A Study of Microbial Problems and Their Control in the Oilfield Waters

Microorganisms present in injection water or other oilfield water may cause corrosion or plugging of lines and reservoir formation rock. It should be pointed out that the mere presence of bacteria or other microorganisms in water does not necessarily mean that they present a problem. Elimination or reduction of bacteria is justified only if it represents an economical solution to a corrosion or plugging problem. This paper is an attempt to report the most important bacteria which grow in oilfield of Ahwaz (Iran), in order to control the action and their growth. Sulfate reducing bacteria (SRB) were the most important and damaging bacteria in this area. They cause corrosion, and the iron sulfide produced as a product of the corrosion reaction is an excellent,plugging material. The bacteria have been isolated from black deep sediments of a river in the neighbourhood of Ahwaz in which the sulfate concentration is high enough to promote the activity of SRB. The strains were first cultivated in anaerobic shakeflasks and progressively adapted to the culture contained carbohydrate and yeast extract as a model for primary experiment. The effect of the pH and temperature on the growth of bacteria under continuous cultivation show that the SRB grow under rather extreme conditions e.g. under pH ranging from 4 to 10, and temperature from 20 to 50°c.