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LGS Luncheon – November 2017


Title: Toward improved modeling in turbidite depositional systems: Case studies from the Gulf of Mexico, Western Irish Namurian Basin, and Alpine Foreland Basin

Jonathan R. Rotzien
Basin Dynamics

Exploration and field extension wells drilled in the Gulf of Mexico and other turbidite-dominated depositional systems continue to face key geologic risks including reservoir presence and reservoir deliverability.  In particular, the Paleogene Wilcox Group shows a broad spectrum of lithofacies, depositional architecture, and reservoir quality over a stratigraphic interval exceeding 6000 ft in the thickest parts of the trend.  Further, a number of industry-sponsored studies have argued that the depositional environment for this group ranges from traditional leveed channels, to sandstone-rich lobes that lack distributary channels and conform to the shape of the underlying topography as a braided system, to sandstone sheets, to sandstone-poor overbank deposits that likely represent deep-water background sedimentation.  Clearly, there is room to enhance the understanding of the stratigraphic architecture and reservoir characterization of target intervals in this trend.

One of the methods to better understand geologic uncertainty in Gulf of Mexico petroleum reservoirs is via the study of global outcrop analogs.  This presentation features new stratigraphic data from two of the most thoroughly studied and classic deep-water outcrops of the Carboniferous Ross Formation, Western Irish Namurian Basin, and the Eocene-Oligocene Annot Sandstone, Alpine Foreland Basin of southeast France, to highlight the architectural complexities and similarities of each system to the Wilcox Group.  The history of exploration into these outcrops began well over a half century ago and inspired the famous work that led to the identification of Bouma and Lowe division terminology.  Today, these systems remain relevant as reservoir analogs for petroleum provinces and will continue to be useful for years as the nature of industry challenges evolve.

Despite decades of research, two important themes have not been solved using the deep-water outcrops in Ireland and France.  Using a core drilled through these outcrops, (1) what are the characteristics of in-channel and out-of-channel bedding, and how can lateral bed continuity be estimated using a process sedimentology approach, and (2) what is the range and variability in deep-water stratigraphic terminations, and how is this new information applied to understanding stratigraphic traps?  These questions address reservoir extent and reservoir quality using common core data that would be acquired in a routine drilling program.  Characterization of high resolution stratigraphic data including grain size, sedimentary process, bed thickness, and bed length from previously unpublished sections in each system reveals the range of solutions to both themes as well as the applicability of the workflow in quantifying geologic risk and uncertainty in modern deep-water drilling programs.  Additionally, these results provide valuable insights for assessing petroleum reservoir characterization in comparable siliciclastic strata, both within the Gulf of Mexico and more generally.






Jon R. Rotzien is President of Basin Dynamics, LLC and Visiting Assistant Professor at University of Louisiana – Lafayette.  His expertise is the sedimentology and stratigraphy of deep-water depositional systems, basin analysis, and source-to-sink sediment transfer.  Jon aims to solve key challenges in the exploration and production of petroleum, including reservoir presence and quality forecasting in frontier basins, and reservoir connectivity, distribution, and deliverability.  Prior to his present position at Basin Dynamics, he was an exploration and appraisal geoscientist at BP.  He received a Ph.D. in Geological and Environmental Sciences from Stanford University and a B.A. degree in Geology from Colorado College.  He has published peer-reviewed research papers and scientific conference proceedings pertaining to reservoir quality, sequence stratigraphy, petroleum geology, process sedimentology, basin analysis, and geophysics.

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