Exploration applications of integrated biostratigraphic analysis, plio-pleistocene, offshore Southern Trinidad

The Neogene depositional history of the Eastern Venezuela Tertiary Basin is dominated by north to northeast transport of deltaic sedimentation overprinted by complex tectonics. Exploration requires precise correlations and carefully constrained depositional models and risk assessment is facilitated by an understanding of depositional environments based on integration of biostratigraphy, seismic sequence stratigraphy, log-motif analysis and seismic facies mapping. Correlation of the offshore Trinidad Columbus and Carambola wells, and their use in calibrating seismic reflection profile analysis, illustrates this process of integrated stratigraphic interpretation. The seismic reflection profiles are dominated by parallel continuous reflections and the tectonic overprint of phases of extension and compression. Locally developed unconformities and clinoforms of basin-slope scale identify what may be several sequence boundaries. Relative abundance plots of climatically controlled littoral and terrigenous derived palynomoph taxa show well developed arid-to-wet cycles. Biofacies analysis of benthic foraminiferal assemblages identifies patterns of shallowing and deepening environments. Integration of palynological and foraminiferal analyses defines two distinct associations/trends interpreted as environmentally significant: a. Low seal-level association: Arid palynomorph assemblage and shallowing foraminiferal biofacies. b. High seal-level association: Wet palynomorph assemblage and deepening foraminiferal biofacies. Within the context of major marine incursions, these biofacies cycles, when integrated with seismic facies andmore » wireline log stacking patterns, provide a framework for defining and correlating sequences. The distribution of seismic facies, log-facies and biofacies within each depositional sequence provides paleogeographic maps suitable for assessing the probable depositional environment, and also reservoir and seal potential within each structural closure.« less