Acoustic
Behavior of Sedimentary Rocks: Geological Properties Versus
Poisson's Ratios
Verwer, Klaas1, Hendrik
Braaksma2, Jeroen Kenter3 (1) Vrije Universiteit,
Amsterdam, Netherlands (2) Universite Montpellier 2, Montpellier, France (3)
Chevron Energy Technology Company, Voorburg, Netherlands
Velocity transforms are fundamental tools
for the extraction of geological information from seismic reflection data sets
and or predicting porosity from wireline logging data. Most commonly used
transform are all based on empirical relationships extracted from relatively
small, “clean”, mono- and bi-mineral and mostly siliciclastic data sets and
generally fail to explain the acoustic relationships within multi-mineral data
sets. To extract globally significant relationships between geological and
acoustic parameters, over 2800 plug measurements were collected from own
measurements (more than two-thirds of the data) and the literature. Fundamental
parameters that control the mechanical properties of the different sediment
groups are rock texture and mineralogy, typical “geological properties”. Using
cross plots of Poisson's ratio versus compressional wave impedance (including
shear wave properties) rock texture can be differentiated. Sedimentary rocks
that have retained their granular texture largely overlap and include
carbonates and siliciclastics, whereas rocks that are recrystallized, and as a
consequence have lost that character, occupy a completely different area in the
cross plots. Rocks that have a transitional character are found to connect both
regions. The results demonstrate an intimate relationship between mechanical
behavior and the primary as well as diagenetic overprint of the sedimentary
rocks and allow the direct extraction of crystalline, granular and mixture
behavior and, secondly, the relative mineral composition within those groups.
This relative simple approach may have great significance for the general
prediction of rock types and index properties from seismic data sets and in
well bores.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California