Two-Dimensional Stratigraphic Simulation of the Malay Basin

Abstract

Stratigraphic simulation is a computer modelling technique that can be applied in petroleum exploration to understand the depositional geometries and architecture of a sedimentary basin. By making geologically reasonable assumptions about certain process parameters (e.g. sediment supply and tectonic subsidence rates), realistic stratigraphic geometries and attributes of sedimentary basins can be replicated by forward modelling. There are a number of proprietary and a few commercially available stratigraphic simulation packages designed for this task; ranging from simple 1D to more sophisticated 3D techniques (Ku Rafidah & Mazlan Madon, 2007). In this study we have used SEDPAK™, a 2D modelling package developed by the Stratigraphic Modelling Group at the University of South Carolina (Kendall et al., 1991), to simulate the stratigraphic evolution of the Malay Basin, offshore Peninsular Malaysia. The objective of the study is to investigate the relative influence of the main factors that controlled sedimentation in the basin. In a previous study of overpressure development in the basin (Madon, 2007), subsidence and sedimentation (burial) rates were found to be the main controlling factors in overpressure development. In this study, SEDPAK™ was used to reconstruct a depositional history of the basin by varying the rates of tectonic subsidence, sediment supply and eustatic sea-level change. We have used an interpreted seismic section across the basin as a starting model (Figure 1) and, upon applying a time-depth conversion, constructed a geologic cross-section to be simulated. Based on the published geologic ages of the seismic horizons and the measured thicknesses of the stratigraphic units, their average sediment accumulation rates were derived along the profile as input to the simulation. Figure 2 shows the three main input parameters. The input value for the modelling parameters is varied by trial-and-error iteration until there was agreement between the model result and the observed geometries in the seismic depth-section.