Petroleum System Elements Reservoir 2 Trap & Seal Source Gas & Oil Migration Depth (km) Oil & Gas Generation Window SLIDE 7 Here is a cross-section through a sedimentary basin The ‘granite’ pattern represents non-sedimentary (basement) rocks There are ~12 major depositional unit (layers) Someone, a basin modeler, has predicted the depths at which: Mostly oil would be generated – the ‘oil window’ Only gas would be generated – the ‘gas window’ Where no more HC would be generated – below the gas window Now all we have to do is: Figure out where the source rocks are. Identify potential reservoir units Locate potential traps that are capped by a sealing lithology And hypothesize HC migration pathways Then we can predict where there are oil and gas fields just waiting to be discovered – simple! If we are working a basin in which fields have been discovered, we can ‘reverse engineer’ the HC system For example, if we know oil is in the shallow reservoir on the right, we know HC migrated into it somehow As shown by the blue arrow, we might call upon HC migration up the fault This would connect our ‘kitchen’ to our known field Of course we have to consider the 3D basin geometry – not a single cross-section 4 Gas Generation Window 6 No More HC Generation 8 Courtesy of ExxonMobil L 2 - Basics of Prospecting