- 13 Sep 2020 13:28
#15119429
Methane is more harmful for the climate then CO2 with increasing temperature arround the globe it will brake out therefore is the better solution to burn it for energy.
https://e360.yale.edu/features/the-worl ... e-hydrates
Methane hydrate on fire.
Methane hydrate on fire. J. PINKSTON AND L. STERN/USGS
The World Eyes Yet Another Unconventional Source of Fossil Fuels
Vast quantities of methane hydrates — frozen deposits of natural gas on the sea floor — exist worldwide. But as experimental drilling moves forward, many experts question the wisdom of exploiting a costly, environmentally risky trove of fossil fuels that will accelerate global warming.
BY NICOLA JONES
AUGUST 21, 2017
In May of this year, China claimed a breakthrough in tapping an obscure fossil fuel resource: Researchers there managed to suck a steady flow of methane gas out of frozen mud on the seafloor. That same month, Japan did the same. And in the United States, researchers pulled a core of muddy, methane-soaked ice from the bottom of the Gulf of Mexico.
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The idea of exploiting this quirky fuel source would have been considered madness a couple of decades ago — both wildly expensive and dangerous. Until recently, methane-soaked ice was considered explosively unstable. In the Gulf of Mexico, traditional oil rigs have been tiptoeing around these icy deposits for years, trying to avoid them.
“These deposits have been a pain in the neck for oil exploration,” says Scott Dallimore with the Geological Survey of Canada. Accidentally melting deposits overlying traditional oil and gas fields could cause drilling infrastructure to collapse, or pipes to clog up with ice. After the Deepwater Horizon oil rig exploded in the Gulf of Mexico in 2010, for example, water and methane formed an icy plug that scuppered one attempt to halt the oil spill.
A piece of methane hydrate found by U.S. scientists off the coast of Oregon.
A piece of methane hydrate found by U.S. scientists off the coast of Oregon. USGS
Now the tide has started to turn, as studies of the frozen gas have quelled some of the bigger fears. “We always used to think of these as explosive and dangerous — they’re not,” says Dallimore, who is involved with Canada’s explorations of these deposits. These reassuring findings, combined with rising energy demands, have spurred some countries — especially fossil fuel-poor nations like India and Japan — to think seriously about commercial extraction.
But there are still concerns about the wisdom of mining this unexplored corner of the fossil fuel landscape, including the possibility of triggering underwater landslides, unleashing tsunamis, disturbing ocean ecosystems, and — most important of all — more than doubling the planet’s natural gas supplies and the planet-warming emissions that go along with them. So is drilling for methane hydrates really a good idea?
For decades now, mankind has been chasing fossil fuels in smaller, weirder, and harder-to-get crevasses of the Earth. In the 1990s, the asphalt-like sludge of Alberta’s oil sands started to look like a viable resource; by 2003, thanks to changing technologies and economics, Canada’s standing in the international oil reserve tables rocketed to second place, behind Saudi Arabia. Then, around 2008, hydraulic fracturing, or fracking, became all the rage: Fossil fuel companies started injecting water, sand, and chemicals into shale rocks to split them apart and suck the natural gas out of the cracks. Both technologies, with their attendant environmental problems, have been grabbing headlines ever since.
Methane-soaked ice is the newest, strangest resource competing to be in the list of exploitable gas.
For decades now, mankind has been chasing fossil fuels in smaller, weirder, and harder-to-get places.
Technically called methane hydrate, or methane clathrate, these deposits are simple ice with methane molecules trapped within the crystal cages of the water molecules. Methane hydrates form in places that are gassy, wet, cold, and under pressure, like in permafrosts or at the bottom of the sea. A chunk of methane hydrate looks benign, like a dirty snowball. But hold a lighter to it and the snowball goes up in flames. Some people call it “fire ice.”
No one even knew that hydrates existed in nature until the 1960s; the first sample wasn’t pulled from the seafloor until 1979. But researchers soon came to realize there is a ridiculous amount of the stuff. There are now thought to be 1,500 to 15,000 billion tons of carbon locked up in hydrates around the world — comparable to the 5,000 billion tons of carbon in all the planet’s oil, gas, and coal. Even though only a fraction of this is mineable, in the United States it has been estimated that exploiting hydrates could bump up that country’s natural gas deposits seven-fold.
The first tests of whether hydrates could be successfully tapped took place not underwater, but in the permafrosts of the Canadian North. In 2002, and then again 5 years later, researchers including Dallimore tackled the hydrates in Mallik, a site on an island of the Mackenzie River Delta near the Beaufort Sea. The idea, then and now, was not to physically dig up the hydrates, but instead to melt (or “dissociate”) them in place, so the gas could be pumped out. Heating the hydrates didn’t work so well, they found, but depressurizing them did the trick. When water is pumped out of the ground and the pressure down below drops, the hydrates become unstable. They then collapse into their component parts of water and gas, so the methane can be sucked up.
Permafrost sites might be easier to access, but the hydrate mother lode (99 percent of the global supply) is underwater. The first deepwater hydrate production test was done by Japan in 2013. Japanese engineers drilled down through a kilometer of water and a couple hundred meters of mud to reach a 60-meter-thick layer of hydrate-rich sand in the Nankai trough. Pumping up water lowered the pressure, and gas started flowing — at 20,000 cubic meters a day, about 10 times higher than at Mallik. Their test stopped when their well got clogged with sand.
Map of the locations at which gas hydrates have been recovered and or confirmed. Click image to enlarge.
Map of the locations at which gas hydrates have been recovered and or confirmed. Click image to enlarge. UNEP
These were both just short-term tests, lasting weeks, not years. But the results were encouraging enough to spur more work. In 2015, the Indian government found a mineable deposit in the Bay of Bengal, and has said it aims to have commercial production in place by 2020. The details of Japan’s 2017 tests have been kept quiet so far, says Tim Collett, a Colorado-based U.S. Geological Survey (USGS) expert on hydrates. But China reported a top flow of 35,000 cubic meters of gas in a single day from their 2017 experiment. Though U.S. efforts have so far been more scientific than commercial, the drilling in the Gulf of Mexico has shown that spot to be a possible candidate for future methane hydrate exploitation.
The early concern with mucking about with seafloor hydrates was that poking and prodding could theoretically cause big chunks of hydrate to accidentally destabilize. This was a worry for at least two reasons: Release enough gas bubbles into the water and maybe they would lower the density of the water enough to sink ships above. Plus, methane is at least 20 times more potent than carbon dioxide as a greenhouse gas, so if vast amounts were released into the atmosphere it would accelerate climate change. Fortunately, both of these concerns have ebbed.
Big hydrate blowouts have probably happened before — triggered by nature, not by mankind. Kilometer-wide craters on the Arctic seafloor are thought to have been made by domes of methane gas that collapsed some 12,000 years ago. About 55 million years ago, the release of 1,200-2,100 billion tons of methane carbon from hydrates has been blamed for helping global temperatures skyrocket by about 5 degrees C (9°F).
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But such blowouts and massive releases are a lot less common than previously thought, says Carolyn Ruppel, who leads the USGS Gas Hydrates Project out of Woods Hole, Massachusetts. Other big bursts of methane in the planet’s history are now thought to have come from wetlands rather than hydrates, she says. “We don’t see a lot of evidence for catastrophic bursts,” says Ruppel.
The production tests done so far have shown that the hard part is getting the gas out, not stopping it from escaping. Drillers have to use energy to pump up water, lower the pressure, and get gas out; stop pumping and the dissociation stops, making runaway destabilization impossible. “We see this time and time again in samples and field tests at Mallik, Alaska, and in Japan,” says Dallimore.
Even if methane escapes from seafloor deposits, Ruppel adds, it’s unlikely to reach the surface. Studies have shown that most of it gets trapped in sediments, is gobbled up by microbes or dissolves into the water. “Hardly any of it makes it to the atmosphere,” agrees Dallimore.
