Tectono-stratigraphic Evolution and Frontier Exploration Screening of the South Western Approaches Basins

The Western Approaches Trough is a failed rift situated on the north-east Atlantic Margin. Rifting initiated in the Permian, reactivating inherited structural weaknesses following the culmination of the Variscan orogeny. Petroleum exploration has yielded poor results thus far, with numerous exploration wells reporting hydrocarbon shows but not of commercial volume. Seismic (2D) and well data have been analysed to develop a tectono-stratigraphic model for the evolution of the WAT, based primarily on seismic mapping and facies analysis. The model has then been used to identify and assess the various petroleum systems elements (sources, reservoirs, seals and traps) and the timing of key tectonic events. Organic-rich marine shales of the lower Jurassic Lias Formation provide the principal source rock for the region. Basin modelling results indicate maturity across the southern WAT, with a primary phase of expulsion occurring in the Early Cretaceous. Potential reservoirs and seals are present at several levels within the stratigraphic succession. Most of the plays are reliant on structural traps developed during two phases of inversion, at the end of the Jurassic and during the Miocene. Composite Risk Segment mapping ultimately reveals the exploration sweetspots. Seal capacity is the primary risk due to the complex tectonic history.