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Computed Tomography (CT) Scans for Mudstone Characterization


Computed tomography (CT) scans when used in conjunction with wireline logs provide a powerful tool to characterize mudstones and to upscale and integrate sample sets from thin section- to core- to wireline log-scale. CT scans provide a non-destructive method to document density differences in three dimensions within cores on a laminaset or bed by bed (mm by mm) scale. CT scan interpretations incorporated with preliminary petrophysical analysis are applied to determine appropriate core sampling programs for mudstone and other fine-grained rock cores. Early characterization of cores with CT scans provides a method to assess overall core integrity by recognizing fractures and drilling induced features. The scans are used to identify sedimentary features (laminasets, scours, cross laminae), macrofossil occurrences and trace fossil assemblages, and to distinguish low density, organic-rich intervals, and identify high density cements (pyrite and barite) distribution. Subsequent to a detailed characterization of the 3D CT scans, lithofacies “packages” with distinctive architecture, ichnofacies distributions and compositional variations can be recognized and tied to sequences or stratal units expressed in the wireline logs. These analyses assist with sampling strategies and in choosing more precise sample locations. The CT scans provide a platform for upscaling and integrating the resultsfrom thin section petrographic analysis, X-ray diffraction (XRD) and geochemical analyses) to the wireline logs for modeling completion strategies and for reservoir modeling.