Ch. R-16 Microbial Ecology of Corrosion and Reservoir Souring

Abstract

Publisher Summary This chapter describes the microbial ecology of produced oil field fluids, and their role in corrosion and reservoir souring process. An oil reservoir consists of a rock matrix containing mixtures of liquid and gaseous hydrocarbons. Two important parameters, which determine the susceptibility of a reservoir to microbial penetration are the porosity and permeability of the rock matrix and the temperature of the reservoir. The other physical parameters, such as pressure and salinity, while influencing the types of bacteria which will be found, are considered to be secondary controlling physical factors relative to porosity, permeability and temperature. Relatively large numbers of aerobic, facultative and anaerobic bacteria are frequently found in fluids produced from oil fields undergoing water-flooding techniques. Electrochemical studies show that iron-reducing isolates accelerate the anodic reaction of the electrochemical cell, whereas the sulfate reducing bacteria act by cathodic depolarization. Thus, considerable data is present, which supports an active role for the iron-reducing bacteria in the corrosion process via: the removal of protective ferric oxide coatings on steel; the production of both sulfide and ferrous ions which will combine to produce corrosive ferrous sulfide; and possibly depolarization by the removal of proton and/or electron envelopes by their hydrogenase activity.