Effect of salt-resistant polymer flooding system SRB on corrosion behavior of 20# carbon steel under deposition

As a means of enhancing oil recovery, salt-resistant polymer flooding technology has been gradually promoted in oilfields. However, due to the excessively high mineralization of the water in which the polymer is configured, contains a large amount of solid impurities, and is not compatible with the formation water, scaling often occurs in the pipeline. In addition, because the pipeline produced fluid contains a large amount of polymers, which provides a stable carbon source for microorganisms, and most of the pipelines are buried underground, which also provides an oxygen-deficient environment for bacteria to survive. Therefore, the pipeline suffered more serious corrosion under the action of scaling and microorganisms. The objective of this study was to investigate the corrosion behavior of sulfate reducing bacteria (SRB) on pipelines under deposition (CaCO3). In this study, 20# carbon steel was used as the experimental material, and the solution was configured to simulate the field sewage in the laboratory, and the weight loss test and electrochemical test were carried out. Combined with the experimental results, scanning electron microscopy, XRD, open circuit potential, polarization curve, electrochemical impedance spectroscopy and wire-beam electrode tests were used to explore the corrosion behavior mechanism of SRB in oilfield pipelines under the anti-salt polymer flooding system under deposition. The results showed that the CaCO3 deposition layer provides an anaerobic environment for SRB, and the corrosion rate of the SRB system is significantly increased. The pitting corrosion of the SRB system is more serious than that of the sterile system. SRB promotes galvanic corrosion under deposition.

Automated summary

Salt-resistant polymer flooding technology has been widely promoted in oilfields, however, the high mineralization and solid impurities in the water used for polymer configuration, as well as its incompatibility with formation water, often lead to scaling in the pipelines. Additionally, the presence of polymers and anaerobic conditions in buried pipelines create an environment that facilitates corrosion by microorganisms. This study investigated the corrosion behavior of sulfate reducing bacteria (SRB) on pipelines under CaCO3 deposition using different tests and analysis techniques. The results showed that the deposition layer provided an anaerobic environment for SRB, significantly increasing corrosion rate and promoting galvanic corrosion under deposition.