Damian T. Herrick1,
Wences Gouveia2,
Lincoln F. Pratson1
(1) Duke University, Durham, NC
(2) Mobil Technology Company, Dallas, TX
Abstract: Building a lithology-based elastic
model from digitized
photographs of stratigraphy
A stratigraphic simulation in a
new form of experimental basin captures the stratal architecture of many basins
of exploration interest. To explore the seismic response of this stratigraphy,
physical property models are constructed from digital photographs of
experimental stratigraphy. Clay content values are assigned to the stratigraphy
based on the 8-bit grayscale value of each pixel in the digital photos. These
are then used to construct models of porosity, bulk density, compressional- and
shear-wave velocities, impedance, and reflectivity. Porosity and density are
modeled based on the Marion et. al. (1992) branched model. Compaction is also
accounted for via an exponential fit to laboratory measurements available in
Marion’s paper. Dry frame elastic
moduli are calculated using either the Xu and
White (1995) or the Berryman (1992) model. Gassmann’s equations are used to
simulate the effect of fluid saturation on the
elastic
moduli. Currently, brine
is used as the pore-filling fluid, but the fluid substitution method allows us
to place any fluid (brine, fresh water, oil, or gas) in the pore spaces. When
combined with the large-scale model of structure and stratigraphy in the
photographs, the physical models allow us to generate synthetic seismic data.
Planned future work includes an examination of the seismic response to varying
length scales and source frequencies, the effect of cable positioning error on
interpretation, an implementation of time-lapse seismics, and an assessment of
the performance of seismic inversion algorithms using the synthetic seismic
response as a test bed.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana