Integrated sedimentological, micropaleontological, and structural data of Miocene limestones in Cicuco and El Difícil fields (Lower Magdalena Valley, Colombia): Methodology and Implications for CO2 storage potential in Northwestern South America

The Lower Magdalena Valley Basin (Colombia, northwestern South America) hosts high-potential Lower Miocene carbonate reservoirs that may represent suitable candidates for geological CO 2 storage; however, their sedimentary characteristics and controlling factors remain poorly understood. This study integrates sedimentological, petrographic, micropaleontological, and seismic analyses of 360 m of core and 3,239 km of seismic data to characterize the depositional architecture, diagenetic evolution, and structural framework of these limestones, and to provide a geological basis for evaluating their CO 2 storage potential. Sedimentary and facies analysis reveal reef complexes (framestone, bafflestone, rudstone) restricted to NE-SW trending paleo-highs. Reef architecture varies between fields: Magangué-Cicuco preserves back-reef to fore-reef transitions, while El Difícil exhibits complete reef systems with lateral variation to patch reefs. Diagenetic evolution progressed from marine eogenesis through burial mesogenesis to late-stage telogenesis, creating mainly low to moderate secondary vuggy and biomoldic porosity. Biostratigraphic data constrain the succession to the early–middle Miocene. Finally, probabilistic volumetric assessment yields mean CO 2 storage capacities of 22.6 million metric tons for Cicuco and 13.3 million metric tons for El Difícil under supercritical conditions. These values highlight their strategic importance for national decarbonization planning and long-term energy transition policies. This study provides the first integrated model of subsurface Miocene carbonates in Colombia (NW South America), highlighting the significance of these facies across the southern Caribbean and their potential role in climate mitigation strategies. The findings advance Colombia's technical baseline for carbon capture and storage while highlighting critical data needs for project implementation. • Integrated sedimentology, micropaleontology, and structural data from Miocene limestones. • Reservoir characteristics evaluated for CO 2 storage in Cicuco and El Difícil fields. • Biostratigraphy helped constrain depositional age and sequence stratigraphy. • 2D and 3D seismic analysis to delineate the trap and the carbonate lithologies of the reservoir. • New data improve understanding of CO 2 storage potential in NW South America.