September 2002 - March 2004
Understanding the Distribution of Gas Hydrates At and Beneath the Seafloor
Alexei Milkov is studying the distribution and significance of gas hydrate. Gas hydrate is a mineral composed of water and natural gases (mainly methane) that occurs in polar regions and in oceanic, sea, and lake sediments at water depth greater than ~200-600 m, depending on seafloor temperature and gas composition. Samples of gas hydrate have been recovered from 22 localities worldwide, and gas hydrate occurrence is hypothesized in 77 localities based on geophysical, geochemical, and geological evidence.
The global gas hydrate reservoir may contain as much as 10,000 Gt of methane, although this estimate is highly uncertain. Because so much methane may be concentrated in gas hydrate, this mineral is considered as a potential energy resource and an important component in the global organic carbon cycle. Moreover, gas hydrate significantly changes the physical properties of sediments when it crystallizes or decomposes, and thus is a subject of geohazard studies.
Alexei has studied gas hydrate in Western Siberia, the Norwegian Sea, and the Gulf of Mexico. The focus of his current research is Hydrate Ridge, a 25-km-long and 15-km-wide accretionary ridge on the Oregon continental margin composed of silty and sandy turbidities. Hydrate Ridge was extensively drilled on the Ocean Drilling Program (ODP) Leg 204. Alexei uses the results of direct in situ methane measurements he made during the Leg to constrain the distribution of gas hydrate in sediments and to estimate the volume of hydrate-bound gas at Hydrate Ridge. He also uses stable carbon and hydrogen isotopes of hydrocarbon gases to better constrain the origin of fluids that migrate within Hydrate Ridge and support concentrated gas hydrate accumulations near the seafloor. Alexei collaborates with George Claypool (USGS), Roger Sassen (Texas A&M University), Gerald Dickens (Rice University), Walter Borowski (Eastern Kentucky University), Jean Whelan (WHOI) and others.