Published:January 01, 2019
A review is presented of the progress of exploration for, and development of, gas fields in the Carboniferous of the UK Southern North Sea in the period since the first significant discoveries were made in 1984. The outcomes of such exploration have generally failed to live up to high initial expectations and exploration targeting of the Carboniferous has declined, the objective having come to be seen by many as difficult and risky. This review includes a summary of the published consensus regarding elements of the Carboniferous petroleum system and discusses the reasons for the decline in interest, which encompass geological complexity, interpretational and operational problems and other non-technical factors. Five areas of Carboniferous petroleum geology are identified in which the currently accepted status quo is open to challenge. More detailed discussion of these leads to the following general conclusions: (1) the distribution of source rocks and their maturation history remains poorly understood, largely as a result of the hitherto unquestioned acceptance that Westphalian coals have acted as the dominant gas source; (2) in many early wells the combination of formation damage and shortcomings in petrophysical data acquisition and evaluation has resulted in a failure to identify potential pay in low permeability formations and an overemphasis on the importance of channel sand bodies as reservoir objectives; (3) the controls on seal capacity and integrity within the Carboniferous succession have been little studied and, as a result, an unduly pessimistic view of intra-Carboniferous sealing potential has prevailed; (4) the distribution of sub-basin depocentres, and thus of basinal shale source rocks and potential hydrocarbon migration paths, remains poorly understood; and (5) conceptual models of the large-scale tectonic history of the Carboniferous basin complex have failed to evolve from early and simplistic rift and sag models, which do not adequately explain the observed distribution of stratigraphic thicknesses and are inconsistent with some published burial histories.
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Paleozoic Plays of NW Europe
CONTAINS OPEN ACCESS
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.