Maturity modelling of well 110/07b- 6

This report details one-dimensional (1D) maturity modelling of well 110/07b- 6 in the Carboniferous rocks of the UK Irish Sea for the 21CXRM Palaeozoic project. The aim of the maturity modelling was to predict when the source rock reached the oil and gas maturity windows, and predict the timing of generation of potential hydrocarbons. Unravelling the burial and thermal history of the Irish Sea has entertained geologists for over 25 years and been subject to numerous studies (e.g. Cowan et al., 1999; Quirk et al., 1999; and references therein). This study specifically focusses on the 1D burial and thermal modelling of well 110/07b- 6 in the East Irish Sea area using BasinMod™ (Platte River Associates software). The regional Palaeozoic stratigraphy is described in Wakefield et al. (2016), the regional source rock geochemistry from legacy well reports is described in Vane et al. (2016) and the regional petroleum system analysis in Pharaoh et al. (2016b). Well 110/07b- 6 was chosen from a restricted number of potential wells as it contained the most comprehensive collection of geochemical data collected from released legacy well reports. The modelled maturity curve with depth was matched to best fit both measured maturity data (vitrinite reflectance) and calculated maturity data (calculated from RockEval Tmax values). A Variscan uplift of 700 m was modelled, as well as a 150 m Cimmerian uplift event and a two-stage Cenozoic uplift of 650 m in the Palaeocene and 450 m from the Eocene to recent. The uplift amount falls to the lower end of the published 1-3 km Cenozoic uplift estimates, and was modelled with a base heat flow of 50 mWm-2 increasing to a 70 mWm-2 peak during the Palaeocene. Deepest burial was reached in the early Cenozoic and the base of the drilled section of Bowland Shale Formation reached main gas generation (base of formation not reached). Main oil and gas generation for the Millstone Grit Group occurred equally in the Jurassic, Cretaceous and early Cenozoic. Oil and gas generation for the Bowland Shale Group occurred mainly in the late Mesozoic and early Cenozoic, with minor oil generation also in the Late Carboniferous. Both the Millstone Grit Group and Bowland Shale Formation in this well have fair source potential remaining. The use of one well for a regional scale study has its obvious limitations. The well chosen is fairly representative of the southern area of the East Irish Sea Basin (EISB) hydrocarbon province, south of the large Morecambe fields and near to the recently discovered Conwy Field (Figure 1). For a more complete understanding of the Solway and Peel-Manx basins to the north-west and Quadrant 109 (Figures 1, 3), geochemical sampling of well cuttings and/or core would be required.