Thin-Bedded Reservoir Analogs in an Ancient Delta Using High-Resolution, Ground Based Remore Sensing Technologies: Cretaceous Notom Delta
Snyder, Casey J. 1977-
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Portable high-resolution hyperspectral and a Terrestrial Laser Scanner (TLS) are used to image fine-scale heterogeneity in a fluvial-deltaic reservoir analog of the Cretaceous Ferron Notom deltaic sandstone in central Utah. TLS is a laser scanning technology used to create an extremely accurate, centimeter to meter-scale, high-resolution, digital representation of the outcrop in 3 dimensions. Hyperspectral sensors record electromagnetic radiation reflected off the outcrop in numerous contiguous bands which were used to generate a spectral signature for each pixel sampled. The spectral signatures are a function of mineralogy, chemistry, grain-size, and cements and were used to distinguish thin mudstones from sandstones within an interbedded sequence. Comparison between the spectral signatures recorded from the outcrop and those of reference materials, and with previous facies architecture studies, enable lithofacies to be accurately mapped. Hyperspectral data was then draped over the TLS model to generate a spatially-accurate detailed 3D geologic map of the heterogeneity. Approximately 150 lateral meters of outcrop were imaged with the hyperspectral camera and TLS system on previously mapped parasequences 5 and 6. These parasequences record ascending regressive shoreline trajectories. Parasequence 6 previously has been interpreted to be fluvial-dominated and parasequence 5 had been interpreted to record significant wave influence. Particular emphasis is placed on heterolithic thin-bedded facies of the distal delta front. The beds within parasequence 6 are shown to have trends in bed thickness laterally. Thinning rates trends showed anisotropy in the data based on the dip versus strike orientations of the previously- interpreted paleogeography. The plan-view geometry of the thin-beds was estimated based on these data. The resulting plan-view geometry model suggested the thin-beds originated as lobate to elongate turbidites and hyperpycnites, associated with fluvial-dominated depositional processes, an interpretation consistent with previous studies. The hyperspectral data provides continuous 3D maps of grain-size and lithology which emphasizes potential permeability differences in the outcrops, offering insight into predicted reservoir behavior. Hummocky cross-stratified beds were mapped in parasequence 5 and were shown to vary in thickness laterally in an undulatory manner and amalgamate frequently.