Niobrara Chalk

Core analysis is challenged when physically measuring permeability, capillary pressure, “irreducible” water saturation, and relative permeability for rocks with permeability of 0.000001-0.1 millidarcies (mD). Measurements are complicated by stress-dependency, high capillary pressure, microcracks, differing PHI-K-Sw measurement methods, and controlling fluid distributions. Image-based digital rock physics provides independent complimentary measurements. The objective of this study was to develop an integrated core analysis (CA) and digital rock physics (DRP) workflow and measure these properties. Using a workflow integrating CA-DRP, we characterized the Niobrara Formation chalks and marls, Denver Basin, Colorado. CA was performed on representative chalk/marl samples and high resolution 3D microscope images were acquired using focused ion beam scanning electron microscopy. Carefully cross-validated digital rock physics and core analysis is an extremely powerful tool for microdarcy rocks, and digital rock physics provides unique data particularly in assessing permeability relationships and saturation/bound water influences. Properties computed herein have been used in reservoir- and well-scale numerical flow modeling to support exploration, completion and production management decisions.

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Niobrara1     Niobrara2

Left: Niobrara Chalk Surface SEM Image, Right: Niobrara Chalk FIB-SEM Image