Dr Stephen Crittenden & colleagues Dr James Cole and Dr Martin Kirk have been involved in exploration for hydrocarbons in the Lower Cretaceous since the early 1980’s. A large amount of geological data has been integrated and analysed. Numerous reports (for Oil company clients) have been the result, parts of which we are proud to say have provided ideas, data and impetus for exploration & discovery in addition to subsequent publications by various authors. Careful analysis is required when dealing with disparate data sets of variable vintage and quality. This care is only achieved by the specialised analysis of the data by committed expert Geoscientists working together as a team.

A preliminary sequence stratigraphy classification of Lower Cretaceous oil and gas accumulations in north

west EuropeStephen Crittenden

Lodestone Geological Services LtdIntroduction

The Lower Cretaceous is a proven hydrocarbon bearing interval in Europe: from the Barents Sea (Ref 15) to the Bay of Biscay.

• Producing hydrocarbons in north west Europe since mid-18th Century - bitumens in Germany from 1750.

• Numerous fields throughout north west Europe including Schoonebeek Field (1943), largest field onshore Europe (>1MMBOIIP).

• Multiple Petroleum Systems and multiple Plays.

• Clastic and carbonate reservoirs (Ref. 1 & 12) .

• Discoveries by design: The SNS, Netherlands, Eire, France & Germany. (Ref. 2, 3 & 9)

• Discoveries by chance: The UK Central & Northern North Sea - the true targets were deeper. (Ref. 5, 6 & 7)

• Goldeneye the first recently ’discovered by design’commercial Lower Cretaceous Field,October 1996, in the UK CNS Aptian Albian sand play. ’Hobby’ the latest (2009) in the CNS Ryazanian - Valanginian sand play.

• Lower Cretaceous potential is concealed within North Sea discovery curves (creaming curves). (Ref. 8)

Can discoveries be ranked by genesis within a sequencestratigraphy model framework? (Ref. 5, 6 & 7)

Transgressive / Highstand Systems Tract

(Eg.Harlingen, Haven, Helder, Helm, Hoorn, Horizon, Kotter, Leeuwarden, Logger, Rijn, Rijswijk Province, Schoonebeek,

Zuidwal)Lowstand Systems Tract

(Eg. Agat, Blake, Cromarty, Britannia, Captain, Chanter, Claymore, Goldeneye, Hannay, Scapa, Saltire, Tiffany)Is such a device viable for modelling the discoveries made to date and indeed useful in the search for the subtle trap?Does a sequence stratigraphy play type classification together with pertinent technical data provide explorationists with suitable analogues for risking purposes?

ASource and collect well & outcrop data.

Collate into data sets.Generation of new data eg. biostratigraphy, biofacies,

palynofacies, sedimentology, petrography.Integration & Interpretation of data sets.

Construction of models and refinement of concepts.

CCollect, document, categorise and tabulate all pertinent

Technical Data for each field & discovery

BCategorise and tabulate the Lower Cretaceous fields within a

Depositional Sequence Stratigraphy Model.Regional Palaeogeographical Mapping.

Petroleum Systems: Source, Reservoir, Trap.Play type, Lead & Prospect mapping.

References1. Copestake, P., Simms, A. P., Crittenden, S., Hamar, G. P., Ineson, J. R., Rose, P. T. and Tringham, M. E. 2003. Lower Cretaceous. 191 – 211. in The Millennium Atlas:

petroleum geology of the central and northern North Sea. Evans, D., Graham, C. Armour, A. and Bathurst, P. (editors and coordinators). Geol Society of London.2. Crittenden, S. 1982. Lower Cretaceous lithostratigraphy north east of the Sole Pit area in the UK southern North Sea. J. Pet. geol.,5/2, 191-202.

3. Crittenden, S. 1987. The Albian Transgression in the southern North Sea Basin. J. Pet. Geol., 10/4, 395-414.4. Crittenden, S. 1991. The Stratigraphy and Reservoir Potential of the Early to Middle Cretaceous of the UKCS (North of 56N). Petroleum Exploration Society of Great Britain

Meeting, London, May 1991. Abstract5. Crittenden, S., Cole, J. M. & Harlow C. J. 1991. The Early to Middle Cretaceous lithostratigraphy of the Central North Sea (UK Sector). J. Pet. Geol., 14/4, 387-416.6. Crittenden, S., Cole, J. M., & Kirk, M. 1997. The Distribution of Aptian Sandstones in the Central and Northern North Sea (UK Sector): A Lowstand Systems Tract Play. Part

1. Stratigraphy, biostratigraphic age determination and genesis of the sandstones. J. Pet. Geol., 20/1, 3-25.7. Crittenden, S., Cole, J. M., & Kirk, M. 1998. The Distribution of Aptian Sandstones in the Central and Northern North Sea (UK Sector): A Lowstand Systems Tract Play. Part

