Field Tests of Sulfide Removing Biologically in Surface Systems

Abstract Biogenic sulfide is really troublesome in many produced water associated surface systems. The problems include iron sulfide (FeS) pluggings (equipment and near-borehole formation), excess solids, emulsion, and H2S related corrosion, toxicity, and reservoir souring as well. Cost effectively mitigating the serial problems is quite challenge and very costly because sulfide related problems often occur in produced water treatment systems, oily sludge system, injection system and extent to reservoir. Waterflooded reservoirs can offer conditions for growth of the sulfate reducing bacteria (SRB) that would convert sulfate to sulfide constantly, and polymer and chemical tertiary recovery implementation contributes sulfide in the reservoir as well. In recent years, many surface facilities including three-phase separators, produced water treatment stations, oily sludge systems and injection systems in Daqing oilfield not only have server the sulfide problems, but also cause electric dehydrator systems power-off because of the high conductivity FeS layer forming, which resulted of FeS emulsified with skimmed oil returning to the dehydrator systems. As a result, normal operation has been disrupted constantly and safety has been a major concern as well in those facilities. In this paper, we present test results from three fields using the microbial technique for sulfide removing in the produced water and oily sludge, and how we did it to achieve better results in a very cost-effective manner. By applying this microbial sulfide removal technique efficiently prevents floating/skimmed and sludge oil aging in gathering systems, and improved produced water treatment efficiency and reduced the facility corrosion for the entire oil produced fluid treatment plants. In other word, the proposed application technique can effectively put sulfide related problems under control not only in isolated facilities and short term, but also in the entire system and long term.