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ABSTRACT: Relation of Physical and Seismic Properties of Gulf Coast Shale Intervals

T. K. Kan, R. M. Slatt

Three shale-prone Gulf Coast wells have been divided into different shale stratigraphic intervals on the basis of depositional environment,

qualitative grain size and sand/shale interbeddedness, and mineral composition. Each interval exhibits unique frequency distributions of log-derived bulk density and sonic velocity, which are related to shale type, compaction state (geopressuring), and diagenesis. Highly interbedded sand/shale intervals exhibit wider distributions of these physical properties than do less interbedded shaly intervals. Shale diagenesis tends to increase bulk densities and, in some instances, to reduce sonic velocities.

Statistical frequency distributions of reflection coefficients and synthetic seismogram attributes, as well as the character of AGC and RAP seismic sections are similarly related to the type of shale stratigraphic intervals. Highly interbedded sand/shale intervals exhibit a wider range of reflection coefficients, relative amplitudes (synthetic trace), and a higher proportion of reflectors (seismic trace) than do more uniform shaly intervals.

Establishing the relationships for a larger number of wells for which good lithologic, log, and seismic data are available can provide a reference set of seismic characteristics for routinely predicting the physical characteristic of a stratigraphic interval from seismic data alone.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990