Lower to Middle Carboniferous shales represent the most prominent shale play in the UK. In the East Midlands region, the Widmerpool Gulf contains proven oil-prone Carboniferous source rocks that sourced producing petroleum fields and seep bitumens such as at Windy Knoll in Derbyshire. This study is based upon new analyses of samples obtained from the British Geological Survey (BGS) for the Duffield borehole that was drilled in the Widmerpool Gulf. These new results, in conjunction with available legacy data, were used to determine the organic geochemical and mineralogical properties of the Upper Carboniferous sediments intersected in this well and for subsequent comparison against the criteria characteristic of producing North American shale gas plays.
By projecting stratigraphic thicknesses from a BGS isopachyte map of the basin, an estimate of post-Variscan burial and erosional events were predicted. Based upon the Duffield borehole data, a 1D model of its burial history was built using Zetaware's Genesistm software. This basin modelling established the thermal history of the preserved borehole section with results indicating is likely potential for an unconventional oil and gas play in the Widmerpool Gulf.
Basin modelling with associated vitrinite reflectance data suggest the burial history of the Widmerpool Gulf involved 1150m (1.15km) and 2760m (2.76 km) of erosion for the Paleozoic and Tertiary events respectively. The modelled scenarios propose that the main maturity for the Widmerpool Gulf was during the Upper Cretaceous maximum burial event, which overprinted any maturity from the minor burial during the Variscan
The Duffield Borehole was drilled by the British Geological Survey (BGS) in 1966–67 (Aitkenhead, 1977) to sample the preserved Carboniferous section on the northern flank of the paleo-geographic feature termed the Widmerpool Gulf (Figure 1). Following rifting, Carboniferous basin evolution in central and northern England was influenced by north-south Variscan compression which resulted in reactivation of older basement faults and lineaments (Fraser and Gawthorpe, 1990). During the Visean-Namurian marine transgression, deep water basinal facies mudstones were deposited in the Widmerpool Gulf, while the relatively shallow water East Midland Shelf to the northeast and Wales-London-Brabant Massif to the south accumulated sands and carbonates. The Duffield borehole is located north of Derby, and about 1.2 km south of the village of Duffield, Derbyshire UK (Lat 52.97579167N: Long −1.49094611E). It is the Visean-Namurian mudstones which form a potential target for shale oil or shale gas exploration.