Mapping Gas Hydrate using Electromagnetic Methods
IPGP - Îlot Cuvier
Séminaires Géosciences Marines
Scripps Institution of Oceanography
Gas hydrate is found globally on the continental shelves and is important as an unconventional hydrocarbon source, a hazard to drilling and seafloor infrastructure, a potential source of potent greenhouse gas, and a confounding resistor in the interpretation of conventional marine EM data. Yet, estimates of global hydrate volume vary by three orders of magnitude and identified recoverable reserves are rare, the reason being that it is difficult to image hydrate using seismic methods alone. However, gas hydrate is highly resistive and presents a good EM target at high saturations. Conventional controlled-source EM (CSEM) methods can be used to image hydrate, but is inefficient because seafloor receivers need to be closely spaced to achieve the appropriate resolution in the upper hundreds of meters of the seafloor. Several groups, including Scripps Institution of Oceanography, have developed towed CSEM systems designed to map hydrate in deep water, and such equipment is now being used commercially to image hydrate with a potential for methane production. In this lecture I will describe marine gas hydrate, laboratory studies of its electrical properties, and the equipment that we use to image it, with case studies from offshore California and the Gulf of Mexico.