New Scientist Magazine piece on Microwave Alternative to Fracking
Forget fracking, microwave zaps could clean up the oil business
Microwaves could deliver plentiful fuel while dodging fracking’s downsides. So why aren’t we
doing it already?
(Image: Spencer Wilson)
WHEN Peter Kearl waxes lyrical about microwaves, he’s not thinking about rustling up a quick
dinner. An engineer who once worked at the Oak Ridge National Laboratory in Tennessee, Kearl
sees microwaves as the answer to our energy woes. As the world debates whether fracking for oil
and gas is an economic godsend or an environmental nightmare, Kearl thinks zapping the ground
with microwaves could provide a cleaner, greener way to get those fuels out. He also knows how
the idea will sound to most people. “We’re still trying to convince people that this is not
something out of Star Wars,” he says.
Perhaps not for much longer. Big names such as BP and ConocoPhillips are also warming to an
idea that, its proponents argue, could provide a cheap new source of oil and gas to bridge the gap
while renewables get off the ground. Not only that, it could also store carbon, keep us from
digging up pristine areas – and even generate clean water.
Too good to be true? Fracking, too, was once described as a “blue bridge to a green future”, but
many would argue that any plan to extract yet more carbon-producing fossil fuel from the ground
can never be a good idea. With microwave zapping, are we heading for fracking mark two?
“Fracking, too, was once described as the bridge to a carbon-neutral future”
Fracking is a corrosive and violent way of getting oil and gas from the ground – because it has to
be. Hydraulic fracturing, as the technique is more properly known, involves injecting water and
chemicals into the ground, and is often combined with horizontal drilling to extract oil and gas
from difficult geology, most notoriously shale, a fine-grained sedimentary rock. In the US, it has
transformed the energy landscape, aiding a switch from coal-fired power plants to natural gas,
which emits half the carbon dioxide of coal. Indeed, fracking may be one reason that, in 2012,
the US met the emissions targets of the Kyoto protocol without ever having ratified it.
For all its benefits, the controversies over fracking are mounting up (Image: Ted Wood/Aurora
Photos)
But there’s still a price to pay, not least that fracking requires a lot of water. Every year, 35,000
US fracking wells use up to 525 billion liters, about what 3.8 million US citizens would use in a
year.
Opponents of fracking highlight how the practice depletes underground aquifers, or depends on
water brought in from afar in diesel-exhaust-belching trucks. And fracking fluid is a nasty
cocktail, containing hydrochloric acid to clear out cement debris from drilling or to break down
limestone, plus corrosion inhibitors, friction-reducing agents, viscosity reducing agents and
biocides, to name just a few.
Although concerns about fracking-induced earthquakes have proved largely overblown, the
escape of large amounts of greenhouse gases from poorly sealed wells also gets many people hot
under the collar. Add all that together and it’s easy to understand the interest in microwaves.
Microwaves can exploit an underappreciated feature of some hydrocarbons: while they can be an
asphalt-like solid at room temperature, they become liquid with a little heating. The trouble is
getting the heat down into the kinds of permeable rocks that trap oil and gas.
We’d never found a good way to do it. Porous rock is an excellent thermal insulator, so electric
heaters don’t work. Injecting steam – a technique sometimes used in conventional wells to make
heavy crude oil and bitumen less gloopy – can heat up a section of rock but won’t work past
obstructions. The best option could be to lower a high-power, 2.45-gigahertz emitter – essentially
a supercharged microwave oven – into the ground.
The idea that a microwave antenna might do the job has actually been around for a while.
However, equipment that can create, steer and stabilize the beam was too bulky to fit down a
narrow well. Now, designs that will soon make the technology cheap and commonplace are
emerging from small outfits, including one Kearl has set up, and from the defense industry.
But just as a ceramic mug in a microwave oven remains cold to the touch while its contents
warm up, porous rocks don’t heat up when zapped with microwaves. The trick is that any water
trapped in their pores will. If that is mixed up with solid hydrocarbons, the boiling water will
heat and liquefy these. The water then turns to steam, and everything can flow through the
cleared pores and cracks to be collected at the surface (see diagram).
