Sedimentary and Diagenetic Models of Upper Cretaceous to Paleocene Carbonate Formations, Aquitaine Basin, France: Prediction of Their Reservoir Properties—Part II

Toullec, Renaud¹, Adrian Cerepi¹, Philippe Razin¹, Louis Humbert¹, Gildas Lageat², Nicolas Labat², Christophe Rigollet², Serge Galaup¹, Brigitte Spiteri¹ (1) Université Michel de Montaigne Bordeaux III, Pessac, France (2) Gaz de France, Saint Denis La Plaine, France

The multiscale analysis of Upper Cretaceous to Palaeocene carbonate formations from basin scale to pore scale of Bas-Adour sub-basin (Aquitaine Basin, France) is based on dif­ferent specific tools : seismic, well logging, petrophysics, thin and polished sections. All these data have been integreted in a carbonate foreland basin model under halocinetic con­trol. This study intends to unlock the sedimentary and diagenetic record, especially the dolomitized bodies distribution, so as to predict reservoir properties. The cores drilling analysis allows us to display the evolution of at least two carbonate platforms, during Coniacian/Turonian to Campanian and the other one during Danian to Upper Thanetian/Ypresien. During this period, available space seems not to be or slightly affected by salt movements relative to the precinematic form of the seismic reflectors. These carbon­ate platforms are characterized by calcarenite deposits with emergences surfaces during Palaeocene, leading to an important primary porosity and permeability. These deposits are separated by fine grained fabrics conducting to cover facies development. The diagenetic imprint differ between high position where formations are intensily dolomitized with a com­plex diagenetic history permitting high secondary porosity development and low positions where sedimentary record is preserved, especially for Palaeocene sediments. Upper Cretaceous sediments are not so affected and their diagenetic history is not so complex. Like this, high positions are better reservoirs than lower ones. Moreover, an Upper Cretaceous to Ilerdian field analogue has been chosen in the high subsident Tremp basin (South Pyrenees) in order to understand the impact on the diagenetic fabric of high frequency transgressive/regressive cycles with periodic emergences.