Structural framework and fault seal prediction of the central slyne basin prospect, Irish Atlantic margin

Abstract Predicting fault seals in prospective structural zones is crucial for evaluating the sealing capacity of hydrocarbon compartments. It is essential for assessing a seal's ability to retain hydrocarbons during their migration into reservoir systems. The Central Slyne Basin Prospect (CSBP), a geological trap within a horst block system, remains underexplored. This study aims to predict hydrocarbon column heights (H) in a Lower Jurassic play (Toarcian interval) within structural traps in the northern Central Slyne Basin by constructing a detailed structural framework. The CSBP, central to the basin's geometry, is the primary focus. Utilizing 3D seismic, well, and checkshot data, we performed seismic surface and fault interpretation of the Lower Jurassic play. Our approach integrates fault juxtaposition analysis, Shale Gouge Ratio (SGR) plotting, and permeability prediction to evaluate fault seal effectiveness and hydrocarbon migration potential. The results reveal the significant influence of fault dynamics on sealing behavior. Analyses of 3D fault plane juxtaposition, permeability plots, and SGR distribution indicate that the CSBP is highly sealed from surrounding structural closures, with an SGR of 40% across most of the fault plane. However, low SGR values (< 10%) near the fault tip may act as fluid migration pathways into the CSBP. The estimated hydrocarbon column height in the central prospect area is approximately 200 m, given the average SGR and a maximum burial depth of 3.5–4 km. These findings underscore the importance of detailed fault seal analysis for understanding reservoir behavior and predicting hydrocarbon migration in complex basins.