Abstract: The microbial growth and metabolism in oilfields has been demonstrated to result in the production of hydrogen sulfide (H₂S), inducing a range of production and environmental challenges, including souring and corrosion. However, available biocides pose risks to environmental safety and resistance development. To explore eco-friendly antibacterial strategies, the inhibitory effects of ethanol extracts from six Chinese medicinal plants (Artemisia argyi, Berberis julianae, Lactuca sativa, Linum usitatissimum, Artemisia capillaris, and Xanthium strumarium) were evaluated against multiple H₂S-producing bacterial species isolated from oilfield settings. Furthermore, the combined effects of B. julianae and A. argyi extract with nitrite were investigated. Results showed that A. argyi extract and B. julianae extract, at an initial concentration of 5 mg·mL^-1, completely suppressed the H₂S- production activity of Thermoanaerobacter mathranii strain S1, Tepidimicrobium ferriphilum strain F1, and Moorella glycerini strain A24 within a 15-day period. In contrast, other extracts showed no effects on all the strains. The combination of B. julianae extract or A. argyi extract with nitrite produced a synergistic inhibitory effect on strains S1, A24, and F1. These combinations resulted in a more than 70% reduction in the required extract doses when compared with the use of individual agents. The utilization of A. argyi and B. julianae extract, either individually or in conjunction with nitrite, possesses the potential for environmentally sustainable microbial souring control in oilfield operations.

Key words: sulfide hydrogen-producing bacteria, Chinese medicine extract, biocide, oilfield, microbial souring