ABSTRACT

Infrastructure-led exploration wells drilled in turbidite-dominated depositional systems along the Gulf Coast continue to face key geologic risks including reservoir presence and reservoir quality. 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. While a number of industry-sponsored studies have argued that the depositional environment for this group ranges from traditional deep-water 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, one of the common threads is that provenance and sedimentation process carries significant weight in determining the overall reservoir quality. These observations have built momentum to study other oil fields and their outcrop analogs through a similar lens around the world.

This presentation features outcrop and subsurface data from five locales in the Gulf of Mexico, Western Irish Namurian, Alpine foreland, Taranaki, and Ventura basins to highlight four important themes pertaining to reservoir quality characterization: (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; (2) what is the range and variability in deepwater stratigraphic terminations, and how do sedimentation units change from axis to off-axis positions; (3) how are source-to-sink studies applied to better predict reservoir quality variations; and (4) what is the range and variation in slurry-flow deposits in active and passive margin settings? 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 stratigraphic sections in each system reveals the range of solutions to the themes as well as the applicability of the workflow in quantifying geologic risk and uncertainty in modern drilling programs. Additionally, these results provide valuable insights for assessing petroleum reservoir characterization in comparable siliciclastic intervals from arc to mature passive margin settings, both within the Gulf of Mexico and more generally.

BIOGRAPHY

Jon R. Rotzien is President of Basin Dynamics, LLC in Houston, Texas and Visiting Assistant Professor at University of Louisiana at 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 to mature basins. Prior to his present positions, 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, sedimentary provenance, basin analysis, and geophysics.