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Controls on Shelf-Margin Architecture and Deep-Water System Development in Contrasted Tectonic and Climatic Settings: Insights From Quantitative 3-D Seismic Stratigraphy

Abstract

With ~15% of siliciclastic hydrocarbon reservoirs located within deep-water basins, a key challenge for the industry is to predict when and where sands are bypassed to deep-water areas, and how they are architecturally organized.

Quantitative 3D seismic stratigraphy (QSS) aims at investigating the linkages (quantified relationships) between hydrodynamic regime along paleoshorelines, shelf-margin architecture and the architecture of coeval deep-water systems in a variety of tectonic and climatic settings. This approach is underpinned by state-of-the-art, full volume 3D seismic interpretation methods that enable very high-resolution seismic stratigraphic analysis of extensive 3D seismic data in a cost-effective timeframe.

Here, we present results obtained from several margins developed in late syn-rift to early post-rift; and deep water fold and thrust belts settings.

Margins developed in extensional basins present relatively low reliefs (<500 m) and are associated with small and short-lived river systems. They are mostly supply- and sand-dominated. Due to the (1) shallow configuration of the margin, (2) presence of short slopes, (3) overall high sand-to-mud ratio, and (4) presence of small and likely short-lived fluvial feeder systems, their linked turbidite systems tend to have short run-out distances (<100 km) and a low architectural maturity. In contrast, margins developed in collisional basins display high reliefs (>500 m) and are associated with larger river systems (associated with active onshore accretion), which the capacity to build longer-lived and architecturally more mature turbidite systems with longer run-out distances (>100 km).

Climate also affect the depositional systems building across the shelf and the overall morphology of the margins. In icehouse systems, high-amplitude and high-frequency eustatic fluctuations promote longer periods of shelf exposure and incised valley development, hence directly impacting the processes delivering sands to deep-water areas. In contrast, the low-amplitude and low-frequency eustatic fluctuations of greenhouse systems promote more efficient deep-water sand delivery as deltaic shorelines are located at the shelf edge during longer periods of time, particularly in supply-dominated systems.

QSS represents an innovative approach to better quantify and evaluate the controls on deep-water sand delivery in different tectonic and climatic settings, hence providing an additional tool to better predict the formation of deep-water reservoirs.