Abstract:

A new technique is presented for generating high-resolution digital models of natural sedimentary deposits for quantitative analyses. The traditional technique of 2D sedimentary-relief peels of unconsolidated clastic deposits is combined with modern digital laser scanning and 3D microscopy techniques to represent spatially varying rock properties related to sedimentary fabrics at native resolution (millimeter to meter-scale). Peel topography (relief) is documented to correlate with changes in mean grain diameter and standard deviation, so that the topography can be used as a proxy (inferred) for spatially varying rock properties related to grain sizes and sorting (e.g., permeability, threshold pressure). To provide an applied example of the value of such investigation, and to illustrate the influence that sedimentary structures can have on fluid migration, peel topography is used to populate a threshold pressure 2D continuum for invasion percolation (IP) simulations. IP is typically used for hydrocarbon migration and is being explored to investigate CO2 migration in sequestration contexts. Simulation results for a 3.1-million-cell model (∼ 0.5 × 0.25 m) of a ripple-laminated peel from a modern fluvial point bar suggest that sedimentary fabrics can strongly modify saturation via local capillary trapping. The technique, datasets, and analysis presented are broadly applicable and expand quantitative characterization capabilities for a variety of geologic studies.

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