Evolution of Middle Eocene Tide-Dominated Deltaic Sandstones, Lagunillas Field, Maracaibo Basin, Western Venezuela
Jesus Maguregui, Noel Tyler, 1991. "Evolution of Middle Eocene Tide-Dominated Deltaic Sandstones, Lagunillas Field, Maracaibo Basin, Western Venezuela", The Three-Dimensional Facies Architecture of Terrigenous Clastic Sediments and its Implications for Hydrocarbon Discovery and Recovery, Andrew D. Miall, Noel Tyler
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Interpretations of net-sand/percent-sand maps, well-log cross sections, vertical log-pattem trends, core descriptions, and log facies suggest that several aggradational tide-dominated deltaic cycles were deposited in Lagunillas field. Western Venezuela, during a widespread transgressive event at the end of the Middle Eocene. Reservoir lithofacies present are estuarine distributary-channel sandstones, tidal sand-ridge sandstones, prodelta/shelf assemblages, and tidal-channel facies. Geometries of the sandstone bodies are highly dip elongate and strike lenticular. These shoestring sands maintain their widths in a landward direction (west) and splay outward at their seaward limit (east), where loci of sand deposition occurred. Eastward, the sequence thickens concomitant with a decrease in sand-to-shale ratio. Individual correlatable depositional units are interpreted to be discrete delta lobes established during progradation of estuarine distributary systems. These single delta lobes shifted laterally along strike during infilling of deltaic depositional axes. Laterally persistent low-resistivity shale markers stratigraphically bound several delta lobes, which together constitute one of five deltaic cycles present in the upper reservoirs of the field.