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Nannofossil Paleoecological Indices: Implications for Reservoir Characterization, Petroleum Systems and Sequence Stratigraphy

Abstract

Nannofossil Paleoecological Indices: Implications for Reservoir Characterization, Petroleum Systems and Sequence Stratigraphy

The quest for increased correlative resolution through biostratigraphic innovation is only limited by our imaginations and willingness to explore new ideas. Looking beyond the stratigraphic information provided by the presence/absence of a particular fossil or assemblage and into the depths of knowledge inherent within biostratigraphic data we find several paleoecological conditions that can be useful. Nannofossil paleoecological indices have utility in examining petroleum systems and providing insight to reservoir characterization in a cost-effective approach, especially in the context of other data (i.e. sequence stratigraphy and benthic foraminiferal data). A new numerical paleoecological indice will be presented using inferences from the literature. Genera or species are selected from observed assemblages with known ecological conditions within sequence stratigraphy (compiled in Flores et al. 2005). These genera/species are then plotted as a proxy to model relative paleoecological conditions during deposition in wellbores of unknown paleoecological settings. Indices include oceanographic conditions/nutrient availability (trophic state), temperature, and shoreline proximity (or salinity). Though application (so far) has been limited, results indicate an ability for the assemblages to allow biostratigraphers to make some basic ecological inferences that can provide insight into depositional settings and petroleum systems.