Microbe enhanced oil recovery (MEOR) uses microbe’s metabolism or metabolites in oil reservoirs to enhance oil recovery. The technique has advantages in high potential, low cost, easy to operate and environment friendly, especially suitable to the late stage of oil field exploration.
The principal of this technique is driving oil by bio-surfactants synthesized by microbes. The stable growth and metabolism of bio-surfactant producing microbes in oil reservoir is a key point for successful technique of organism oil recovery. However, most surfactant-producing microorganism reported is aerobic and anaerobic environment in the oil reservoir results in that air has to be poured into the reservoir to maintain the activity of the bacteria and thus increase the cost. Reported anaerobic bacteria had low activity and sensitive to inhibition by hydrogen sulfide.
Prof ZHANG Ying and her research group of Microbe Ecology and Technology has got some breakthrough in the techniques of microbial oil recovery:
1) To overcome the oxygen-limiting conditions in oil reservoir and to circumvent the complex regulation of rhamnolipid biosynthesis in Pseudomonas aeruginosa, an engineered strain Pseudomonas stutzeri Rhl was constructed for heterologous production of rhamnolipid under anaerobic conditions. The oil recovery was significantly (9.8%) increased under simulated anaerobic environment (Zhao et al., 2015a). A wild strain of P. aeruginosa SG was isolated from oil field in Xinjiang and the strain was used to construct a gene engeniired bacterium P. aeruginosa PoprAB. The ramnolipid production under anaerobic conditions was enhanced by 60.2% and the experimental oil recovery increased 9.2%. The work provides bacteria resources to enhance oil recovery.
2) Sulfate-reducing bacteria (SRB) in the anairobic environment in oil reservoir and produces H2S that inhiites theactivity of rhamnolipid producing bacteria, acidefies oil reservoir and corodes pipline. Inhibition of SRB, removal of H2S and production of rhamnolipid by recombinant Pseudomonas stutzeri Rhl were investigated. Strain Rhl can simultaneously remove S2− (>92%) and produce rhamnolipid (>136 mg/l) under S2− stress below 33.3 mg/l. Rhl reduced the SRB numbers from 109 to105 cells/ml, and the production of H2S was delayed and decreased to below 2 mg/l. Rhl also produced rhamnolipid and removed S2− under laboratory simulated oil reservoir conditions. High-throughput sequencing data demonstrated that addition of strain Rhl significantly changed the original microbial communities of oilfield production water and decreased the species and abundance of SRB. Bioaugmentation of strain Rhl in oilfield is promising for simultaneous control of SRB, removal of S2−and enhance oil recovery.
The work was supported by 863 project (2013AA064402) and project of cooperation with Daqing Oil Field Cooperation Limited.
