Seismic modeling of two depositional systems

Abstract

Two ideal lithologic sections representing a tidal bar system and a fluvial complex were drawn in order to run seismic modeling programs developed by OGS on behalf of the European Community. The simulations allowed an accurate analysis of the seismic expressions of the two sections. The tidal bar system is formed by a number of sandstone lenses interlayered with siltstone and mudstone deposits. These lenses meet together on an erosion surface, while they thin and vanish in the other direction. The fluvial complex is fonned by a limestone basement overlain by coarse alluvial plain sediments which in turn are transgressed by finer flood plain sediments, including sandstone lenses stacking towards the top in a meandering belt. These lithofacies associations represent potential multi-pool reservoirs in which the mudstone layers constitute the plugs. As a function of the granulometric and depositional features of each lithological unit, together with fluid content, wave velocities and densities were evaluated. A 2D modeling for elastic plane wave propagation in these hypothesized geologic sections was run on a Cray supercomputer. The numerical scheme is based on solving the full wave equation by pseudospectral methods.