Prior to contemporary times, direct hydrocarbon indicators (DHIs) such as stains, shows and seeps including mud gas and cuttings gas data had been used for the evaluation of potential hydrocarbon accumulations, maturation and productivity of source rock. Caprock leakage had never been viewed with greater interest than sparingly using these indicators. Modern studies have evolved into employing petrophysics of the caprock section, seismic sections and molecular geochemistry to discern potential mechanism and migration pathways of leaked petroleum via caprocks. In this study, thermogenic wet gas – depth profiles and thermogenic signature – depth profiles derived from cuttings (headspace)/or mud gas data show significant potential as a fast and reliable tool for evaluation of caprock leakage in the North Sea. The study showed that most wells in the North Sea have appreciable amounts of thermogenic wet gas in significant range of caprock sections above the caprock–reservoir interface over petroleum reservoirs, these observations infers leakage and the leaked hydrocarbons could have been delivered into the caprock sections via pressure prone fracture and capillary leakage through network of pores in the matrix of the caprocks.
