Guillaume Rongier

A geostatistical approach to the simulation of stacked channels

Turbiditic channels evolve continuously in relation to erosion-deposition events. They are often gathered into complexes and display various stacking patterns. These patterns have a direct impact on the connectivity of sand-rich deposits. Being able to reproduce them in stochastic simulations is thus of significant importance. We propose a geometrical and descriptive approach to stochastically control the channel stacking patterns. This approach relies on the simulation of an initial channel using a Lindenmayer system. This system migrates proportionally to a migration factor through either a forward or a backward migration process. The migration factor is simulated using a sequential Gaussian simulation or a multiple-point simulation. Avulsions are performed using a Lindenmayer system, similarly to the initial channel simulation. This method makes it possible to control the connectivity between the channels by adjusting the geometry of the migrating areas. It furnishes encouraging results with both forward and backward migration processes, even if some aspects such as data conditioning still need to be explored.

Stochastic simulation of channelized sedimentary bodies using a constrained L-system

Simulating realistic sedimentary bodies while conditioning all the available data is a major topic of research. We present a new method to simulate the channel morphologies resulting from the deposition processes. It relies on a formal grammar system, the Lindenmayer system, or L-system. The L-system puts together channel segments based on user-defined rules and parameters. The succession of segments is then interpreted to generate non-rational uniform B-splines representing straight to meandering channels. Constraints attract or repulse the channel from the data during the channel development. They enable to condition various data types, from well data to probability cubes or a confinement. The application to a synthetic case highlights the methods ability to manage various data while preserving at best the channel morphology.

Quality Analysis of Geostatistical Simulations through their Connected Structures

Various methods have been developped to perform geostatistical simulations. Depending on the studied case, each of them can claim to obtain the best results, but it is rarely supported by an objective and quantitative analysis, especially concerning the geological structure reproduction. In this work we propose to go deeper into the assessment of realization quality through connected geobodies, focusing on the capacity to reproduce connected geological strutures. This quality assessment relies on quality indicators computed on each realization. The realizations are then compared based on a dissimilarity calculated from the indicators. The dissimilarity analysis is facilitated using multidimensional scaling (MDS) completed with heat maps. The application of this methodology to a synthetic case and associated realizations gives rise to some practical considerations. While MDS is a powerful tool to facilitate the analysis, it does not represent exactly the dissimilarities, leading to possible misinterpretations. Details considering the relationship between the realizations should preferably be analyzed on the heat map as it represents directly the dissimilarities. This connected geobody-based method appears to complete pattern histogram-based method, which less take into account pattern relationships.