Corrosion of offshore oil-gas gathering and transportation pipelines can lead to serious environmental risks and economic losses. With the continuous development of China's marine energy industry, it is imperative to accelerate the rational exploitation and utilization of offshore oil-gas resources as well as upgrade the oil-gas production equipment. As an important part of oil-gas gathering and transportation networks, submarine pipeline is known as the "artery" of offshore oil-gas production systems. Under actual working conditions, submarine pipelines are inevitably exposed to corrosion and failure. Microbiologically influenced corrosion (MIC) has been considered one of the main factors causing this problem. According to statistics, more than 20% of the oil-gas pipeline corrosion and oil leakage accidents are directly or indirectly related to MIC. The vast ocean includes a wide range of extreme environments such as high salt, high pressure, and low temperature environments. Marine environments are more diverse and complex than terrestrial environments, indicating that marine microbes are more tolerant to extreme conditions. Herein, the sources of corrosive microorganisms in offshore oil-gas pipelines, including reservoir endogenous microorganisms, exogenous microorganisms introduced by seawater injection, and microbial enhanced oil recovery, were classified. The characteristics of fluid chemical substances in submarine reservoirs were analyzed. It was confirmed that they were rich in methane, sulfides, and volatile fatty acids, and they were classified according to the characteristics of endogenous microbial metabolism and products, including sulfate-reducing bacteria, methanogens, fermentative bacteria, and iron-reducing bacteria. Moreover, the characteristics of microbial community abundance in the produced water of an oilfield were analyzed with an example, and the evolution rule of the microbial community under long-term oilfield environmental stress was clarified. Complex gathering and transport networks are particularly prone to biofilm formation and metabolite accumulation, which may cause or exacerbate corrosion problems. A corrosive biofilm, composed of various environmental microorganisms, is a general life form used by microorganisms to resist changes in the external environment and maintain homeostasis of the internal environment, which includes a complex symbiotic relationship between microorganisms with different metabolic characteristics. Accordingly, theories of metabolite-MIC, extracellular electron transfer-MIC, and synergism/antagonism among corrosive microorganisms in offshore pipeline networks were further reviewed. Pure/mixed culture in laboratory conditions can hardly represent the complexity of in situ biofilms in oil-gas pipelines; therefore, it is almost impossible to reconstruct the corrosion behavior of microorganisms in a real service environment. Industrial bactericides are one of the most widely used strategies for MIC in oil-gas pipeline networks. Advanced composite bactericides often possess broad-spectrum antibacterial properties, low toxicity, and sustained bactericidal activity. However, bactericides have drawbacks such as increased microbial resistance, difficulty in degradation, and deterioration of crude oil quality. Therefore, it is extremely challenging to detect the corrosive microbial community and the metabolic processes leading to corrosion accurately under actual working conditions. Advanced biological detection technologies, including environmental genomics, microfluidics, and high-throughput rapid detection technology, should be fully utilized in future research on the MIC of oil-gas pipelines. In this paper, the types of potential microbial species, types of MIC, and the corrosion mechanisms are summarized in detail, and novel anti-corrosion methods based on biotechnology are proposed. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.
