CO2 storage potential of contourite channels – Laboratory studies on geochemical reactions

Contourite sandstones exhibit high lateral continuity, moderate to high porosity (depending on diagenetic overprint), and are typically overlain by fine-grained marls, making them promising candidates for subsurface CO₂ storage. This study investigates contourite channel deposits of late Miocene age that outcrop in the Rifian Corridor (northern Morocco). A fine-grained, bioclastic–siliciclastic sandstone and a medium- to coarse-grained sand representing potential reservoir materials were selected for controlled CO₂–rock interaction experiments.CO₂ exposure tests were conducted in a batch reactor at 8 MPa and 40 °C for 30 days. Textural and pore-space changes were assessed through comparative SEM imaging, and bulk-rock and brine chemical compositions were analysed before and after exposure. The first reservoir sample experienced only minor dissolution features and limited particle detachment. In contrast, the fine-grained reservoir candidate underwent pronounced physical disintegration during CO₂ exposure. Chemical alteration was modest in both lithologies, expressed mainly as slight increases in dissolved ion concentrations in the brines.These results highlight contrasting mechanical responses of contourite channel facies to CO₂ exposure and underscore the importance of lithological variability when evaluating contourite systems for CO₂ storage applications.This research was conducted within the ALGEMAR Project (Ref. PID2021-123825OB-I00), funded by the Plan Nacional of Spanish Ministry of Science and Innovation