Sedimentological, mineralogical and diagenetic controls of particle transport in the Albian sands aquifer of the Paris Basin

The Albien aquifer constitutes a deep reservoir located under the chalk of the Parisian basin composed of unconsolidated clay-sandstone deposits and is considered as a strategic resource for Ile de France in the event of long-term unavailability of classic resources. The deposits present a complex sedimentary architecture at the scale of the sedimentary system and a complex distribution of clayey heterogeneities at the scale of the reservoir, both disturbing the fluid flow within the aquifer. At small scale, the mineralogical composition of the deposits constitutes a heterogeneity having consequences on the mobility of the particles within the reservoir, and on the chemical transformations which result from interactions between fluids and surrounding rocks. It is thus crucial to characterize the mineralogical composition that make up the aquifer. The spatial and temporal variability of the elements entering the initial composition of a sediment must also be specified because this induces mineralogical heterogeneities pre-existing to diagenesis, at the origin of petrophysical heterogeneities in the reservoir.
The task given to the PhD student is to identify and prioritize the key sedimentary, mineralogical and/or diagenetic parameters which have an influence on the behavior of the aquifer under constraints linked to increased exploitation, and at what scales this influences the system behavior. An understanding of the sedimentary system at the basin scale by correlation of sedimentary units will be necessary to constrain the architecture of the system, and thus determine the nature and location of the main types of reservoirs and their characteristics. This phase of understanding will be carried out at the basin scale and at the reservoir scale. A final phase consists of integrating these key parameters into a modeling approach considering the proxies identified at different scales. Stratigraphic modeling will first help at testing the different scenarios and to propagate in 3D the sedimentary geometries and their properties (mineralogical content, proportion of clay, etc.). The nature of the Albian reservoirs will then be reconstructed by establishing "rock-types" integrating the different properties (sedimentary facies, mineralogical content…), and will finally help at downscaling the properties at the reservoir scale in order to assess the fluid flow behaviour that depend on the reservoir characteristics (flow velocities control the transport and the capture of fine particles through the porous network by mechanical filtration and therefore inducing changes in permeability).

Keywords: Albian, sands, aquifer, sedimentology, mineralogy, stratigraphic modelling

• Academic supervisor    Professor PATRIER Patricia, IC2MP, Poitiers University
• Doctoral School    Doctoral school n° 614: Chemistry, Ecology, Geosciences, Agrosciences (Théodore Monod), https://www.u-ldevinci.fr/cega/
• IFPEN supervisor    PhD, DESCHAMPS Rémy, research engineer in geosciences, Sciences of surface and sub-surface department, remy.deschamps@ifpen.fr
• PhD location    IFPEN, Rueil Malmaison, France, Poitiers university, Poitiers, France
• Duration and start date    3 years, starting in fourth quarter 2022
• Employer    IFPEN, Rueil Malmaison, France
• Academic requirements    University Master degree geosciences
• Language requirements    Fluency in French or English, willingness to learn French