84
Thermogenic gas typically forms deep underground, and its presence in air can
be an indicator of fugitive emissions from O&G operations. If ethane is found with
methane, this can be a good indicator that the gas originated from O&G operations,
because ethane does not have any natural atmospheric sources (Pekney et al.
2014). Along with thermogenic gas, “abiotic” methane gas can be created deep in
the Earth’s crust through inorganic mineral reactions with water during a recrystallization process called “serpentinization” (Bradley and Summons 2010; Andreani
and Ménez 2019). Tracking down fugitive emissions of natural gas is complicated
and full of caveats.
One clear link between air pollution and fracking is a significant increase in VOC
and NOx emissions measured at the national level between 2005 and 2015, which
coincides with the development of shale gas and tight oil resources in the United
States (Allen 2016). The onset of the shale boom resulted in many active drill rigs,
more hydraulic fracturing operations, and new pipeline construction, gas plants,
compressor stations, etc. Nationwide impacts from the sheer volume of all this
infrastructure expansion are reflected in the air quality data.
VOC and NOx emissions into the atmosphere from O&G development come
from two main sources: poorly functioning or malfunctioning equipment, and certain operational practices such as venting tanks or storing VOC-bearing produced
water in open impoundments. Some of the VOC compounds, especially formaldehyde and benzene, may cause cancer or other adverse health effects and have been
categorized as hazardous air pollutants by the U.S. EPA. It can be challenging to
define the timing and duration of these pollution sources, especially on large shale
plays where there may be many operators involved.
Sources of air pollution include organic gases and VOCs from the produced
water, petroleum, and natural gas, VOCs and PM from the drilling and completion
fluids, and NOx and PM from diesel and natural gas-fired internal combustion
engines on the pad (Zielinska et al. 2014). Secondary ozone and PM pollution can
be created by reactions among the organic gases and NOx (Nsanzineza et al. 2019).
The sulfur content in diesel fuel or the produced O&G may result in sulfur dioxide
(SO 2 ) or hydrogen sulfide (H 2 S) emissions. NOx, SO 2 , and PM can present both
acute and chronic health risks, and as such are regulated by the U.S. EPA (Cohen
et al. 2017). The five states with the highest health risks from these compounds
based on population size and proximity to O&G operations are Texas, Pennsylvania,
Illinois, California, and Oklahoma (Buonocore et al. 2019).
Emissions vary with the types of operations being performed at the well site.
Even some time-limited activities, such as liquid off-loading, product transfer, and
tank inspections can still result in significant emissions. One study found that liquid
unloading events, which last only minutes, can produce methane emissions equivalent to those from a thousand routinely operating wells (Allen et al. 2015). Storagerelated emissions resulting from product transfer and tank inspection may also
contribute significantly to VOCs (Pétron et al. 2014). Even intermittent operations
like flaring can be an important source of VOCs, NOx, and other hazardous air pollutants (Franklin et al. 2019). The introduction of new technologies and changes in
operational practices may affect the magnitude of emissions over time.
5 Fracking and Air Quality
Thermogenic gas typically forms deep underground, and its presence in air can
be an indicator of fugitive emissions from O&G operations. If ethane is found with
methane, this can be a good indicator that the gas originated from O&G operations,
because ethane does not have any natural atmospheric sources (Pekney et al.
2014). Along with thermogenic gas, “abiotic” methane gas can be created deep in
the Earth’s crust through inorganic mineral reactions with water during a recrystallization process called “serpentinization” (Bradley and Summons 2010; Andreani
and Ménez 2019). Tracking down fugitive emissions of natural gas is complicated
and full of caveats.
One clear link between air pollution and fracking is a significant increase in VOC
and NOx emissions measured at the national level between 2005 and 2015, which
coincides with the development of shale gas and tight oil resources in the United
States (Allen 2016). The onset of the shale boom resulted in many active drill rigs,
more hydraulic fracturing operations, and new pipeline construction, gas plants,
compressor stations, etc. Nationwide impacts from the sheer volume of all this
infrastructure expansion are reflected in the air quality data.
VOC and NOx emissions into the atmosphere from O&G development come
from two main sources: poorly functioning or malfunctioning equipment, and certain operational practices such as venting tanks or storing VOC-bearing produced
water in open impoundments. Some of the VOC compounds, especially formaldehyde and benzene, may cause cancer or other adverse health effects and have been
categorized as hazardous air pollutants by the U.S. EPA. It can be challenging to
define the timing and duration of these pollution sources, especially on large shale
plays where there may be many operators involved.
Sources of air pollution include organic gases and VOCs from the produced
water, petroleum, and natural gas, VOCs and PM from the drilling and completion
fluids, and NOx and PM from diesel and natural gas-fired internal combustion
engines on the pad (Zielinska et al. 2014). Secondary ozone and PM pollution can
be created by reactions among the organic gases and NOx (Nsanzineza et al. 2019).
The sulfur content in diesel fuel or the produced O&G may result in sulfur dioxide
(SO 2 ) or hydrogen sulfide (H 2 S) emissions. NOx, SO 2 , and PM can present both
acute and chronic health risks, and as such are regulated by the U.S. EPA (Cohen
et al. 2017). The five states with the highest health risks from these compounds
based on population size and proximity to O&G operations are Texas, Pennsylvania,
Illinois, California, and Oklahoma (Buonocore et al. 2019).
Emissions vary with the types of operations being performed at the well site.
Even some time-limited activities, such as liquid off-loading, product transfer, and
tank inspections can still result in significant emissions. One study found that liquid
unloading events, which last only minutes, can produce methane emissions equivalent to those from a thousand routinely operating wells (Allen et al. 2015). Storagerelated emissions resulting from product transfer and tank inspection may also
contribute significantly to VOCs (Pétron et al. 2014). Even intermittent operations
like flaring can be an important source of VOCs, NOx, and other hazardous air pollutants (Franklin et al. 2019). The introduction of new technologies and changes in
operational practices may affect the magnitude of emissions over time.
5 Fracking and Air Quality