming.

3. The method according to claim 1, wherein, in the chemical injection scheme during resumption of production, after the pipeline is put into production, bactericides are injected once at the wellhead for sterilization, and the injection time is 6 - 8 hours. The bactericides are injected in an impact injection manner; corrosion inhibitors are continuously injected at the manifold. Preferably, a corrosion inhibitor concentration of 100 - 150 ppm is used for pre-filming of the corrosion inhibitor.

4. The method according to claim 1, wherein, in the injection scheme during production, the situations where corrosion inhibitors need to be enabled for steel pipelines are: the monitoring results show that the pipeline corrosion intensifies; the slow release rate of the corrosion inhibitor is low; the pipeline operating state changes significantly.

5. The method according to claim 1, wherein, in the injection scheme during production, the situations where scale inhibitors need to be enabled for steel pipelines are: serious fouling on coupon or during pigging; obvious calcium carbonate, barium sulfate, strontium sulfate in the scale sample analysis; compatibility between various chemicals after adding or replacing new chemicals; obvious working condition changes or increasing fouling trend in the steel pipeline.

6. The method according to claim 1, wherein, In the dosing plan during production, the situations where bactericides need to be used for steel pipelines are as follows: the bacterial count in the water samples at the inlet and outlet of the steel pipeline does not meet the standard; the H 2 S content at the outlet of the steel pipeline exceeds the standard or increases significantly, or the difference in H 2 S concentration between the inlet and outlet of the steel pipeline is > 100 ppm for two consecutive times; the bactericide loses its effect or the bacteria develop drug resistance.

7. The method according to claim 1, wherein, in the injection scheme during pigging, the pigging operation of the steel pipeline is carried out in combination with pre-filming of corrosion inhibitor and injection of bactericide.

8. The method according to claim 6, wherein, in the injection scheme during pigging, the implementation method of the pigging operation of the steel pipeline in combination with pre-filming of corrosion inhibitor and injection of bactericide is as follows: ① Determine the pigging operation time of the steel pipeline; ② Inject bactericide in an impact injection manner from the inlet of the steel pipeline after the last pig enters the steel pipeline during the pigging operation of the steel pipeline; ③ The corrosion inhibitor is pre-filmed continuously for 24 hours at a pre-filming concentration of 100 - 150 ppm.

9. The method according to claim 1, wherein, in the injection scheme during shutdown of the steel pipeline, corrosion inhibitors, bactericides, and scale inhibitors are injected into the inlet of the steel pipeline to carry out anti-corrosion treatment on the inner wall of the pipe, and pipeline batch treatment agents or deoxidizers can be added according to the corrosion situation of the remaining liquid in the pipe.

10. The method according to any one of claims 1 - 9, wherein, The corrosion inhibitor is selected from adsorption film type corrosion inhibitors, such as imidazoline quaternary ammonium salts, tallow amine, cetylamine, octadecylamine; the biocide is selected from non-oxidizing biocides, such as dodecyl dimethyl benzyl ammonium chloride, bisquaternary ammonium salts, organic bromides, glutaraldehyde, THPS or organic guanidine types; the scale inhibitor is selected from organic phosphate scale inhibitors, such as polyol phosphate esters or polyoxyethylene phosphate esters.