Structural and Stratigraphic Control on Reservoir Quality in a Salt-Influenced Jurassic Carbonate Platform: Callovian–Oxfordian of the Toukimt Field, Essaouira Basin, Morocco

The Middle-Upper Jurassic carbonate succession of the onshore Essaouira Basin forms a hydrocarbon play comparable to Atlantic passive-margin systems. In the Toukimt field, gas and condensate have been produced from fractured Argovian dolomites, but reservoir prediction remains difficult because facies variability, diagenetic overprint, and fracture development generate heterogeneities. This study characterizes the sedimentological framework of the Callovian–Argovian (Middle Oxfordian) succession, establishes a sequence-stratigraphic framework, and evaluates the role of halokinesis in controlling accommodation and sediment distribution. The analysis integrates core-based sedimentology, well correlations, high-resolution sequence stratigraphy, and 2D-3D seismic interpretation. Four facies associations have been defined in the ramp system ranging from grain-rich biodetrital shoals to micritic outer-ramp facies. The succession is organized into four depositional sequences (DS1–DS4) showing a shallowing-upward trend with alternating retrogradational flooding and progradational colonization parasequences. Reservoir-prone intervals occur within highstand shoal facies, where depositional texture provides a favorable framework, while fracturing and dissolution enhance petrophysical properties. Seismic data reveal a gravity-driven rollover structure linked to west-dipping listric faulting and salt withdrawal within a long-lived halokinetic system active since the Early Jurassic. Basin-ward growth of the Tidsi diapir generated asymmetric subsidence, indicating that inherited structures, halokinesis, gravity sliding, and diagenesis jointly controlled accommodation, reservoir geometry and quality.