Gas on Ice
Once dubbed an energy pipe dream, the prospect of extracting significant quantities of natural gas from frosty hydrate deposits just got a major boost. Scientists have demonstrated for the first time that they can produce natural gas from an existing gas hydrate deposit in nature. An international consortium of researchers and gas industry experts met in December in Tokyo to discuss results from an experimental drilling project conducted at the hydrate-rich well site known as Mallik, in the Mackenzie Delta of northern Canada.
Hydrate forms when gas, usually methane, mixes with water under just the right temperature and pressure conditions. A lattice-work of frozen water molecules encases each molecule of the gas, creating a flammable, ice-like substance. When it was first discovered in the 1950s, hydrate was considered a nuisance, often clogging pipelines at drill sites. Hydrates were a “gold-plated pain in the rear,” says gas industry veteran Robert Maddox, an emeritus professor of chemical engineering at Oklahoma State University.
In the past few decades, however, interest in hydrate has soared. The biggest reason for hydrate’s appeal is the sheer volume of deposits buried beneath marine sediment and permafrost regions of the globe. Keith Kvenvolden, senior scientist (emeritus) at the U.S Geological Survey, estimates that the world’s total supply of hydrate is more than double the amount of all other known fossil fuel deposits combined. If we could produce gas from only 1 percent of all the hydrates in the world, says USGS researcher Tim Collett, we would have enough natural gas to last more than 170,000 years at the present U.S. consumption rate of 23 trillion cubic feet annually.
Drilling for gas hydrates in the Mackenzie Delta of the northwestern Canadian Arctic. Images courtesy of USGS.
As a source for natural gas, hydrate today is about where coal bed methane was 15 years ago, says Michael Max, a hydrate expert formerly with the Naval Research Laboratory in Washington, D.C. “Coal bed methane was a classic, unconventional gas play,” with more than a few doubters, Max says. “Now it supplies around eight percent of the U.S natural gas supply. We think hydrate has a similar trajectory.”
Yet hydrate’s evolution has, until the December announcement, hinged on the giant “if” of technical feasibility. Engineers and geoscientists worked for years studying how changes in temperature and pressure affect hydrates in deposit. Reduce pressure or increase temperature just enough, and hydrate will melt. When that happens, the gas and water molecules go their separate ways and the gas, everyone assumed, could then be captured much like gas from conventional deposits. Computer models had predicted the resulting release of gas, but the idea had never been tested, making the successful melting and recapture of natural gas at Mallik a milestone for energy science.
The Mallik project followed years of research into the behavior of melting hydrate, as well as geophysical assessments of the Mallik deposits themselves. For the most recent findings, scientists used fiber optics instruments to characterize conditions within the different wells, together with seismic studies to estimate the extent to which released methane might seep into the surrounding geologic formations. After that, it was time to melt the hydrate-first through depressurization and then through heating, both of which proved to be effective methods for releasing methane that could then be captured. So much was known about the wells that the team was able to adjust the rate of hydrate dissociation, and thus the rate of gas release.
What’s more, Mallik also demonstrated that large amounts of natural gas are likely to be attainable in areas with high concentrations of hydrate. Because this was a first-time endeavor, scientists weren’t after maximum well output, but rather a carefully controlled reaction that could then be analyzed with greater precision. Yet models built using the Mallik data suggest that production could indeed yield rates of “several million cubic feet of gas per day,” says Collett-an output as good or better than that of conventional gas well. That could make hydrates a significant addition to global natural gas supply-especially in resource-poor parts of the world.)
Though countries from Canada to India have been investing heavily in hydrate research, the biggest effort has been in Japan. With the world’s second-largest economy, Japan imports roughly 98 percent of its oil and gas, and the Japanese are itching to find a domestic energy resource. Off the eastern coast of the main island of Honshu is a massive hydrate deposit similar in composition and concentration to the Mallik site, which helps explain why Japan bankrolled the bulk of the Mallik project. Some Japanese industry leaders have gone as far as to claim that hydrate development will make Japan energy self-sufficient by 2015.
That may be overly optimistic. For one thing, Japan may not have enough hydrate within its borders to power the country. It is also too soon to say whether other deposits would be as cooperative and productive as Mallik was in this first set of tests. In addition, the economics of hydrate production are not yet competitive with oil and gas from conventional sources. Nevertheless, the unpredictability of global energy markets (the price of natural gas, for example, was surging just before the New Year), the almost pathological commitment of the Japanese when it comes to energy security, and the money being thrown at hydrate research collectively indicate that gas from hydrate may very well play a major role in our energy picture over the long term.
A hydrate-rich energy future is not, of course, inevitable. For one thing, recent discovery and development of enormous new natural gas reservoirs means that conventional supplies of gas will be on hand for a long time to come. Economic viability remains the key wild card: no company will invest in the science and infrastructure needed to extract gas from hydrate if they can make more money finding and tapping conventional wells. And lastly, though burning natural gas is far cleaner than burning oil or coal, it does emit greenhouse gases. “If we get serious about climate change, we’ll have to look beyond carbon-based fuels, whether to solar, nuclear or something totally new. In that sense, we could be leaving all that hydrate untouched where it is,” says David Victor, Director of Stanford’s Program on Energy and Sustainable Development.
Still, knowing that it is technically feasible to unlock gas from hydrate means development of this resource is possible. And than means more choices about fueling the future.
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