温度和O_(2)含量在CO_(2)/H_(2)S/O_(2)体系中对输气管道的腐蚀行为研究

Corrosion Behavior of High Temperature and O_(2) Content on Gas Pipelines in CO_(2)/H_(2)S/O_(2) System

目的 为给新疆油田输气管道的腐蚀防控提供依据,揭示L360NS钢在CO_(2)/H_(2)S/O_(2)共存体系中不同O_(2)含量(物质的量分数0%~2%)和不同温度(60~180℃)工况下的腐蚀行为。方法 以新疆油田HN区块输气管道为研究背景,基于现场运行工况设计高温高压反应釜试验方案,选择L360NS钢为试样进行失重法、腐蚀产物表征、基体形貌表征、腐蚀缺陷深度测试等试验。结果 随O_(2)含量增大,L360NS钢的均匀腐蚀速率从0.299 1 mm/a逐渐增大到0.912 3 mm/a。试样表面出现腐蚀缺陷,且随O_(2)含量升高有逐渐扩大的趋势,腐蚀产物膜呈楔形、多方晶体状,大小不一。温度(60~180℃)升高,L360NS钢的均匀腐蚀速率从2.103 4 mm/a逐渐降低到0.457 0 mm/a,腐蚀缺陷逐渐减小,产物膜结构由稀松多孔逐渐转为致密。结论 由于O_(2)具有强氧化性及去极化效应,导致在产物中出现Fe的高价氧化物,结构疏松多孔。另一方面,H2S与O_(2)发生交互作用生成单质S,单质S的强氧化性与水解反应,两种作用相互影响,促进钢材腐蚀。在CO_(2)/H_(2)S/O_(2)腐蚀环境中,温度升高,一定程度上促进腐蚀反应动力学,但是升温会促进Fe CO_(3)沉淀,导致腐蚀产物膜结构致密,阻碍腐蚀性介质与基体接触,抑制腐蚀。

With the rapid development of industries such as transportation and petrochemicals,the demand for energy such as oil and natural gas continues to increase.Heavy oil reservoirs that account for a large proportion of petroleum resources have attracted the extensive attention of a large number of scholars.For example,multi-component thermal fluid flooding was adopted as an effective technology to recover heavy oil in Xinjiang Oilfield.The high temperature and strong corrosive medium will directly accelerate the corrosion of the gas pipelines due to the high temperature of the multi-component thermal fluid,which poses a huge threat to the safe operation of the gas pipelines in Xinjiang Oilfield.In this article,to provide a basis for corrosion prevention and control of gas pipelines in Xinjiang Oilfield,the corrosion behavior of L360NS steel was researched by the corrosion weight loss method under different O_(2) content(0-2mol%)and temperature(60-180℃)in CO_(2)/H_(2)S/O_(2) coexistence system.The experimental scheme of high temperature and high-pressure autoclaves is formulated by operating conditions of the gas pipelines in the Xinjiang oilfield in this paper.The corrosion solution is simulated formation water,and the experimental sample is an L360NS steel pipe.Surface characterization of corrosion scales using SEM,EDS,and XRD showed that O_(2) content(0mol%-2mol%)and temperature(60-180℃)notably changed the characteristics of corrosion scales.The results showed that the average corrosion rate of L360NS steel gradually increased from 0.2991 mm/a to 0.9123 mm/a with the increased O_(2) content(0-2mol%).The corrosion product film is of different shapes as wedge-shaped and polycrystalline and corrosion defects showed a gradually enlarging trend on the surface of the samples.There are two reasons why O_(2) content affects the corrosion rate.The appearance of loose and porous Fe high-valent oxides is due to the strong oxidizing and depolarizing effects of O_(2) on the surface of the corrosion product.Depolarization and strong oxidization generate high-valent oxides of Fe(such as Fe2O3,and Fe3O4),the product film structure gradually becomes loose,the protection performance decreases,and the corrosion degree is deepened.The synergistic effect of O_(2) and H2S generates elemental S,and elemental S is easily hydrolyzed in solution to generate H2SO4,which will induce the formation of local corrosion defects in the low pH area,further promoting local corrosion.The average corrosion rate of L360NS steel gradually decreases from 2.1034 mm/a to 0.4570 mm/a with the increase in temperature(60-180℃).Corrosion defects are gradually reduced and the structure of corrosion product film changes from porous to dense gradually.The corrosion product of Grain-like products decreases and grains become smaller,polygonal crystal-like products increase.The temperature mainly affects the product film's structure to inhibit steel's corrosion.In CO_(2)/H_(2)S/O_(2) corrosive coexistence system,the higher temperature promotes the corrosive reaction kinetics to a certain extent,but the higher temperature will promote the formation of FeCO_(3),resulting in a dense corrosion product film structure that hinders the contact between the corrosion medium and the substrate and inhibits corrosion.