Geophysical Investigation of Gas Hydrate-Bearing Sediments in the Sea of Okhotsk

Abstract

As the sea connecting with the East Sea, the Sea of Okhotsk is the most potential area of gas hydrates in the world. In other to examine geophysical structures of gas hydrate-bearing sediments in the Sea of Okhotsk, the CHAOS (hydro-Carbon Hydrate Acumulation in the Okhotsk) international research expedition was carried out in August 2003. In the expedition, high-resolution seismic and geochemicalsurvey was also conducted. Sparker seismic profiles show only diffusive high-amplitude reflections withoutsobtained using different frequencies. Many gas chimneys rise up from BSR depth to seaflor. The chimneys can be divided into two groups with different seismic characteristics;wipe-out (WO) and enhanced reflection (ER) chimneys. Different seismic responses in the chimneys would be caused by amount of gas and gas hydrates filing in the chimneys. In hydroacoustic data, a lot of gas flares rise up several hundreds meters from seaflor to the water column. Al flares tok placed at the depthswithin gas hydrate stability zone. It is interpreted that gas hydrate-bearing sediments with low porosityin which gas is migrating up without los of amount. Therefore, large-scale gas flare at the site on gas chimney releases into the water column.