School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
ExxonMobil Upstream Research Company, Spring, Texas, USA.
Appl Environ Microbiol. 2019 Jan 23;85(3). doi: 10.1128/AEM.01891-18. Print 2019 Feb 1.
Oil reservoir souring and associated material integrity challenges are of great concern to the petroleum industry. The bioengineering strategy of nitrate injection has proven successful for controlling souring in some cases, but recent reports indicate increased corrosion in nitrate-treated produced water reinjection facilities. Sulfide-oxidizing, nitrate-reducing bacteria (soNRB) have been suggested to be the cause of such corrosion. Using the model soNRB sp. strain CVO obtained from an oil field, we conducted a detailed analysis of soNRB-induced corrosion at initial nitrate-to-sulfide (N/S) ratios relevant to oil field operations. The activity of strain CVO caused severe corrosion rates of up to 0.27 millimeters per year (mm y) and up to 60-μm-deep pitting within only 9 days. The highest corrosion during the growth of strain CVO was associated with the production of zero-valent sulfur during sulfide oxidation and the accumulation of nitrite, when initial N/S ratios were high. Abiotic corrosion tests with individual metabolites confirmed biogenic zero-valent sulfur and nitrite as the main causes of corrosion under the experimental conditions. Mackinawite (FeS) deposited on carbon steel surfaces accelerated abiotic reduction of both sulfur and nitrite, exacerbating corrosion. Based on these results, a conceptual model for nitrate-mediated corrosion by soNRB is proposed. Ambiguous reports of corrosion problems associated with the injection of nitrate for souring control necessitate a deeper understanding of this frequently applied bioengineering strategy. Sulfide-oxidizing, nitrate-reducing bacteria have been proposed as key culprits, despite the underlying microbial corrosion mechanisms remaining insufficiently understood. This study provides a comprehensive characterization of how individual metabolic intermediates of the microbial nitrogen and sulfur cycles can impact the integrity of carbon steel infrastructure. The results help explain the dramatic increases seen at times in corrosion rates observed during nitrate injection in field and laboratory trials and point to strategies for reducing adverse integrity-related side effects of nitrate-based souring mitigation.
油藏酸化和相关的材料完整性挑战是石油工业非常关注的问题。硝酸盐注入的生物工程策略已被证明在某些情况下可以成功控制酸化，但最近的报告表明，在硝酸盐处理后的采出水回注设施中，腐蚀加剧了。已经有人提出，硫化物-氧化、硝酸盐还原菌（soNRB）是造成这种腐蚀的原因。本研究使用从油田获得的模型 soNRB 种 sp. 菌株 CVO，在与油田作业相关的初始硝酸盐与硫化物（N/S）比的情况下，对 soNRB 引起的腐蚀进行了详细分析。菌株 CVO 的活性导致了严重的腐蚀速率，高达 0.27 毫米/年（mm y），仅 9 天内就形成了 60-μm 深的点蚀。在菌株 CVO 生长过程中，当初始 N/S 比较高时，硫化物氧化过程中产生的零价硫和亚硝酸盐的积累与最高的腐蚀相关。在单独代谢物的非生物腐蚀试验中，证实了生物成因的零价硫和亚硝酸盐是在实验条件下腐蚀的主要原因。在碳钢表面沉积的菱铁矿（FeS）加速了硫和亚硝酸盐的非生物还原，从而加剧了腐蚀。基于这些结果，提出了 soNRB 通过硝酸盐介导的腐蚀的概念模型。与注入硝酸盐控制酸化相关的腐蚀问题的含糊报告需要更深入地了解这种经常应用的生物工程策略。尽管对微生物腐蚀机制的了解仍不够充分，但仍有人提出硫化物氧化、硝酸盐还原细菌是关键罪魁祸首。本研究全面描述了微生物氮和硫循环的单个代谢中间产物如何影响碳钢基础设施的完整性。研究结果有助于解释在现场和实验室试验中，硝酸盐注入时腐蚀速率有时会急剧增加，并指出了减少基于硝酸盐的酸化缓解的不利完整性相关副作用的策略。
