Conditional Simulation of Sedimentary Cycles in Three Dimensions

Abstract

We propose a method to determine the most probable pattern of a sedimentary cycle between boreholes. The purpose of this conditional simulation method is to solve a three-dimensional quantitative problem. It differs essentially from classical methods of quantitative studies by involving several dimensions and by not using any Markovian property. The example is the Permo-Triassic sedimentary cycle of the Chemery structure in the Paris Basin. It is a fluvial or deltaic sequence of clayey and sandy lenses. The structure is outlined by 15 boreholes.

Some genetic hypotheses are made about the cycle. A random- genetic model is proposed which fits the available data. The most probable lithological correlations between layers of different boreholes are determined. To do this a maximum likelihood method is used. The most probable shape of lenses between boreholes for each group of contemporary lenses is determined. In this manner the problem is thus solved. The results are given as a set of thickness maps for successive groups of lenses and as cross sections.