INPEX Corporation, Tokyo University and Natural Institute of Advanced Industrial Science and Technology (AIST) have been working since 2008 to study methane-producing technology using microbes inhabiting depleted oil and gas fifields. The concept and mechanism of microbial methane conversion are depicted as follows. First, inhabiting bacteria prompt to produce acetic acid or hydrogen from residual petroleum components in the underground reservoir. Next, methane-producing microbes (methanogens) are concerned in generating methane from the produced acetic acid, hydrogen and carbon dioxide injected for geological sequestration as CCS operation.
A wide variety of hydrogen- and methane-producing microbes have been discovered in (depleted) oil fields. We found that microbes indigenous to the reservoir brine could produce methane probably by using crude oil as a carbon source in the presence of CO2 (10 mol%).
Kinetics of gas (methane, carbon dioxide) production and consumption of acetic acid indicated that there are two reaction pathways from oil to methane; the acetoclastic methane producing pathway and the hydrogentrophic methane producing pathway.
Furthermore, from the result of methane producing experiments and Carbon isotope tracer test, the existence of syntrophic cooperation between hydrogen producing bacteria and methane producing archaea is also identified.
We are currently evaluating the way to enhance the capability of methane-producing microbes and developing an effective and efficient process for methane production in the actual reservoir condition.
Our results will lead to establish a new MEOR system that converts residual oil in depleted oil fields into environmentally friendly methane efficiently.
