Diversity of Indigenous Anaerobes and Methane Conversion System from Reservoir Oil by Indigenous Anaerobes in Depleted Oil Fields

We developed methods and technology to identify oil and gas fields that are likely to support the restoration of methane deposits, and identified the main characteristics of microbes inhabiting depleted oil and gas fields. To evaluate the potential for microorganisms to inhabit oil and gas fields in Japan, we investigated the existence of methane-producing archaea (MPA) and hydrogen-producing bacteria (HPB) using PCR-DGGE (Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis) analysis. Reservoir brine from Yabase oil field (Akita Pref., Japan), which was incubated under strictly anaerobic conditions at 50 degrees C, actively produced methane, indicating that Yabase oil field is a suitable site for methane generation. Moreover, analysis of the enrichment culture revealed that it is possible for indigenous anaerobes inhabiting an oil field to generate methane from oil components. Additionally, findings established a methanogenic pathway composed of MPA such as Methanoculleus sp., Methanothermobacter thermoautotrophicus, and Methanosaeta sp. and hydrocarbon-degrading hydrogen-producing bacteria (HD-HPB) related to Thermotoga sp., Petrotoga sp. and Clostridiaceae str. These results strongly suggest that Yabase oil field has the technological potential for the microbial restoration of methane.