Injection wells at the Superb oil field in Canada. To make hydrogen, workers heat the reservoir with steam and feed it air, setting off underground oil fires.

This month, on the frozen plains of Saskatchewan in Canada, workers began to inject steam and air into the Superb field, a layer of sand 700 meters down that holds 200 million barrels of thick, viscous oil. Their goal was not to pump out the oil, but to set it on fire—spurring underground chemical reactions that churn out hydrogen gas, along with carbon dioxide (CO2). Eventually the company conducting the $3 million field test plans to plug its wells with membranes that would allow only the clean-burning hydrogen to reach the surface. The CO2, and all of its power to warm the climate, would remain sequestered deep in the earth.

“We want to launch the idea that you can get energy from petroleum resources and it can be zero carbon emissions,” says Ian Gates, a chemical engineer at the University of Calgary and co-founder of the startup, called Proton Technologies.

Markets are growing for hydrogen as a fuel for power, heat, and transport, because burning it only releases water. But most hydrogen is made from natural gas, through a process that spews carbon into the air, or by electrolyzing water, which is pricey. Proton Technologies says it can cut costs by relying on oil reservoirs shunned by drillers because they are water-logged or because their oil is too thick. “Someone’s abandoned liability becomes our hydrogen field,” says CEO Grant Strem, who bought the Superb field out of bankruptcy.

Geoffrey Maitland, a chemical engineer at Imperial College London, says he is a “great fan” of the concept, which treats the oil reservoir as a hot, naturally pressurized reactor. “This chemistry is well-proven at the surface,” he says. “The challenge is controlling these processes several kilometers underground.”

Industry has experimented for decades with underground burning, also known as fire flooding. Fed by air or oxygen pumped into the ground, the fire releases gases that can push oil toward wells, and its heat can soften tarlike bitumens and other heavy oils, making them easier to pump. In the early 1980s, fire-flooding tests on an oil field called Marguerite Lake, in Canada’s vast oil sands, produced substantial amounts of hydrogen as a byproduct. No one cared very much at the time, but the finding sowed “the seed of the idea,” Gates says. “What if we only produce hydrogen out of the reservoir?”

In a 2011 paper in the journal Fuel, he and his colleagues sketched out how it could work. The first step would be to use steam to heat a reservoir to 250°C or so and add air or oxygen to touch off combustion. The heat “cracks” the oil’s long hydrocarbon chains into smaller pieces and produces small amounts of hydrogen. But if the fire reaches temperatures above 500°C, injected steam or water vapor from the hot reservoir itself will react with the hydrocarbons to make syngas: a mixture of carbon monoxide and hydrogen. Adding more water to the syngas sets off a final reaction that produces CO2 and more hydrogen.

The main obstacle will be raising temperatures above 500°C with in situ combustion, which is “complicated and not easy to control,” says Berna Hascakir, a heavy oil reservoir engineer at Texas A&M University, College Station. Gates says the reactions can still proceed below 500°C, just less efficiently. “Ideally, we’d like to get hotter,” he says. “But those temperatures are fine to produce meaningful amounts of hydrogen.”

Another challenge is separating the produced hydrogen from the CO2 and other impurities in the mix, such as toxic hydrogen sulfide. Strem says the company will use thin membranes made of palladium alloys, which will decompose hydrogen gas into individual hydrogen atoms. Those atoms will diffuse through the metal lattice, then combine to form hydrogen gas again on the other side. But palladium membranes can be fragile and finicky, even when used at the surface, notes Jennifer Wilcox, a chemical engineer at Worcester Polytechnic Institute. “When doing everything underground, it’s difficult to have control.”

For now, Proton Technologies will use their membranes at the surface and vent the separated CO2. But if the company can raise roughly $50 million for the next field test, Strem would like to test the membranes deep in the wells. He also wants to buy an air separation unit and inject pure oxygen into a reservoir, which would make it a hotter and more efficient reactor. He hopes to produce commercial amounts of hydrogen in the coming months and says the company could eventually produce the gas for between 10 and 50 cents per kilogram—significantly cheaper than current sources.

The vast majority of the world’s produced hydrogen is used to refine petroleum products and make ammonia fertilizer. But the market for hydrogen as a green fuel is growing, says Ken Dragoon, executive director of the Renewable Hydrogen Association. In pilot projects, utilities are injecting small amounts of hydrogen into natural gas pipelines for home heating and appliances. In transportation, he says, fleets of trains, buses, and forklifts are turning to hydrogen fuel cells, which offer a longer range and much faster refueling than the other green alternative, electric batteries.

Dragoon, an advocate for renewable hydrogen made with electrolyzers, would be happy to see a competitor like Proton Technologies. “We need everything we can,” he says. “If it’s safe, and it produces a climate neutral fuel, more power to them.”

Via ScienceMag.org