Unlike with fracking, no chemicals are involved with hydrate extraction: just methane and water.
Nevertheless, real concerns remain. Microbes in the water that consume methane use up oxygen and release carbon dioxide, making the water more acidic. Those conditions can make life stressful for marine organisms. That was accidentally tested by the Deepwater Horizon explosion, which released not just oil but also methane gas (from the reservoir, not from hydrates). There was a subsequent change to oxygen levels in the waters, although researchers couldn’t pin any negative ecosystem impacts on the methane release alone. Ruppel and others are planning to investigate some natural methane seeps in the Atlantic in the coming months to see how they might be affecting water chemistry.
An aerial view of the Mallik drilling site near the Beaufort Sea in Canada.
An aerial view of the Mallik drilling site near the Beaufort Sea in Canada. SUZANNE WEEDMAN/USGS
Drilling and gas extraction could also destabilize the ground enough to cause an underwater landslide. “The major risk is slope failure,” says Klaus Wallmann, who is leading a German research initiative to explore hydrates as a natural gas resource. Hydrates can act like a kind of cement to hold seafloor sediments together; if they are disturbed, that could cause ground collapse, wiping out local ecosystems or even, theoretically, triggering tsunamis. But, reassures Wallmann, “a major tsunami is very unlikely.”
Ways exist to mitigate these risks, like not tapping areas with steep slopes or where the hydrates are close to the seafloor surface. Miners could also swap the methane in hydrates with carbon dioxide captured from coal-burning power plants or other sources, cunningly tucking away some greenhouse gases while also keeping the icy hydrates stable. The U.S. tested that idea in some Alaskan permafrosts in 2012; it worked, though they weren’t able to suck out methane at a high rate.
A 2014 United Nations Environment Program (UNEP) report concluded that the environmental risks of hydrate exploitation “would likely be similar to those of conventional [natural gas] projects.” But that still leaves a major issue — the exploitation of yet another massive source of greenhouse gases. That’s the real hazard, says Yannick Beaudoin, editor of the UNEP report. “With costs of renewable sources now flirting with coal in some places, we might avoid this `hazard’ simply because of the rapidly changing economics,” adds Beaudoin, chief scientist for GRID-Arendal, a Norwegian-based foundation that supports sustainable development. Countries like China, Beaudoin adds, might choose to up their investment in renewables rather than plowing funds into novel fossil fuels.
The real thing holding back hydrate mining isn’t technological, political, or environmental, but economic.
The unknowns still leave some observers worried, and wondering whether and how the industry could be regulated before it ramps up. “We need a better grasp of the risks of such operations and how to manage them,” write Haoran Dong & Guangming Zeng of China’s Hunan University in a recent issue of Nature. Wallmann says that Vladimir Golitsyn, the president of the International Tribunal for the Law of the Sea, has asked him about whether regulation might be needed, and what form it might take.
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In the meantime, the real thing holding back hydrate production isn’t technological, political, or environmental, but economic. “In North America, we’re awash with natural gas and no one cares [about hydrates],” says Dallimore.
A typical deepwater natural gas well pulls more than a million cubic meters of methane per day, notes Collett — about 50 times higher than the rates managed with hydrates so far. But that might not be as big a problem as it seems, he adds. India imports more than a third of its energy resources; Japan more than 90 percent. “Their natural gas costs are 4 times what we pay,” Collett notes. For them, hydrates are looking ever-more attractive.
Nicola Jones
Nicola Jones is a freelance journalist based in Pemberton, British Columbia, just outside of Vancouver. With a background in chemistry and oceanography, she writes about the physical sciences, most often for the journal Nature. She has also contributed to Scientific American, Globe and Mail, and New Scientist and serves as the science journalist in residence at the University of British Columbia. MOREABOUT NICOLA JONES →
TOPICS
Energy
GLOBAL WARMING
GREENHOUSE GASES
NATURAL GAS
TECHNOLOGY
REGIONS
North America
Asia
Antarctica and the Arctic
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