Resources assessment of methane hydrates offshore Japan

Abstract:

JOGMEC, as a member of research group for resources assessment of Research Consortium for Methane Hydrate Resources in Japan (MH21), is conducting resources assessment of methane hydrates (MHs) offshore surrounding Japan.

The interpretation of 3-D seismic data acquired by geophysical vessel ‘Shigen’, which is owned by Agency for Natural Resources and Energy, are carried out. And MH concentrated zones are being extracted.

This study is an introduction for the case example of interpretation of 3-D seismic data in the area which have not been drilled.

The characteristic of 3-D seismic data in this study area shows fold structure, which undulates severalfold. In addition, some faults are interpreted, which does not show the large displacement, are seen. Bottom Simulating Reflector (BSR) is very visible continuously. Clear velocity contrast in the boundary between above and below of BSR and the high velocity anomaly above BSR are confirmed in the high density velocity analysis profile. MHs are assumed to exist in sand heterogeneously because the velocity distribution in the extracted zones is inhomogeneous. In the results of geomorphological analysis, channel deposits and mid submarine fan deposits, which are located above BSR, are presumed the sediments which bear sand.

Thus the extracted zones are estimated MH concentrated zones.

As above, even the area has not been drilled, the extraction of MH concentrated zones can be estimated by the interpretation of the seismic data, the result of the high density velocity analysis, and the distribution of sand by geomorphological analysis. These results will be useful for the plan of the future drilling programme.

This introduction is the example of 3-D seismic survey area. It will become a useful information for 3-D seismic survey plan by performing similar interpretation in 2-D seismic survey lines.