This PhD project focuses on the 3D structure of continental carbonates and fluid transport within the unsaturated zone of the Beauce limestones, a key groundwater reservoir in France. Using high-resolution data from the O-ZNS site (cored boreholes and a 3D-scanned central well), it combines geological, petrophysical, and numerical approaches to investigate how sedimentary heterogeneity affects porosity, permeability, and water flow. The work is structured into three main themes: geological description, physical properties, and integration into a numerical model.