MIT: Fugitive Methane Emissions From Shale Gas Wells Overstated
The State Journal
29 November 2012
By Pam Kasey
Fugitive methane emissions from completion of shale gas wells have
been overstated, according to a new study from the Massachusetts
Institute of Technology.
These emissions may be significant, at 3.6 percent of fugitive
emissions from the industry, according to "Shale gas production:
potential versus actual greenhouse gas emissions," published Nov.
26 in the peer-reviewed journal Environmental Research Letters.
But field practices are managing more of the potential emissions
than other researchers have asserted.
It was long and widely said that natural gas emits half the
greenhouse gases of coal, a generalization based on a comparison
of carbon dioxide emissions when the two are burned for
But a 2011 study from Robert Howarth of Cornell University looking
at the "lifecycle" extraction–to–end use greenhouse gas footprint
of shale gas set off a public debate.
Howarth's study found that, when operators who use high-volume
hydraulic fracturing into shale formations "complete" their wells
— that is, make them ready for production — they release large
volumes of methane, a far more potent greenhouse gas than carbon
The study estimated that, including methane released during
completion and methane leaked afterward during processing,
transmission, storage and distribution, as much as 8 percent of a
shale well's final volume could be lost to the atmosphere. The
study concluded that the global warming potential of shale gas
exceeds that of coal over a 20-year time frame and is comparable
over a 100-year time frame.
While a spate of estimates since that time have ranged, generally,
from 2 to 10 percent of total production volume released as
fugitive emissions, scientists coming in all across that spectrum
have agreed that much of the fugitive methane is released
specifically during the week or so of well completion.
The MIT study disagrees.
The researchers looked at production data on 4,000 new wells in
the five most productive shale formations in 2010 — Barnett,
Fayetteville, Haynesville, Marcellus and Woodford shales.
Data on the key question of emissions during well completion are
scarce, they acknowledged.
"Significant opaqueness surrounds real world gas handling
practices in the field, and what proportion of gas produced during
well completions is subject to which handling techniques," they
Howarth, they wrote, assumed that all potential fugitive emissions
are vented. The U.S. Environmental Protection Agency has assumed
that half of fugitive emissions are vented.
The MIT researchers themselves referenced an industry-sponsored
survey of practices used at about 1,600 wells — acknowledging its
industry source but noting that it is the most comprehensive study
available — and supplemented that information with interviews with
industry, the EPA and others.
They concluded that methane generated during well completion is
captured at 70 percent of wells, flared at 15 percent and vented
at only 15 percent.
That reduces fugitive emissions from an average potential of 228
megagrams of methane per well to their estimate of 50 megagrams
Overall, according to their calculations, 0.4 percent to 1.0
percent of a well's ultimate production volume is lost through
An April 2012 rule from the EPA requires operators to flare their
gas during completion or to capture it rather than venting it.
But this study suggests that shale well completion is not
necessarily a hot spot for controlling gas-industry emissions —
that emissions come, rather, from points throughout the gas
production, processing, transport and delivery processes.
"Although fugitive emissions from the overall natural gas sector
are a proper concern, it is incorrect to suggest that shale
gas-related hydraulic fracturing has substantially altered the
overall greenhouse gas intensity of natural gas production," they