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Elastic‐wave velocity in marine sediments with gas hydrates: Effective medium modeling
Author(s) -
Helgerud M. B.,
Dvorkin J.,
Nur A.,
Sakai A.,
Collett T.
Publication year - 1999
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl900421
Subject(s) - clathrate hydrate , porosity , elastic modulus , geology , hydrate , sediment , elasticity (physics) , mineralogy , thermodynamics , geotechnical engineering , chemistry , geomorphology , physics , organic chemistry
We offer a first‐principle‐based effective medium model for elastic‐wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions: (a) hydrate modifies the pore fluid elastic properties without affecting the frame; (b) hydrate becomes a component of the solid phase, modifying the elasticity of the frame. The goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain hydrate concentration estimates from assumption (b) consistent with estimates obtained from resistivity, chlorinity and evolved gas data.