2023-12-13 12:11:56
MADRID, 13 Dic. (EUROPA PRESS) –
Millions of cubic meters of methane are trapped beneath the permafrost of the Norwegian archipelago of Svalbard, and scientists have discovered that can migrate under the seal of permafrost and escape.
This is how they publish it in the magazine ‘Frontiers in Earth Science’.
A large-scale release could create a warming cycle that would trigger methane emissions: The warming thaws the permafrost, causing more gas release, allowing more permafrost to thaw and more gas to be released. Since the geological and glacial history of Svalbard is very similar to that of the rest of the Arctic region, These migrating methane deposits are likely present elsewhere in the Arctic.
“Methane is a powerful greenhouse gas,” says Dr. Thomas Birchall of the Svalbard University Center and lead author of the study. “Currently, Leakage below permafrost is very low, but factors such as glacial retreat and permafrost thaw can ‘lift the lid’ in the future.
Permafrost, soil that remains below zero degrees Celsius for two years or more, is widespread in Svalbard. However, it is neither uniform nor continuous. Western Svalbard is warmer due to ocean currents, so the permafrost tends to be thinner and potentially more patchy.
The permafrost in the highlands is drier and more permeable, while that in the lowlands is more saturated with ice. The underlying rocks are often sources of fossil fuels, releasing methane that is sealed by permafrost. However, even when permafrost is continuous, some landforms can allow gas to escape.
The permafrost base is difficult to study due to its inaccessibility. However, over the years, companies seeking fossil fuels have drilled many wells into permafrost. Researchers used historical data from commercial and research wells to map permafrost in Svalbard and identify permafrost gas accumulations.
“Kim, my supervisor, and I looked at a lot of the historical data from the Svalbard wells,” Birchall recalls, “and Kim realized that “There was a recurring theme: gas accumulations at the base of the permafrost.”
Initial temperature measurements are often compromised by heating the drilling mud to prevent freezing of the wellbore. However, observing the trend of temperature measurements and monitoring drilling over the long term allowed scientists to identify permafrost.
They also looked for ice formation inside the well, changes in drill cuttings produced when drilling the well, and changes in bottom gas measurements.
Monitors identified gas intrusions into the well, indicating accumulations beneath the permafrost, and abnormal pressure measurements showing the frozen permafrost acting as a seal. In other cases, even when the permafrost and underlying geology were suitable for trapping gas, and the rocks were known sources of hydrocarbons, there was no gas, which suggested that the gas produced had already migrated.
The scientists stressed that gas accumulations were much more frequent than expected. Of the 18 hydrocarbon exploration wells drilled in Svalbard, eight showed signs of permafrost and half of them found gas accumulations.
“All the wells that hit gas accumulations did so by chance; however, hydrocarbon exploration wells specifically targeting accumulations in more typical environments had a success rate well below 50%,” explains Birchall.
“These things seem to be common,” he continues. to detect explosive levels of methane, that went off immediately when we held them over the well.”
Experts have shown that the active layer of permafrost – the top one or two meters that thaws and refreezes seasonally – is expanding with a warming climate. However, less is known about how deeper permafrost changes, if at all.
To understand it, you have to understand the flow of fluids under permafrost. If frozen permafrost steadily becomes thinner and uneven, methane could migrate and escape more easily, which could accelerate global warming and worsen the climate crisis.
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