Thermal evolution and resources of the Bowland Basin (NW England) from apatite fission-track analyses and multidimensional basin modelling

Abstract

Once highlighted for having significant shale gas resource potential, the Bowland Basin has been at the centre of both scientific and political controversy over the last decade. Previous shale gas resource estimates range from 10^3 - 10^1 TCF. Repeated events of induced seismicity following hydraulic fracturing operations led to an indefinite government moratorium and abandonment of operations across the mainland United Kingdom. We use apatite fission track analyses to investigate the magnitude and timing of post-Triassic uplift and exhumation. Results indicate maximum paleo temperatures of 90 - 100oC were reached in the stratigraphically younger Sherwood Sandstone. We combine paleotemperature predictions to constrain paleo heat flow and erosion in regional basin models for the first time. Our results indicate variable maximum Late Cretaceous paleo heat flow values of 62.5 - 80 mW m^2 and the removal of 800 -1500 m of post-Triassic strata at wells across the basin. Regional 2D basin modelling indicates a gas in-place estimate of 131 +/- 64 TCF for the Bowland Shale. This reduces to a resource potential of 13.1 +/- 6.4 TCF, assuming a recovery factor of 10%. These values are significantly lower than previous resource estimates and reflect the highly complex nature of the Bowland Basin and relatively unknown history of post-Triassic uplift, exhumation, and erosion.