Minshull, T.A. and Chand, S.
The microstructure of sediment-hosted hydrates: evidence from effective medium modelling of laboratory and borehole seismic data.
Long, D., Lovell, M. A., Rees, J.G. and Rochelle, C.A. (eds.)
Sediment-Hosted Gas Hydrates.
Geological Society of London.
(Geological Society of London Special Publication 319).
Much of our knowledge of hydrate distribution in the subsurface comes from
interpretations of remote seismic measurements. A key step in such interpretations is
an effective medium theory that relates the seismic properties of a given sediment to
its hydrate content. A variety of such theories have been developed; these theories
generally give similar results if the same assumptions are made about the extent to
which hydrate contributes to the load-bearing sediment frame. We have further
developed and modified one such theory, the self-consistent
approximation/differential effective medium approach, to incorporate additional
empirical parameters describing the extent to which both the sediment matrix material
(clay or quartz) and the hydrate are load-bearing. We find that a single choice of
these parameters allows us to match well both P and S wave velocity measurements
from both laboratory and in situ datasets, and that the inferred proportion of hydrate
that is load-bearing varies approximately linearly with hydrate saturation. This
proportion appears to decrease with increasing hydrate saturation for gas-rich
laboratory environments, but increase with hydrate saturation when hydrate is formed
from solution and for an in situ example.
Actions (login required)