Simultaneous Inversion of Pre-Stack Seismic Data for Fluid and Lithology Prediction

Bankhead, Bradley L. ¹ (1) VeritasDGC, Houston, TX

We have developed a new approach to the simultaneous inversion of pre-stack seismic data which produces estimates of P-impedance, S-Impedance and density. The method is based on three assumptions: that the linearized approximation for reflectivity holds, that PP and PS reflectivity as a function of angle can be given by the Aki- Richards equations, and that there is a linear relationship between the logarithm of P-impedance and both S-impedance and density. The use of petrophysical constraints together with multi-angle wavelet analysis provides a more robust solution for rock property extraction through a coupling of Vp and Vs, as well as Vp to density.

This approach has proven beneficial to the exploration efforts in the Rockies through the discrimination of sands and shales. This is accomplished by combining multiple inversion volumes such as P-impedance, density, and the Vp/Vs ratio to estimate V-clay. The process is guided by a detailed rock properties study of the existing log data making use of multi-well trend plots and crossplots of the different elastic properties. 

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana