Alastair Haddow

Sponsor: Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme (PIP) - see: http://www.pip.ie

PhD Project:

Investigation of the palynology, stratigraphy and palaeogeography of Carboniferous rocks in western Irish offshore basins

Supervisor: Geoff Clayton

Project Summary:

During the Carboniferous Period (359-299Ma) and prior to the formation of the Atlantic Ocean, Western Europe and North America belonged to a single, equatorial continent. Large volumes of organic plant matter were deposited forming coal-rich stratigraphic horizons. Mesozoic rifting and opening of the Atlantic led to the development of the Western Irish offshore sedimentary basins (Porcupine, Slyne and Erris) with burial and maturation of the organic rich Carboniferous rocks leading to the generation of natural gas. Hydrocarbon exploration offshore Western Ireland has resulted in a number of gas discoveries, the largest to date being the Corrib field of 1996.

This research project aims to utilise recent advances in palynology and seismic based sequence stratigraphy to:

1. Revise the current bio- and lithostratigraphic classification for Carboniferous rocks in offshore Western Ireland basins and correlate with the Carboniferous succession offshore Eastern Canada; Interpret the palaeogeography and variation in depositional environments of offshore Western Ireland and the North Atlantic during Carboniferous times; and,
2. Identify potential hydrocarbon source rock intervals, reservoirs and seals within the offshore Western Ireland Carboniferous section.

The research will first reappraise the existing lithostratigraphic and biostratigraphic (palynological) frameworks of the offshore Western Ireland Carboniferous that were established over 15 years ago using samples and data from 17 exploration wells that penetrated the offshore Carboniferous succession. The new research will utilise a revised Carboniferous miospore zonation and the palynological analysis of ca. 100 new samples.Carboniferous palaeogeographic reconstructions of the North Atlantic region will be based on seismic sequence stratigraphic and lithostratigraphic data analysis integrated within the revised palynostratigraphic framework. Sequence stratigraphic analysis of relevant seismic surveys will enable packages of time related sediments to be correlated on a regional scale. Seismic event geometry, palynofacies analysis and sedimentological data from well reports will be used to distinguish regional variations in sedimentation and depositional environment.The palaeogeographical analysis will further current investigations into the relationship between late Carboniferous Irish offshore, Scandinavian and Iberian marine sediments, testing the hypothesis that a seaway linked the Western Irish offshore to Norway and/or Scandinavia during the late Carboniferous.A further research aim is the correlation of the revised offshore Ireland Carboniferous palynostratigraphy with that of Eastern Canada. Carboniferous miospore assemblages of similar composition are present in both regions, suggesting a possible transatlantic stratigraphic correlation.

Finally, due to its economic importance as a source rock for natural gas production, palynological analysis of well samples will be used to identify potential source rock intervals within the offshore Ireland Carboniferous succession. Sedimentological data analysis and sequence stratigraphy will be utilised to recognise potential reservoir and sealing lithologies. Observations from Irish offshore basins will be compared with those from Canadian offshore basins. The project deliverables will provide valuable information for future gas exploration and development offshore Ireland and further the current understanding of the development of the North Atlantic region during the Carboniferous.