Methane wave: in search of leaky boreholes

How important are natural gas leaks?

BGR and MARUM looked at nine more boreholes in the German sector of the North Sea in 2021, but used hydroacoustics to route networks very precisely over the relevant boreholes to study the water column and geochemically identify methane. The researchers focused on one aspect that, from their point of view, was not sufficiently taken into account in all of their work – natural gas leaks also near the boreholes: Krupiński is being rebuilt by MARUM, and they can also collect samples in the North Sea, ”enthuses Blumenberg. “For the first time in the North Sea, we were able to use such a small robot to collect gas bubbles that we geochemically analyzed in the laboratory to determine if they were thermogenic or biogenic in origin.”

Scientists supplemented the hydroacoustic measurements with a human-sized water sampler: “We placed it in each well and at the natural gas outlets to take upstream and downstream samples. In this way, we could exclude that the methane measured at one point was not coming from another source, ”explains Blumenberg. And so they came across the phenomenon of »BERT«, an underwater salt dome. BERTA is an area with a very noticeably increased concentration of natural gas, methane, which, however, comes from the gas risers in the weak zones above the salt dome and has nothing to do with the old wells.

People like to drill near salt domes as oil or gas often accumulated on their sides. However, it seems that BERTA does not deal with such gases, there may be another source. Blumenberg explains: “This part of the North Sea was land 10,000 years ago, there were rivers with deposits of plants and other carbon-rich materials that led to large peat deposits. To this day, microorganisms use it to produce methane, which is found in the deeper sediments of the North Sea. ”

This scientifically fascinating background, which scientists published in Frontiers in Earth Science, now serves as a model for the formation of biogenic gas with particular anomalies. He explains that there are many marine methane vents that are not man-made but natural. If you want to measure the human effect on methane from old sea wells, you need to rule out these natural sources.

Conflicting data, missing data

Researchers at the institutes involved did not find any methane leaks from the old wells they examined, some of which were also drilled through the shallow gas pockets. This does not mean that none of the nearly 200 other old boreholes in the German sector of the North Sea are leaky. It also does not interfere with the 20 wells in the UK sector of the North Sea visited by the Haeckel team. However, he explains that further measurements are needed if we want to more accurately determine the leakage balance here, on land and in the rest of the North Sea.

There is also hardly any research on 20,000 old onshore boreholes in Germany alone. Better is the data on millions of old wells in the US. However, comparisons between countries are difficult, for example because of different mining laws. For example, in the USA, every landowner also owns the underground, while in Germany, all the raw materials found in the deep belong to the federal state. This could allow drilling companies to drill or seal wells with varying capacities and responsibilities – regardless of the current world market price.

A working group led by Mary Kang published an exciting correlation between the price of oil and the number of wells in the PNAS. It turned out that with rising oil prices in the US, more and more wells are being drilled. On the other hand, if the price of oil falls, wells may be exited too quickly again. Because Kang’s team examined 750,000 abandoned boreholes in Pennsylvania alone and found that methane was still leaking from them years later.

© Federal Institute of Geosciences and Natural Resources (BGR) (details)

Sunset on the North Sea | View from the deck of the research vessel Maria S. Merian during the North Sea expedition in January 2021.

In Germany, there is no such link between the price of oil and drilling. Blumenberg believes that the processes and approvals all the way to production and sealing are stricter here as well. To better understand the situation in Germany and Europe, Mary Kang wants to start a project with European research groups and BGR – with Martin Blumenberg.

On land, BGR is currently exploring the old shafts in Lower Saxony, which are home to many historic oil and gas wells. While rough seas and limited ship times no longer play a role, Blumenberg faces new difficulties when, for example, there is a cornfield above an investigated well. His team uses, among other things, a special syringe to draw soil air from deeper soil layers to analyze it in the laboratory.

Even with leaks, natural gas is still more environmentally friendly than coal

Journalists from the U.S. media center Boomberg LP were also on the way with infrared cameras and methane detectors, and revealed in several media reports in October 2021 that there are many old leaking gas wells in the Appalachian Mountains that cannot be expected to be properly sealed. see you. Much of the boreholes are likely not sealed as it costs over $ 10,000 to concret the well.

In the summer of 2021, the German environmental organization DUH also used infrared cameras to detect ‘significant’ methane emissions at 15 on-ground natural gas installations and spoke of serious neglect. When EDF in Hamburg searched for leaks in the city’s natural gas infrastructure, the working group did not find any significant gas emissions, possibly because – unlike other countries – the infrastructure here in Germany had already been renovated: Until a few decades ago, the natural gas used in Germany was still transported on cast iron pipes with leaky welds, but pipes have long since been replaced by tighter plastic pipes.

Therefore, at other points or on the way to Germany, you should carefully check that there are no leaks in the natural gas supply chain. Some argue that so much methane is escaping that coal is even better than natural gas, but Blumenberg disagrees: “Natural gas may not be the best, it’s just a bridge technology.” colleagues calculated that the natural gas supply chain would still be a better solution than coal for Germany, even if all the spills went as expected – in the worst case scenario.

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But even if leaks in old German wells play a minor role, after more than 20 years of methane research, Blumenberg is confident: »Understanding possible methane emissions from wells remains very important in a world that increasingly relies on natural gas as a bridging technology. «

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