The overall effect is similar to fracking, but with none of the chemicals or contaminated water.
The steam ensures oxygen stays at levels too low to be easily flammable, meaning there is no
risk of underground fires. And while the beam might cook any microorganisms in its immediate
path, it will do less damage than the acidic mix in fracking fluid. “It’s more efficient, with less
impact on the environment,” says Kearl.
After developing his microwave system at Oak Ridge, in 2013 Kearl formed a company called
Qmast in Grand Junction, Colorado, to bring the technology to market. He’s not the only one.
Last year, ConocoPhillips published a patent to use microwaves to liquefy and extract
subterranean oil.
But Kearl thinks there is another, immediate use for his technology: to unblock existing oil and
gas wells that have become too sluggish to be worth operating. In oil wells, this happens when
paraffin wax and other impurities build up in the conduits to the pipe. Similarly, fracking well
production declines quickly when the shale absorbs water, causing the rock to swell and squeeze
into the fractures and block the gas’s exit. Many of these wells are abandoned despite there being
plenty of remaining oil or gas, and new wells are dug. If microwaves can melt paraffin and boil
off water, blocked wells will flow like new. “They could be effectively rehabilitated by
microwave heating,” says Kearl.
This could help protect environmentally sensitive areas. “If we can produce more oil from old
wells, that would lessen interest in drilling for new sources of oil,” says Stephen Brown, an
energy economist at the University of Nevada, Las Vegas.
Kearl’s method is not the only way that microwaves can clean up after the oil and gas industry.
John Robinson and his colleagues at the University of Nottingham, UK, are developing a system
to dislodge oil trapped in drill cuttings, the contaminated sand left by the drilling process in a
conventional well. When the team zaps the mix with microwaves, the heating of any water
mixed in with the heavy oil makes oil dribble out, leaving basically clean sand. BP has funded
Robinson’s team to extract oil from cuttings left by its ocean platforms, making the cuttings safe
to put back into the ocean.
The same process can coax oil from tar sands, a forbidding mixture of sand, clay, water and
bitumen – a heavy oil sludge that has resisted all efforts to pump it from the sands. The only way
to do it is by strip mining or open pit mining, which means tearing up the ground with large
hydraulic shovels. This has led to protests in tar sand hotspots like Canada, where mining has
razed thousands of square kilometres of boreal forests. Like shale, however, these “low-grade”
tar sands might succumb to zapping – thanks to their payload of water, trapped in this case
within the crystal structures of small particles called clay fines. Robinson says his group’s longterm goal, like QMast, is to use microwave heat for large-scale production of hydrocarbons.
“If microwave technologies can eliminate the need for water and chemicals in hydraulic
fracturing, that would be a significant advance,” says Rob Jackson, an earth systems scientist at
Stanford University in California. Indeed, rather than consuming vast quantities of water as
fracking does, zapping could even unlock fresh water supplies.
When Robinson’s technique turns the water in tar fines to steam, it yields not just oil but water
pure enough to drink. Tar sands are only about 1 per cent water, but oil shale’s water content can
approach 20 per cent. Current methods of oil and gas extraction use two to five barrels of water
per barrel of oil produced, says Eleanor Binner, an engineer on Robinson’s team.
“Microwave extraction can yield not just oil, but water pure enough to drink”
By contrast, Kearl says, oil-producing rocks – for example the Green River formation in the
western US, which contains the largest oil shale deposit in the world – would yield a barrel of
water for every two barrels of oil. “The hydrocarbons and water can be easily separated once
condensed,” says Robinson.
A question of scale
Still, there are reasons not to be wildly enthusiastic just yet. Jackson, for one, points to the small
scale of the microwave testing done so far in the lab. “Bench-top experiments are a good first
step, but they’re a long way from a well that’s a mile deep and a mile wide,” he says. So far, a
complex mixture of chemical agents has been needed to get hydrocarbons to flow over that
distance.
