Hydrocarbon generation and migration from Jurassic source rocks in the E Shetland Basin and Viking Graben of the northern North Sea

In the E Shetland basin oil generation began 65 m.y. ago; peak oil generation maturity occurs today at 3250 m and was first reached 40-50 m.y. ago; the oil generation threshold is at 2500 m. Oil migration has probably occurred through oil-wet kerogen laminae and through interconnected large pores aided by low oil/water interfacial tensions. In the Viking graben, the Kimmeridge Clay is at oil-floor maturity below 4500 m; peak oil generation began 55-65 m.y. ago; at 40 m.y. the peak had been passed and gas generation by cracking of oil had begun.