Shelf-margin architecture, sediment partitioning and shallow- to deep-water reservoirs distribution in the Barrow Group (Northern Carnarvon Basin, North West Shelf, Australia): Insights from quantitative seismic stratigraphy

Abstract

Traditional stratigraphic models predict that accumulation of deep-water siliciclastic reservoirs occur when falling sea-levels promote basinward migration of rivers and development of shelf-edge deltas. However, recent studies show that the processes redistributing sediments at the shelf-edge seem to have a direct impact on the shelf-to-basin sediment transfer mechanisms and the accumulation of reservoir-grade sands.

The Barrow Group constitutes a unique example of a regressive shelf margin (~100-500 m shelf-to-basin relief) developed continuously during a syn-rift to post-rift transition (Latest Tithonian – Late Valanginian) in the Northern Carnarvon Basin (North West Shelf, Australia). In this study, we focus on the Lower Barrow Group (LBG; late syn-rift I and II) that developed under supply-dominated conditions. However, lateral variations in subsidence regime and shifts in sediment supply led to significant variations in shelf-margin architecture along strike, directly impacting the distribution of sediments between the shelf and deep-water areas.

To better integrate the variability of shelf-margin depositional systems in time and space, and better understand the shelf-to-basin sediment transfer mechanisms, we present a new workflow combining full-volume 3D seismic interpretation methods with a dynamic stratigraphic approach (i.e., quantitative 3D seismic stratigraphy). This workflow allowed developing a high-resolution seismic stratigraphic framework for the LBG with the identification of 73 clinothems (average time span of ~63,000 years).

The quantitative analysis conducted links together: (1) key shelf-edge geometries (trajectory angle, slope gradient, differential sedimentation between topsets and bottomsets); and (2) paleoshoreline processes and architecture of coeval deep-water deposits (both determined through 3D seismic geomorphology). Statistical analysis of these data reveal the genetic linkages between A/S conditions on the shelf, deltaic hydrodynamic regime and slope-to-basin depositional architecture.

Results show that low A/S conditions on the shelf were associated with sediment bypass to the slope, whereas high A/S conditions were linked with increasing sediment storage on the shelf. While fluvial to wave processes can be dominant in all A/S conditions, fluvial-dominated coastlines are mostly associated with steep clinoform slope gradients and more mature turbidite systems. In contrast, wave-dominated shorelines are linked to gentle clinoform slope gradients and no to poor turbidite system development (unchannelized sheet sands and MTDs), leaving a starved slope. These variations are observed both through time and along strike.

High-resolution 3D quantitative seismic stratigraphy constitutes a new step in sequence stratigraphy as: (1) it allows interpreters to map sequences in a true 3D environment, hence taking into account the full variability of depositional systems through time and space; (2) it highlights the significant role of shelf-margin architecture and processes in predicting the distribution of reservoirs in the shallow- and deep-water segments of continental margins; and (3) it offers an observation-based and model-independent approach to better understand the short-term and long-term controls on sequence development in shelf-margin depositional systems.

Biography

Dr. Victorien Paumard is a Postdoctoral Research Associate at the Centre for Energy Geoscience, University of Western Australia. He graduated with a BSc in Geosciences and a MSc in Petroleum Geosciences from the UniLaSalle University in France; and with a PhD in Basin Analysis and Seismic Stratigraphy from the University of Western Australia. His MSc research was focusing on the 3D seismic stratigraphy of Oligocene-Miocene carbonate platform offshore Myanmar. His PhD research focused on the links between shelf-margin architecture, shallow-marine processes and deep-water depositional systems within the Barrow Group (Early Cretaceous) in the Northern Carnarvon Basin (North West Shelf of Australia). Victorien’s expertise is in basin analysis, seismic stratigraphy and sequence stratigraphy. His research interests are focused on the development of quantitative methods to build 3D seismic and sequence stratigraphic frameworks, better understand the controls on the architecture of continental margins, and better predict the location of shallow-marine and deep-water reservoirs. Victorien is a member of AAPG, ASEG, PESA, SEPM, IAS and GSA.

Venue

This seminar will be held using the video conferencing software Zoom. If you would like the link, please email sees.seminars@uq.edu.au