Sulfide removal in reservoir brine by indigenous bacteria

A field test was performed at the Coleville field to evaluate the ability of indigenous bacteria to remove sulfides from reservoir brine. Ammonium nitrate and sodium phosphate were injected continuously at two injectors for nearly 50 days. Sulfide levels at the two injectors declined by 42 to 100% and by as much as 50 to 60% at two adjacent producers. Concentrations of indigenous sulfide oxidizing, nitrate-reducing bacteria increased at injectors and producers while concentrations of sulfate-reducing bacteria remained unchanged or decreased slightly. Stimulation of indigenous beneficial bacteria has potential application as a cost-effective, low toxicity means to remove and control sulfides in reservoir brines.