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Effects of Differential Dissolution on the Acoustic Properties of Carbonates (Upper Cretaceous Skeletal Grainstones, Southeastern Netherlands)

Jeroen A. M. Kenter, Marc Reinders, Bruce W. Fouke, Wolfgang Schlager

With the growing need of more precision in calibrating the seismic record with lithologic and stratigraphic observations (e.g. by generating synthetic seismic models of outcrops) more information is needed on the fundamental properties of the rock itself. In contrast to the acoustic behavior of siliciclastics, the acoustic properties of carbonates are highly Previous HitvariableNext Hit. Three of the parameters that control the acoustic behavior of carbonates are porosity, clay content, and diagenetic processes. The net effect of diagenetic processes of leaching and cementation cause significant deviations (positive and negative) from values predicted by commonly used empirical equations.

Laboratory measurements of P-wave Previous HitvelocityNext Hit in cemented grainstones from the Cretaceous in southeastern Netherlands are significantly higher than those in poorly cemented grainstone of similar depositional texture, an effect that cannot be explained by the decreasing porosity. Image analysis studies of the sediment texture confirm that poorly and moderately cemented grainstones have similar texture (size, shape, aspect ratio, and relative orientation of grains and pores). Petrographic and SEM observations show a difference in the presence of calcite cement at grain contacts that is linked to differential dissolution.

Similar observations in carbonates from the Great Bahama Bank and volcaniclastics from ODP Leg 143 confirm the presence of a threshold in the proportion of cement that causes a significant jump in acoustic Previous HitvelocityTop that cannot be explained by existing empirical equations. These observations underline the significance of diagenesis for the variation in the acoustic properties of carbonates and has consequences for predictive seismic modelling and interpretation.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995