Optimization of nonisothermal selective plugging with a thermally active biopolymer

Abstract

A novel concept of microbial enhanced oil recovery (MEOR) under nonisothermal conditions was developed based on temperature-dependent biokinetics. The model specified the use of temperature-triggered Dextran (a biopolymer) produced by Leuconostoc mesenteroides (a microbe). The effects of environmental temperature on microbial growth and biopolymer production were validated and calibrated using the cardinal temperature model and experimental results. Various biokinetic parameters and a permeability reduction factor were also obtained to within approximately 2% error of those previously reported sandpack experiment. Based on the developed nonisothermal biokinetic model and the permeability reduction factor, thermally active MEOR was analyzed for a high-temperature reservoir. The results suggested the influences of injection parameters, such as injected nutrient concentration, rate, and temperature, on oil recovery factor. Higher nutrient concentrations resulted in increased Dextran production, thereby increasing oil recovery by selective plugging. On the other hand, injection rate and temperature were related to Dextran distributions. Higher injection rates led to lower Dextran concentrations with wider distributions. The injection temperature controlled the location of trapped Dextran in porous media, thereby influencing oil recovery. Through the optimization process, the injection design was determined with a rate of 30 m(3).day(-1), temperature of 5 degrees C, and nutrient mole fraction of 0.009. The suggested optimal injection design resulted in the largest oil recovery (39%) for a highly heterogeneous layered reservoir.