114
A surface disposal process for produced water that is commonly used in the arid
west is to allow it to evaporate from an open tank. This requires a bit of patience, but
once all the liquid is gone, the remaining minerals can be disposed of as solid waste.
Evaporation is not an option in the humid east, and other disposal methods must be
employed.
In early 2011, the Secretary of the Pennsylvania Department of Environmental
Protection (PADEP) appealed to Marcellus Shale operators to stop using POTWs to
dispose of produced water (Soeder 2017). Operators in Pennsylvania voluntarily
complied, and bromide levels in the Monongahela River dropped soon afterward
(Wilson and VanBriesen 2012). The PADEP recommended that TDS be removed
from produced water prior to disposal by flash distillation or membrane filtration at
the CWT facilities used by heavy industry or disposed down Class II-D UIC wells,
designated for oilfield waste. Operators in West Virginia followed, although careless
handling of the hypersaline produced water has also led to environmental issues.
Along with the produced water pipeline break described previously that contaminated a North Dakota creek (Cozzarelli et al. 2017), USGS researchers have found
that surface spills of high TDS fluids around disposal wells in West Virginia have
led to the contamination of nearby streams (Akob et al. 2016).
The injection of residual wastewater into the deep subsurface occasionally results
in induced earthquakes, discussed in more detail in the next chapter. There were few
existing UIC wells in Pennsylvania for Marcellus produced water, requiring the
wastewater to be hauled to Ohio or West Virginia for injection. The new requirements for disposing of Marcellus produced water through CWT facilities or down
UIC wells resulted in a fivefold increase in the cost of residual wastewater disposal
(Rodriguez and Soeder 2015).
In the Appalachian Basin, the shale gas industry understood that only a relatively
small percentage of injected frack water is returned as flowback. A lot of the water
they were putting into the ground for hydraulic fracturing remained downhole and
therefore was not part of the disposal cost. Industry soon realized that if the flowback and produced water that did return to the surface could be recycled into the
next frack, most of that would remain in the ground as well. Recycling the produced
water into subsequent fracks proved to be a cost-effective, de facto method of disposal. As an added bonus, the recycling practice greatly reduced the volume of
residual wastewater that ultimately had to be handled by UIC wells or CWT
facilities.
Once the recycling process became established, nearly 90% of the relatively
fresh flowback water was recycled into additional fracks. The higher saline produced water from later in production was also recycled, but the high levels of TDS
interfered with the properties of the ionic surfactants and friction reducers. More
freshwater was required to dilute the salinity down to acceptable levels (Maloney
and Yoxtheimer 2012).
Everything has consequences, and the recycling process for frack water resulted
in the development of biocide-resistant microbes (Vikram et al. 2014). Biocides are
used to control the growth of bacteria that are introduced downhole with the frack
fluids. A particular variety of microbes known as “sulfate reducers” may metabolize
6 Fracking and Water
A surface disposal process for produced water that is commonly used in the arid
west is to allow it to evaporate from an open tank. This requires a bit of patience, but
once all the liquid is gone, the remaining minerals can be disposed of as solid waste.
Evaporation is not an option in the humid east, and other disposal methods must be
employed.
In early 2011, the Secretary of the Pennsylvania Department of Environmental
Protection (PADEP) appealed to Marcellus Shale operators to stop using POTWs to
dispose of produced water (Soeder 2017). Operators in Pennsylvania voluntarily
complied, and bromide levels in the Monongahela River dropped soon afterward
(Wilson and VanBriesen 2012). The PADEP recommended that TDS be removed
from produced water prior to disposal by flash distillation or membrane filtration at
the CWT facilities used by heavy industry or disposed down Class II-D UIC wells,
designated for oilfield waste. Operators in West Virginia followed, although careless
handling of the hypersaline produced water has also led to environmental issues.
Along with the produced water pipeline break described previously that contaminated a North Dakota creek (Cozzarelli et al. 2017), USGS researchers have found
that surface spills of high TDS fluids around disposal wells in West Virginia have
led to the contamination of nearby streams (Akob et al. 2016).
The injection of residual wastewater into the deep subsurface occasionally results
in induced earthquakes, discussed in more detail in the next chapter. There were few
existing UIC wells in Pennsylvania for Marcellus produced water, requiring the
wastewater to be hauled to Ohio or West Virginia for injection. The new requirements for disposing of Marcellus produced water through CWT facilities or down
UIC wells resulted in a fivefold increase in the cost of residual wastewater disposal
(Rodriguez and Soeder 2015).
In the Appalachian Basin, the shale gas industry understood that only a relatively
small percentage of injected frack water is returned as flowback. A lot of the water
they were putting into the ground for hydraulic fracturing remained downhole and
therefore was not part of the disposal cost. Industry soon realized that if the flowback and produced water that did return to the surface could be recycled into the
next frack, most of that would remain in the ground as well. Recycling the produced
water into subsequent fracks proved to be a cost-effective, de facto method of disposal. As an added bonus, the recycling practice greatly reduced the volume of
residual wastewater that ultimately had to be handled by UIC wells or CWT
facilities.
Once the recycling process became established, nearly 90% of the relatively
fresh flowback water was recycled into additional fracks. The higher saline produced water from later in production was also recycled, but the high levels of TDS
interfered with the properties of the ionic surfactants and friction reducers. More
freshwater was required to dilute the salinity down to acceptable levels (Maloney
and Yoxtheimer 2012).
Everything has consequences, and the recycling process for frack water resulted
in the development of biocide-resistant microbes (Vikram et al. 2014). Biocides are
used to control the growth of bacteria that are introduced downhole with the frack
fluids. A particular variety of microbes known as “sulfate reducers” may metabolize
6 Fracking and Water