Abstract:Oil reservoirs are often deep subsurface extreme environments with high temperatures, pressures, and salinities. Several physiological and taxonomic groups of thermophilic anaerobic bacteria are present in the oil reservoirs, such as fermentative, methanogenic, sulfate-reducing and Fe(III)-reducing microorganisms. A total of 90 strains of Fe(III)-reducing bacteria have been isolated from oilfield fluids and identified as the genus Thermotoga, Thermoanaerobacter, Deferribacteres, the order Desulfuromonadales within the class Deltaproteobacteria, the order Shewanella within the class Gammaproteobacteria, and Thermococcus within the Euryarchaeota, in the growth temperature range of 4?85 °C and the growth salinity range of 0.1%?10% NaCl. The growth pressure range of Fe(III)-reducing microorganisms in oil reservoirs has not been reported yet. There is strong interaction among the microorganisms, minerals and fluids (oil/water) at the actual reservoir conditions. The clay minerals can serve as carriers for microbial life activities and also provide electron acceptors for microbial metabolism. Here, we present the current status of isolation and characterization of Fe(III)-reducing bacteria in oil reservoirs, describe the environmental applicability of Fe(III)-reducing bacteria, and predict microbial enhanced oil recovery (MEOR) application prospects by using Fe(III)-reducing bacteria.
