Optimization of Microbial Enhanced Oil Recovery with Temperature-Triggered Biosurfactant and Biopolymer

Abstract

Through the understanding of temperature-dependent biokinetics, this study proposed a novel concept of temperature-triggered MEOR under nonisothermal conditions. The suggested concept characterized the stoichiometric reactions of microbial growth with bioproduct generation and was validated against the experimental results for Bacillus subtilis (biosurfactant-producing microbe) and Leuconostoc mesenteroids (biopolymer-producing microbe). Based on these stoichiometric reactions, temperature effect of microbial growth rate was formulated. Coupled biokinetic and nonisothermal model was examined to validate the efficiency of temperature-triggered MEOR at high-temperature reservoir. Bacillus subtilis improves wettability, while Leuconostoc mesenteroids (L. mesenteroids) improves sweep efficiency. Throughout the adjustment of injection parameters (nutrient concentration, rate, and temperature), overall performances of temperature-triggered MEOR were investigated in high-temperature reservoir. Higher sucrose concentration and lower temperature represented positive effects on oil recovery. Optimal injection rate was identified because it depends on not only heat transfer but bioprodoucts distributions. Optimization process was also accomplished to derive design parameters maximizing oil recovery. In wettability alteration mechanism of Bacillus subtilis, oil recovery was improved up to 52% compared to waterflooding (45%). Selective plugging mechanism of L. mesenteroids also achieved maximum oil recovery of 37.9%, which was comparable to waterflooding (28.9%). The results showed a promising potential of temperature-triggered MEOR in high-temperature reservoir.