Abstract: The issue of microbial-induced hydrogen sulfide (H₂S) in oilfields, also known as microbial souring, exerts deleterious effects on oilfield development, including safety concerns and corrosion. Nevertheless, research endeavors are critically needed to understand the physiological characteristics and control strategies of the microorganisms responsible for H₂S production. We employed the roll tube technique to isolate and screen the hydrogen sulfide-producing bacteria from the production water of an offshore souring high-temperature oil well. We examined the physiological and biochemical characteristics of the high-efficient strain and the inhibitory effects of several biocides on the activity of H₂S production. The results showed that the high-efficient hydrogen sulfide-producing bacterial strain A17 shared 99% similarity of 16S rRNA gene sequence with the type strain DSM9442 of Pseudothermotoga elfii. The cells of A17 were short rods, with a length of 2.2 μm, and motile. The optimal growth condition was at 65 ℃, pH 7.0, and a salinity of 1%, respectively. Strain A17 could utilize a diverse range of carbon sources, including sodium lactate, glucose, and sodium acetate. Strain A17 utilized thiosulfate as electron acceptor, instead of sulfate, sulfite, nitrate, and or nitrite. The amendment of glutaraldehyde (at a final concentration of 200 mg·L^-1), tetrakis (hydroxymethyl) phosphonium sulfate (200 mg·L^-1), bronopol (40 mg·L^-1) or nitrite (20 mg·L^-1) alone resulted in the complete inhibition of H₂S-producing activity of A17 within the 30-day incubation. Strain A17 is a thermophilic H₂S-producing bacterium that differs from the sulfate-reducing bacteria frequently observed in oilfield habitats. The potential contribution of “non-sulfate-reducing bacteria”, as represented by A17, to the secondary H₂S in oilfields merits further investigation. Our findings contribute to the understanding of souring-causing microorganisms in high-temperature oilfields. The A17 strain could be used for the research and development of mitigation strategies in the study region.

Key words: offshore oilfield, sulfide-producing bacteria, biocide, souring, sulfate-reducing bacteria