If this takes off HZR is in the box seat

Fire ice’ deposits could provide new source of energy

04 Sep 2013by David Foxwell

Methane hydrates from a gas field approximately 50km off the Japanese coast in the Nankai Trough were used in Japanese tests to successfully extract natural gas. Other countries, i...

Methane hydrates from a gas field approximately 50km off the Japanese coast in the Nankai Trough were used in Japanese tests to successfully extract natural gas. Other countries, including Canada, the US and China have also been looking into ways to exploit methane hydrate deposits, although concerns have also been raised about the potential environmental effects of using offshore deposits as a source of methane.

Methane hydrate, sometimes known as ‘fire ice’, is an ice-like material in which methane molecules and water combine under high pressure and low temperatures. Deposits of gas hydrates are widespread in marine sediments beneath the ocean floor and in sediments within and beneath permafrost areas, where pressure and temperature conditions keep the gas trapped in the hydrate structure. Methane is the gas most often trapped in these deposits, making gas hydrates a potentially significant source for natural gas around the world.

Japanese state-owned Japan Oil, Gas and Metals National Corporation (JOGMEC) has been conducting a survey of the field. Japanese government officials have said that they hope to develop technology that would enable the country to extract methane hydrates on a production scale within five years.

A Japanese study estimated that at least 1.1 trillion cubic metres of methane hydrate exist in offshore deposits, equivalent to more than a decade of Japan’s gas consumption. The deposits are all the more important to Japan since the Fukushima nuclear disaster two years ago.

JOGMEC, which has been conducting preparatory work for some time on deposits off the Atsumi and Shima peninsulas, started a flow test using a technique known as depressurisation earlier this year. In February and March last year, JOGMEC drilled a production well and two monitoring wells and subsequently acquired a number of core samples.

JOGMEC said that, although the first offshore production test was not commercial-scale production, it represents major progress in research and development of methane hydrate as a resource. The work has provided invaluable information about the dissociation behaviour of methane hydrates under the seabed and the impact on the surrounding environment.

It is not just in Japan that methane hydrates are of interest, however, and scientists in the US recently returned from a research expedition in the northern Gulf of Mexico with the best high-resolution seismic data and imagery ever obtained of sediments with high gas hydrate saturations.

The expedition and the data and imagery collected resulted from longstanding co-operation between the US Geological Survey (USGS) and Bureau of Ocean Energy Management (BOEM) and the US Department of Energy (DOE). The collaboration aims to advance scientific understanding of gas hydrates.

“This expedition represents a significant milestone,” said USGS energy resources programme co-ordinator Brenda Pierce. “The data and imagery provide insight into the entire petroleum system at each location, including the source of gas, the migration pathways for the gas, the distribution of hydrate-bearing sediments, and the traps that hold the hydrate and free gas in place.”

Using low-energy seismic sources, USGS scientists collected details about the nature of the gas hydrate reservoirs and about geologic features of the sediment between the reservoirs and the seafloor. The new data also provide information about how much gas hydrate exists in a much broader area than can be determined from using standard industry seismic data, which is typically designed to image much deeper geologic units.

“Understanding the nature and setting of deepwater gas hydrates is central to the National Methane Hydrates R&D Programme, which is led by DOE and managed by Fossil Energy’s National Energy Technology Laboratory,” said Christopher Smith, DOE’s acting assistant secretary for fossil energy. “Over the past eight years, research carried out under this programme has resulted in significant advances in our understanding of methane hydrates, their role in nature, and their potential as a future energy resource. This success is largely due to an unprecedented level of co-operation among federal agencies, industry, national laboratories, and academic institutions.”

“The high-resolution nature of the data acquired through the project will inform the BOEM effort to assess the resource potential of gas hydrates on the US Outer Continental Shelf,” said Renee Orr, chief, strategic resources office, BOEM.

The data was collected at two locations in the Gulf of Mexico where the three federal agencies partnered with an industry consortium to conduct a drilling expedition in 2009. That expedition discovered gas hydrate filling between 50 and 90 per cent of the available pore space between sediment grains in sandy layers in the subsurface. The reservoirs are expected to be representative of the 6,700 trillion cubic feet of gas that BOEM estimates is housed in gas hydrates in sand-rich reservoirs in the northern Gulf of Mexico.

The data is being used to refine estimates of the nature, distribution, and concentration of gas hydrate in the vicinity of the 2009 drill sites. This will help assess how useful specialised seismic data may be to estimating hydrate saturations in deepwater sediments. In coming years, the three agencies will continue their collaborative investigation of gas hydrates in the northern Gulf of Mexico and other locations across the world.

A collaborative project between the National Oceanography Centre (NOC) and the University of Southampton in the UK is seeking to improve geophysical remote sensing of seafloor methane gas and hydrates through innovative laboratory experimental and theoretical studies.

Researchers will develop a laboratory instrument capable of simulating the high pressures and low temperatures needed to create methane hydrates in sediment samples and carry out acoustic and electrical properties experiments. The results will be used to develop theory for modelling geophysical survey data in terms of seafloor gas and hydrate content.

Dr Angus Best of NOC and professors Tim Leighton and Paul White from the University of Southampton’s Institute of Sound and Vibration Research (ISVR) have been awarded a grant of £0.8 million by the Natural Environment Research Council (NERC) to investigate methods for assessing the volume of methane gas and gas hydrate locked in seafloor sediments.

Dr Best, who is leading the project, explained that, currently, there are only very broad estimates of the amount of seafloor methane and hydrates. Improvements to geophysical remote sensing methods, especially acoustic methods, offer a way to better assess this important store of greenhouse gas.

Apart from being a potentially important energy source, scientists want to learn more about methane hydrate’s possible impact on ocean acidification and global warming if seafloor methane were released in to the water column or atmosphere. It is thought that methane hydrates could also contribute to geo-hazards such as seafloor landslides – it is thought that earthquakes and the release of gas hydrates caused the largest-ever landslide, the Storegga Slide, around 8,000 years ago.

The team plans a series of experiments on a range of sediment types, such as sand and mud. They intend to map out the acoustic and electrical properties of differing amounts of free methane gas and frozen solid methane hydrate.

The laboratory-based approach adopted by the team will involve the development of a major new acoustic pulse tube instrument at NOC. Using acoustic techniques and theories developed by the ISVR team, they aim to provide improved geophysical remote sensing capabilities for better quantification of seafloor gas and hydrate deposits in the ocean floor.

“Not much is known about the state of gas morphology – bubbles. Muddy sediments show crack-like bubbles, while sandy sediments show spherical bubbles. Only dedicated lab experiments can hope to unravel the complex interactions. By creating our own ‘cores’ of sediment material in a controlled environment where we know the concentrations of methane, we can create models to help us with in situ measurements on the seafloor.”

Professor Leighton said: “As a greenhouse gas, methane is 20 times more potent per molecule than carbon dioxide. There is the potential for climate change to alter sea temperatures and cause more methane gas to be released from seabed hydrates into bubbles which reach the atmosphere. It is therefore vital that we have the tools to quantify and map the amount of methane that is down there.” OSJ

“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.”

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.

Getty Images

Japan has been researching the potential of flammable ice for decades, but it is only within the last few years that extraction has come within reach (Credit: Getty Images)

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

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.

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.

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.

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.

“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.

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.

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.

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.

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Record breaking

Recent news of China’s success in producing gas from sub-sea methane hydrates has re-ignited the emergence of these deposits as a possible alternative energy source, which could usher in a new energy revolution. On 9 July 2017, China announced that it had achieved continuous gas production from hydrates during a 60-day trial, located ~300km SE of Hong Kong, and at depths of 203m-277m beneath the seafloor (1,266m water depth), in Shenhu Area of the South China Sea. Using the CNPC-owned Bluewhale 1, a semi-submersible which was domestically designed and constructed, China set a new world record producing a total of 309,000 cubic metres (cm) of gas (~10.9 million cubic feet of gas (MMcfg)). The average production during the trial was 5,151cm per day (~181 thousand cubic feet of gas per day (Mcfg/d)) and the gas was reported to have had a methane content of up to 99.5%. The trial has been heralded as a breakthrough in the search for alternative, cleaner energy sources; however, China isn’t the only country pursuing the colloquially named ‘fire-ice’, as countries including Japan, India, South Korea, and the United States are all actively investing into research and development of the unconventional resource.

What is ‘fire-ice’?

Methane hydrates or ‘fire-ice’ is a globally distributed fossil fuel. It is composed of methane trapped inside a lattice of water molecules, which forms a white, energy-dense substance that can be easily ignited, like solid ethanol. The hydrates form at relatively shallow sub-surface depths, in high pressure and low temperature environments, typical of outer continental margins and permafrost areas. Once the substance is heated and depressurised to normal conditions, 1cm of hydrates equates to ~164cm of regular natural gas. The gas consists of 80-99.9% methane and produces much less pollution than coal and oil when burned – estimates suggest that natural gas emits just 60% of the carbon emissions generated by coal, and 80% of the emissions generated by oil.