Seismic investigation of natural methane hydrate deposits

Abstract

The world’s continental margins are home to the very high pressures and low temperatures where methane combines with water to form the ice‐like methane hydrate. Only in the last couple of decades has it been discovered that methane hydrate is distributed over virtually every continental margin, as well as Arctic and Antarctic regions, and as such, may play a significant role as a future energy source, an agent of global climate change, or a factor in marine slope stability. Because the acoustic impedance of gas phase methane is significantly less than sediment, water, or methane hydrate, the phase boundary between gas and gas hydrate is frequently quite strong, and easily discernible in seismic sections. Further, because pressure variations in this part of the seafloor are typically small, the phase boundary can be used to determine sediment temperature. In certain circumstances, lateral variations in the depth to this phase boundary can be used to constrain the flux of heat, pore‐water, and methane responsible for concentrated methane hydrate deposits and chemosynthetic communities found at seafloor seeps.