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 been demonstrated in all accessible zones of water injection and oil production al eas of three facilities in the North Sea and from open sea situations. We consider that this widespread occurrence indicates an indigenous population of tSRB within oil-bearing formations. The impact of the oil recovery industry on formations, in particular the use of secondary waterflooding of reservoirs, has caused unprecedented fluid movement 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. Representative cultures of tSRBs recovered from the oil facilities have been shown to be able to survive simulated environmental fluctuations such as those imposed by existence in and passage through formations and prolonged exposure to cold seawater conditions. Results presented here indicate that tSRB are highly opportunistic bacteria, able to respond rapidly to change and most importantly, able to attach to metal surfaces even when in a state of very low metabolic activity.