Online Journal for E&P Geoscientists

Bastide, Fanny ^*1; Massonnat, Gérard ²; Virgone, Aurélien ³; Pabian-Goyheneche, Cécile ⁴
(1) Géomodelisation et incertitude, Total, Pau, France. (2) Géomodélisation et incertitude, expertise, Total, Pau, France. (3) Exploration carbonate, Total, Pau, France. (4) Recherche et développement des réservoirs carbonatés, Total, Pau, France.

Urgonian platform carbonates are widespread in the Southeast of France. They were deposited along the northern Tethyan margin during the lower Cretaceous (Barremo-Aptian age) on the Vocontian basin border. They are mostly composed of rudist facies and bioclastic/ooid grainstones. The Urgonian formation of southeastern France can be considered as an analogue for Shu’aiba and Kharaib reservoirs of the Middle East to illustrate and understand the geometries and facies distributions of these reservoirs.

For years, Total has elaborated a work program focused on this thematic. It aims to define a sedimentary model at the basin scale, and to appraise the heterogeneity of inner architecture and petrophysics of Urgonian sequences. Reservoir description and behavior is captured thanks to multi-scales static and dynamic data integrated through a multidisciplinary process including sedimentology, hydrogeology and structural geology.

A huge database was constituted including outcrops and wells studies (facies, fractures, fauna…), electrical and production logging, wells tests, aerial photographs, local springs and aquifer surveys. Several key sections and 17 vertical wells drilled in the Urgonian karstic aquifer were studied. Plus, several dynamics data: 40 well tests and surveys of 13 springs were intepreted.

Thanks to a precise determination and biodistribution study of the main benthic foraminiferas, to a facies description in detail and to a fine study of the parasequences succession, three sequences have been described in the Upper Barremian (Ba3, Ba4 and Ba5) and two in the Lower Aptian (A1 and A2). Thanks to the correlation of the different stratigraphic limits of each sequence, a fan deposit stratigraphic framework has been displayed. The faults delimiting the four fan deposits have been highlighted by the hydrodynamic behavior of the Urgonian karstic formation. Consequently a tilted blocks model of the Urgonian platform has been built. To control this model, fluid flow simulations have been done and compared to the real hydraulic dynamic data.

As a conclusion, this paper presents the tilted blocks model of the Urgonian platform honoring all the static and dynamic data. The impact of the structural framework on deposits has been evidenced by the model and, finally impact of early or late heterogeneities (fracturation, karstification…) has been weighted through fluid flow simulation honoring hydraulic dynamic data.