Interrelations of the petrophysical, sedimentological and microstructural properties of the Oolithe Blanche Formation (Bathonian, saline aquifer of the Paris Basin)

The Paris Basin seems a suitable location for CO 2 capture and storage given both the amount of CO 2 produced and the availability of depleted fields and deep saline aquifers. This study investigates the petrophysical properties in relation to the sedimentary and diagenetic environment of the Oolithe Blanche Formation (Middle Jurassic), a deep saline aquifer considered a potential candidate for CO 2 storage. Because of the scarcity of core data in the Paris Basin, our investigation was based on the study of field analogues in the south-east part of the Paris Basin. The Oolithe Blanche Formation (Bathonian) is 70–80 m thick. Eighteen oriented blocks were collected from three outcrops selected for the different sedimentological facies identified in the formation. Their petrophysical properties were measured: porosity, pore size distribution derived from mercury injection tests, permeability and capillary imbibition parameters. The sedimentary and diagenetic facies were defined by using optical microscopy coupled with image analysis on thin sections and SEM. The Oolithe Blanche Formation is composed of oolitic and bioclastic limestones, deposited in a shallow marine setting. Three main sedimentological facies were defined: the oolitic shoal facies, the tide dominated facies and the prograding oolitic facies. They exhibit subtle variations in composition and in the distribution of carbonate textures. Porosity, measured using the water saturation triple weight method, ranges from 6% to 34%. Permeability values are low, between 0.1 mD and 9 mD. The data from mercury intrusion porosimetry show that the distribution of the pore throat diameter is either unimodal (microporosity only) or bimodal (macro- and microporosity). Microporosity is intraparticle (intraooid) and macroporosity is interparticle and is related to dolo–dedolomitization. Variations of petrophysical parameters can be explained by the microstructure. Now, these latter results calibrated by studying field analogues must be extended to borehole data and core data to optimize our knowledge of the deep saline aquifer of the Oolithe Blanche Formation. Without such investigations, it will be impossible to estimate the suitability of this deep saline aquifer for CO 2 storage.