3 research outputs found
Aerial Surveys of Elevated Hydrocarbon Emissions from Oil and Gas Production Sites
Oil
and gas (O&G) well pads with high hydrocarbon emission rates may
disproportionally contribute to total methane and volatile organic
compound (VOC) emissions from the production sector. In turn, these
emissions may be missing from most bottom-up emission inventories.
We performed helicopter-based infrared camera surveys of more than
8000 O&G well pads in seven U.S. basins to assess the prevalence
and distribution of high-emitting hydrocarbon sources (detection threshold
ā¼ 1ā3 g s<sup>ā1</sup>). The proportion of sites
with such high-emitting sources was 4% nationally but ranged from
1% in the Powder River (Wyoming) to 14% in the Bakken (North Dakota).
Emissions were observed three times more frequently at sites in the
oil-producing Bakken and oil-producing regions of mixed basins (<i>p</i> < 0.0001, Ļ<sup>2</sup> test). However, statistical
models using basin and well pad characteristics explained 14% or less
of the variance in observed emission patterns, indicating that stochastic
processes dominate the occurrence of high emissions at individual
sites. Over 90% of almost 500 detected sources were from tank vents
and hatches. Although tank emissions may be partially attributable
to flash gas, observed frequencies in most basins exceed those expected
if emissions were effectively captured and controlled, demonstrating
that tank emission control systems commonly underperform. Tanks represent
a key mitigation opportunity for reducing methane and VOC emissions
Constructing a Spatially Resolved Methane Emission Inventory for the Barnett Shale Region
Methane emissions from the oil and gas industry (O&G) and other
sources in the Barnett Shale region were estimated by constructing
a spatially resolved emission inventory. Eighteen source categories
were estimated using multiple data sets, including new empirical measurements
at regional O&G sites and a national study of gathering and processing
facilities. Spatially referenced activity data were compiled from
federal and state databases and combined with O&G facility emission
factors calculated using Monte Carlo simulations that account for
high emission sites representing the very upper portion, or fat-tail,
in the observed emissions distributions. Total methane emissions in
the 25-county Barnett Shale region in October 2013 were estimated
to be 72,300 (63,400ā82,400) kg CH<sub>4</sub> h<sup>ā1</sup>. O&G emissions were estimated to be 46,200 (40,000ā54,100)
kg CH<sub>4</sub> h<sup>ā1</sup> with 19% of emissions from
fat-tail sites representing less than 2% of sites. Our estimate of
O&G emissions in the Barnett Shale region was higher than alternative
inventories based on the United States Environmental Protection Agency
(EPA) Greenhouse Gas Inventory, EPA Greenhouse Gas Reporting Program,
and Emissions Database for Global Atmospheric Research by factors
of 1.5, 2.7, and 4.3, respectively. Gathering compressor stations,
which accounted for 40% of O&G emissions in our inventory, had
the largest difference from emission estimates based on EPA data sources.
Our inventoryās higher O&G emission estimate was due primarily
to its more comprehensive activity factors and inclusion of emissions
from fat-tail sites
Constructing a Spatially Resolved Methane Emission Inventory for the Barnett Shale Region
Methane emissions from the oil and gas industry (O&G) and other
sources in the Barnett Shale region were estimated by constructing
a spatially resolved emission inventory. Eighteen source categories
were estimated using multiple data sets, including new empirical measurements
at regional O&G sites and a national study of gathering and processing
facilities. Spatially referenced activity data were compiled from
federal and state databases and combined with O&G facility emission
factors calculated using Monte Carlo simulations that account for
high emission sites representing the very upper portion, or fat-tail,
in the observed emissions distributions. Total methane emissions in
the 25-county Barnett Shale region in October 2013 were estimated
to be 72,300 (63,400ā82,400) kg CH<sub>4</sub> h<sup>ā1</sup>. O&G emissions were estimated to be 46,200 (40,000ā54,100)
kg CH<sub>4</sub> h<sup>ā1</sup> with 19% of emissions from
fat-tail sites representing less than 2% of sites. Our estimate of
O&G emissions in the Barnett Shale region was higher than alternative
inventories based on the United States Environmental Protection Agency
(EPA) Greenhouse Gas Inventory, EPA Greenhouse Gas Reporting Program,
and Emissions Database for Global Atmospheric Research by factors
of 1.5, 2.7, and 4.3, respectively. Gathering compressor stations,
which accounted for 40% of O&G emissions in our inventory, had
the largest difference from emission estimates based on EPA data sources.
Our inventoryās higher O&G emission estimate was due primarily
to its more comprehensive activity factors and inclusion of emissions
from fat-tail sites