Seismic Modeling Applied to Stratigraphic Models to Assess Seismic Interpretation Consistency

Cacas, Marie-Christine, Caroline Sultzer, Caroline Joseph, Emily Albouy, Institut Francais du Petrole, Rueil-Malmaison Cedex, France

Stratigraphic modelling simulates erosion, sediment transport and deposition at basin scale and geological time scale. It provides three-dimensional sub-surface models in terms of isochron surfaces and sedimentary filling, i.e. lithologic proportions between these sur­faces.

Sub-surface models provided by stratigraphic modelling can be constrained by seismic horizons and well data. However, these constraints are often sparse and fuzzy, and usually allow for multiple solution models to be proposed.

A methodology to validate or unvalidate a solution model is proposed here. It is based on a synthetic seismic modelling ran on the sub-surface model. The validation consists in comparing the obtained synthetic seismic to the real acquired seismic image. Comparison criteria are basically texture attributes.

The methodology proposed here includes a down-scaling of the stratigraphic model, since stratigraphic models discretization is usually too coarse for seismic modelling purpos­es. The down-scaling is performed by running a non-stationnary geo-statistical simulation. The simulation grid is built from isochron surfaces. Proportion matrices are directly given by lithological proportions output from the stratigraphic model. Synthetic seismic modelling is a simple 1D convolution.

This methodology is applied to real data at basin scale and to synthetic geological envi­ronments modeled at the scale of a prospect. Results definitely show that this methodolo­gy helps to discriminate between possible scenarios and hypotheses: for given acoustic properties measured at wells, resulting synthetic seismic textures are sensitive to lithology proportions and depositional environments.