About This Item

Share This Item

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 wave velocities or Poisson's ratios from the seldom used amplitude variations within a common-depth-point (CDP) gather. From a crossplot of pressure wave velocity and Poisson's ratio, lithologies and pore fluids are then estimated.

The SAMPLE method works because Previous HitreflectionNext Hit and Previous HittransmissionNext Hit 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-wave velocity, Poisson's ratio or S-wave velocity, and density. Given these 6 parameters and the angle of incidence of a plane elastic wave, the Previous HitreflectionNext Hit and Previous HittransmissionNext Hit amplitudes (Previous HitcoefficientsNext Hit) can be calculated using Zoeppritz's equations. SAMPLE is an inversion of this calculation. P-wave velocity is determined in a conventional manner (i.e., Dix interval velocities). Density is assumed to be a function of P-wave velocity. The unknown Poisson's ratios can be determined from the Previous HitreflectionTop amplitude variation with angle of incidence (offset versus amplitude variations within a C P gather.)

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

End_of_Article - Last_Page 479------------

Copyright 1997 American Association of Petroleum Geologists