3-D Stratigraphic Modeling of Sedimentary Basins
Thanks to the recent developments in geology and applied mathematics, relationship between climatic, tectonic and sedimentary processes can now be investigated from source to sink, using numerical stratigraphic forward models, such as Dionisos.
A Dionisos simulation is performed from the past up to the present in a sequence of time steps. At each time step, a hydrology model is used to define either the depth of lakes or the height of fluvial channels in continental environments, taking into account the balance between rain fall, run-off and evaporation, and assuming a permanent water flow. Terrestrial organic matter and evaporites are then produced respectively in lacustrine and sabkhas. The hydrology model is also linked to a weathering model (at each point of the basin, the erosion rate is controlled by the local slope and shear stress induced by water flow), and transport model, to define the sediment transport induced by slope-driven and water-driven processes (sediment flux is assumed proportional to the energy slope and the water discharge). The fluvial flow is then transformed either as a hypopycnal or a hyperpycnal flow at the plunging zone (i.e. the transition between continental and marine environments), based on the momentum of and sediment concentration in this fluvial flow. This marine clastic flow may then interfere with carbonate production, which is as a function of water depth, wave energy and ecological parameters.
Some applications on passive and active margins are presented to illustrate these principles, such as the Miocene formation of the Gulf of Mexico (interaction of a clastic deltaic progradation and a series of growth faults and shale diapirs), the Messinian formation along the NW Mediterranean Sea (high-frequency climatic variations, induced by a precessional forcing, controlling the deposition of gypsum beds and organic-matter rich marls), and the Pleistocene / Holocene evolution of the Orinoco deep sea fan (climatic variations, shelf progradation and turbiditic systems). These applications show us that stratigraphic forward models are dreamed tools to decipher the sedimentary infill of basins, and can help petroleum geologists to explore frontier areas and better define new plays, although great scientific effort still have to be put on their developments to close the process-deposit loop at a source to sink scale.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009