2. Distribution and exploration strategy. J. Pet. Geol., 21/2, 187-211.8. Crittenden, S., Sauar B. E. & Hjaltason F. 1999. The Lower Cretaceous of the Agat Field Area; Comparisons with the UK Central North Sea and implications for exploration

on the Norwegian Continental Shelf. In: Lower Cretaceous of the Central North Sea: Regional Setting and Depositional Architecture, 18-19th May, 1999, Aberdeen -

Petroleum Group of the Geological Society of London. Abstract. 44-44.9. Den Hartog Jager, D. G., 1996. Fluviomarine sequences in the Lower Cretaceous of the west Netherlands Basin: correlation and seismic expression. In: Rondeel, H. E.,

Batjes, D.A. J. & Nieuwenhuijs, W. H. (eds): Geology of Gas and Oil under the Netherlands. Kluwer (Dordrecht): 229 – 242.10. Goodchild, M. W., Henry, K. L., Hinkley, R. J. & Imbus, S. W. 1999, The Victory gas field, West of Shetland. In: Fleet, A. J. & Boldy. S. A. R.. (eds) Petroleum geology of

Northwest Europe: Proceedings of the 5th Conference, 713 – 724. Geol Soc, London.

11. Gulbrandsen, A. 1987. Agat. In: Geology of the Norwegian Oil and Gas Fields. 363-370.12. Jakobsen, F., Ineson, J. R., Kristensen, L., Nytoft, H. P. & Stemmerik, L. 2005. The Valdemar Field, Danish Central Graben:field compartmentalisation and regional

prospectivity of the Lower Cretaceous Chalk play. in Dore, A.G. & Vining, B. A. (eds). Petroleum geology of Northwest Europe & global perspectives. Proceedings of the 6th Conference, 177-186.

13. Skibeli , M., Barnes, K., Straume, T., Syvertsen, S. E., & Shanmugan, G. 1995. A sequnce stratigraphic study of Lower Cretaceous deposits in the northernmost North Sea. 389 – 400. In: Sequence Stratigraphy on the Northwest European margin. Steel, R. J., Felt, V. L., Johannessen, E. P., & Mathieu, C. (editors). Special Publication of

the Norwegian Petroleum Society.

14. Charnock, M. A., Badics, B., Augustson, J.H. & Crittenden, S. 2004. The Distribution of Potential Cretaceous Source Rock horizons in the Norwegian and Barents Sea. In: Arctic Geology, Hydrocarbon Resources & Environmental Challenges (Conference), 24-26th May, 2004, Polar Environmental Institute, Tromsø, Norway. Abstract.

15. Seldal, J. 2005. Lower Cretaceous: the next target for oil exploration in the Barents Sea? In: Dore, A. G. & Vining, B. A. (eds) Petroleum geology: North-West Europe and global perspectives- Proc 6th Petr Geol Conf, Geol Soc, London. 231-240.

AcknowledgmentsCretaceous discussion: colleagues in academia and industry including M. B. Hart, John Gjelberg , Mike Charnock, Brit Sauar, Haydon Bailey. Careful analysis: Jim Cole & Martin Kirk. Inspiration, conversation and assistance : Clara, and the late Prof Jack Black.

For further information

Please contact:

stevecrittenden@yahoo.co.uk. lodestone.geos@yahoo.co.uk

Concluding Remarks

The keys to Risk Reduction encapsulated within the sequence stratigraphy modelling approach are:

•Robust geological models are generated from integrated data sets.

•Ongoing exploration & development will result in new insights.

•Innovation and technological development togetherwith sound geological thinking provide accuracy to predictions, and a better understanding of petroleum systems, plays and prospects.

•The development of regional plays from an enhancedunderstanding of the distribution of Lower Cretaceousreservoir potential sands and carbonates.

•An understanding of potential source rocks both withinthe Lower Cretaceous and from other epochs (Ref 14) and both marine and non-marine.

•The broad holistic approach has a predictive use for exploration.

•A catalogue of field analogues / case studies is used to risk generated leads and prospects within a sequencestratigraphy classification and to reduce uncertainty.

Not surprisingly such an approach adds value to an exploration strategy seeking the subtle stratigraphicaltrap. Recent exploration strategy has concentrated onso-called deep-water plays in ’small areas’ ie the MorayFirth / CNS & West of Shetland, and discretestratigraphical intervals eg. Aptian/Albian & Ryazanian / Hauterivian - Valangian.

This poster introduces results from a research methodology that embraces the prospectivity of the whole Lower Cretaceous interval in the context of North West Europe..

Materials and Method

Results: Lithofacies–clastics (Ref. 6 & 7)

Results : Example, Mid Norway Lower Cretaceous Stratigraphy Model (Ref 14)

Results: Example Field TableResults: Example Field Data Sheet

The Helder Field is one of the Q1 oilfields of the LowerCretaceous of the inverted Broad Fourteens Basin: Helm, Helder, Hoorn & Haven.