抄録
Microbial EOR (MEOR) is generally understood as one of other EOR techniques although its high potential has been shown through numerous investigations for almost 90 years. The author concludes that the following three challenges should be needed to develop MEOR to a practical EOR.
· Screening for potential microorganisms that can grow under reservoir conditions such as high temperature and high salinity
· Development of commercial MEOR simulator
· Developing real-time sensing system to monitor the target microorganism in reservoir
The author has isolated successfully a thermophilic anaerobe that can degrade long-chain hydrocarbon of crude oil selectively and reduce oil viscosity to 60 percent of its original viscosity after a few days' incubation. It can grow even under a temperature of 80°C and a salinity of 90 g/L. The potential of MEOR using this anaerobe was shown through core-flood experiments.
The author has developed a prototype numerical simulator for MEOR that consists of 5 compositions: degraded oil, undegraded oil, brine, oil-degrading anaerobe, and yeast extract. The growth of the anaerobe depends on the concentration of yeast extract, temperature, and salinity on this numerical model. According to the numerical experiments, growth of the anaerobe and reduction of oil viscosity were found only around the injection well because the anaerobe consumed whole yeast extract around there. Therefore, the recovery factor can be increased by increasing the amount of yeast extract injected.
The author is estimating a possibility of a novel real-time sensing system based on the flow cytometry in order to monitor the target microorganism in reservoir. A target microorganism could be found selectively in culture solution where the target and nontarget microorganisms mixedly exist using a commercial flow cytometer, therefore, the possibility of the sensing system based on the flow cytometry was shown.
