Bacterial community dynamics during MEOR biostimulation of an oil reservoir in sumatera Indonesia

Abstract

Biostimulation is a method of microbial enhanced oil recovery (MEOR) by injecting nutrients into an oil well to stimulate the growth of indigenous bacteria and their activities dealing with the increasing of oil recovery. This study aimed to obtain an optimum nutrient formulation at laboratory scale to be applied for MEOR field biostimulation pilot project. Field monitoring of chemical and bacterial composition in oil well was also carried out up to twelve weeks after biostimulation. The oil composition was analyzed by GC-MS and column chromatography. Bacterial community analysis was performed using 16S rRNA gene as the biomarker, which was sequenced by Illumina Miseq Sequencing. Based on Response Surface Methodology (RSM), the optimum nutrient concentrations that increase bacterial growth and decrease oil viscosity were molasses 5% (w/v), NPK 0.5% (w/v), and DAP 0.5% (w/v). The relative abundance of the bacteria and the community composition constantly changed during the monitoring process. Injection of molasses stimulated the growth of the hydrocarbonoclastic bacteria until the end of monitoring period. • Higher nutrient concentrations does not always stimulate the indigenous bacteria. • During the MEOR monitoring process, saturated and resinic fractions increased. • SRB growth was successfully suppressed by biostimulation treatment. • Biostimulation rise the bacterial community to a significantly different and more diverse species.