Geological setting and characterization of a methane hydrate reservoir distributed at the first offshore production test site on the Daini-Atsumi Knoll in the eastern Nankai Trough, Japan

摘要: Abstract To obtain basic information for methane hydrate (MH) reservoir characterization at the first offshore production test site (AT1) located on northwestern slope of Daini-Atsumi Knoll in eastern Nankai Trough, extensive geophysical logging and pressure coring using a hybrid system were conducted 2012 monitoring well (AT1-MC) (AT1-C). The MH-concentrated zone (MHCZ), which was confirmed by AT1-MC, has 60-m-thick turbidite assemblage with sublayers ranging from few tens to hundreds centimeters thickness. is composed lobe/sheet-type sequences upper part relatively thick channel-sand lower part. Well-to-well correlations sandy layers between two wells within 40 m one another exhibited fairly good lateral continuity sand reservoir. This suggests an ideal test. validity MH pore saturation (Sh) evaluated data comparing those core analysis. In MHCZ, Sh values estimated resistivity logs showed distinct differences mud layers, compared nuclear magnetic resonance (NMR) logs. Resistivity have higher vertical resolution than NMR logs; therefore, they are favorable these types thin-bed evaluations. part, 50%–80% observed agreement core-derived values. both background smoother curves also