An Outcrop Analog of Kharaib and Shu’Aiba Reservoir: Example of the Urgonian Platform (Lussanenque Area, Gard, SE France)

Abstract

Urgonian limestone (Lower Cretaceous) of southeastern France is a coeval analogue of the Shuaiba and Kharaib Formations of the Middle East and can constitute a good reference proxy to illustrate and understand the internal geometries of these reservoirs. It is also a relevant database for reservoir modeling and/or EOR studies. Total Company has proposed an R&D work program focused on the comprehension of geometric and petrophysical heterogeneities of the Barremo-Aptian carbonate reservoirs, located in Lussanenque area (Gard, South East France). The present paper allows us to : present internal geometry of high resolution sequences (vertical and horizontal variations at the 4th/5th order of scale) of outcropping sections and thereby comprehension of internal reservoir architecture of the Kharaib and Shu’aiba formations, in contrasted paleogeographic domains of carbonate platform (from internal to the slope), discuss the relationship between sedimentary discontinuities and early acquisition of porosity, give some palaeogeographic trend for the main environmental belts in relation with the structural framework and discuss the impact of the facies distribution around the Bab basin. To achieve these objectives, an integrated workflow using a mixed static and dynamic approach was used in order to constrain the reservoir architecture. A huge database was studied, including several key sections and more than 60 vertical wells drilled in the Urgonian aquifer. Some wells were logged (GR, resistivity, borehole images). This “rock” database was completed by several dynamical data including 40 well tests and the surveying of 8 springs for one year. A biostratigraphic framework was updated in order to discuss correlations between the different studied areas, in agreement with the regional background knowledge (Vercors and Provence areas). A reliable faciological model and an integrated sequential framework were built based on a detailed thin section analysis.