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