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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 479

Last Page: 479

Title: SAMPLE--Seismic Amplitude Measurement for Primary Lithology Estimation: ABSTRACT

Author(s): Gary S. Gassaway, H. J. Richgels


SAMPLE is a method of seismic interpretation that extracts shear Previous HitwaveNext Hit velocities or Poisson's ratios from the seldom used amplitude variations within a common-depth-point (CDP) gather. From a crossplot of pressure Previous HitwaveNext Hit velocity and Poisson's ratio, lithologies and pore fluids are then estimated.

The SAMPLE method works because reflection and transmission of elastic waves (seismic waves) at the boundary between two media are a function of 6 parameters. Three elastic parameters in each media are P-Previous HitwaveNext Hit velocity, Poisson's ratio or S-Previous HitwaveNext Hit velocity, and density. Given these 6 parameters and the angle of incidence of a plane elastic Previous HitwaveNext Hit, the reflection and transmission amplitudes (coefficients) can be calculated using Zoeppritz's equations. SAMPLE is an inversion of this calculation. P-Previous HitwaveNext Hit velocity is determined in a conventional manner (i.e., Dix interval velocities). Density is assumed to be a function of P-Previous HitwaveNext Hit velocity. The unknown Poisson's ratios can be determined from the reflection amplitude variation with angle of incidence (offset versus amplitude variations within a C P gather.)

Having solved for P-Previous HitwaveTop velocities and Poisson's ratios, lithologies and fluids are estimated.

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Copyright 1997 American Association of Petroleum Geologists