The fate of gas migration paths in the gas hydrate-bearing sediments in the Sea of Okhotsk

Abstract

High-resolution seismic profiles show distinct chimney structures (hereafter gas chimney) imbedded in gas-hydrate-bearing sediments while hydroacoustic profiles capture ongoing methane-emission features into the water column in the Sea of Okhotsk. On the profiles, we identify two kinds of chimney structures through the gas hydrate-bearing sediments, which are interpreted as active and non-active migration paths of methane. We propose that during methane release, a wide gas chimney with enhanced reflection is formed along the path due to lateral saturation of gas into the surrounding permeable sedimentary layers, after stoppage of methane release the gas chimney becomes a narrow wipe-out gas-hydrate chimney filled with highly concentrated gas hydrate converted from enriched gases along the path.