Carboniferous depositional systems of the Southern North Sea

Abstract

A study of the Carboniferous sequences in some 93 wells from onshore England to onshore Netherlands has provided data on variations of depositional styles, sandbody dimensions and petrographic composition, both through time and, in the Upper Carboniferous, across the basin. Three separate sources of sediment input are recognized: a dominant, and petrographically fairly uniform, north to southflowing sediment distribution system which shows a general southerly decrease in channel sandbody size and abundance; a less important source on the Anglo-Brabant Massif; and a probable third source in SE Holland.Through time, there was a progressive increase in petrographic maturity, while channel sandbody percentages decrease to a minimum in the Westphalian B and then begin to increase again through the Westphalian C and D. Compared to the UK onshore, there is a close similarity between the Dinantian successions on the Mid North Sea High and in the Northumberland Basin and marked contrasts in sedimentation styles between the offshore Red Beds sequences in the centre of the basin and those seen onshore in the English Midlands. Regional mapping of channel sandbody statistics for different stratigraphic intervals could guide future exploration efforts towards areas with greater reservoir potential.The nature of the Carboniferous sequences and their distribution beneath the Southern North Sea have been reviewed by Leeder and Hardman (1990) and Besly (1990). These reviews are very valuable but are, of necessity, rather generalized. The increasing interest in Carboniferous sequences as exploration targets requires a more systematic evaluation of the nature and dimensions of Carboniferous sandbodies and this paper describes results of a study which attempted to fulfil that requirement.The principal aims of the study were: (1) to identify from what sources and through what distribution systems sediment was introduced; (2) to establish the main depositional styles which operated through the Carboniferous; (3) to assess how the distribution of these styles changed through time; (4) to distinguish different types of sandbodies present and to assess the likely dimensions of these potential reservoirs through both direct measurement of thickness and comparison with empirical analogue data from outcrop.The study was based on some 93 wells, extending from East Gelderland in the Netherlands to Tyneside, northeast England (Fig. 1). Most of the wells were for hydrocarbon exploration, although those in East Gelderland were drilled as part of a coal exploration programme. Eleven of the wells used in the study were made available by the operators on a confidential basis. The remainder were released wells, the distribution of which is shown in Fig. 1.For each well, geophysical logs were examined and operators' biostratigraphic reports were assessed. In addition, all available core was re-described and sandstones sampled for petrographic examination which was undertaken primarily to identify differences in provenance. Consequently, the material ...

Provenance of late Carboniferous sandstones in the Pennine Basin (UK) from combined heavy mineral, garnet geochemistry and palaeocurrent studies

“…12). These highs are thought to have subsided more slowly than the surrounding basins and to have accumulated thin coverings of Carboniferous sediment (Collinson et al, 1993;Fraser and Gawthorpe, 2003). However, the heavy mineral data suggest that there must have been, at the very least, enough exposure to allow erosion and recycling of pre-existing sediments.…”

Sequence stratigraphy of the Westphalian in the northern part of the Southern North Sea

“…Collinson et al (1993) suggest that facies and depositional styles in the Westphalian in the offshore are similar to those encountered onshore in the UK. They record that the offshore Westphalian A and early Westphalian B is characterized by stacked fluvial sandstones analogous to the deposits of the Durham coalfield (e.g.…”

Carboniferous petroleum systems around the Mid North Sea High, UK

“…Major, stacked channel sandbodies and palaeovalley fills within the Fell Sandstone, Scremerston, Yoredale and Millstone Grit formations have been documented previously as potential reservoir intervals (Collinson and Jones, 1997;Collinson, 2005;Jones, 2007;Maynard and Dunay, 1999). Using onshore exposures of age-equivalent strata (e.g.…”

“…The spatially extensive Visean-Namurian succession subcrops at the base Permian unconformity on the southern margin of the 'Mid North Sea High' (Collinson, 2005) and has been seismically interpreted in Quadrants 29,37,38 and 39 of the UK Continental Shelf (UKCS) (Hay et al, 2005;Milton-Worssell et al, 2010), leading to suggestions of a potentially prospective petroleum system in these lower-middle parts of the Carboniferous succession (e.g. Milton-Exploration Roadmap (21CXRM) Palaeozoic Project (2014Project ( -2016 contributed to increased exploration activity of the 'frontier' MNSH region.…”