An overlooked play? Structure, stratigraphy and hydrocarbon prospectivity of the Carboniferous in the East Irish Sea–North Channel basin complex
Published:January 01, 2019
T. C. Pharaoh, C. M. A. Gent, S. D. Hannis, K. L. Kirk, A. A. Monaghan, M. F. Quinn, N. J. P. Smith, C. H. Vane, O. Wakefield, C. N. Waters, 2019. "An overlooked play? Structure, stratigraphy and hydrocarbon prospectivity of the Carboniferous in the East Irish Sea–North Channel basin complex", Paleozoic Plays of NW Europe, A. A. Monaghan, J.R. Underhill, A.J. Hewett, J.E.A. Marshall
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Seismic mapping of key Paleozoic surfaces in the East Irish Sea–North Channel region has been incorporated into a review of hydrocarbon prospectivity. The major Carboniferous basinal and inversion elements are identified, allowing an assessment of the principal kitchens for hydrocarbon generation and possible migration paths. A Carboniferous tilt-block is identified beneath the central part of the (Permian–Mesozoic) East Irish Sea Basin (EISB), bounded by carbonate platforms to the south and north. The importance of the Bowland Shale Formation as the key source rock is reaffirmed, the Pennine Coal Measures having been extensively excised following Variscan inversion and pre-Permian erosion. Peak generation from the Bowland source coincided with maximum burial of the system in late Jurassic–early Cretaceous time. Multiphase Variscan inversion generated numerous structural traps whose potential remains underexplored. Leakage of hydrocarbons from these into the overlying Triassic Ormskirk Sandstone reservoirs is likely to have occurred on a number of occasions, but currently unknown is how much resource remains in place below the Base Permian Unconformity. Poor permeability in the Pennsylvanian strata beneath the Triassic fields is a significant risk; the same may not be true in the less deeply buried marginal areas of the EISB, where additional potential plays are present in Mississippian carbonate platforms and latest Pennsylvanian clastic sedimentary rocks. Outside the EISB, the North Channel, Solway and Peel basins also contain Devonian and/or Carboniferous rocks. There have, however, been no discoveries, largely a consequence of the absence of a high-quality source rock and a regional seal comparable to the Mercia Mudstone Group and Permian evaporites of the Cumbrian Coast Group in the EISB.
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Paleozoic Plays of NW Europe
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Despite successful production from Carboniferous and Permian reservoirs in the southern North Sea and onshore Netherlands and Germany, Paleozoic hydrocarbon plays across parts of NW Europe remain relatively under-explored both onshore and offshore. This volume brings together new and previously unpublished knowledge about the Paleozoic plays of NW Europe to describe significant additional exploration opportunities outside and below existing plays.
The volume contains papers on Paleozoic plays in the North Sea, Irish Sea, onshore UK, France and Switzerland. They highlight how improvements in seismic data quality and the availability of previously unpublished well datasets form the basis for improved understanding of local to regional interpretations that move forward from generalized basin development models. The improved structural trap and source rock basin definition feeds to better constrained, locally variable burial, uplift, maturation and migration models. Particularly notable are the significant mapped extents and thickness of Paleozoic source, reservoir and seal rocks in areas previously dismissed as regional highs and platforms.