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Geologically Consistent Rock Physics- and AVA Depth Trends in Siliciclastic RocksNormal access

Author: A.D. Draege
Event name: Fourth EAGE Workshop on Rock Physics
Session: Sedimentological Integration With Rock Physics
Publication date: 11 November 2017
DOI: 10.3997/2214-4609.201702449
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1013.38Kb )
Price: € 20

Summary:
Rock physics depth trends is a powerful tool for estimating changes in reservoir properties and seismic response for various depths, pressures and temperatures. Recorded subsurface properties at a given depth can be extrapolated up and down in the lithological column. Traditionally, rock physics depth trends are estimated for an “average” or representative homogeneous sand and shale without honoring the internal cyclicity in the sediments. The traditional method therefore results in smooth sand and shale trends, with only small variations in properties within small depth intervals. A heterogeneous sandstone will for instance be approximated with a homogeneous sandstone with representative properties when depth trend modeling is performed. This will lead to information loss and increase the uncertainty of the results. It can be of large importance for seismic and amplitude versus angle (AVA) response if a heterogeneous sand is more dirty in the top or the base, and this information will not be included when making traditional smooth depth trends. This study demonstrates a workflow for modeling rock physics depth trends where internal geological variations in sands and shales are included. The estimated depth trends of elastic properties and density are used to model AVA responses versus depth for a shale – sand interface while honoring geology.


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