Characterization of the Miocene Castellón Sandstones Formation in the Western Mediterranean as a potential geological carbon storage site

In response to the growing interest in decarbonizing Europe's industrial hubs, this study examines the potential of the Miocene Castellón Sandstones Formation in the Valencia Trough for geological carbon storage. The proposed storage unit is represented by a siliciclastic succession formed mainly by sandstones and sandy heterolithics, in the Ebro Delta offshore area of the Valencia Trough. The sedimentological characterization of this succession, based on the study of a cored section from Amposta Marino C-2 well, has allowed to identify up to eleven lithofacies, comprising sandstones, heterolithics, calcarenites and carbonate breccias. These lithofacies can be grouped in six facies associations, including: 1) fluvial channel, 2) delta front proximal mouth bar, 3) delta front distal mouth bar, 4) proximal prodelta, 5) distal prodelta and 6) shelfal lag. The seismic stratigraphic analysis carried out throughout the study area points out to the additional presence of delta plain deposits in the northeastern sector of the study area, approximately at 30 km from the present-day Ebro delta shoreline. Based on the interpretation of these facies and seismic facies associations, the proposed depositional model consists of a river dominated, wave-influenced delta for the proto-Ebro deltaic system during the Late Miocene in the Valencia Trough. This study proposes that this sand-prone succession is presented as a good candidate for geological carbon storage in the study area, considering its proximity to the onshore Tarragona's industrial complex and its optimal reservoir characteristics. Additionally, the thick succession of the Ebro Shales also shows great potential as a vertical and lateral seal of the underlying Castellón Sandstones Formation.