Stratigraphic evolution of an estuarine fill succession and the reservoir characterization of inclined heterolithic strata, Cretaceous of southern Utah, USA
Cari L. Johnson, L. Stright, R. Purcell, P. Durkin, 2017. "Stratigraphic evolution of an estuarine fill succession and the reservoir characterization of inclined heterolithic strata, Cretaceous of southern Utah, USA", Sedimentology of Paralic Reservoirs: Recent Advances, G. J. Hampson, A. D. Reynolds, B. Kostic, M. R. Wells
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This study documented the architecture of a paralic succession using outcrops of the Upper Cretaceous John Henry Member of the Straight Cliffs Formation, southern Utah (USA). The 65 m thick interval of interest includes a basal succession of elongate tidal bars, which sits unconformably on the Calico Bed of the Smoky Hollow Member. These barforms are overlain by carbonaceous estuarine bay fill with tidal deposits, a bayhead delta and, ultimately, a coastal plain succession. The estuarine succession demonstrates a decreasing tidal influence through time and this is interpreted to reflect evolution from a mixed-energy to a wave-dominated estuary as a result of the changing morphology of the estuary and/or the migration of barrier islands across its mouth. The regional correlations are also discussed, with implications for sequence stratigraphic interpretations. A detailed interpretation of the ancient bayhead delta highlights the internal architecture and provides data for statistical comparison between this feature, which is dominated by inclined heterolithic strata, and a previously published study of fluvial point bar inclined heterolithic strata. The results emphasize distinct grain size trends from these two examples, as well as differences in the continuity and spatial distribution of mudstone drapes, which act as both baffles and barriers to fluid flow.
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Paralic reservoirs reflect a range of depositional environments including deltas, shoreline-shelf systems and estuaries. They provide the backbone of production in many mature basins, and contribute significantly to global conventional hydrocarbon production. However, the range of environments, together with relative sea-level and sediment supply changes, result in significant variability in their stratigraphic architecture and sedimentological heterogeneity, which translates into complex patterns of reservoir distribution and production that are challenging to predict, optimize and manage.
This volume presents new research and developments in established approaches to the exploration and production of paralic reservoirs. The 13 papers in the volume are grouped into three thematic sections, which address: the sedimentological characterization of paralic reservoirs using subsurface data; lithological heterogeneity in paralic depositional systems arising from the influence of tidal currents; and paralic reservoir analogue studies of modern sediments and ancient outcrops. The volume demonstrates that heterogeneity in paralic reservoirs is increasingly well understood at all scales, but highlights gaps in our knowledge and areas of current research.