Introduction to the development, evolution and petroleum geology of the Wessex Basin

Despite containing the largest known onshore oilfield in western Europe, the Wessex Basin hydrocarbon province appears to be extremely limited spatially and it currently only consists of three producing oilfields: Wytch Farm, Wareham and Kimmeridge. The main factor which controls hydrocarbon prospectivity in the area appears to be preservation of oil accumulations originally sited in Mesozoic tilted faultblocks. The extensional palaeostructures of Wytch Farm and Wareham are interpreted to have been charged by upwards migration of oil from mature Liassic source rocks situated across the Purbeck-Isle of Wight fault system in the Channel (Portland-Wight) sub-basin prior to, and unaffected by, either significant effects of intra-Cretaceous (Albian-Aptian) easterly tilting or by Tertiary tectonic inversion. To date, only the small Kimmeridge oilfield, which is situated in the core of a periclinal fold created in response to structural inversion, suggests that any hydrocarbon remigration into younger structural inversion structures has taken place.