Skip to Main Content
Book Chapter

CALIBRATION OF SEISMIC RESPONSE FOR 3D-AVO ANALYSIS

By
JAMES DISIENA
JAMES DISIENA
Geophysical Development Corporation 8401 Westheimer, Suite 150 Houston, Texas 77063-2799
Search for other works by this author on:
FRED HILTERMAN
FRED HILTERMAN
Geophysical Development Corporation 8401 Westheimer, Suite 150 Houston, Texas 77063-2799
Search for other works by this author on:
CONNIE VANSCHUYVER
CONNIE VANSCHUYVER
Geophysical Development Corporation 8401 Westheimer, Suite 150 Houston, Texas 77063-2799
Search for other works by this author on:
Published:
December 01, 1996

ABSTRACT

In this Gulf of Mexico case study, extended Amplitude Versus Offset (AVO) analysis enables the generation of sand and gas reservoir maps not obtainable from conventional 3D data. This interpretation results from calibrating the 3D-AVO response to lithology and pore fluid variations, in particular:

  1. Analysis of well data provides lithology, velocity, and density control necessary to estimate Poisson’s ratio, as well as rock property variations from wet to gas filled conditions,

  2. AVO modeling based on these variations yields the anticipated seismic response, thereby linking the log properties to the 3D seismic data, and

  3. Processing to recover the AVO response from data with source-to-receiver offsets out to two times the target depth, enables lithologic mapping when supported by the above calibration.

The reservoir sands range from 6,000 to 13,000 ft depth, lying above and below geopressure. Conventional seismic analysis associates the amplitude of the reflections to the contrast in acoustic impedance, the product of velocity and density. On the log data, the target sands appear to have little contrast in acoustic impedance with their encasing shales. Because of this low contrast, the amplitudes on the seismic stack sections show little-to-no discrimination between sand-shale lithologic variations or pore fluid variations.

A two-term model for the seismic amplitude provides the basis for unraveling the complex AVO responses of lithologic variations and gas sands. The first term, the Normal Incidence reflectivity (NI), responds to changes in acoustic impedance. The second term, defined as the Poisson reflectivity (PR), relates to changes in Poisson’s ratio. Unlike NI, PR remains sensitive to lithologic variations within this geologic environment. The rock property contrasts, which generate the NI and PR response, become evident by crossplotting well-log values of acoustic impedance versus Poisson’s ratio. The crossplots show that even when the sands have the same acoustic impedance as the encasing shales, Poisson’s ratio discriminates between them. To obtain a robust estimate of PR, the AVO processing incorporates corrections for anisotropy, which extends the AVO analysis out to very-far offset traces. Finally, a view of the lithostratigraphic properties develops by displaying the NI and PR estimates from the seismic data with a novel color crossplotting method. Unlike the stack amplitude, distinct reservoir features appear in the seismic crossplot volume. After calibration, these 3D crossplot sections provide maps of reservoir quality sands and potential pay intervals.

You do not currently have access to this article.

Figures & Tables

Contents

GCSSEPM

Stratigraphic Analysis Utilizing Advanced Geophysical, Wireline and Borehole Technology for Petroleum Exploration and Production

Jory A. Pacht
Jory A. Pacht
Seis-Strat Servies, Inc. Sugar Land, Texas
Search for other works by this author on:
Robert E. Sheriff
Robert E. Sheriff
University of Houston Houston, Texas
Search for other works by this author on:
Bob F. Perkins
Bob F. Perkins
GCSSEPM Foundation West Hartland, Connecticut
Search for other works by this author on:
SEPM Society for Sedimentary Geology
Volume
17
ISBN electronic:
978-0-9836097-6-6
Publication date:
December 01, 1996

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal