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可燃冰:有可能成为未来的能源

更新时间:2018/12/10 20:21:08 来源:纽约时报中文网 作者:佚名

Why 'flammable ice' could be the future of energy
可燃冰:有可能成为未来的能源

Buried below the seabed around Japan, there are beds of methane, trapped in molecular cages of ice. In some places, the sediment covering these deposits of frozen water and methane has been eroded away, leaving whitish mounts of what looks like dirty ice rearing up out of the seafloor.

在日本周边的海底之下,埋藏着甲烷储层。在那里,甲烷被困在冰晶体结构的水分子中。在有些地方,覆盖在这些冻结的甲烷水合物矿藏表面的其他沉积物已被腐蚀殆尽,留下发白的,看上去像脏污冰块一样的可燃冰突起在海床上。

Take a chunk of this stuff up to the surface and it looks and feels much like ice, except for a give-away fizzing sensation in the palm of your hand, but put a match to it and it doesn’t just melt, it ignites. Large international research programmes and companies in Japan, among other countries, are racing to retrieve this strange, counter-intuitive substance – known as fiery ice – from beneath the seafloor to use its methane for fuel. If all goes to plan, they may even start extraction by the end of the next decade. But the journey so far has been far from smooth.

拿起一块带到海面,你会发现它的外表和给人的感觉都很像冰,只不过你会发现它在你手中会发出咝咝的声音,用点燃的火柴去靠近它,不仅会融化,还会燃烧起来。大型国际研究项目和日本等国家的公司,正在争相研究从海底开采这种与人的直觉不符的奇怪物质(人们称之为可燃冰),以获取其中的甲烷燃料。如果一切按计划进行,十年后日本等国家们可能就要开始商业性开采。但截至目前,进展远远称不上顺利。

There’s no doubt that methane hydrates could offer a major source of fuel, with recent estimates suggesting they constitute about a third of the total carbon held in other fossil fuels such as oil, gas and coal. Several nations, notably Japan, want to extract it. It is not hard to find, often leaving a characteristic seismic signature that can be detected by research vessels. The problem is retrieving that gas and bringing it to the surface.

毫无疑问,甲烷水合物可能会成为一种主要的燃料来源。最近有人估计,它们大约相当于石油、天然气和煤炭等其他化石燃料储藏的总碳量的三分之一。多个国家,尤其是日本,希望对其进行开采。找到甲烷水合物并不难,它们通常会留下一种勘察船能够以震测方式发现的特征。真正的挑战在于分离甲烷并将其输送到海面。

“One thing that’s clear is that we’re never going to go down and mine these ice-like deposits,” says Carolyn Ruppel, who leads the US Geological Survey’s Gas Hydrates Project.

美国地质调查局(US Geological Survey)的天然气水合物项目负责人拉佩尔(Carolyn Ruppel)说,“有一点很清楚,我们永远不会下到海底去开采这些像冰一样的沉积物”。

It all comes down to physics. Methane hydrates are simply too sensitive to pressure and temperature to simply dig up and haul to land. They form at typically several hundred metres beneath the seafloor at water depths of about 500 metres, where pressures are much higher than at the surface, and temperatures are close to 0C. Take them out of these conditions, and they begin to break down before the methane can be harnessed. But there are other ways to do it.

一切问题都归结于甲烷水合物的物理特性。它们对压力和温度非常敏感,人类根本无法简单地将其开采出来并输送到陆地上。可燃冰往往埋藏在水深约为500米的海底以下几百米处。那里的压力远高于海平面,温度接近0摄氏度。离开高压和低温环境后,甲烷水合物会在甲烷被提取出来之前已经分解。不过还是有办法开采。

“Instead, you have to force those deposits to release the methane from the formation in the seafloor. Then you can extract the gas that comes off,” says Ruppel.

拉佩尔说,“必须强迫这些沉积物在海底把甲烷释放出来,然后再提取释放出来的甲烷”。

A Japanese government funded research programme is trying to do just that. Its initial mission, after several years of preliminary research scoping out likely spots for methane hydrates, was in 2013. “It was a world-first,” says Koji Yamamoto, director general of the methane hydrate research and development group at the Japan Oil, Gas and Metals National Corporation, and one of the leading researchers in Japan’s national gas hydrates research programme.

日本政府资助的一个研究项目正在朝这个方向努力。日本经过几年的初步研究,对可能存在甲烷水合物的海域进行了评估后,于2013年启动了全球首个海底开采可燃冰测试计划。日本石油天然气和金属国家公司(Japan Oil, Gas and Metals National Corporation)甲烷水合物研究与发展小组的负责人山本幸治(Koji Yamamoto,音)说,“这在全世界是首开先河”。山本幸治也是日本国家甲烷水合物研究项目的主要研究人员之一。

The team managed to produce gas from the methane hydrate reserves by drilling a borehole down into the seabed of the Nankai Trough, off the eastern coast of Japan’s main island. By lowering the pressure on the reserves, they were able to release and collect the gas. The test ran for six days, before sand entered the well and blocked the supply.

通过在日本本州东海湾附近的南海海沟的海底钻孔,该团队得以从甲烷水合物储层中提取出了甲烷气体。他们通过降低储层受到的压力,得以释放并收集甲烷气体。这场试验持续了六天,直到沙子进入气井,堵塞了管道。

A second test in 2017 ran in the Nankai Trough. This time the researchers used two test wells. The first encountered the same problem as before and became blocked with sand after several days. But the second of the well ran for 24 days without technical problems, Yamamoto says.

2017年,日本又在南海海沟进行了第二次试验。这一次,研究人员使用了两口测试气井。第一口井遇到了和之前一样的问题,几天后就被沙子堵住。但山本幸治说,第二口井连续24天没有出现技术问题。

Even though the tests ran for a short time, they showed that there was a glimmer of potential that Japan might have usable carbon-based natural resources. The public reaction, however, was mixed, says Ai Oyama, a technical translator and former research analyst working on methane hydrates at the Hawai’i Natural Energy Institute. Some welcomed the idea that Japan may have energy independence. Others were very wary about any technique that disturbed the seafloor near tectonic plate boundaries.

尽管试验持续的时间短,但显示出日本将会拥有日本国产碳基能源的一线可能性。但技术翻译、夏威夷自然能源研究所(Natural Energy Institute)的前甲烷水合物研究分析师小山爱(Ai Oyama)称,日本公众反应不一。有些人对日本有希望拥有自己的能源不再完全依赖进口这一点表示欢迎。有一些人则对任何破坏地壳板块边缘附近海床的技术都非常担心。

“In general, people just feel really scared to do anything to the ocean floor. The place is known to be unstable and earthquakes happen,” Oyama says.

小山爱说,“总的来说,人们真的害怕破坏到日本海的海床。众所周知,那里不稳定,时有地震发生”。

The fear is that depressurising one part of the methane hydrate deposit might make the whole reserve become unstable.

人们担心,给甲烷水合物储层的某个部分减压可能会导致整个储层变得不稳定。

“People worry that we’ll start extracting methane from the gas hydrates and get into a runaway breakdown where we can’t stop it,” says Ruppel.

“人们担心我们会开始从这种天然气水合物中提取甲烷,进而陷入一种我们无法阻止的失控崩溃中”,拉佩尔说。

The problem with this would be two-fold. First, a lot of methane gas would suddenly be released into the ocean – which could potentially add vast amounts of the greenhouse gas to the atmosphere.

这里涉及的问题是两方面的。首先,大量甲烷气体会突然释放出来,进入海洋,这可能会导致大气中的温室气体大量增加。

Second, methane hydrate releases a lot of water as well as a lot of methane when it destabilises, which would introduce a lot more liquid into the sediment below the ocean floor. In a steeply sloping environment, a lot of excess water could lead to landslips. Some environmentalists even fear that it could lead to a tsunami.

其次,甲烷水合物分解时会释放大量的水和甲烷,导致海床以下的沉积物中的水分大大增加。在陡峭的斜坡环境中,水分过多可能会引发滑坡。一些环保人士甚至担心这会引发海啸。

However, the physical properties of methane hydrate put a natural brake on this chain of events, says Ruppel. To release methane from a deposit, you have to put energy into the system. Without working hard to release the gas – through lowering the pressure or raising the temperature of the deposit – it simply stays put in its stable form of methane hydrate.

然而,拉佩尔说,甲烷水合物的物理特性阻碍了这一系列事件的发生。要让甲烷从沉积层中释放出来,就必须向该系统注入能量。不努力让甲烷释放出来(释放甲烷是通过降低压力或提高沉积层的温度),它就会保持甲烷水合物的稳定形态不变。

“So the problem is actually the opposite. You may start the process of getting the gas to come off, but to keep that process going, you have to introduce more energy to make it happen,” says Ruppel.

拉佩尔说,“所以说这个问题其实是对立的。你可以开启让甲烷气体释放出来的过程,但要让这个过程持续下去,就要引入更多能量才能实现”。

While a runaway reaction isn’t likely, the Japanese programme is still carrying out extensive environmental studies to test the safety of the methane hydrate production. The data gathered at the first test in 2013, and at a second longer test in 2017, so far hasn’t suggested that the technique will destabilise the ocean floor, Yamamoto says. But given Japan’s history of natural disasters – around 24,000 people are still under evacuation order since the 2011 Tōhoku earthquake and tsunami – the public is highly risk-averse.

尽管不太可能出现失控的反应,但日本这个项目仍在进行大范围的环境研究,以测试甲烷水合物生产的安全性。山本幸治说,迄今为止,2013年第一次试验和2017年持续时间较长的第二次试验收集到的数据未表明这种技术会破坏海床的稳定。但考虑到日本自然灾害频发的历史,自2011年东北地方太平洋近海地震海啸以来,仍有大约24000人处于被疏散状态,民众非常害怕再担风险。

“We feel that gas hydrate production is environmentally safe,” says Yamamoto. “But still, [the public] have a concern about negative effects of gas hydrate production.”

山本幸治说,“我们认为这种天然气水合物生产在环境方面是安全的,但(民众)还是担心天然气水合物生产的负面影响”。

As well as the reserves buried beneath the sea floor, there is another type of methane hydrate deposit that has been gaining attention from Japanese researchers. Efforts to research shallower deposits, very close to the seafloor surface, is also being explored off in the Sea of Japan to the west of the country. Accessing these shallow reserves poses a very different potential risk.

同时,除了深藏在海床之下的甲烷水合物储备外,另一种甲烷水合物也引起了日本研究人员的注意。日本正在该国以西的日本海,对非常接近海底表层的浅层甲烷天然气储藏进行研究和勘探。开采这些浅层甲烷水合物构成的潜在风险截然不同。

“These are very active biological environments,” says Tim Collett, a senior scientist at the US Geological Survey’s Gas Hydrate Project. “There are whole communities that live off the methane.”

“这些海域生态环境非常活跃”,美国地质调查局天然气水合物项目的高级科学家科莱特(Tim Collett)说,“有些生物群落全都以甲烷为生”。

These environments are rich in unique organisms, from bacteria to very large tubeworms and crabs, all specialised to live off the methane as their source of energy. In other parts of the world where these methane-based communities live, they are often protected as rare natural environments.

在这些环境中,有种类丰富的独特生物,从细菌到巨型管虫和螃蟹,全部以甲烷为生,把甲烷作为它们的能量来源。在世界其他地方,以甲烷为生的生物群落栖息的海洋,通常被当作稀有自然环境而受到保护。

Beneath the permafrost

永冻层之下

Japan’s main efforts in extracting methane hydrate, however are not in the seafloor at all, but in the only other place that flammable ice can found – deep in the permafrost, the permanently-frozen layer of rock or soil that covers the ground at polar regions and high-rise mountains. Researchers from Japan, which doesn’t have its own permafrost, are assisting in the most ambitious on-land production test for methane hydrate so far, in Alaska’s North Slope.

但日本开采甲烷水合物的主要活动并不在海底,而是在永冻层深处。永冻层是极地和高山地表的一层永远处于冰冻状态的岩石或土壤,也是除海底之外唯一能够找到可燃冰的地方。日本并没有自己的永冻层。该国的研究人员正在阿拉斯加北坡协助进行迄今为止最雄心勃勃的陆上甲烷水合物开采试验。

In December, researchers from Japan’s national research programme are set to start work with the US Geological Survey and the US’s Department of Energy, to begin what they hope will be a long-term production test site. While this source of methane hydrate is very different, the methods used to get to it are actually very close.

日本国家研究项目的研究人员将从2018年12月开始与美国地质调查局和美国能源部(Department of Energy)合作,开始建设试验场地。他们希望打造一个长期的生产试验场地。尽管这种甲烷水合物的来源截然不同,但开采方式其实非常接近。

“The conditions at those reservoirs under the permafrost are pretty similar pressure and temperature conditions as they are in the Nankai Trough,” says Collett. “It turns out, to the best of our knowledge, even though the Arctic and the marine environment are very different, the physical properties of the deposits and how they occur in the sediments appears to be very similar.”

科莱特说,“永冻层下面的这些甲烷水合物所处的环境,和南海海沟的压强和温度相近。事实证明,至少据我们所知,尽管北极和海洋的环境大相径庭,但甲烷水合物储藏的物理性质和它们在沉积层中的反应似乎非常相似”。

The production techniques used in Alaska could end up being transferrable to the marine environment. But there are still big challenges. A long-term production of methane hydrates hasn’t been carried out anywhere yet, on land or under the sea.

在阿拉斯加使用的开采技术最终可能会适用于海洋环境。但目前仍存在巨大的挑战。迄今为止,无论是在陆地冰冻层还是在海底,人类还没有进行过长期的甲烷水合物开采。

“We’re still very much in research mode,” says Collett.

科莱特说,“我们在很大程度上还处在研究阶段”。

Given the difficulty of retrieving gas from methane hydrate reserves, and the concerns around extraction, the stakes have to be high for a nation to invest heavily in this technology. Having very few other options in terms of domestic energy makes this hard-to-access source of methane an appealing prospect. Japan is not a country that has other carbon-based sources of energy to fall back on.

考虑到从甲烷水合物中提取天然气的难度,以及对开采的担忧,对大力投资这项技术的日本来说,投资风险必然很高。在国内能源方面,日本几乎别无选择。这使得开采难度颇大的甲烷资源成了一个诱人的希望。日本是没有其他碳基能源资源可以依靠的国家。

“Japan imports a lot of natural gas, but it is very costly. If we have our own domestic resource, [it could] contribute to the energy security of Japan,” says Yamamoto.

山本幸治说,“日本进口大量的天然气,但代价非常高。如果我们拥有自己的国内资源,(可能)有利于日本的能源安全”。

As an economic resource, it’s easy to see the appeal of methane hydrate. But, fundamentally, it is just another source of natural gas and burning it would contribute to climate change.

作为一种经济资源,甲烷水合物的吸引力容易看到。但从根本上说,它只是另一种天然气能源,其燃烧会加剧气候变化。

“The most important thing is the recognition and appreciation that gas hydrates are just another fossil fuel,” says Collett. “All the social and environmental issues associated with fossil fuels apply to gas hydrates.”

科莱特说,“最重要的是认识到并承认天然气水合物只是另一种化石燃料。与化石燃料有关的所有社会和环境问题,天然气水合物都有”。

In this context, methane hydrates – if they are to play a role in Japan’s energy future – are likely to be used as a bridging fuel, in the transition towards renewables. Natural gas is the least carbon-intensive form of fossil fuel, releasing less carbon dioxide per unit of energy released than coal or oil. But, as a carbon-based fuel, burning it still contributes to climate change.

在这种背景下,甲烷水合物——如果它们即将参与日本的能源未来——应该只当成一种过渡燃料,以帮助过渡到转用可再生能源。天然气是碳排放最低的化石燃料,每单位能源释放的二氧化碳少于煤炭和石油。但作为一种碳基燃料,它的燃烧仍会加剧气候变化。

“We need to shift to renewable energy,” says Koji Yamamoto. “But complete switch to renewable energy [takes] a very long time.”

山本幸治说,“我们必须转向可再生能源,但完全转向可再生能源(需要)很长的时间”。

Even as a transition fuel, gas hydrates could be hugely important, Ruppel says. “Were a country able to efficiently produce methane from these deposits, it could open a new realm in bridge fuels to another energy future,” she says.

拉佩尔说,即使作为过渡燃料,天然气水合物也可能非常重要, “如果一个国家能够高效地从这些储藏中开采甲烷,就可能开启过渡燃料的新领域,引领我们走向另一种能源未来”。

How useful a role it can play in the future depends on how quickly methane hydrate can be accessed and produced on a commercial scale. The Japanese government hopes to begin commercial projects exploring methane hydrate between 2023 and 2027, according to its latest Strategic Energy Plan.

甲烷水合物在未来的作用取决于其何时可以开采,以及何时可以达到商业生产的规模。日本最新的战略能源计划(Strategic Energy Plan)显示,日本政府希望在2023年到2027年之间启动甲烷水合物的商业勘探项目。

This target could be a bit ambitious. Jun Matsushima, a researcher at the Frontier Research Center for Energy and Resources at the University of Tokyo, puts the estimate at around 2030 to 2050. “There is a long way to commercialise methane hydrate,” says Matsushima.

这个目标可能有些太过雄心勃勃。东京大学先端能源与资源研究中心(Frontier Research Center for Energy and Resources at the University of Tokyo)的研究员松岛润(Jun Matsushima)估计,计划实现时间估计应推迟到2030年前后到2050年之间。松岛润说:“要商业开采甲烷水合物有很长的路要走。”

The make-or-break moment will be when a long-term production test can be sustained without technical problems or budget constraints shutting it down, says Ruppel.

拉佩尔表示,决定成败的关键是长期的生产试验能够持续下去,此期间不会因技术问题或预算紧张导致开采试验半途而废。

“I would guess there will be a long-term production test – from months to more than a year – by 2025. But I don’t have a crystal ball,” Ruppel says.

拉佩尔说:“我猜会在2025年之前进行一次长期生产试验,从几个月到超过一年。但我没有(能够显示未来的)水晶球。”

But at the same time, Japan is committing to moving towards renewable energies and decarbonisation. As technologies for harnessing renewable energy become better and cheaper, the role for fossil fuels – especially experimental and expensive ones like methane hydrate – decreases. The longer it takes to get methane from gas hydrate reserves on a commercial scale, the shorter the useful window for using it may be. The other possibility is that adding in a new accessible source of fossil fuel could delay the transition to renewables, says Collett.

然而,与此同时,日本也承诺将向可再生能源和脱碳的方向发展。随着利用可再生能源的技术变得更完善、更便宜,化石燃料的作用会减弱,尤其是像甲烷水合物这种仍在实验性开采的昂贵燃料。从实验开采到商业化规模开采的时期越长,利用甲烷水合物这种能源的有效窗口期可能就越短。科莱特说,另一种可能性是,出现一种可开采的化石燃料能源将会推迟向可再生能源的过渡。

This source of carbon, the most abundant in the world, may be one of the last new forms of fossil fuel to be extracted on a commercial scale. It is also the only one to be developed with the end of fossil fuels in sight. The race for methane hydrates is a unique one, where researchers are working towards a goal that might be made irrelevant by renewables by the time they reach it.

作为世界上最丰富的碳来源,甲烷水合物可能是最后一批即将面临商业化开采的新型化石燃料,也是唯一一种在化石燃料时代即将终结时才进场的化石燃料。各国争抢开采甲烷水合物可说是最特别的能源争夺战,因为可能还没有等到现在的开采研究出到成果,可燃冰就因为可再生能源成为主流而变得无关紧要。

For this reason, methane hydrates may well have a shelf life, but it remains to be seen whether Japan, and other countries pursuing them, will be able to get to them on a sufficiently large scale before they’ve already become expendable.

因此,甲烷水合物很可能只是一种以备不时之需的能源。但日本和其他谋求开发甲烷水合物的国家是否能够赶在这种能源变得无关紧要之前实现大规模开采,还有待观察。

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