Multi-Scale Integrated Approach for Better Understanding Reservoir Heterogeneity: Case Study of the Green River Formatio

Pre-salt carbonate reservoirs are a challenge for the exploration and production. Using outcrop analogues provides key information for a better characterization of the complex architectures of these deep reserves.

The aim of this study is to better understand heterogeneity of an outcrop analogue of an Atlantic pre-salt carbonate reservoir: the Green River Formation (Wyoming, USA). The Laney Member of the Green River Fm corresponds to marginal lacustrine carbonates deposits, and its architecture is complex: it is organized in patches of reef-like morphologies made up of microbialites, with intercalated breccia and shales. The internal organization of microbialites consists in various nested scales of heterogeneities.

In order to describe reservoir properties and facies distribution in these complex architectures, an integrated approach is built using sedimentological, petroacoustical and petrophysical data acquired at different spatial and frequency scales. From this exhaustive dataset, electrofacies are determined from gamma ray and sonic and then compared with sedimentological facies. Finally, using measurements on core samples, dynamic properties are introduced into the classification in order to obtain rock-types.

This integrated workflow is a tool for better understanding microbial dominated lacustrine system. It allows to identify main heterogeneities, but shows also some limits.