Quantifying 3-D Heterogeneity in Fluvial/Deltaic (Incised-Valley/Lowstand Wedge) Environments with 3-D Seismic Data
DESHPANDE, Anil., Department of Geosciences, 801 Deike Building, Penn State University, University Park, PA 16802, anil@essc.psu.edu; FLEMINGS, Peter B., Department of Geosciences, 541 Deike Building, Penn State University, University Park, 16802, flemings@geosc.psu.edu.
We document scale-invariant statistics and strong anisotropy in rock properties from well log and 3-D seismic data in fluvial/deltaic (incised valley/lowstand wedge) environments. Spectral analysis is used to characterize the scale-invariant behavior through a correlation coefficient, b, which captures the degree of correlation in profiles and surfaces (b=0 for white noise). In vertical and horizontal log data we find b=1.8 for lithology logs (gamma-ray and spontaneous potential) and impedance logs (density * velocity). The variance of the horizontal data is one fifth that of the vertical data. Horizontal seismic depth slices of impedance (extracted from 3-D seismic data) in fluvial and deltaic settings also exhibit scale-invariant behavior. In the fluvial environment, there is higher correlation in the direction of stratigraphic dip associated with the fabric of channel systems (b along channel orientation = 2.7; b perpendicular to channel orientation =1.1). In the lowstand deltaic wedge, we do not find anisotropy. As in the log analysis, we find the lowstand deltaics have much greater variance than the incised fill. These results suggest that different depositional environments may have characteristic correlation parameters. We envision that distinct correlation behavior may be associated with both depositional processes and changes in accommodation (through variations in sea level, subsidence and sediment supply). This approach provides a methodology to characterize 3-D heterogeneity at the meter to kilometer scale which compliments outcrop studies. The results can be used to gain insight into depositional processes and to constrain stochastic simulations of heterogeneity for hydrodynamic-, geologic-, and seismic-modeling.