Identification, characterization and application of sulfide- oxidizing bacteria in oil fields

The cycling of sulfur in oil field brines has focused predominantly on bacteria involved in the reduction of sulfur species to sulfides, which are detrimental to the production of these fields. However, recent interest in the addition of nitrates and nitrites to oil field brines for the remediation and control of sulfides has rekindled new interest in sulfide bio-oxidation. Addition of nitrate and phosphates to produced brine from an oil field in Western Canada resulted in the stoichiometric conversion of sulfide to elemental sulfur and nitrate to nitrogen gas. Isolation and characterization of sulfide-oxidizers from this brine revealed the presence of two novel, autotrophic, colorless sulfur bacteria. Culture techniques and reverse sample genome probing were applied to field brines to confirm the identity and role of one of these isolates during a field test. The results suggest that sulfide-oxidizers exist in oil field brines that can be selectively activated in situ through the addition of limiting nutrients. However, similar tests applied to oil field brines from West Texas (WT) suggested that heterotrophic sulfide-oxidizers might play a more predominant role in sulfide oxidation in these habitats.