Euzen, Tristan¹, D. Granjeon¹, R. Eschard¹
(1) Institut Français du Pétrole, 92852 Rueil Malmaison Cedex, France

ABSTRACT: Stratigraphic Modelling of Deep Offshore Turbiditic Fans Deposits. Application to the Pab System (Maastrichtian, Pakistan)

Stratigraphic forward modelling provides additional constraints for reservoir prediction at basin scale. The aim of this study was to simulate two contrasting turbiditic depositional systems using a deterministic approach.
The Upper Maastrichtian Pab turbidite system crops out in Western Pakistan, and was deposited in a passive margin setting. The Lower part of the system is a sand-rich basin floor fan fed by a canyon cutting the shelf and the slope, whereas the upper part consists of a sand-rich slope fan directly fed by a delta.
The Dionisos software is a three-dimensional forward stratigraphic model that simulates sediment erosion, transport and deposition from exploration to appraisal scale. The input parameters of the model are initial bathymetry, accommodation, sediment supply, and transport parameters. Three main processes are taken into account using deterministic equations: (1) long-term low-energy fluvial flows, (2) short-term high-energy turbidity flows, and (3) catastrophic slope failure and debris flows.
The depositional model of the Pab system was used to calibrate the input parameters of the forward stratigraphic model. Sub-marine erosion in canyon and channel complexes, prograding terminal lobes and back-stepping filling of the system were successfully reproduced. The upper Pab sand-rich slope fan was simulated by hyperpycnal flows transporting sediment load across the shelf break from the prograding delta.
This stratigraphic modelling allows validating the depositional model derived from outcrop analysis and lead to a better understanding of the system thanks to the coupling with a process-based approach.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.