Compressional and Shear Wave Velocities in Uncemented Sediment Containing Gas Hydrate

YUN T.S., FRANCISCA F. M., SANTAMARINA J. C., RUPPEL C.

GEOPHYSICAL RESEARCH LETTERS

American Geophysical Union

Año: 2005 vol. 32 p. 1 - 5

0094-8276

The competing hypotheses for gas hydrate formation at the particle scale in sediments describe processes of porefilling, frame-building, or cementation. New measurements of compressional (VP) and shear wave (VS) velocities in fine-grained sands subjected to low confinement and monitored during formation of  tetrahydrofuran hydrate indicate that hydrate nucleates in the pore space (presumably at grain boundaries) and grows with limited impact on the sediment shear stiffness, VP, and VS until crystals begin to interact with the granular skeleton at 40% hydrate concentration. VS increases significantly more than VP at higher hydrate concentrations, reflecting larger changes in the specimen’s shear stiffness than its bulk stiffness. The results indicate that seismic velocities and/or their ratio (VP/VS) have limited capability for locating hydrate or constraining hydrate concentrations.