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The AAPG/Datapages Combined Publications Database
CSPG Bulletin
Abstract
"Colour Imaging of
Velocity
Variations Due to Fracture Porosity and Fluid Content [Abstract]"
ABSTRACT
Consolidated reservoir formations are defined as those having consistently higher acoustic impedance (density and velocity
product) than similarly aged, normally pressured shales. For such formations, porosity and hydrocarbon effects can be effectively imaged via seismic
velocity
changes over a substantial range of depths (to 16,000+ feet/4877+ m). Additionally, the
velocity
variations that could be noted had quantitative significance in terms of reservoir quality and production potential.
The goal of this exposition is to illustrate the technology, which has been verified in a number of diverse examples. We shall note consolidated sand and carbonate reservoirs from South Texas, northern Oklahoma and the North Sea. Fractured reservoir plays of current interest encompassing such formations would include the Austin Chalk (Cret.), Mississippian Osage Lime, and Niobrara as well as others.
End_Page 216------------------------
The effectiveness of spatially dense seismic velocity
measurements and colour inversion sections scaled in
velocity
is clearly demonstrated by the variety of successful examples reviewed.
Velocity
drops observed for gas presence (greater than 1,000 ft./sec) approach those typically seen for unconsolidated reservoirs. Smaller, but significant
velocity
drops are noted for oil-filled reservoirs (400 to 800 ft./sec) as in the case of the Austin Chalk. Such effects can not be viewed on conventional black and white displays of normally processed seismic
data
. "Coarse" processing loses the detailed information, and visual dynamic range limitations are severe.
Colour inversion displays from properly processed seismic data
can image these target zones quite clearly. Additional
analysis
such as "DIVA" can also indicate the orientation of fracture zones using conventionally processed seismic
data
.
End_of_Record - Last_Page 217-------
ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES
1 N.S. Niedell & Associates, Houston, Texas 77042
Copyright © 2003 by The Society of Canadian Petroleum Geologists. All Rights Reserved.