Kearl insists that the technique can scale up, and says QMast has extensively modelled and labtested the interaction between microwaves and shale. Like fracking, he says, microwaves can
reach deep into the rock surrounding a borehole – and the more liquid is removed, the further
into the rock they penetrate. “Once the water and oil are removed, the rock is basically
transparent to the microwaves and heating continues at increasing distances from the well,” he
says. For now, the beam has a range of around 25 meters.
His claims are backed up by Matteo Bientinesi and his group at CPTM, a research center in
Cecina, Italy – albeit with some caveats. When they used 2.45-gigahertz microwaves to heat 2
tons of oil sand to over 200 °C in the lab, they identified a potential problem. Just as in
microwaved lunch pots, some areas may overheat while others remain undercooked. They solved
the problem with better antenna design and reservoir modeling, but the lesson was clear: “The
technique must be adapted to the properties of the reservoir,” says Bientinesi.
A far bigger hurdle is the technique’s hunger for energy. In principle, microwave zapping “uses
less energy than conventional extraction”, says Robinson. However, that saving is lost once you
factor in inefficiencies associated with running the microwave antenna on electrical power. Kearl
says microwaving should produce oil for $9 a barrel – cheaper than other niche methods, but
merely on a par with fracking and other conventional extraction. So while there are reasons to
adopt microwave zapping, saving on the cost is not among them.
For the same reason, microwave extraction offers no cuts in carbon emissions. To improve on
this, Kearl plans to use the cavities created during microwave heating to store carbon dioxide
produced by the antenna’s electrical power source. Combining fracking with CO2 sequestration
has been proposed before to bring emissions down, but mining firms have been slow to take it
up.
Another way to lower emissions would be to power the antenna on renewable energy. For
example, Colorado’s oil shale deposits lie in a windy region, one where turbines would provide
ample power.
Others see a broader philosophical problem. Although microwave heating would make existing
oil and gas extraction more environmentally acceptable, there is no guarantee that it won’t allow
mining to encroach on new areas – for example, the vast volumes of inaccessible bituminous oil
in shallow deposits like Green River, that would otherwise never leave the ground.
That would be a disaster, says James Hansen, a climate scientist at Columbia University in New
York. “Discovering new ways to extract still more fossil fuels is crazy from a global or national
strategic perspective,” he says, because it will increase emissions and discourage the
development of renewables.
But Robinson doesn’t see it that way. Emissions or not, he and others view the microwave
process as a necessary bridge to a low-carbon economy. “We need to keep going with
hydrocarbons, to drive the economy and enable investment in renewables,” he says.
“Renewables are in no shape to take over just yet. The only way we can afford to develop them
is by extracting hydrocarbons.”
Enthusiasts for fracking, of course, made a similar argument, describing it as the bridge to a
carbon-neutral 21st century. We now know that although fracking has enormous benefits,
horizontal fracturing is being used to access deep coal seams previously beyond our reach. That
provides access to enough fuel to warm the Earth by many degrees. What unforeseen
consequences will microwaves bring about?
For now, it may be a moot point: the biggest obstacle to microwave extraction is not technical,
political or environmental, but the state of the oil market. Having been at more than $100 a barrel
for some years, the price of oil began to plummet late last year and is now teetering around $50 a
barrel, with little prospect of regaining its previous heights. Faced with an oversupply of oil,
there is little incentive for companies to invest in new extraction technologies.
That means the funding pipeline is sluggish – except for remediation projects, says Bientinesi.
For now, his team, like Robinson’s, is focusing on environmentally beneficial applications over
possibly damaging oil extraction. To extend Kearl’s Star Wars metaphor, it remains to be seen
whether higher oil prices tempt microwave zapping to the Dark Side.
This article appeared in print under the headline “Oil on zap!”
By David Hambling
David Hambling is a writer based in London
Magazine issue 3034 published 15 August 2015