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