Comparison of single and multiple times nitrate addition as microbial souring inhibitor to microbial community

摘要

Biological souring was known to cause corrosion by indirect mechanism of microbiologically influenced corrosion (MIC), in response to the problem, nitrate injection has been widely used to minimize the production of biological sulfide in oil and gas field. In environments exposed to seawater injection, nitrate is used to chemically and biologically control the growth of sulfate-reducing bacteria (SRB). However, the application of nitrate injection still ineffective, since the determination of the protocol (such as: nitrate concentration, injection methods, and injection period) still debatable. The aim of this study was to asses the suitable methods of nitrate injection to prevent souring by two different ways, single (4.5 mM nitrate) and multiple injection (three times; 1.5 mM nitrate for each addition), under artificial souring experiment, using diluted crude oil as substrate and electron donor. Based on this study, we investigate the production of sulfide when all the nitrate was reduced in condition with multiple nitrate addition, followed by decrease of nitrate-reduction. Moreover, based on quantification of functional gene analysis, which are: 16SrRNA (total bacteria) and dsrA (dissimilatory sulfate reduction in SRB), showed there were no significant difference between all conditions compared to control (without nitrate). Thus, the nitrate addition methods applied, single and multiple times, were not effectively eliminate SRB from the bacteria community. Some of the SRB was still remain in the bacteria community and potentially caused subsequent SRB outbreaks after nitrate become limited in environment.