Analysis of Methane-Hydrate-Bearing Formation using WeIl Logging and VSP Data in the MITI Nankai-Trough Wells, Japan
Y. Sanada, T. Takayama, M. Nishi, H. Yamamoto, S. Matsuda and T. Uchida
Event name: The 8th International Symposium on Recent Advances in Exploration Geophysics (RAEG 2004)
Session: Borehole Geophysics
Publication date: 10 March 2004
Info: Extended abstract, PDF ( 383.94Kb )
In this project, logging data showed P-wave low-velocity layers below bottom edge of methane-hydrate-bearing formation. Sonic log (DSI) couldn't acquire accurate compressional velocity in this zone, thus accurate correlation couldn't be taken between logging, VSP and surface seismic map. Small amount of gas concentration was presumed to cause difficulty of getting P-wave low-velocity. VSP interval velocity was used to compensate this low-velocity layer, and it showed slower value than mud velocity. Synthetic seismogram was created by VSP-compensated velocity to compare against corridor stack of VSP. As a result, the depths above and below methane-hydrate-bearing formation were correlated well with Synthetic seismogram and reflectivity events of VSP. By using this correlation technique, distribution of methane-hydrate-bearing formation can be estimated well.