SURVIVAL MECHANISMS OF HYDROGEN SULFIDE-PRODUCING BACTERIA ISOLATED FROM EXTREME ENVIRONMENTS AND THEIR ROLE IN CORROSION

The presence of thermophilic sulphate-reducing bacteria (tSRB) has bee n demonstrated in all accessible zones of water injection and oil prod uction al eas of three facilities in the North Sea and from open sea s ituations. We consider that this widespread occurrence indicates an in digenous population of tSRB within oil-bearing formations. The impact of the oil recovery industry on formations, in particular the use of s econdary waterflooding of reservoirs, has caused unprecedented fluid m ovement within these deep subsurface zones. The microflora, disturbed by these processes, is likely to be forced into a cyclic rotation from formation, through production facilities and back into the formations after an unspecified residence time in North Sea waters. Representati ve cultures of tSRBs recovered from the oil facilities have been shown to be able to survive simulated environmental fluctuations such as th ose imposed by existence in and passage through formations and prolong ed exposure to cold seawater conditions. Results presented here indica te that tSRB are highly opportunistic bacteria, able to respond rapidl y to change and most importantly, able to attach to metal surfaces eve n when in a state of very low metabolic activity.