Synergistic approach to control reservoir souring in the moderately thermophilic oil fields of western India

Abstract Souring, the increase in sulfide concentration in production fluid, exists in the moderately high temperature oil fields of western India located in state of Rajasthan. The source water for oil production is taken from an underground aquifer that has high salinity and sulfate concentration. The reduction of this sulfate to sulfide was initiated above-ground when this source water was mixed with produced water. Current research revealed that high temperature (55 °C) and low salinity are the factors that influence souring in these fields. It was observed that the microbial community of the produced water has a significant proportion of thermophilic SRB and the active sulfate reduction takes place only after produced water was mixed with source water for reinjection. To stop sulfate reduction at these sites, six combinations of biocides and metabolic inhibitors were screened. Out of these combinations, nitrate and benzalkonium chloride (BAC) showed a maximum synergistic inhibitory effect on SRB growth.