Tech Briefs Magazine - February 2021 - 11

Q A

Who's
Who
&
at NASA

SEAL
and

Oil and Gas Wells for Energy Storage
Professor Iraj Ershaghi
and a team of researchers at the University of
Southern California (USC)
found a way to use idle
oil and gas wells for energy storage - one of the
major concerns for solar and wind energy generation.

sure of formation could be, for example,
3,000 pounds per square inch. When you
produce from that for a couple of days,
the pressure drops very rapidly. Then, the
compressor automatically brings the pressure back up. When the stored energy is
needed, the air rises to the surface and
pressurizes a container of water to run a
turbine-powered generator.

Tech Briefs: Where did this idea
come from?

Tech Briefs: So, you're using
existing technology but applying it
in a way that's more economical
and useful.

Professor Iraj Ershaghi: A major problem is what to do with the large number
of oil and gas wells that have reached the
end of their productive lives and have to
be permanently abandoned. I had been
thinking about what the engineering
community could do to reduce abandonment cost and do it more effectively.
A company approached us and said they
would like to work with USC to deal with
a problem facing the renewable energy
industry - energy storage.
I was aware that the McIntosh Power
Company Alabama had drilled into
huge geological structures made of salt,
called salt domes. They created cavities
in them to store compressed air during
times when an energy source is producing excess power. When they need to use
the stored energy, they release the compressed air to run a turbine that produces electricity. Although we don't
have salt domes in California, we know
that as you go from the surface all the
way down to the sub-surface hydrocarbon zones, there are layers of sandstone
full of ancient saline seawater.
Tech Briefs: How would this work?
Ershaghi: The oil and gas could be
sealed off with cement 9,000 feet below
the surface. Above that, there might be
hundreds of feet of sandstone containing
saltwater, perhaps 5,000 feet below the
surface. If a solar energy source is producing excess power, we can use that to run
an air compressor to force air into the saltwater-bearing sandstone. Because water
has a low compressibility, its stored pres-

Ershaghi: It's a proven technology -
having stored air in salt domes. Our first
contribution is that you don't require a
salt dome - as long as you have a saline
aquifer, that could do the job. The
impression is that this is costly because
you have to drill the well. But we've
shown that we could use existing wells
that are destined for abandonment.
That's the idea. So, essentially use the
idle wells, use a saline aquifer, and
expand the technology to make it widely
available, while reducing the liability to
the states and the public for the well
abandonment costs.
Tech Briefs: What are the economic
incentives for building these
systems?
Ershaghi: If I'm an operator who owns
a number of wells - some of which are
economically unproductive - this could
be a source of income. If I convert those
abandoned wells to storage, I could
charge a utility for the right to use them.
The operator would then have a source
of income from these non-producing
wells. Meanwhile, the operators eliminate
or postpone the abandonment cost. This
could also be a new source of income for
landowners: leasing their subsurface
rights to storage operators. Utilities
would find it worthwhile because they
could reduce the amount of oil and gas
they need to generate power.
Read the full transcript of this Q&A at
www.techbriefs.com.

Tech Briefs, February 2021

www.techbriefs.com

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Tech Briefs Magazine - February 2021

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