Laser-Based System Offers Continuous Monitoring of Leaks from Oil and Gas Operations

Nobel-prize winning technology measures small methane leaks in large
outdoor area

WASHINGTON–(BUSINESS WIRE)–#ARPAE–Researchers have conducted the first field tests for a new laser-based
system that can pinpoint the location of very small methane leaks over
an area of several square miles. The new technology could one day be
used to continuously monitor for costly and dangerous methane leaks at
oil and gas production sites.

As a primary component of natural gas, methane can leak during normal
oil and gas production or through unknown leaks in production
infrastructure. These leaks not only cost oil and gas companies money
but also contribute to climate change and can be dangerous to people.
Today, a person or team must travel to different sites to check for
leaks with a special camera that is sensitive to methane at close
distances. This approach is time consuming and could miss methane leaks
that are intermittent in nature.

“Our approach allows measurements to be autonomous, which enables
continual monitoring of an area,” said co-lead author of the study Sean
Coburn, from the University
of Colorado in Boulder. “This technology could play a significant
role in reducing methane emissions from production activities, easing
tension between urban development and oil and gas production and helping
avoid disasters like the 2015 Aliso Canyon methane storage leak that
released 90,000 metric tons of methane into the atmosphere.”

In Optica,
The Optical Society's journal for high impact research, researchers from
the University of Colorado, the National Institute of Standards and
Technology (NIST)
and the National Oceanic and Atmospheric Administration (NOAA)
showed that their system can uniquely detect slow, low-volume methane
leaks from a kilometer away in an outdoor setting. They demonstrated
that the system can detect leaks with a flow rate equivalent to just 25
percent of a person’s resting breathing rate.

The method could also be used to measure other gases to provide new
insights into air pollution.

“Our system is based on frequency comb laser spectroscopy, which stemmed
from the Nobel-prize winning work of Jan Hall at University of
Colorado,” said Coburn. “Because of recent advances, we were able to
take this technology out of the lab and use it in the field for the
first time. Combining this precision spectroscopy technique with new
computational methods allowed us to pinpoint methane sources and
determine emission rates with unparalleled sensitivity and range.”

Fast, precise analysis

Methane and other gases absorb light at specific infrared wavelengths,
creating an absorption spectrum that can be used like a fingerprint to
detect gases in the air. The new system uses a scanning laser beam with
discrete reflectors placed around the field to determine the amount of
methane in air that intersects each beam path. Comparing measurements
from two laser beam paths shows if a leak is present in the area between
the paths. The exact location and size of the leak is determined using
newly developed methods which utilize atmospheric models that simulate
how gases are moving across the area at the time of the measurement.

A key component of the system is a frequency comb laser, which emits
hundreds of thousands of infrared wavelengths, rather than the one
wavelength emitted by traditional lasers. Using this type of laser for
spectroscopy enables fast measurements over a broad range of wavelengths
with very high resolution, which proved important for distinguishing
gases that absorb at similar wavelengths such as methane and water.

“The change in methane concentration downwind from a small leak is about
the same as the change in methane due to dilution by water vapor that
occurs when a rainstorm starts,” explained Gregory Rieker, principal
investigator on the methane sensing technology development project.
“Laser frequency comb spectroscopy allows us to simultaneously, and
accurately, measure water vapor and methane. This lets us correct for
water in the air, which is critical for detecting very small increases
in methane over a large area.”

The system also calculates background methane concentration, which can
change as the wind shifts. This is critical for distinguishing a tiny
leak from a change in the overall methane concentration in the air.

“A large proportion of the methane emissions that contribute to
greenhouse gas emissions from oil and gas are thought to be from
intermittent leaks,” said Caroline Alden, co-lead author on the study.
“To detect and analyze these types of leaks continuously, we developed
computational methods that provide a history of how emissions vary over
time.”

Outdoor methane measurements

The researchers demonstrated the system in a series of tests
designed to mimic scenarios that could be faced in an oil and gas field.
They housed the frequency comb laser in a mobile trailer and generated
multiple beam paths that each covered about a kilometer to a low-cost
reflector.

For one experiment, the researchers configured the system to quantify a
small controlled leak about 1 kilometer from the mobile trailer and 50
meters from the laser beams. In addition to determining when the
controlled leak was active and how emission rates changed over 20 hours,
the researchers demonstrated measurements of emissions as low as 2 grams
per minute.

In another test, they placed five potential methane leaks at various
locations between multiple laser beam paths. The researchers were able
to pinpoint which sources were leaking and determine the emission rates
of those leaks.

In addition to continuing to refine the system and test it in various
scenarios, the researchers plan to work with industry partners to see
how the system will perform at actual oil and gas production sites.
Working with spin-off company Longpath Technologies, they want to
commercialize the technology as a detection service for the oil and gas
industry.

This research was conducting with support from the U.S. Department of
Energy’s Advanced Research Projects Agency-Energy (ARPA-E)
Methane Observation Networks with Innovative Technology to Obtain
Reductions (Monitor)
program. The Monitor program aims to foster the development of new
methane sensing technology that can be transferred to oil and natural
gas production.

Paper: S. Coburn, C. B. Alden, R. Wright, K. Cossel, E. Baumann,
G.-W. Truong, F. Giorgetta, C. Sweeny, N. R. Newbury, K. Prasad, I.
Coddington, G. B. Rieker, “Regional trace-gas source attribution using a
field-deployed dual frequency comb spectrometer,” Optica, Volume
5, Issue 4, 320-327 (2018).
DOI: 10.1364/OPTICA.5.000320

About Optica

Optica is an open-access, online-only journal dedicated to the
rapid dissemination of high-impact peer-reviewed research across the
entire spectrum of optics and photonics. Published monthly by The
Optical Society (OSA), Optica provides a forum for pioneering
research to be swiftly accessed by the international community, whether
that research is theoretical or experimental, fundamental or applied. Optica
maintains a distinguished editorial board of more than 50 associate
editors from around the world and is overseen by Editor-in-Chief Alex
Gaeta, Columbia University, USA. For more information, visit Optica.

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