Architecture and Geometry of Clastic Injectites Network and Their Feeder—an Outcrop-Based Model to Constrain Reservoir Modeling: The Example of the Vocontian Aptian and Albian Massive Sands, Southeast France

Fries, Gerard Olivier¹, Olivier Parize² (1) Institute Francais du Petrole, Rueil-Malmaison, France (2) Ecole des Mines de Paris, Fontainebleau, France

Massive sandstones are excellent hydrocarbon reservoirs deposited in turbiditic envi­ronment. However the original depositional geometries can be dramatically modified by large network of clastic injections (dykes and sills); The geometry and architecture of these network cannot be determined only from core analysis and seismic scale studies provide low-frequency images that need to be detailed and validated prior to reservoir simulation studies.

If turbidites, massive sands or clastic injectites outcrop examples are well-known, few of them give the opportunity to observe, within a well-constrained structural, sedimentary and litho- and chronostratigraphical context, simultaneously the channel feeder in visible connection with the injection network; moreover the quality of the outcrops need to be exceptional to make 3D field observations, in order to have comparable scales of observa­tion from core, well and even to seismic data using GPR technics or high-resolution seismic acquisition.

The Vocontian Aptian and Albian outcrops belong to the category of exceptional “refer­ence” outcrops that can be used as analogues to build full-scale geometrical model, con­straining reservoir models. The Vocontian domain (SE France) provides an example of a well-documented slope complex characterized during the Aptian and Albian by the accumu­lation sandy and mud-prone sediment gravity-flow deposits that can be followed downslope over tens of kilometres. The Aptian and Albian succession exhibits massive sand deposits and large-scale clastic sills and dykes related to minor post-depositional (per ascensum) or upward propagating (Nyons-type) and dominant syn-depositional (per descensum) or downward propagating injectites (Bevons and Rosans-types). These very large kilometre­scale syn-depositional clastic injections mobilize very large volume of sand.

This model is now a reference framework for outcrop and subsurface studies that can be used to visualize the clastic injectites network and the associated feeder and to test dif­ferent hypothesis related to facies, geometry and internal architecture of the sand bodies.