86
the region is relatively straightforward and simple. However, other shale resources
are located in areas that have existing, conventional O&G development, or near
major cities like Dallas-Ft. Worth, Denver, or Pittsburgh. Defining the potential contribution of shale gas production to air pollution in the presence of all the other
emission sources in these areas can be challenging (Pekney et al. 2018).
Many of the air contaminants linked to drilling and fracking, such as NOx,
VOCs, DPM and others can also be sourced from automobiles, trucks, gasoline stations, and industrial processes. Only in cases where oil and gas development are
especially intense, such as the Permian Basin in the Texas-New Mexico border
region are emissions clearly related to hydrocarbon production. Satellite observations have in fact detected a “cloud” of NO 2 , a surrogate for NOx, over the
Permian Basin.
Methane emissions in particular can have both natural and anthropogenic sources
that are difficult to separate. A study in the St. Lawrence River valley in Quebec
near some Utica Shale production sites found four sources of methane in air (Pinti
et al. 2016). These include the degassing of groundwater during processing for
domestic or municipal uses, natural groundwater discharge along rivers, methane
migration by seepage directly to the surface, and the degassing of recovered hydraulic fracturing fluids during flowback. Telling these sources apart can be quite
challenging.
Several investigations sought to compare the concentrations of criteria air pollutants in areas with significant shale gas and tight oil production against existing data
from the same location prior to development (e.g. Vinciguerra et al. 2015; Maskrey
et al. 2016; Williams et al. 2018). This approach assumes that the background
sources have remained constant over time, and any present-day spike in pollutants
is due solely to shale development activities. This is not always the case, and
accounting for the presence of other sources that could affect regional air quality is
a major challenge (HEI 2019).
When historical data are not available, another strategy that can be used is to
compare air pollution levels from a shale development area with a similar, reference
location that does not have shale development (e.g. Rich and Orimoloye 2016;
Garcia-Gonzales et al. 2019). This approach assumes the background sources in the
reference location are essentially identical to those in the shale development area,
which again may not always be the case. Care must be taken to separate out the
shale-related pollution sources from everything else.
Air emissions from shale gas and tight oil development operations are complex,
sporadic, and variable in terms of both concentration and composition. Every step
of conventional and unconventional hydrocarbon development produces some
degree of air emissions, which can originate from activities either on or off the well
pad (Zielinska et al. 2014; Vaughn et al. 2018). Intermittent wellsite operations like
pumping a hydraulic fracture treatment or temporarily throttling up a generator to
drill through a difficult interval can create brief, high emissions (refer back to the
photograph of a frack in progress in Fig. 2.1). These occur against a background of
many hours of low emissions when equipment is slow or idle.
5 Fracking and Air Quality
the region is relatively straightforward and simple. However, other shale resources
are located in areas that have existing, conventional O&G development, or near
major cities like Dallas-Ft. Worth, Denver, or Pittsburgh. Defining the potential contribution of shale gas production to air pollution in the presence of all the other
emission sources in these areas can be challenging (Pekney et al. 2018).
Many of the air contaminants linked to drilling and fracking, such as NOx,
VOCs, DPM and others can also be sourced from automobiles, trucks, gasoline stations, and industrial processes. Only in cases where oil and gas development are
especially intense, such as the Permian Basin in the Texas-New Mexico border
region are emissions clearly related to hydrocarbon production. Satellite observations have in fact detected a “cloud” of NO 2 , a surrogate for NOx, over the
Permian Basin.
Methane emissions in particular can have both natural and anthropogenic sources
that are difficult to separate. A study in the St. Lawrence River valley in Quebec
near some Utica Shale production sites found four sources of methane in air (Pinti
et al. 2016). These include the degassing of groundwater during processing for
domestic or municipal uses, natural groundwater discharge along rivers, methane
migration by seepage directly to the surface, and the degassing of recovered hydraulic fracturing fluids during flowback. Telling these sources apart can be quite
challenging.
Several investigations sought to compare the concentrations of criteria air pollutants in areas with significant shale gas and tight oil production against existing data
from the same location prior to development (e.g. Vinciguerra et al. 2015; Maskrey
et al. 2016; Williams et al. 2018). This approach assumes that the background
sources have remained constant over time, and any present-day spike in pollutants
is due solely to shale development activities. This is not always the case, and
accounting for the presence of other sources that could affect regional air quality is
a major challenge (HEI 2019).
When historical data are not available, another strategy that can be used is to
compare air pollution levels from a shale development area with a similar, reference
location that does not have shale development (e.g. Rich and Orimoloye 2016;
Garcia-Gonzales et al. 2019). This approach assumes the background sources in the
reference location are essentially identical to those in the shale development area,
which again may not always be the case. Care must be taken to separate out the
shale-related pollution sources from everything else.
Air emissions from shale gas and tight oil development operations are complex,
sporadic, and variable in terms of both concentration and composition. Every step
of conventional and unconventional hydrocarbon development produces some
degree of air emissions, which can originate from activities either on or off the well
pad (Zielinska et al. 2014; Vaughn et al. 2018). Intermittent wellsite operations like
pumping a hydraulic fracture treatment or temporarily throttling up a generator to
drill through a difficult interval can create brief, high emissions (refer back to the
photograph of a frack in progress in Fig. 2.1). These occur against a background of
many hours of low emissions when equipment is slow or idle.
5 Fracking and Air Quality