Bacillus subtilis‐based microbial enhanced oil recovery (MEOR) in polymer microfluidic chip

Abstract Microbial enhanced oil recovery (MEOR) is a tertiary oil recovery process that manipulates the microbial environment inside oil reservoirs to modify the physical/chemical properties of the reservoirs to enhance the oil recovery. Up to now, the detailed MEOR mechanism is still not entirely clear due to the multiple influence factors (e.g., pH, nutrients, temperature, porosity, and permeability) on microbial growth and reproduction, as well as the lack of understanding of microbial's influencing mechanism on the oil recovery process. In this study, a Bacillus subtilis ‐based MEOR process was conducted in a polymethyl methacrylate (PMMA)‐based microfluidic device to mimic the MEOR process in the reservoir. The porous microstructure based on real sandstone slice images was fabricated with laser ablation on a PMMA substrate. Two different MEOR approaches were conducted in the PMMA‐based microfluidics devices: the direct injection of displacing reagent (biosurfactant produced by bacteria) into the microfluidic chip for the oil recovery (ex‐situ), and the incubation of bacteria solution inside the chip followed with brine flooding (in‐situ). The result indicates the ex‐situ MEOR process with B. subtilis can reach a recovery rate of 38.56%, while the in‐situ MEOR process with B. subtilis reached a recovery rate of 40.27%. The proposed study provides a new tool for understanding the MEOR process, with advantages in visibility and accurate fluid control during the MEOR process.