High-Resolution 3D Stratigraphic Modeling: From Digital Outcrop Modeling to Carbonate Sedimentary System Characterization - Example of the Gresse-En-Vercors Lower Cretaceous Carbonate Platform (South-East France)*

Typical ancient carbonates reservoirs are characterized by imbricated stratigraphic architecture and facies at various spatial dimensions, thus resulting in a wide range of heterogeneities at different scales. More specifically, the accurate characterization of the spatial relationships between stratigraphic architecture, sedimentary geometries and facies is fundamental to understand the parameters and processes registered in these carbonate systems, and to predict sub-surface rock properties repartition and the flowunits connectivity. This is also critical for 3D modeling of hydrocarbon carbonate reservoirs properties. A possible large part of the misconception of ancient carbonates is rooted in the difficulty to obtain high-resolution data set over carbonate systems (modern and ancient) that typically cover areas of at least several hundreds of km 2 . Platform-to-basin transition or ramp that form gentle slope over several kilometers - and are associated to various facies mosaic - can propagate through time in complex prograding systems with. Such strata forms are very critical in sub-surface as they can result in non-layer cake reservoir architecture more challenging to predict and model. On outcrop models, such carbonate systems are characterized by high resolution (cm-dm) and low uncertainty in the “vertical” direction (perpendicular to strata) and variable (low-high) resolution and uncertainty in the “lateral” directions (conform to strata). This is the consequence of the poor horizontal continuity of outcrops compared to the great lateral dimensions of the platform systems. In this case, the spatial gap is filled by stratigraphic interpolation and correlation between observations that is not constrained by data. Concepts and knowledge used in this correlation process are based on recent carbonate depositional environments, seismic or outcrop analogue.