Severe bacteria corroison was observed at dead ends in an oil field producing formation water with TDS higher than 250 g/l and pH around 6 - 6.5. SRB and TRB activities are supposed to be very low in such salty environment. Four water samples of 3 -4 cm3 each collected from the same dead end showed that the salinity of the stagnant water is one order of magnitude less (about 15 - 20 g/l) and the pH is as low as 4.5. More samples were collected and the changes of salinity and pH were confirmed. It was clear that production of acids /water by some bacteria created ideal conditions for SRB/ TRB development. In order to understand the mechanism and identify involved bacteria several water samples were collected from dead ends and sent to a well know laboraotry for identification of differente species. In the mean time the emchanisms of dead end corrosion were investigated.