Unlocking the potential of bacterial consortia from oilfield wastewater for enhanced heavy oil recovery by efficient biodegradation and biosurfactant production

Microbial techniques are increasingly used in the extraction of heavy oil from reservoirs. The use of consortia containing heavy oil-degrading and biosurfactant-producing bacteria is a promising strategy for microbial enhanced oil recovery (MEOR), which can provide higher efficiency and robustness over single strains. The aim of this study was to construct bacterial consortia for enhanced heavy oil recovery with strains isolated from oilfield wastewater. Three strains with strong abilities to degrade petroleum hydrocarbons and produce biosurfactants were obtained. They were identified as Bacillus paraclicheniformis (W1), Microbacterium barkeri (W2), and Bacillus halotolerans (W3) based on morphological analysis and 16S ribosomal gene sequencing. Four heavy oil-degrading consortia were developed using three strains. Among them, W12, W13, and W123 performed well in heavy oil biodegradation (34.2–40.2 %). Heavy oil treatment with these three bacterial consortia led to transformation and redistribution of major fractions by increasing the saturate content and reducing the aromatic, resin, and asphaltene contents. Gas chromatography-mass spectrometry evidenced the degradation of saturates (C₂₀–C₂₉ n-alkanes) by 42.3 % (W12), 19.2 % (W13), and 40.9 % (W123). Inductively-coupled plasma mass spectrometry revealed prominent effects of W12, W13, and W123 on demetallization of Ni, Fe, and V, with maximum removal rates of 54.0 %, 90.7 %, and 51.0 %, respectively. The viscosity of heavy oil was decreased by up to 43.6 % after 30 days of bacterial treatment. Our results unlock the potential of bacterial consortia containing Bacillus and Microbacterium strains as oil degraders and displacement agents for use in enhanced heavy oil recovery.