Quantifying past subglacial methane storage and emissions under the Fennoscandian ice sheet by means of historic data from hydrocarbon industry

Large-scale methane releases from geological hydrocarbon seepage and the dissociation of subseafloor gas hydrates under shallow waters are important drivers of atmospheric methane concentration increases and global warming. However, the processes, timescales, and fluxes involved in such emissions remain insufficiently constrained. In this study, we redeploy historic oil and gas industry datasets—including well logs, seismic data, as well as reservoir temperature and pressure data—to reveal reservoir-scale methane leakage, storage and release dynamics in the Håkjerringdjupet area at the offshore continental margin of Norway beneath the past Fennoscandian ice sheet during the last glacial maximum.

Our numerical approach considers glacial loading causing the overpressurization of a shallow gas reservoir, driving the expulsion of methane-rich fluids through faulted zones and into subglacial sediments. Glacially-driven pressure increments led to extensive methane hydrate formation within these sediments, storing carbon and significantly improving basal traction. Laboratory shear-strength measurements (Spangenberg et al., 2020), integrated with subglacial hydrate formation modelling (Li et al., 2022, 2023), indicate a minimum hydrate saturation to regulate glacial flow, with the subglacial hydrate system storing ~0.48 Gt of methane in Håkjerringdjupet. During deglaciation, we estimate that ~120–240 Tg of methane released by hydrate dissociation may have reached the atmosphere shortly after the last glacier retreated (about 16,000 years before the present).

Our findings highlight how legacy industry well data and conventional oil and gas technologies can be harnessed to advance understanding of subglacial carbon storage and fluid migration in response to climate change. Our work provides an insightful Pleistocene analogue for studying contemporary ice-sheet-driven methane storage and release, informing strategies for sustainable carbon management in the transition towards net zero emissions.

References:

Li, Z., Spangenberg, E., Schicks, J. M., and Kempka, T.: Numerical Simulation of Coastal Sub-Permafrost Gas Hydrate Formation in the Mackenzie Delta, Canadian Arctic, Energies, 15, 4986, https://doi.org/10.3390/en15144986, 2022.

Li, Z., Chabab, E., Spangenberg, E., Schicks, J. M., and Kempka, T.: Geologic controls on the genesis of the Arctic permafrost and sub-permafrost methane hydrate-bearing system in the Beaufort–Mackenzie Delta, Front. Earth Sci., 11, 1148765, https://doi.org/10.3389/feart.2023.1148765, 2023.

Spangenberg, E., Heeschen, K. U., Giese, R., and Schicks, J. M.: “Ester”—A new ring-shear-apparatus for hydrate-bearing sediments, Review of Scientific Instruments, 91, 064503, https://doi.org/10.1063/1.5138696, 2020.