From Rock Record to Subsurface Reservoirs: A Novel Workflow Integrating Surface Analogs and Subsurface Data for Advanced Reservoir Characterization

Abstract This study presents an integrated surface–subsurface workflow to enhance reservoir characterization in heterogeneous aeolian–fluvial systems. High-resolution surface analogs from the Iberian Desert comprising cross bedded aeolian dunes, interdune elements, bounding surfaces, and early calcite concretions, late silica cementation, were used to calibrate and validate subsurface interpretations based on core description, image logs, well logs, XRD, SEM, and thin section petrography. The analog informed framework allowed for the recognition of key architectural elements and diagenetic features that influence reservoir quality, including the spatial arrangement of facies, phreatic flow pathways, and cementation patterns. Subsurface data confirm that aeolian dune facies represent the highest quality reservoir intervals, with excellent porosity and permeability resulting from their well-sorted textures, low clay content, and limited early cementation. In contrast, interdune facies characterized by finer grains, higher clay content, and early-stage calcite and late stage silica cementation, act as lateral and vertical baffles, restricting flow continuity. Fluvial-dominated facies, concentrated in the central to southern part of the field, introduce localized heterogeneity and contribute to stratigraphic complexity and reservoir compartmentalization. A key finding of this study is the identification of early illite grain coatings, which inhibit quartz overgrowths and preserve intergranular porosity in selected dune intervals. This highlights the significant role of early diagenetic processes in controlling long-term reservoir performance. The results underscore the value of integrating surface analogs with subsurface datasets to predict heterogeneity, constrain flow barriers, and refine static models in data-limited environments. The proposed workflow is transferable and provides a powerful tool for guiding well placement, facies modeling, and development strategies in similar continental reservoir settings. The resulting surface and subsurface conceptual models provide a predictive tool for subsurface facies transitions, optimized facies prediction in image-log wells, and constrained depositional geometries in static reservoir modeling.