Fault seal analysis of the Greater Heidrun area on the Haltenbanken platform, offshore mid-Norway, has been carried out as part of a larger integrated study. Analysis included the construction of fault seal probability maps and shale smear diagrams. Fault seal probabilities were derived from an empirical relationship based on fault throw, reservoir/non-reservoir juxtaposition, and a shale smear factor, thus incorporating a measure of cataclastic gouge thickness and cementation, juxtaposition, and shale smear. A fault seal probability map, showing variations in fault seal probabilities both along the strike of faults as well as from fault to fault, was used to derive likely migration pathways into and through traps at the level of the Top Fangst Group. Shale smear diagrams, which independently corroborate the results of the fault seal analysis, were derived from shale thickness and fault throw. Fault seal probability was calibrated for hydrocarbon column height and differential pressure based on data from adjacent hydrocarbon pools. Fault seal analysis successfully explained the well results and allowed an assessment of undrilled prospects, providing a direction for future exploration. Dynamic fault seal is seen as a characteristic process in this area. Most faults are predicted to be sealing with respect to oil, but non-sealing with respect to gas. The Revfallet Fault Complex was determined as a sealing fault apart from its southern end. This may have been the entry point of overspill from Smørbukk to the Heidrun Platform. Sealing faults on the Heidrun Platform focused hydrocarbons to the Heidrun and Heidrun North areas, and created migration shadows to the east and west of Heidrun North.