In the methane hydrate research project by METI/MH21 consortium, some unconventional data analysis techniques are developed and various types of geophysical surveys have been carried out to estimate the distribution and characteristics of methane hydrate. In this paper, we describe the continuous velocity analysis technique, 2D multi-component seismic survey and 2D deep-towed seismic survey which could give promising results not only for methane hydrates but for conventional oil and gas exploration.
The continuous velocity analysis is applied to PSTM gather of 2D/3D seismic data in order to estimate the detailed velocity structure around methane hydrate bearing layer. Especially the high velocity anomaly above BSR is recognized as one of the indication which implies existence of methane hydrate concentrated zone. This velocity analysis technique has been applied for monitoring the oil-sand production with SAGD and it gave the successful results.
A 2D multi-component seismic survey was carried out using the RSCS in 2006. It is an ocean bottom cable system employing a series of 3-component geophones connected with submarine optical cable. The resulting PP reflection PSTM sections with the vertical component showed excellent agreement with the 3D survey migrated volume. The PS-converted wave sections with inline horizontal component showed amplitude anomalies around BSR. This fact indicates S-wave velocity anomaly and gives information to estimate the rock physics model.
A 2D deep-towed seismic survey was carried out in 1996. Both the source and the hydrophone cable are towed close to the seabed to obtain higher resolution section and velocity profiles compared with 3D marine seismic in the very shallow part. But, we can not recognize BSR clearly on the section because of its insufficient source energy. The high resolution section of the survey has great potential for finding active faults or hydrothermal deposits.