The timing of hydrocarbon generation from Carboniferous source rocks and the lack of evaporites within the Triassic Mercia Mudstone Group seal sequence have contributed significantly to the lack of exploration success in the Triassic Sherwood Sandstone play of the Central Irish Sea Basin. Apatite fission-track analysis (AFTA(R)), combined with vitrinite reflectance data from the Central Irish Sea Basin and adjacent areas, indicates that maximum burial and heating of the Carboniferous section was achieved by the Early Cretaceous. The long residence period for trapped hydrocarbons generated in the Early Cretaceous, combined with the ineffectiveness of the Mercia Mudstone Group seal caused by the absence of annealing halites and the presence of thief sandstones, led to hydrocarbon loss through trap breaching during subsequent tectonic events. In contrast, maximum burial of Carboniferous source rocks in the central East Irish Sea hydrocarbon province was achieved in the Late Cretaceous-early Tertiary, giving a shorter residence period for generated hydrocarbons. The combination of a short residence period and the presence of a halite-bearing Mercia Mudstone seal sequence significantly improved hydrocarbon retention within the Sherwood Sandstone reservoir. If traps were episodically breached during the late Tertiary, they were recharged by the inversion process, which caused gas expansion, spill from charged traps, and lateral remigration of hydrocarbons updip. The inversion-related pressure drop also caused retrograde condensate dropout from gas accumulations to provide a supply of late condensate for preferential spm and remigration.