Sulfate-reducing bacteria (SRB) are those bacteria and archaea that can obtain energy by oxidizing organic compounds while reducing sulfate (SO42-) to hydrogen sulfide (H2S).In a sense, these organisms "breathe" sulfate rather than oxygen by anaerobic respiration.
Sulfate-reducing bacteria can be traced back to 3.5 billion years ago and are considered to be among the oldest forms of microorganisms on Earth. Species of SRB’s can tolerate temperatures exceeding 90°C and more than 100 bar pressure.
The main nutrients for SRB are simple organic acids and molecular hydrogen (H2) from decomposing natural organic matter. The nutrients are oxidized, with sulfate being reduced to sulfide (hydrogen sulfide, H2S). The formed is the principal agent in the disastrous effects caused by SRB. It contaminates gas and stored oil, precipitates ferrous sulfide that plugs injection wells, and promotes precipitates ferrous sulfide that plugs injection wells, and it is one of the main causes of Microbiologically Influenced Corrosion (MIC)
Good control of SRB will avoid the formation of H2S and extend the operational life of the system and greatly reduce the incidence of microbiological problems.
Hydrogen sulfide (H2S) is a naturally occurring gas contained in many of the world’s crude oils. It is also formed in the refining process by the degradation of sulfur-containing compounds in crude at high temperatures.The average sulfur content of crude oils being processed in the world’s petroleum refineries continues to increase.
Refineries and storage facilities, such as tank farms, are likely to encounter problems specific to the handling of crude oils, intermediates and refined products that contain or generate H2S.
Heavy oils, including crude oil, residual fuel and gas oil, tend to have large concentrations of H2S. This becomes a concern if these products are to be stored for an extended time or during transport.
While safety remains the primary concern when dealing with H2S, other H2S-related issues can create additional challenges for these facilities.