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Formation of bitumen in the Elgin/Franklin complex, Central Graben, North Sea: Implications for hydrocarbon charging

Meredith, Will; Uguna, Clement N.; Snape, Colin E.; Carr, Andrew D.; Scotchman, Iain C.

Formation of bitumen in the Elgin/Franklin complex, Central Graben, North Sea: Implications for hydrocarbon charging Thumbnail


Clement N. Uguna

Professor of Chemical Technology & Chemical Eng

Andrew D. Carr

Iain C. Scotchman


The Elgin/Franklin complex contains gas condensates in Upper Jurassic reservoirs in the North Sea Central Graben. Upper parts of the reservoirs contain bitumens, which previous studies have suggested were formed by the thermal cracking of oil as the reservoirs experienced temperatures >150°C during rapid Plio-Pleistocene subsidence. Bitumen-stained cores contaminated by oil-based drilling muds have been analysed by hydropyrolysis. Asphaltene-bound aliphatic hydrocarbon fractions were dominated by n-hexadecane and n-octadecane originating from fatty acid additives in the muds. Uncontaminated asphaltene-bound aromatic hydrocarbon fractions however contained a PAH distribution very similar to normal North Sea oils, suggesting that the bitumens may not have been derived from oil cracking.
1-D basin models of well 29/5b-6 and a pseudowell east of the Elgin/Franklin complex utilise a thermal history derived from the basin’s rifting and subsidence histories, combined with the conservation of energy currently not contained in the thermal histories. Vitrinite reflectance values predicted by the conventional kinetic models do not match the measured data. Using the pressure-dependent PresRo® model, however, a good match was achieved between observed and measured data. The predicted petroleum generation is combined with published diagenetic cement data from Elgin/Franklin to produce a composite model for petroleum generation, diagenetic-cement and bitumen formation.

Journal Article Type Article
Acceptance Date Jan 24, 2019
Online Publication Date Jan 29, 2019
Publication Date Jan 29, 2019
Deposit Date Feb 18, 2019
Publicly Available Date Feb 18, 2019
Journal Geological Society, London, Special Publications
Print ISSN 0305-8719
Electronic ISSN 2041-4927
Publisher Geological Society
Peer Reviewed Peer Reviewed
Volume 484
Pages SP484-2017-344
Keywords Geology; Ocean Engineering; Water Science and Technology
Public URL
Publisher URL


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